Author Topic: Adding manual clutch to model engine  (Read 1453 times)

Offline Brian Rupnow

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Adding manual clutch to model engine
« on: October 10, 2018, 07:30:41 PM »
A few years ago I had my single cylinder flathead  i.c. engine featured in Home Shop Machinist magazine. It was built by a number of people, and since then has mostly set on a shelf in my office collecting dust. I have been messing around with various styles of manual clutch this last month or so, and have decided to install a manual clutch on the flathead engine. I designed a "line shaft clutch" last year, and in it's final guise as an expanding shoe clutch it worked so well that it has become my favourite style of clutch. I am going to modify the clutch and make it a direct drive from the crankshaft of the engine.

Offline Ye-Ole Steam Dude

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Re: Adding manual clutch to model engine
« Reply #1 on: October 10, 2018, 09:10:08 PM »
Hello Brian,

Neat looking drawing and the clutch should be a good attachment to your motor.

Have a great day,
Thomas

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #2 on: October 10, 2018, 10:57:10 PM »
Hot diggity dog--I made a part today. In fact, I liked it so much that I made it twice. That long extension hanging out of the engine started life as a piece of 1/2" cold rolled, turned to .25" diameter over most of it's length with a 3/8" counterbore in the 1/2" end to slip over the engine crankshaft. Somehow, I managed to read my micrometer wrong and turned the first one to 0.22" diameter. Ah Poop!!! So, into the box of miscellaneous short ends it went, and then got remade. In the picture, you see all the victims. The flathead engine, the line-shaft expanding shoe clutch, and the single part that was successfully made.

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #3 on: October 11, 2018, 10:36:04 PM »
So here we are at about 85 percent--Everything goes round and round with no binding and no clearance problems. I have to trim the clutch shaft to length and drill a hole thru the shaft for a dowel which locks the expanding shoe carrier to the shaft. Also have to drill and tap two places at the sleeve end of the shaft to lock it to the crankshaft. Next step is to clean up the drawings tonight and send them off to someone.


Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #4 on: October 13, 2018, 04:04:48 PM »
So, today we have a video of the clutch in operation. I would call this clutch about 85% effective. The fact that the clutch drum rotates freely on the driven shaft and only revolves under power when the clutch is engaged means that the clutch wants to "creep" a little even when it is fully disengaged. Of course the trick is to find something to drive which has enough resistance to keep the clutch from "creeping" but not so much resistance that it stalls the engine when the clutch is fully engaged. I already have an idea in the back of my head on how to build a "non creep" clutch, and will probably post about it when time allows. The people who bought plans for this clutch will get new free plans for the new "non creep" version after I have built and tested it. The last 20 seconds shows me de-mounting the camera and tripod--I thought the camera was turned off.
« Last Edit: October 13, 2018, 04:08:49 PM by Brian Rupnow »

Offline Ye-Ole Steam Dude

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Re: Adding manual clutch to model engine
« Reply #5 on: October 13, 2018, 05:24:15 PM »
Hello Brian,

Pretty slick.  :ThumbsUp:

Have a great day,
Thomas

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #6 on: October 13, 2018, 06:28:17 PM »
As you seen in the previous video, the clutch performed quite well, but had a tendency to want to "creep" even though the clutch was fully disengaged. This was caused by friction between the rotating clutch shaft and the clutch drum which was supported by it. I have a new design using almost all of the current parts, but arranged a bit differently so that the clutch drum will never see any frictional influence from the rotating clutch shaft.

Offline AlexS

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Re: Adding manual clutch to model engine
« Reply #7 on: October 13, 2018, 09:46:07 PM »
Interesting design Brain! Do you have an section view of the previous clutch system?

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #8 on: October 14, 2018, 12:13:41 AM »
This shows what the previous clutch (this morning) looked like in cross section. The fact that the clutch drum was supported by the rotating shaft made it want to "creep" even when not engaged.

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #9 on: October 14, 2018, 09:48:26 PM »
Today I have spent the entire day reconfiguring the clutch so the drum would not "creep" due to the friction from the rotating shaft which it was riding on. Not a lot of changes to the clutch itself, but had to change the bracket a bit by lengthening the hole that the clutch arm sets in and shortening the shaft. Everything is back together now, and the clutch is performing well, except now the drum wants to creep because of the near proximity of the shoes inside the clutch drum. However, this will get sorted out this week. I have a bit of "real work" starting tomorrow, so will fit my model work in between things.---Brian

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #10 on: October 14, 2018, 10:09:14 PM »
I have my detective/analyst hat on now, and think I have found a clue. The clutch is disengaged in the picture. You can see the hot pink return spring that returns the clutch shoes to their home position when the tapered cone is not forcing them apart to engage the clutch. The green arms which hold the two cap-screws the spring is attached to and the other two dark blue screws that are forced apart by the tapered cone when the clutch is engaged are heavy little devils, and I'm sure that when the engine is turning at around a thousand rpm, they are acting as counterweights. Centrifugal force is making them fly out enough to make the shoes rub on the inside of the clutch drum. When I shut the engine off, the drum spins freely and I don't feel any drag. A stronger spring should fix that, but I've worked enough today. I will get to that later this week.---Brian
« Last Edit: October 16, 2018, 12:14:42 AM by Brian Rupnow »

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #11 on: October 16, 2018, 12:14:24 AM »
I am busy right now with a drop in design order for a welding fixture for a General Motors supplier. As soon as I get the chance I am going to put another spring on the opposite side to the current one and see if that cleans up the problem of "shoe drag".

Offline MJM460

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Re: Adding manual clutch to model engine
« Reply #12 on: October 16, 2018, 01:00:03 AM »
Hi Brian, another interesting build that I have been following from the beginning.

To reduce the centrifugal force due to the cap screws, it might be worth trying replacing the cap screws with grub screws.

It is a rotational system, so mass at a greater radius, like the heads of the cap screws are much more significant than the same mass closer to the axis of rotation.  (Force is proportional to mass times radius squared.)

I don't know if it would be enough, but easily tried.  At least the extra spring should work, though of course it will also increase the centrifugal force required to force the shoes outwards to press on the drum, so again hard to tell.  Again easier to try than calculate.

Looking forward to developments,

MJM460
The more I learn, the more I find that I still have to learn!

Offline Brian Rupnow

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Re: Adding manual clutch to model engine
« Reply #13 on: October 16, 2018, 01:39:47 AM »
MJM460--good thinking. I may replace the dark blue capscrews with set screws. That will take away the mass of the heads.--Brian

Offline crueby

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Re: Adding manual clutch to model engine
« Reply #14 on: October 16, 2018, 01:48:22 AM »
Can the levers be drilled or milled with channels to take out more weight from them?