Main bearings

wilko · Post by **wilko** » Thu Oct 14, 2010 11:24 pm

Standard Mini's or Coopers? Just curious.

Eric · Post by **Eric** » Fri Oct 15, 2010 12:50 am

At the time all BMC "A" series engines.

As an apprentice with a BMC company from 1958 to 1963 but not with cars you got special visits around the so called flagship factories just so you got an understanding of how fantastic they were supposed to be.

I have a very strong memory of the drop forge shop at Austin at the now defunct Longbridge site where when one of the hammers came down you went up about 1/2" off the ground, they were forging crankshafts.

I would think anyone who lived within 1/2 mile of the site knew they were forging crankshafts as well.

By the way they were also dynamically balanced.

dodger · Post by **dodger** » Fri Oct 15, 2010 8:54 pm

dodger · Post by **dodger** » Fri Oct 15, 2010 8:56 pm

Charles,

What firm metal sprayed your crank? this would be useful info to have filed away for possible future use.

Laurie

Charles · Post by **Charles** » Tue Oct 19, 2010 5:13 pm

I don't know who sprayed them back up as Tony Hartlen at the Rebore Shop sorted it out and he outsources that aspect to specialists. I'll give him a call and ask, if he is still there.

regards
Charles

Groily · Post by **Groily** » Tue Oct 19, 2010 6:54 pm

Not sure about this, but isn't there a question about the exact fit of the rear of the Mini shell option - apart from the tag being on the wrong side and requiring a new notch be cut on the rod/end cap?
I had some -80s in my Mod 20 when I got it a million years ago, and it was fine . . . but then had it sprayed back to standard when they wore out, and it promptly broke the crank. Since then, I've kept within the standard AMC sizes and used AMC bits. Once bitten, etc.
Anyone want a Meehanite 650 crank that would need spraying back to standard, as it's below the limits for JSL-sourced bits . . . NO? The last rods didn't love it either and jumped ship.

paul knapp · Post by **paul knapp** » Tue Oct 19, 2010 11:46 pm

Having watched metal spraying being done, the surface is first prepared by roughing it up by turning a coarse thread over it so the molten introduced metal has something to key into. I have always thought that this would weaken the strength of the work piece by introducing a series of spiral fracture points.
Not something I would be doing on a highly stressed engine component.
The sprayed metal does not increase the strength of the shaft by bonding, it only adds thickness by building up and has a definite separation line.

Groily · Post by **Groily** » Wed Oct 20, 2010 12:47 am

Classic spiral fracture is what did for mine Paul, but all way beyond my ken. Except I think I understand that strength is not imparted, just bulk, and I'm not sure how that works on radii that may not be kosher to start with at the sorts of dimensions we're talking about. Would love to know it's perfectly possible, then the old 650 crank on the shed floor could be used for something apart from a doorstop.

paul knapp · Post by **paul knapp** » Wed Oct 20, 2010 3:55 am

In the same work place, hard chroming was also done to refurbish failed crank journals out of expensive commercial engines. I have seen the plate built up to over .060" thick to save a worn journal and to bring it back to a standard dia.. Expensive process, but the end result left a journal that out lasted the original, as the chrome is extremely hard wearing. We also built up small engine cranks, but they were not to many as the cost came into the equasion.

laxy · Post by **laxy** » Fri Oct 22, 2010 12:21 am

T&L Engineering in Bedford metal sprayed my 650 crank and reground back to standard.They came highly recommended and do a lot of AMC cranks.The bike is at last up and running and Ill report back if any problems occur as a result of the crank refurbishment