Governing

There are two principal types of governor regardless of fuel type or number of cycles. Engines are either Hit-and-Miss or Throttle-Governed. Often the exact same engine was available as either governing method at the preference of the buyer with all other parts the same.

There are enourmous differences in opinion on this subject and one of those differings of opinion led to one of the best and most heated debates on the Stationary Engine Mailing list in years in February 2002. Fortunately, the debate came to a successful conclusion and all list members benifited in learing a little more about governing. One of the interesting things which came out of the discussion is that many members have engines of one type or the other and not both. While they thought they knew how the other camp worked, they found that they actually did not!

Interestingly, the governor has made a comeback in recent times on car engines, in a modern engine the computer stops over-speeding by turning off the fuel injectors and spark - the same principal as throttle governing.

Hit and Miss

Throttle Governed

The difference between the two methods

Under load both engines behave similarly that they both draw in a charge of fuel/air when they need to. Again there is a significant differnce in that the H&M engine can only draw in a full charge of fuel/air and because of this has around a 20% speed variance under load. The T/G engine only draws in as much fuel/air charge as is required to keep the engine at constant speed.

From Rathbun: Gas Engine Troubles and Installation 1919

Hit and Miss Governing: The governor is of the "Hit and Miss" type, that is, the speed of the engine is held constant by missing more or less explosions on light loads, and increasing the number of explosions as the load increases, the quantity and quality of each charge remaining constant. A hit and miss governor allows only enough charges to be fired to keep the speed constant. When a portion of the load falls off and the engine tends to increase in speed the governor cuts out the next explosion by holding the exhaust valve closed and the inlet closed; this prevents a fresh charge from being drawn into the cylinder. Should the load increase the governor releases the valve gear, and allows a succession of charges to be fired until the speed is up to the required limit. Hit and Miss governing is very economical of fuel as only full charges of the most perfect mixture are fired, but does not hold the speed as constant as the throttling type in which a charge is fired at every other revolution, regardless of load."

Note the diagram is from The Little and Ives Complete Book of Science Illustrated 1943.

Throttle Governor: Unlike the hit and miss system, the throttle governed engfine takes an explosion regularly every other revolution, the speed being held constant on varying loads by either regulating the quantity of mixture admitted to the cylinder or by varying the quality or richness. Throttle governing admits of very close governing or speed regulation, as the impulses are more constant and not so violent as with the hit and miss system. The governor acts directly on the throttle valve and at no time is the operating mechanism disengaged from the driving cam. The throttle governor is particularly well adapted for driving dynamos, supplying electric light, as the uniform speed give a smooth steady llight without the objectionable flickering so likely with the hit and miss engine. To obtain the best fuel economy with a throttling engine it should be run close to its rated capacity, as the poor and imperfect mixture admitted at light loads considerably increases the fuel consumption.

The conjecture

The Stover KA Instructions

The engine is kept at its rated speed by means of the governor. As the speed increases the governor balls move out, which forces in the governor spindle plunger against the throttle shoe which is in turn attached to the throttle lever. (See cut of governor.) The throttle lever working through the throttle rod opens and closes the throttle valve, and thus regulates the speed of the engine. The position of the throttle valve, as shown in the cut is with the throttle valve open and the governor balls together. The throttle valve should work on equal sides of the center line as shown. Set throttle shoe 1/16 inch from end of plunger.

The action of the governor on the hit and miss engine is similar to that used on the throttle governing engine. The governor spindle plunger works against the detent lever on which the detent blade is attached. The action of the governor weights forces the governor spindle out and against the detent lever, which in turn engages the detent blade with the detent catch block on the side rod. When the detent blade and the catch block are engaged, the exhaust valve is held open causing the engine to cut out, and run idle, until the speed has been reduced to such a point, that the engine needs another explosion, at which time the action of the governor weights releases the plunger pin, and permits the engine to take another explosion.

In testing, the detent is carefully adjusted. As the blade and catch block are of tool steel upon which the wear is very slight, they should need no adjustment for some time. There is, however, a natural wear on all working parts, therefore, after the engine has been in operation for a long time. the detent blade or catch block may need replacement. Irregular explosions, and the engine running erratically, are indications of a worn detent blade or catch block. This is caused by the detent blade slipping off the catch block. Either the detent blade or catch block can be very easily replaced.

Joe Prindle's other Governing Methods

Joe Prindle joe_prindle2001@yahoo.com:

With all this talk of weird hit and miss systems, how did they work on the vertical Stickney? Artie Wegner had one fifteen years ago and I thought I had it all figgered out but now all I can recall is that they had an extra valve or two on them, something to do with preventing it from forming a vacuum needed to slurp the intake valve open or something like that?

I am not familiar with the slide valve Ottos, but the later ones like I have had governed by deciding whether or not the gas valve opened. It was hit and miss, all or nothing on the gas valve. The vertical flyball governor moves a roller onto or off of the gas valve cam on the sideshaft. A unigue feature of the Otto is that the governor has no springs. THe top of the governor is a conical weight that can be removed and replaced while the engine is running. TO change the speed of the engine, use a different sized top, weighing more or less. To make it real slow, for show, put a ball bearing under the weight so that it rides on the spindle but does not bear against the flyballs. Engines like the springfield and White and Middleton have simular means of cutting off the gas to control speed. THey compress on every compression cycle but there is no gas, so they don't fire. All of this wasted compression strokes is inefficient and the hit and miss engines that lock the exhaust valve open are more efficient. Other engines that did this were the S M Jones engines, the pendulum governor decides whether or not the gas valve is opened. Oil field engines such as most half breeds are qualitative governed. Many of them use a steam engine governor to throttle the gas going to the inlet, making the mixture progressively leaner as speed increases towards or past the set point.

