Question about good ol' cottered spindles....

[Paulmh]

I'm still restoring a 1950's BSA girls' "Airborne Bicycle". By a stroke of bad luck the paint sprayers have lost the bottom-bracket (BB) spindle, lock-nuts, cones and bearings, bless them. The bottom bracket shell is 56.5mm long (most old bikes have BB shells of 68 or 73mm, I believe). The internal diameter of the shell is about 34mm, which I think is near enough standard. I reckon the chain line is 36.5mm and from this, if I work out the overall length that the spindle / axle needs to be it is 120mm, near enough, assuming symmetry of the pedals / cranks each side of the frame. I've fitted a period 3 speed Sturmey Archer hub, by the way - a departure from the single speed hub that was originally fitted, but that hasn't altered the spacing between the rear forks or the chain line.
A question arises; if I try and alter an oversized spindle, should the cotter-pin recesses in the spindle be equally spaced either side of the centre-line of the frame? I would have thought so because one wants the pedal crank arms to clear the chain stays by the same amount each side.
I only ask because every old spindle I come across has different spacing from the bearing "cones" to the cotter-pin recesses each side. That would make sense if there were 2 or 3 front sprockets, but where there is only 1, why would the spacing need to be eccentric?
Apologies if this is all obscure techno-babble but I'm learning as I go along. Anybody know what I'm banging on about?
Toodle pip,
Paul

 

[sidevalve]

It depends on your engineering skill and equipment available. If you are to alter an oversize spindle I wonder how you are going to make the cotter pin slot. If you are turning the spindle down I would have thought the easiest way would be to fit it then the cranks and mark the position to suit, then use a mill of the correct size. However I would check E bay very carefully first as there are often "old stock" items being sold off by dealers, or, and this may be a longshot, try to find and "old school" bike shop [there are some still around] or a bicycle recycle scheme as these too often have old style spares to sell on. A few days searching may be a lot easier than the considerable work involved in creating a spindle and old spares are often very cheap.

 

[Paulmh]

Thank you Sidevalve. Sorted!! I heard about a bicycle jumble in Ripley last Saturday. I think it was organised by the Veteran-Cycle Club, which I've now joined. What a completely wonderful experience the jumble was. So many brilliant, informative, friendly stall holders and so much bicycle stuff in old oily boxes and trays. One stall-holder said, "Here you are mate, see if these fit your bike, pay me something if they do". They did fit!! Next time they hold a jumble sale I hope to take my grand-daughters fully restored BSA Parabike to show the end result. A couple of months more work and it should be done.

 

[raindog]

A couple of months more work and it should be done.

we'll expect to see photos in here