Author Topic: Brian Rupnow Modification to my simple carburetor design  (Read 9650 times)

Online Brian Rupnow

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #15 on: December 29, 2014, 11:28:27 PM »
This video shows the operation of the throttle made as per the drawing posted at the beginning of this thread.

Offline cfellows

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #16 on: December 30, 2014, 05:26:28 AM »
Nice mod, Brian.  That seems to operate really smoothly.

Chuck
So many projects, so little time...

Online Brian Rupnow

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #17 on: January 03, 2015, 07:53:06 PM »
I haven't ran off and abandoned this project. As Jason pointed out, vibration from the engine makes the throttle handle rotate to it's lowest point of gravity. I have a very simple fix for that. The #6-32 thread that holds the small screw which interacts with the diagonal slot in the throttle shaft is currently through only one side of the carburetor body. I am going to make it go all the way through, and insert a nylon #6-32 set screw on the side opposite the throttle shaft. That way I can put whatever pre-load I want on the throttle shaft to make it hold it's position, and since the screw is made of nylon it will hold it's position and not back off. I have ordered some screws from my local fastener company, and I am waiting for them to come in.---Brian

Offline GordonL

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #18 on: January 04, 2015, 09:35:53 PM »
I hope you come up withe the perfect carburetor soon. Carburetors have always been a problem on my  small engines. I have tried several different designs over the years and this seems to be ideal. Every time I get a new carburetor built you improve it and I build the new one and it is better so I think I will build one for this other engine and then another engine etc. If I keep building improved carburetors I may never get around to building a new engine.  :lolb: :Lol:

This latest is the best yet. Thanks a lot guys.

Offline Roger B

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #19 on: January 07, 2015, 11:36:17 AM »
I hope you come up withe the perfect carburetor soon. Carburetors have always been a problem on my  small engines. I have tried several different designs over the years and this seems to be ideal. Every time I get a new carburetor built you improve it and I build the new one and it is better so I think I will build one for this other engine and then another engine etc. If I keep building improved carburetors I may never get around to building a new engine.  :lolb: :Lol:

This latest is the best yet. Thanks a lot guys.

I agree completely  :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Online Brian Rupnow

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #20 on: January 13, 2015, 01:37:32 AM »
A brief return to an "ongoing" project.--This is the perfect solution to a throttle shaft that won't hold it's position. A nylon "set screw". You can put whatever amount of pre-load you want on the shaft, and that's all you have to do. It won't gall the shaft, and it won't vibrate loose nor fall out. Sooner or later, I will have this carburetor up on an engine to see how well it works.---Brian

Online Brian Rupnow

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #21 on: January 15, 2015, 09:13:28 PM »
We're getting closer!!  I want to try out my modification to Chuck Fellows carburetor, and needed to build a gas tank to use the Webster engine. (I had stolen the gas tank off it about 4 engine builds ago.) I never built a tank this shape before, but it is easier than the style I have always built before. Maybe tomorrow I'll get it to run.

Offline philjoe5

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #22 on: January 15, 2015, 09:25:13 PM »
Good luck with it Brian :popcorn:

Cheers,
Phil
If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man.  - Mark Twain

Online Brian Rupnow

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #23 on: January 16, 2015, 01:28:02 AM »
I had to do it!!--I simply couldn't restrain myself!! I'm tired---it's 40 below out in my main garage--I couldn't find the damn starter spud and had to make a new one---But---Oh, does the Fat Flywheeled Webster ever run sweet with my modified Chuck Fellows carburetor on it!!! The 1/4 turn throttle really does the trick. ---It doesn't run any BETTER than it did with the original Chuck Fellows carb on it, but the throttle handle does indeed work great, from "dead slow" to "wide open" in 1/4 of a turn. I will post a video of it tomorrow morning. Now what you are going to see isn't going to look all that much different from the video I made with the original Chuck Fellows carburetor on it. That is because, when running under no load, the original carburetor will go from "dead slow" to "Frightningly fast" in just slightly more than 1/4 of a turn, using the little handle I made to clamp on the head of the #8-32 shcs throttle. It's only when the engine is running under a load that the difference becomes apparent. On the original version, running under load, the throttle screw has to be rotated about 3 full turns to achieve a "wide open" state, and that is very difficult if you have a "handle" attached to the head of the screw. The new modification achieves the "wide open" state in 1/4 of a turn. This entire enterprise is somewhat like trying to determine how many angels can dance on the head of a pin, but it's fun. Every time I try something new like this and it works, I can almost know what Henry Ford or Thomas Edison must have felt like. ---Video Tomorrow----Brian

Online Brian Rupnow

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #24 on: January 16, 2015, 02:21:09 PM »
This is the Webster engine running the modified Chuck Fellows carburetor on it. It works very well. As I said earlier, I don't think it works any better than it did with the original Chuck Fellows carburetor on it, but the throttle can be fully opened with 1/4 turn of the handle. I will post the original video of when I first tested the original Chuck Fellows carburetor on the same engine on a following post, and you can draw your own conclusions.

Online Brian Rupnow

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #25 on: January 16, 2015, 02:47:43 PM »
Here it is with the original Chuck Fellows carburetor on it.--one confusing part of this video is where I mentioned that Chuck had abandoned this design.-Chuck was trying out this new design carb on a new engine he had built, and a problem somewhere else on the engine had caused him to think it was a carburation issue Story had a happy ending--Chuck sorted out the other issue and decided the carb was okay, but by that time I had already made this video.--One other thing--I checked with my laser tachometer, and the lowest sustainable rpm of the engine in it's current form is 422 rpm.---Brian

Offline cfellows

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Re: Brian Rupnow Modification to my simple carburetor design
« Reply #26 on: January 18, 2015, 05:30:55 AM »
Impressive, Brian, guess I'm going to have to try your modification.  Seems to work really well.

Chuck
So many projects, so little time...