Ah, makes sense. BTW, I wasn't intending full crank to flat if that's what you inferred by the sketch. Just enough to keep them tight-ish to ne another. Just to lazy to draw the wavy form. Although I'm kind of intrigued to try LOL Yes maybe a filler like Tom mentions. I've also seen delicate metal parts bedded into/onto an MDF wood base with hardware store 5min Devcon epoxy. Do all the CNC milling & then apply heat gun. Epoxy softens & peels off with no residue quite nicely. But I just don't know how filler would interact with grinding wheels
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CMT Ursus 250 Repair: 1) Clutch
- Thread starter RobinHood
- Start date
Well, the first of three shipments just arrived! It was all from the same order (they apparently did not have all items in the same location, thus split it up on their end).
A few items were shipped from Cleveland yesterday and one item is coming from New Jersey, also shipped yesterday. That is very good service, IMHO.
So I just figured out how they got this to me so fast: the items in the box were in stock in Aurora, OH. They trucked the box to Hamilton, ON, where it made the daily flight on Cargojet to YYC. And then it was delivered this PM to my door. Amazing.
A few items were shipped from Cleveland yesterday and one item is coming from New Jersey, also shipped yesterday. That is very good service, IMHO.
So I just figured out how they got this to me so fast: the items in the box were in stock in Aurora, OH. They trucked the box to Hamilton, ON, where it made the daily flight on Cargojet to YYC. And then it was delivered this PM to my door. Amazing.
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You got it @Tom O!
The carbide will turn into scraper blades —> to freshen up the flaking on the cross slide and compound ways; some original ones are still there.
The steel sheet is 25 thou 1095 annealed spring steel --> back-up plan if the washer modification does not work satisfactorily. I can surface grind it down to 0.6mm and then using a die, form the wave washers and heat treat them (if I even have to).
The 932 bearing bronze is to make new clutch basked bushings —> that clutch problem I knew about when I inspected the lathe pre-purchase.
The carbide will turn into scraper blades —> to freshen up the flaking on the cross slide and compound ways; some original ones are still there.
The steel sheet is 25 thou 1095 annealed spring steel --> back-up plan if the washer modification does not work satisfactorily. I can surface grind it down to 0.6mm and then using a die, form the wave washers and heat treat them (if I even have to).
The 932 bearing bronze is to make new clutch basked bushings —> that clutch problem I knew about when I inspected the lathe pre-purchase.
Progress: managed to grind the OD and ID of the off-the-shelf wave washer. The Röhm chuck has V shaped grooves on the outside of the jaws. Was able to just grab the new washer on the ID and grind the outside.
The Röhm chuck does not have the same V grooves on the inside of the jaws, so I had to switch to the Pratt - it has them. That allowed the OD of the washer to be held securely, allowing ID grinding.
Here are the grinding spec: lathe spindle - 130 rpm; grinding stone - 1.5” OD, 8700 rpm; DoC - 0.05 mm; feed rate - 0.05 mm / rev for roughing, reducing to 0.03 mm / rev for finishing.
The new washer is still 0.3 mm oversized. Now that I know that I can grind it, I’ll fix that. The OE is on the left, the newly ground one in the middle and the off-the-shelf one with the OD rough ground, on the right.
Now I just have to make 3 more...
The Röhm chuck does not have the same V grooves on the inside of the jaws, so I had to switch to the Pratt - it has them. That allowed the OD of the washer to be held securely, allowing ID grinding.
Here are the grinding spec: lathe spindle - 130 rpm; grinding stone - 1.5” OD, 8700 rpm; DoC - 0.05 mm; feed rate - 0.05 mm / rev for roughing, reducing to 0.03 mm / rev for finishing.
The new washer is still 0.3 mm oversized. Now that I know that I can grind it, I’ll fix that. The OE is on the left, the newly ground one in the middle and the off-the-shelf one with the OD rough ground, on the right.
Now I just have to make 3 more...
Good job. So that's what those jaw grooves are for LoL!
Just curious if the diameters of your existing ones vary depending how you position the mic jaws? Do you think they were post ground like you are doing or pressed into wave shape heat treated from a circular washers shape? (therefore some probability that maybe a bit eccentric anyways). Or are just trying you make your perfectly circular rings within a min/max of existing?
