Plumbing Parts Engine

[Swarf Rat]

A very interesting engine. I especially like your changes to the original design.

 

[cfellows]

Can't quite put this project to bed. The problem I'm having is that engine is eight-stroking. It doesn't fire every other revolution like it should, but rather every 4th revolution, which means it's missing. I know that at low RPM's, the engine must be running too lean because if I trying mixing any air into the line, it won't run. Unfortunately, I don't have any immediate way to make it run richer. The next step might be a copy of the carburetor from the plans uploaded by George Britnell.

Anyway, I've made some more changes. I moved the throttle off the manifold and onto the fuel tank. It's the socket head cap screw on top of the brass assembly:

The air / fuel mixture is adjusted with a sleeve next to the fuel tank (pimento jar) lid. Rotating the sleeve covers and uncovers a hole leading into fuel line:

I also replaced the points that were running off the crankshaft with a microswitch that now runs off the exhaust valve cam gear. Now it only fires on the compression stroke instead of every crankshaft revolution. This has eliminated the thumping or banging sound that the engine was making earlier.

Here's the latest video:

[ame=http://www.youtube.com/watch?v=GLzOjL4NIVc]http://www.youtube.com/watch?v=GLzOjL4NIVc[/ame]

 

[Deanofid]

I know it's not quite what you're after, Chuck, but the 'eight stroke' situation actually sounds kind of nice. It pretty much makes nice mechanical noises all 'round.

It's been a little while since you first started writing about the gas vapor fuel tank/carb. I think I remember you mentioning that it ran richer if the air pipe ran down into the fuel? Maybe that would make the mixture a little richer for you?

Dean

 

[ghart3]

I'm like Dean, liking the not firing every time. Not only like the sound but it makes for a cooler running engine with air being pumped through on the wasted cycles.
By the way Chuck, nice engine, I like it. gary

 

[BigBore]

"Can't quite put this project to bed."

I, for one, am ecstatic that this project continues to pi$$ you off motivate you. This is one of those "everything you wanted to know about..." threads. Please keep going.

In my lab, I have a LP Bunsen burner with a sleeve valve that controls the amount of air in the gas mixture. It never adjusts the same way twice. It kept loosening up so I plugged the one hole with Hi-temp RTV. Could you make a smaller hole to start with or a series of very small holes instead of just the one through hole?

Howzabout two of your cool little throttles? One for fuel and one for air? Could they be milled/drilled into one block? Wow, am I a wanna-be or what?

Ed

 

[cfellows]

I decided to post this here so it would be a continuation of the Plumbing Parts engine instead of the thread I started on the model carburetor. I had a full day to myself, so I set out in the shop to build a scaled down version of the carburetor from George Britnell's drawings. Then I took a look at what I had already built and decided, this isn't so different than George's design, maybe I can just make some changes to what I already had.

So, first I had to plug up the bottom of the throttle body hole. I turned a small piece and drilled it with a #29 drill to be tapped later. Here's the carb body and the piece to patch the hole:

Well, that was easy, messy, but easy. Next I needed to turn off the bottom part of the throttle barrel since it would no longer extend all the way through the body.

So far, so good!

Next I needed to tap the new insert so I could thread in the needle valve seat. That's a 5-40 tap to accommodate a 1/8" threaded needle seat.

And here the needle seat is threaded into the bottom of the carb body.

And here it is mounted on the engine.

And here is the video. Runs much better, even though the adjustments are kind of finicky. I'm wondering if the engine would be less finicky if I made a slightly larger version of the carb. This one has a venturi bore of 1/8"

[ame=http://www.youtube.com/watch?v=yEeSkoBMZKg]http://www.youtube.com/watch?v=yEeSkoBMZKg[/ame]

Chuck

 

[putputman]

Chuck, did you also add the bleed hole like George's design shows? You are really fine tuning that engine.

Are you using that new Canon digital camera for your videos? They are really clear at all distances. The sound is good also.

 

[cfellows]

Thanks, Arv.

