Bearing fit on crank

[dwilfong]

I have bin working on the bearing problems with my VAC 1.05 eng build and have spent some time talking with some very good people to help with this problem.

I know this has bin discussed in the past but would like to start a discussion here in the motor forum.

I have bin looking at a few cranks I have and can see where the inner race has spun on the crank.

From what I have bin told the inner race will expand as it heats up from the bearings not being of the proper clearance.

This pertains to the radial clearance being to tight or as I call it to big balls and also the fit of the race on the crank.

What I am wondering is how to make the fit of the inner race on the crank better?

I have checked out chroming and grinding the crank to size of the particular bearings I will use from a batch of bearing I have purchased. But this is costly about $200.

Then I was looking in to anodizing the crank.

This looks like it can be done at home and with different film build up controlled by the temp and voltage applied to the mix.

Just not sure if it will hold up to this application?

Any thoughts?

David

 

[dwilfong]

I have looked at the Loctite info for 640 and 680.

What success has any one had using this?

Will it last till the bearing change is needed?

 

[RodneyPierce]

My only worry about doing that is I wouldnt want a piece of that to break loose and go through the bearings. Might not hurt I guess? Will the nitro eat it anyhow?

 

[dwilfong]

The problem I am told with the locker is that it dose not preload the race on the crank.

So as the race expands the locker dose not.

My understanding is with a good fit to the crank it should be a slight press on the crank.

This way as every thing expands it still remains a tight fit.

Building up the crank is the only way I see this working.

Also the bearing clearance should be taken with the bearing installed on the crank under preload?

 

[RodneyPierce]

I know both of my .21 Nova's are a "slight press fit" on the rear bearing. First motors I have had that are like that.

 

[steve wood]

we use a carbidizer at work to build up areas that wear from use.it will add carbide to hard or soft steel or carbide. sometimes we add the carbide to i.d. of die bores then hone them back to size.sounds cheesy(gooey?), but works surprisingly well.it doesn't seem to flake off. this would work on your crank,then it would have to be ground. I could hook you up in about 3 months or so

 

[dwilfong]

we use a carbidizer at work to build up areas that wear from use.it will add carbide to hard or soft steel or carbide. sometimes we add the carbide to i.d. of die bores then hone them back to size.sounds cheesy(gooey?), but works surprisingly well.it doesn't seem to flake off. this would work on your crank,then it would have to be ground. I could hook you up in about 3 months or so

Sounds like a plan Steve.

You stay off that knee now and lisen to the Doc.

 

[Ken Retallick]

Hi David,

You cannot anodize steel, Only aluminium.

Hard chroming would be the best option, but it will need to be baked to remove any hydrogen embrittlement.

Grinding to size afterwards will be the biggest cost if you have to farm that out.

 

[dwilfong]

Hi David,

You cannot anodize steel, Only aluminium.

Hard chroming would be the best option, but it will need to be baked to remove any hydrogen embrittlement.

Grinding to size afterwards will be the biggest cost if you have to farm that out.

http://www.corrosionhelp.com/steelanodize/AnodizedJECS2007.pdf

 

[Ken Retallick]

Interesting! never heard of that process before.

 

[Tom Foley]

Probably cheaper to change out the cranks . I've seen the inner race "skid" on my Mac 84's - 67 's and VAC 91's while turning over slowly with backplates off . I tried some penetrating grade green loctite applied with an artists brush to the race and the crank . Next time I took the plates off it was not doing anything , bearing would skid if turned super slow .

 

[dwilfong]

Changing out the crank will not stop it from happening again thats the problem.

The tolerance that is held for production of cranks and bearings is all over the place when it comes to the fitting of the bearing.

It is the luck of the draw if you get a good match.

When Steve gets back on his feet I will give the carbonizer a try.

Also found some full complement 6002 bearings thy use on mountain bikes that look promising. http://www.jensonusa.com/Bearings/Outlet-Abi-Enduro-Max-Cart-Bearing

Will send them off to Greg to have them checked out and re balled.

 

[dwilfong]

Probably cheaper to change out the cranks . I've seen the inner race "skid" on my Mac 84's - 67 's and VAC 91's while turning over slowly with backplates off . I tried some penetrating grade green loctite applied with an artists brush to the race and the crank . Next time I took the plates off it was not doing anything , bearing would skid if turned super slow .

Thanks Tom that is what I needed to know.

 

[lohring]

You could try brush plating. Out here it's used commercially to repair shafts on industrial equipment in place.

Lohring Miller

 

[dwilfong]

You could try brush plating. Out here it's used commercially to repair shafts on industrial equipment in place.

Lohring Miller

Thanks Lohring I was looking at brush plating but could not find a cheep set up.

I will check this out and give it a try with a old crank I have to play with.

 

[Tim_Duggan]

So when these tolerances are refined, how does one get the race onto the crank? ( Press, or immerse the crank first in dry ice maybe?)

 

[dwilfong]

The fit I am told needs to be a firm press that you can almost do with your finger.

Pressing needs to be done on the inner race.

The bearing need to go on the crank first then install the assembly in the case.

Marty Davis showed a pic of a tool he made to fit the bearings and crank assembly in the case.

It may be on his web sight?

Nova Rossi has a tool for this for there engs.

 

[dwilfong]

Well got some good news found a full complement bearing and sent it to Greg Settle to check out.

Looks like we got a winer. Thy checked out real nice and reballed with ceramics seam to be the ticket.

Now on to the front bearing for the same thing.

 

[Tim_Duggan]

I'd imagine with the rear bearing now being full compliment, the front one wouldn't really need to be as long as it's a reasonably good bearing to begin with. The distortion is originating at the rod end (unless you are side loading the threaded end with gears or a belt pulley).

 

[dwilfong]

Well are thinking is with the shaft pushing on the smaller front bearing it is taking a heavy load.

The front bearing is the same size as a .21 rear bearing.

With the clearance set at the proper dimensions and good ceramic balls the full complement will out perform the standard bearing.

Why do it half a$$ed?

At less than $5 for the bearings to start with the rebuild is very cost affective.

Mountain bikes use the same bearings as are little Eng's

Some times you have to take the blinders off and look out of the little box we are in.