Just curious if the diameters of your existing ones vary depending how you position the mic jaws? Do you think they were post ground like you are doing or pressed into wave shape heat treated from a circular washers shape? (therefore some probability that maybe a bit eccentric anyways). Or are just trying you make your perfectly circular rings within a min/max of existing?
I am using the Colchester.
The OE washers are surprisingly uniform in both ID & OD. I have not used mics to measure - I just use trusted callipers. There is quite a bit of clearance on both the ID and OD. The washer “floats” inside the driven steel.
I think they used a punch press and did a “hot” punch followed by an immediate quench. Then some vibratory tumbling to knock off the edges and that’s it.
The Baruffaldi machine tool company started in 1927 making motorcycle clutches - so I gather they have the process down pat. The driver and driven steels seem punched as well.
The electromagnetic brake on this lathe is also made by Baruffaldi: similar punched steels. Main difference: the driven ones are slightly dished so that the stack opens up after the electromagnet releases.
That’s the “brake” shaft: there is a gear missing in this picture as it is still “trapped” in the HS. It will only come out once the spindle is removed - that will be next on the list after I finish the clutch repair.
The OE washers are surprisingly uniform in both ID & OD. I have not used mics to measure - I just use trusted callipers. There is quite a bit of clearance on both the ID and OD. The washer “floats” inside the driven steel.
I think they used a punch press and did a “hot” punch followed by an immediate quench. Then some vibratory tumbling to knock off the edges and that’s it.
The Baruffaldi machine tool company started in 1927 making motorcycle clutches - so I gather they have the process down pat. The driver and driven steels seem punched as well.
The electromagnetic brake on this lathe is also made by Baruffaldi: similar punched steels. Main difference: the driven ones are slightly dished so that the stack opens up after the electromagnet releases.
That’s the “brake” shaft: there is a gear missing in this picture as it is still “trapped” in the HS. It will only come out once the spindle is removed - that will be next on the list after I finish the clutch repair.
I've never seen internal clutch assemblies like that, interesting stuff. I guess when you have HP flowing through the driveline like that it takes a lot of metal & friction surfaces.
Looks like your modified wave washer replacement will work out just fine. And no finicky holding jigs, bonus.
I was holding off on my backup plan Haha. I feel like you need a heat treat oven soon!
Looks like your modified wave washer replacement will work out just fine. And no finicky holding jigs, bonus.
I was holding off on my backup plan Haha. I feel like you need a heat treat oven soon!
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Thanks Peter.
Yes, am lucky that I can hold the washer with a regular chuck and did not have to make fancy fixtures. It saves some time.
The grinding is still a very slow process: it takes 60 passes to open the ID up. Perhaps I could be more aggressive with the DoC &/or feed rate, but i don’t want to heat up the washer too much and lose its temper.
Yes, the lathe has 10hp - so quite the surface area required to transmit the torque.
Yes, am lucky that I can hold the washer with a regular chuck and did not have to make fancy fixtures. It saves some time.
The grinding is still a very slow process: it takes 60 passes to open the ID up. Perhaps I could be more aggressive with the DoC &/or feed rate, but i don’t want to heat up the washer too much and lose its temper.
Yes, the lathe has 10hp - so quite the surface area required to transmit the torque.
So we hit a snag today. After making two washers, I assembled them on one side of the clutch pack. One on each extremity. Turns out that the new washers are weaker than the OEM ones. The plates drag. So even though the material is slightly thicker than the OEM, the spring rate must be just a bit less.
I was hoping that it would be the other way around - the new ones would be just a bit stronger than the old. That way, they would have compressed the originals just a bit more, but not enough to cause the plates to drag. The OEMs separate the plates really well and the gaps are relatively wide - they could be a bit narrower and the plates would still not drag.
I think I have two options now: get more of the same washers to modify so I can replace all 7 on one side (they should all have equal properties, so the plates should separate evenly), or get 4 thicker washers to modify, so I can be back at my original plan of putting a new one on each end of each stack.
Last resort remains: try and make all new ones from raw stock (which I have on hand) and see if they match the OEM ones. If they don’t, just make enough to service the whole pack... the heat treating is the challenge with that idea.
Any thoughts?
