Author Topic: Rupnow Overhead Cam-Air Cooled  (Read 35381 times)

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #15 on: January 27, 2017, 10:35:35 PM »
Sorry for intruding Brian - but to me this has a similarity with old Honda and Airmacchi engines and then the exhaust should be leaving the cylinderhead on the downward side (opposite to where you placed it) and the carb should be where you placed the exhaust .... this would also be the most pleasing look to my eyes ...  ;)

Best wishes

Per
Admiral--There is a great deal of merit to what you say. Since I run a bit of 2 cycle oil with my fuel, the exhaust from these little engines is  nasty, and will coat everything below and in line with the exhaust pipe. If I make the switch you suggest, then my exhaust pipe can be long enough to extend out past the flywheel and keep everything cleaner.---Brian

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #16 on: January 27, 2017, 10:35:46 PM »
I was wondering about where to put the ignition points. Once again the beauty of a single cylinder engine being able to run a "waste spark" system has saved me. I can fit them on the side opposite to the flywheel and run them off the crankshaft. Although the top timing belt pulley up at the cam is going to be twice as large as the diameter shown, the small pulley down at the crankshaft is going to stay very close to what is currently shown.

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #17 on: January 27, 2017, 10:51:29 PM »
Admiral_dk--as per your suggestion, I have swapped the position of the exhaust pipe and the carburetor. I don't know yet if I will leave that strange little intake manifold in place, or remove it completely and let the carb stick out at 90 degrees from the cylinder. That might look good with a really well shaped air intake horn.

Offline 10KPete

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #18 on: January 27, 2017, 11:57:38 PM »
Now it's looking like an engine!!   :whoohoo:

 :popcorn: :popcorn:

Pete
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SB 10K lathe, Benchmaster mill. And stuff.

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #19 on: January 28, 2017, 02:46:06 PM »
I had to move the cylinder intake port around again, as there was no way to get a gas tank mounted with the previous configuration. This will work out pretty good, I think. The exhaust pipe discharges out between the timing belt drive, and the carburetor sucks in fresh air from the flywheel side. I had to make my "crank-case access hatch" a bit smaller as the gas tank covered the top portion of it, but I still have lots of room to get in there with a squirt can. I am going to have to rethink  the use of a ball bearing in the small end of the con rod. A 3/16" i.d. ball bearing is 1/2" o.d. and there simply isn't enough room for it.--And nobody sells a 3/16" sealed roller bearing.

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #20 on: January 28, 2017, 07:25:24 PM »
A big THANK YOU shout out to Luc from Quebec for putting me onto R.C. ball bearings at the hobby shop. I bought two 3/16" i.d. sealed bearings that measure 0.311" outside diameter x exactly 0.125" thick. These two will set side by side in the small end of my 1/4" thick connecting rod. They are part #DTXC1413, and cost $2.49 each. Yes, I do realize that ball bearings are not recommended for something like a wrist pin, which only oscillates back and forth, but doesn't spin fully around. However, they have to be better than a bushing with no lubrication at all. Time will tell about that one.  I also bought four 1/4" sealed flanged ball bearings that are 0.421" diameter over the flange, 0.375" over the other diameter, and have a total thickness of 0.125". Each camshaft support tower will receive two of those. They are part #DTXC1517 and cost $3.99 each. This means that the only bearing surface on this entire engine that doesn't have a ball bearing will be the big end of the con-rod, which will probably get an oilite sintered bronze bushing, and will be easily accessible for oiling by removing the magnetic "inspection hatch" cover.
« Last Edit: January 28, 2017, 07:45:48 PM by Brian Rupnow »

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #21 on: January 29, 2017, 10:12:23 PM »
I keep moving things around, looking for the "ideal" configuration. I got my information today on that 60 tooth pulley that goes on the cam shaft, and it's big enough in diameter that my exhaust pipe was going to run thru the side of it. I messed around a bit having the exhaust come out of the cylinder and point straight up, but that not only looked a bit dumb, but would have covered the entire engine in oil spatter after five minutes of running. Then I had a new thought and turned the cylinder head around 180 degrees on the cylinder. I like that!! I can still have the carburetor where it was before, and have the exhaust pipe pointing down and away from everything.

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #22 on: January 31, 2017, 05:42:13 PM »
Why yes, I DO have a rotary table!!!--And sometimes I do use it for making something other than gears. I have turned the crank on this one so many times this morning that I'm thinking of changing my name to "Crankenstein". If I don't manage to screw this up before I get finished, it is going to make a very pretty little cylinder head.

Offline Roger B

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #23 on: January 31, 2017, 06:54:22 PM »
The design is coming together nicely  :ThumbsUp:  :ThumbsUp: Can you reduce the size of the camshaft pulley? It seems somewhat overpowering.
Best regards

Roger

Offline Tennessee Whiskey

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #24 on: January 31, 2017, 07:16:21 PM »
So I guess we can assume that the "original design concept " is going to be a build  :stir:

Cletus

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #25 on: January 31, 2017, 09:25:43 PM »
When I first looked at the cylinder head detail, I immediately had a big whine and thought "Oh, but this is going to be so hard.---Wahhhhh". Then I thought "Yes, but I've designed similar "hard to make" parts over the last fifty years, and never gave a second thought for the poor guy in the machine shop who actually had to build the parts. So, since I liked the design, I went ahead and made it to the drawing. Lots of work and multiple set-ups there, but I like the finished part. And every part like this that I make stretches my abilities just that little bit more.---I did change the timing belt pulleys.--went from 30 tooth and 60 tooth down to 20 tooth and 40 tooth. Proportions look a lot better now.


Offline 10KPete

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #26 on: January 31, 2017, 09:32:27 PM »
I like this engine, and just need to keep the popcorn locker filled. :popcorn:

Changing the cogwheel sizes really helped!!!

 :cheers:

Pete
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Offline cfellows

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #27 on: February 01, 2017, 03:01:27 AM »
My engines spend most of their time on the shelf where I can look at them and (lately) I've come to realize that well-executed, elegant design is worth the extra effort.

Chuck
So many projects, so little time...

Offline Art K

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #28 on: February 01, 2017, 12:42:25 PM »
Brian,
I've been following along silently. Not that looks are everything but the design looks better w/o the ginormous cam sprocket. Just my 2 cents worth. :)
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #29 on: February 01, 2017, 01:52:53 PM »
Chuck--I'm glad to hear from you. I don't see you on the forums as much now as I used to, and hoped that you were okay. Art and Pete, thank you for your comments. It is nice to know that people are looking at my posts.---Brian

 

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