# Clutch---Again!!!



## Brian Rupnow (Apr 1, 2013)

Earlier this winter I designed and built a clutch, to use between one of my i.c. engines and a model sawmill I designed and built. Unfortunately, although the clutch worked, it had issues with internal binding which robbed a lot of the power, to the extent that my small engines couldn't cope with it. The design you see posted here is the design that I built and had the problems with. I am going for a total redesign, which although it will still be a cone type clutch with a wooden cone, the actuator will be a purchased Destaco type "push-pull" clamp.


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## Brian Rupnow (Apr 2, 2013)

The first clutch I made was made with what I had laying around. This time, I'm getting more serious. I'm actually spending some money. I have bought a Destaco style "push/pull" clamp, and 6 bearings (I may not use them all) from Canadian Bearings, a local supplier. The bearings are single row sealed ball bearings, 1/2" bore x 1 3/8" o.d. x 7/16" wide. Before anyone jumps on my back about using "thrust bearings", keep in mind that the engines this will be used with are micro horsepower. A normal ball bearing is well capable of withstanding any axial thrust loads they will see in the applications I have planned for them. The shaft will be supported at one end only, and the entire design will be more amenable to changing belts on than the previous design. I am still early in the planning stages of this clutch, as you will see by the sketches on the paper under the bearings. I don't recomend that anybody jump right in and start building this with me. I want to finish this one and "field try" it to avoid some glitch showing up "after the fact". I will post pictures and models as this develops, and a video of the field trial" when it is finished. I will also try and address any shortcomings that the previous design had, one of the big issues on the first clutch being the limited size and type of pulley used on it.----Brian


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## Brian Rupnow (Apr 2, 2013)

This is uglier than original sin, but its a start. The pulleys are not shown yet. Neither is the die spring that forces the cone away from the receiver. However, I've been working 3 hours on it and thats enough for tonight.


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## hi speed scrap (Apr 3, 2013)

Hi Brian,
My suggestion is to use an over centre style clutch, such as many
dozers and marine gbx's used.
Advantage being there is no axial load being applied to the mainshaft,
thus reducing to the angular thrust on your ball bearings to zero.
They are easy to make, and not hard to have air operated.
I have some sketches at home of one, but I wont be home for a day
or so.
try googling for a schematic of one.

Dave.


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## Brian Rupnow (Apr 3, 2013)

I like this design better. The Destaco clamp is gone. The base is much shorter. The clamp has been replaced by a cam type lever to engage the clutch, and a die spring mounted internally disengages the clutch. There is enough room to put a 6 1/2" outer diameter pulley on either hub. The belts can be assembled without taking anything apart. There are fewer bearings. the blue center shaft does not rotate. It is a stationary, cantilevered design. All axial forces are transmitted through the bearing balls. 









View attachment ASSEMBLY--CLUTCH-2.PDF


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## Dave Sohlstrom (Apr 3, 2013)

Brian

Are you going to have problems with the spring when clutch is disengaged with relative motion between fixed and moving parts.

Dave


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## Brian Rupnow (Apr 3, 2013)

Dave Sohlstrom said:


> Brian
> 
> Are you going to have problems with the spring when clutch is disengaged with relative motion between fixed and moving parts.
> 
> Dave


If I do this right, The spring will run out of compression after its first .040" of travel. I would hope it shoves the wooden cone back far enough to disengage, and then just lays in there without putting any force against the wooden cone.


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## trumpy81 (Apr 3, 2013)

Brian, I see a number of potential problems with your clutch design. The first one is the limited amount of surface area on the frictional faces of the cones. This would require a good deal of pressure to be placed on those two components in order to get a good drive and that pressure may increase the drag on the bearings causing significant losses in the drive train. Secondly, the spring will cause friction between the driven and non driven components with the clutch disengaged. Although it may be less of a problem, you may find that it is impossible to completely disengage the clutch, IE: some drag will remain between the driven and non driven components.

Have you considered using a multi-plate clutch similar to those found in a modern motorcycle?


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## Brian Rupnow (Apr 3, 2013)

I don't know what a motorcycle multi plate clutch looks like.


