Sheered bolt removal?

[tj500]

It's the bolt that holds the crank pulley in place, which became detached rather alarmingly under speed t'other day. Griff now at my local mechanics (alas no TVR specialists round these 'ere parts) who called this morning saying unable to remove remains of sheered bolt. Help!! Done a search on previouis PH threads, it appears the problem is not that rare, people talk about 'spark cutting' and 'spark erosion' to get it out - what is this & what is the equipment required? Any alternative suggestions for removal also urgently welcomed.

tj

[victormeldrew]

Those are put in at a monumental torque - equivalent to a big guy standing on a scaffold pole. I'm not too surprised they can't get the sheared remains out!

Spark erosion is sort of the opposite to arc welding; instead of material being added, material is taken away. Good description here You'd want the guy doing it to be pretty damn good, or your crank nose will be eroded too. I can't see how you could remove the bolt by this means without damaging the threads/crank to be honest.

[steve-v8s]

It is vitally important that all the bits hung on the front of the crank are balanced, so if the bit doesn’t come out cleanly you may be better off getting the crank rebalanced else you will end up with a two part crank, like I did. I can confirm that they make quite a bang when they snap and the potential cost is lot more than getting it, the pulley and flywheel balanced. Obviously the nicest solution would be to get the broken bit out cleanly.

[s7paul]

I'm a bit puzzled, though this could be due my unfamiliarity with the design of these parts. If the bolt head has sheared off, the torque load on the thread will have gone, so you should be able to remove it relatively easily. Can they not drill into it and use a stud extractor?

[victormeldrew]

Mmmm, I was thinking that there must be some of the head left that is applying torgue - or as you say the remains should be easy to remove.

[tj500]

s7paul said:

I'm a bit puzzled, though this could be due my unfamiliarity with the design of these parts. If the bolt head has sheared off, the torque load on the thread will have gone, so you should be able to remove it relatively easily. Can they not drill into it and use a stud extractor?

Update from garage is that they've drilled into it & tried to extract but it won't budge, they think it's bonded in. Are now trying oxy-acetaline to warm it up & melt the glue in order to aid extraction. Am nervously waiting for the phone call from them right now...either to tell me they've succeeded or engine bay's on fire! Just do NOT want to contemplate possible failure & requirement for new crankshaft...

tj

[victormeldrew]

Fingers crossed - 500 cranks are a tad rare.

[tgriff]

Mine did the same low loader back to TVR " they do that sir" spark cut it is an easy out there is no torque on the bolt once the head is sheared off.
They simply arced an small bolt on the end and turned it out .
fit a new pulley and a new high tensile bolt
steve

[GreenV8S]

tgriff said:

Mine did the same low loader back to TVR " they do that sir" spark cut it is an easy out there is no torque on the bolt once the head is sheared off.
They simply arced an small bolt on the end and turned it out .
fit a new pulley and a new high tensile bolt
steve

Because they have to be done up 'kin 'kin tight to take the torque from the damper, and because that puts them quite close to the limit for that bolt, it could have been glued in to make sure it doesn't shift. If so, it'd be a pig to remove even after the end load has been taken off.

[tgriff]

any lubricant on a fixing alters the torque and should not be used or if it is used then a different torque setting should be used.
The bolts never ever suffer from coming loose if done to the correct torque, they snap.
the only way the remaining stud could be tight is if it had bottomed in the hole , if so its the wrong bolt.
The bolt will come out , if necessary a 6mm hole and an extractor can be used with little problems, believe me when the factory was open they had done hundreds.
By the way the new pullys come statically and dynamically balanced so bolt straight on

Don't worry the man unduly
Steve