# Friction clutch for small engines



## Brian Rupnow (Sep 22, 2018)

While I was working on the dog clutch for my recently built drag saw, I put out a request asking for a good design for a friction clutch that could be "miniaturized". Some kind hearted soul from another forum sent me a link to a one page document, which shows setting up instructions for exactly what I was looking for, which surprisingly enough was a friction clutch used on a drag saw. It must be about 100 years old, and will totally make your head explode trying to figure out how it works. It is a great design, because it not only engages the clutch, but a secondary and very beneficial effect is that it "traps" the clutch handle and won't let the clutch accidently disengage until the operator wants it to.  This is my interpretation of the mechanicals of this clutch, and an attempt to build one.
http://www.herculesengines.com/hercules/NewManual/page_58.html


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## Brian Rupnow (Sep 22, 2018)

These two models show the clutch engaged and disengaged. the green expander cone is slid along the shaft by an outside handle (not shown) and when it engages them it spreads them open, thus making them rotate and put pressure on the red friction disc. the yellow flywheel is keyed to the shaft. The blue hub with sprocket mounted on it floats on the shaft.


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## Brian Rupnow (Sep 22, 2018)

In about two minutes I am going to jump up and grab a piece of mild steel and make this expander cone. It's cold outside and good wife and visiting daughter are off to the mall. I don't have any 01 stock this large in diameter, so I'm not going to harden it.


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## minh-thanh (Sep 22, 2018)

That's Great
I'm looking to combine my engine with a car


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## Brian Rupnow (Sep 22, 2018)

First part made---the expander hub. I made it from a scrap end of material that I had left over from something.


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## Brian Rupnow (Sep 22, 2018)

I was originally going to make this clutch with three comma shaped arms. However, looking at the slitting saws I have, I decided to make it with four comma shape arms. This way I can cut the 1/8" wide slots in the blue hub all the way across the face.


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## 10K Pete (Sep 22, 2018)

Now you have a design that is very interesting to me. I wuz gonna take yer two arm and make it more powerful but you have done it here!

Excellent work! The magic of CAD....

Thanks,
Pete


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## Brian Rupnow (Sep 23, 2018)

I don't post very many set up shots anymore, but this is a worthy one. No, it's not a Maltese cross, it's the hub that will hold the four comma shaped arms. There is more work yet to be done on it.


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## Cymro77 (Sep 23, 2018)

Fantastic!


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## nel2lar (Sep 23, 2018)

Brian
I believe you have the winning combination. The drag saw drags on. No pun intended.
Nelson


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## Brian Rupnow (Sep 24, 2018)

Now, is that a beautiful thing or is that a beautiful thing? I chickened out at the very last moment and put the slots in with a 1/8" carbide endmill instead of using my slitting saw. This part is steel and I didn't want to take a years life off my slitting saw. I took 0.010" deep cuts with the mill running at 1300 rpm and hand cranked very cautiously so as not to snap the endmill off.


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## Brian Rupnow (Sep 24, 2018)

Now it's my turn to ask a question. What can I buy for a friction disc. The disc stands alone and is not attached to anything, simply centered on the shaft. In a perfect world, I would like something about 1/16" to 1/8" thick. Whatever it is, it has to not only have very good friction surfaces on it, but must be durable and capable of holding it's shape. It needs to be 2 1/4" diameter. If I don't get a good answer to this question, I may default to a piece of 1/4" plywood for a friction disc.


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## dtsh (Sep 24, 2018)

Have you looked at clutch pack material  for limited slip or perhaps motorcycle clutches? You many have some luck finding some in that diameter.


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## TonyM (Sep 24, 2018)

The old bike clutches had cork inserts. You could try epoxying a cork disk inside a thin aluminium ring and a small aluminium  centre.


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## Anatol (Sep 24, 2018)

Funny- this ad popped up in response to your question about what to make clutch disc out of


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## Anatol (Sep 24, 2018)

but hard leather might actually work. (?)


