A Variable Speed Governor... breathing new life into an old Hit and Miss Engine

[MatthewMachinist]

Hi Guys,

Some time ago I got to see a hit and miss engine running at a show. I really like how those engines could run on just about anything.

I began thinking about ways that you could use them today, because of their economy I would love to have one powering a DC motor... used as an emergency generator.

The problem of course is that the variable speed would make it a bad candidate for the job.

Anyway while I was thinking about this I did a job on my small Raglan Lathe which has a variable speed mechanism where you can shift one side of the pulley to change the speed... a form of variable transmission.

So I began wondering about the idea of putting a governor onto the flywheel of the engine, which would drive a V belt, my initial thought is to use a cam operated governor which during high speed would push the pulley outwards providing a small driving diameter to counteract the high rpm, and then when the rpm starts to drop the spring would overpower the cams and the pulley would pull together which would result in a large driving diameter which would counteract the low rpm. I was initially thinking about putting this governor on the driven side... but that would mean the pulley would need to come together during peak acceleration... my instinct is that it would be better for the pulley to split apart during peak acceleration.

Now I have no illusions about this providing perfect speed, it wouldn't, but it should be possible to overcome the highs and lows to a large degree if I am not mistaken?

The second half of the equation is that the bench with the generator motor would be mounted on a pivot pin... so the generator would lean backwards and provide tension on the belt. In use the generator bench would move back and fourth during each firing cycle. This would be based on the assumption that when the hit and miss is firing frequently when you start up... you would make sure the belt was loose and not loading the engine. This idea would also be based on the idea that I would use a larger say 5hp engine, they fire less often than the smaller 2hp versions.

Now I should mention I am a Machinist with decades of experience now... but I have NEVER worked on a governor. So I was just wondering if anyone has experience with machinery design or old machinery, and perhaps you can comment if this idea seems feasible? If I did pursue it this idea would be for personal use, I do not expect this to be economical for commercial gain.

Thanks for any ideas.
Matt.

 

[Peerless Repair]

Yeah you could do all of that...OR, you can get a THROTTLE GOVERNED open crankcase flywheel engine and save a hell of a lot of dicking around and have excellent speed/load regulation.

Something like a 6hp IHC M or 6hp Fairbanks-Morse Z....

 

[texasgeartrain]

With electric power generation continuous speed is important. If powering lets say incandescent light bulbs, they will brighten or dim if going over or under rated speed. Engine speed is directly tied to electric cycles or Hz, like a physical lock. On old school electric items, fluctuations in Hz are not an awesome idea, but are generally more forgiving. If you were powering newer electronics, those fluctuations could damage those components.

With that in mind, I think the hit and miss engines I've seen, the speed changes are too dramatic for electric power generation. I think even with the vee type variable speed belt, it wont keep up in a timely manner. So you would have pulsing light bulbs.

I'm thinking with this style of engine it'd make a good pump engine for pumping water if you could make use of that.

 

[john.k]

For what an open crank engine in runnuing order sells for now,you could buy a new four cylinder diesel to power your project.

 

[Joe Michaels]

I thnk the scheme of using a set of variable pitch pulleys to try to maintain a constant rpm at the generator shaft is not likely to work. The hit and miss engine has a fairly wide band of rpm. The variable pitch pulleys would be in almost constant pitch-changing mode as the engine rpm rose & fell within that band. As generator load increased (or was constant), the hit and miss engine would, in theory, stabilize (if such a word can be applied) to a steady frequency. The variable pitch pulleys would need some kind of independent governor to adjust their pitches/ratio to maintain that constant rpm. I think the end result would be either the governor on the pulleys was constantly playing 'catch up' to what the hit and miss engine rpm was doing, and likely putting this governor in a 'hunting' mode.

I would not mount the motor/generator on a pivoted mounting. With the unstable rpm, the generator will be bouncing and the belts will be adding some additional vibration. Who knows ? With two governors, some hunting, and a generator on a 'live' mount plus flapping belts, the whole works might go into resonance.

It brings back a memory of a diesel generator that supplied power to a sawmill camp/jobsite I worked at in Paraguay over 40 yrs ago. The engine was a little 4 cylinder diesel power unit built in Brazil under license from MWM. The generator was a "Kohlbach" Brazlian made unit with brush type exciter. The engine had a lever-operated clutch and drove the generator thru multiple vee belt pulleys. A concrete pad had been poured and both these units were bolted to it. The belt tension was maintained, after a fashion, by loosening the generator mounting bolts and setting belt tension with a pinch bar while a second guy tightened the mounting bolts. In service, the generator crept towards the engine and the belts started flapping. The generator mounting was sloppily made, so the generator shaft also went out of parallel with the engine's shaft. This got the engine's mechanical governor (on the injection pump) to hunting. The result was the brushes and commutator in the exciter (which was cantilevered off the the main generator' rotor's shaft end) went to hell in a hurry. This situation kept recurring until the lead mechanic working with me made slotted rails for the generator mounting and added jacking screws (made from all thread rod) to adjust and maintain belt tension.