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## trumpy81 (Apr 3, 2013)

Brian, here's a link to an exploded view of a motorcycle clutch;
http://www.google.com.au/imgres?img...ZcUdaSKs2ziQfkz4H4DA&ved=0CDUQ9QEwAQ&dur=6296

They are fairly simple devices and there are a number of ways to make one. I could draw up a simplified 3D model of one if you like. What software are you using? Solidworks, Alibre or Inventor?


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## Brian Rupnow (Apr 3, 2013)

Trumpy---Thanks, but thats way too many parts for me.


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## raven007 (Apr 3, 2013)

You could still use the cantilevered shaft, except make it hollow and have a release rod running through. The release rod pushes outward on a spring loaded plate (on the driven side of the clutch preferably to eliminate idle drag) to disengage the clutch.


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## trumpy81 (Apr 3, 2013)

Brian Rupnow said:


> Trumpy---Thanks, but thats way too many parts for me.



Brian, you don't need to use that many plates in the clutch. One or two is all that is necessary for a clutch of the scale you would need.

I'm sure you could simplify it even further without losing it's effectiveness. the main thing to remember is that the friction plate has a much larger contact surface area than your current clutch, and that area is doubled because both sides of the plate are used. It also requires much less pressure in order to get the clutch in the locked up state.

Would it help if I told you that this type of clutch is also used in Top Fuel dragsters?


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## Jordan (Apr 3, 2013)

A multi plate clutch could be compact and still have a large working surface area, but is lots more work and complexity. As I understand it, cone clutches on automobiles were harsh, giving a rather on-off action, so were replaced with flat plate type that gives a smoother take up. But a cone type could be quite suitable for driving a machine tool, and has the advantage of being more compact than a flat plate type. I guess the cone has a wedging action that increases grip.
Some machinery (eg Myford lathes) use a design similar to a drum brake, having cylindrical elements, all metal. Not quite as simple as the axial design of the cone clutch, as the "shoe" needs to be expanded.
Has an all metal clutch been considered? Rather than steel on wood, steel on cast iron may have advantages. Wood burns if overloaded. But being less grippy, for the same size you might need to use a stronger spring.


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## Brian Rupnow (Apr 3, 2013)

Raven007--Thats a great idea. In fact, they are all great ideas. I like it when I get serious feedback from people reading my posts. Today I returned the big Destaco style clamp and used the refunded money to buy some aluminum material to build the clutch outer drums and frame with, and a peice of cold rolled steel for the cam lever. Like the small engines that drive them, the machines which I design don't take a tremendous amount to torque to drive them. The sawmill has turned out to be an exception, but everything is relative. If my small engines are a bit underpowered to run it, then we'll gear things down and run the saw a bit slower. However, it is imperative that I be able to completely stop all power being transmitted to the sawmill without stopping the engine everytime I retract the carriage. The previous clutch design transmitted torque with no problem, but was inclined to bind on the shaft when engaged, and seriously limited the size of pulley that could be used on it. Hopefully this design will get around those issues.---Brian


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## kutzdibutz (Apr 4, 2013)

Hi Brian,

what you also could think of is a drum break style clutch. That way you would also get rid of the axial thrust on the bearings. Could be actuated with a slide/claw thingy. There are also automatic engaging/disengaging designs with the right spring size and pad weight used. (engaging/disengaging at a given RPM)
But I would actually also go for the disk clutch. One or two disks shold be plenty. I designed such a clutch once at university. Only have paper copies left but I could scan them if you like. Was including torque calculation if I remember right...

Cheers, Karsten


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## Brian Rupnow (Apr 4, 2013)

Am I winning or losing?--I'm not sure. I spent today making both the outer aluminum shells, the oak friction cone, and the shaft, and assembled everything. I will make the main aluminum frame that holds everything tomorrow. Based on what I'm seeing so far, there isn't much chance for any binding internally. I think the secret to this clutch is all going to be in the design of the locking cam/lever.--One thing I did find out---The only spring I was able to pick up yesterday that would slide over the 1/2" shaft is too weak. The only thing worse than a clutch that won't engage is a clutch that won't disengage!!!


