Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties So... I'm trying to find a frame...

So... I'm trying to find a frame...

Post Fri Jan 06, 2012 6:10 am

Posts: 14
As of right now, I have two that I might adapt, but it'll take awhile.

A 70's shovel head soft-tail, or an early 70's Triumph triple frame (trident).
The shovel frame weighs a ton, but I really like the idea of a soft tail flathead harley-
The triumph frame is cooler, but with only an ARC welder I'm guessing the mods I'll need to make are too numerous.

I'd like to get an Ariel plunger frame (just missed one on eBay) but I don't know how much work it takes to make one fit.
Just welding in motor-mounts I hope?

I dunno...
Also love to rock a wl frame or something, but those cost a bit more, and I wouldn't want the guilt of butchering a stock one...

Idea's, suggestions, opinions?
Anybody want to trade??? I got some triumph stuff and chopper stuff... and a long girder that's been cut, but not re-welded.


Post Fri Jan 06, 2012 8:50 am

Posts: 1654
I can't comment on the soft-tail frame, apart from your obvious remark about the weight. However I'm pretty sure you will find that the Triumph one is about 60mm too short in the main loop.

Don't get involved with plunger frames, they are heavy and have numerous sliding joints which wear like crazy and produce various odd handling effects.

For a 45 special, I'd suggest either a repro rigid Big Twin frame of some sort - this will be fairly easy to find and probably slightly lighter than the 45 unit, but leave you with various transmission issues; or, look for the front half of a oil-in-frame BSA or Triumph frame. This will take the engine in the main loop and you can easily find an aftermarket back end about 4" longer than stock which will give room for the gearbox behind the seatpost.

The BSA A10 frame is much easier to cut and shut than the later one as it is all-welded tubular construction. See Dr Dick's bike for how this works out in stock form. A10 frames are quite hard to find now, though. Norton Featherbeds will take the 45 unit but they have been making crazy money from the classic road racers for many years
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Fri Jan 06, 2012 7:21 pm

Posts: 14
I'm very interested in the OIF approach...

Any pics anywhere?


Post Sat Jan 07, 2012 3:22 am

Posts: 1654
I'd suggest trawling about on Jockey Journal for a bike like that. One here in a stock Triumph rigid frame ... umph+frame which interestingly enough has the engine and trans in the stock locations; poster says it will fit, and there's the photo.

You could also use the front section of an earlier swing-arm frame, the results would be similar in terms of geometry and the appearance would be better.

"Back in the day", bikes using 45 engines and British frames and transmissions were built in some numbers in the UK, because the components were available. The most common approach was the cut off the top tube in front of the seat post and fabricate a new front section, keeping the various forgings etc for transmission and oil tank mounts. Also, British frames tended to have more ground clearance than American ones so the "British" style of chopper tended to be less concerned with raising the front of the frame, although there were plenty of real horrors about.

Another approach was to take the widely-available BSA M or B series frame and extend it by cutting and extending the single top-tube, along with the lower frame rails if fitted ( the M33 and M21 have them, the M20 may or may not, the B31 and B33 don't - but any rear section fits any front section ).

Any British frame conversion leaves you with the task of fabricating the engine mounts, you really need a frame with full-length bottom rails to accomodate this - the 45 engine isn't designed to be used as a structural frame member, unlike the Indian Scout/741 unit.

Interesting to see another bike so similar to my project on this thread. I came to the conclusion many years ago, after owning a bike of that sort, that the Ariel was much the best suited of the period rigid frames for the purpose, although always difficult to find and tending to vary in detail between successive batches - the downtube length varies, for example; the forks have several different configurations, but they are all more-or-less interchangeable as complete sub-assemblies.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Wed Jan 25, 2012 1:47 am

Posts: 14
Hmmm, yes I am thinking all of these things over...
What I'd really like is just the engine cradle from a servicar frame, then I could fab my own rear end on. :roll:
(I'm working within a $1000-$1500 top-price range. I don't like the paughco's or the big, dual-uptube frames. If I wait long enough my frame might show up in my price range though, right?)