No, haven't drilled an air bleed hole. So far, I'm controlling speed by just not closing the throttle too far. Then I adjust the mixture. I really like the way it runs and sounds on the carb but the carb is presenting some of its own challenges. I can get it to run the speed I want it to, but am having problems getting it to run consistently. Also a lot harder to start with the carb than it was on just the vapor fuel tank. I think I'm going to try boring the venturi hole out from 1/8" out to 5/32" and see how that works. My goal is just to get it to start reliably and run at a medium idle.

Oh, and yes, all the pictures have been taken with the Canon SD780. By the way, these pictures are cropped then reduced to about 25% of the original size. Love that camera!

Chuck

 

[kpate]

Chuck,

The carb looks real good and I'm liking the experimentation that you're doing with this engine. :bow:

 

[Chaffe]

Amazing, just read this thread from start to finish. Im looking forward to doing something similar when i clear my feet of a few excisting projects! I too have a draw of half finished engines lol!

 

[bearcar1]

Chuck, I salute you!! I have followed along on your building of this fine example of model engineering from day one and have truly enjoyed the journey. I marvel at how you attack a certain problem and address it in logical steps and then are able to present your tribulations and successes in a concise understandable manner. BRAVO!! If the day ever arrives that I feel compelled to build one of these engines, yours will be the one that will be used as a benchmark. Terrific work, and thank you for sharing all of it with us.
:bow:
BC1
Jim

 

[cfellows]

Thanks for the kinds words. The nice thing about an engine design like this is that it's pretty modular and allows for experimenting with different parts without rebuilding the whole thing. I've had two nagging problems with this engine that I've never resolved to my satisfaction. One minor problem is the fact that the S&S ignition module fires on both the make and break of the points. That may not hurt anything, but I've always had the suspicion that the engine is sometimes firing off-cycle, if that's even possible.

The other problem is the difficulty of getting the engine to run without misfiring at low RPM's, like 400 RPM. I've not found a satisfactory carburetor for very low speed running. Maybe it's just the nature of real small bore engines.

Chuck

 

[gbritnell]

Hi Chuck,
Boy I really like your engine. It sure runs nice. As far as the carb I wouldn't make the venturi any larger in fact if I was going to do anything I would make it a little smaller. With a slower running engine the velocity through the carb isn't as great as an engine that runs higher up in the rpm range so by going smaller you increase the velocity so therefore you get a better vacuum signal for the fuel.
The purpose of the air bleed on these throttling carbs is to prevent the richness at idle speeds. You can adjust the needle to compensate but then when you open the throttle you also have to open the needle a little to match the air volume.
George

 

[drallen]

Hi Chuck
I have been reading this thread regarding the plumbing parts engine. Congratulations. I noticed you are using Flex hone. I have used these myself. For anyone wanting them they are also available from KBC tool at www.kbctools.com.
Dave

 

[flyingtractors1]

Hi Chuck. I just stumbled on to this thread and found it incredibly interesting and informative. Nice engine. Great build - wonderful naratives and pictures. It is work such as this that makes this Forum so valuable, motivational and inspiring. Many Thanks to you and to others who shared wisdom here. Ralph

 

[doc1955]

Chuck
It's sounding pretty good! Nice job I sure like the looks of that engine! She sure revvs up nice!

 

[cfellows]

Thanks, guys. That's still one of my favorite engines. I keep thinking I might convert it to a hot bulb engine one day.

Chuck

 

[Ken I]

Chuck, what a wonderful engine with so many creative features providing plenty of food for thought.
This thread was basically finished before I joined the forum and for whatever reason, I have not seen it before - read it from end to end - quite a ride.

Regards,
Ken

 

[AussieJimG]

Thanks for the journey Chuck, I admired your engine when I saw it on YouTube and then stumbled upon this posting. Once I started reading, I couldn't stop.

Seeing you change direction and backtrack on some of the design gives me heart. Now I know that the experts do it too, I feel much better.

Merry Xmas and keep up the good work.

Jim

 

[lazylathe]

Hi Chuck,

I was wondering what had happened with this build of yours!
Found out I missed the end by a few months....

Amazing work as usual and a very distinctive sound!!
Great work as usual and yet another totally unique creation from your workshop!!!

Andrew