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## Brian Rupnow (Sep 24, 2018)

Maybe I'll go down in the swamp behind my place and catch a crocodile


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## Brian Rupnow (Sep 24, 2018)

I went down street on a shopping trip today, and bought a 3 foot length of 1" x 1/8" precision ground 01 steel to make the comma shaped pieces from. Also bought a couple of very healthy small springs, one of them will work on the end of the clutch shaft, not sure which yet. Also picked up a sprocket which can be bored out to fit the appropriate clutch hub. I sawed off four 1 1/2" long pieces of the 1 x 1/8" 01 material, lined up the sides and one end, and clamped them in a set of welding vice grips. I will put a dab of mig weld on the ends which will be trimmed away after the fact, so I can machine all four pieces at the same time to ensure that they are all the same.


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## Brian Rupnow (Sep 24, 2018)

I'm curious--those of you who have suggested leather, how would you use it. Would you glue it to the face of one of the discs, or just let it free float between the two metal discs?


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## razor7177 (Sep 24, 2018)

Brian, you'd probably have to epoxy the sucker onto a sacrificial piece( make sure you have afew of this as spares) just like a car dry clutch plate.
Hope this helps.


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## Anatol (Sep 24, 2018)

"those of you who have suggested leather, how would you use it. Would you glue it to the face of one of the discs,"
I was imagining it glued to one disc. But that was OTOH. But I feel like it might also need some kind of surface treatment - like violin bow resin? I may be completely wrong
I've played around with small electromagnetic clutches, the plate one side seemed to be some kind of fibrous cement. I might have been asbestos once...


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## razor7177 (Sep 25, 2018)

You should try making a centrifugal clutch, or buy a rc one.


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## OldToad (Sep 25, 2018)

Hi Anatol,
 I don't think leather would be very long lasting and offer the required drive. I have used the asbestos free friction material used for brake manufacture in the past,  its machinable and can be easily bonded to a back plate or drum and is available to purchase online try this site for ideas. http://www.autoandindustrial.co.uk/index.php?webpage=friction-materials
regards
Peter


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## werowance (Sep 25, 2018)

could you use actual clutch material?  my local junk yard has several clutch discs laying around all over the place that are worthless but do have what I would guess is plenty of friction material left on them for a model clutch,  and then what about mining belt or conveyor belt?  if mining belt will work I can cut you a piece and mail it to you if you want.


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## Brian Rupnow (Sep 25, 2018)

After cutting the four plates of 01 material to size and milling a notch in the area that will be machined away as a last step, I milled a notch 0.100" deep in all four plates and then with them clamped in a vice I ran a mig weld across all four plates in the bottom of the slot. Then any weld which was "proud" of the plate surface was removed with my 1/2" wide electric belt sander. Now I can grip all four plates together in the vice for farther machining operations.


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## Brian Rupnow (Sep 25, 2018)

Here are a couple of borderline awful pictures of drilling the appropriate holes in the stack of comma plates, and the final shape marked out on the drilled stack. Now it's cutter, file,  and grinder time.


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## Brian Rupnow (Sep 25, 2018)

One more thing before I cut loose with files and grinders. If you remember, I mentioned making "filing buttons" to accurately file the radii onto the ends of these comma shaped pieces. This shows the filing buttons in place in both ends. They are made from 01, and oil hardened to the max. A file will not touch them. Now when I file the rad on the comma shaped pieces, they should end up perfect. Then the filing buttons go into a jar where I keep all the different sizes I have made.


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## Brian Rupnow (Sep 25, 2018)

The fingers are all finished, filed and fitted. I am happy with the results so far. Now I can harden them. Those 3/16" diameter pins in the assembly are just scrap pieces I had available. The hardened filing buttons and pieces of 3/16" pins are shown along with the comma shaped pieces. Tomorrow I will make proper length pins with snap rings, and make some washers out of the 01 material I have left.


