Friction clutch for small engines

[Anatol]

"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...

 

[razor7177]

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

 

[OldToad]

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

 

[werowance]

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.

 

[Brian Rupnow]

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.

 

[Brian Rupnow]

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.

 

[Brian Rupnow]

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.

 

[Brian Rupnow]

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.

 

[Buchanan]

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.

 

[nel2lar]

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

 

[Brian Rupnow]

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

 

[Buchanan]

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.

 

[nel2lar]

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

 

[propclock]

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.

 

[Brian Rupnow]

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.

 

[Brian Rupnow]

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.

 

[Brian Rupnow]

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.

 

[toolingjim]

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.

 

[Brian Rupnow]

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 Rupnow]

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.