Test

[Miles]

You can certainly use bike stuff. The smaller pitch chains allow you to get a greater reduction ratio, though. As Jeremy said, the faster you can spin the motor, the better.

 

[mk1]

You can certainly use bike stuff. The smaller pitch chains allow you to get a greater reduction ratio, though. As Jeremy said, the faster you can spin the motor, the better.

Yes it would be useful to be able to use the faster motor. Something else to think about!

Martin

 

[Jeremy]

I can understand the gearing problem, but it's well worth looking at trying to run the motor fast in a drive system like this.

If you take your first choice, the 4011, running at 24V, with peak rpm of about 120, then even assuming that you have a 35A controller and high capacity batteries you're only going to get a maximum of about 110 watts from the motor. This really isn't enough to make an appreciable difference to your bike, in my view.

If your drive system can tolerate 260rpm at the motor, then a 408 running at 36V will give you around 450 watts peak, pretty much the same as most "legal" ebikes.

If you really want to run a non-gear reduction motor at 24V, then try a 405 with a 35A controller and high capacity battery pack. This will run at about 270 rpm max with a peak power of about 400 watts, which is still OK.

Using a geared hub motor, like the BMC or eZee, will make a big difference to your gearing arrangements and may solve the big/small sprocket problem. As an example, an eZee run at 24V will give you a max rpm of around 160 and a peak power of about 470 watts.

Jeremy

 

[kraeuterbutter]

hmm..
lets say 450Watt Crystalite direct drive, mounted in the wheel...
on a steep hill or a heavy bike or trailer or low speed
- in this situations it will be way of this 450Watt

so: when you wana use such a motor through the bikes gears and not direct drive..
maybe 450Watt are not needed anyway...
i mean: if the hill is realy steep, you can use a very low gear..
80rpm on the pedals, 300Watt from the motor --> its maybe more than a double as strong motor as direct drive would bring to the road in such condition anyway..

 

[flecc]

maybe 450Watt are not needed anyway...
i mean: if the hill is realy steep, you can use a very low gear..
80rpm on the pedals, 300Watt from the motor --> its maybe more than a double as strong motor as direct drive would bring to the road in such condition anyway..

True. In fact the Panasonic unit's 390 watt motor rarely operates at over 250 watts with average riders, lower gears enabling them to climb 20% quite easily at about 200 watts.

I think cycle transmission could suffer with a combination of 450 watts plus the rider's input.
.

 

[kraeuterbutter]

isn´t it possible to upgrade the transmission ?

i mean: there are motorbikes with chains and 200hp+
so: chaintechnologie is able to handle great powers..

of course a motorcycle-chain would be a little TOO heavy and big

but: there are tandems.. maybe they use stronger equidment ?
some hub-gears are allowed to be used in tandems.. maybe this can be used ?

 

[flecc]

The bike Martin is using has a derailleur, so stronger chains aren't an option in the final drive.

The only heavy duty rated hub gear is the SRAM P5 Cargo, and in fact it's just a standard P5 with a slightly higher low gear to allow just that to be uprated.

Over 3 years I destroyed one of those with load towing on a Panasonic low powered motor, so with double motor power and a younger rider it probably wouldn't last long.
.

 

[mk1]

I can understand the gearing problem, but it's well worth looking at trying to run the motor fast in a drive system like this.

If you take your first choice, the 4011, running at 24V, with peak rpm of about 120, then even assuming that you have a 35A controller and high capacity batteries you're only going to get a maximum of about 110 watts from the motor. This really isn't enough to make an appreciable difference to your bike, in my view.

If your drive system can tolerate 260rpm at the motor, then a 408 running at 36V will give you around 450 watts peak, pretty much the same as most "legal" ebikes.

If you really want to run a non-gear reduction motor at 24V, then try a 405 with a 35A controller and high capacity battery pack. This will run at about 270 rpm max with a peak power of about 400 watts, which is still OK.

