Mid Drive to a Single Speed Hub? Bad idea?

[SimiGuy]

I'm building a cargo bike and just ordered the Cyclone 3000W mid drive kit from Luna Cycle. Originally I wanted to mate this with a Nuvinci hub but found out that the new Nuvincis can't handle the torque and the old ones are hard to find (and I can't afford Rohloffs).

I hate the idea of a derailleur on the rear end so I was thinking of just using a single speed freewheeling hub (BMX style) with the Cyclone. The idea is that the bike would be geared pretty high which would normally make it a pain to get going or to climb hills. But since I will now have this motor (with potentially 10 times the power of a human) to help out then I would just use the motor to help me get going & accelerate from a dead stop and to help up the hills. Was going to pick a gearing that gives me a pretty fast but bearable cadence at around 20 mph.

Has anyone every experienced something like this and / or think it is a good or bad idea? Could this set up be un-ergonomic or feel weird?

 

[broke]

i have the same motor working with rohloff. I would not gear it like that. It would be better to gear it for low speed.
1 the kit will flex so bad chains will pop off.
2 how are you going to get going from stops.( think stop sign on a hill)
3 under load like that with no throttle ramping. ( stop controller ) things will brake in no time
just my 3 cents.

 

[Chalo]

My recent experience with the Luna cargo bike leads me to point out that the chainline is freaky bad. That's no good if you're using a gearhub with fixed freaky-bad chainline, but it's okay if you're using a derailleur system that runs in the higher gears most of the time (where chainline is better).

My suggestion is to use a single speed MTB hub, spaced only as much as necessary to accommodate a 5-speed freewheel, and put a rear derailleur on one of these:

Limit the derailleur to only as many gears as it can use without scrubbing the chain on the tire (probably just the outer three gears of five).

14-17-20 rear gearing isn't much range, but it can allow you to make much better use of your motor power than you could with only one gear. For best results, set it up so the 14t is the gear to use when the battery is healthy and range isn't an immediate concern. That gives you the best (still not that good) chainline you can have with that frame as built.

 

[Deafcat]

Consider trying the Sturmey 5-speed IGH hub, with integrated 90mm drum brake. it's apparently rated for "heavy duty" and improved over their previous stuff. I think it would work great for this kinda thing if it's reliable! Not too pricy either.

what frame are you building with?

 

[Chalo]

Hmm, I saw "cargo bike" and "Luna" and made my own conclusion. But you didn't say you were using a Luna cargo bike frame, so now I'm curious.

 

[Leebolectric]

Many of the MTB single speed hubs are actually short cassette hubs...they hold 4-6 cogs.
Tighten the hi/lo limit screws and use the standard 7,8,9,10 speed cassettes,shifters,deraileurs...just take out cogs you don't want.
Hope,Hadley,And King are the first to come to mind, but others are out there.
http://www.balleracing.com/hadley-single-speed-135mm-x-10mm-ti-bolt-on-rear-hubs/hadley-rear-clear-ss-single-speed-10mm-ti-hub
prime beef there^

 

[SimiGuy]

Thanks for all the suggestions and links. I'm building a custom frame and can mount the Cyclone in any why I need to keep it nice and rigid and aligned correctly - so I'm hoping to avoid the drive line issues. Below are couple of CAD shots of what I'm currently building.

So with my high gearing, I was hoping to use the motor to get me going from stops. But as you said "broke", you didn't think that was a good idea because too much force / torque at that initial moment and things could break - hmmm... Maybe I will have to investigate the 5 speed Sturmey Archer...

 

[WoodlandHills]

I ran a BBSHD on my SS fat bike with no real troubles on the street, but the sprocket selection is limited. You can take a steel freehub apart and use a single cog, but when you go too large you run the risk of bending the gear. The biggest SS sprocket available is 22t and off-road that just too small. My Bikes Direct has a freehub with a spacer to locate the cog as opposed to a SS freewheel.

My solution is to have a Shimano Nexus3 laced into my hub and I will be picking it up later today, if all goes well I will test it this weekend. The 3-speed hub is supposed to be stronger than the 8-speeds, so we shall see. Mainly I want to have a decent granny gear for slow climbs on tight tracks.