Clutch Pressure Plate Assistance

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Hi, all-

I am using a Newby clutch on a G15-CS, and one of the issues is clearance between the mainshaft and the clutch pressure plate. Long story short, shortened mainshaft 2mm per Newby's instructions, but put on a clutch seal which has eliminated the clearance I created.

Question: I relieved some metal off the inside of the clutch plate, but need to take off more.

Relief in clutch pressure plate by Mick Doul, on Flickr

Concerned with the elimination of threads for the adjuster screw and am considering a steel thread insert to increase the interface area with the aluminum plate.

1- Is this a vaild approach?

2-Which type of insert would be best (timesert type? Helicoil?) and how should I install it?

Thanks!
 

texasSlick

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I think it is a valid approach. The goal is to spread the load on the threads over more area in a radial direction, to compensate for loss of area in the axial direction.

Which is best is the insert that gains the greater area.

Without making any measurements, my guess would be the Timesert.

Slick
 
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Thanks, Slick.

Timeserts are pretty thin-walled, so the helicoil might be better in the diameter respect. My concern mostly about the insert spinning itself out...think that's valid at all?

I thought maybe I'd try this...?

Stainless Steel Screw-Locking Helical Inserts


A distorted thread grips the screw to resist loosening. Also known as Heli-Coil inserts, these inserts have coils that expand once installed to securely anchor the insert. All have a prong for ease of installation. An installation tool grips the prong and reduces the coil diameter, enabling the insert to fit in tapped holes. Remove the prong to insert the screw. Installation requires a drill bit, a helical insert tap, an installation tool, and a prong break-off tool.

For technical drawings and 3-D models, click on a part number.
 

texasSlick

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I am well famiiar with helicoils. You can ensure the coil does not loosen with a dab of red Loctite. Swab out the inside of the helicoil to remove excess Loctite .... you do not want to Loctite the adjuster screw.

If you have access to machine tools, you might consider making your own bushing .... use a fine thread on the OD of the bush, and tap the ID for the adjuster thread.

Is there any cavity on the inside surface of the pressure plate? Your custom made bush could be made with a top hat and inserted from behind the pressure plate. Also, if a cavity, make the bush longer in the axial direction to gain more thread area for the adjuster.

Slick
 
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Slick, wasn't implying you weren't familiar with helicoils! Sorry...was just musing on the specific "screw-locking" style they're selling at McMaster, among their other choices. Then again, installed with green bearing retainer I'd expect any thread repair to stay in place reasonably well.

The bushing idea is great, but I'm not a machinst. I could probably send it to a friend to do the job, though...hmm.

Just wondering if I'm overthinking all this as usual, or conversely if I'll end up "that guy" who just machined away his clutch plate without thinking it through and locked up his primary when it came apart, lol...
 

texasSlick

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Just wondering if I'm overthinking all this as usual, or conversely if I'll end up "that guy" who just machined away his clutch plate without thinking it through and locked up his primary when it came apart, lol...
Only you have your eyeballs on that pressure plate.

How about a pic of the backside of the pressure plate, and another of the clutch with the PP removed. I am trying to grasp how much room you have back there. Also, how thin is the PP at this point.

Slick

Edit: Ooops! After re-reading your original post, I realize I am seeing the back side of the PP.
 
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texasSlick

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Here is another thought ....

Flanged bronze bushings are available stock from bearing suppliers such as Purvis Bearings, Allied Industrial Supply, to name just two.

Consider purchase of a flanged bush having the right ID to tap for the adjuster, then machine the PP for a press fit of the bush.

This simple machine work could be accomplished with a drill press and a file (that is about the level of my machinist skills)

I have long lamented never getting a small bench lathe. The problem with getting one now is there isn't enough time to get my money out of one!

Slick

Edit: Since I now realize I am looking at the back side of the PP, the use of a flanged bush is not possible, as the flange would be exactly where you are trying to gain clearance. A plain threaded bush is still do-able.
 
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Slick, I tried to get some photos earlier to clarify, but was unable to get anything meaningful out of it.

I will take a photo of the clutch pack for you when I can. Looking at the pic above, even with the relief you see in the PP, the inner side is barely clear of the pushrod seal nut on the mainshaft when the PP is in place; ie, it's close to riding right on the mainshaft. Grinding more relief would allow for clutch plate wear before the shaft and PP interfere, causing clutch slip. (Installation of the clutch pushrod seal holder/nut ate up the clearance I had gained through some cutting/grinding of the mainshaft...)

At this point, the PP is 7mm thick through the remaining threads. If it went to 5mm thick, do you think that would still be enough to allow the M10 adjuster bolt to function without overstressing the threads?

Similar to your bushing idea, using an insert like the one below seems like a possibility. I don't have an M16 tap, though...or the bit to drill for it. The insert is much longer than my PP would require, but I could grind it flat after installation.

