clutch basket

Well. anyone had a go at riveting a clutch basket together? is this something that should be done by others or is it possible to do yourself?

I'm watching this topic , should be riviting lol

might be riveting, but could turn you into a basket case  ive gone for 6 a2 m5 counter sunk bolts , finished off with m5 nylocks and a splash of lock tight... basket needs a bit of trimming so that the lovley new chain from Rex will fit correctly. which is where this little project ends for now as i dont have a lathe ... but i could set it up on an old gear shaft and spin it with a battery drill, if i feel like spending half the day building a wooden jig to hold it all

Nigel,
       This is what I did with the clutch body when building w/c engine back in 98, never worked lose and is still together today, 5mm csk head Allen screws, lock washers and thread lock grade Loctite. The whole thing was dynamically balanced, as best as I could get it, the chain wheel was mounted on a mandrel and skimmed on both faces to balance and provide uniform thickness, the lightening holes were symmetrically and concentrically located. The body I made from EN24t which rendered it un-burstable, and locates on the chain wheel with minimal run out. Make, fit, forget!

However, this does not answer your actual question! I did try rivets but could never get them tight enough with the kit I had to hand, plus my lack of riveting skills, and they always seemed to fret themselves lose. The out of balance forces of a clutch body snatching and failing around at 10k is quite alarming. I got one of the maths boffins at work to calculate it all out and quite how the primary chain survives is a miracle. It is also worh pointing out that the main shaft will also flex over its length and undoubtedly contributes to gearbox troubles!
I did get an out-rigger bearing set-up on paper to reduce further still the clutch throw but we packed up racing before I got into metal, be well worth someone having a go at it though?

Trevor

nigel, reading your post i see you mention a2 bolts, i take it you mean stainless one, not sure they'll be best as although stainless it tougher than steel they're not high tensile and i have found theyre prone to vibration fractures etc, if it were me id use super high tensile grade 10.8 minimum 12.9 or 15.9, even a 12.9 will be almost double the strength of an a2 bolt (k nuts work best for vibi stuff too )

ok.... thanks for the replys . i thought the stainless would be stronger, but this can be changed as ive since pulled it all apart again. that lock tight is good stuff. had to cut off the nuts to disassemble.

ive put my Bant-a-geva engine back together again with the bantam clutch basket for now, but at least i can see whats required to fit the more modern lightweight system

my reason to try changing the basket etc was due to what i found when i took the bike up the road for a quick spin,,, (pre dyno session) the heavy duty springs and four plate clutch were not man enough to withstand the engines power. when i took off the side casing it smelt like it had been on fire and further examination after pulling apart showed excessive wear to the plates. also my home made offset engine sprocket has buckled which needs to be addressed. its made up from two sprockets bolted together spaced in between for the offset, but ive again used m8 stainless cap head screws to bolt one to the other which have bent, unbelievably, under the strain.

im thinking maybe i should have turned the cylinder base plate enough to allow the exhaust port to pass the frame and then offsetting engine and sprocket wouldnt be needed.

considering this was only being done as a way to go on and develop my own water cooled barrel its becoming annoying!!!
still... got a nice aprillia rs 125 and baby blade to play on

Stainless is very overrated I can't recall the grades that most are made of but it's mostly censored lIkea 304 etc, if you do  bolt together hunt out screws with a parallel shank and minimum thread (not always easy with csk) the load will ne borne on the thickest part as the threaded bit is only 4.1-2 mm !

I thought that this photo of a Harley Hummer clutch might be of some interest for those viewing this topic. More plates than the Bantam and the lightening holes already there, great shame that BSA didn`t do likewise, could have saved a lot of anguish for us racers!

Trevor

getting ready to remove a bit of metal to let timing chain fit

Nigel,
Nice fixture you have concocted there, but I am intrigued as to what comes next! What metal are you removing, from where, and, with what? Knowing your innate flair for innovation, this should be well worth watching, hope it all went well. Are we going to be treated to a sequential photo montage?

Cheers, Trevor

ooops. sorry..just come out the garage having trimmed the edge of the basket where it fits to the bantam clutch wheel. the gap just needed increasing to allow the chain to fit correctly.. i didnt photo anything. tried to upload a video yesterday to this site but i couldnt transfer it from my phone as it was too big.

i need a new nut to fit to the end of the gear shaft where the clutch fits... any idea what size this is?

Nigel,
My main shaft thread mics up at just under .500" and has 16 threads per inch with a 55* angle, so according to my trusty old thread pitch gauges and Zeus hand book that makes it.... 1/2" bsf.

Trevor

thanks Trevor...

this yamaha clutch conversion has been done before by others... google yamaha bantam clutch

Clutch of choice for trials bantams Yamaha yb100 just fits inside bantam chaincase these are available commercially at a price.
Bill

Nigel,
Smart conversion, neatly executed and should hold the power from the hybrid engine: Any chance of a blow by blow tutorial to installation?
Bill, nice to learn that these things are available to buy, do you have any sort of idea of potential costs involved in doing this modification and where they might be purchased from? I have a feeling there may be some serious interest in this!

Cheers, Trevor

This clutch i first saw at the stafford bike show priced at £160..... a fully finished ready to go item. i have no idea which yamaha clutch that was used , but seems bill has identified it as a yb100. The clutch i used is off the yamaha ybr 125. maybe this is the same size  as the yb100. i have had to trim the basket  fingers back a little,remove some metal from the rear of the basket to allow the primary chain to fit nicely and also remove a little from inside the  bantam side cover to allow this to fit without catching internally.  I also had to make  spacers/shims,Tickle the spline in the middle of the basket  with very small file, recess the basket spline area a little and form a shoulder on the retaining nut to secure it all. I paid £35.00 for the complete clutch, so on reflection with all the fiddling around, £160 is not a bad price to buy ready to go.

Many thanks for that Nigel, your conversion has to be way better than messing around with an all metal job, and one off clutch bodies! I can see a lot of these being retro fitted by the racing fraternity and as you suggest, £160 ready to go is not a bad price, but your d.i.y option is fantastic value, I think you may have started something!

Cheers, Trevor

Hi Nigel
Just measured O/D of YB 100 clutch basket @ 124mm I have not fitted mine but I assume it will be much the same as you I spoke too a guy at Telford offroad show who was selling said clutches but I have lost his card but Jim Pickering of Drayton frames has supplied quite a few he can be contacted on 07850836571. Bill

outside diameter of ybr 125 basket is 118.9mm... looks like it comes up slightly smaller.

Thanks for that Nigel YB100 clutches are becoming hard too source there seem to be more YBR125 clutches on evilbay

Bill