Briggs & Stratton hit & miss idea

[Chevyguy207]

Hello everyone

I was wondering if anyone has done this or could lead me in the right direction. I had an idea this morning about making a old briggs & Stratton motor in to a hit & miss engine. It seems to me it would be pretty straight forward but I'm not to sure how to go about it. I have a engine all cleaned out and ready for it.


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[Philjoe5]

OK, as someone who has never built a working hit-n-miss I'll take a stab at it.

You have the basic engine, currently throttle controlled. You need to make the hit-n-miss mechanism.

This is a spring loaded device that will engage a catch plate of some sort. The springs counteract the centrifugal force of the governor weights. When the engine speeds up, the centrifugal force acting against the springs allows a rod to engage the catch plate and hold the exhaust valve open.

With the exhaust valve held open, there's no vacuum, therefore, no fuel intake. The engine is in the miss mode and starts to slow down. As it does, the governor weights collapse against the spring causing the the rod to retract from the catch plate. Now the exhaust valve is in its normal operating condition and the engine is in its hit mode.

There are a number of hit-n-miss governor designs available. You just need to pick one and make it.

Cheers,
Phil

 

[gus]

Briggs&Stratton Engine ------gave me my very first engine sizing/selection lesson to drive Ingersoll-Rand T-30 Model 253 with 5 hp motor. You just cannot use a 5hp B&S engine to replace the 5 hp electric motor. The Poor engine did run for a while and finally died. :hDe::wall:
The B&S Engine Sales Manager was very kind,he gave me a 10 hp engine F.O.C.

Very sad I did not get his name.He taught me Single Piston Gas Engine application and selection to drive air compressors. He gave me a very simple layman's formula which I remembered forever.Twenty years later I taught the Singapore Armed Forces application and selection of B&S Engines to drive water pumps and Gensets.
And Genset application for their moble workshops. I also gave them a very simple formula.
Time passed and thats 40 years ago.

 

[Chevyguy207]

OK, as someone who has never built a working hit-n-miss I'll take a stab at it.

You have the basic engine, currently throttle controlled. You need to make the hit-n-miss mechanism.

This is a spring loaded device that will engage a catch plate of some sort. The springs counteract the centrifugal force of the governor weights. When the engine speeds up, the centrifugal force acting against the springs allows a rod to engage the catch plate and hold the exhaust valve open.

With the exhaust valve held open, there's no vacuum, therefore, no fuel intake. The engine is in the miss mode and starts to slow down. As it does, the governor weights collapse against the spring causing the the rod to retract from the catch plate. Now the exhaust valve is in its normal operating condition and the engine is in its hit mode.

There are a number of hit-n-miss governor designs available. You just need to pick one and make it.

Cheers,
Phil

Thank you for this information Phil. When you say "normal operation" do you mean the exhaust valve is back to running off the cam or does it stay closed until the engine fires?


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[Philjoe5]

Yes, in the hit mode, the exhaust valve is operating off the cam.

Some hit-n-miss engines use atmospheric intake valves and only have the exhaust valve operating off of a cam.

Cheers,
Phil

 

[Chevyguy207]

Ok so I have to trim the push rod down so I can fit some sort of catch in there to hold the exhaust valve open until it's ready to fire than it will have to let the valve fall back down on to the push rod to run normally right? And as for the catch plate where would I find some designs to base mine off from?


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[Chevyguy207]

Ok I've started this project and there's no turning back now. I made the cut into the crank case and exposed the cam gear. My plan is to use the cam gear to run the governor. I'll keep adding pictures as I go.


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[Ripcrow]

Don't know much but if u only have the exhaust valve operating on the cam can't u gear the cam at 8/1 so that it only fires every 8 strokes

 

[Chevyguy207]

I'm not really sure. This will be my first hit & miss build. I'm considering running both intake and exhaust off the cam but I don't know if that's the best way or not.


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[Chevyguy207]

I did a little test today to see how the intake valve will have to work on this motor and it turns out I can leave the intake valve set up the way it comes from briggs. All I had to do was remove the push rod from the cam and the heavy spring that was in there, replace it with a lighter duty spring and just like that I have a atmospheric intake valve.


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[Chevyguy207]

The only problem I'm having now is where this is my first hit and miss build is I'm not sure how it should be geared. Should the gear that will be running the shaft that will be hooked up to the governor be the same size as the gear on the crank or the one for the cam?


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[misfitsailor]

Instead of interrupting a valve from closing, you could just add a compression release, and rig your governor to open it to cause the engine to coast.

 

[jschoenly]

I converted a Briggs to a Hit and Miss as my first project, even showed it at NEMES one year when I was about 12 or 13. What I did was as follows:

- Removed stock flywheel and cut crank to accept 2 spoked flywheels (1/2 scale olds to be exact)
- Trimmed the bearing cover (with the points) to a circle and used the points only to fire a coil
- Removed the intake tappet completely
- make a new exhaust tappet with a sharp groove in it (carefully measured)
- tappet was made after I drilled a hole intersecting the exhaust tappet bore for the "catch"
- made a "catch" rod that was actuated by flywheel mounted governor.

Sadly, this engine has been apart and neglected for a while, but your post might just be what i need to break it out and "restore" it. There were a few adjustments needed to the governor and I made a 1/4" pipe lunkenhiemer carb that i never did get on it. I will try to get this out and take a few pictures for you (and hopefully work on it!).

 

[gus]

Is Briggs&Stratton plant still there. Lister is gone. Over here in Singapore market,its all Honda and Robin.The Chinese engines are untouchables. The construction folks just won't touch it.