Bsa Airborne Crank Arm Variations ?

[JOHN DANGER]

I was lucky to find a very nice original BSA airborne folder recently but unfortunately it is missing the original sliding pedals, I noticed the crank arms were different than my other that had sliding pedals, I figured the arms might have been changed out with a nonfolding military bsa to add standard pedals, but the holes were not threaded and the paint a perfect match, so I decided to dig a bit and found other very original bikes without the wider crank pedal end boss, I imagine this is a late or early thing , but I have seen early bikes with both styles, as well as later bikes with both , does anyone know anything about it?

Here is the common wide bossed crank

 

[JOHN DANGER]

and the narrow version

 

[JOHN DANGER]

narrow

 

[JOHN DANGER]

and even a drawing with the narrow crank end

 

[Mercian]

Hi John,

Late reply, just came across it.

It was discussed some years ago in the UK, but no real conclusion was arrived at.

The best anyone could guess is that the extra boss gives a greater surface area, so spreads the load and stops the 'pedal' from being so easily bent when pedalling hard. As such it would be a modification and a 'late' thing, but there is no hard evidence.

Best Regards,

Adrian

 

[Houndsworth]

I have the narrow ones on my early models, S/N 12XX and 5XXX. My late one lacks the correct crank/pedal/chain wheel assembly (I need this!)

 

[Willem]

althe info adrian send is good information,
you are quit right, the early bikes didnt and they bent, also the conversion on the folding bit was made more sturdy and the 2 patrn was one downtube becouse the first patern was breaking or bending at he bottem, some of the verry firts seem to have had normal pedals, you could see it in the convertion couse they still have tread for the pedal instead of sliding pedal, wat you have is a verry nice example of the first patern, but not the verry first,chainwheel and cranck should be able to find, but original expensive, would not do to much about the sadle, if it works,,,, finding original, or replica of the bsa 40 sadle wil be a bit of a fortune,, use a period correct one like the BROOKS 17.... wil do fine.paint,,,, leave as is ,cous there is some value and a respray will spoil that, jusst oil rag,,, would chance the brake cable, take the awful bold and nut out.,,,, foldigpart you can easily chance that by reworking a bolt plus the flange, by putting a bolt upside down and make it that the nutflange does not come of, it should not,
have fub with it a nice bike
and if it is of anny help, have to do some slidingpedals for mine, this winter and going to make a complet set incl BSA chainwheel 46/48 theeth

tada