Welding on a Flywheel Ring Gear?

[CCWKen]

Moved from another post:Speaking of ring gears John, are you making them from scratch or weld/repair? I need one for a Kubota and can't seem to get one without buying a whole freakin' lower end--about $1200.
I figure I can weld new "teeth" and grind them back into profile. The problem is; I'm afraid of weld srinking the ring and not being able to get it pressed back on the flywheel.

Any suggestions?

[zl1byz]

Don't press it on. Use the oposite force that you think is going to cause your trouble. Warm the ring gear up so that it expands enough to get it onto the fly wheel then let it cool/shrink on. Probably more knowledgable people out there but this is how I have seen it done.

John.

[This message has been edited by zl1byz (edited 01-07-2005).]

[x39]

John is right, I've removed and replaced ring gears on flywheels a bunch of times, and a little bit of heat does the trick, slick as can be every time.

[wierdscience]

Shrink it back on the flywheel first,then do the welding,after it cools,reheat the ring gear and drive it off,then remachine the teeth and shrink it back on.

Is it so far gone that you can't just flip the gear?

[torker]

The others are probably correct but...after welding (with it on the flywheel) I'd be tempted to hit the welded areas with the torch to relieve the weld stress. It's already pretty tight and the weld is going to suck it down even more.
Russ

[CCWKen]

Yep, I've replaced ring gears before. I've never tried to weld one though. Thanks WS, I'll give that a shot. It's really bad on one spot and pretty bad in another. (The stop points) The starter doesn't engage at all in the "really bad spot". I could probably rotate it to a new index though. (pinned)

I'll give the welding procedure a shot. The flywheel is heavier than a truck load of "farm spread". Any chance of warping?

I think I may have an old T gear to practice on.

[zl1byz]

<font face="Verdana, Arial" size="2">Originally posted by torker:
The others are probably correct but...after welding (with it on the flywheel) I'd be tempted to hit the welded areas with the torch to relieve the weld stress. It's already pretty tight and the weld is going to suck it down even more.
Russ</font>

This is a curly one. Don't forget that the ring gear already has stresses in it from the interference fit on the flywheel. I'm not sure which force will have greater effect, remember welding can stress releive forces already in the material.
I'd be a bit carefull about hitting the ring gear. They can be broken.

John.

[torker]

John...Thats why I'd give it a BIT of heat. If you don't it may not fit without a bunch of heat. I've changed lots of ring gears out and am aware of how they work. I've also got into lots of trouble welding things and finding out they don't fit after. Heat can be your friend in a tricky situation. This is a tough call with out some kind of testing or the proper BIG measuring equipment. I've never welded anything that didn't shrink to some degree. Stress relief in the weld area would hopefully bring it around where it should be.
Russ

[x39]

Perhaps preheating prior to welding would help?

[zl1byz]

<font face="Verdana, Arial" size="2">Originally posted by torker:

John...Thats why I'd give it a BIT of heat. If you don't it may not fit without a bunch of heat. I've changed lots of ring gears out and am aware of how they work. I've also got into lots of trouble welding things and finding out they don't fit after. Heat can be your friend in a tricky situation. This is a tough call with out some kind of testing or the proper BIG measuring equipment. I've never welded anything that didn't shrink to some degree. Stress relief in the weld area would hopefully bring it around where it should be.
Russ</font>

Your probably right Russ.

John.

[torker]

<font face="Verdana, Arial" size="2">Originally posted by x39:
Perhaps preheating prior to welding would help?</font>

Yes it probably would....but how much? I can almost guarantee if you shrink that ring gear even a bit too much you are going to have a devil of a time putting it back on.

[zl1byz]

Almost wonder if your going to weld it in place why not machine it on the flywheel too.

John

[CCWKen]

I'm concered about pre-heating (Gear on the flywheel). The flywheel is cast iron and I'm afraid that applying heat in isolated areas will warp it. Yes, no? Pulling it off is no problem. A little torch heat in a circle and it practicly falls off.

I can get a good set (penetration) and build with my MIG in two quick steps. Wire speed low then kick it up. I've done it before with a spur gear. But it had some mass.

I guess I can only hope that the flywheel will expand slightly and act as a jig for the ring--Holding it close to spec as it cools.

Well, what the hay. It's not much use as it is now any way.

[CCWKen]

John, I'd have to take anoter look at it but as I recall, the gear sits right up against a ledge and even with the top of the teeth. (No clearance behind it.) I sure would hate to cut into that! Read rebalance.

[John Stevenson]

Ken,
Good advise in that ring gears are shrunk on.
For just a few damaged teeth I'd MIG weld them a pair at a time and file or grind them back to shape.
The MIG won't put enough heat into a job this size to matter.

The ones I'm doing at the moment are new rings from scratch for going onto large boat flywheels.
These were either hand crank or cartridge start and never had ring gears.
Because of the size we can't get an off the shelf gear.
Ring gears work to an ANSI standard and one size is too small for the flywheel and the next is too big for the location.

I though a shot of the machining setup would be interesting.
These rings are 22" inside diameter and 23.75 OD to take 188 teeth at 8DP.



[PS] Perhaps now you can see why I can't get a hoist leg BEHIND the lathe

Only snag is the bigest faceplate I have is 19" and I don't have a spare sub plate any bigger.
The oxy-aceteylene profiled blank is welded to four 3/8" thick washers out the scrap profile box, bolted to the face plate and bored. The OD was done with the same boring tool mounted upside down and the lathe run in reverse.
The washers are then ground off and welded to the next ring.




Another shot showing the chamfer being turned.

These will be pressed and pinned onto the flywheel and then the flywheel will be held horizontally on a big rotary table on the bed of the horizontal mill and the gear teeth cut with a form cutter on the arbor by raising the knee past the cutter.

John S.


[This message has been edited by John Stevenson (edited 01-08-2005).]