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## Buchanan (Sep 25, 2018)

Brian, I like that clutch. And your Saw is awesome. May I make a comment on Filing buttons.  For may years I made hard buttons and they work very well at maintaing a beautiful radius, but I ruined many of my best Swiss files on them, even when they barely touched them. Now I make  leave the buttons soft but make each  about two diameters long.  Then there is so much material to remove from the button  that they keep their shape just  fine, you don't have to stop and harden them, so, I am more inclined to make them , and best of all they don't harm the file.   If you make them  just loose on the pin, and, they can rotate freely, they don't ware down at all at all, if you file in the rolling direction.


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## nel2lar (Sep 25, 2018)

Brian 
There is nothing impossible for you, you are a master craftsman. Beautiful job on the fingers and all the new clutching components. I stand in awe.
Nelson


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## Brian Rupnow (Sep 25, 2018)

Buchanan--My files are old and cheap and should probably all be replaced. I do very little actual filing. I have about six different kinds of grinders and sanders, and would never resort to a manual file if I thought a power tool would do the job adequately. Nelson--I love this stuff. I spent over half a century as a design engineer designing custom machinery, and I get the biggest darn thrill out of making this stuff.---Brian


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## Buchanan (Sep 25, 2018)

Brian, I couldn't agree with you more about the grinders and sanders.  Keep going with what you are doing , I like it a lot, and the best part about what you are doing, is, you can do it the way you like it.


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## nel2lar (Sep 25, 2018)

Brian
You do not have to tell us how you love what you do,you show it in all the extra you do to make your projects better. And when you wrap it up it is perfect at the BEST. Like I said you are a true craftsman with a special touch.
Thank you for sharing all you do. Please don't ever stop, you are the best.
Nelson


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## propclock (Sep 26, 2018)

I might have missed this in previous post's
But the only drag saw I had ever contact with had a simple driven domed drive pulley,
and a floating bearing  idol pulley, And much
to my surprise the belt could be shifted 
from drive to idol with a stick or anything.
Talk about simple. Just my experience.
I know yours is gear driven, I really was surprised to see how easy it was to go from driven to engaged, with a nice slip /clutch
engagement  due to the belt being partially 
engaged, before riding up on the crown. 
  I guess all the Line shaft guys know what I mean.  Just my 1.414 cents worth.
I enjoy all your posts Brian.


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## Brian Rupnow (Sep 26, 2018)

Propclock--The dragsaw has a dog clutch on it, not a friction clutch. Big difference in the two types of clutch. a friction clutch can be engaged slowly to take strain off the drive components. A dog clutch is just 'WHAM' and it's engaged.


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## Brian Rupnow (Sep 26, 2018)

This was one of the days when I worked all day and don't have a lot to show for it. I drilled and tapped the end of the shaft for a threaded stud, shortened up a spring to fit, and drilled and tapped the holes to mount the sprocket. The sprocket had to be bored to fit on the hub. Tomorrow I'll make the proper pivot pins.


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## Brian Rupnow (Sep 26, 2018)

I think this clutch is going to work. Now that I have the spring in place and the appropriate washers and bushings made, I have assembled it with a clamp ring on the side which will normally hold the friction disc and flywheel. The sliding cone does indeed make the four "fingers" expand when pushed by hand, and the resulting action makes the entire pack expand about 1/16" linearly. That isn't much, but  it's surely enough to clamp the friction disc securely between two faces. I find this quite exciting.


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## toolingjim (Sep 26, 2018)

Just ran across your thread--great design. You might want to try looking at Mcmaster-Carr. They list sheets of brake/clutch lining in various frictional coefficients and thicknesses, starting at .14 x 1/8". Mcmaster is never the cheapest source, but they have most everything and they ship promptly. Hope this helps.


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## Brian Rupnow (Sep 26, 2018)

toolingjim--McMaster won't sell/ship to Canada unless you had an account with them 10 years ago. A gentleman in British Columbia has a piece of the McMaster Carr stuff, and is sending me enough to make this clutch.---Brian


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## Brian Rupnow (Sep 27, 2018)

I just had one of those mornings we don't like to talk about much. After fully assembling all the clutch pieces, I seen that one of the 01 steel washers could be shaved thinner to make things work better. So I did--and then it wouldn't work at all. So--I got to make a brand new washer from 01. Then I noticed that the bushing which the sliding cone slides on could be made 3/16" shorter to make a more compact package, so I did---and then it wouldn't work at all. So---I got to make a brand new 01 steel bushing. I hope I don't see anything else that needs improving!!! I may make the flywheel this afternoon, and I still have to harden all of the 01 steel pieces. I wish I had made that sliding cone out of 01, but I didn't have any 01 that size. I might ask a local shop about case hardening it.


