Clutch Centre Bush clearance

Needing a new clutch centre bush for my sswc motor I asked Dave to make me some.
I am using later 4 plate steel centred bronze type, with custom hardened steel washer behind, needle roller thrust bearing and 4 plate splined shortened centre up front .

He is suggesting making a ground hardened steel "top hat" instead.
Hmmm......, not sure says I. P.B bush tried and tested, but does seem to wear out quickly and the clutch centre tapers out.

I did get some replacements from UK sources, but these either are all poor fit and solid bronze. So might squash up when clutch centre nut tightened.

So, my question is; having looked everywhere for clearance specs. Does anyone have a recommended O.D size or clearance ?

hi john

we mainly throw away the cast steel centre/ machining up a new top hat, out of bigger dimesions, then making a much thicker boss to be riveted to the sprocket, this is then finish machined to the sprocket to take a Torrington needle bearing, with a needle thrusts either end - 1.5 inch at the back that is the one sitting on the top hat, of the clutch and 1 inch behined the splined clutch centre to control the float, we then fit a small 3/4inch needle thrust using a stop hat, that is hollow machined soft that locates into a small hole bored into the end pusher/drive plate.

out of interest these are all made soft very accurately machined, the bearing run on std hard sleeves that can be purchased for pennies that are then pressed onto the top hat to run the clutch on, takes out all the work for hardening/grinding problems.

Always seemed to work, but in the rush to get things done for the practice day the only thing we did not fit and the pushrod did fail - this has now sorted with a new set up for this engine,that has been modified and changed to as explained here.

hope your well would still like to see a close up photo of the clutch centre with spline as asked for on my previous quote.

Problem with my last post / wave or carburation issue caused through- the piston uncovering the bottom of the exhaust port at top dead centre, NASA developed and do a repair paste that can be mixed with aluminium or cast iron 30% that has all suitable chemical temp, shock resistance to be suitable to repair the exhaust port of an internal combustion/gas turbine /turbocharged diesel engine, and be durable, its operating range is -300f to 1000c or 3000f "wow "I will see if I can order some tomorrow, I hope it arrives in time.

any one got any other suggestions:- for a product that is available in the uk

kind regards Derek

That sounds good, but still begging the question of what clearance you have between the outside diameter of hardened sleeve and inside of new back top hat ?

sorry gremlins got it first !

hi john

the other side "my friend"

bearing tolerance on diameter side clearance 0.002 /0.003 thou

The old clearance values are not any good for racing ,switch it to metric and its perfect.0.02mm -0.03mm the tighter you can run the longer it lasts.
regards Dave

Hi Dave

good to see you posting again

- did you get those extra gears and ratio's figure in the end ?

John the clearence I gave are not for bronze they are needle rollers thrusts and roller bearings, I changed to this as we found bonze type seemed to change every time we stripped it, and there was wear.

so much easier to pope out an old one and stick in a new purchased one rather than having to have a lathe to remanufacture bespoke each time the bearing is changed.


regards Derek

derek this is the inside

Hi John you trying to frustrate me ! - not that picture the other photo of the first itm on the other side. please!

I have a;lready seen thes two pics on here, ? I WAS HOPING TO LOOK AT HOW YOU HAVE MATED THE CENTRAL spline piece to the inner drive not the outter clutch body.

but i'm still very impressed with what you have done with this.



regards Derek

The centre mushroom has a wire cut spline and a T shaped nut that holds it onto the mainshaft

Hi John thanks

what about a pic a little furthur away, so we an see a close up - but of the whole thing. but the same shot not any other view

the machining on this looks like a mission with the lightening thats gone on, credit looks a great job,

is it steel or alloy or is the center piece a different matereial to the outter it looks this way, but my be an elusion.

kind regards

Derek

John i use on 001 std bsa bronze/steel insert bush (dont recall changing one ever?) Yes its worn but thats a good thing - no clutch drag! I always grease it up before a meeting. 003 has a 3sp top hat bush and no bearing and works just fine!

Regards Mike

Insert is steel and only minimal machining to clutch centre ribs to clear mainshaft nut

Mike, I am amazed you have rarely changed the bush.

I was thinking my worn bush was causing the clutch basket to wobble around and contribute to repeated primary chain failure.

My ss wc 125 motor eats primary chains in 4 hours.

Tried new sprockets/baskets, both perfectly aligned; < 500mls different good gearbox oils, different chains: JWIS/DID/Renolds/Tsubaki.
Things that have worked fine before in other engines.
Seems chains are locking up, DID was every 2 links, like they are over heating.

Hey derek,

When you have your clutch apart can you show us a picture of the back and new top hat / bearing setup ?

Thanks

Hello John,
Went to my favorite helpful bearing shop in Perth yesterday, looking for torrington needle bearings with a correct 5/8 inner diameter and 7/8 long ,no go not in Australia which is not a big problem.Scoured the internet for alternate manfuactures and sizes but with only semi success ;the best length I found was 3/4 inch long.
Also I would prefer to use a slip ring on the shaft so it could never get ruined by the needles rollers also the same as my Kawaski setup.I will press on and start manufacture of the new bearing holders as the finish needle bearing diameter can be done later.
Derek ,whilst you have your clutch exsposed taking pictures from every angle ,can you record your bearing numbers .
thanks Dave

think ist on here somewhere ? but will do, Like Mike said some have no issues here, But Ihave seen a set up in Bronze that Tom Locked up infron of me - it was unberleavable "no wobble - no movment and ran perfectly free I could never duplicate it so whet to proper bearings, DAD even made a lap to lap the centere parallel that the bush sits in as when it wears it wears tapered, never made any difference, clearly some evidence here of "Tom Knows the secret so just ask him"

I seen mikes stripped and he is telling the truth, it wobbles but I agree with John wobble creates more drag - well this could be debatable
as 1) with surflex friction plaste its worce
2) but not with all stell - does not seem to make any diffeence.

what do you think Mike ?

John you deffernatly have an issue with primary chains 4 hrs?? - something must be wrong Robbies chains are bullet proof.

I will get some more photos when I strip it again but not sure when this will need to happen not soon I hope, Iam running surflex in one engine and stell in the other engine.

Kind regards (

Derek Betts - p.s. (im not planning on surfing again till later this afternoon and it wont be on here but in the water see you all monday)