Author Topic: Rupnow Overhead Cam-Air Cooled  (Read 35383 times)

Offline Brian Rupnow

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Rupnow Overhead Cam-Air Cooled
« on: January 25, 2017, 06:02:12 PM »
This morning I'm setting around with some free time, and I've been thinking for a while now about an overhead cam air cooled engine. There are a lot of horizontal and vertical cylinder engines out there, but I haven't seen very many single cylinder engines like the old "Iron Horse" washing machine engines with the cylinder on a 45 degree angle. My thoughts of course, were that if you could hang the entire camshaft off the cylinder head, then it would give you the freedom to run the cylinder on just about any angle you wanted. By using a cogged belt drive to the camshaft instead of a gear train, that opens up even more freedom with placement of components. I looked through all of the engines I have built over the past few years, and ended up leaning heavily on my Atkinson for some of this, so if it looks a bit familiar, then that is why. I'm not saying I'll actually build this, but you know how it is------Brian

Offline bruedney

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #1 on: January 25, 2017, 06:07:23 PM »
 :popcorn:
‘Results! Why man, I have gotten a lot of results. I know several thousand things that won’t work.’ — Thomas Alva Edison

Offline gerritv

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #2 on: January 25, 2017, 06:13:25 PM »
Very interesting design. Looks ripe for lots of embellishments as well.

Gerrit
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Online crueby

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #3 on: January 25, 2017, 06:51:04 PM »
Looks like it would be modular enough to make a multi cylinder version at different angles too...


 :popcorn:

Online Roger B

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #4 on: January 25, 2017, 07:27:26 PM »
Yet another interesting build  :ThumbsUp:  :ThumbsUp:  :wine1:
Best regards

Roger

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #5 on: January 25, 2017, 09:56:57 PM »
Well----At this point in time it looks Ahhh---Interesting!! I've been waiting most of the day for a call back from a customer, and while I wait I can "doodle". As shown, it has a 1" bore, a 1 1/8" stroke, and that is a 5 1/8" flywheel setting on there. The crankshaft is 3/8" and runs on two sealed ball bearings at each end. The crankshaft is a two piece unit. The "driver" end which supports the flywheel and has the rod journal  on it is one pressed together assembly, the other part of the crank is a "follower crank" and will ultimately drive a cogged pulley and the ignition points. The cogged pulley shown on the cam shaft is only about half the diameter it will end up being in reality.--There may even be a way to incorporate fan blades into the camshaft pulley to blow a stream of cooling air over the cylinder.

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #6 on: January 25, 2017, 10:25:18 PM »
The only bearings that will need lubrication in the engine itself are the con rod big end and the wrist pin. The con rod big end is very easily accessible for a squirt of lubricating oil from my trusty oil can. The wrist pin, however, is hard to get at to oil. Since this is a 1" diameter piston, I am going to try and find room in the small end of the connecting rod for a sealed ball bearing. I won't do that at the big end because it throws the crankshaft too out of balance.

Offline Ian S C

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #7 on: January 26, 2017, 09:53:19 AM »
Brian, you might be able to use a needle roller in the little end bearing, I noted on the last chain saw I stripped that it had one. This looks like an interesting motor.
Ian S C

Offline gbritnell

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #8 on: January 26, 2017, 11:42:09 AM »
Brian,
Here's a thought while you're still in the planning stages. To reduce the size of the sprocket on the camshaft (twice the crankshaft sprocket diameter) use a set of gears down low to get your reduction then you can make the pulleys the same size and smaller. To reduce the height of the cam over the valves make a cap with a recess in it to hold a hardened shim. This way the cam will have a hardened surface to ride on and it will substantially reduce the overall height. The shims can't come out because the recess is deeper than whatever clearance you use. This is how some motorcycle engines are built.
gbritnell
« Last Edit: January 26, 2017, 11:46:28 AM by gbritnell »
Talent unshared is talent wasted.

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #9 on: January 26, 2017, 04:32:15 PM »
I was able to shorten up the blue towers considerably, by getting rid of the pellet shaped pushrods completely and letting the cams push right on the end of the hardened yellow caps. These yellow caps are closed on the end that contacts the cap, and open on the other end to contain the valve spring and for a pinned connection to the end of the valves. The transparent bar guides them and keeps the cam from putting any side load on the valve stem. I thought about how to tie the two sideplates together and decided that a piece of 3/8" thick aluminum angle would be just the ticket. It provides rigidity to the sideplates, and also acts as a great containment for any oil slung off the big end of the con rod. I will mill a recess for a polished brass cover plate which has super magnets embedded into the underside of it, and put some ferrous plugs in the aluminum side plates for the magnets to stick to. this allows me to remove the cover plate, give the big end of the rod a squirt of lubricating oil, then put the cover plate back into place. I am not a fan of oil filled crank cases.



Offline 10KPete

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #10 on: January 26, 2017, 05:36:29 PM »
Interesting design so far!! I'm following.. :popcorn:

The cam followers don't need to be pinned to the valves. They'll stay in place, trapped between the valve and the cam.

Pete
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Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #11 on: January 27, 2017, 01:14:20 AM »
Pete--On one of the forums I visit, somebody has just completed a build of an overhead cam engine designed by Jan of the Netherlands. It worked very well, and had absolutely gigantic towers supporting the overhead cam. This got me thinking about how you could accomplish the same thing with smaller towers, which lead to this design with the towers supported off the cylinder head.--Then, after designing the cylinder head and cam support towers, I had to design some kind of engine to go with it. I get these ideas chasing around in my head, and I can't rest until I set down at the computer to see what they would look like.---Brian

Offline 10KPete

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #12 on: January 27, 2017, 02:32:45 AM »
I can really relate to that, Brian. My brain gets going sometimes and just won't let go!! But I love the results...always interesting stuff.

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Brian Rupnow

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #13 on: January 27, 2017, 06:59:52 PM »
So---The plot thickens---a little bit. I see that with an adapter, I can mount one of my Traxxas carburetors. I could build my own carburetor, but why make more work? I hunted around on my old Atkinson engine thread from back in 2012 and found the name of the company I bought the timing belt and pulleys from. This time I need two pulleys, one exactly twice as big as the other for my 2:1 ratio, and since I now know what my center to center of pulleys are, I was able to call the company in North Carolina that supplied the pulleys 5 years ago and ask for price, delivery, and 3D solid models of the pulleys. I added an exhaust "muffler" and manifold to the engine. (I may rethink the shape of that exhaust manifold, I'm not sure yet). It doesn't show in the model, but I have rejigged those magenta coloured bearing housings to set in tighter to the engine sideplates. The timing belt pulleys on the engine are not updated yet.--I have to get the new 3d models before I can do that.

Offline Admiral_dk

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Re: Rupnow Overhead Cam-Air Cooled
« Reply #14 on: January 27, 2017, 09:50:05 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


 

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