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## Brian Rupnow (Sep 27, 2018)

So--If I had my friction material, we're ready to rock and roll. Since there is no way to show inanimate pictures and tell people "it works", I will be rigging a drive and a clutch handle and setting up a live performance I can take a video of.


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## Brian Rupnow (Sep 27, 2018)

I've had a revelation this afternoon!! My back was getting sore from standing at the lathe, so I decided to do a bit more studying on clutches, looking at dragsaw videos. When I made the dog clutch on my drag saw, the sliding portion of the dog clutch was moved by two 3/16" diameter pins thru the clutch handle as shown in the first picture. It worked, but I thought that the minimal contact between the round pins and the slot in the sliding cone would probably have been a problem. Today, I replayed all the YouTube dragsaw videos, and SHAZAM!!!--I seen that on the full size machine, there were actually two bronze crescents that fit into the groove on the sliding cone.--See second picture. Damn!!! Learn something new every day!!!


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## nel2lar (Sep 27, 2018)

razor7177 said:


> You should try making a centrifugal clutch, or buy a rc one.


centrifugal clutch requires a sharp increase of speed, Brian's engine runs very close to the same speed even under a load


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## Brian Rupnow (Sep 28, 2018)

I can get very close to what was originally designed by cutting the blue inserts from bronze, soldering on stub shafts, and using a piece of 2 1/2" std. pipe to form the outer housing. Not really sure that I want t go to all that bother, but maybe. A lot depends on how well I can silver solder onto bronze.


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## Brian Rupnow (Sep 28, 2018)

Oh yeah baby--I had some brass or bronze, (I don't know which and for what I'm doing it doesn't matter). Now I'm off to see a friend who will send my sliding cone out with some of his stuff to get case hardened.


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## LorenOtto (Sep 28, 2018)

Brian,
I have had some luck with 1/8" Masonite, not the hardened kind as it is too slick.  The regular grade gives a good bite on both sides.


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## Brian Rupnow (Sep 28, 2018)

Thanks Loren.--A gentleman in British Columbia had some extra friction material from McMaster Carr that was left over from a project, and he has mailed some to me. I just sent out the expander hub today for case hardening, so the project won't get finished for a week or more.---Brian


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## 69002 (Sep 29, 2018)

I know that you are the other side of the pond, and I don’t know if you have over there....a “bulldog” caravan anti-snake device used two friction discs of about the size you require....I’ll try and find a link.


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## Brian Rupnow (Sep 29, 2018)

Never heard of an anti snake anything.--Sounds interesting.


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## 69002 (Sep 29, 2018)

Link to “towsure” friction pads for their own and “bulldog” anti-snake or stabiliser bar..
https://www.towsure.com/bulldog-lc3-3-friction-discs-200q-400q-stabilisers


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## nodaker (Sep 29, 2018)

Brian:  I have been following this thread with interest.  When I was on the farm, we had a Wisconsin single lung engine with an enclosed clutch assembly and an exterior lever to engage or disengage the clutch.  the lever acted as a snap over center motion and the clutch itself was a cone clutch with a l ining.  I know you have done a lot of work on your current assembly but it could be the cone clutch complex is a better alternative.  John


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## Anatol (Sep 29, 2018)

Brian Rupnow said:


> I can get very close to what was originally designed by cutting the blue inserts from bronze, soldering on stub shafts, and using a piece of 2 1/2" std. pipe to form the outer housing. Not really sure that I want t go to all that bother, but maybe. A lot depends on how well I can silver solder onto bronze.
> 
> Brian, reading this thread is interesting because you understand, just by looking at a machine, how the parts function to handle the forces they experience. They developed that way because other solutions had broken, wore out etc. Its interesting to think about the 'evolution' of such things (at least for me
> 
> ...


