I have just finished building a demand valve designed by jerry howell, but find in Australia , there is very limited supply of lpg equipment for this application. I need a regulator to control 2 to 4 psi and a design for an effective carburettor to suit a 1" bore and 2" stroke engine . Rpm around 250 . Any help would be appreciated.
lpg fuel
- Thread starter grapegro
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Cogsy
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I think the normal BBQ regulators are around 2 psi, but of course they aren't adjustable. Ebay is a good source of adjustable regulators though. I just bought a 40 psi one brand-new for $30 and picked it up locally in Perth.
As far as carbies go, I've read that you can use the normal carb for the engine but you need to choke it. You put some tape over the intake with a small hole in it, then keep increasing the hole size until the engine runs well. Once you know the hole size you make a permanent choke with that size hole in it.
That's literally all I know.
As far as carbies go, I've read that you can use the normal carb for the engine but you need to choke it. You put some tape over the intake with a small hole in it, then keep increasing the hole size until the engine runs well. Once you know the hole size you make a permanent choke with that size hole in it.
That's literally all I know.
canadianhorsepower
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Cogsy
you can remove that regulator from inside his Clamp shell
then you can fully adjust it
cheers
Luc
you can remove that regulator from inside his Clamp shell
then you can fully adjust it
cheers
Luc
Richard Williams, who designed the popular propane demand valve, gives this advice for finding the bore size of a carburettor designed for propane (I originally thought it was Bob Shores who wrote this):
Using propane you will need to enlarge the fuel orifice. For instance if you have a .040" hole for gas, propane would be .060" to .080". Also you may need to make the intake hole on the carb smaller to pull more vacuum. An easy way to check this is to put a piece of masking tape over the intake of the carb and put a small hole in it. If the engine runs too rich, enlarge the hole. When you can control the fuel with the needle valve, about two turns open, the hole is just right.
Dave
The Emerald Isle
Using propane you will need to enlarge the fuel orifice. For instance if you have a .040" hole for gas, propane would be .060" to .080". Also you may need to make the intake hole on the carb smaller to pull more vacuum. An easy way to check this is to put a piece of masking tape over the intake of the carb and put a small hole in it. If the engine runs too rich, enlarge the hole. When you can control the fuel with the needle valve, about two turns open, the hole is just right.
Dave
The Emerald Isle
chucketn
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canadianhorsepower
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Hi Chuck you can close it completely I know that part
on the other side I never went fully open I was going to melt my BBQ:fan:
cheers
Luc
chucketn
Senior Citizen
Sounds like it's worth experimenting with!
I happen to have an adjustable propane regulator, but my casting buddy doesn't.
Chuck
I happen to have an adjustable propane regulator, but my casting buddy doesn't.
Chuck
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Hi Grapegro,
I use propane on 1" bore slow speed (600RPM) engines. Standard RC carbs are satifactory. The needle valve needs to be opened significantly more turns, but they work well. I use Weber "Go Anywhere" portable gas grill regulators (Ebay) on the disposable 1 lb propane bottles commonly found in the US. Their output pressure is fixed at 4" WC (water column) pressure and is more than adequate pressure to the demand regulator. You do not need more than 4-5" WC pressure on the input side of the demand regulator. The output side of the demand regulator runs at a slight negative pressure created by the vacuum signal from the carb. I usually use the smallest throat dia. carbs I can find. A 3mm (.100"-.125") throat dia. is usually fine for a multi-cylinder 1" bore engine for variable speed operation without using a restrictor plate. A restrictor plate is needed only when the carb is too large to pull an adequate vaccum signal on its own. Most slow and medium speed model engines (liquid or gaseous fueled) have carbs that are much too large. Smaller is most always better.
One more thing on RC carbs. Do not use an air bleed type when using LP gas. Find one that is self compensating. On this type carb, the gap between the needle and seat should open more as the throttle is opened, and vice versa. This type carb maintains a reasonably steady fuel-air ratio when opening or closing the throttle, even on LP gas. Otherwise, the needle setting will need to be adjusted any time the throttle setting is changed (even slightly changed).
Also, always build-in a priming button on your demand regulator to allow gas to flow at pressure to the carb. I believe Jerry's regulator design has the priming button. Call it a choke or whatever, it really helps in starting your engines. Once you learn to use it, your engines will start very easily.
Jeff
I use propane on 1" bore slow speed (600RPM) engines. Standard RC carbs are satifactory. The needle valve needs to be opened significantly more turns, but they work well. I use Weber "Go Anywhere" portable gas grill regulators (Ebay) on the disposable 1 lb propane bottles commonly found in the US. Their output pressure is fixed at 4" WC (water column) pressure and is more than adequate pressure to the demand regulator. You do not need more than 4-5" WC pressure on the input side of the demand regulator. The output side of the demand regulator runs at a slight negative pressure created by the vacuum signal from the carb. I usually use the smallest throat dia. carbs I can find. A 3mm (.100"-.125") throat dia. is usually fine for a multi-cylinder 1" bore engine for variable speed operation without using a restrictor plate. A restrictor plate is needed only when the carb is too large to pull an adequate vaccum signal on its own. Most slow and medium speed model engines (liquid or gaseous fueled) have carbs that are much too large. Smaller is most always better.
One more thing on RC carbs. Do not use an air bleed type when using LP gas. Find one that is self compensating. On this type carb, the gap between the needle and seat should open more as the throttle is opened, and vice versa. This type carb maintains a reasonably steady fuel-air ratio when opening or closing the throttle, even on LP gas. Otherwise, the needle setting will need to be adjusted any time the throttle setting is changed (even slightly changed).
Also, always build-in a priming button on your demand regulator to allow gas to flow at pressure to the carb. I believe Jerry's regulator design has the priming button. Call it a choke or whatever, it really helps in starting your engines. Once you learn to use it, your engines will start very easily.
Jeff