I was hoping that it would be the other way around - the new ones would be just a bit stronger than the old. That way, they would have compressed the originals just a bit more, but not enough to cause the plates to drag. The OEMs separate the plates really well and the gaps are relatively wide - they could be a bit narrower and the plates would still not drag.
I think I have two options now: get more of the same washers to modify so I can replace all 7 on one side (they should all have equal properties, so the plates should separate evenly), or get 4 thicker washers to modify, so I can be back at my original plan of putting a new one on each end of each stack.
Last resort remains: try and make all new ones from raw stock (which I have on hand) and see if they match the OEM ones. If they don’t, just make enough to service the whole pack... the heat treating is the challenge with that idea.
Any thoughts?
Bugger. Well by adding another spring washer in from you new set, say in the middle of the pack (1 left, 1 right, 1 center), the complete multi-spring set will compress more due to reduced accommodation room & yield more force. Maybe enough to overcome the weaker spring constants. The question is will it fit & still allow the engage/disengage action.
If you need to stick with 2 new, possibly add dummy non-wave regular shim washers on either end & sneak up on a thickness combination that works? Its a less effective variant of above because the dummy doesn't spring but net effect will yield more total force. But may cause issues in another way.
If you wanted to try making them, maybe last resort, I can find the name of local-ish bladesmith guy I used who has the HT equipment. As long as you knew your alloy & temp, pretty sure he could hit the temp/soak much more reliably than anything you could do reliably with a torch or whatever. I just mailed him my came plate with instructions (after pre discussion) & he mailed them back but maybe he accommodates in person too.
If you need to stick with 2 new, possibly add dummy non-wave regular shim washers on either end & sneak up on a thickness combination that works? Its a less effective variant of above because the dummy doesn't spring but net effect will yield more total force. But may cause issues in another way.
If you wanted to try making them, maybe last resort, I can find the name of local-ish bladesmith guy I used who has the HT equipment. As long as you knew your alloy & temp, pretty sure he could hit the temp/soak much more reliably than anything you could do reliably with a torch or whatever. I just mailed him my came plate with instructions (after pre discussion) & he mailed them back but maybe he accommodates in person too.
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Craig, I probably was not clear what I am trying to replace: the FWD and the REV side of the clutch each have 7 spring washers, total 14 for the clutch pack. Four of them are broken and need to be replaced. (I’d probably replace all 14 if I could find a rebuild kit). Since I figured that it would be next to impossible to match the spring properties of the original washers without finding NOS, I decided that if I can make some replacement washers, they would have to have the same (or very close to) physical dimensions, and, be at least as stiff (= perfect match) or slightly stiffer than the OE ones. I have been successful in grinding the new springs to the physical dimensions. If they were too stiff, I’d just grind a wee bit more off to try and soften them for a better match. But the ones I have ground are too weak - I can’t make them stiffer. This is where the options I though of above (post #35) come in.
The two new “stiffer” springs would go on each end of both the FWD and REV clutch pack. Both the FWD and the REV side would still have 5 of the OEM springs in the middle. Total 7 per side.
A driver plate is 1.1mm thick. They can slide axially on the input shaft. A driven plate is also 1.1mm thick, they can also slide on the input shaft as well as the output basket. Nested in the center of the driven plate is the wave spring washer. Uncompressed, it is about 4mm high. The thickness is 0.6mm. All assembled (9 drivers and 7 driven) the washers are slightly pre-loaded (partially compressed) with about 0.5mm of clearance on each side of the driven plates ==> low friction / free wheeling position. If I put two new washers that are slightly heavier on each extreme end of the 7 washer stack, it will compress the 5 OE washers just a bit more, but still leave clearance as the forces in all the springs will equalize. When the clutch is engaged, all spring force is mechanically overcome and the plates are pressed hard together. In slow motion, one would probably see the center 5 driven discs make contact with their drivers first as the gaps are smaller than the two outer most ones with the heavier springs and thus bigger gaps. Releasing the clutch would be opposite: outer two open first, inner 5 last. With weaker outer springs, that does not work as there is a very small, no gap to begin with and the plates drag.
So no, I am not trying to replace 7 springs with just two. Apologies for wording my problem poorly in the previous posts.