The exception to the above statement that comes to mind is the Bessemer with the lolipop governor, a true hit and miss, covering an internal port and cutting off the air and fuel mixture when the engine is in an overspeed condition. Some gearless four cycle engines, like the McVickers Automatic, have a port that allows combustion pressure to operate some linkage to cause the push rod to open the exhaust valve. If they don't fire, there is not exhaust stroke and there is no new intake stroke. THese engines control speed by cutting off the spark, and then go through a series of strokes where they compress and de-compress a the same fuel charge a number of times. When the speed drops, the spark is no longer cut off and they hit on the charge of fuel that had been sloshing around in there (washing the cylinder clean and wearing it prematurely) and the pressure operates the linkage, much like a gas operated semi-automatic rifle works. My buddy has a Lambert gearless that works like that and another buddy has a McVickers, The gearless olds is different, but I am not that familiar with them.

The Detroit two cycle vertical uses compressed air in the crankcase to push the fuel into the cylinder with a sort of mixer that they called an injector. It is a bit different than the sort of injector we think of today, but works well and must be seen to be appreciated. They control speed by throttling the air going into the crankcase. I haven't messed with a detroit in years, but I seem to recall that they can be made to idle without missing if you put a petcock in the bottom of the crankcase and run the engine with the valve partway open to bleed off some of the compressed air in the crankcase and make for a lighter mixture because of it. Just a little rambling, sorta got carried away....

The principal messages in cronological order from the list members

The whole thread started when George Best gsb@plaza.ds.adp.com stated:

One thing you need to keep in mind if you belt your show engine up to some device, is whether you have a constant or variable load on the engine. If you have a constant load, your hit&miss engine is going to be hitting all the time same as a throttle governed engine. In other words your hit&miss engine that coasts for long periods between firing, will not be coasting anymore.

It's my understanding that IF a Hit and Miss engine hits "all the time" it will damage the engine. I'm NOT talking about 10seconds (or so, when power is needed) but rather continuing to hit "all the time." If it hits "all the time" What you need is a bigger engine!

I have heard this before and have never seen any documentation to tell me why. In other words it takes a larger hit and miss engine to perform the same work as a throttle governed one? I haven't run my Alamo under load for more than an hour or so at a time, but when running like this it hasn't seemed to hurt anything.

Is there a formula for sizing a hit and miss engine to a certain job? In other words if my cane mill requires 6 to 8 horsepower to run, what size hit and miss engine should it require? I know that there is a different horsepower rating for steam engines than gas engines for the same job in some of my catalogs, but no mention of types of governors.

I guess I don't understand what you can damage if the bearings, timing valves, etc, are all the same,............. or are they?

Take care.

It's not good for lots of throttle governed engines to run at full power continuously, either. I notice the Wisconsin manuals advise not loading them at over 80% of rated horsepower. (Even with the optional Stellite-faced exhaust valves, seat inserts and valve rotators.) A hit and miss always "hits" at full power, so if it's hitting continuously it's wide open.

The first thing to suffer in an overloaded engine is likely to be the exhaust valve. Different materials for valve heads and seats, different designs of valve stems and guides, cooling around them, exhaust gas temperature, free oxygen in the exhaust gas, dwell time of the valve off the seat, exhaust backpressure, contact of the valve face with the seat when closed, perhaps the barometric pressure and phase of the moon can all influence how long a valve can last. Exhaust valves in gasoline engines running hard can glow cherry red and draw their heads out into a tulip shape as they bump into the seat on closing. That's where the idea to make some exhaust valves in that shape to start with came from. Our engines don't run at the high power densities of things like supercharged aircraft engines, but I'll bet something like my 3 HP IHC M with its uncooled "hot" head can get the valve temperature right up there under full power! Or a similar hit and miss hitting all the time. I know my M can blow some pretty fire out the exhaust.

speaking of which, i have been having problems with my "M" Siezing up. It would actually heat up and start seizing up enough to actually shut itself off. Then i would wait about a half hour and be able to start it again. I always keep lots of water in it, and LOTS of oil. Infact when it seized up the first time it emptied an entire oiler. I dont run it really loaded, just a gear reducer and a butter churn. Maybe its time for a rebuild??? It feels like the piston is swelling since the cylinder wont shrink when heated. Any ideas what happened??

Maybe not enough oil, maybe too tight piston-cylinder clearance, maybe too tight ring gaps? If you're using lots of oil, maybe it's varnishing up the sides of the piston enough to make it tight? Extra heavy grades of oil would be more likely to do this. Wouldn't expect it to stop a running engine, though. More likely to get tight after running hot and then sitting a while. Could the oil hole in the piston be clogged up so the wrist pin bearing's not getting oil? (I don't know if that could seize or not, usually they get loose and knock.) Sure you're getting adequate grease to the main and rod bearings? Sounds like time to pull it down for a look-see.

A friend of mine had a similar experience. He was running a 5 hp FBM Z at rated speed. The water hopper was boiling nicely. He was feeding 90 wt. gear oil in the cylinder oiler. Engine seized right up. He pulled the head and with a liberial application of "weasel piss" was able to get it "unstuck" and the piston removed. The piston and rings had a very gummy / varnished look to them. He spent about a half hour cleaning the piston, rings, and bore. Cleaned the 90 wt. out of the oiler and replaced it with plain vanilla 30 wt. oil. The engine ran perfectly the rest of the rally.

If I were you, I'd pull the piston and give it a good cleaning. Then check what sort of oil you're using and set the drip rate at a drop or two per horsepower per minute. I think you'll solve your problem.

