Crank rebuild.

[Mekanix]

Opinions wanted.

I have a wsm crank with 10 hrs and the counterbalance shaft bearing went.
Destroyed the crank gear and seals.

One part of me is thinking to use a donor crank gear, new seals and new bearings and it's good to go again.

Another part of me is thinking how much would that cost? Vs replacing the crank.
And reliability??

Just a shame to see it go to waste.

Nowhere local to me does crank work like that. I dont have a strong enough press or the experience to do it myself yet.

So what would you do ?

 

[etemplet]

Under the circumstances.... No way. And I am a huge proponent of condition based repairs and maintenance. It's too cheap to replace the crank now and way too much work and expense to replace it later. Eating that gear put a hell of a load on everything and with that much metal being moved chances are it got into places you don't want it to be.

On a side note, I don' think it is worth it to repair a crank yourself. Too much work, too little cost savings.

 

[Mekanix]

I started rebuilding counterballance shafts and replacing sleeves, so it felt like something interesting to do.

Your right about the loading. I didn't consider that factor.

 

[etemplet]

Hey, if you're doing all that then... what the hey. Go for it. I priced quality parts for the crank job. They are not cheap. I have a balancing machine in the shop but it's not set up. Boy O Boy that would be interesting to balance everything and see how much smoother it would run.

 

[etemplet]

I started rebuilding counterballance shafts and replacing sleeves, so it felt like something interesting to do.

Are are you changing the seals on the CB shaft? What are you pressing the gear off with? It'd be nice and easy of there was flat surface to press against.

 

[Mekanix]

Are are you changing the seals on the CB shaft? What are you pressing the gear off with? It'd be nice and easy of there was flat surface to press against.

Yeah i change the seals too.
I set up a special block in my press that allows the gear to sit flat. Then warm up the gear with my heat gun and press it off. But daam it takes alot to get it to move. About 5 tonn to start it then 1 tonn to get it all th way off. Indexing isnt that hard either.

951 shafts are the easiest. I just use the bearing to pull the weight off too. Then use the weight to push the bearing back in place. Indexing is easy witha few marks. Also it moves at 2-3 tonn and then hardle anything to drive it all the way off.

 

[Mekanix]

Also i maxed out my 10 tonn press trying to seperate a 720 crank. Even with heat it wouldnt budge. So need some major power to get these apart. If i had access to the equipment i would try just to gain the experience but like you said with that kind of loading and destruction of the cases i think there would be a bend in the crank or weakened component.

 

[Matt Braley]

WSM knows about the issue. I would contact them and see if they will help you out like they have done for others in the past.

 

[Mekanix]

WSM knows about the issue. I would contact them and see if they will help you out like they have done for others in the past.

Oh really?
I'm not sure which failed first, the ballance shaft or the crank gear.

It was a counterbalance bearing that disintegrated but I'm not sure if that's a symptom or a Cause for how to defend a case of saying the crank is the cause

 

[etemplet]

Yeah i change the seals too.
I set up a special block in my press that allows the gear to sit flat. Then warm up the gear with my heat gun and press it off. But daam it takes alot to get it to move. About 5 tonn to start it then 1 tonn to get it all th way off. Indexing isnt that hard either.

951 shafts are the easiest. I just use the bearing to pull the weight off too. Then use the weight to push the bearing back in place. Indexing is easy witha few marks. Also it moves at 2-3 tonn and then hardle anything to drive it all the way off.

Send me a picture of what you are using on the 787s? I experimented with one, using heat but I pulled on the outside of the gear with a bearing puller. Bent the hell out of it. Ha ha. But I was experimenting. I have 100 ton press partially built but I"m lazy and always find a way that I don't need it.

Get yourself a torch, not a toy torch either. Quick heat and you'll use a lot less pressure. That heat gun is useless. The heat will travel from the external part to the internal too quickly and it isn't near hot enough.. You need a quick HOT heat. some of the stuff actually falls off with little to no pressure from the jack but it is good to have it in place if it gets stuck. I did this kind of work every day. Sometimes two and 3 torches going at the same time. You sure are going "all in" on this stuff. Good Luck !!

 

[Matt Braley]

The WSM problem was with a bad run of cb's. With only 10 hrs on it I bet they will at least sell you some better parts at cost or something, it's worth a try.

 

[etemplet]

The WSM problem was with a bad run of cb's. With only 10 hrs on it I bet they will at least sell you some better parts at cost or something, it's worth a try.

The shafts were new?? If so.... Yikes !!

 

[Mekanix]

Ok this was a wsm crank with an oem counterbalance shaft. Was actually my first 951 rebuild. I should have replaced the bearings. "Thought they felt good" well since then I've learned to just replace them reguarldess.

Actually I've learned two things from this one.
First is to replace the bearings,
Second is to always replaced a chipped sleeve. This one was chipped and welded and then another chip formed and took out the mag cylinder. And the weld cracked anyways.