Super simple Retro-Direct

[John in CR]

Now that I've pretty much decided to get my hub motor out of the wheel, because I absolutely must have variable gearing, I've come up with a 2 speed the old fashioned retro-direct way, with the lazy John easy way twist. Instead of snaking and contorting a single chain around, or paying a fortune to get the right parts and fab others for Miles version, I can just run 2 chains, one on each side of the wheel and each side of the hub motor. Each connection at the wheel and motor will have a freewheel, so 4 in total. At the wheel on one side, I'd need 2 strong idlers so the outside of the chain wraps around the wheel sprocket, so when the motor spins backwards it spins that sprocket forward.

Then all I need is switches for 2 hall wires and 2 phase wires to enable reverse, and probably a disk brake with e-brake cutoff on the motor to stop it when I'm changing gears (trying to change motor direction while spinning fast in the other direction is liable to blow a controller unnecessarily).

All I have to fab is hub with threads on both sides (which I've done before), threads to accept a freewheel on the other motor cover (which I've also done before), and secure the freewheels that will want to unscrew under power (right side motor and left side wheel).

It ain't elegant, but it's guaranteed to work flawlessly, and I'm not restricted to using bike chain and can even use belts instead.

SWEET! I've got my hub motor 2 speed drive with whatever gear ratios I want, and no mountain can stand in my way. No dual motors to rig and test, no more worrying about how I'm going to climb that mountain. Just a long low bike, a powerful and reliable hubbie, and a bunch of batteries. I knew there was a good reason my brain kept me up all night. Time to hit the rack and catch a few Z's.

John

 

[TylerDurden]

Not bad, but I think stacked freewheels on the right side would be simpler:

Bottom-bracket cup to marry the freewheels together
Idler cog from derallieur (strap iron to hold idler)
Turnbuckle and spring to maintain tension

N'est-ce pas?

http://www.efball.com/gears/

 

[John in CR]

True, I forget how elegantly simple the original is after not seeing it in a while. I've just been worrying about bicycle chain and twisting it under load, especially since my big hubbie will cruise merrily along at 2kw. Plus if the original breaks I'm stuck. With 2 at least I can get back during testing. What about efficiency of a non-straight chain vs overcoming an extra freewheel...does the gear ratio make a difference (I'll need at least 2.5:1)?

John

 

[Miles]

John,

The system of retro-direct you described, with 2 chains, was first used by Paul de Vivie, in 1899.

It has the advantage of allowing a different size of driver gear for each ratio, which would make it easier to get a wide ratio difference.

 

[John in CR]

John,

The system of retro-direct you described, with 2 chains, was first used by Paul de Vivie, in 1899.

It has the advantage of allowing a different size of driver gear for each ratio, which would make it easier to get a wide ratio difference.

Kudos to the guy who came up with the single chain version too. I thought the single chain R-D was old as well.

John

 

[Miles]

I thought the single chain R-D was old as well.

Yes.

Just about every permutation was tried around that time...

If you want a taste of the history:
http://www.users.globalnet.co.uk/~hadland/old_derail.htm#Introduction%20to%20change-speed

 

[HAL9000v2.0]

Most of the controllers have reverse jumper inside. All crystalyte and all kelly AFAIK.

 

[Miles]

http://www.bicicletasantigas.com.br/arquivos/portal/galeria/m10.htm