Making new is probably the easiest solution but Norman Hyde used a submerged arc welding process to stroke the Trident crank for his 1000cc conversion. The Trident crank is a one piece forging though and minimising distortion was a priority. If you don't feel like taking the job on I am sure the Velo club could advise on a crank restoration specialist. It would be very satisfying to fix it yourself though but cocking it up could total the engine and it would be game over I suspect.

Mike

Whilst I always like the idea of doing as much as possible myself, would Alpha Bearings be able to assist?

I could to with talking to them about Ducati bevel big ends. I understand that the owner has recently passed away, so I don't know the current state of play with the company.

Bill

Alan i will be following this thread with interest, as i am into old motorcycles too. But am more of a BSA and Triumph man, but have lusted after a Velo for years.

I would agree with JohnF, en24t is easily available, very tough, and yet not too difficult to machine. I made a new central flywheel for a Norton commando crankshaft out of it years ago, to replace the original cast iron one, and really liked it.

Also consulting the fabulous book "The vintage motorcyclists workshop" by Radco, he says its suitable for shafts, spindles, connecting rods etc, and has good resistance to wear and shock loadings.

You should have a go at making the spindles, i think i would.

Concur. I'm not a Velo man either (not thru lack of trying – love 'em) but i have seen lots of specialist Velo people in the classic mags.

Hell, not only have i seen 5 speed box upgrades, but 6 speed too. Belt drives, alternator conversions, electronic ignition, and now having thought about it, a guy is building and selling complete engines. So somebody is making crankshafts.

OP just needs to look harder.

To those that advocate going to a specialist parts maker/supplier, i suggest going online and looking at the prices of their parts, excellent though they may be, they are eyewateringly expensive.

Looking at those shafts, there is perhaps £20 worth of steel in them, why not try to make them and if they do not work out, you have lost little. I would have a bash.

OP, are you sure the fit is not the usual Veloce slow taper? Many years ago I repaired a Mk1 KSS crank that had suffered they same as yours. Straight forward turning job, all the diameters can be turned at the same setting ensuring concentricity. What I had to do was bore the holes in the flywheels, both damaged. I bored them just enough to remove the damage and counterbored to take a "head" left on the inner ends of the shafts to stop them pulling through the flywheels. this approach avoids the welding approach. If you do bore the mainshaft holes this must be done with great care, setting up off the crankpin hole, get this wrong and the crank will never true up on assembly.

I believe Alpha are not trading at the moment, hopefully to return soon.

I would disagree with the "aftermarket scene" for post war Velo's being huge. The main supplier is not getting any younger and would like to retire. Anno domini is making itself felt with four other specialists (repairers). Some other classic bike dealers sell the common stuff, the more specialist stuff will become hard to get unless someone picks up the reins, may be the owners club?

Its also been mentioned someone is making complete engines, not quite but I believe that is his ambition. The price will mean that very few will be able to buy these parts.

John

Oh yes Tim, i know all about time consuming engineering work, the amount of people who want a "quick job done for a tenner" who i tell to take a hike is quite large, i do not work for free.

As has been said if En24t is used, then the material is already heat treated, as for the cylindrical grinding, i am not so sure if its necessary in this case, i have access to a cylindrical grinder if i need it, and its very rare i do. I would think fine turning would fit the bill.

I have a crankshaft somewhere from a jawa speedway engine. I would imagine it had to cope with 60hp passing through it. There is no splines, serrations, tapers,rivitted flanges, cotter pins or anything else holding it together. Both the mainshafts are press fits into the crank cheeks, and the big end the same.

Effective though press fits are you need very careful control of sizes and surface finish if full grip is to be achieved. Its very easy to scrape things a touch or even, god forbid, start things slightly out of line initially stretching the hole as the shaft goes in.

Slow tapers give almost identical grip for the same pressing loads but the actual pressing distance is far shorter and they are mostly self aligning. Its much easier to to do a good job.

Testimony to the potential issues with high strength press fits are the various patent expansion techniques, such as the SKF oil injection process, intended to sidestep potential issues with surface damage whilst obtaining the maximum retention forces. The BSA riveted flange construction was devised to allow a light press fit sufficient to carry basic crank loads to be used with the riveted flange handling dynamic peaks and ensuring that the shaft couldn't pull through. As with most complicated efforts failure results in a really sorry mess!

If going for parallel press I'd be inclined to cool the shaft to make fitting easier. But in a normal workshop you have condensation issue to contend with.

Clive