Britbike forum Forums British Motorcycle specific Brands Velocette forum Rigid MAC Frame

I'm again reaching out to the collected wisdom of the forum.
I'm collecting parts for a mongrel MAC. I have located a frame numbered MB 1242 and would like to know the approximate date of manufacture. I saw an auction listing for a bike MB 2618 that was from 1946.
Any thoughts appreciated!
Tom

Using the Ivan Rhodes book as a go by, your frame is early '46. 1294 is the earliest post-war frame number he quotes and that is said to have been dispatched in March of '46. I have a '46 MAC with frame number 1160. The MB prefix is said to have come into use in 1940 and was used again post war. Military frames have the prefix D according to Mr. Rhodes. Velocette numbering was a bit hap-hazard so definitive dating is hard to obtain. I assume your frame has the cast bottom section as first used on military bikes. Your bike should have Webb girder forks which were in use until sometime around 1948. Good luck with your project, they are fun little bike and very resilient if properly built. I have a good supply of parts if you need any (I assume WA is Washington state and not Western Australia. I am in California).

Thanks for the response!
I don't own the frame, it is one I found for sale. I'm still weighing options for the alloy MAC engine that I do have! I like the idea of a girder/rigid bike, but I also appreciate a more standard machine.
All of my bikes started as either a bare frame or engine and built up from parts. Nothing silly mind you!
How difficult are the Webb forks to find?
Finally, yes, I'm in Washington state.
Tom

Don't assume that the later Alloy MAC engine will fit in the rigid type frame.
Check before you buy.

Webb forks? Hard to find... be prepared to pay a four-figure sum, even for a rough / incmplete fork.
It doesn't necessarily need to be a Velocette fork, -Webb made forks for many different brands.

I think you need 'Lightweight' Webs, not 'Heavyweight' Webbs. You'll need to get measurements - I'd find an owner with the correct forks and get the major measurements so you can find same or similar. 'Blades' Length, Steering head measurements, links lengths, etc etc. They are very tricky to set up properly.

I built a MAC racer, but I used heavyweight Webbs off a Norton - they worked, but I wouldn't do it again.
Remember that the earlier Iron MAC motor -with a few upgrades is thought to be a better option for race/tuning.

There were three ranges of Webb girder forks; light, medium and heavy. MACs used medium, GTPs used light. Different tube diameters and dimensions. All are hard to get. I had a MAC that had light weight forks fitted but they looked very spindly.

All the more reason to use a swing arm frame!!

Rigid and swing arm MAC engine cases are different. The rear engine plates are different and the primary case mounting is different. Mix and match on a Velocette is not as easy as other makes. Even rigid engine cases for MACs of various years are not inter-changeable without modification. I would have to say for Velocettes the best approach is to buy a machine where all the major components are there and are compatible. I've assembled a complete rigid MAC from gathered parts but it was a slow process and a real learning experience.