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## Brian Rupnow (Sep 29, 2018)

All of my clutches 01 steel parts have been heated to orange/red, quenched in oil, and then baked in good wife's oven for 2 1/2 hours at 350 degrees. The heating and quenching makes them diamond hard, but very brittle. The oven heat soak leaved them hard but takes away the brittleness. The cone part of the clutch, which was made from mild steel has been sent out for case hardening. The bushing which fits between the cone and the shaft is also made from 01 steel, and has been heated, quenched, and tempered. It is not in the picture, because the surface finish was SO UGLY that I am ashamed to show it. On my very last pass on the o.d. I didn't retract the cutting tool before backing it away from the chuck, and it left a spiral gouge full length of the bushing. There wasn't enough material left to do a clean-up pass without going undersize. I dressed it with 200 grit carborundum strip paper, which takes off only about half a thou but cleans up a lot of the minor tooling marks, but the spiral gouge is still there. It won't affect anything, and will in fact act to retain some lubrication between the outer diameter of the bushing and the steel cone which slides on it, but it looks really nasty. Once everything is assembled it won't be visible.


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## Brian Rupnow (Sep 29, 2018)

Nodaker--I have built a cone clutch, and it works very well, but it is a bit too large to act in this application. It is not an "over center" mechanism, but has a spring loaded latch to hold the clutch engaged. I will try and hunt up the thread I posted while building it and put the link here.---Brian
https://www.homemodelenginemachinist.com/threads/clutch-again.20528/


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## LorenOtto (Sep 30, 2018)

nodaker said:


> Brian:  I have been following this thread with interest.  When I was on the farm, we had a Wisconsin single lung engine with an enclosed clutch assembly and an exterior lever to engage or disengage the clutch.  the lever acted as a snap over center motion and the clutch itself was a cone clutch with a l ining.  I know you have done a lot of work on your current assembly but it could be the cone clutch complex is a better alternative.  John



I have a full size drag saw that utilizes a cone clutch.  It works quite well.


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## Brian Rupnow (Sep 30, 2018)

Today I'm reduced to "farting around". Can't do much on the clutch assembly until I get the friction material and the part I sent out for case hardening back. I did accomplish one thing--a close examination of that big 8" wobbly v-belt pulley that I've used on numerous set-ups showed that two of the spokes were broken, so I went down to Canadian Tire and bought a new pulley and a couple of cheapo 1/2" dia. pillow block bearings. I modelled them this afternoon for something to do. The actual test set-up for video is going to look like this.


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## Brian Rupnow (Sep 30, 2018)

Loren Otto--I didn't say that a cone clutch wouldn't work on a dragsaw. I have also seen videos of them using a dog clutch. I have a great interest in clutches. I have built ( in model size) a cone clutch, a line shaft expanding shoe clutch, a dog clutch, and now this current clutch I'm working on is something new that I haven't built before. The excitement of modelling and building something new (to me) is what drives me in situations like this.---Brian


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## nel2lar (Sep 30, 2018)

Brian
I have been watching with quite a bit of fascination of the mechanics and the way you solve some of the problems. I was looking through some of my old files and ran upon my old Bolen mower and the clutch system on it, a lite bulb lit up. I was thinking in the idea of the center being a floating belt or chain sprocket with pads around the flats about .500 to .750 from edge. The newest method you have for engage and disengage  on the outside the shaft just like you have yours. This has become one of the best projects I've seen in a long time.
Looking good Brian
Nelson


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## DougC (Oct 1, 2018)

Brian Rupnow said:


> toolingjim--McMaster won't sell/ship to Canada unless you had an account with them 10 years ago. A gentleman in British Columbia has a piece of the McMaster Carr stuff, and is sending me enough to make this clutch.---Brian


Brian,
It appears that McMaster-Carr has started to service Canada.  Over the years I would occasionally give it a try ... and was always rejected.  A few months ago, I tried again and bingo ... no problems.  They charge GST, land the shipment in Canada (ie. no customs clearance fees), with two day courier shipping to my home in Salt Spring Island, BC for about US$20 shipping fee (I suppose depending on size & weight - I ordered about US$60 of various lengths of O ring cord, adhesive, a cutoff blade ....  so it wasn't very heavy).


