Gearbox taper pin sheared

[ronhatch]

Hi all, I decided to change the seals on my TR4 gearbox, when removing the taper pin from the clutch fork ( my dad used to call this the troddle arm, anyone heard of that?) I found it had sheared so I ordered a new uprated one but I can't get the sheared part out. I was going to try vibrating it out but has anyone got any other ideas ?

Regards

Ron

[RogerH]

Hi Ron,

is it possible to drill the back of the fork above the end of the pin and then tap it through.

 

if the fork doesn't come off with the pin stub insitu you may have to cut the cross shaft.

 

When re-assembling make sure the new taper pin/firk/shaft fit together very well AND use an extra roll pin etc at 90' to the taper pin.

 

Roger

[Geko]

yes, cutting the cross-shaft and replacing with a new one. I don't think there's another option.

Edited July 4, 2014 by Geko

[ronhatch]

I'm in no rush at the mo so before that drastic action I am going to fill the hole with release oil or something else to thin the oil/grease and then try to vibrate it out ( what with I haven't figured out yet, but probably with an air tool )

Then if not out with the grinder, I'll let you know

Regards

Ron

[ronhatch]

Is the pin a "snug" fit ? and what is the roll pin for?

Regards

Ron

[Motorsport Mickey]

The roll pin is an extra fitment that runs across the line of the original taper pin fitment. This puts the fork into double shear splitting the loading and preventing the breakage of the single pin fitment.

 

Mick Richards

[Fireman049]

I had the same problem with my 3A. I had to cut the cross shaft and fit a new one. I also fitted a roll pin.

 

Tom.

[RogerH]

Hi Ron,

in theory the pin is a very snug fit - hence it being a taper pin.

I don't think you will vibrate it out - nobody else has succeeded yet.

 

See if you can get access to the top of the fork to drill a hole above the pin and then knock it down.

 

Roger

[AlanT]

Don't think you will shake this out with vibration.

 

Your best bet to avoid cutting the shaft is some kind of drilling out method.

 

Maybe one one these would help get to it:

https://flic.kr/p/i6QCas

[Kiwifrog]

 

See if you can get access to the top of the fork to drill a hole above the pin and then knock it down.

 

Roger

 

Thats how I did mine take it slowly and try and rotate the shaft as much as possible to make it easier, its bloody satisfying when it goes right and quite simple

 

Cheers

 

Alan

[ronhatch]

Hi all, I will give it a go with the vibro method but it sounds unpromising then I will attempt the drill method but I can't figure out where the roll pin fits, is it in the fork, the shaft or the bearing. the drawings are vague in the books, I need a "light bulb" moment.

Regards

Ron

[Motorsport Mickey]

Ron,

 

Check your PM for help from "Osram"

 

Mick Richards

[peejay4A]

Here's a roll pin fitted. Doubled up cross shaft bearings too.

 

Edited July 4, 2014 by peejay4A

[RogerH]

Hi Ron,

have a look at Pete's Pic.

The black dot in the middle of the fork is a roll pin that goes through the fork and the shaft. This is normal way to help support the taper pin.

You could use a nut and bolt but they tend to have slack in them and that defeats the object.

 

As Pete states - double up on the bearings on the end of the shaft. You can see them just protruding.

 

Roger

[ronhatch]

Aha, picture paints a thousand etc. now I see why I couldn't find It ! understand the principle now

Thanks all

Regards

Ron

[Guest ntc]

Hi Ron,

is it possible to drill the back of the fork above the end of the pin and then tap it through.

 

if the fork doesn't come off with the pin stub insitu you may have to cut the cross shaft.

 

When re-assembling make sure the new taper pin/firk/shaft fit together very well AND use an extra roll pin etc at 90' to the taper pin.

 

Roger

Roger is correct I have done many times and you can do it at an angle

[BlueTR3A-5EKT]

I have successfully drilled from above and tapped out the broken pin from the lever more than once . Cross shafts are a fortune. Still have the forks with the a drill hole in them. I always thought I would pre drill through the top of the fork so I could bang it out if required later in life.

 

Additional cross drilling and adding a roll pin is also a good solution to aid the taper pin.

 

Pete I would say your wire locking was bordering on unlocking, although the pin is never going to fall out even if it come run loose.