Using a geared hub motor, like the BMC or eZee, will make a big difference to your gearing arrangements and may solve the big/small sprocket problem. As an example, an eZee run at 24V will give you a max rpm of around 160 and a peak power of about 470 watts.

Jeremy

You are quite right Jeremy, now that I have had a proper look at the hub motor sim, my first choice is clearly pretty ridiculous!.
I am still worried about putting too much power through the transmission though.
I can put a reasonable amount of power in myself on occasion, so I reckon a max of 450 watts from the motor as well would be the limit.

Martin

 

[Miles]

The way to get more power through the transmission is to use smaller wheels

Here is another work bike that would be great for conversion:
Mundo Utility Bikes: affordable bikes to carry cargo and to transport stuff by bike for sustainable transportation

 

[mk1]

It's a bit late now Miles .
To be fair I did look at the Yuba but the spec is not quite as good as the Kona.

Martin

 

[flecc]

One of the Mundo model claims:

"The Mundo 5-speed (special order ONLY!) uses an internal hub, reinforced for cargo hauling, that enables the rider to shift on the fly whether pedaling, cruising or idling. Also suited for heavier loads."

Totally wrong. It's a P5 Cargo, and SRAM hubs are notoriously slow changing, will refuse to change with pedals turning and that must never be attempted on that design. Just as well it's special order only with that wrong advice.
.

 

[Jeremy]

From what I've researched, peak rider power at the pedals can be around 400 to 500 watts, although the average power will be much lower, perhaps less than 100 watts. Lance Armstrong was reputed to be able to deliver an average power of about 400 watts for an hour at the pedals (the peak power would have been very much greater), so clearly a bike transmission is able to handle this sort of power.

The real issue is the torque capability of the drive system, rather than the power. It may be that the transmission will comfortably handle 400 watts at a cadence of 120, but would only take half this power at a cadence of 60.

Generally speaking, it is much kinder to the transmission to run it at a high speed, as this reduces the forces in the chain, and, more importantly, the sprocket bearing faces, for a given power delivery.

There's no getting away from the basic facts about the power needed to travel at a given speed against a given resistance, either from drag or from an incline. Just lowering the gear ratio for a very low power bike doesn't magically allow you to travel up hills at the same speed as a bike with more power available.

A quick look at the bike power calculator here: Bicycle Speed And Power Calculator will show just how much power is needed for a given bike under a range of conditions. The laws of physics still apply, even with a low geared, low power motor!

Jeremy

 

[flecc]

Of course the lower power will mean lower speed hill climbing, there's no argument on that, only that lower powers make transmissions last longer. The record of hub gears on both tandems and chain drive e-bikes has been a bit poor, and I think a derailleur is a better bet as Martin intends with the Kona.
.

 

[mk1]

I am not sure how accurate that power and speed calculator is, but it's good fun to play with.
Now I know how much power I need to get up a 20% hill if I weigh 400 pounds

Martin

 

[Miles]

See also: http://www.pedelecs.co.uk/forum/electric-bicycles/50-spreadsheet-calculator.html

Use Rev.3

 

[flecc]

I am not sure how accurate that power and speed calculator is, but it's good fun to play with.
Now I know how much power I need to get up a 20% hill if I weigh 400 pounds

Martin

Plus a 30 kilo e-bike and at 5 mph, 930 watts, and I didn't need a calculator or program.
.

 

[mk1]

bike + rider weight (kg) x 9.8 x elevation gain (meters) / time (seconds) = power (watts). Add 10% for rolling and air resistance.

 

[flecc]

Ahem! 9.81
,

 

[Jeremy]

9.80665 if we're intent on being pedantic (at least as far as five decimal places)............

Jeremy

PS: Personally I always reckon it's good enough to remember that a Newton is roughly the downward force that a big apple exerts on one's hand when standing on the Earth's surface. Easy to remember and an approximation that is good enough for rough calculation purposes.

 

[flecc]

This one Jeremy?
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