Webster Carby

[simister]

I am sourcing the parts for the Webster engine. I am having trouble finding the O.S. .12 carby that is specified.

Can anyone suggest a carby that would be suitable to use with the Webster?


Regards John


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[Cogsy]

Bmac2 recently built a Webster and recomends Chuck Fellows carby as super easy to make and well suited to the Webster. You can find the plans at

Updated, Simple Carburetor Design


There's only three parts to make I'm told.

Edit - not sure why my link morphed into that, but the address is
homemodelenginemachinist.com/downloads/updated-simple-carburetor-design-295.html

 

[bmac2]

Hi Simister.
Cogsy is spot on. I’d never built a carb before (please see September model of the month woohoo1) and felt a little intimidated particularly looking at drilling the jet. Then I noticed the “Alternative way to make jet tube”. It makes the trickiest part of the carb a matter drilling a 1/16 hole and soft soldering (I used rosin core) a piece of 1/16 brass tubing.

Don’t stress out much about the materials. I did a lot of reading before I built my version and just about anything goes. Cast iron rings, viton O rings, and one I saw with no rings. For the cylinders everything from cast iron to brass. The only things I kept to the original was the manifold/valve layout, timing gears (sort of), the piston and the length of the stroke.
The Webster design is a great little engine and I learned a ton. Please post a build. It doesn’t have to be fancy or turn into an epic novel but I for one would love to see a couple of pictures as it progresses. A build log is also a great vehicle to get advice along the way. Thm:

Well it’s +1c outside, scaring hell out of 11 o’clock and I have to go to work tomorrow so I’m going to go see if my wife has warmed up my side of the bed. :-\

 

[simister]

Thanks guys for your suggestions. I will certainly have a look at the carby plans. I will post the progress of the build on the forum when I get started. I am about to finish a Stuart engine that I have been building for some months.

I am looking forward to starting the Webster as it will be my first IC engine.




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[simister]

I have not decided to buy or build as yet. What is the max size of the bore / Venturi?. I see that the plans call for about 4.5 mm bore. Carburettors of this small diameter are hard to come by.

I see that Brian used a Traxxas pro.15 carby that has a 6 mm bore.

As far as I can see the most important specs are.

Twin needle,
Around 4.5 mm bore
8 mm engine fitting.

Are there any more important specs that I have missed and how much leeway do I have on the above specs.

John


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[bmac2]

Hi John
When I first got my Webster running I had put a Tarno Carburetor from a Cox .049 (only thing I had) and though it ran, the needle valve only had about 1/8 of a turn between too rich and too lean. The bore on the Tarno Carburetor is .185” (4.6mm). It was pointed out to me that even a little .049 is a lot thirstier (18.000 rpm) that a Webster.
“Jens Eirik (Mechanicboy)
The fuel in Cox engine and other glowplug engines is running on methanol while your engine is running on gasoline with difference fuel amount. It is methanol who is a poor energy (low calories in methanol, about 5000 calories against gasoline who has about 10 000 calories) and need more fuel to run the engine.”
Brian Rupnow has a couple of videos posted comparing the Traxxas Pro-15 carb and the Chuck Fellows carb on his Webster.
http://www.homemodelenginemachinist.com/showthread.php?p=245053&highlight=Chuck+Fellows#po st245053

 

[Cogsy]

When I built my Rupnow hit and miss I initially got it running quite well on the carby off a 0.46 RC airplane glow engine. The needle wasn't too fiddly and performance was good. This carby is quite a bit bigger than the one designed for it but it was usable, so I imagine you have a bit of leeway in carby size.

 

[mattty]

Hi Simister, i am also building the Webster, I see you are also from Aust, have you purchased your gears yet, if so where from?
Also i have made my cylinder from mild steel, do you see this as being an issue?
Thanks Matt

 

[simister]

Thanks guys for your input. I will read Brian's comparison with the two carbs with interest.


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[simister]

I touched the screen on my ipad and the post went before I finished - annoying.

The smaller carbys are not that easy to find. I have plenty of time before I get to the carby stage. I will read Brian's comparison in Chucks carby and the pro-15 with interest. I want to stay as close to specs as possible so that if I run into starting problems there will be less variables to consider.

What is the best fuel to run?




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[simister]

Hi Simister, i am also building the Webster, I see you are also from Aust, have you purchased your gears yet, if so where from?
Also i have made my cylinder from mild steel, do you see this as being an issue?
Thanks Matt

Hi Matt,

Interesting you are from Australia - whereabouts?

Yes, I have purchased the gears from Stock Drive products in the US. I received them in about 10 days. You can buy them in Brisbane but they are more expensive. The Brisbane supplier also get them from Stock drive.

I have not started yet, as I am just completing a Stuart Engine. I am doing all the reading, research and sourcing of all the parts first.

I intend building the cylinder in 12L14 bright steel

Have you got the condenser and points as yet?

John



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[Brian Rupnow]

I am a big fan of Chucks carburetor for the Webster. Chucks old carburetor plans are an excellent choice for the Webster.---Brian

 

[simister]

Thanks Brian, I will have a look at Chucks plans. I see you are saying the old plans.

Is there 2 versions?

John


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[simister]

Can someone give me a link to Chuck's old carby plans please?

John


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[simister]

I have found the link. I missed it in a previous post

John


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[Rustkolector]

John,
I, and a few other builders, have become fans of a very small (and I do mean tiny) RC type carburetor that Roy Sholl of S/S Engineering is currently marketing. They don't show on his website (that least that I can find), but I think it is the only carb he currently sells. So far, I have it running .9 to 1.060" bore engines very well on camp fuel. It is a self compensating type carb that does not use an air bleed. I don't have a photo of just the carb, but it does show in the first photo of a HMEM post on I did some time ago. See link below. This engine runs nicely from 400 to 800+ RPM on this carb using either camp fuel or propane.

Jeff

http://www.homemodelenginemachinist.com/showthread.php?t=22238&highlight=titan+engine

 

[simister]

Thank Jeff,

I will take a look. The smaller carbys are not that easy to find.

John