Having removed and rebuilt the gearbox as part of the conversion to RHD, I have just installed a new clutch cross shaft in the RHD position.
Following installation of the shaft I noticed that the release bearing is not concentric with the first motion shaft. The distance from shaft to bearing is 5.7mm on the left but only 2.7mm on the left side. see pics.
Thinking that the new shaft was not accurately made (my doubts were raised because this is the second new shaft, the first being taper drilled in the wrong direction, so was returned). I removed the shaft to compare it to the worn original.
Both shafts measured very similar, the critical distance (for release bearing position) from taper pin hole to locking bolt groove differs by only 1.5mm.
My question is, has anyone else noticed this same issue and will the release bearing being offset affect smooth clutch operation? Views and opinions welcomed.
Just had my clutch rebuilt (see picture). It is in the horizontal direction absolutely in the centre (the bearing has dropped a bit to the front on the photo, but in reality also in the vertical direction itās perfect).
Could it be that thereās something wrong with the bolt (CB.131/16D, item F.36 in the XK 120 SPC) that locates the shaft at the RH side (for LHD cars) in the correct axial position, securing that the fork is exactly in the centre? Can you still move the shaft in an axial direction, meaning this bolt is perhaps incorrect or damaged? Youāre looking for only 1.5 mm in order to get it right in the center.
I donāt think that the complete fork will be distorted although you can check of courseā¦
There is some normal misalignment in the vertical as the fork moves in and out, which does not create a problem.
By any chance do you have a spacer or washer on the shaft where it is not supposed to be?
Horizontal misalignment is clearly poor manufacturing of reproduction parts, unfortunately something weāve seen before now.
Everything seems to be assembled correctly, there is a spring washer on the shaft next to the lever as usual, but actual location is dictated by the bolt which passes through the machined groove in the shaft and allows the shaft to turn. All parts are original, fork, bolt, spring washer. Only the shaft is new but strangely it is very close in dimensions (1.5mm difference) to the old (original?) shaft.
I am just wondering if I am alone with this misalignment or has it been noticed before and more importantly will it affect clutch operation?
Rob,
Yes the shaft is indeed ambidextrous, the reason I changed the shaft was that a previous owner had made a modification (see pic).
Presumably the modification was made due to lack of parts ie a taper pin, so the lever had been brazed to the shaft and part of the shaft and lever ground away - resulting effectively in a brass taper pin plus a brass crosspin on the end.
An ingenious solution but not one that I wanted to rely on.
Interestingly when my son and I first removed and examined the gearbox (in LHD format)
Sorry I did not quite complete my last postā¦ (fatfinger!)
Interestingly when my son and I first removed and examined the gearbox (in LHD format) I noticed and did remark to him that the release fork was not central - and that was with a different shaft and a different fork to the ones now fitted! Hmmm.
Interestingly, I have exactly the same problem! I purchased a new shaft, fork and bearings and when I assembled them I found that the yoke was not central in the hole in the bellhousing. I decided to get the later XK150-type shaft with the parallel, rather than tapered, pins. Iāve read that this is a stronger design and less likely to snap (both the old ones had snapped). When I measure from the edge of the yoke to the edge of the hole I get 3.5mm on one side and 8mm on the other.
Iāve been advised that this is not going to cause any problems (after all, the release bearing is not centred vertically throughout its operating arc, and itās just a rubbing graphite ring rather than a ball or roller bearing) but it still offends me a bit!
The easiest way out of the problem that I can see would be to machine another groove in the opposite end of the shaft and use the locating bolt on that side. There is an unused mirror-image hole there.
So at least I am not alone! I appreciate what you say about the release bearing also moving in the vertical plane during use, so maybe the horzontal discrepancy is just a perceived rather than real problem, fingers crossed.
That is a good idea ref moving the groove to the other end, I will file that away for possible use in the future.
Same source as you, though I am not suggesting the shaft is at fault as apart from 1.5mm difference already mentioned it is identical to the old one I removed.
Mine came from them, too. I was thinking, another way to tackle the āproblemā (if indeed, it is one) could be to take a little bit of the inside of the yoke on one side, and put a packing washer(s) on the opposite side to centralise thingsā¦
Have you tried assembling it as a LHD and see if it has the same problem?