It would seem to me that for a hit and miss engine to fire every second revolution would be much the same as running a throttle governed engine with the throttle wide open. In both situations I am assuming the load will keep the rpm at the governed limit, say, 600 rpm. Not many engines like being run flat out wide open for long. I doubt that any manufacturer of these old engines intended them to be loaded that heavily, but expected they could put out their rated horsepower with less than full throttle, or, not hitting at every opportunity. To run an engine at full output means that if the load increases a little, the engine will be reduced in speed, and, probably reduce output and may even die under load. The effects of excessive heat on the exhaust valve may also, as has been mentioned, lead to premature wear. The only automobile engine I have had that could be run at full throttle without harm was a Volkswagen beetle. In that engine, the intake system was undersized as compared with the bore and stoke and so the horsepower output of the engine was modest compared to its displacement. Consequently, it could be run "wide open" without harm. Naturally, some folks modified the intake systems and achieved considerable horsepower increase. Judson, an old name in engines, made a very nice supercharger that bolted on the 36 HP engine and made a BIG difference in acceleration, and a modest benefit in top speed. But, I digress.

Why do they put a rated speed on a hit and miss engine if it can harm it to run that speed?

You are forgetting that the governed limit can be reduced by quite a bit, at least on the three that I have. I can set my Alamo which is rated at 360 RPM, to latch out at probably half that speed. Of course it isn't producing 7 horsepower at that speed either. So there is no way I am running this engine wide open. I sure don't think I have harmed it by running my cane mill or the grist mill, both of which I run under full load a lot of the time.

Also, most of those old farmers didn't know anything about these infernal combustion engines, and there is nothing in any of the manuals I have that say not to run them under load.

The rated speed is the number of revolutions per minute. It doesn't harm it to run at that speed. But, if the load is increased to the point the engine is firing at every opportunity in order to maintain the rated speed, you are getting maximum output from the engine, and the increased heat load may bring about early failure.

I've seen discussions of this in some of my early engine books but can't seem to find it quick when I wanted to quote it. The thinking is that a hit and miss engine that is under too much load to miss never reaches its rated operating speed and is under constant lugging. With a throttle gov engine you would almost need a tach to see if it is running at rated speed or watch to see if the throttle ever fluctuates. It wouldn't kill the engine in short order but would be overworked.

The only reference to favoring a throttle governed engine over a hit and miss in my old books is in applications that require a constant speed. There is no mention of avoiding running a hit and miss engine under a constant load. These are books published in 1910 and 1912. Dykes also mentions the same reasons in his short treatise in my 14th edition (1925). The reproduction "directions for setting up and operating the" IHC engines booklets I have all say basically the same thing, and none of them mention anything about operating speeds.

It may be running at a constant speed but it is being load governed as opposed to mechanical governed. I finally found a reference to what I was trying to explain. It is in an International Correspondence school book with a copyright date of 1907. It is in section 23 titled "Care and Management of Stationary Engines. I quote section 2 below:

In determining the size of an engine for a given amount of work, it should be borne in mind that an engine that is called upon to run at its full capacity during the greater part of the time is actually overtaxed. Working an engine to this extent will result in rapid wearing of the piston and cylinder and consequent loss of power and economy due to leakage. When doing the maximum amount of work possible in a plant, the engine, if governed by the regulation of the number of impulses, should cut off at least once in 4 or 5 charging strokes. This will benefit the cylinder through the admission of charges of cool air at more or less regular intervals.

I found this in my 1912 IHC engine operators guide. The "Make-and-Break" type is used almost entirely for engines running below 500 RPM. ---The governor is designed to hold the speed of an engine uniform. In either regulates the amount of mix- ture for each charge-as in the case of the throttling governor-or it acts so as to permit an impulse only when power is required, as in the case of the "Hit-and-Miss" type governor. Am I right when I say: for a constant speed you need a throttle governed engine and the amount of "Hits" of a "Hit-and-Miss" engine depends on the horse power needed at that moment?

That's in line with Wisconsin's (throttle governed) recommendation of not exceeding 80% of rated power continuously. Many engine makers just rated their engines at less horsepower than they were actually capable of producing.

I have seen this also. However, if the H&M engine is hitting every time, would it not be running at a constant speed?

In the case of a generator, it might not run at a constant speed if there is no constant current draw. I don't run any generators, but it is my understanding that if there is a current draw, the load on the engine is higher. Thus a hit and miss might back off once in awhile in this application and then when something is loaded on it, it really isn't producing the proper current until it gets back to speed. I'm sure our folks with the light plants can fill us in on this subject.

Faulty logic, Dave. The failure of the governor to latch up under a heavy load is an indication that the load is so great that the engine is unable to overcome it and attain the speed set point. The speed will not likely be constant, as the demand for power increases, the speed of the engine will droop and the pressures inside the cylinder will increase until the amount of pressure required to force the piston down the bore is greater than the amount of pressure created by combustion, at which point the engine stalls. The bearings and cylinder will heat up unless the lubricators are opened up to increase the flow to carry away the extra heat generated. Just my observations, based on a lot of tinkering and working with these engines. Take it for what it is worth to you.

Well Joe, I knew that if I kept my mouth shut long enough, someone would make Dave's argument for him.

> Faulty logic, Dave.
> The failure of the governor to latch up under a heavy load is an indication that the load is so
> great that the engine is unable to overcome it and attain the speed set point. The speed will not
> likely be constant, as the demand for power increases, the speed of the engine will droop and the
> pressures inside the cylinder will increase until the amount of pressure required to force the
> piston down the bore is greater than the amount of pressure created by combustion, at which point
> the engine stalls. The bearings and cylinder will heat up unless the lubricators are opened up to
> increase the flow to carry away the extra heat generated.

You did it very clearly, but I think your were looking at it from different direction.

George started out talking about a Hit and Miss engine that was "under load" and hitting on every power stroke, IE. the governor was not engaging.

----- Original Message -----
From: "George Best"

> One thing you need to keep in mind if you belt your show engine up to some
> device, is whether you have a constant or variable load on the engine. If
> you have a constant load, your hit&miss engine is going to be hitting all
> the time same as a throttle governed engine. In other words your hit&miss
> engine that coasts for long periods between firing, will not be coasting
> anymore.

Dave said that if you had a Hit and Miss engine under such a load as to cause it to hit on every power stroke, YOU NEED A BIGGER ENGINE !!!!!

