Crankshaft repairs

[Alan Waddington 2Participant @alanwaddington2]

Started restoring an old Velo engine today……pulled the crank apart and it’s in a pretty sorry state. As far as i can make out the Timing and Drive side shafts are not available as spares, so aside from searching for another crank i reckon there are two options.

1- Try and repair the original shafts (which are ravaged by rust to varying degrees.) This would probably mean building up with weld and then turning/threading back to spec.

2- Attempt to make two new ones from scratch.

A web search reveals that veloce made the shafts from 3% Nickel Steel whatever that is ?

What do you reckon ?….Thoughts on a postcard please

[Alan Waddington 2Participant @alanwaddington2]

[Anonymous]

Doesn't look that difficult to make new ones, mostly turning and screwcutting with some keyway milling. Try using EN36, a 3% nickel case hardening steel, which would be a useful characteristic for a crankshaft

[Mike PooleParticipant @mikepoole82104]

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

[Alan Waddington 2Participant @alanwaddington2]

Posted by Andrew Johnston on 05/08/2018 22:21:14:

Doesn't look that difficult to make new ones, mostly turning and screwcutting with some keyway milling. Try using EN36, a 3% nickel case hardening steel, which would be a useful characteristic for a crankshaft

Mmh i would agree that on the face of it making from scratch looks fairly easy, but the tolerances need to be quite tight, the shafts are a press fit into the crank, with no shoulder to press up to.

Supposedly tapered 8 thou per inch, however when i quickly measured them today i didn’t find any evidence of that, although due to the condition they're not the easiest things to measure accurately.

[peak4Participant @peak4]

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

[JohnFParticipant @johnf59703]

Hi Alan, I would make new and suggest EN24T condition T is in the heat treated condition but still machinable, very tough material and should be ideal for the situation. Depends on what machine you have to decide on the best tooling HSS or carbide, coolant or not.

I see you have pressed them out of the flywheels, what did you use? Whatever it was it should be capable of pressing new ones back in and you can get a good measurement for this from the originals by the look of your photo.

Maybe to Velo club or a member will have drawings or maybe someone will come to your aid with a good crank you can measure up, even so I think you should be able to obtain suitable measurements from your old ones, most sizes will probably be a nominal imperial size or you will know what they are to fit into.

[ronan walshParticipant @ronanwalsh98054]

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.

[HopperParticipant @hopper]

With all the cottage industries serving the vintage bike scene these days, I'd keep looking around for replacement parts. There must be some out there somewhere, or somebody making them. What model Velo are they from?

Edited By Hopper on 06/08/2018 01:57:21

[thaiguzziParticipant @thaiguzzi]

Posted by Hopper on 06/08/2018 01:56:45:

With all the cottage industries serving the vintage bike scene these days, I'd keep looking around for replacement parts. There must be some out there somewhere, or somebody making them. What model Velo are they from?

Edited By Hopper on 06/08/2018 01:57:21

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.

[Alan Waddington 2Participant @alanwaddington2]

Posted by Hopper on 06/08/2018 01:56:45:

With all the cottage industries serving the vintage bike scene these days, I'd keep looking around for replacement parts. There must be some out there somewhere, or somebody making them. What model Velo are they from?

Edited By Hopper on 06/08/2018 01:57:21

The crank is from a MK1 KSS, 1934, Not a model particularly well served by the vintage Velo industry. Plenty of MK2 stuff to be had. The shafts are not even shown as individual spares in the original Velo parts manual of the 30’s, they were supplied complete with the corresponding crank half, already pressed in.

[Alan Waddington 2Participant @alanwaddington2]

Posted by thaiguzzi on 06/08/2018 06:25:42:

Posted by Hopper on 06/08/2018 01:56:45:

With all the cottage industries serving the vintage bike scene these days, I'd keep looking around for replacement parts. There must be some out there somewhere, or somebody making them. What model Velo are they from?

Edited By Hopper on 06/08/2018 01:57:21

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.

Agree the aftermarket scene for 60’s Velo’s is huge, not so big for pre war machines. Also those lovely aftermarket cranks you mention are generally full units, splendid things indeed but ££££

[Clive FosterParticipant @clivefoster55965]

Agree that making new ones is quite practical. One nice thing about Velos is that all the taper fits are largely self gauging. Final position is flush with the inside end so if the initial insertion distance is correct the press fit will be too.