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## Coilmotorworks (Apr 5, 2013)

I like your work here and think that the latest design will probably do just fine for what you are doing. For your consideration I am posting a good clutch design that would work also for what you are doing. An over center design: An internal shoe clutch similar to what is found on old Rumely Oil Pulls is well suited as it actually has few moving parts and bearings required and the release tension and load pressure can be easily micro adjusted. The clutch can remain open without any input pressure. It also has no load pressure on any bearing once engaged and thus running friction is greatly reduced. Your current design will have quite a bit of friction even with the best ball bearings installed. This type clutch can be built quite small too and still apply good solid engagement. As an example of how small it can be made I am including a picture of one that I built for a 1;12 scale tractor which the clutch OD is the diameter of a quarter. 

CMW


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## Brian Rupnow (Apr 5, 2013)

There it is, all done except for the locking cam/lever. I only used 4 of the bearings I purchased for $7.00 each and about $20 worth of aluminum. Well under $50. If it works as hoped, thats a very cheap stand alone clutch. If it doesn't work, I've had $50 worth of entertainment out of it. Just about every comment posted about it has been correct. I know the bearings will spin freer if I pop the seals out. I know the clutch would probably work better is I used end grain wood. I know that in some respects it is probably way "over designed", but its easier to take a bearing out later than to add another bearing later. With this design, the largest pulley or sprocket or whatever will be bolted to the ring of holes on the hub closest to the vertical stand. It will always be turning as long as the engine is running. My expectations are that a small diameter pulley will be attached to the ring of holes around the outermost "clutched" pulley, on the hub side. In fact, a 3/4" wide flat belt can be run right of the face of the hub on the outermost pulley. The real trick to this thing is going to be in the locking cam/lever.


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## Brian Rupnow (Apr 5, 2013)

Coilmotorworks said:


> My opinion. A good clutch for what you are doing is an over center design: An internal shoe clutch similar to what is found on old Rumely Oil Pulls is well suited as it actually has few moving parts and bearings required and the release tension and load pressure can be mechanically adjusted. The clutch can remain open without any input pressure.


 Coilmotorworks---I don't have too many old "Rumley Oil Pulls" (whatever that is) laying around my garage. However, I do react well to good clear sketches, explaining what you are suggesting.----Brian


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## trumpy81 (Apr 5, 2013)

Brian Rupnow said:


> Coilmotorworks---I don't have too many old "Rumley Oil Pulls" (whatever that is) laying around my garage. However, I do react well to good clear sketches, explaining what you are suggesting.----Brian



Brian, here is a drawing of a multi-plate type clutch for your application. It's actually a single plate clutch but the rest is based on the multi-plate concept.

If you want more details I'd be happy to supply the models etc. for it. 

View attachment Clutch.pdf


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## Brian Rupnow (Apr 5, 2013)

Trumpy---Thank you. Thats a great design. I have stashed it away on my hard drive with my other clutch files.----Brian


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## Brian Rupnow (Apr 6, 2013)

Today we had our first tryout of the new clutch. It looks really good in the movie, but only seconds after the movie was made the clutch started to bind up. I'm not sure why---haven't torn anything down to check yet. If this clutch design doesn't work out, then I'm going to give up on clutches for a while.


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## Brian Rupnow (Apr 6, 2013)

I tore things down and it seems that some Loctite had migrated to where it shouldn't have when I assembled things the last time. After a bit of clean up and reassembly, things appear to be okay. The clutch is up on the lathe again wailing away at 500 RPM. If it does this for half an hour without any more binding, I think its okay. I'll let you know when the half hour is up. Then I will run it for half an hour with one of my air/steam engines to see if there is any binding thats being hidden by the lathe, which is very powerful.


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## Brian Rupnow (Apr 6, 2013)

Barrington---The spring just sets in there between two faces. That is the only constraint imposed on it. Yes, you are correct. This makes the clutch somewhat "uni-directional", depending on whether the spring is wound clockwise or counter clockwise. This second test I curently have underway is turning in the opposite direction, brecause I thought of the same thing you suggested. In the first test, the parts were rotating "against the spring". In this current test, the parts are turning the opposite direction. As for heat causing clearances to change and bind, it shouldn't happen. Everything that turns is supported on sealed ball bearings. The only non bearing  contact is between the clutch cone and its receiver. The cam/lever pushes against the inner race of the outer bearing, but that inner race doesn't turn. The pressure is transferred to the wooden cone thru the balls and the outer race.


