Who’s had one twist?

[byron]

I bought a 60mm AF "race" crank that had only done about 500 gentle miles on a 175 kit. it was well twisted. it didn't matter as I only wanted the webs.
whereas I have been caning a MEC on my Mugello 186 for 000s of miles and it's been fine [well it was still true last time it was out and checked]
maybe quality has gone down in recent years, bearing in mind dsc scotty's experience.

[J1MS]

I've welded a couple, a long while ago. One was in TZR steves Primmy that reved very high and was twisting cranks regularly prior to welding.

But what I wanted to know is. which welding process gives the best or strongest weld keeping in mind the types of steels being welded. And do those welding them use a specific wire or welding rod for this.

[shocky]

it has to be TIG welding and something like silver steel filler wire , i dont think it matters much as the weld isnt taking all the load only acting as a key to stop it twisting ,ive repaired keyways with this filler wire, or maybe a chrome/nickle tool steel wire will do the job if the crank is of a higher alloy , the nickle rods are less likely to crack than other wires as the nickle is more elastic , tig welding will alow a more localized heat area than any other but you can control the amount of penertration as well

[mickeyb]

Ive just had an AF Race Crank fitted along with an MBD Racetour TS1 kit,can sum1 tell me what is meant by twisting please?

[shocky]

the 2 halfs are not alined this can cuase vibration , the flywheel to rub the stator,move the drive sprocket out of alinement ,knacker your main bearing or trap the rod causing it to wear or brake and also make the piston score the barrel so not good i always have mine checked ... but the last few cranks ive had have been indian webs rebuilt by harry barlow to race spec but not welded as the pin is always a tight fit and if its not harry will fit a tight one

[nick jordan]

i had an af crank go after about 1500 miles in a ts1 and an alpha go after 1000 ish miles also in a ts1 both with lightened flywheels and with no "bad treatment" (allthough got to say mb stood by their product and got it fixed) now have an af crank tigged by jb tuning in a powerfull rb engine--so far so good

[Powolotti]

took this one out of a friends engine two days ago, seems to be a bit off as well...

[J1MS]

it has to be TIG welding and something like silver steel filler wire , i don't think it matters much as the weld isnt taking all the load only acting as a key to stop it twisting ,Ive repaired keyways with this filler wire, or maybe a chrome/nickle tool steel wire will do the job if the crank is of a higher alloy , the nickle rods are less likely to crack than other wires as the nickle is more elastic , tig welding will allow a more localized heat area than any other but you can control the amount of penetration as well

I was asking as its been a while since I was welding for a living... And I have only welded a few cranks and Clusters and wondered what processes and wire /rod others thought best...

I cant remember all the different rods and wires I used... But I know when I welded dissimilar metals I used certain types of filler wire or fluxed filler rod to prevent grain migration on medium, high carbon or alloy steels...

Here is a little of the welding processes and what I can remember..



The heat input according to the type of welding process ... Gas is the highest; Tig, second; Arc, Third; and MiG welding would input the least heat.... The amount of heat energy absorbed into the surrounding area is what contributes to grain structure changes within the metal being welded, and the depth or spread of these changes...

Gas welding would cause so much deformation it is just not viable where a crank pin is concerned...

Tig is a good weld clean welding process, but the energy used is not instant and the metal being welded has to first melt by heating with the plasma type arc... this makes the HAZ wider... But welding penetration and weld quality are excellent... I have used this process myself for cranks with good success..

Arc welding does not have such a wide HAZ as Tig, done by a competent welder and with a light prep to pin and webs, this I would think, be a good process for welding a pin.. but the choice of filler rod could be critical... a general purpose rod might not be a good idea where as a rutile filler rod for penatration, or a welding rod for dissimilar metals might be... I have welded pins with this process and also welded a couple of main-shafts, assembling modified clusters for close ratio gearboxes... but cant remember the rod type I used.. I think it was a high nickle content, or rutile filler rod... or possibly a low hydrogen rod... really cant remember..??

MiG my favourite welding process with high penetration and a narrow HAZ giving strong high quality results... But I have never used this for a Crankshaft pin... Not that I wouldn't...

I listed what I have used, not knowing what anyone else uses for their assemblies.. I don't know if the way I went about it was right... its just how I did it, and now I cant even remember the exact type of fluxed rods or filler wire I used..

Which would you think would actually be best, strongest or at least give the least problems after welding... i.e. Doesn't crack or distort after welding and gives the longest service life... When welding Crank pins or gear clusters... Shocky has mentioned what hes used & why... is there anyone else that has done this type of welding..??

[shocky]

the dissimilar and nickle rods are good but work best with a DC welder as penetration is better and theres less spatter , but working on a low amperage most rods will flick some spatter ,you would have to be quick with the weld if younu8sed arc and the chances of some perosity or lack of fussion somewere are high with what in effect would be no more than a tack , also the rate of cooling would be quick thats good for the surrounding parts but the weld pool crater might have small cracks in it , thats the reason most tacks are cut out when welding critical fabrications , the TIG if used with a rheostat foot pedal or one that allows the arc to drop off slowly will all but eliminate crater cracks
JIMS i dont know how much load the weld will take and even if a crack occurs it might act as a rough key stoping any twisting
another thing how much room is left either side of the crank after its fitted, i know sometimes the drive side plate had rubbing marks on it from the crank

[J1MS]

Your right about the weld spatter it can be a problem, but on the ones I did the taper was protected with a sleeve of sheet metal and the crank webs covered where they weren't going to be welded... only a small portion of the crank was exposed, the pin was lightly machined and the Webb's were lightly modded to allow for a good strong weld with the arc welder....
But the Tig welding was easier, as it was more controllable especially as it was a three phase water cooled BOC unit, & foot controlled... Very easy to weld with and very neat... and it didn't need so much of a prep to leave a flat (ISH) welded surface.. the weld lightly dressed after welding to ensure it didn't rub on the case... Only ever had one let go after welding, and that was a Tig weld... It cracked in the HAZ, and was the first welded crank TZR Steve fitted it in his primmy, but it was in for a couple of years before it let go... And it reved very high for a road scooter...