Be wise to verify the size of the hole in the crank webs as such have been known to stretch over the years leading to inadequate grip. Classic example of this is the BSA Gold Star which has a plain shaft with almost no nip held in by a riveted flange. Fine on the cooking M series, B 31 and B32 but frequently hammered loose by the more powerful B32 and B34, especially D series and especially if the RR gearbox is used on the road.

Fortunately opening up plain taper a touch to restore roundness is nearly trivial.

If you intend to press it it with an ordinary press you will need a proper guide tube to keep the thing dead straight. If it cocks slightly it will stay cocked.

Back in the day the butcher brigade were known to advise welding in place. Which works, or rather doesn't work, about as well as similar efforts on Goldies.

Clive.

[ronan walshParticipant @ronanwalsh98054]

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.

[duncan webster 1Participant @duncanwebster1]

I wouldn't even think about welding, the heat would do all sorts of unpleasant things to the base material. You would still have a lot of machining to do, make some new ones. As others have said, EN24 is probably a good start, not quite as strong as EN27 (3% Ni) but I doubt that would be a problem, at least you can get hold of it fairly readily

[Alan Waddington 2Participant @alanwaddington2]

Thanks for all the suggestions, reckon i may as well have a go, no point in having the machinery otherwise……….need to find a supplier for the main bearings first though, which at a quick glance are roughly £100 a piece

[Tim StevensParticipant @timstevens64731]

ronan – One-off or even ten-off manufacture is very time-consuming – just ask others on the forum who have been doing it for years. Therefore we have to expect rather high prices. These shafts are not something you can knock out in an afternoon on a Myford – they involve things like heat treatment, & cylindrical grinding, so even if you only need one of each I bet you need two or three material blanks to be sure of getting it right.

I'm sure a web-search on Velocette Owners Club will prove rewarding. And if it is, please join. They can only provide a service if they have money to do it. Worth every penny.

Cheers, Tim

[John MCParticipant @johnmc39344]

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

[ronan walshParticipant @ronanwalsh98054]

Posted by John MC on 06/08/2018 17:53:07:

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

I really hope Alpha comes back, i did hear that Max Nightingale died suddenly and was wondering if the firm would continue work. As for serious engineers making spares for old bikes, its a difficult one as most people into old british bikes are getting on in years, as are the engineers. Also i think a lot of people are buying old bikes now for investments, and not to ride, which is a pity.

[ronan walshParticipant @ronanwalsh98054]

Posted by Tim Stevens on 06/08/2018 15:18:02:

ronan – One-off or even ten-off manufacture is very time-consuming – just ask others on the forum who have been doing it for years. Therefore we have to expect rather high prices. These shafts are not something you can knock out in an afternoon on a Myford – they involve things like heat treatment, & cylindrical grinding, so even if you only need one of each I bet you need two or three material blanks to be sure of getting it right.

I'm sure a web-search on Velocette Owners Club will prove rewarding. And if it is, please join. They can only provide a service if they have money to do it. Worth every penny.

Cheers, Tim

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.

[Alan Waddington 2Participant @alanwaddington2]

Posted by John MC on 06/08/2018 17:53:07:

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

John, i was trying to convey the difference in aftermarket spares availability between early and late Velo’s. Maybe i didn’t word it very well. The MK1 KSS gets very little attention, even compared to the MK2, so the aftermarket scene for Viper and Venom parts is huge in comparison.

Yes i think you are correct about the slow taper. The mainshaft bearing is described as having a 1 thou to the inch taper, which is probably why i struggled to measure it from the old shafts. Incidentally that single bearing is £185 + vat

This got me thinking, if im going to the trouble of making new shafts in modern material, then why not modify them to try and improve location. Your solution of adding a head and counterbore had crossed my mind, however i did wonder if this might weaken the crank halves and should they too be remade in EN24t.

if i did go down this route, i wonder if the shafts could be made plain with no taper, just an interference fit and tig welded on the back side, then a more common bearing used, (which should hopefully be cheaper ).

I would be interested on your thoughts.

[ronan walshParticipant @ronanwalsh98054]

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.

[IanHParticipant @ianh]

I have redone the bottom end of a JAP 60 degree twin and used what is now I believe a very well established approach. New shafts are made out of EN36B and then carburised, you leave additional material on where you don’t want the shafts hardened e.g where it is threaded. Then turn these details and send the shafts for hardening, finally the hard surfaces are ground to size. Tapers are abandoned being replaced by press fits.
Ian

[Clive FosterParticipant @clivefoster55965]

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

[not done it yetParticipant @notdoneityet]

Perhaps a shrink fit might be more appropriate in this century? Liquid nitrogen is relatively freely available these days.

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