If you are intent on using your hit and miss engine to generate electricity, you might look into using an inverter. Ungoverned sources of energy such as very small hydro turbines and wind turbines drive permanent magnet DC generators. This output is run thru inverters to make AC current. This current, in turn, is then rectified to make DC current to charge storage batteries. The storage batteries act as a kind of 'electrical flywheel' and provide a stabilized DC output which goes thru a final inverter to make AC house current. Plenty of systems of this type are in use by 'off grid' people with micro hydro turbines, waterwheels, wind turbines, and combining with solar panels in some cases. I cannot speak for how a permanent magnet generator will hold up to the varying rpm of a hit and miss engine. What does come to mind here is the old buzz saws driven by hit and miss engines. These often had a heavy solid-web flywheel on the saw arbor (which a lot of oldtimers called a 'balance wheel'). The science of governing prime movers is just that- a science in itself. Hit and miss governed engines were never intended to drive anything needing a constant (or nearly so) rpm. The hit and miss engines had heavy flywheels of their own to try to stabilize their rpm and carry them thru the 'miss' periods when the governor caused the engine to coast down. My own term for this is "playing catch up, with overshoot". IOW, when the engine rpm drops low enough, the governor unlatches the exhaust valve and the engine fires again ('the hit'). The result is some overshoot of rpm, causing the governor latch the exhaust valve open and the 'miss' or coast-down happens. Heavier loads narrow this band. Under heavy enough load, the engine will be 'on its knees', making relatively steady rpm as the governor is really not doing anything other than holding the exhaust valve unlatched. These engines varied 'governed speed' (if you could call it that) by varying spring load on the governor. All this did was to narrow the band or widen it at which hit and miss occurred. Crude but effective for the time and applications. Not so good for generators.

 

[enginebill]

If you use the DC to charge batteries, the speed variation won't matter.

 

[Peroni]

There's no need to reinvent the wheel as it were, all this has been done before well over 100yrs ago. A hit miss engine can be used for indirect lighting with no issues. Engine drives the generator, generator charges batteries, and the lights will burn nice and steady running off the batteries. For direct lighting you will need a throttle governed engine. It can drive the generator and directly power the lights. If you have money to burn then pick up something like a Fairbanks N or maybe a nice Otto in the "special electric" version. These will be throttle governed with extra heavy flywheels. Lots of makers offered them for direct lighting. Otherwise pick up something cheaper like a Fairbanks Z or IHC M. Fairbanks, among other makers, even offered a complete home lighting system.

Fairbanks Morse Home Lighting Unit

 

[JST]

Also, if you have ever put a hit and miss under a load, they steady right up as the load gets heavier. As they "hit" more than "miss" the speed variation is less.

When at near full load, they are pretty much just running similar to WOT and not varying much. So, don't baby the thing, set it up with a good load.

 

[animal12]

I thought I read somewhere that governors were a option on some hit & miss enging ?
thanks
animal

 

[john.k]

The hit and miss is the governing......generally an inertia weight connected to the inlet valve ,or exhaust that doesnt open the valve on the miss ...........more complicated is the flywheel governor,which is also an inertia weight connected to the valvegear........for bigger engines,there is various Pickering type governors that operate a throttle valve.

 

[Peerless Repair]

The hit and miss is the governing......generally an inertia weight connected to the inlet valve ,or exhaust that doesnt open the valve on the miss ...........more complicated is the flywheel governor,which is also an inertia weight connected to the valvegear........for bigger engines,there is various Pickering type governors that operate a throttle valve.

That is mostly inaccurate info....

 

[Peter from Holland]

What about a VFD in reverse ????
Alternating frequency in Constant frequency out

Peter

 

[Joe Michaels]

The hit and miss engines I have seen (and made a few parts for) here in the USA had 'atmospheric' or "automatic" intake valves. The exhaust valves were worked by pushrod & rocker arm. The governors on these engines were flyball type. The governors worked a latching mechanism which held the exhaust valve open when the engine reached the set speed of the governor. Most of these engines used a type of magneto which worked off linear motion (another pushrod off the camshaft ?). These were either Webster or Wico magnetos as I recall. I do not recall if the hit and miss governing also stopped the magneto from 'firing'.