From: "Dave Rotigel"

> Hi George,
> It's my understanding that IF a Hit and Miss engine hits "all the
> time" it will damage the engine. I'm NOT talking about 10seconds (or so,
> when power is needed) but rather continuing to hit "all the time." If it
> hits "all the time" What you need is a bigger engine!
> Dave

Dave was not saying that Hit and Miss engines would not do the work they were rated for or that running them at their rated RPM and work load would cause damage.

He was simply and correctly saying that any Hit and Miss engine that is pulling a load that does not allow the Governor to function, is an engine that is being asked to work above and beyond it's designed rating and will soon suffer from such use.

Thanks for your input. I would think that you have cleared things up very nicely. More importantly, thanks for reading what I wrote, understanding what words mean, and for NOT putting any additional words into my keyboard--all things that some others on the List apparently can't seem to do!

Another question along these lines:

What about engines where the horsepower was raised by the manufacturors simply by setting the governed speed higher?

With such an engine, would running it on the previously rated max load probably cause damage? In other words, it seems there must have been a little "wiggle room" (don't touch that Arnie) in their specs to CYA.

To summarise then so as to make sure I've read ALL the words correctly. Whatever the governing system it is a bad idea to constantly run an engine above75-80% of max power for several reasons: - you are operating on the droop of the efficency curve and so below peak fuel efficiency - The engine will be running hot and also probably near the extremes of lubrication. Also perhaps worth noting that most H&M predate NiMoNiC steels and valve warping was common. -Its noisy (and in preservation mostly unecessary) I'd add that a H&M governer is not the most precise governing system (cyclic variation in excess of 20%) and would expect it to latch every time some way before max power. Also some manufacturers were very conservative in ratings and their machines could be and were run for long periods at rated power. Ruston and Petter (prewar) being two good (UK) examples.

An engine SHOULD be able to run at its rated horsepower. An engine that cannot be run at full power for an extended period is either poorly designed, or in need of repair.

I don't think anyone would dispute what you say here. The problem is that THAT was NOT the question asked. I urge you to go back and look at the post that started this thread--NOT the posts that (like yours) answer a question (or questions) that were NEVER asked.

I continue to be astounded at how many on the List either can't read, don't know what words mean, respond to a question before they understand what is being asked, or respond to a question that was never asked! (I'll not even get into the "I can't answer your question, but I will say that my father's doves were VERY pretty." or the "Where on earth do you get this CRAP" type of answer here! Some people just like to see their words "in print" and we all just have to live with that.)

Let me try this in a bit different way and see if it makes sense. Set the governor on your H&M engine so that, WITH NO LOAD on it, it is running at the rated speed. Now hook it up to whatever device that you intend it to pull with it and have it under load. Start the engine and see if it latches up on the governor from time to time. (See Doug's post here.) If the engine does not latch up on the governor, get a bigger engine! If you continue to use the smaller engine that does not latch up, you are doing harm to it.

Dave
PS, My guess is that Ken's 7 HP Alamo would meet this "test" and run the way that Doug's post suggests a H&M engine should preform.
PPS, Ken, Don't take this, however, to in ANY WAY suggest that you should not buy a larger engine!.

Not to want to doubt you Dave, after all you are so old and therefore wise, but I cannot see why this is so... there are some brands in which the same engine made of the same castings was available either hit-n-miss or throttle-governed - what did they change in these engines to make them stronger? While I do not know for sure that every part was the same, I'd have to wonder why any engine company in their right mind would want two parts which look the same for the same job, but not actually be the same - would seem to be a stores and QA problem in the making. Might the story have been spread by sales people looking to sell poor dumb farmer Joe a bigger engine when he did not really need one?

>I don't think anyone would dispute what you say here. The problem
>is that THAT was NOT the question asked. I urge you to go back and look at
>the post that started this thread--NOT the posts that (like yours) answer
>a question (or questions) that were NEVER asked.

Hi Dave, Did someone ask, "will running a hit and miss engine under such a load that it fires every time cause damage to the engine?" That was the question that you answered, abeit incorrectly.

It was your fallacious statement (that you tried to qualify with the heresay of some mysterious engineman) to which I took exception.

>you continue to use the smaller engine that does not latch up,
>you are doing harm to it.

Exactly what kind of harm is being done to this engine? Please answer the question as you would expect your students to answer the question. You WILL be graded.

Dave Rotigel rotigel@westol.com responded to Ken's new question:

Many engine manufactures (eg. Hercules, Witte) claimed that their engines were PURPOSEFULLY underrated in HP. Thus, the "upping" in HP by simply increasing the speed by 25/50 RPM's did not hurt the engine in any way. Thus, to run the older engine at 25/50 RPM's faster, or the newer ones at 25/50 RPM's slower would appear NOT to hurt the engine in any way.

>To summarise then so as to make sure I've read ALL the words correctly.
>Whatever the governing system it is a bad idea to constantly run an engine
>above75-80% of max power for several reasons:

Ok, I can't stand it any longer and am compelled to open my mouth (or keyboard). The original premise was that it was harmful to run a hit and miss engine under such a load that it fires every time. Because no one has made any compelling arguments regarding exactly WHAT harm would be done to the engine, I must take the position that it does NO harm to an engine to run it at it's rated horsepower.

Certainly, an engine will endure more wear when run under a heavy load, but this is evident, and would hardly be considered "damaging" by any stretch of the imagination.

>The engine will be running hot and also probably near the extremes of lubrication.

A cylinder and piston on a hot running engine wear considerably less than on a cold running engine. Rate of wear climbs dramatically as temerature decreases. We've all seen the effects a cold running engine has on spark plugs; all that carbon buildup is a indicator of inefficient combustion. Those are TWO good reasons to run an engine HOT.

Lubrication is a non-issue if you set your oilers to the manufacurer's specs.

