Sometimes, in the early part of the year, "cabin fever" strikes the engine mailing list on the internet. Subject matter goes wildly off topic and tempers have been known to fray. This year, however, was vastly different as we enjoyed some of the best discussions seen for a long time, and raised several possibilities for passing on to the readers of GEM, such as the correct way to lift an engine, pouring Babbitt bearings and making hopper gaskets. While talking, via email, about what people find interesting to see at shows, the subject moved from displays to the engines themselves and how they should be run, and before long there was such a vast amount of information flying back and forth around cyberspace that even by keeping to the most relevant and informative mails I found myself with an article too long for a single issue of GEM. So, here are both parts of the article on the governing of stationary engines. Enjoy!

* 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 10 seconds (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 no "documentation" to back this up, it is just what I have been told by several old time engine men whom I greatly respect.
I do know that a larger hit and miss engine will latch up on the governor even if it is under a constant load. My 5 HP Green Economy would hit "all the time" when we belted it up to several implements. My 9 HP Galloway would not.
Perhaps someone with some old literature can shed some light on this discussion. I would be interested to know if what I have been told is true.

* That is not to say 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. It is 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.

* 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.

* 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.

* 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.

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

* 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.

* 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 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.

* 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've seen discussions of this in some of my early engine books but can't seem to find it 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 governed engine you would almost need a tachometer 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.

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

* Faulty logic. 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.

* 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!

* 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.

* 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 mixture 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?

* 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.


* Another question along these lines:
What about engines where the horsepower was raised by the manufacturers simply by setting the governed speed higher?
With such an engine, would running it on the previously rated max load probably cause damage?

* Many engine manufactures (eg. Hercules, Witte) claimed that their engines were PURPOSELY 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. 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.

* 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.

* 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.

* 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.

* 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, 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."

* 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 really have wondered about this for some time now since I use my 7 HP Alamo to run my cane mill, and it is firing under load as long as I am keeping the feedbox full of cane. It does latch up at times when the box isn't full, so it might just run for 5 minutes solid with a few misses in between. The mill I am using requires a 6 HP gasoline engine or 4 HP steam engine. It usually takes an hour and a half to make enough juice for one batch.
From what I am hearing this engine shouldn't be run in this manner even though I am using a machine that is rated below the horsepower the engine. One more excuse to get a larger engine!
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.

* To summarize 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 efficiency 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 unnecessary)
I'd add that a H&M governor 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.

* 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.

A cylinder and piston on a hot running engine wear considerably less than on a cold running engine. Rate of wear climbs dramatically as temperature 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 manufacturer's specs.

When 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.

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.

* 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.

* 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.
I read somewhere that in the late teens gasoline could cost as much as $0.05 per gallon, but Kerosene cost ONLY $0.03 per gallon!

* 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.)

* 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.

* 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. 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.
My guess is that the 7 HP Alamo working a cane mill would meet this "test" and run the way that a H&M engine should perform, but please, don't take this, however, to in ANY WAY suggest that you should not buy a larger engine!!

* Have you every closely watched T/G engines running? 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.
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 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/G really does fire every time when not under load there is probably something wrong
with the governor or fuel system.

* 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.

* 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 within 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.

* I've been following the discussion on rated power of engines with great interest, and have been thinking about what has been said. 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 economical. 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 than 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, ie 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, ie 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 sett, 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, eg 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 or kerosene engines. 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.

* 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.
So, throttled governed engines are not constant speed engines.

* Essentially you are right here, however I expect that the hysteresis 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 accelerating them - of course this cannot happen instantly (ie the fly wheels have to accelerate 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 hysteresis on both styles of engine.

* 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.

A marathon (and fascinating) discussion which I'm sure will make most enginemen listen and watch more carefully to what their engine is doing, hopefully with greater understanding. I might add that even more information was forthcoming about the less common methods of governing engines, many of which were manufacturer-specific, so leaving it at just throttle-governing vs. hit and miss covered the majority of engines and prevented us from completely taking over GEM!

stationary-engine@atis.net

Site Index

Back

Articles Index

Next

Email










©FBI 2002