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## Brian Rupnow (Apr 6, 2013)

Here we have it after 1/2 an hour at 500 rpm. It still engages and disengages slick as a whistle, and no binding apparent.---I slipped the belt off and turned it by hand to check this. Nothing was hot, nor even warm to the touch. I think Barrington nailed it with his comment about the spring direction.


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## Brian Rupnow (Apr 6, 2013)

Here is a neat little video of the clutch being driven by one of my very earliest steam engines. It seems to take very little power to run this clutch, as can be seen here.


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## Walsheng (Apr 6, 2013)

Brian Rupnow said:


> Barrington---The spring just sets in there between two faces. That is the only constraint imposed on it. Yes, you are correct. This makes the clutch somewhat "uni-directional", depending on whether the spring is wound clockwise or counter clockwise. This second test I curently have underway is turning in the opposite direction, brecause I thought of the same thing you suggested. In the first test, the parts were rotating "against the spring". In this current test, the parts are turning the opposite direction. As for heat causing clearances to change and bind, it shouldn't happen. Everything that turns is supported on sealed ball bearings. The only non bearing  contact is between the clutch cone and its receiver. The cam/lever pushes against the inner race of the outer bearing, but that inner race doesn't turn. The pressure is transferred to the wooden cone thru the balls and the outer race.



So you are saying it works well in both directions?
Because I am thinking of using a steam engine to run a small watchmakers type lathe, just for demo's and shows and things, and I would want a clutch that would work both ways.

John


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## Brian Rupnow (Apr 7, 2013)

Yes---There is a high coefficient of friction between wood and steel, much lower between steel and steel. A hardened washer set in the bottom of the oak cone counterbore would let the spring ride against steel on both ends, with a much lower chance of wanting to "grab" and bind on the end of the spring.


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## Brian Rupnow (Apr 18, 2013)

I haven't run off, and I haven't abandoned this project. Since I last posted, I've had an "Almost Flood", picked up a bunch of design work, and managed to catch some kind of nasty flue----All simultaneously. That, along with machine shop burnout has kept me from adding anythng interesting. I am also having issues with my Odds and Ends engine that I recently completed---something to do with carburation, I believe. I will add more when I'm feeling a bit more human, and have sorted through some of the issues.---Brian


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## aonemarine (Apr 18, 2013)

Hope your feeling better.  I've been in clean up shop mode the past week. Hope to make chips tomorrow.


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## Brian Rupnow (Apr 21, 2013)

I think I'm going to live!!! Felt well enough to play with my clutch design this afternoon. I have come to realize, after playing about with this thing, that I have to have some means of holding the clutch engagement lever in place, other than my thumb.---And it has to be adjustable, to compensate for clutch wear and to adjust the force put on the cone. I'm not sure how well it shows up in the attached .jpg, but the dark blue part has a slot in it for a 1/4" unc bolt, and can be moved in a slot milled in the grey frame member to adjust position. The yellow trigger is spring loaded "up" with a compression spring underneath it. It pivots around the green outer 1/8" dowel, and is restrained from springing completely out by the second 1/8" green dowel that is closer to the grey frame. The bronze colored 1/8" cross shaft thru the yellow trigger is something to push down on to release the clutch engagement lever. I have built the 1/4" thick by 6.75" dia. pulley and bolted it in place.---Haven't drilled all the holes in it yet though.---The 12 holes have no real purpose, but if you don't put them in, its very difficult to see what is rotating and what isn't in a video.