When the the work to be performed is a given, then the only other option to using a small engine that "hits" every time is using a larger engine. The larger engine will have greater losses due to internal friction, the losses due to the inherent inefficiency of combustion will be greater in the larger engine, thermal losses will be greater, and the larger engine just plain costs more. Economically, it's better to get the correct sized engine to perform a given task.

>Also some manufacturers were very conservative in
>ratings and their machines could be and were run for long periods at rated
>power. Ruston and Petter (prewar) being two good (UK) examples.

An engine SHOULD be able to run at its rated horsepower. An engine that cannot be run at full power for an extended period is either poorly designed, or in need of repair.

Basically true, BUT, is the rated horsepower the true maximum output of the engine? Full power that the engine can develop may well be above the rating at which the manufacturer intended the engine to operate continuously. If you put "full RATED power" into that second statement above, no one can reasonably argue against it.

I rather suspect that most of these old engines will in fact run wide open for a long time without incident, but it was often recommended not to do so.

Surely you're NOT suggesting disabling or doing away with governors are you? You may _suspect_ that this practice would not cause damage, but empirical evidence says otherwise.

Arnie, if you carefully study the governors on most stationary engines, you'll find that when operating normally they only allow the engine to run wide open when they are slowed down by applying a load to them. Quite the opposite of overspeeding. Running them wide open in this way may potentially cause accelerated engine part wear or heat damage, but won't cause catastrophic engine failure (at least if it's not detonating hard as a wide open engine running on kerosene without water might.) There's a nice explanation of how governors work at Bill Dickerson's page if you'd like to learn more: http://ourworld.compuserve.com/homepages/billd1/gov.htm.

Note I've only included the next two messages because in John's response there is an important safety message - I'm not out to embaress John by dragging an episode out again - we've all been in similar situations where we broke the engineers golden rule "if it aint broke dont touch it". Arnie Fero feroa@venus.pgh.wec.com taunted:

Gee, sounds like you have some first-hand experience of engine overspeeding caused by a "malfunction" of the governor?

Well, I knew that's where you were headed. I've previously apologized both privately and publicly to you for jamming the throttle on your Petter M and racing it 2 years ago, and I'll take this opportunity do so again. I never should've messed with someone else's (your) running engine without your supervision and express consent. That was stupid and wrong, and I'm sorry. I'm very thankful that I didn't blow your engine up, and even more thankful that I wasn't responsible for injuring someone. It scared me badly.

In explanation of my actions, not to offer any excuse, I quite mistakenly thought (A) that I was doing something perfectly innocuous and safe, having many times before blipped open the throttle of throttle-governed engines by hand to momentarily hear what the engine would sound like pulling a load, the governor pulling the throttle back closed when the pressure was released (having no idea that that engine did have a dangerous flaw of governor design or execution that allowed the throttle to go over center and jam), and (B) that it belonged to a good friend who wouldn't object if I did so.

When I was unable to pull the throttle lever back down as it began to speed up, I feared that the flywheels might burst, and I was directly in the line of explosion. Yelling bloody murder, I stepped to the side so my trunk and head would be out of the line of flight of fragments, risking my arms (the right one of which had already been through major trauma surgery a few months before, so I knew just what I was risking) as I continued to struggle with the throttle and pulled off the spark plug wire. (It left the terminal on the plug.) The engine kept racing, firing without spark, and I turned around to yell for help at the group under the tent, and several people did run to assist. I had no idea what else to do at that point. I think it was Jim French who obstructed the engine's air intake and shut it down.

I was terribly embarrassed and ashamed, as well as baffled over how such a thing could've happened. I learned several important lessons from that experience, and I certainly won't mess with anyone else's engine or anything of yours, Arnie, ever again!

Perhaps so, but perhaps NOT! The question was concerning a H&M engine "hitting all the time." I've done a little reading (dangerous?) and a little thinking (ALWAYS DANGEROUS!) But try this out.

When a H&M engine "hits" it fires with a FULL charge in the combustion chamber. If it is firing with a full charge "all the time" (and constantly) it is running at MAXIMUM all the time. A T/G engine hitting all the time is NOT necessarily firing with a full charge in the combustion chamber. There would be a full charge each time it fires ONLY if the governor were set to it's MAXIMUM position. Usually this IS NOT the case, and I believe that constant firing in the maximum position would likely damage the engine. (I'd have to do some more research/reading, but I believe that T/G engine instructions would indicate as much.)

If I am correct here, running a H&M engine in such a way as to NOT allow it to lock up on the governor OR to run a T/G engine with the governor set WIDE OPEN (for any extended period of time) would have the same results--either engine can be expected to produce a BANG that is not the kind that we would prefer to hear!

Here's my thoughts. First why would anyone want to run an antique that you are trying to preserve with a heavy load that will wear it out. Second it is probably not a good idea to load any old engine much more than 50% of it's rated horsepower and probably not much more than 80% on brand new engines.

I didn't think I was overworking the engine because I have never boiled the water in it. I use the engine because it is a great way to make use of one of my hobbies to assist in another, (syrupmaking). If you go to any shows with steam engines, you will probably notice that they give them a pretty good workout, and most of those engines are older than our gas engines.

Just my 2 cents worth.

Have you every closely watched T/G engines running? I'm not sure if you have any but please take a look. If the engine is under load near its rated power at less than its rated RPM then it will fire every time with a full charge because the butterfly valve in the intake is held wide open by the governor - if it is not fully loaded then the charge will be reduced and less fuel allowed to enter (ie. your point below). Just out of interest you seem to consider that T/G engines fire every time - they don't unless they are fully loaded, once the engine gets up to speed the governor closes the [butterfly] intake valve and you get no fuel entering the cylinder - thus no firing. It does not start firing again until it slows down enough for the governor to allow entry of fuel. If a T/Greally does fire every time when not under load there is probably something wrong with the governor or fuel system.

It would depend on the load - if it is a constant load then probably, but if it is something which fluctuates like a hay baler then no, the engine will increase speed during the easy bits and bog down during the hard bits.

Hi Paul, JUST NOT TRUE!

