brazing on line shaft

[vbottles]

Hi all.
I've been asked to look at ways of fixing a broken flange joint on some line shafting. It's got an old break covered in oil and grease with a new break that is clean. I can either remove the flange and braze up then re fit. I'm concerned that the brazed section wont remain round and in line with the shaft.
The other option is to braze in situ. But is there a risk that I could braze the shaft onto the flange. I'd like to avoid this incase the flange needs to be replaced in the future ( breaks again). Though the shaft could be a bit of a heat sink.
I've got access to Oxy act. Or Oxy propane. It's there any benefits in welding this cast iron? I've got experience in oxy.act, mma,mig and tig welding I've brazed a couple of times on smaller sized pieces. But am not sure how much heating this would take to braze.
Andrew

 

[WorkshopChris]

If i was to attempt that it would have to be done off the shaft.
You will need to v out from the centre and braze the external then internal and machine the bore afterwards.
Probably machine a ring of some sorts for location purposes.
I have in the past sealed the crack area with a thin coat of varnish to keep the surface clean while removing the oil and crud then blast once its de greased. It stops the new broken surface adsorbing any oil.
Lots of pre heat then slowly cool wrapped in a welding blanket.

Don't know what fits through the holes but if its just bolts could you not make new bush with keyway then bore out the damaged cast and weld four tabs onto you new steel bush that locate with the four holes. All depends how much load iths thing is transmitting and what facilities you have available.

Just guessing from the mesh is the shaft roughly 4" and the OD 16".

 

[the snooper]

Make a new flange would be the best option

 

[Seadog]

It also looks like the crack is propagating through the fillet on the right hand side of the boss. It looks like it may be a nightmare to weld or braze.

 

[500e]

To meany cracks a rotating nightmare get a new one made, bet if you degrease & crack test it will scare H&S
Seadog to the left as well click & blow pic up

 

[vbottles]

The line shaft is around 4 inch in diameter. The flange is around 12 inch. The four holes take bolts about 1 1/4 ". These attach onto a vertical line shaft about 8 in di as meter. AttachedTo shafting from a big water wheel. Low speed but a bit of torque behind it. The shaft revolves about 30 rpm.
I have thought about turning up a new flange. But wanted to see the amount of effort needed to braze this up. Also see how complex it will be.
Andrew

 

[Bill Edwards]

A new flange would be the best way forward, probably not a big deal although it's probably pretty big?

I would vee it out and weld it cold, followed by making a collar to fit snugly over the broken part which would give it a lot of strength, obviously also welded in place to the flange and the repaired section (braze would actually be better for that part).

 

[Screwdriver]

Looks bigger in the pic. You'd need to thoroughly clean it of course and burn out the oil, over a bonfire or barbecue I guess, then braze while it's still hot and cool it slowly etc.. Braze is best and it will need to be V'd out first.You will have to re machine the bore whatever you do not forgetting you want to discover why it broke in the first place.

Is it keyed onto the shaft?

Best place for info is Keith Fenner's YouTube channel.

S.

 

[vbottles]

Thanks for the input. I think I'll look at making a new flange. As the footage broke after the holding bolts loosened of and the top shaft started turning out of true.
The difficult part will be making bushings to fit into the lower bolt holes. These are oval and slanted with a taper leading to the hole.
Andrew

 

[ikb]

Thanks for the input. I think I'll look at making a new flange. As the footage broke after the holding bolts loosened of and the top shaft started turning out of true.
The difficult part will be making bushings to fit into the lower bolt holes. These are oval and slanted with a taper leading to the hole.
Andrew

Probably all over bar the shouting now but considering the need to ensure the parts are absolutely clean and remain clean while the brazing is undertake It occurred to me this may have been be a candidate for a large salt bath brazing tank. It could be clamped together with a sacrificial clamp/s and immersed into the salt bath and left to come up to the process temperature. The only tricky part would be applying the brazing material which is generally applied as a preform so that it wicks into the joint by capillary action. Just as an academic interest has anyone got any knowledge of this process with large items?