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Holy Cow!!! Information overload. Its not so much a matter of not knowing where to buy a carburetor, as not knowing what carburetor to buy. Jeez---There are a hundred different carbs available, and they are all different. I did manage to get my brass exhaust pipe finished today. I was just heading out to the garage with the exhaust pipe and the bottom valve housing in one hand, and the silver solder and flux in the other, when the engine Gods whispered to me that "Hey---the valve guide is loctited into that housing!!!" Silver soldering it would have really messed up my day, do I loctited the exhaust pipe in place too. I have the gears on order, and I have the grease and oil cups on order, so I guess I will look at the fuel tank next.
 
Brian Rupnow said:
Holy Cow!!! Information overload. Its not so much a matter of not knowing where to buy a carburetor, as not knowing what carburetor to buy. Jeez---There are a hundred different carbs available, and they are all different. ...
Click to expand...

You got that right, Brian. Very confusing. And most of them are designed to run on Nitro, not gasoline or Coleman Fuel. And they are designed for high speed, 2 stroke engines. Would they even work on a Webster???

Longboy, what does the .15 signify on all these carburetors? Also, any idea what the venturi bore on them would be?

Edit... I see the first Traxxas has a bore of 6mm, almost 1/4". Do you think there is anything smaller?

Chuck
 
cfellows said:
You got that right, Brian. Very confusing. And most of them are designed to run on Nitro, not gasoline or Coleman Fuel. And they are designed for high speed, 2 stroke engines. Would they even work on a Webster???

Longboy, what does the .15 signify on all these carburetors? Also, any idea what the venturi bore on them would be?

Edit... I see the first Traxxas has a bore of 6mm, almost 1/4". Do you think there is anything smaller?

Chuck
Click to expand...

I used an old Perry carb on my Webster. It was originally off of a .61 cubic inch engine. The .15 refers to a .15 cubic inch engine. An old OS .10 to .19 carb should work well.

Charlie
 
cfellows said:
You got that right, Brian. Very confusing. And most of them are designed to run on Nitro, not gasoline or Coleman Fuel. And they are designed for high speed, 2 stroke engines. Would they even work on a Webster???

Longboy, what does the .15 signify on all these carburetors? Also, any idea what the venturi bore on them would be?

Edit... I see the first Traxxas has a bore of 6mm, almost 1/4". Do you think there is anything smaller?

Chuck
Click to expand...
Like Charlie said the fractional number of the carb refers to engine size. Its working fine on My Webster. It only uses about 1/3 of throttle travel from idle to 3000 RPM. A good experiment would be to get some Ace Hardware Denatured Alky or some methanol from the drag strip and see if this carb would needle out enough to use this fuel. As for smaller carbs the answer is a definite maby. Smaller carbs would likly be part of the crankcase casting with an intergrated needle. I wouldn't get lost on their venturi diameters but on something like your low RPM Henry Ford this 6mm Traxxis would be more ideal with greater range of throttle movement if it is a smaller size than my .15 carb. Maby ask Gbritnell for his insight!
Brian Rupnow said:
.............when the engine Gods whispered to me that "Hey---the valve guide is loctited into that housing!!!" Silver soldering it would have really messed up my day, do I loctited the exhaust pipe in place too...........
Click to expand...
I epoxied the exhaust pipe and valve guides to valve bock. Exhaust seal has not failed in the heated environment.
 
IronHorse said:
I was at Pinnacle Hobby store in Markham last week and I saw they sell all kinds of R/C carbs starting at $20. I am sure there are some R/C hobby stores up in your area.


IronHorse
Click to expand...

Iron Horse---I was in Toronto today on business. I drove out to Pinacle in Markham. They do NOT stock any carburetors. They have parts for a wide array of carbs, but no complete carbs at all, and never have had. They will order them for you, if you appear in person and have your credit card with you, but will not take orders by credit card over the phone.
 
According to my math, the Webster displaces 0.75 cubic inches. Thats a 7/8" bore and a 1.25" stroke. And for those of us who work in cubic centimeters, thats about 12.3cc The Traxxis .15 carb refers to the engine size this carburetor is intended to be used on. I am assuming thats .15 cubic inches, but I'm not sure. At any rate, there seems to be a large disparity between .15 and .75 cubic inch engine displacement. I tried to talk to the owner at Pinacle about my engine, but got the distinct impression that although he could order any carb matched to any specific "kit", he was even more lost than I am about a carb size for a home built engine.
 
