Hit and Miss based on Chuck Fellows design

[FIXIT]

Hi
I've started building a Hit&Miss loosly based on Mr Fellows and Brian Rupnows design and i notice in one there is a 2/1 gear reduction on the actuation rod letting "fire" every two strokes and the other very clever and nicely made engine has a regulator which apparently would "fire every stroke until it comes up to speed.

The question/explanation i have/need is can this engine 'fire every stroke and control the speed by restricting the air or is there another reason for the gear reduction,

I've not seen this type of engine before so i need your wisdom please.

Steve

 

[Jasonb]

Most hit and miss engines are 4 stroke engines so you need the 2:1 reduction so the exhause is onlty actuated on every other turn of the crank

Jason

 

[cidrontmg]

Yes, these engines are 4 stroke, so they need the 2:1 reduction (gears, or other means of accomplishing the same effect). The governor is there to limit the max. speed. When it actuates, it "floats" the exhaust valve, so it stays open all the time. As there is no suction then, the intake valve won´t open (the valve will open only with suction, there is no mechanical linkage to open it). So the motor will idle, for some rotations (2-4 is good, 7 would be excellent...), until the revs fall, the governor stops keeping the exhaust open, and the motor fires again. If there would be no governor, it would be a "normal" 4 stroke engine, instead of a hit and miss.

A hit and miss uses less fuel, is FAR better cooled (the piston just pumps air into and away from the cylinder when it idles, cooling it from the inside). And is not supposed to run fast.
When there is a load on the engine, the engine slows down, the governor won´t actuate, so the engine fires at (almost) every stroke, depending on the load.

These things work with very simple carbs. If you build a "real" carb to go with it, and limit the revs with that, you´re in for a very different engine (a normal 4 stroke). Then you need a far better cooling system, a far better lubrication, and a far better balancing of the engine (a usual hit and miss is not famous for its balance...).

So, go with the 2:1 and the governor, otherwise you´re not building a hit and miss...
;D

 

[arnoldb]

Hi Steve.

Your post is somewhat confusing...

I think Brian did build a true Hit 'n Miss gas(petrol) engine. That used the gears.

Are you maybe confusing it with the compressed air Hit 'n Miss that came from an original design of Chuck, and that Brian added the hit and miss part to ?
This one runs as a compressed air engine, and there is no gearing involved- it is a completely separate engine from Brian's other hit 'n miss.

Regards, Arnold

 

[FIXIT]

I think i have confused everybody (including myself)


Yes it's the compressed air engine with the inlet opened from the crank and the 'automatic exhaust valve, but it shows a 2:1 gear ratio operating the inlet.

I can see how it operates but is the gear ratio necessary to give the exhaust time to shift or for some other reason.

thanks for replying guys


Steve

 

[johnthomp]

i built a rough one wich is two stroke without the governor on the flywheel and the slowest it will run is around 20psi at 300rpm and the fastest ive had out of it is a whapping 3500rpm at 80 psi ill try and add a foto of it in a little while to give you an idea of how i set it up aww sod it ill even show you the double size one im halfway through watch this space
reguards john

 

[johnthomp]

http://i107.photobucket.com/albums/m310/amd47/SDC17541.jpg[/img]]
as expertlt demonstrated by my little lego engineer bloke i just put a cam straight on the crankshaft in the position of the crank being at 12 o clock and the cam top being at 9 o clock it ran first time the engine is still in its ugly rough state coz i havent decided weather to paint the engine yet or polish it
hope this picture helps
reguards john

 

[FIXIT]

Thanks John
for the picture i think it clears it up for me , I think i will folllow your valve design first .

I'm building this from my 'scrap box' and it's turning out well at the moment so not having to cut gears at the moment is good,

I've just have to learn how to make a nice looking cam like yours.
i will post a pic of my efforts later.

Regards Steve

 

[johnthomp]

how i made the cam was cheating a bit all i did was centre and drill out one ed of a 1" mild steel bar and glue a paper stencil of the cam shape on the end then scribed round it and ground it out ith a 4" angle grinder then finished it up with a file before cutting the cam off the end of the bar
i also made it thick enough to take a 3mm grubscrew tapped into the edge of it and cheated with that by tapping it out screwing a panhead screw into the hole till i see it in the shaft hole then backing it out a couple of turns cutting it a little proud of the surface then cut slothead in the end with a junior hacksaw and screw back in with a tiny screwdriver or in my case a sharpened drill bit but end works a treat
hope this helps a little more fella
reguards john

 

[Brian Rupnow]

If you are working from my plans, you will see that I did not use any gear reduction. Its not necessary that it only fire on "every other stroke". When Chuck did his original design, he used the gears to emulate a true 4 cycle hit and miss engine behaviour. Being a natural cheapskate, I did not need it to sound like a 4 stroke engine, so the gears are not used in my version of the hit and miss engine.---Brian

 

[FIXIT]

Hi Brian

thanks for that, i was only looking at your build to get ideas as if i needed gears or not and i really like the Governor that you've' designed/built but i think i will have to 'up my game ' to make that at the moment,
so i will try to acheave a running engine first then learn from there.

Regards Steve

 

[Brian Rupnow]

ArnoldB---Somebody is confused!!! I have never designed nor built a hit and miss internal combustion engine. The one which I did the design for was a steam/air engine, and I can't take the credit for any original thinking there. It was purely Chucks original design, and all I did was make a set of engineering drawings that were a bit easier to follow. I have built a Webster internal combustion engine, and it is a 4 stroke, but not a hit and miss. Its not my design, but was designed and posted as "public domain" by Mr. Webster (I assume).---and he did a very fine set of plans for it. Its a sweet running engine.

 

[cfellows]

Just saw this thread. Brian is right. I added the 2:1 gearing to emulate a true 4 stroke sound and operation. If you are going to add the governor to make it a hit n miss, the geared valve train will add a lot to the complexity and won't really add much to the sound. I'd go ahead and make it a 2 stroke if you are going the hit n miss route.

Chuck

 

[FIXIT]

Thanks Chuck that's just the information i needed I'm not so confused anymore (but maybe tomorrow's another day)

Steve