C: Clutch Ball bearing clutch pushrod device..

[ericg]

I have one of Norman's thrust race kit fitted to my Norvin and it's worked very well for the last 20000 miles.

 

[Goffy998]

I had one made up similar to the Mini valve arrangement which seemed to make a difference. I then changed it for one of needle roller versions from the VOC which works no better or worse. I didn't really have a problem with the plate opening at an angle so I didn't expect much improvement. First engages silently from cold - hots another matter.

 

[clevtrev]

I had one made up similar to the Mini valve arrangement which seemed to make a difference. I then changed it for one of needle roller versions from the VOC which works no better or worse. I didn't really have a problem with the plate opening at an angle so I didn't expect much improvement. First engages silently from cold - hots another matter.

Because when your engine gets hot, you`ve taken up the clearance of the centre. Solution, give more clearance.

 

[Hugo Myatt]

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.

 

[timetraveller]

Thanks for the comment Hugo and also thanks for the feedback. It is only with feedback from a variety of users that one can improve things. My guess, and I emphasise the 'guess', is that these symptoms could be caused be the aluminium crank case and gearbox housing expanding with the heat more than the clutch pushrod. I will do a very simplistic calculation. Suppose that the difference in the coefficient of thermal expansion between aluminium and steel is 10 parts in ten to the minus six per degree Celsius. Further suppose that the length is 10 inches and that the temperature difference is 100 degrees C, almost certainly too much. Then I make it that the differential change in length between the aluminium castings and the steel components could be as high as ten thou. Remember that Vincents found it necessary to make the length of the battery carrier tube adjustable to aid gear changing because of temperature changes. That way there might not be the same lift when hot as when cold by ten thou, if I am correct, and it would be good if someone can check that figure. I can think of two ways to overcome this, if it is the problem. One would be to ensure that there is the absolutely minimum of clearance when cold so that the ten thou increase keeps the clearance down to an acceptable value. Then there is the alternative of using the Clubs slightly modified lifting components, which have been found necessary with the multi plate clutches. An aluminium push rod might work but I would be wary of wear between that and the lifting lever G91. Remember that the needle roller mod cannot impart any turning motion to the clutch push rod but is sits inside a gearbox main shaft which can.

 

[Hugo Myatt]

Thanks Norman. I will cogitate on this.

 

[greg brillus]

There is some confusion going on here between multiplate and stock Vincent clutches. In a stock Vincent clutch the handlebar free-play boarders on excessive, and mine gives no trouble when hot, but if the clutch drags when hot if a multiplate is used, then this I can understand, as my unit construction Triumph did this, and I use to adjust the cable adjuster as I was riding along. In that case the free-play increased and the clutch did not lift enough, so by shortening the outer cable this then regained the lost travel, I see this scenario happening with a Vincent of unit construction as the heat spreads from the engine to the gearbox. So Trevor's answer makes no sense to me, so on a cold engine and with a multiplate you need almost zero freeplay at the handlebar lever, and this free play increases as the engine heats up, thus the slight loss of lift causes the clutch to drag. However.......... With the multi's on a cold engine, the drag is quite high due to the stickiness of the plates in an oil bath........But as the engine is running and warmed up, this oil is thrown out centrifugally, so then the clutch does not drag anymore.......In theory, anyway..........Think about it.

 

[tatty500]

How does that thrust bearing set up get any lubrication, or is it meant to run dry. I would like to come up with a change to the ring/spring plate to make adjustment of the springs possible, like most other clutches. But I think the design makes that quite difficult.

Greg,

Apart from the slight twist of C13 on the big nut C20, all the parts are rotating together with the mainshaft. Loctite might be a good lubricant for the race!

The rubbing takes place at the other end, and might be needed to stop the parts so that first might be engaged quietly.

Too much travel can cause a spring to become coilbound in my twin. This can tilt the plate with the standard set-up....so more slack is better with the proviso that when stinking hot in traffic there is sufficient movement left.

Tatty

 

[stu spalding]

Thanks for the comment Hugo and also thanks for the feedback. It is only with feedback from a variety of users that one can improve things. My guess, and I emphasise the 'guess', is that these symptoms could be caused be the aluminium crank case and gearbox housing expanding with the heat more than the clutch pushrod. I will do a very simplistic calculation. Suppose that the difference in the coefficient of thermal expansion between aluminium and steel is 10 parts in ten to the minus six per degree Celsius. Further suppose that the length is 10 inches and that the temperature difference is 100 degrees C, almost certainly too much. Then I make it that the differential change in length between the aluminium castings and the steel components could be as high as ten thou. Remember that Vincents found it necessary to make the length of the battery carrier tube adjustable to aid gear changing because of temperature changes. That way there might not be the same lift when hot as when cold by ten thou, if I am correct, and it would be good if someone can check that figure. I can think of two ways to overcome this, if it is the problem. One would be to ensure that there is the absolutely minimum of clearance when cold so that the ten thou increase keeps the clearance down to an acceptable value. Then there is the alternative of using the Clubs slightly modified lifting components, which have been found necessary with the multi plate clutches. An aluminium push rod might work but I would be wary of wear between that and the lifting lever G91. Remember that the needle roller mod cannot impart any turning motion to the clutch push rod but is sits inside a gearbox main shaft which can.

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.

 

[Bazlerker]

Ahem.....is there no one about who has tried the device and comment as to its efficacy, before we get into a discussion on coeffecients of thermal expansion?