Self compensating carburetor
- Thread starter gbravo
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Hi German,
Having never built a Bob Shore's carburetor I can't say what it is but having built many other carbs for model engines I can't think it would be more than an air bleed type. I went to Bob Shores web page and looked at the picture of the carb and this is what it seems to be. I have been following your build of the BMW engine and your recent posting of the carbs looks like you are using an air bleed type. I have had very good luck with these. It just takes a little fine adjustment to the air bleed port and valve and they operate quite well. I have tried several other types but haven't had any better luck than with the air bleed style.
gbritnell
Having never built a Bob Shore's carburetor I can't say what it is but having built many other carbs for model engines I can't think it would be more than an air bleed type. I went to Bob Shores web page and looked at the picture of the carb and this is what it seems to be. I have been following your build of the BMW engine and your recent posting of the carbs looks like you are using an air bleed type. I have had very good luck with these. It just takes a little fine adjustment to the air bleed port and valve and they operate quite well. I have tried several other types but haven't had any better luck than with the air bleed style.
gbritnell
Is Bob referring to carbs that compensate for pressure altitude? Of course in WW2, there was a critical need for maintaining power at altitude, thus we get turbo and superchargers... but even a plain carburettor will have mixture variations as the altitude changes. If that's what it is, no worries, because our engines aren't trying to reach 30,000'
In my experience with small carbs, simpler is usually better. We look for reliable running more than squeezing the maximum joules of power per CC displacement. I do think that some variety of float simplifies things greatly, because a float chamber allows a fuel tank to be positioned anywhere above the carb, and the head pressure the carb sees remains constant so long as there is available fuel.
If there's no float, as the fuel tank empties, the mixture tends to go from rich to lean, sometimes so much so that the engine stalls.
Can you link to a specific web page? I've got Bob's book on coils, and it is a dandy.
In my experience with small carbs, simpler is usually better. We look for reliable running more than squeezing the maximum joules of power per CC displacement. I do think that some variety of float simplifies things greatly, because a float chamber allows a fuel tank to be positioned anywhere above the carb, and the head pressure the carb sees remains constant so long as there is available fuel.
If there's no float, as the fuel tank empties, the mixture tends to go from rich to lean, sometimes so much so that the engine stalls.
Can you link to a specific web page? I've got Bob's book on coils, and it is a dandy.
BillC said:
Why delete posts when someone disagrees? I see people do it when subsequent responses either ignore or go against the suggestion. Now, I have no idea what was posted and whether or not there was anything to learn.
I did try to lookup the Westbury design Bill mentioned, but either the plan set mentioned wasn't the one or I had the wrong one. The article I think Bill was referring to was the Kiwi MkII as described in Model Engineer, Nov. 1960. The text talks about positioning the jet such that fuel draw is appropriate for engine operation at large and small throttle settings. The carb does use a float. It also says you would tune it with minor alterations to the bore in the throttle barrel, just like was done in the early days of RC aircraft.
Not knowing what Bob Shores design is like, I'm not sure if they are similar at all.
Greg