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## Brian Rupnow (Oct 1, 2018)

I have reached the "Can't do anymore" point. I have to wait now for my friction material and my case hardened expander cone. This is the mechanism which operates the clutch. The ends of the flatbar are left untrimmed for now, until I assemble everything.


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## Brian Rupnow (Oct 1, 2018)

A huge THANK YOU going out to "Cuttings" from beautiful British Columbia for two pieces of friction disc material that came in my mail today.---Brian Rupnow


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## bmac2 (Oct 1, 2018)

Hi Brian

I’ve been following along and am enjoying this build and thought it was time to drop a note. If anyone should ever ask that _IS_ an oil groove and they are _Very_ hard to make . As a side note if “the good wife” ever gets touchy about using her oven for workshop projects have a look around for a toaster oven. I picked one up cheap at Value Village a couple of years ago. Anything that is used to process food usually goes pretty cheap and I wanted something to bake casting cores. Its good up to 500 degrees but I have to use shielding as the heat is not well distributed. It’s also handy to be able to set it in the back yard if there could be fumes involved.

Glad to see the friction material arrived before Canada Post went out.


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## Brian Rupnow (Oct 2, 2018)

This will be (more or less) the set-up for testing the clutch. An electric motor is going to drive the large pulley via a v-belt. The sprocket which is bolted to the driven hub of the clutch will drive a second smaller sprocket when the clutch is engaged, thru a #35 pitch roller chain. In order for a clutch like this to function properly, there has to be some resistance to turning. If there is no resistance to turning, then just the fact that the clutch sprocket is setting on a revolving shaft will make the sprocket turn also. The resistance in this case will be provided by a nylon pellet under a #10-24 set screw thru the side of the small sprocket shaft housing. I will be able to vary the resistance to turning by tightening down the set screw against the shaft which carries the small sprocket.


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## MachineTom (Oct 2, 2018)

Since you have some material your good at the moment. I recently rebuilt a Tapmatic Tapping Head. The friction disks were cheap like $4 each, that was the small 30 size head, I would suggest looking at a 70 size disk, about the size you were looking for.


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## Brian Rupnow (Oct 5, 2018)

And now we are in "wait mode". I can't do anymore until my case hardened expander hub comes back from case hardening.--And I can't call the guy and hurry him along, because its being done as a "favour". The set-up as shown lets the shaft revolve freely without turning the sprocket. it also lets the sprockets and chain revolve freely without rotating the shaft. I may have to adjust the width of the wooden stand, but won't know until the expander hub is installed and anchored in the correct place.


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## werowance (Oct 5, 2018)

Brian, are you using regular size bicycle chain or do you have a source for mini scale sized chain?


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## nel2lar (Oct 5, 2018)

Brian
Love your cad drawing and how much you do to make the demonstration model. Looking to the growth of this clutch.
Looking good.
Nelson


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## Brian Rupnow (Oct 5, 2018)

Werowance--that is #35 pitch industrial roller chain. I can buy the chain, sprockets, and connecting links at Princess Auto in Ontario.--Brian


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## Anatol (Oct 6, 2018)

regarding chain and the like, for those of us in US and maybe Canada - I've use the Surplus Center in Lincoln Nebraska for years, they have an amazing selection of surplus machine parts at low prices. I have no association with them except as a long time satisfied customer.


