Sleeving crank journals - good idea / bad idea?

[Captain_Chaos]

At the risk of sounding stupid?

I am thinking of having a 1mm (0.04?)  thick sleeve fitted to the crank journals.
This would require machining the 30mm journals down to 28mm to accommodate the sleeves.
What are the chances of the following happening?
-   Crank failing catastrophically due to reduced strength
-   Sleeve breaking apart
It is a no-brainer that this is not as good as a fresh crank. But if it works it would be an easy fix.


I am considering this, as I have not been able to find someone locally who is prepared to hard chrome a 2T crank.

Loctite is an option, but I am concerned regarding the ease of splitting the cases afterwards.

[Larry Wiechman]

 Why not look into sleeving the journals and use a larger ID bearing?

This was a common trick with Yamaha kart engines. The cranks were very soft. I would put a hardened sleeve on a new crank before the bearings wore it out of round. 

[Motorrad]

Doesn't swaintech do a spray on build up coating??

[Captain_Chaos]

Hi Larry,

I have considered a 35ID bearing, but this the following limitations:
-   The area where the bearing sits is worn slightly smaller than the seal face, so in order to get the sleeve on, so the seal area on the journal would probably also have to be machined (I will check with the machine shop, maybe they can get it on without touching the seal face).
-   The 35ID is easily available, but is 17mm wide instead of 19mm (this could be fixed with 2mm spacers)

Sleeving the journal to the original size would be simpler/cleaner.
My thinking is that this is not a highly stressed area, so reduction effective diameter might be acceptable?
I am assuming that the journal diameter was sized by Kawasaki based on the bearing requirements and the fit to the crank web, and not based on the bending and torsion stresses.

Hi Motorrad,

The people I have spoken to regarding hard chroming and metal spraying do not seem interested in working on a pressed crank ? I will however do a bit more research on what is available locally (Johannesburg South Africa).

[Motorrad]

call swaintech   bet they can help ya out..

http://swaintech.com/industrial-coatings/material-substitution/

[Captain_Chaos]

Looks like Swain Tech offer some great coatings, but I would prefer not to ship the crank all the way from South Africa. I?m still researching some local companies.

[Captain_Chaos]

I managed to find a company that can hard chrome and grind my crank
Asking the bike workshops and searching the internet did not help ? I got the details from a fellow rotary fan (he?s currently building a street bike with a 13B turbo rotary motor).

Hopefully I can drop the crank of tomorrow (assembled & trued, but without the rod).

I?m feeling much more confident going this route.

[Larry Wiechman]

 You will still have to OD grind the plating to size and concentricity.

[Motorrad]

somthing to watch out for.... and warn the shop.

Just because the outer crank web is round.....    doesnt mean its true to the bearing..     or actually round for that matter....

so they need to figure that out before they decide to cut the bearing journal off that as a guide...

(had this conversation with my hardchrome guy too)

[Larry Wiechman]

 They are ground using the 60? centers in the end of the threaded diameter and the crank web.

[Captain_Chaos]

Just to clarify, the crank will be sent to the Hard Chromers assembled and trued, but without the conrod and bearing. (i.e. the stubs, webs & big end journal all pressed together)
The hard chrome platers will not disassemble the crank so they will be able to use the crank centres for the grinding. I will need to check with them if there is any possibility of distortion during the plating process.

I don?t have the factory specs on the interference fit.
Do these sound about right to you?
 RH bearing journal 30.02mm (1.1819?) ? 0.0008? bigger than bearing ID
 LH bearing journal 30.01mm (1.1815?) ? 0.0004? bigger than bearing ID
 Seal surfaces 29.99mm (1.1807?) ? 0.0004? mm smaller than bearing ID

[sandblaster]

The platers will grind the journals undersize to clean up and true.
Then they will plate a little oversize and grind to finish.
That way you are assured uniformity of plating and a concentric finish...
Or something like that 

[DoldGuy]

Captain C,
 Your numbers are good.
DoldGuy

[Captain_Chaos]

Just doing a bit of running around.
After seeing the crank, the platers told me they would get better results if the crank was split. (with the crank as a unit, one of the stubs would face down and the web would cast a ?shadow? on it)
The stubs have centers on the inside, so grinding would not be a problem.
The quote for the chrome plating & grinding came to ZAR 480.- (55 USD) so it?s quite cost effective.

On the negative side, they will only commit to a tolerance of ?0.005mm (?0.0002?), so the final journal size will be somewhere between 30.01mm (1.1815?) and 30.02mm (1.1819?). Both LH & RH journals and seal areas will be done to this size.
This is less than ideal for assembly/disassembly but is a compromise I would be prepared to live with.
I will however try to find someone who can to do the final grind to closer tolerances.

[Captain_Chaos]

Got the crank halves back just before Christmas.
The results are quite disappointing.
The journal grinding is completely out (0.04mm undersize) and they decided to charge me more than double the original quote.
The crank will need to get hard chromed again.
I will need to look for an alternate supplier for the grinding once the shops open again.

With all this running about and waiting I would have been better off just ordered a new crank.

Locks like I will have to enter the first race of the season on my RM250!