5 replies to this topic

[NDT]

I broke my crank pulley when taking it off. 

Given it's from a 35 year old Metro turbo engine which got burnt out in 1990 then it's probably not a great loss.

Probably going to buy the Mini Spares separate pulley and damper, which will need balancing.

Has anyone done this? How hard is it?

[OzOAP]

MED separate pulley and damper are sold balanced.

[NDT]

MED separate pulley and damper are sold balanced.

Thanks. Expensive but tempting!

[Spider]

I've not used the Mini Spares 2 piece Damper, it's a copy of the early Cooper and Cooper S type.

 

I've read where others have found the bolt holes for the Damper Ring are not as tight on the bolt shank as they could be, which is probably not a bad thing, but just check it runs on center before and adjust it for this, before going too far and then perhaps index mark them, so if they are separated later, they can be reassembled back as they were for balancing.

 

Once together, there's really no reason why you can't do a static Balance yourself. You'll need a dummy shaft and 2 knife edge parallels to check it. Set up the Parallels high enough off the workbench to allow the Damper Assembly to turn between them and make sure they are dead level (see below), then check the dummy shaft first for Balance by placing it across the Parallels. it should roll to the lightest side up. mark it and then Check it a few times, each time rolling it over say 1/4 or a 1/3 of a diameter each time. Then remove some material from the heavy side (drilling a shallow hole is an easy way). Keep checking and adjusting until it's in Balance, then fit the Damper Assembly and do the same to that. With the Damper you'll likely be putting shallow holes in it's outer ring, just go easy when removing material as it's on a larger dia than the shaft, it will be much more sensitive to material removal.

 

A very accurate method of getting the Parallels dead level is to fit a 90 square to each of them, the taller the better, then hang a plump-bob off the top of that and check at the bottom of the square for error.

 

This is a common method for balancing Grinding wheels.

 

[ACDodd]

I do loads of them.

Ac

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[NDT]

Thanks.

Any view on whether a crankshaft damper needs dynamic balancing rather than static balancing?