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## canadianhorsepower (Apr 21, 2013)

Hi Brian, 
this is a nice set up you have, I think you should consider one thing
having 1 to 1.5 degree angle different between your friction point and frintion disck

having all the same angle as soon that this wood will get smooth because of clutch slipering it wont work like a used Vbelt when all the sides rub it' slips
by having a different angle you would eliminate this.

now you have a nicely finish pieces of metal polishing wood when they mate
all your friction is gone. other wise you would  would be using that peaces a few thow at the time
hope my french didnt interfer to mutch with my translation


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## Brian Rupnow (Apr 21, 2013)

Luc--the trouble with two different angles is that you end up with a line contact, which almost immediately wears away. With both angles the same, you get full face contact, and as the face wears the cone just sets farther into the cup. Thats why the adjustment slot is there in the blue part. As the clutch wears down and begins to slip, the bolt in the blue part is loosend up and the whole latch mechanism can be moved in a bit to keep pressure on the cone.


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## Jordan (Apr 22, 2013)

canadianhorsepower said:


> like a used Vbelt when all the sides rub it' slips



I thought a worn V belt slips (sometimes with noise) when the sides get so worn that the belt rides on the bottom of the pulley's Vee. Then the wedging action is lost.

Jordan


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## Brian Rupnow (Apr 22, 2013)

Jordan said:


> I thought a worn V belt slips (sometimes with noise) when the sides get so worn that the belt rides on the bottom of the pulley's Vee. Then the wedging action is lost.
> 
> Jordan


Yes Jordan, you are correct. That is why, in the design of this clutch, there is a lot of room between the end of the wooden cone and the inner bottom of the aluminum cone shape that it fits into. Once those two surfaces touch, the clutch loses about 95% of its eficiency.


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## Brian Rupnow (Apr 24, 2013)

I finally found some time to fully assemble this clutch, make the large pulley, and machine the spring loaded trigger latch, and make a base. I must say, it works fine with no noticeable binding at all. The adjustable latch not only holds the clutch cones fully engaged, but since it is adjustable, I can set now much force is applied between the two friction cones when the clutch is engaged. It also enables me to adjust for any wear that occurs.  I have put up two pictures, one showing the latch position when the clutch is engaged, and one showing it with the clutch disengaged. The large pulley is driven by a 0.100 rubber o-ring drive belt from the engine. The smaller pulley closest to the latch can either drive a flat belt off the smaller diameter, or can have a larger pulley bolted to the ring of holes in the larger diameter.--Now I have to get back to my Odds and Ends engine and do some carburetor work, and perhaps we can have a demo video. I'm not certain at this point if the Odds and Ends engine is going to have enough power to run the sawmill or not. Jim Dunmyer has built one of the sawmills, and his smaller engines don't have enough power to run it properly.---We'll see!!!!!---Brian


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## collbee (Apr 29, 2013)

The Centrifugal  Clutch system used on many early International tractors and 6hp stationary engines, may also be an interesting research project sometime in the future. I am pretty sure I have a pic of one in an old IHC catalogue. Will post when I find it. If I remember correctly ... no springs and one brass bearing ... but don't quote me lol.  Meanwhile I will post a very non-commital pic of one in use to wet the appetite.

Geoff


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## Coilmotorworks (Apr 30, 2013)

Some of the IH cltches could be engaged while running but the engine had to be shut off to disengage.


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## Brian Rupnow (May 9, 2013)

The clutch is finished, and it works very nicely. There is a video of it in operation in my post about "Model Sawmill Dreaming". For anyone wishing to build this clutch, the attached link will get you a free download of all the detail drawings in pdf format. When you click on the link, a page will open. Scroll down to the bottom of the page and choose the "slow download" option. Its not really slow, and it won't cost you anything.-Its not really slow, and it won't cost you anything.----A word of warning though--When you download it, you will be offered a whole damn bunch of junk offers. Just hit "Decline" every time that happens, and eventually you will get to the download---Brian
http://www.filefactory.com/file/1yrhedyn4p6d/CLUTCH_DETAIL_DRAWINGS.zip


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## rutzen (Oct 6, 2020)

Hello Coilmotorworks.  I am trying to do the drawings for a Rumely Model F to 1/8th scale that I want to build.  One of the details I can't work out is how the clutch works.  I can see that it is a friction clutch working on the inside of the belt pulley but how does the operating linkage work and how is the drive transmitted to the pinion which is on the other side of the belt pulley please?


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## larryg (Oct 7, 2020)

o;d thread


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