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In 1998 I bought a Triumph Herald 13/60, here you can read about it's restoration and share in a few photo's from it's travels. Please feel free to leave comments to any of the posts, of even email me if you want to.

Thursday, October 2, 2014

Propshaft for Overdrive Gearbox

Recently I have fitted an 3 rail, D-Type overdrive gearbox to my Herald. As the Herald never had this as a factory option, propshafts of the correct length are not that plentiful. This is not too difficult to overcome, though it may make a big dent in you wallet if you buy one from one of the Triumph traders, or maybe a little cheaper if you have your existing propshaft shortened professionally.

Before I considered doing the overdrive conversion I had bought a propshaft off eBay, it was advertised as a being suitable for a Herald and having a sliding joint, which I consider to be preferable to the solid or strap type that are more common. However when it arrived it was far too short, so short in fact I couldn't find out what it could have been used for.

The ideal propshaft length for a Herald with a 3 rail O/D gearbox is 46.5", the closest one in the small chassis family is from a Non-O/D Vitesse at 47". Many people use these without modification, though some have to put a spacer on the engine mounts to move it forward to allow for it being slightly too long. I had picked up one of these propshafts cheaply so used it initially, but whilst it did fit I wasn't happy with how tight the whole thing was, even with the engine pushed forward, this also affected clearance between the fan and radiator, which were closer than I liked.

So I now had a selection of propshafts, two too long and one too short. Being too mean to buy the correct one or send one off to be shortened, I decided to make one of the correct length myself from the original solid Herald item and the very short one with a sliding joint.

The two donor propshafts
First thing was to remove sliding joint from the propshaft that was too short, this is easily done using an ultra-thin cutting disc on a grinder. Once this was off I offered it up to the propshaft which was too long to see how much I needed cut off, then again with the grinder I cut off the excess.

Sliding joint and cut down propshaft
Next I took the sliding joint to a local retired engineer who was able to machine down the rough cut I had made to a perfectly flat face. Unfortunately he didn't have any machinery big enough to level off the mating face of the propshaft, so instead I levelled off the rough cut on a belt sander, then using a file and a set square I carefully filed and measured, filed and measured until I was happy it was square.

Measuring the squareness of the propshaft
Then I drifted on the sliding joint on to the propshaft, it was a tight fit, ensuring it was a nice flush fit all round, then double checked the length to ensure it was what I wanted. There was 1.5" of movement in the sliding joint and the 46.5" fell right in the centre of the travel, just as I wanted.

Sliding joint drifted on to the propshaft
Once I was happy the fit and length were good, I put 4 tacks of weld to hold it in place. Before fully welding I used a cutting disc to create a V-shape at the join, this allows the weld to get deeper in to the joint so adds strength.

V-Shape where sliding joint meets the propshaft
Then using a nice hot weld and slow wire speed to ensure it pulls right in, I fully welded around the join.

Joint fully welded
Then using a soft disc I cleaned up the weld.

Weld on the joint cleaned up
Finally I gave it coat of paint before fitting.

Propshaft painted and ready to fit

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