propane carb

[fourstroke]

Are there any designs for a propane carb on here that anybody can point me to or reccomend?
Thanks
Dougie

 

[werowance]

well, I have seen regular carbs used and if it had one just remove the float. and then use a demand propane regulator on that.

I have also seen just a collar made to go between the regular carb and the block so you could "dual fuel" it. also needing a demand regulator.

cant help on the carb but I believe no matter what you would still need the demand regulator, here is a link to the model engine size demand regulator you could use and just hook the outlet for the propane between carb and block or something similar.

about 1/4 of the page down look for demand regulator.
http://www.floridaame.org/HowTo2.htm

good luck, if you build it I want to see it.

werowance

 

[Rustkolector]

If you can tell us what type of engine you are going to use propane on it would help a great deal. I use propane on most of my engines, but they are all constant speed engines.
Jeff

 

[fourstroke]

Thanks for the replies
I am hoping to run one or both of the engines I am building, the details are in a thread on this site in the engines from castings setion " a side valve from home made castings"
Its 38mm bore x 40mm stroke
Thanks
Dougie

 

[Rustkolector]

Dougie,
Gaseous fuels are more susceptible to leaning out on increasing speed when using a carb designed for liquid fuels. However, these carbs are often the simplest and easiest to use with propane. The jet and needle are too small ideally for propane, however, the right kind of liquid fuel RC carb can work very well. You need a self-compensating type carb that is not of the air bleed type. One that has the needle assembly on a threaded shaft so that the needle moves away from the fixed jet on throttle opening thereby increasing the jet opening. These will work. The only problem I have found with these carbs is that the needle valve setting is usually within 2-3 turns of falling out. You may have to provide a packing or seal of sorts on the needle shaft to assure no air enters through the needle threads thereby upsetting the fuel-air ratio. This simple carb has worked well for me.



There is also a string type grass trimmer on the market built in China that runs on propane. I cannot remember the brand name, but the engine bore x stroke is about the same as yours. You might want to look at that possibility. You are also not too much smaller than some small commercial engines that have propane fuel systems available as aftermarket.
Jeff

 

[deverett]

I think it was Bob shores who suggested that when converting an engine from running on petrol to propane, stick a bit of masking tape over the air intake and pierce it with a small drill. Gradually increase the size of the hole till ideal running conditions prevail. Then make a choke with that size hole to fit permanently in the carb throat.

Thought this was on the fame site - hints & tips, but can't see it now.

Dave
The Emerald Isle