Excessive crank end float.

Mart

Mart

Well-known member
What problems are associated with excessive crank end float?

I have a crank that is in nice condition but when assembled up it has .020" end float. The motor starts up ok, I haven't driven it yet.

What, if any problems can I expect from this situation.

It is a French motor so has 59A type cam gears which thrust the cam towards the block and subsequently there is a forward thrust on the crank. This is the same direction as clutch release thrust.

So in this case would it be reasonable to think that the crank might tend to spend most of it's time at the forward limit of travel and not switch back and forth? Or do you think it would drift towards the rear location during acceleration?

I don't really have much choice as I want to run it at the weekend but I was wondering if excessive end float is more of a less than optimum thing or is it definitely a complete disaster.

Mart.
 
I cannot answer your question, but what I've done in the past in this situation, is I've built up the thrust faces on the bearing with babbit and machined to suit.
 
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It may have a sound like a loose main bearing when going off and on load driving conditions. Spec is about .08 IIRC
 
Hi Mart. At .020" end float I wouldn't expect any problems. Not optimal for sure, but not a disaster either.



Terry
 
It is not going to last very long with that much clearance. You need to determine what the problem is first.
Is the thrust bearing worn? If so, possibly a new one will cure the problem.
Is the block saddle worn? If so, sleeving the side of the saddle will cure that.
Is the crank thrust worn? If so, it can be welded and re- ground.
 
The thrust surface width on your nice condition crankshaft is worn so to reduce the end play a bit here's what you can do. Flare the thrust surface out just a touch on the main bearings. Wont take much to reduce the end play down to the max which is .006 according to the books I work from. It would take a long time before any wear is seen in the bearing if you decide to just flare the bearing thrust surface out a slight amount.
Ronnieroadster
 
Pete said:
Is the block saddle worn? If so, sleeving the side of the saddle will cure that.
Click to expand...
How is that done?


I've read here in the past that the bearing shell can be shimmed a few thousandths to adjust end play, is that a reasonable thing to do?
 
My way of thinking is how does that much end play affect the rods with it thrusting fore and aft ? I’m thinking not good.
 
cas3 said:
It may have a sound like a loose main bearing when going off and on load driving conditions. Spec is about .08 IIRC
Click to expand...

.080"? You sure about that? That seems like a mile. That's just shy of 1/16".
 
Ronnieroadster said:
The thrust surface width on your nice condition crankshaft is worn so to reduce the end play a bit here's what you can do. Flare the thrust surface out just a touch on the main bearings. Wont take much to reduce the end play down to the max which is .006 according to the books I work from. It would take a long time before any wear is seen in the bearing if you decide to just flare the bearing thrust surface out a slight amount.
Ronnieroadster
Click to expand...

Ronnie, .006" sounds much more credible than the .080" that CAS3 posted.
 
Yoyodyne said:
How is that done?


I've read here in the past that the bearing shell can be shimmed a few thousandths to adjust end play, is that a reasonable thing to do?
Click to expand...

Same principal as if you were sleeving the middle of the saddle. You bore away about .080 from the area covered by the side of the shell, then make a flat curved piece to fit in the bored away area. Make the insert about .010 to .015 thicker than the finish thickness for the saddle.
Clamp the new piece in place with a generous amount of Loctite and drill 4, 1/8 holes evenly spaced across the piece. Take a short piece of 1/8 brass welding rod, coat the tip with Loctite and drive it in one of the holes till it bottoms. Do the other 3 the same way. Take the clamp off.
Using a fine tooth jewlers saw cut the excess brass off of the pins. Now peen what is left down till it is flush.
Face and bevel the insert to finish size.

NO, you can't shim a bearing shell and expect it to live.
 
Pete said:
Same principal as if you were sleeving the middle of the saddle. You bore away about .080 from the area covered by the side of the shell, then make a flat curved piece to fit in the bored away area. Make the insert about .010 to .015 thicker than the finish thickness for the saddle.
Clamp the new piece in place with a generous amount of Loctite and drill 4, 1/8 holes evenly spaced across the piece. Take a short piece of 1/8 brass welding rod, coat the tip with Loctite and drive it in one of the holes till it bottoms. Do the other 3 the same way. Take the clamp off.
Using a fine tooth jewlers saw cut the excess brass off of the pins. Now peen what is left down till it is flush.
Face and bevel the insert to finish size.

NO, you can't shim a bearing shell and expect it to live.
Click to expand...


Thanks for that description Pete.


The shims I read about here were behind the thrust surfaces only, much like the inserts you describe. So you say that does not work? Is it because of lack of heat transfer?
 
Yoyodyne said:
Thanks for that description Pete.


The shims I read about here were behind the thrust surfaces only, much like the inserts you describe. So you say that does not work? Is it because of lack of heat transfer?
Click to expand...

If there was some positive way to hold them in, they might work.

Heat is not a problem.
 
So sorry...I left out one zero ! At any rate, I still think you will hear a knock like a main bearing, and agree with ken, rods won't like the thing moving around. I would fix, or not use it
 
Crank is low miles French military rebuild. Bearings are brand new. Saddle is not worn.

I think the French military might have ground the cranks oversize on the thrust faces and had access to oversize bearings to suit.

I have a crank with a damaged thrust face. Can someone give details on the welding process to build up the thrust face?

For example, what type of welding? Mig? Arc/ what type of wire or rod? Special gas?

If normal mig welding and wire I could try myself. Ditto if arc if I know what rods to use.

Thanks for the input so far..

Mart.
 
Mart, What I've done a coupla times now is to build up the faces on the bearing. use a big iron and some whitemetal. easy peasy; the faces are already 'tinned' so to speak, just need a bit more of a build up each side. Then machine the built up faces to acheive your desired clearance. you say you've got .020" clearance. You only need an additional .007" on each face. In effect, you're making oversize bearings as you claim the French had access to.
Personally, I don't like welding cranks, can be done, but a lot of work!
 
Hi Mart.. take the soft option. You could look at metal spraying the trust surfaces of the bearings. Then mill or sand them to suit. I like Brian's idea.
Just a thought.

Regards Kevin
 
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