C: Clutch Ball bearing clutch pushrod device..

[BigEd]

You've hit the nail right on the head, Norman. What is needed is a clutch pushrod with the same coefficient of expansion as aluminium. My limited engineering expertise would perhaps suggest Dural with bonded on hardened tips, but this is only an idea. How does Titanium behave when heated? Cheers, Stu.

Just had a quick look on t'internet coefficients of expansion. Aluminium, depending on the grade is roughly in the 20's and Titanium 8-9.5.
Some pushrod OHV engines have hollow aluminium pushrods with steel at the ends for either a ball to fit in a follower or threaded for tappet adjustment. I think maybe AJS/Matchless singles were like this. Your suggestion of aluminium with steel tips would surely help to keep differences in clearance due to expansion to a minimum when things warm up. Anybody tried it?

 

[tatty500]

Just had a quick look on t'internet coefficients of expansion. Aluminium, depending on the grade is roughly in the 20's and Titanium 8-9.5.
Some pushrod OHV engines have hollow aluminium pushrods with steel at the ends for either a ball to fit in a follower or threaded for tappet adjustment. I think maybe AJS/Matchless singles were like this. Your suggestion of aluminium with steel tips would surely help to keep differences in clearance due to expansion to a minimum when things warm up. Anybody tried it?

How about this?

Since most other boxes have their mainshaft positioned by the bearing at the kickstart end, allowing it to move through the output sleeve gear as the case heats up, most of the aluminium parts are removed from the equation. Now, with the twin mainshaft anchored at the primary end maybe if the abutment for the cable outer were moved over there too, the aluminium again can be removed from the system.

Now you all think I really am nutty....go on admit it.

Tatty

 

[vibrac]

You've hit the nail right on the head, Norman. What is needed is a clutch pushrod with the same coefficient of expansion as aluminium. My limited engineering expertise would perhaps suggest Dural with bonded on hardened tips, but this is only an idea. How does Titanium behave when heated? Cheers, Stu.

sounds like a job for arrow shafts

 

[clevtrev]

Sorry to be a dumbo but give more clearance where? Longer pushrod? Tighter clutch lever adjustment? Using Normans brilliant thrust bearing mod mine engages first silently when cold but when hot engaging first from neutral the clutch drags. Hugo.

The bushes in the sprocket need to have about 5 thou removed from the face.

 

[Michael Vane-Hunt]

Just had a quick look on t'internet coefficients of expansion. Aluminium, depending on the grade is roughly in the 20's and Titanium 8-9.5.
Some pushrod OHV engines have hollow aluminium pushrods with steel at the ends for either a ball to fit in a follower or threaded for tappet adjustment. I think maybe AJS/Matchless singles were like this. Your suggestion of aluminium with steel tips would surely help to keep differences in clearance due to expansion to a minimum when things warm up. Anybody tried it?

Do you mean this type of push rod? Lots of the Vancouver section use these on high mileage bikes, think Robert W

. This rod broke in Medora, North Dakota. Push rod was from Chris Klep's Egli and happened on our way home from the Minnesota NA Rally. Cause of breakage not sorted yet. I suppose you could use something like this rod as a clutch push rod.

 

[timetraveller]

The thing to remember about the clutch push rod, as opposed to the valve operating push rods, is that they cannot have a diameter greater than 7 mm When I designed this mod and sent our the first few they all had 7 mm diameter silver steel push rods. The idea was that the 7 mm was a nice slide fit in the main shaft and this stopped any tilting, however small, of the push rod in the gear box main shaft. Those of you familiar with the original design will realise that there is a small brass or bronze bush just inside the clutch side of the gear box main shaft. This has an internal diameter of 0.25" (6.35 mm). This had to be knocked out to allow the 7 mm push rod to be inserted. This was stated quite clearly in the instructions sent out but the Spares Company had enough trouble with people who did not read, or could not cope with, removing this bush that they asked me to make all future items the 0.25" diameter of the originals. The most recent 200 to 300 units have all been like that.
Regarding clevtrev's remark about taking something off the bushes in the centre of the clutch sprocket; I'm not sure how this would help if it is a problem of differential expansion but I would be happy to learn.

 

[Bill Thomas]

The bushes in the sprocket need to have about 5 thou removed from the face.

I think a lot of the trouble is the shoes flinging out, Because the slower the tickover the better ?.
There is so much lift on the standard clutch, I don't see the outer plate as the fault. Cheers Bill.

 

[Simon Dinsdale]

I think a lot of the trouble is the shoes flinging out, Because the slower the tickover the better ?.
There is so much lift on the standard clutch, I don't see the outer plate as the fault. Cheers Bill.

Bill is correct. The problem occurs when there is any clearance between the tip of the shoe plunger and the clutch plate carrier pins. This allows the shoes to rock slightly and if there is a slight drag on the primary plate part of the clutch it allows the plunger clearance to be taken up and the shoes can sometimes rock enough to contact the drum and that causes extra drag.
My clutch has the plungers just resting on the pins so no clearance and it goes into gear without any noise and changes gear on the move with no problems, hot or cold. That is with the std primary plate lifting setup, no mini valve etc.

Simon

 

[timetraveller]

I think that Bill makes a good point. I did not know until a few years ago that Vincents used to balance their clutch shoes to help them to free off at high revs. Has anyone ever tried this. I imagine that quite a lot of lead is required in the one which has the pivot near to one end.

 

[stu spalding]

I think that Bill makes a good point. I did not know until a few years ago that Vincents used to balance their clutch shoes to help them to free off at high revs. Has anyone ever tried this. I imagine that quite a lot of lead is required in the one which has the pivot near to one end.

Paul Zell reported an improvement in the gear change after balancing the clutch shoes. Cheers, Stu.