Here is a slide show << http://www.slideshare.net/juandigital/how-to-install-safety-wire-presentation >>

Did you fit the release bearing eventually or are we awaiting the "funny noise when the clutch is depressed" thread to start.

Did you fit the roll pin in the release bearing carrier to stop it spinning on the fork fingers? (PtNo DS811) I was told these are critical on cars without external clutch slave cylinder return springs. ie TR4A onwards.

 

Cheers

Peter W

[peejay4A]

Yes Peter I thought that when I took time to study the picture. However I used one of those lock wire tools and the wire is very tight. I'd do it differently next time but if it does move it won't get far and the roll pin is there. The anti spin pin is in place and I did remember to install the relase bearing. All that was around 7000 miles ago when Eric was recommissioned. So far all is well.

[peter.goreham]

Hi,

Interested in part of Peter W's post - ''Did you fit the roll pin in the release bearing carrier to stop it spinning on the fork fingers? (PtNo DS811) I was told these are critical on cars without external clutch slave cylinder return springs. ie TR4A onwards.''

I wonder if you could elaborate on where the advice came from and what it meant by 'critical'.

The reason I ask is that my rebuilt gearbox is ready to go in the car (TR5) and it has no pin in the carrier. The reason it has no pin is that in an email from Pete Cox he told me ''Don't worry about the pin through the bearing carrier (or sleeve). I find it causes more problems than it solves''.

I'm pretty confident of Pete's advice but always interested in the other point of view.

 

Regards

Peter

[BlueTR3A-5EKT]

The advice I stated came from the late Alan Wadley of TR Workshop.

 

His experience related to TR4A/5/250/6 where a fixed length push rod and no return spring is fitted to the clutch slave cylinder - (the self adjusting clutch).

In operation the release bearing may remain in light contact with the clutch cover release forks causing the bearing and the carrier to continually spin together if the stop pin is not fitted.

 

His workshop experience demonstrated the spinning carrier (where no pin was fitted) wore the finger pins fitted in the fork and the groove surface of the carrier which the finger pins act on. Stopping the carrier rotating with the pin made the release bearing do the job it is designed to do - spin when in contact with the clutch cover and release the clutch when needed.

 

Pete Cox's view is perhaps because many owners are now converting their cars to the adjustable push rod and pull-off spring arrangement as used on TR2/3/4, to improve clutch operation and release on 6 cylinder models.

 

My own view is that the anti spin pin is an engineering solution for a problem encountered by Triumph when they went for the self adjusting clutch.

 

Cheers

Peter W

[Guest ntc]

And by the way you can drill and remove the pin in situ,no need to rotate it.

[Tom Fremont]

If the new pin is chamfered under the head it should seat on the tapers ( rather than on the head, which prevents the tapers mating properly ). Many pins lack this step in their manufacture, and doom them to failure.

 

Bedded properly I've not had a failure in my '250s using either the Laycock or Sachs pressure plates. Without proper seating of the tapers the roll pin plays a role; otherwise it's redundant IMO. Moreover, I reckon the original type pin has a higher shear rating than the roll pin.

 

I too double the cross shaft bushings, filling the gap between with wheel bearing grease.

Edited July 8, 2014 by Tom Fremont

[Motorsport Mickey]

Hi Tom,

 

I reckon you're right the standard pin will exceed the roll pin in shear strength, but when the standard pin shears it's not because it's 50% less shear strength then required, it will possibly be maybe a couple of percent the wrong side and that's enough to shear it. The roll pin at the 90 deg fitting puts the force in double shear and gives the standard pin the edge back and enough in hand to resist the shear forces.

 

Mick Richards

Edited July 8, 2014 by Motorsport Mickey

[RogerH]

Hi Tom,

I agree that the taper pin is more than strong enough in shear. The fact that it is supported on one side (single sided shear) does not reduce its quality.

Sadly the taper in the shaft does not always mimic the taper of the pin so the pin is no longer in shear but in tension on one side.

This causes a crack to start on the stressed side and this then propagates rapidly into failure.

 

If the top of the taper pin could be supported then it would be in double shear but more importantly it would have no tensile forces acting on it. ( this is easily done).

 

Roger

[Shuthonger]

I have just reinstalled my gearbox and I noticed that the release bearing has a kink in the groove where the finger pins locate to stop it spinning. This is as it was before removal when it worked perfectly. I have reinstated it as it was. Fingers crossed as it's not coming out again!