the ideal and practial motor solution

[cadstarsucks]

It is hard enough to find room on a bike to put batteries to get all of the Ah I want, but to add a large outside case spinning motor just so I have a one to one ratio with the drive wheel doesn't seem to make much sense. I think hub motors are best put at the center of the wheel where they are designed to go.

Please don't pull Safe's chain drive leash or more graphs will poop out!

So where is the mime? You know, a mime is a terrible thing to waste.

[safe]

Torque Extremes

Not a true "chart" (see the lower chart) in that it's not spreadsheet driven, but the idea is there. At the lowest pedal rpms your torque swings will be the greatest, but as the rpms rise your ability to deliver torque drops until all your energy is spent trying to get your legs spinning in circles. This is why the peak power tends to be at lower rpms for untrained cyclists since the coordination to deliver real torque at high rpms is not there.

So you can see why this previous chart is valid also:



...and the reason for what's happening:

[Miles]

The problem with putting the motor and pedal power through derailleurs is that 3/32" chain and sprockets wear so quickly.

I don't agree with that.

I've been running a cheapo chain on my bike and pushing 1.36 horsepower (peak) and have gone 2,500 miles with it with no noticeable chain wear. The important thing about chain life is lubrication... if you neglect your chain then it will die an early death..........

Chains that are only 3/32" are still plenty strong and last a long time if you take good care of them.

As far as the chain goes, its gotta be stardard chain that fits through a regular bike derailer...we bought the highest performance SRAM chain but it didn't really last that long.

[numberonekiwi]

this has been done already here nice set up and I am sure could be fitted to nearly anything

[recumbent]

It is hard enough to find room on a bike to put batteries ... Please don't pull Safe's chain drive leash or more graphs will poop out!

This has been discussed before, the end result is chains can be problematic, add two of them, plus another freewheel, more noise and more potential problems.

Hub motors fit the goal most of us seek, we don't mind pedaling a little bit some times, it's a pedal bike after-all. Both systems work well, just depends if you want to tinker with dirty chains more, or tinker with them less

[safe]

Hub motors fit the goal most of us seek, we don't mind pedaling a little bit some times, it's a pedal bike after-all.

We all don't "seek" the same goal... (but "most" is probably accurate)

In my case my "goal" is a Road Racer bike that has certain odd charactoristics that other bikes don't have:

1. At top speed I DON'T pedal. (staying tight in a tuck makes so much less wind resistance that it equals all the pedal power you might create)

2. I need to be able to climb hills as well as hit my top speed, you just can't do that with a fixed gear. On my present bike I don't even bother with pedals. (though that will change with future versions)

3. When you are allowed only 750 watts (with just a little above) you get a net gain in power of 25% across the full spectrum of bike speeds. You get a 25% improvement in efficiency and a reduction of heat of 33% all because of the use of gears... that's hard to ignore and would make my bikes performance suffer if I went without it.

However... my bikes are all custom built, so for the "real world" most people will choose the hub motor because it takes no real effort to make work. Often one's "goal" is more about a compromise... because other options are simply too hard. (custom bike creation is very hard work)

[Geebee]

The problem with your "Bad" example is that it works great, as it gives more assist up uphill and on the flat it is better as your pedal speed rises it unloads the motor sving power for when it is needed.
I have had no problem with the setup on steep (40% +) off road but with a lower powered motor the only negative is that you need a tensioner in the drive side of the rear wheel as it will tend to move forward.
I have never broken a chain with a bb drive and I clocked up a lot of ks on one which peaked over a kw, as pointed out keep the chain lubed and wear plummets.
Tandems put huge peak loads on chains and they work fine.