1948 Sq4 basket job - help!

[Roger Gwynn]

Check the parts book for the Burman number of the shell and find a gearbox with that shell number, that way even if the insides have been mucked about with you will have the correct shell to use as a basis.

[RayBlack]

Thanks Roger and Nev. I will get a better idea of exactly what I have to work with next week when I visit my friend with the mountain of parts. It is indeed a great pity the original owner of the the Ariel parts cache felt the need to dismantle and store without labeling the majority of the bikes he collected...

[paul.jameson]

To identify the gearbox shell and the different mountings for singles and Square Fours, the following note from Cheval of around 1988 remains relevant. I had just done the same trick as Nev by cutting the mountings back on one side and using the cut off bits as spacers on the other side to fit a singles gearbox into my Square Four. The other point to remember though, is that the Square Four mainshaft is 3/16" longer than the Singles mainshaft. You need both the long mainshaft and the altered mountings to convert from Singles gearbox to Square Four.

[RayBlack]

Thanks Paul. That will be useful information if the correct or near correct gearbox cannot be found.

[RayBlack]

I have just heard from my friend with the parts pile. It turns out there is a choice of two '48 plunger frames: AX491 and AX532. There is a choice of three useable crankcases: CJ549, CJ401 and CJ 494. It would be nice if a couple of these matched up.

[paul.jameson]

Sorry Ray but no matches. Both frames are in fact 1939 frames but the engines are all 1948. They will, of course, fit together perfectly but you have a good reason for negotiating a lower price.

[RayBlack]

Thanks for checking those Paul. I have a list of frame and engine prefixes by John Mitchell. That states the sprung frame had an AX prefix in 1948. If that is correct, what numbers should I be looking for (there are several other frames available).

[paul.jameson]

The AX prefix runs through from 1939 in a continuous stream of numbers. For 1948, AX950 - AX1250 are about right. Above 1250 you may be coming into the 1949 model year but still with the cast iron CJ prefix engine as the Mk I engines didn't become available until January 1949. The 1949 model year frames with prefix GS began to appear in September 1948 but Ariel, as usual, used up their stock of the previous year's frames at the start of the new model year.
Come back to me as necessary with other frame numbers.

[RayBlack]

Thanks again Paul. I will get my friend to search the less desirable (ie in need of work or repair) frames for a later number.

[RayBlack]

There is another frame with number AX1280. It is beyond the '1250' that you stated may be the upper limit for 1948 model year Paul. Is it possible to check this number more definitively? And does it possibly match one of the sets of cases that are available? (CJ549, CJ401 and CJ 494)