Looking at all the parts involved, I think the one most likely to have a machining error would be the yoke, which is supposed to have the locating bolt hole 3/4" offset from the centerline of the yoke arms, but that might be a little bit off.
It would have made things so much easier if they had put it in the center, with a through bolt and nut. I wonder why they didnāt. Just using it the way they got it from Standard in the 1930s I guess.
Tony, sorry to be revisiting your old thread, but Iām building up my gearbox ('55 140DHC), and am now installing the clutch mechanism. Iāve gone with the later 9.5" clutch, but am using all 140 parts with the exception of the deeper release bearing.
I have the same issue with the bearing position a you. Mine is around 5mm offset on the shaft to the right (of the car, left in the photo). I have the shaft and the fork from Coventry. As itās a carbon block type, I rather doubt it makes any significant difference, but Iām interested to know what the consensus was following your experiences. Did you do anything different? I donāt really fancy trying to pack things out etc.
I have the original fork and shaft assembly from my car, which does look to be steel. Interestingly Iām assuming they are original, but the fork and lever are retained by parallel pins (not tapered), which are quite long and have full hex heads with a hole for a lockwire. I donāt think these parts have been changed for 150 parts, but the trunnion on the end of the lever has a screw in the end of it as well which makes me wonder. I did think about using these parts instead due to the discussions around materials (judging by the surface rust, the fork is steel), but the old fork is of thinner construction than the Coventry bronze alloy item. More worryingly, as Jim noted in his video when assembled and tightened up the fork can still move a very small amount on the shaft as the parallel pin has no way of tightening futher in the aligned holes. I tend to think the Coventry item is a better design, but the jury may still be out on the materials. As itās the diaphragm 9.5" arrangement I know the pressure on the components will be less than on the original.
So basically, did anything further come of this discussion?
Roger
Forgot to mention - I did do a dummy assembly as LHD as Rob suggested, and got a mirror image of the āproblemā. This might well be an issue if it applied to my Mustangās SN95 clutch release, where the bearing is designed to run lightly on the clutch diaphragm fingers all the time, but given the way the ancient carbon block system operates Iām really not sure a slight lateral misalignment is a problem.
Without addressing every aspect youāve mentioned, I just wanted to let you know that also my Clutch Bearing is (a bit) out of centre, although far less than 5 mm.
On the other hand, have you looked at the movement that occurs when the fork is moving front and back? The movement of the fork is in fact a radius and thereby creates a lateral movement over the carbon, although in this case a vertical one whereas you talk about a horizontal movement due to your fork being out of centre.
The general consensus seems to be that the release bearing moves off centre in the vertical axis anyway, so a small amount of misalignment horizontally should work OK.
And it does seem to be OK, so far.
We (son and I) managed to drive the car round the block for its 70th anniversary - though that is the limit of testing as we now have an engine issue (never assume that a shiny painted engine is as good on the inside as it looks outside!).
In summary, if everything is tight (no lost motion) I would continue the build.
I would add that I have since purchased a beautifully made release fork from Crossthwaite and Gardiner as used in their C and D type rebuilds - that is an alternative source of supply. Now in the spares box for possible use in the future.
Thanks both - yes, Iām assuming there is always going to be some change in contact between the two surfaces, so a little bit of lateral misalignment isnāt the end of the world. To me a tight fit of all components is the principal concern as any movement at all will lead to fretting and subsequent wear.
Iāve seen the C&G fork, Tony, and was tempted, but decided to stick with the Coventry offering because I think it helps if all the parts that fit together are made (or at least sold) by the same supplier, as this way machined surfaces should match (e.g. tapered pins etc.). That said, C&G do make the tapered pins as well but I didnāt see the shaft on their website - but didnāt look that far. I could phone Tony to ask - I have a lot of C&G parts in my engineās timing gear, and as you might expect they are made to a very high standard.
As I noted above, I have the same slight misalignment issue. However, I was told by a well-regarded and very experienced engineer specialising in old Jag transmissions not to worry about it. It wonāt be a problem.
