I'm not too familiar with splined crankset designs, but this seems like it would allow a splined crankset to be used with a square taper bottom bracket: an anular insert with an exterior that matches the interior of the crank arms, and an interior that matches the taper profile.

Thoughts?

cartridge style BB are so cheap these days, why not just get a BB that matches your crankset?

never heard of anything like it.
even if there was such an adaptor, the cranks would sit out very far, giving poor chainline.

i feel very confident that this would be a very bad idea. Not only for the aforementioned chainline issues, but for the worries about the whole thing staying tight and reliable, plus the question must be asked: which isis or octalink crank is worth that kind of silliness?

-rob

For the record, I don't need anything like this.

I was just wondering if there would be any technical obstacles; so far, it seems that chainline would be the only one (I don't think that keeping it tightly secured would be any more of an issue than with any other crankset and bottom bracket [as long as there's an inner shoulder to keep the crank arm from sliding inwards]).

Of course, it's also nice to hear from those with more sense than creativity.

The cost of such adapters would be at least the same price as a BB to fit the crank arms. What you're after is a rather fancy bit of kit. Also the whole point of a splined crank such as Octalink or ISIS is to reduce the flex in the BB. So why would you WANT to install an adapter that allows you to use a splined crank arm set with a square taper BB?

So basically you've come up with a solution to a question that no one has ever asked or that anyone SHOULD ask. Don't feel bad though. I've done the same thing far more than once...

That would really screw up the Q factor and chainline. Figure this would make the pedals about 3 inches or more wider apart. Also since it is such an odd shape and small in size it would be a real PIA to machine this out of billet tool steel.

The cost would likely exceed buying a new cartridge bottom bracket as there's no economy of scale on something like this.

the only possible use, I can think of, is for threadless BBs.

Echo #2 Just Buy the matching splined BB . ..

[unless you own a manufacturing facility to make what you propose]

In case it was misunderstood, the entire piece in question would sit within the splined cranks, except for the inside shoulder that I mentioned in my second post. Assuming such a set up is possible, why would the crank arms be moved so far apart (up to 3", by MikeW's estimate)?

Of course, BCRider is right about the practicality and desirability of such an adapter.

However, I will say that this idea came about when thinking about the type of bottom bracket to use in an upcoming build and dreaming of far-off touring: wrestling with the serviceability of cup-and-cone bottom brackets, the availability of cup-and-cone vs cartridge bb's in such places, the disposable nature and increasing prevalence of cartridge units, semi-cartridge bearings like Phil Woods and the matching axles, required tools, etc.

Replacement axles for loose ball bottom brackets are no longer made, and I know of nowhere
that you can get pits reground out of their races, a logical way to reuse old parts,
but no economic support.


for a self supported tour.

square taper seems to still be supplied, the spline schemes were a passing fancy,
and there were never any variety of axle lengths
like there is in square taper..

I have used same crankarms , on 1 bike that needed a 118, and another 127.5, as the tire clearance between the chainstays , and the chainline required.

have you considered a one piece crank? heavy but really durable and all parts are cheap.

back in the 80's there were tubular one piece crankarms, I thought they were quite an elegant piece, all and all.

********************? I have at least 3 sources that still stock them.

name them, Dan.
Ordered thru current Wholesaler or just old dealer stock .. all lengths?

for repairs, 2 kinds .. solid, nut holds on arm, and hollow , bolt threads into it.

Quality sells 'em. Happy to ship to your local dealer.

You can also get 'em thru Harris and from Euro-Asia. Sugino and Miche both make 'em, as does Odyssey. They're not common but they are certainly not unavailable.

Why even bother? The replacement of a loose ball with a cartridge bottom bracket is way too easy.

fietsbob, I did consider one-piece cranks; my main objection is that their pedal threads are 1/2", not 9/16".

As for the availability of bottom bracket axles, I would like to build a fixed gear, and I'd need an axle that is shorter than what most cranksets require (although, with modern road or mountain bike frame spacing, I suppose a longer bb axle could be used if you rearrange the spacers and redish the wheel to correct the chainline--not practical, though). I suspect that high end Japanese cup-and-cone bottom brackets and parts will always be around, but they can be kinda pricey, and one is unlikely to find them in most shops.

As a side note, I just awoke from a late-night nap in which I dreamt that I disassembled my bottom bracket (which looked more like a hub) to find that my bearings had turned to dust. Maybe that's a sign of some sort. In this dream I also saw a prostitute who hangs out on my block sometimes.

What did the you do with the prostitute and your bottom-bracket that turned the bearings to dust???

I guess I needed the grease...

Note: there is a model of SCOR 'knee saver' that is a 1/2'' to 9/16'' pedal adapter,
as it widens the stance a bit also..