# gasoline carb



## Kermit (Dec 18, 2008)

I didn't know a carb could be THIS simple.


Hope somebody finds this useful,
Kermit


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## bentprop (Dec 18, 2008)

Maybe I'm a bit dense :big:,but how does the valve operate?It IS a very simple carb,but so is an air-bleed carb,like used on small rc engines.


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## tel (Dec 18, 2008)

I assume it relies on the vacuum of the inlet stroke to lift the valve off the seat against the spring pressure?


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## Paula (Dec 18, 2008)

It looks a lot like the Lunkenheimer, which was often used on hit & miss type engines:






Tel is right -- the poppet valve is opened with the pressure drop as the piston goes down for the intake stroke. The Domestic engine that I built (my avatar) had this type of carb, but I never could get it to work well with the poppet valve, and eventually replaced it with a dummy stem (for external appearance). Worked fine after that.

I had a 2-cylinder Maytag engine once that basically just had a fixed orfice in a venturi pipe, attached to a standpipe from the fuel tank. Dirt simple, but it worked.

Paula


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## bentprop (Dec 18, 2008)

Thanks Tel,Paula,this proves the point,you're never to old to learn ;D


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## rake60 (Dec 18, 2008)

Very early carburetors were even simpler.
I have a 1935 Jaeger 2HP engine restoration in my projects to finish list.
Long ways to go on that, but the carburetor has seen a bit of improvment.
They didn't call it a carburetor then, it was a mixer. Today it looks like this.






The clean threads on the mixing needle show that is the only part I have made
new for it to date.

Anyway, that is all there is to it.
The fuel line from the tank attaches to a pipe threaded inlet, opposite the needle.
The horn facing forward is the air intake and the upper 3/4" pipe thread outlet is
fitted to a pipe nipple that is screwed directly to the recess above the intake valve.
It almost looks too simple to work but it did very well for about 50 years.

Rick


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## Kermit (Dec 18, 2008)

Wow, Awesome! I'm in love with you guys.

Now, during my exploring some old tomes: It was written of a tank with folded gauze and wire screen, which was allowed to wick up gasoline and also provide a filtered flow of air through the screen- (evaporating the gasolene)

A setup I would think of as a fuel soaked air filter!

Kermit


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## GailInNM (Dec 18, 2008)

As we just passed the 105th anniversary of the Wright Brothers first powered aircraft flight a few days ago, it is probably worth noting that their "carb" was essentially a flat pan that the fuel dripped into with the air flow over the fuel picking up vapors to make the air-fuel mixture used by the engine. No control at all except for a valve to turn off the gravity fed fuel. The pan was warmed by the engine to help vaporize the fuel.

Other bits of info on the engine. It was about 200 cubic inch displacement (3.27 liter) and their first tests showed it delivered about 4 HP. They ran part of their workshop with the engine while tweaking it and working on the aircraft, and as I recall they got it up to a little over 8 HP by the time of the first flight.

Gail in NM,USA


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## te_gui (Dec 18, 2008)

Friend of mine who has a large collection of antique machinery once described early carbs as "A tin can with a hole in it". With a lot of this old stuff, thats pretty close

Brian


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## ghart3 (Dec 18, 2008)

Another simple carb is the one used on a model of Henry Ford's first gasoline engine.
The lower sight glass in a drip oiler is removed and a fine mess screen is inserted for the gasoline to drip on. 





When making a carb like the Lunkenheimer,  where the hole wants to be in the center of the valve seat,  drilling the hole from the outside first and then machine the valve seat so the hole is in center of seat.  Much easier then drilling and aiming for center of the seat.

Gary


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## T70MkIII (Dec 20, 2008)

Looking at the first carb on the thread, how would you throttle such a thing? Or is that out of the question with such a design?


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## Kermit (Dec 20, 2008)

Looks like its all manual. A knob for the fuel amount and one to limit the opening of the air intake valve. Seems you have to adjust BOTH of these for a throttle function.

So now someone needs to make one of these.


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## nemt (Dec 20, 2008)

The carb as mentioned is also used on the Wyvern, the engine I have build several years ago and is also the picture you see when you read this. I have used the same type on Topsy Turvy.
Works very well. Interesting is that on the Wyvern carb there is a possibility to set it up for two fuels, petrol or propane gas.
Next weeks I will proceed on the Mastiff and I have planned to bring some pictures again on this forum.

Merry Christams and a happy new year to you all joining this magnificent forum.

Nemt
 from a dreary Holland. No white Christmas overhere.


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## ronm (Dec 20, 2008)

T70MkIII  said:
			
		

> Looking at the first carb on the thread, how would you throttle such a thing? Or is that out of the question with such a design?


That kind of mixer was used on hit & miss governed engines, the speed was regulated by holding the exhaust valve open until the speed came down. Every time it fired, it was a full charge. The intake valve was atmospheric, i.e. it had a light spring & was opened by vacuum on the intake stroke. When the exhaust was latched out, there was no vacuum, so the intake didn't operate. What they call the jump valve in the mixer shown created enough vacuum to suck the fuel up the line from the tank..like this...
[ame]http://www.youtube.com/watch?v=4nH0QDSIYpc[/ame]


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## itowbig (Dec 20, 2008)

wow i sure do learn a lot here . many thank U's to all.
great stuff. love that engine too


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## kf2qd (Dec 20, 2008)

Looks a lot like the carb on a old OMC 2 cylinder outboard I used to have. It also functioned as the read valve. THrottle was done with the spark advance - push teh advance to the other side of the engine and start it backwards for reverse. It was common at one point in time to use the spark advance to control speed rather than a carb butterfly. The outboard also had a button to push to free up the disk which would become stuck when the fuel all evaporated off and got gummy... That carb also had a float - push on the pin that stuck ou the top of the bowl and prime it.


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## Phelonius (Jan 26, 2009)

I once did this to run a briggs and stratton engine. I made a needle valve drip gasoline onto a piece of aircleaner foam at the intake. T'werks good!

 Can it get any simpler?

 Phelonius


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