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## Brian Rupnow (Oct 8, 2018)

Spent today eating turkey and pumpkin pie--House was full of adult children and grandchildren. Good wife cooked her usual fantastic thanksgiving dinner.--and when I wasn't actively engaged in being grandpa I was thinking about clutches. Earlier in the week I had looked up and studied on a wrap-spring clutch, which I have never heard of before but now I know how they work. Also looked at a number of "over center" manual clutches and electromagnetic over-center clutches. I have built cone style clutches and expanding shoe clutches and dog clutches. They all seem to work, but they all (except for the dog clutch) seem to have too many parts to "miniaturize" down to a point where they work repeatably and consistently on an engine with a 3/8" crankshaft. I also looked at a proprietary friction clutch which is sold for go-carts and mini-bikes, but couldn't really tell how it operated. I hope to get the final part for my current clutch build back from case hardening this week to finish it up.---Brian


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## billco (Oct 8, 2018)

Brian Rupnow said:


> Spent today eating turkey and pumpkin pie--House was full of adult children and grandchildren. Good wife cooked her usual fantastic thanksgiving dinner.--and when I wasn't actively engaged in being grandpa I was thinking about clutches. Earlier in the week I had looked up and studied on a wrap-spring clutch, which I have never heard of before but now I know how they work. Also looked at a number of "over center" manual clutches and electromagnetic over-center clutches. I have built cone style clutches and expanding shoe clutches and dog clutches. They all seem to work, but they all (except for the dog clutch) seem to have too many parts to "miniaturize" down to a point where they work repeatably and consistently on an engine with a 3/8" crankshaft. I also looked at a proprietary friction clutch which is sold for go-carts and mini-bikes, but couldn't really tell how it operated. I hope to get the final part for my current clutch build back from case hardening this week to finish it up.---Brian



You could check your local hobby store. I believe the r/c cars use a friction clutch like the go carts only smaller .love your work and follow closely


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## velocette (Oct 8, 2018)

Hi Brian
enjoying following your progress on this clutch.  There is probably a problem here  from Billco With the RPM that they engage at  "You could check your local hobby store. I believe the r/c cars use a friction clutch like the go carts only smaller .love your work and follow closely".  
Eric


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## Brian Rupnow (Oct 9, 2018)

Today I'm just dickin' around. No real work and my clutch part isn't back from case hardening yet. Of all the different clutches I've designed, the expanding shoe clutch seems to lend itself best to installing on a small engine. It is relatively small at 1 3/4" diameter, and it doesn't put any axial load into the crankshaft. I checked out all of my engines, and the one most suited to adding a clutch to was the flathead engine I had featured in the Home Shop Machinist magazine a few years ago.


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## Brian Rupnow (Oct 15, 2018)

It seems that my case hardening friend has let me down. I will give him one more week and then I will get the part back and use it unhardened, or else build another from 01 and harden it myself.---Sorry about the delay.---Brian


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## nel2lar (Oct 15, 2018)

Brian
Sorry to hear the bad news. Maybe they are sick or just forgot about the part. 
Hopefully you come up with positive closure.
I've enjoyed your build.
Nelson


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## Brian Rupnow (Oct 15, 2018)

Nelson--I used to work for this guy about 20 years ago, and he was a really great boss. His machine shop ran into hard times and had to close about 15 years ago and he went to work for his competition right here in town immediately afterwards as a salesman. I know he had good intentions when he offered to have it case hardened, but he told me today that the company he now works for doesn't send as much stuff out for case hardening now as it used to. It's not a big deal. I have two projects on the go, along with an order I'm currently designing for a welding fixture for General Motors.


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## nel2lar (Oct 15, 2018)

sounds like all is good
Have a great day
Nelson


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## Brian Rupnow (Oct 19, 2018)

Okay--We're back in the saddle again on this project. I just went down to the machine shop that was going to have my tapered hub case hardened, and then didn't.--Moving on--I'm going out to my main garage right now and set this up with a motor to drive it, and see if and how well it works. A video and picture will be posted here shortly.---Brian


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## Brian Rupnow (Oct 19, 2018)

And as I promised, here we have a still shot of the assembled clutch, and a nice video of it in operation---Brian


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## Brian Rupnow (Oct 19, 2018)

As promised, here are all the engineering drawings to fabricate this clutch.---Brian
http://www.mediafire.com/file/x7shbmds6box782/FRICTION_CLUTCH_BASED_ON_DRAGSAW.zip/file


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