Clutching at straws?

[Billybream]

When fitting the SRM Alloy Plate and Top Hat Radial bearing you would have shortened the push rod, did you harden the cut end.
Also worthwhile modification is to cut the push rod in half and insert a ball bearing.
Sure it will be something simple, best of luck with the refit.

[Colsbeeza]

Billy,
My pressure plate did not come with a ball bearing, but had a 1/4" steel cup in the centre. I presumed it was meant to have a ball bearing there, so I put a used steering head ball (don't throw anything away) in it anyway - greased to stop it falling out whilst assembling. For the pushrod,  I used a new piece of 1/4" Silver steel, as the old one was too short (my old Inner drum was only 30mm deep, not 35mm as it should have been.
I was a bit hesitant to cut the rod and put a ball in the middle, as with my luck it would fall into the gearbox if I withdrew the rod. So I didn't. The new rod was 297.5mm, and the old one was 292.5mm. No surprise really, as the new drum was deeper by 5mm.
I did try to harden the ends by heating to cherry red (Silver Steel recommended 770-790 DegC), checking for magnetism to ensure I was above 770 DegC, and quenching, followed by tempering. As I have never done any hardening before, I am not sure how successful it will be. It seemed hard by the file test. I used an old Honda alternator rotor for a magnet. It has a very strong pull, and I could not feel the magnetism easing. So quenched it anyway. Then on tempering I am darned if I could see the colours going straw or any other colour, so dunked it anyway. It hissed a bit, so was at least 100 DegC. Time will tell. Tubal Cain strongly recommends lots of practice to get good judgement - how true.!
Colin

[chaterlea25]

Hi Colin,
After hardening, you need to polish the rod end back to shiny steel, then when you re heat you can see the colour changing

John

[KiwiGF]

Billy,
My pressure plate did not come with a ball bearing, but had a 1/4" steel cup in the centre. I presumed it was meant to have a ball bearing there, so I put a used steering head ball (don't throw anything away) in it anyway - greased to stop it falling out whilst assembling. For the pushrod,  I used a new piece of 1/4" Silver steel, as the old one was too short (my old Inner drum was only 30mm deep, not 35mm as it should have been.
I was a bit hesitant to cut the rod and put a ball in the middle, as with my luck it would fall into the gearbox if I withdrew the rod. So I didn't. The new rod was 297.5mm, and the old one was 292.5mm. No surprise really, as the new drum was deeper by 5mm.
I did try to harden the ends by heating to cherry red (Silver Steel recommended 770-790 DegC), checking for magnetism to ensure I was above 770 DegC, and quenching, followed by tempering. As I have never done any hardening before, I am not sure how successful it will be. It seemed hard by the file test. I used an old Honda alternator rotor for a magnet. It has a very strong pull, and I could not feel the magnetism easing. So quenched it anyway. Then on tempering I am darned if I could see the colours going straw or any other colour, so dunked it anyway. It hissed a bit, so was at least 100 DegC. Time will tell. Tubal Cain strongly recommends lots of practice to get good judgement - how true.!
Colin

Rightly or wrongly I was far less scientific than this, I just get the rod end red hot and dunk it in water, with no tempering done afterwards as there is no bending of the rod going on and I just want it glass hard, I’ve always done it this way without problems

[Colsbeeza]

Thanks John,
Tubal Cain was a bit vague about polishing the rod end before tempering. Next time, I will polish it. Presumably the quickest way to keep it warm is to touch it to the motorised wire brush on my bench grinder.? Or some 1200 Wet & Dry.? Maybe autosol or Goddards Glow afterwards.? What do you use John.?
kiwigf - that is interesting. The books are of the opinion that the steel would be very brittle, thus the need for tempering. Given the relatively light load, perhaps it is not a huge problem if you quench harden only without tempering.?
Cheers
Colin

[KiwiGF]

Thanks John,
Tubal Cain was a bit vague about polishing the rod end before tempering. Next time, I will polish it. Presumably the quickest way to keep it warm is to touch it to the motorised wire brush on my bench grinder.? Or some 1200 Wet & Dry.? Maybe autosol or Goddards Glow afterwards.? What do you use John.?
kiwigf - that is interesting. The books are of the opinion that the steel would be very brittle, thus the need for tempering. Given the relatively light load, perhaps it is not a huge problem if you quench harden only without tempering.?
Cheers
Colin

I’ve not thought about it too much, but a push rod is not like a knife blade which is subject to being flexed or bent and where the steel being brittle would be a problem, so I’m thinking the rod end being brittle is not a problem in practice, and really what is wanted is a rod harder than the ball bearing, and tempering will soften the rod end, albeit maybe only a small amount if done properly.

