ppc

I just came across this page that deals with the bizarre idea of running two chains on a bike, when I read the following nugget at the end of the page:

However it got me thinking about another bike I'd seen with a similar set-up but this one made a lot of sense. In 1982 Canadian rider Jocelyn Lovell rode the kilometre time trial at the World Championships in Leicester, England using a bike with two transmissions. His arrangement gave him two gear ratios, a lower gear to get away from the line and a higher gear that kicked in after about seventy metres. His ride in Leicester wasn't as good as he hoped for but the transmission worked well and it could not be faulted by the UCI commisaires.



Jocelyn's bike had a freewheel sprocket on the normal right hand side and a fixed sprocket on the left hand side. As he moved away from the line he drove through the RH sprocket and the left hand fixed sprocket began to unscrew from the hub. It being of smaller diameter it turned at a slower rate than the RH sprocket and being on the "wrong side" of the hub it would naturally unscrew. After about seventy metres the LH fixed sprocket came up against the lockring and at that point drive was through the LH side and the RH sprocket freewheeled. The distance traveled before the higher gear engaged could be adjusted by setting the position of the lockring. The bigger the space between lockring and sprocket at the start the longer the distance before the higher gear engaged.
Jocelyn experimented for some considerable time to come up with a combination of sprockets and chainrings that would not only give two suitable ratios but that would need chain lengths that would be at the correct tension. He settled on a low gear of 42x13 (87.2") and a high gear of 53x15 (95.4")

Wow, that is incredibly clever and a very elegant working around (or within?) the UCI rules. Lovell was a genius. I'm almost tempted to try it myself to see what it feels like

(There's just a small misunderstanding of how the system worked in the above explanation: the LH sprocket unscrews because it is smaller and thus spins *faster* than the wheel in the first 70m, not slower)

carleton

That's pretty ingenious.

I've seen a double freewheel setup using a standard freewheel on the right side of the cranks combined with a LSD (left side drive) BMX freewheels for the left side setup.

LSD exists because some BMXers want the chainring on the left side to get it out of the way if they like to do grinding tricks on the right side.

jtgotsjets

Nahhh man, LSD exists to bring us all together.... man.

jimmytango

damn jets, you beat me to it lol.

seau grateau

Interesting. Any video of this in action?

youngandcurious

https://www.youtube.com/watch?v=hSoMkOhvaUQ three chains, three chain rings,three cogs!

xkillemallx16

tempted to try this

adriano 

if every edge really mattered, why would you want to uselessly spin a freewheel for the bulk of the race?

rustybrown

More of an edge gained by quicker acceleration.

adriano 

did he win?

rustybrown

Everybody wins in a TT

kyselad

But unrelated to the setup described by the OP as far as I can tell. What would be the point of such an apparently identical and redundant drivetrain, anyway?

polobreaka

funny, my bro and i were just joking talking about putting on 2 cranks and 2 cogs just for kicks when i was changing out my drivetrain.

ph4nt0mf1ng3rs

More surface area contact with the mechanism driving the wheel forward? Kind of like the idea between turning a rolling-pin pulley with a string, vs pulling it with a wide belt.

Or something like that.

I dont know Im just making a hypothesisisisness.

chenghiz

This would only be useful if a single chainring/cog was slipping, which it wouldn't be. I imagine the triple chainring/cog setup is just a vanity thing.

ppc

3 chains on one side are useless, and so are 2 chains on both sides. One chain is plenty strong to withstand the effort of any cyclist. Mechanically, only one cog can be fully screwed onto the hub, and only one of the chains can be fully engaged anyway.

So yes, it's all vanity.

youngandcurious

Hmm i posted because it has multiple drive chains i guess and there is no benefit...

vw addict

but r u going to the alleycat? bring your under armor, and aerospokez

adriano 

i need a left side freewheel for a fast start.

WoundedKnee

When I brought my double freewheel to my lbs, he said back in the 80s or 90s some BMX racers had double freewheels with some kind of "shift once" mechanism to get a quick start. That's what I thought you were talking about.