I have engines which behave this way, I have to admit to being a bit of a stranger to my own hit-n-miss engines (one of which is with Leroy and the other of which is slowly making its way southwards to my house in Australia thanks to the help of many friend list members) - however, I'm pretty familiar with my T/G engines and they do not fire on a full charge every time. The governor does control the butterfly valve and does completely close it - I could not say if all engines work this way but the seven that I have all do.

And before you point it out, yes I know this has nothing to do with the original question

Hi Dave Sorry mate shouting is not making an argument. Paul's description is spot on. Like you I have shelves of books and I read them. All, including Sir Harry Ricardo, agree with Paul.

Given the level of misunderstanding a GEM article would be useful. However I'd also suggest that, rather than using this increasingly ill-tempered blather, GEM might be better off with a precis of an authoritative piece on the subject. Ricardo or Heldt say?

I must also apologise that we Brits exported sarcasm to the US.

Dykes (and others) also point out that a T/G engine is much easier to run on kerosene. Several books that I looked at indicate that kero can be used in a H∓M only if there is a preheater for the fuel. This is, of course because the cylinder/combustion chamber (in a H∓M) is not hot enough to vaporize the kero unless it's preheated.

PS, I read somewhere (Arnie's literature?) that in the late teens gasoline could cost as much as $0.05 per gallon, but Kerosene cost ONLY $0.03 per gallon!

John Hammink: Am I right when I say: for a constant speed you need a throttle governed engine and the amount of "Hits" of a "Hit-and-Miss" engine depends on the horse power needed at that moment?

Yes, and No. A T/G engine will give a constant speed, a H& M will not. (I'm assuming that both are pulling a device that is w/in their HP range.) A H&M will vary by, perhaps, as much as 20%. On a H&M engine the speed can be controlled somewhat by the setting of the governor. Hercules built engines, for example, have 3 different settings and the Galloway engine has a thumb screw adjustment on the governor that varied the speed. Slower speeds can easily be achieved by installing lighter springs. Once the governor is set to a certain speed on a H&M engine it will keep it to that speed (+/- 20%.) This has NOTHING to do with the HP rating of the engine, unless you have the governor set at the rated speed as indicated in the name plate.

For example, I run my 16 HP Galloway at shows at somewhere around 85 RPM's It's rated at 16 HP at 320 RPM's (I think that's correct, but you get the idea.) Clearly at 85 RPM's it's NOT putting out 16 HP. Now if I were to belt the 16 HP Galloway up to something it would continue to run at 85 RPM's unless I were to change the governor setting (and in this engine's case the springs as well.)

So the number of "hits" per minute DOES NOT depend on the HP needed, but only the number of "hits" needed to keep the engine at the speed at which the governor is set.

the R&V, running with no load, varies from 150rpm to just under 200rpm. Would it be safe to presume that if I put the engine under load there would be less variation in the speed?

I would think that you would get the same variation in speed with the engine under load. The only difference would be that it would not coast as long between hits.

Ron (Maytag) Carroll MaytagTwin@aol.com responded Ken's question:

Suppose you have a 7 horsepower Alamo that is rated at, say 650 rpm and a potential of 7 HP. If you reduce the governed speed to 360 rpm then the horsepower output potential is accordingly reduced. One thing to keep in mind is the horsepower is not being generated by simply maintaining the governed speed. If the engine is not loaded, and is a hit and miss, it will fire, coast a while, then fire again with it trying to maintain the governed speed. In a throttle governed engine the throttle will be closed a bit to keep the speed down to the governed speed. With either kind of engine, running at a lower than maximum rated speed will result in less potential horsepower output. Just for grins sometime you might belt your Alamo up to a little one or two horsepower Briggs and set your Alamo exhaust valve open so that it doesn't get compression. If the one or two horsepower Briggs can turn your Alamo at its rated speed of 650 or so rpm, then you are seeing how little horsepower is needed for overcoming engine friction. I suspect a two horse Briggs would do the job of spinning the engine. If so, and the maker rated the engine at 7 hp, that means the engine is capable of producing a potential 7 hp on the output pulley, overcoming the approximate 2 hp internal friction loss while doing it. Simply put, the engine isn't producing the rated horsepower until you let the clutch out. Then, if the load is equivalent to the rated horsepower, and the engine can maintain the rated rpm, it is.

OK, time for me to add to this discussion. From a standpoint of one who knows VERY little about the flywheel engines, these are my observations.

1. Gas was VERY expensive back in the good old days.
2. A Hit n Miss uses a lot less gas when it is not under load, so it can coast between the loads. IE: Hookin one up to a corn sheller is gonna have a bit of a lull between bags of corn.
3. A throttle governed engine requires constant fuel to keep it running.
4. A Throttle governed engine is gonna keep stuff moving at full speed even though aint nothin bein done.

I would think that for something like a saw mill you would want constant speed, but for something like a corn sheller or mill you would want to use a hit n miss that you can run all day long if need be on less gas.

I have seen how well built these engines are as compared with the engines of today. The farmer would have only had to keep an eye on the oil and grease, which is what the young'ns was fer.

Certainly, an engine will endure more wear when run under a heavy load, but this is evident, and would hardly be considered "damaging" by any stretch of the imagination.

Paul,

You are right on, except technically speaking the spark is firing each time on a throttle governed engine, there is just not enough fuel drawn into the chamber for combustion. And, that is just exactly what the governors on a throttle governed engine are supposed to do: "When the engine does not need additional fuel to maintain its load, the governor and throttle butterfly shuts off fuel to the chamber thus saving fuel just like a hit and miss." I have a couple of throttle engines that actually sound like hit and miss because the butterfly's are a very close fit and completely shut off the fuel when closed.

Ps: I have a number of hit and miss engines that I have been trying to get the "miss out" for years with no success. Guess I need to go back to mechanics school.

