A10GF Crank quesion

[scotty]

Greetings

Other than an intro post quite a while back, this is my first post. I've finally stripped the old 55 GF down to a million bits.

Sludge trap plugs were a bugger (3 nights of persuasion) but managed to get them out without destroying female threads.

Just got the crank back from machine shop and she's now ground -.010

Eng # is CA105743 .....the flywheel is bolted to the crank with 6 bolts and the sludge trap did not have a removeable tube but a gallery that I've cleaned out.

I'm trying to figure out if I have a large journal crank or a small journal crank ???

Any wisdom would be greatly appreciated

Thanks alot

Scotty

[RichardL]

Look's small to me, but a dial caliper or micrometer around it would tell a lot. About the tube in the sludge trap, I thought that the tube acted as the sludge separator, but I have the later type of crank and maybe these earlier versions worked differently. The point being, you definately need to make sure that a previous owner didn't just decide that he didn't need the tube.

Richard L.

[LJ.]

Looking at the sludge trap which looks small in diameter, and there is no way a trap tube could be inserted in there like on the later large  journals, I think that might answer your question, BUT... I know very little about these things so please dont take my answer as cannon.

Scotty, did you read the thread that Dark_knight87 started? might be some useful info there for you...

http://www.a7a10.net/forum/index.php?topic=661.msg4026#msg4026

[A10Boy]

As I understand it, large journal cranks were Da10 on, and all CA10s were small.

[Brian]

While we are on the subject, does anyone know when they went to the radial bolted type crank ?

[trevinoz]

Definitely small journal.
As to when the radial bolted cranks were introduced, 1958 for the Flash. Not sure for the Rocket as they used a large journal one piece crank from probably 1956. This crank is much heavier than the later radial bolted type.
According to the parts book , the first Rockets used the small journal crank and thin flange barrel.
Trev.

[scotty]

Thanks for the replies

I think its safe to say I've got a small journal crank.

In this mornings post I received the beezer twin resto book by the baconator that seems to concur.

Thanks again for the wisdom 

Scotty

[dpaddock]

The 3-bolt flywheel and tube sludge trap was first fitted to the RR in 1957; the GF got one in 1958.

BSA Service Sheet 207 seem to show 'small' (1.45 inch) crankpin diameters for 1950 thru 1957 GF, and 1.677 inch thereafter. The RR got the 1.677 inch crankpin in 1954.

Mainshaft diameters are nominal 1.36 inch for all A10 models.

[wardleybob]

Re large journal crank 1.686 is standard