Crank Collar Verus Weld And Machine To Extend

[darrinspencer]

It was mentioned to me the other day of a crank shaft repair mob in Brisbane prefer to weld the front of the crank and machine instead of fitting a crank collar. They believed they could better clearances to the pump drive doing it this way

Cost was approx $220-240 which is not too much different from paying someone to supply and fit the crank collar.

What are people thoughts with this method

[bubba]

Some don't like it, some do.

It is what I will be doing.

[chuckie]

Hi Darrin,

I think WELD & machine is only way to go BEST FIT & no worries,

this will be done on my 30,

Goodluck with build great work,

Cheer`s Chuckie

[The Dan]

LOL when the snout of your crank snaps off. It'd be a cold day in hell before I'd weld anywhere near the end of a crankshaft. Considering you can take a crankshaft into Chilton engineering and have the collar supplied and fitted for around $220-$240, why would you even consider something like welding?

[tridentt150v]

Welding a crank can be done, but it is much much more than a simple hit with the mig. If you pre heat the whole crank and use slake lime to cool it etc etc then it will work. This costs a heap more and I doubt anyone is set up to do it properly, but [as Elite says] otherwise you will see it snap at the heat location front where one side is hot as from the weld, and the other side is cold.

I've had a crank welded [it was a one off crank and the splines had been flogged by a cog that when the lock tab washer snapped. You don't pick up on those sort of things until in gets noisy]. It was for a motorbike so a lot smaller easily managed - and is still working today. But the firm [which has since closed down] followed the full process - they knew what they were about and specialised in doing it. The trouble is in our throw away society these days, there are less and less craftsmen and more and more tradies!!!so sadly the art is being lost.

[YLD-CHLD]

Welding a crank can be done, but it is much much more than a simple hit with the mig. If you pre heat the whole crank and use slake lime to cool it etc etc then it will work. This costs a heap more and I doubt anyone is set up to do it properly, but [as Elite says] otherwise you will see it snap at the heat location front where one side is hot as from the weld, and the other side is cold.

I've had a crank welded [it was a one off crank and the splines had been flogged by a cog that when the lock tab washer snapped. You don't pick up on those sort of things until in gets noisy]. It was for a motorbike so a lot smaller easily managed - and is still working today. But the firm [which has since closed down] followed the full process - they knew what they were about and specialised in doing it. The trouble is in our throw away society these days, there are less and less craftsmen and more and more tradies!!!so sadly the art is being lost.

Agreed i had a similar problem & had a bloke in his "Backyard Garage" TIG it up,in sydney.

This bloke is a craftsman,1 look at his "Backyard Garage" convinced me,man wat a setup ,TIG ,Lathe ,Mill,Horizontal borer,grinders unbelievable.

[STATUS]

collar or late model crank.

[old mate]

80mm collar from a bearings supply place for $60 and you tap it on with supplied fitting and then cut off the lip. David Chilton told me to do this.

[chuckie]

Tridentt , Not May left , the most important thing IS THE HEAT TREATMENT, keeping at A SET temp & then slowly reducing it over set Time,,so many do not UNDERSTAND welding & what the HEAT AFFECTED ZONE is ,it`s the HEAT TREATMEN that return`s all metal`s to former state or close to it,

Now i will WELD MAY CRANK WHERE I HAVE BEEN TOLD TO & DO ALL MOD`S TO BULD A ENGINE THAT WILL LAST & get it HEAT TREATED AFTER ,

I see SOME MANY WELD ALI & then run 30 pis & wonder WHY IT SPILT`S around welded area ,

NORMALIZE SHOULD BE A MUST IF YOU WELD ON MOST METAL`S but people DON`T WANT TO PAY FOR IT ,& DON`T UNDERSTAND WHY IT`S A MUST IN MOST ENGINE COMPONTENT like a CRANK ,

shame we have lost the oldschool way`s & it`s just inthe bin & buy new

Cheer`s Chuckie.

[GTRNUR]

Welding affects the metal at a molecular level in more ways that you can imagine. Firstly you are introducing a metal alloy (filler wire) that is of a different grade than the crank material. As it is a different type of metal it behaves differently at different temperatures.

Tig welding focuses way too much heat in one area at a time and mig would not be a pure enough weld, nor would it be hard enough material to bother doing. The metal around the finished weld would potentialy be softer than the crank material, as well as there is the potential for introduced crystalisation of the material.

The only method of welding that is worth considering is submerged arc welding, where the crank is machine welded in a rotating lathe. This then introduces the issues associated with heat warping and material grain disruption. This method is sometimes used to repair crankshafts in industrial engines, and also for building up camshaft lobes prior to re-grinding.

The material the nissan cranks are made out of is extremely good quality. The factory forged cranks combined with the nitriding is the reason the majority of cranks only need a linish before being re-used after 150-200,000K's. This combined of course with multiple heat cycles and work hardening of the crank journels that happens from years and years of running in a low reving R31 skyline, with mineral based oils.

Instead of welding the crank, consider machining back the snout as you would to fit any other colar, and then have an oversize custom colar machined up from 8640 chromoly (gear grade chromoly). Have it interference(shrink fit) to the crank colar with a 0.0011 interference, then grub screw it to the crank. Finally have the new oversize colar machined down to fit your pump perfectly. This way you arent messing with the metalurgy of the crank, AND you have a much harder grade steel driving the oil pump that a built up weld drive would be.

After its all said and done, its a lot of work to do to a crank that is well proven to 9000 rpm with just a JUN extension and a good quality pump (tomei, nitto, etc).

Edited May 26, 2010 by GTRNUR

[Duncan]

I've run both collars and welded cranks in the race car with no issue