crankshaft grinder

1608 · Post by **1608** » Fri Mar 02, 2012 1:32 pm

I would be interested if anybody could elaborate on this point a bit more. Such as, was this radius requirement featured on any other makers machines or is it peculiar to AMC because of the reputation of the twin cranks breaking. Was the radius still needed on the 'noddy' crank. And, was it a feature on the early 50s ones or only when the 650 was blamed.

ghost123uk · Post by **ghost123uk** » Fri Mar 02, 2012 1:59 pm

quote:
Glad its taken in the spirit it was meant John. Too many people seem to be overly sensitive in my view, especially when its in the written form as on this forum.

I use a lot of forums and find it helps when you become familiar with a persons style, misunderstanding then become rare

quote: I love reading technical manuals etc, even been known to read one in bed, helps send the missus to sleep. [and] ps. I wouldn't sleep at night if my bike was kept 200yds away, and keep the manual in the house, its far more convenient. You can be revising whilst convalescing too.

I thought exactly that as I was typing my last reply ! I know what I will be reading tonight to distract me from the discomfort !

Back on topic =

quote: The 9/64" dia radius is formed btn the main journal and the web and similarly 3/32" btn cntre bearing and web This is believed to maintain the strength and integrity of the whole structure.

Makes sense, we do that with the tiny con rods and cranks in our racing model aircraft engines for the same reasons. In fact we do it to the structure of the airframe too. It spreads stresses over a wider area and so dissipates them. (easier to imagine in the mind than type, for me anyway !)

alanengineer · Post by **alanengineer** » Fri Mar 02, 2012 2:40 pm

I also think forums are good.It is easy to forget how difficult it was to get knowledge before the internet came to our rescue.
The bike handbook, parts book and the Bacon book was all i had. And some of the London dealers (now dissapeared) didnt help by not passing on knowledge.

bjork · Post by **bjork** » Fri Mar 02, 2012 7:41 pm

Ref Johns question about why radius? It is a standard feature on crank journals of all one peice cranks. A standard engineering practice to strengthen any component that has material at 90 degrees. Helps spread the load/stress and avoid fractures. So any shell bearing crank should be done this way or they really do break!
I'm convinced that half the broken AMC cranks were ones that were badly reground rather than being duff in the first place.Edited by - bjork on 02 Mar 2012 7:42:42 PM

charlieb1954 · Post by **charlieb1954** » Sat Mar 03, 2012 12:36 pm

thank you all, i travel abit as my work takes me away to all places i contact T & L and delivery them, see if he will do a deal on a few, and maybe he can tell me the differance between 500 and 600 ones . thanks

SPRIDDLER · Post by **SPRIDDLER** » Sun Mar 04, 2012 5:00 pm

quote:
As I am on a learning curve (and like to know stuff) could someone tell me which radius is being referred to here please ?

Looking for something else (grey and raining all day) I came across drawings of the twin crankshaft showing the critical radii if it it's of interest/use. See Page 22 for tech info on regrinding and Page 24 for drawings, here:

http://archives.jampot.dk/Book/Workshop ... GH_RES.pdf