Cast iron crack repair

[IHJ]

Hi, i have a flywheel of a small vintage garden tractor that has 3 hair line cracks about 1 1/2 inch long from the centre.

As i have never welded cast before i would like some advice.

I have been told to use cast iron welding rods 2.5mm??? and to drill a hole at the end of the crack.

If anyone has further suggestions it would be much appreciated and if the hole technique is correct how big a hole? and do i drill right through?

I know welding a flywhell isnt ideal but im restoring the tractor and cant find a replacement.

Many thanks,
James

 

[dannyp]

ummm welding flywheel,

get some dye on it and find the true end of the cracks and if and how meany more there are before doing anything else

 

[piman]

Hello James,

In addition to welding, have you considered using steel disc(s) screwed to the hub to reinforce it? I think a fairly neat job could be done using countersunk screws?

Alec

 

[mowersman]

I'm afraid to say I would be very very cautious about welding flywheels. I have seen the aftermath of a flywheel explosion when a stationary engine flywheel broke up when it was running. Not pretty. What is it off, It may well be possible to find another.
Andrew

 

[awemawson]

I'm with mowersman on this one. Don't do it! Fabricate a replacement from flame cut plate, or get a replacement cast using the original as a pattern.

 

[Drains]

I'm with mowersman on this one. Don't do it! Fabricate a replacement from flame cut plate, or get a replacement cast using the original as a pattern.

Thirded. Don't do it.

 

[PTvor]

I've seen a broken cast iron flywheel from a lawnmower which I think was grey cast Iron with a really coarse crystal structure. From what I could find out it couldn't be repaired safely by welding.

Don't attempt it, the flywheel might break up and it's dangerous. It could also wreck the engine.

 

[brightspark]

I'm with mowersman on this one. Don't do it! Fabricate a replacement from flame cut plate, or get a replacement cast using the original as a pattern.

one problem using the original casting as a pattern.the flywheel cast off the original will shrink when it cools and be smaller so unless the spec from the original isnt critical it will be ok. and dont forget the original will have been machined down to size

 

[Robotstar5]

one problem using the original casting as a pattern.the flywheel cast off the original will shrink when it cools and be smaller so unless the spec from the original isnt critical it will be ok. and dont forget the original will have been machined down to size

The pattern shop in the foundry I worked at had special calibrated rules that compensated for the shrinkage when making the patterns to finished drawings.

 

[brightspark]

The pattern shop in the foundry I worked at had special calibrated rules that compensated for the shrinkage when making the patterns to finished drawings.

yep me brother has a couple of them bought from a autojumble for 2 quid not a sellable item unless u make patterns for castings

 

[awemawson]

Yes I also use contraction ruels, however for a small casting, wriggling it in the green sand before removal and after ramming will usually make up for the shrinkage

 

[dannyp]

would be easyer to fabricate a flywheel rather than cast it if your just doing the one.

the weight on a knackerd old post rammer cuts down nicely to make flywheels

 

[TechnicAl]

Well Im going to be contraversial here. Id weld it. If you do it properly and do what dannyp suggests and dye pen it to make sure you have repaired all the cracks. It shouldnt be a problem
A flywheel will more than likely be made from SG Iron unless its really old. Even if its grey iron it should still be OK. Follow the rules given in the tutorial section and you should be alright.

The only alternative would be to get a replacement if possible. Casting one isnt as easy as it sounds, getting the shape is one problem but also getting the correct metallurghical structure is another.

 

[Drains]

Al.

Perhaps it might also be worth considering why the flywheel cracked in the first place. Poorly cast, inferior material, is it on a taper shaft and been over-tightened, or taken a wallop at some point, or is it out of balance?

By welding it you're introducing more stresses into a high speed rotating lump which already has unresolved problems. It may be true that cast is repairable, SG certainly, but without knowing what caused the original failure, seems like asking for trouble.

Still, I won't be driving the thing.

 

[TechnicAl]

I was thinking that its lasted this long (whatever that is) and its been cracked (for how long) and it hasnt failed.........so why would repairing it make it worse

Ive been wrong before

 

[Drains]

I was thinking that its lasted this long (whatever that is) and its been cracked (for how long) and it hasnt failed.........so why would repairing it make it worse

Ive been wrong before

And it might be slow revving and over engineered. If it were me... well I'd get the lads in the machine shop to knock one up, but if it weren't for them I'd get the nickel rods out. But would that be sound advice to give?

Your questions over age and time of crackage may be good ones to ask.

 

[aametalmaster]

Check out this flywheel mishap. I know it wasn't welded just turning too fast but the oomph is still there...Bob
http://gardentractorpullingtips.com/flywheelbreakage/flybreak.htm

 

[Shox Dr]

hollys***e!!!

 

[awemawson]

Like I said before DON'T weld it, replace it. The risk is totally unjustifiable.

 

[PTvor]

Some risks are worth taking and some are not worth taking. I don't think welding a cast iron flywheel together, especially one rotating at high speed, 2,000 rpm or whatever this thing does, is a risk worth taking.