6 Bolts or Splined adapter for Bottom Brackets ?

[qwerkus]

Hello,

I want to use a standart BB (tapered, isis - doesn't matter) as jagshaft. This would require a way to mount sprockets on both sides - unfortunately, cranks only come with 104 odr 130mm bcds, which is too large for small sprockets. So milling a crank is not really an option (besides beeing quite wasteful!).

Does anyone know a good source for 6 bolts (44mmbcd) or splined (cassette-style) adapter that fit standart bottom brackets ? Shipping to EU would be a plus!

Thank you for your help,

qwerkus

 

[offGridDownUnder]

I want to use a standart BB (tapered, isis - doesn't matter) as jagshaft.

I don't know enough about what you are doing to know if this is useful - tandem cranks mount sprockets on both sides.

 

[offGridDownUnder]

Hello,

I want to use a standart BB (tapered, isis - doesn't matter) as jagshaft. This would require a way to mount sprockets on both sides - unfortunately, cranks only come with 104 odr 130mm bcds, which is too large for small sprockets. So milling a crank is not really an option (besides beeing quite wasteful!).

Does anyone know a good source for 6 bolts (44mmbcd) or splined (cassette-style) adapter that fit standart bottom brackets ? Shipping to EU would be a plus!

Thank you for your help,

qwerkus

Also, Problem Solvers and some track bicycle specialists make sprockets that mount to 44mm BCD ISO pattern disk rotor mounts.

These people are selling off the last of the components they made - there are cranksets and 44mm sprockets. I bought a few of their 44mm mount sprockets before I switched to a Gates belt. I think I have unused 22T and 16T and maybe others. See if they have what you want:

VeloSolo - Main Shop

VeloSolo Fixed Wheel & Singlespeed Bike Shop - disc hub mount cogs and specialist parts and accessories for singlespeed and fixed wheel bikes

velosolo.co.uk

Using their names try searching for others that make the like. There are some people here in Oz that make entire cranksets from billets for a price.

 

[qwerkus]

Thank you for your reply. Finding sprockets is no the issue - the tricky part is to mount them onto the BB:

 

[offGridDownUnder]

the tricky part is to mount them onto the BB

The tandem idea bears no fruit? I know some tandems use Gates belts, but I haven't researched this use case.

On my trike, at the motor with a 39T Gates sprocket (4 bolt) and at the rear with a 60T sprocket (5 bolt) both were mounted using the 6 bolt 44mm BCD ISO brake mounts (on the left in both cases). There is a picture showing some view of both further down the thread in my signature. I designed the spiders and had them laser cut.

Currently I have a 26T sprocket directly mounted to the brake rotor mount on the motor (no picture) and the same 60T sprocket on the rear. I have a 22T sprocket and a 48T on the way to try.

I would look at a similar adapter doing the opposite job - matching a 104mm BCD or 130mm BCD crank spider to a 44mm BCD 6 bolt Gates sprocket (as you show above). With a tandem crank having spider mounts on both sides. But the belt line might be an issue.

Failing that, there's always welding a custom adapter to the machined-down stub of a suitable crank spider - those parts are small enough to go in an oven after to recover temper. But better to buy if someone has already made it.

 

[qwerkus]

The tandem idea bears no fruit? I know some tandems use Gates belts, but I haven't researched this use case.

Good idea, but also not easy. Tandem chain usually go from crank to crank. Those using left side drive up front need freewheel adapters with much larger sprockets than mine. I guess machining is the only real option. Not that hard either: I just need a cheap crank with a sprocket pressed in that has enough metal to drill the 44bcd holes.

 

[Chalo]

Does anyone know a good source for 6 bolts (44mmbcd) or splined (cassette-style) adapter that fit standart bottom brackets ?

You have other options. BMX cranks feature things like small (23T or even less) drive sprockets, 48 spline direct drive sprockets, and right side/left side compatible cranks.

A BMX or external cup bottom bracket can be used to hold a keyed shaft with industrial sprockets or freewheel thread adapters mounted on the ends.

Trials bikes have cranks with RH freewheel threads at the base of the (right side) arms. Those can mount freewheels as small as 16T or fixed gear cogs as small as 13T.

 

[qwerkus]

You have other options. BMX cranks feature things like small (23T or even less) drive sprockets, 48 spline direct drive sprockets, and right side/left side compatible cranks.

A BMX or external cup bottom bracket can be used to hold a keyed shaft with industrial sprockets or freewheel thread adapters mounted on the ends.

Trials bikes have cranks with RH freewheel threads at the base of the (right side) arms. Those can mount freewheels as small as 16T or fixed gear cogs as small as 13T.

Interesting reply. I'm not sure how I would fit a belt sprocket on a bmx crank, but the trial crank thread could work. Do you know if the threading is the same as for one of those 6 bolts adapters ?

 

[Chalo]

Interesting reply. I'm not sure how I would fit a belt sprocket on a bmx crank,

BMX bottom brackets have open cartridge bearings in them, mostly in very common sizes: 19mm or 3/4", 20mm, 22mm, 7/8" or 22.2mm. Road bike and MTB external cup bottom brackets are available in 19mm and 24mm, or 25mm if you take the plastic sleeves out of a 24mm one. Industrial belt sprockets for keyed shafts are easier to get than bicycle-specific 6-bolt sprockets. So if you can get sprockets for one of those diameters, you can use a piece of keyed shaft instead of a BB spindle.

but the trial crank thread could work. Do you know if the threading is the same as for one of those 6 bolts adapters ?

View attachment 348597

It is the same thread.