Hey Ron, That brings up another question. A Maytag engine (92 at least) is hit and miss governed (although in a slightly different manner), so what happens when one of them is loaded down to the point of firing every time? Not much..but then again, they are 2-stroke engines: much fewer moving parts etc to break down. And the 92 always sucks a full charge of fuel in, so I suppose it is always running at full load (if it is firing every time).

Hi Randall,
Your point is good. I have experimented a little with a Johnson Utilimotor that is a small two-stroke much like the Maytag 92, and I find that if a light load is applied, the firing increases but it still spins a few turns between firing. Then, if a heavier load is applied, it begins to fire every revolution. In both cases the engine is turning slower than when it was firing and coasting many turns between firing. Also, once it begins firing every revolution, it doesn't take much more load to bog it down and bring it to a stop. It appears to me the maximum output occurs just when the engine slows enough to begin firing every revolution. I used the Johnson Utilimotor to experiment with because, unlike the Evil Dave, I respect my Maytag ENGINES too much to subject them to such abuse. And, unlike the KA Rob who would run a Maytag ENGINE without lubrication if possible (I guess to appease the KA EPA?), I run the old standard mix of 16 parts gasoline to one part 30 wt. non-detergent oil. It smokes, but, so do some of my best friends. :>)

The next day Philip Thornton-Evison philipte@clara.co.uk wrote the following article:

I've been following the discussion on rated power of engines with great interest, and have been thinking about what has been said. I promise it won’t happen again [:-)] I found it helpful to imagine a TG and an H&M engine, of the same power, side by side. At idle/no load conditions, the H&M engine will fire only when the speed falls below x rpm, determined by the governor setting. When it fires, it speeds up and the exhaust valve is latched open. At this point the engine is freewheeling, the stored energy in the flywheels being used purely to overcome engine friction, and a small pumping loss,when air is being pumped in and out of the cylinder through the exhaust valve, This also has the effect of cooling the cylinder, and more importantly the valve head. Very useful if its made of a low quality steel which will warp and/or burn if it gets too hot. Also, during this freewheeling period the engine is using NO fuel.

The TG engine will have the throttle butterfly fully, or nearly fully closed under the same no load conditions. It will be drawing a small amount of air into the cylinder, along with an equally small amount of fuel. This will fire on every power stroke to keep the engine running at its governed speed. The closed throttle butterfly will reduce the effective compression ratio, and thus the efficiency of the engine. Now, the big question is which engine will use the least fuel under these conditions.

My experience is that the H&M will be more econmical. Mind you, the average farmer wouldn’t want to burn expensive fuel when the engine wasn’t working, so the H&M would be better suited. The TG engine will be burning fuel constantly, although some makes will run a bit like a hit and miss off load and misfire slightly.

Next step is to consider the engines working under, say, 50% load. The TG would have opened its throttle wider, under the influence of the governor, and be drawing in more air and fuel on each stroke, thus increasing the power developed. THe H&M would be ‘hitting’ more tha it would be ‘missing’, thus it too would be developing increased power to match the load. The speed variation between hits and misses would also be less, i.e the speed would be more constant.

If we increased the load up to 100%, the TG engine would have the throttle held wide open and be drawing in as much air and fuel as it could to keep the rpm up to governor speed. The H&M would be hitting at very stroke, again burning the maximum amount of fuel it could and developing maximum power. Increase the load above this, and despite both engines running flat out, the speed would start to drop as they would not be able to respond to the load, the governor can’t open any more than fully open. The only way to get more power from these engines would be to increase the rpm, i.e draw in more air and fuel. This will increase the amount of heat to be dissipated, and may be too much for the cooling system to cope with, not to mention the poor old exhaust valve, glowing cherry red......

For practical reasons of economy and longevity therefore, running an engine at full throttle is not desirable. It's cheaper to get a bigger engine. I have in front of me a textbook, dated 1949, which gives an example of an engine rated at 100 bhp/2500 rpm absolute maximum. If used in a car, the rating would be 80 bhp at 2500 rpm. Sold for use in a truck the rating would fall to 60 hp at 2000 rpm. For use on a pumping set , running several hours a day, the rating would be reduced to 45 hp at 1500rpm, and for continuous duty it would be lower still, probably not more than 35 or 40 hp at 1500 rpm.

In conclusion, a H&M engine is probably better if its duties involve long periods of idle running, as it will use less fuel. Under moderate loads I don’t think there is much to choose between H&M and TG in economy terms except if you need to run something at a constant speed, e.g a centrifugal pump or dynamo. If you hook a dynamo and some lamps up to a H&M the results are nothing short of comical. A bright flash of light as the engine fires, dimming down to a glow before it fires again. The TG on the other hand, will hold its speed far better and the lamp flicker will be barely noticeable. Indeed, larger ( mainly single cylinder) engines often came with a heavier ‘electrical’ flywheel if they were going to be used for generating duties, some had a yet heavier option for driving alternators in parallel.

Finally, we need to consider paraffin engines, or kerosene if you come from across the pond! Kero is heavier and less volatile than petrol, and it won't vaporize at normal temperatures. Consequently, a H&M is not much use for burning kero, as all that cold air pumping in and out of the cylinder reduces the temperature too much. In this instance TG is what is needed, to keep the cylinder hot enough. In fact, a kero engine needs to have the contents of the hopper just ‘on the boil’ if it is to operate efficiently without producing clouds of pungent smoke and fouling the plug. Get the engine too hot though, and kero tends to detonate badly. Hence the water drip seen on some engines. The idea is to introduce enough water to stop the knocking when under load.

Right, now I better put on my flameproof suit, as I fear I may have raised the combustion temperature on the list even more than it has been of late!!

You are all missing the point when you say a throttle governed engine maintains a constant speed. It TRIES to but if you watch/listen/have a rev counter you'll notice that when the load comes on the engine slows down, the throttle opens up to feed more fuel and there is a lag before the engine increases speed. This is due to system inertia.