[RogerSB]

When I had to make a push rod for a new SRM clutch last year I made one out of a length of 6mm dia silver steel purchased locally. After I cut it to the size required I heated both ends (one end at a time I will add) until glowing red and then quenched in ATF oil. In my ignorance I didn't temper the ends afterwards. I haven't checked the ends since fitting, as the clutch has pefrormed faultlessly - so I'm hoping a quench in ATF oil was good enough.

[JulianS]

Have used method described by RogerSB a number of times, never tempered and never had any problem after many many miles.

It is the method recommended in the instructions which come with the SRM clutch, the same method was recommended by Devimead back in 1982 when I first fitted their light alloy pressure with needle thrust bearing and shortened the rod.

[chaterlea25]

Hi Colin,
I just use a bit of fine emery to get the steel colour back, nothing exotic
That said I have often just quenched the ends of the rod in water, touch with a file and see if it bounces off
Thats hard enough

John

[Colsbeeza]

Thanks John  (CL25), I wasn't sure that the 1200 grit may scratch the rod, inducing cracks. Looks like the books are aimed at perfection, whereas we just want to harden it.
Sorry John (a101960), we have hijacked your problem a bit with pushrod issues. Not sure whether any of this has helped with your clutch problem.
Colin

[a101960]

Sorry John (a101960), we have hijacked your problem a bit with pushrod issues. Not sure whether any of this has helped with your clutch problem.

Colsbeeza Don't worry about that. It is all very interesting. As for my problem I spent the whole of yesterday resetting the spring tension ( a bit lighter) and pressure plate lift. Primary cover is not yet fitted, so I have not yet tried it out. Not sure if this is a good omen or not, but now when I turn the engine over with the kick start there is an audible clank when the clutch is operated and the plates "rattle" when the clutch is turning with the lever pulled in. Time will tell I suppose. Mind you it was far to hot really to be working in the garage, I was knackered by the time I had finished.

[duTch]

 I hope this one works for you- plates rattling sounds good to me, but....

 

..... Mind you it was far to hot really to be working in the garage, I was knackered by the time I had finished. 

 Just how hot was it ?? ...like enough to temper the pushrod ??

[KiwiGF]

Sorry John (a101960), we have hijacked your problem a bit with pushrod issues. Not sure whether any of this has helped with your clutch problem.

Colsbeeza Don't worry about that. It is all very interesting. As for my problem I spent the whole of yesterday resetting the spring tension ( a bit lighter) and pressure plate lift. Primary cover is not yet fitted, so I have not yet tried it out. Not sure if this is a good omen or not, but now when I turn the engine over with the kick start there is an audible clank when the clutch is operated and the plates "rattle" when the clutch is turning with the lever pulled in. Time will tell I suppose. Mind you it was far to hot really to be working in the garage, I was knackered by the time I had finished.

Can you give it a test ride before fitting the cover? I did that to establish roughly how far I could back the springs off before it started slipping. On the swing arm it’s best to put bolts temporarily into the front 3 holes before setting off.

[a101960]

Just how hot was it ?? ...like enough to temper the pushrod ??

dutch easily hot enough to do that! It was so quite too, not a sound anywhere. There I was totally absorbed in the task of clutch fixing, and the rest of neighbourhood indoors watching the tele. Shame the bike was not road worthy otherwise I would have been out taking advantage of the empty roads.

[a101960]

Well, the clutch is back together again, and last night I went for a test ride after spending forever and a day setting the clutch springs up. Not much improvement. Now, a question about the chainwheel bolts. Mine are loose and wobble about all over the place. Should they do that? or should they be reasonably rigid? Do I need to buy a new chain wheel? It has occured to me that maybe this is where my problem might be, and my reasoning for this is that the bolts are relying on spring tension to keep them central, and therefore are potentially likely to move about as the spring pressure changes causing the clutch adjustment to alter as the clutch is operated. I can't see any other reason for the clutch behaving as it does due to misalignment of the springs as they compress and release. Just a thought as everything else checks out OK.