Brian,
You are correct .15ci engine. I would go to Tower recomended earlier. Whole carbs in every size. Search OS carb

Tony
 
That's funny about Pinnacle, I was in line waiting to pay for some brass stock and the guy behind me had a carb in his hand. I asked where he got it and he pointed to a rack on the wall. I asked the salesman about them and he said there are many available $20 and up.

Oh well
IronHorse
 
Tony---Thanks. I'm not questioning your credentials in any way.-(I seen your post in the other carburetor thread.) However--If thats the perfect 0.75" carburetor, why are people like Longboy getting what appears to be really good results with a carb intended for a 0.15 cu. inch displacement engine? And why do I keep seeing references made to "small venturi" as in 0.25" diameter barrels. This is all making me moderately crazy!!! The model aeroplane engines are all running nitro/methane blends with lubricating oil in the fuel, and they are all two strokes. The webster, by comparison is a 4 stroke engine running Coleman lantern fuel (I expect Naptha.) with external lubrication, and revving at much lower speeds. Damn---So many choices----Brian
 
Hi Brian,
Maybe due to the slower rpm. I left more locations of carbs. Perry carbs are good and inexpensive.

My Coles small h/m justs has 1 bore x 1.25 stroke 4cyc. Carb is a 1/4 bore in a 5/16 hex stock needle and seat. It runs pretty good. Well at least I think.

Good luck with your decision

Tony
 
After much indecision and tooth gnashing, I went back and reread the instuctions provided by the man who designed the Webster engine. He provides plans for a simple carburetor, then tells everyone to "Not even bother" building it. He recomends a small bore carburetor for a .12 to .15 cubic inch engine, which fits right in with Longboys report of how good that carb size works on his Webster. The intake port size on the Webster valve body is only 3/16" in diameter, so I think it is reasonable to assume that any carb with a barrel larger than that is going to be somewhat redundant. So, today I will order a TRA4033 Traxxas carburetor from a local hobby shop in Barrie. They cost about $40 American. I will post and do a write up on this carb when it shows up here. Thanks to everyone who offered advice and help on this issue.---Brian
 
Brian Rupnow said:
Thanks to everyone who offered advice and help on this issue.---Brian
Click to expand...

...and thanks to you for doing the tooth gnashing and research for the rest of us. :bow:
 
Does anybody know---Does the fuel tank outlet have to set higher than the Traxxas carb for a gravity flow to the carburetor, or will the engine vacuum draw the fuel up to the carburetor. I'm figuring out a fuel tank, and would like to know.----Brian
 
Brian,
Even though that's a car carb, it's pretty much the same as an airplane one. Standard practice in unpressurized systems is to set the top of the tank level with the needle valve of the carb.

Higher = when you fill up you'll drip fuel from the carb.

Lower = hard start and inconsistent runs

This is the way it has been done since the 1920's in model aircraft.
I know this from reading my dad's model airplane magazines from that time as a kid
(sure wish I still had them to thumb throuh now and again)

Tony
 
I'm not certain if this answers your question to its fullest extent but in my experience of RC planes building, the center line of the fuel tank was placed as close as possible in-line with the carburetor spraybar (needle valve) for proper operation and as close as physically possible as well. Most of the tanks were pressurized from a tap taken from the muffler to supply a positive pressure to the system. This was not 100% pressure but merely bypass, enough to pressurize the tank during operation. If the tank were placed too low there was a good chance the venturi vacuum would not be enough to draw fuel out of the tank. If the tank were set too high, fuel would be gravity feed into the carb for the duration of time until the fuel level dropped down far enough to correct the problem. This condition would also cause erratic mixture adjustments during flight. I would recommend a tank installed either with the center of the tank in-line with the needle valve or just slightly lower Good luck Brian, and I look forward to seeing your Webster run.

BC1
Jim
 
Brian Rupnow said:
Does anybody know---Does the fuel tank outlet have to set higher than the Traxxas carb for a gravity flow to the carburetor, or will the engine vacuum draw the fuel up to the carburetor. I'm figuring out a fuel tank, and would like to know.----Brian
Click to expand...

The plans (Sheet 20, under "Starting and Running") say:

I have a 1 oz. fuel tank set so that
the fuel level when full is about 1/4" lower than the needle valve.
 
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