Similarly, if you take the load off, the engine actually speeds up for a fraction before the closing of the throttle butterfly reduces the fuel intake and causes it to slow back to the regulated speed.

Depending on engine tuning, particularly fuel settings, when a load is applied, the engine may even speed up past the regulated speed before coming back to speed. This is system overshoot.

In addition, depending on the tuning, an unloaded throttle governed engine will often "hunt" back and forth about the nominal regulated speed ie it will go + and - the set RPM. Look at the regulator mechanism and see if it moves slightly back and forth, even though there is no load on the engine. This is system hysteresis.

Sooo, throttled governed engines are not constant speed engines.

and in another message

May I jump in here and answer Patrick's question, because Dave seems to be occupied elsewhere.

A Hit and Miss engine is governed on its minimum speed, not its maximum speed. The maximum speed it attains depends on the load and the amount of energy provided by the fuel each hit.

A load will cause the engine to slow faster than if unloaded.

So with a load on, the engine will slow down more quickly to the speed where the trip actuates. Note: the trip actuates at the same speed each time.

Now the engine fires but because it has a load it will not come up to the unloaded speed.

So a loaded H&M will fire more often than one unloaded and will not come up to unloaded RPM but will not drop below the RPM set by the trip, whether loaded or unloaded.

So Patrick, your engine will run 150 RPM to maybe 170 RPM, loaded, instead of 150 to 195, unloaded.

Essentially you are right here Colin, however I expect that the hysteris would be different between a Hit and Miss and a Throttle Governed. The TG is much better at maintaining its speed within the range of 2% (guesstimate) of its set speed, but the Hit and Miss is probably within the range 20% (another guesstimate, backed up by Rathbun).

When loaded with a constant load the TG is going to maintain its speed much better than the H&M. In both cases, I don't think either engine is going to go much over its rated (note: not the speed we've set the engine to run at, but the maximum speed it was designed to run at) speed as the governor should prevent that happening by cutting off the fuel - no fuel, no explosion, no momentum, no speed increase. Running a H&M and a TG on a light plant should demonstrate this concept for you. On the H&M the lights go (engine fires) bright, dimmer, dimmer, dim, dim, dim, (engine fires) bright, dimmer, dimmer, dim, dim, dim but on the TG they're going to stay fairly bright all the time.

As an example an engine set to run very slowly - when it fires, it is going to run much faster for a while because the energy of the explosion is going to be the same at any speed. For example an engine set to say 500 rpm whose rated maximum is 600 rpm will probably run very close to 500rpm when both coasting and firing. However, the same engine set to run at 50 rpm will not run at 50, but instead will fire and run at whatever speed is imparted by the explosion then gradually coast back down to 50 where it will fire again. I'm not even going to try the physics calculations, but as a layman I'd expect that an engine rated at 650 rpm is going to try and travel that fast when the explosion occurs, the energy has to be transferred to the fly wheels by accellerating them - of course this cannot happen instantly (ie. the fly wheels have to accellerate slowly - they cannot change from 50 rpm to 500 rpm instantly) so would help keep the actual speed down.

I've seen engines which back up this theory and engines which do not - when a H&M engine is set to run really slowly, barely turning over its fly-wheels they do one of two things when they fire - they either speed up dramatically and coast for ages, or they just barely fart and keep going slowly with only minimal change to the fly-wheel speed. I suspect that the second style of engine is not receiving a full charge of fuel/air as it was designed to do, but the first is. It would be easy to adjust the fuel intake so it got much less fuel.

The fly wheel(s) should also smooth out the hysterisis on both styles of engine.

Jack Watson:
As another simpleton, I am thinking about the fuel consumption of two engines of equal size and efficiency (including that of their "carburettors"), running at high idle (rated speed, no load), one a TG and t'other a H&M.

Seems to me if the TG engine consumes more fuel over a given amount of time, it must either accelerate or increase its mass. John Culp's response:
What you're forgetting is pumping losses. When a TG engine closes its throttle down to limit the fuel-air mixture, it's pulling a rather strong vacuum in the intake tract. That's doing negative work on the piston as it moves down the intake stroke with vacuum on top and atmospheric pressure on the underside of the engine. Remember the old atmospheric engines like the Otto-Langen? That's actually where they got all their driving power from, as a vacuum was created in the cylinder and air pressure pushed the piston back in. The H&M engine has no throttle, the carb is "wide open" all the time, and it creates little vacuum on the intake stroke. Another way of looking at the same thing is that it takes a lot more work to suck the mixture past that nearly closed throttle than to suck a larger amount of mixture through a wide open intake. (The same effect explains much of a Diesel's increased efficiency in vehicular use, where they spend a lot of time at part power. A throttled engine uses a lot of fuel overcoming pumping losses, which the unthrottled Diesel doesn't have much of.)

One other thing makes the TG engine much worse on fuel consumption at idle: When only a very little mixture is let in, these low compression engines with a large clearance space above the piston have a lot of residual exhaust gas left in the cylinder. It can dilute a charge enough that it won't fire until a second charge has come in and flushed out the cylinder enough to make an explosive mixture, causing the "hit and miss" behavior Paul Pavlinovitch mentioned. (Often an idling TG engine fires every other power stroke. I call it "8-stroking.") On each stroke that doesn't fire, unburned fuel-air mixture goes out the exhaust, and the throttle has to open a bit more to compensate, so it's using more than twice as much fuel as it would if you could keep it firing every time at idle and far more than the H&M that intermittently pulls in an unthrottled charge and coasts with negligible pumping losses between hits. At rated power you'd notice much less difference in fuel consumption between the two, and at maximum power with the throttle wide open on the TG engine and both hitting every time, the consumption should be the same.

I already E-mailed Philip about this, but I believe he's quite right in every respect except on the point of a moderately loaded H&M engine running at a steadier speed than at idle. The governor will still latch in and out at the same RPMs, the engine will just slow down to the speed where it starts "hitting" again quicker when it's under load than when not.