John / Peter, I believe there is unfortunately not enough space for two, stacked spring washers (or one spring washer and a spacer) as they are 1.4mm thick together (the max space available in the compressed state is </= 1.1mm as dictated by the driven plate thickness). I need to clarify a bit: there is enough space in the disengaged position, but when you engage the clutch, the wave washers won’t allow the plates to close because two of them stacked are too thick.
The washer next size up has a compressed rating of 65lbs, with a thickness of 0.76mm. The ones I presently have are 57lbs, 0.71mm thick. ID and OD will need adjusting to make them fit, but hopefully it will match the OE ones or be slightly heavier when ground.
The raw stock is annealed 1095 carbon steel sheet. I do have the recipe how to heat treat it - apparently it is one of the more difficult steels to get the HT right (of course it would be); compounding the problem is the small cross section and the large OD of the washer as the heat will be lost very fast when it comes out of the oven and into the quench (1095 allows 5 sec max between oven and bath...)
The two new “stiffer” springs would go on each end of both the FWD and REV clutch pack. Both the FWD and the REV side would still have 5 of the OEM springs in the middle. Total 7 per side.
A driver plate is 1.1mm thick. They can slide axially on the input shaft. A driven plate is also 1.1mm thick, they can also slide on the input shaft as well as the output basket. Nested in the center of the driven plate is the wave spring washer. Uncompressed, it is about 4mm high. The thickness is 0.6mm. All assembled (9 drivers and 7 driven) the washers are slightly pre-loaded (partially compressed) with about 0.5mm of clearance on each side of the driven plates ==> low friction / free wheeling position. If I put two new washers that are slightly heavier on each extreme end of the 7 washer stack, it will compress the 5 OE washers just a bit more, but still leave clearance as the forces in all the springs will equalize. When the clutch is engaged, all spring force is mechanically overcome and the plates are pressed hard together. In slow motion, one would probably see the center 5 driven discs make contact with their drivers first as the gaps are smaller than the two outer most ones with the heavier springs and thus bigger gaps. Releasing the clutch would be opposite: outer two open first, inner 5 last. With weaker outer springs, that does not work as there is a very small, no gap to begin with and the plates drag.
So no, I am not trying to replace 7 springs with just two. Apologies for wording my problem poorly in the previous posts.
John / Peter, I believe there is unfortunately not enough space for two, stacked spring washers (or one spring washer and a spacer) as they are 1.4mm thick together (the max space available in the compressed state is </= 1.1mm as dictated by the driven plate thickness). I need to clarify a bit: there is enough space in the disengaged position, but when you engage the clutch, the wave washers won’t allow the plates to close because two of them stacked are too thick.
The washer next size up has a compressed rating of 65lbs, with a thickness of 0.76mm. The ones I presently have are 57lbs, 0.71mm thick. ID and OD will need adjusting to make them fit, but hopefully it will match the OE ones or be slightly heavier when ground.
The raw stock is annealed 1095 carbon steel sheet. I do have the recipe how to heat treat it - apparently it is one of the more difficult steels to get the HT right (of course it would be); compounding the problem is the small cross section and the large OD of the washer as the heat will be lost very fast when it comes out of the oven and into the quench (1095 allows 5 sec max between oven and bath...)
Dabbler
ersatz engineer
That's the problem of trying to help via armchair - 
- I only get to see a tiny part of the whole , and so the suggestions don't work too well!
On the heat treat side, you will have to locate the bath as close as possible to your oven. - Bert made this mistake once, as he only likes to do things one way and perfect that - but when HTin a very tiny part it always got screwed up until we hung a coffee can right off the front face of the furnace, beside the door... Even the cold tongs screwed it up, until we got them dark red via oxyacet before removing the part. You can use a HT wire and lift and dunk from that.
Any luck with contacting the OEM on getting replacement springs?
- I only get to see a tiny part of the whole , and so the suggestions don't work too well!On the heat treat side, you will have to locate the bath as close as possible to your oven. - Bert made this mistake once, as he only likes to do things one way and perfect that - but when HTin a very tiny part it always got screwed up until we hung a coffee can right off the front face of the furnace, beside the door... Even the cold tongs screwed it up, until we got them dark red via oxyacet before removing the part. You can use a HT wire and lift and dunk from that.
Any luck with contacting the OEM on getting replacement springs?