[Old_Dude]

I was talking to the expert wrench at the LBS the other day & we were talking about the future of mountain bikes. He thought hub transmissions would never make it to mountain bikes because they're heavy & with suspension it's just not a good idea, & blah, blah, blah.

So, I was thinking, why doesn't somebody make an internal transmission located at the bottom bracket. I just keep thinking the whole chain, cogs, derailleur thing is so primitive. What about shaft drive or single sided swingarms (like so many motorcycles)?

I really love the belt drives on a few bikes out there - very, very cool.

Just thinking.

 

[oldfart]

Two reasons: Heavy and internal friction. I think there have been some attempts on some DH bikes. Shimano had a system that Herbold used briefly. Driveshafts have been used a long time ago. I have a book with photos of bikes through the ages and it shows some WW2 era bikes with shaft drive. Lots of full suspension army bikes too. But the roller chain drive train we all use is one of the most effficient machines known. Its really hard to make an internal hub as low friction and smooth as external stuff.

 

[SwitchbladeWD]

When I was in Japan, a buddy of mine ran across a bike with shaft drive. It was very heavy and inefficient. Too many gears and crap changing rotational direction and such.
Shaft drive on performance motorcycles has also suffered a pretty checkered history. Most performance bikes still run a chain. Shaft torque has too much effect on the rear suspension. I don't know that a Bicyclist can generate enough torque to incur shaft torque, but it's a pain on a motorcycle.
Shaftdrive also limits the ability to easilly change the final drive ratio.
A one sided swingarm..... now that's a thought! Imagine a Cannondale with one leg up front and one in the rear! Gives me a headache thinking about it.

 

[Shibby]

there's something called a Mountain Drive that has a 2-speed clutch inside the BB... something with planetary gears....

 

[Rik]

at school, my year long major project was to design and construct an alternative to derailluers... it never happened. you know why? you cant get more efficient than chain drive
the current system is so light, works so well and cannot be improved much more than now...


although i have seen 3speed bottom bracket drives, and a new zealand company mounted the rohlff 14spd hub into their frame (not on the wheel) and those seem like 2 alternatives, but they'll never take off