Tandem wheels

[pete75]

Will a 36 spoke front wheel built with strongish components, Exal CL19 rim and DT Alpine 3 spokes, be strong enough for loaded touring on a Galaxy tandem. Riders weighing about 28 stone in total. 40 spoke rear wheel will be strengthened by replacing existing straight gauge spokes with Alpine 3 and fitting a Longstaff axle in the Suzue hub along with a third bearing.

[Brucey]

should be OK but it won't hurt to take a spare axle and some spare bearings with you.

Also... there is the vexed question of freewheels...?

cheers

[pete75]

should be OK but it won't hurt to take a spare axle and some spare bearings with you.

Also... there is the vexed question of freewheels...?

cheers

Never had any problems with them meself. Will be fitting a third bearing into the freewheel itself as per this viewtopic.php?f=5&t=61819

[Brucey]

Due to the usual PPPPPP mindset, I've only had a few freewheel troubles out on the road, but when they come, boy do they come!

All you can do is choose/prepare carefully and hope to stay lucky.

cheers

[kylecycler]

Due to the usual PPPPPP mindset, I've only had a few freewheel troubles out on the road, but when they come, boy do they come!

All you can do is choose/prepare carefully and hope to stay lucky.

cheers

Brucey, what causes a freewheel axle to break: is it age, or stress? In other words, if you replace the axle each time the cones get even slightly pitted, or even just at 'X' miles, as a precaution, should you be ok, or is it not as predictable as that? Could you, for example, suffer a broken axle simply as a result of hitting a pothole or bumping over a kerb (I don't bump over kerbs but sometimes don't see potholes)?

[Brucey]

if you break an axle over a bump it is almost certain that it was cracked most of the way through already, and all you did was administer the coup de grace to the thing.

From my experience of such things and from scientific tests on similar parts I would say that the fatigue life of many bicycle parts is dominated by initiation of crack-like defects, rather than propagation of such defects. This means that in a highly loaded part there may be a one in twenty chance that a crack may start in (say) any one six month/3000 mile period, but also that there might be a one in five chance that any such crack may propagate to failure in the following period if not detected.

in general engineering practice the method is to inspect for cracks at intervals that are short enough that the smallest unseen crack will not propagate to failure in the next interval before another inspection.

If you inspect used parts carefully, and they are found crack-free, they should be as reliable as brand-new parts of similar quality. The used parts may have tiny unseen cracks in them, but they are by definition free of catastrophic manufacturing defects, else they would not have lasted that long, even.

Repeated stress grows cracks, but a corrosive environment grows them faster.

By extension then, if you carefully inspect a used machine at regular intervals, if anything, I'd expect it to be slightly less likely to break in the interval between inspections than a new machine might be.

cheers