I was just talking to a guy who had a slightly raked servi but he said he wanted $5 for it and it wasn't really a $500 frame, IMHO. But, I guess any frames are hard to find or something? 'Cause it looks like his sold.

I really like the Ariel frame/45 motor "look", they look so cool! Were those more popular in Europe? (Shipping would probably kill me, but if they are easier to find it might be an idea-)

Oh! And I just got a pre-unit 4-spd!
Woo-hoo! Slowly but surely!

Post Wed Jan 25, 2012 2:08 pm

Posts: 1654
Ariels were and are rare in Europe and the US, but they were imported into the US and used with some success on the dirt-tracks. I have three frames which I've picked up by word-of-mouth over a long period of time. You probably have about the same chance of finding one in the US.

The main thing about the Ariel fame is that it is about 2" longer in the engine bay than the equivalent Triumph and BSA units, also the original design includes a short down-tube with plates spanning the gap to the bottom rails. This was originally intended to provide room for a dynamo on some pre-war models but was kept, partly for no real reason and partly to make the frame usable for just about any engine in the range.

This means you have room for the generator on the 45 in a cut-out on the engine plates, and the plates span the gap so that the engine is not acting as a stressed frame member, which 45 engine mounts are not designed to do. The Ariel rigid
frame is one of the few British frames which will accept a fully-equipped 45 with no cutting or welding
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Thu Jan 26, 2012 5:01 am

Posts: 14
Good info!


Post Thu Jan 26, 2012 5:40 pm

Posts: 159
Are we talking SQ four or single Ariel. I have a project in mind?

Post Thu Jan 26, 2012 8:17 pm

Posts: 14
Yea, square four, not single.
(stuffing a v-twin in single sounds like quite a chore)!

Post Fri Jan 27, 2012 12:46 am

Posts: 1654
All 1940s - early 1950s Ariel frames will take the 45 motor. They are not completely interchangeable - the length of the front down-tube varies between specific models and may require bending slightly to clear the generator on some cases - but they will all serve.

Don't get involved with plunger frames. They have numerous wearing parts which are very difficult to replace if missing or worn, and handle poorly in any case. They are, strictly speaking, a form of short trailing link rather than the vertical plungers used by BSA and Indian, but they have most of the same problems and a few quirks of their own.

They originally used Burman gearboxes, so you are best with a gearbox fitted with lugs top and bottom, but the BSA type with two lugs underneath can be accomodated if required.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Mon Jan 30, 2012 2:44 pm

Posts: 3
Location: Montana, USA
This frame came from an Ariel "Red Hunter" (Single) modified to fit the 45. Bought on Ebay for $250.00, so keep loooking. The single downtube was "massaged" in a pipe bender and the lower tubes bolted/welded to the lower frame. Tried to keep the "gooseneck" lines.
In "The Horse" magazine, there was a motorcycle with a 45 Flathead front with engine mounts welded to a triumph rigid rear with trans mounts. Looked very cool. Looking forward to seeing what you come up with Justin!
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Post Tue Jan 31, 2012 1:35 am

Posts: 1654
I like the front engine mounts, which are neater than mine. I have used two frames at various times while building my bike; the first one had the front down tube tweaked ( about 6mm ) with a cold bender, then I found a second frame with the shorter front down tube which didn't need it and used that instead.

My bike has footboards and footboard side mounts using a combination of NOS, repro and second-hand parts including a WL right side set and a Servicar left-side set ( I decided early on to use the left-side pedal as a footbrake as it was the simplest solution ). I was going to use a NOS side stand but in the end, didn't do this although I still have the parts and may yet fit it.

We made a set of plates ( because we could ) to see how it all fit together and that became the approach. They provide locating points for the top of the gearbox, footboard bolts, primary cover and a couple of other odds and ends like the oil filter and bottom of the battery tray.
Shoot, a man could have a good weekend in Dallas with all that stuff...

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