As this thread develops, I am reminded of the charging generators in older vehicles. These made charging current for the battery over a wide range of rpm. By the mid 60's in the USA, alternators took the place of vehicle generators. An alternator uses the vehicle battery for field excitation. It produces AC current, and has a rectifier (diodes) to convert this output to DC for battery charging. Recently, I was asked to help find replacements for some 32 volt alternators used on a smaller diesel locomotive. I knew this voltage was more common nowadays for marine applications. Railroads, like farm lighting systems, used 32 volt DC current for lighting and headlights. The alternator vendor I found was primarily a supplier of marine electrical stuff. Their tech support told us that output voltage varied over a fairly narrow range vs engine rpm. We needed 70 amp outputs on the alternators as the batteries on the locomotive provide excitation to the main generators and traction motors. The tech support person told us what rpm range we needed to have the alternators make at least 70 amps, and we sized the alternator pulleys based on engine rpm and available pulleys on the diesel engine.

I think the OP might want to consider using a vehicle alternator and 12 volt battery, driven by his hit and miss engine. A vehicle alternator with an internal diode board and 12 volt battery would work well belted off the hit and miss engine. Getting a heavier duty alternator from a diesel truck or heavy equipment engine and charging two (2) 12 volt batteries in parallel would make a good stable power supply off the hit and miss engine.

 

[JST]

The hit and miss is the governing......generally an inertia weight connected to the inlet valve ,or exhaust that doesnt open the valve on the miss ...........more complicated is the flywheel governor,which is also an inertia weight connected to the valvegear........for bigger engines,there is various Pickering type governors that operate a throttle valve.

Nope..... they are just what they say. The speed depends on load, and the ratio of "hits" vs "misses".

Usually, the "governor" holds the exhaust open for "misses", and often blocks the magneto from being triggered as well.

 

[Peroni]

Usually, the "governor" holds the exhaust open for "misses", and often blocks the magneto from being triggered as well.

Seeing that John K is from Australia he is likely more familiar with the English built Crossley, Blackstone, Hornsby and the native Ronaldson Tippett engines. Most of those govern the intake valve and the engine will coast against compression when on the miss cycle. Quite different from those in the US where most govern the exh valve and breath freely thru said vale on the miss cycle.

 

[john.k]

Im not that familiar with any kind of hit and miss engine,and dont claim to be .............there are thousands of different engines and probably hundreds of different methods of hit and miss governing...........As mentioned,heavy flywheels are the main factor in steady running with these engines.

 

[JST]

Seeing that John K is from Australia he is likely more familiar with the English built Crossley, Blackstone, Hornsby and the native Ronaldson Tippett engines. Most of those govern the intake valve and the engine will coast against compression when on the miss cycle. Quite different from those in the US where most govern the exh valve and breath freely thru said vale on the miss cycle.

The British have had a penchant for doing things differently... But at the end of the day, it is still the ratio of hits to misses that governs the speed.

Some of the old French rotary aircraft engines were sort of similar, no throttle at all, you cut the ignition intermittently. I seem to recall reading that those could not be effectively throttled. The intake coming through a "mixer" and then through the non-moving crankshaft was already a high friction lowish flow situation.

You can think of hit and miss as an "all-or-nothing" throttle. Either going WOT or cut off and coasting.

 

[MatthewMachinist]

Thanks for all of the replies guys, using a hit and miss is still an option but I dont think the governor idea is best... Joe Michaels mentioned some very good points about resonance and other points that I had not initially considered.

I am also looking into a small cheap diesel unit. They seem to be quite efficient on fuel as well.

Thanks again,
Matt.

 

[Peroni]

Some of the old French rotary aircraft engines were sort of similar, no throttle at all, you cut the ignition intermittently. I seem to recall reading that those could not be effectively throttled. The intake coming through a "mixer" and then through the non-moving crankshaft was already a high friction lowish flow situation.

You can think of hit and miss as an "all-or-nothing" throttle. Either going WOT or cut off and coasting.

It was called a 'blip switch' and it's use was not confined to just the French manufacturers.

 

[dundeeshopnut]

Not sure of the availability for you Kiwis but over here there is a crapton if 45 hp [2203] Kubota's kicking around from reefer units [usually Carrier] that don't meet tier 4 emissions. 500 clams gets you a nice fairly low hour unit [they usually run for 20 000 hours or so], and they work wonderfully belted to a 15 kw generator. I have one set up on a wagon with a 250 gallon fuel tank that runs drainage pumps at the back of the farm in spring or when needed. It also serves as standby power for our house which is on a different lot than the dairy barn. With their 13 liter oil pan, they can run for weeks without supervision and use only about 2 1/2 liters of fuel per hour working. The governors on these are exceptional and I have no trouble getting smooth 60 cycle AC from it .