Another idea, which Bob Newby put forth while I was having my initial problems with mainshaft/PP interference, was another metal plate in the clutch stack. Actually, that's probably the easiest and cheapest way out of this issue. I will likely go that direction...cheaper and easier than any other. Bob Newby's concern with the approach is more weight on the clutch and less efficient heat transfer, so he advised me to grind the clearance at the mainshaft...did this but, again, now I've lost the clearance due to the seal nut. Bob's concerns seem largely theoretical for my non-race use, and it's a simple, inexpensive, non-invasive solution.

I forgot about that.


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Black-Phosphate Steel Easy-to-Install Thread-Locking Inserts

A black-phosphate finish provides mild corrosion resistance. Also known as E-Z Lok, these inserts use Loctite® adhesive to keep them in place. The adhesive reaches full strength after 72 hours. Installation requires a drill bit and a standard tap. Then set the insert with a bolt and two nuts, or use an installation bit.

Inserts with a thin wall are often used in small holes or near the edge of a workpiece.

Choose inserts with a thick wall for greater strength than thin-wall inserts, or to fill a large hole.

To drive slotted inserts, you can use a slotted screwdriver instead of using an installation bit or a bolt and two nuts.

For technical drawings and 3-D models, click on a part number.

Metric



Black-Phosphate Steel with Thick Wall
M10 1.5 Coarse 9/16"-12 __ 33/64" 31/64" 31/64" Slotted 10 97084A130 13.00 94110A160 9.26


M10 1.5 Coarse M16 2 17mm 14 mm 14mm Slotted 5 97084A250 14.38 94110A160 9.26
-----
 
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Yep, that's the seal nut. I gave a light dremel flap-wheeling to the nose of the arrangement this morning, but didn't want to take too much off.

The mainshaft already has 2mm ground off (per Bob Newby's instructions to me) and I wouldn't want to take off any more...I had to shorten the o-ring carrier of the seal quite a bit to match this already.
 

texasSlick

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Go with the extra clutch plate. I think you would be pushing the limit by thinning the PP to 5 mm.

I agree that Newby's concerns are largely theoretical. The extra plate could be placed anywhere in the stack ..... why not a plain plate innermost? Check with Newby for optimum plate thickness, if he should have options on that.

Slick

Edit: just be sure the extra plate does not push the top plate out of the basket!!
 
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Yes, for sure on all...!

Given Bob's the guy who brought up the possibility, I think it's likely to work, but I will do a careful test-fit first to make sure it all functions appropriately with my setup.
 

texasSlick

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So, if you shortened the nose of the mainshaft by 2 mm, did you also shorten the clutch pushrod?

If so, I would be concerned the tip of the rod, which I would think is hardened, might now be soft.

Dang! One thing leads to another.

I hope I don't needlessly worry you about the rod tip, as I do not know for sure whether it is hardened. Try scratching the tip with a file .... use the clutch actuator side for comparison if you have ground one end off.

Slick
 
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Oh, I've been adjusting and re-hardening the rod to suit my various configurations, generally 2-piece with a ball bearing, along with rounding the rod ends to engage the Newby adjuster, as recommended by manufacturer.
 
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No worries; appreciate the insight and experience!

You are very right that this bike and my tinkering often lead to an old-lady-who-swallowed-the-fly situation, and my relative lack of experience sometimes causes me to either miss important downstream effects or fail to see obvious problems in front of my face.

Ed: I did have fun learning to re-harden the rod ends, and using my drill clamped to the bench as a mini-lathe against my Dremel flap wheel to reshape the rod end was a high point of smug ingenuity for me.
 
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So I added the steel clutch plate, and with the clutch engaged, the pressure plate -barely- has enough grip on the posts in the hub to stay in place. With a little wear to thin out the clutch stack I'm sure it's fine, but I think I'll wait for this little wear to occur before putting it in there.

It would be easier to remove Dynodave style clutch nut seal holder and just go to an o-ring seated in a groove on the pushrod, however. This is, in fact, what Bob Newby recommended to me, and I'm inclined to follow the man's advice.

Has anyone used this method to help seal the primary from the transmission? Glad to hear about any experiences or opinions.
 
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the only issue i see with an o ring on the clutch rod to main shaft is the inside of the main shaft is usually a very rough finish so not fit for a seal to work on the ID.
 
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Bill, my solution for that was an undersize o-ring combined with a bunch of grease. Maybe not perfect, but I hope it should largely if not totally mitigate. I think I'll try and see. Worst comes to worst, I'll put the seal nut back on
 

t ingermanson

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Not to diminish Dave's clutch rod seal, but I've found that a viscous mineral oil-resisting grease squirted through the mainshaft, the length of the clutch rod works wonders.

I found a grease called Huskey HVS-100 that does an excellent job keeping the oil out of my Newby clutch. It's not as sexy as an aftermarket seal kit, but it does the job well and takes up zero room.
 
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