Tuesday, October 18, 2016

Cycle Tracter

the secret to a cycle tractor is the gear reduction

This is a perfect example of how to NOT build your bike 
into a cargo bike. If they had used a motor with a high 
contrast reduction ratio it would be able to climb hills 
with massive amounts of weight at a legal wattage.
 But most builders insist on using fast gears and 
electronics to limit the speed. Unfortunately that 
can be bypassed to make it a deadly motorcycle. 
40 mph is way too fast for a machine like this no mater 
where you ride it. And the wattage their motor uses is only
 appropriate for an off-road bike. This is NOT a street 
cargo-bike. It would be perfect to go camping in the mountains. 

Low Gear= High Contrast Reduction Ratio.

You ever wonder why e-bikes burn out so often? It is because they are built as cheaply as possible and because people want to use them much harder that they are built for. So why can't they build them right for heavy duty use?

People are so brainwashed by the bicycle industry that they think hub motors and kits of any well known motor-system are the things to use, even though hub motors are the least effecient for hill climbing and stop-n-go city driving. There are good reasons to build a bike with a non-hub direct rear drive. Mostly to keep from turning your bicycle into an illegal motorcycle with inadequate brakes. And still have enough power to climb the nasty hills that make my legs scream for help.

The controller type and setup have a significant effect on performance, not just the motor and gear ratio. Kelly controllers
have constant torque mode capabilities, in other words they have the capability to prevent amp multiplication at low RPMs that increases torque as the motor gets dragged down by increased load (at the same throttle setting). This prevents wasted energy at low RPMs where the motor is most inefficient and overheating abuses of the motor.

A 3000rpm motor will take a two or three stage reduction adding up to 18:1 to get the 26” wheel down to about 13mph a single stage reduction would take a sprocket larger than the drive wheel.

It would be easier to use a Lightningrod's kit that operates at about 90% efficiency, with 2 belt reductions before the third chain reduction to the drive wheel.

Or use a hub motor with a heat sensor, that drives at about 1500rpm or less, at the wattage listed on the label.

Gear reduction is the key to heavy hill climbing. A 9:1 ratio would be good for a 26” tire if the motor runs at about 1500rpm. That would be 16 tooth sprockets on the motor and 144 on the drive wheel. Or 18 on the motor and 162 on the wheel. Never use sprockets smaller than 12T, they will create excessive wear of the chain.

pedal assisted power drive

The crank should drive the motor, if the motor drives the crank your top speed can be much faster than anything safe.

If you can find a motorcycle sprocket adapter that will fit the free-hub body it would be easy to use two chain drives on the cassette side.

  • Kelly controller (option of torque control throttle standard):
  • Sprocket adapter (may need a longer axle or shorter hub to fit)
  • #35 chain
  • Large motorcycle sprocket (to fit the chain)
  • Motor:
  • Throttle:
  • Battery (the most expensive part)
  • Cycle-Analyst power meter
You could use regenerative braking in the rear for your in-place of a break, if you have a good break in the front.

veloci front hub w/ two disc mounts

sprocket bolted on front hub used on rear

A #35 chain to the left hand side of the drive wheel is better than a BMX chain. The hard part is figuring out how to mount a large sprocket on the hub and still keep your disc brake.

I think it would be easier to use a belt drive with a large rim pulley on the drive wheel than any kind of drive chain, unless it has a two stage reduction. I could not find a sprocket large enough for a single reduction. But a 12inch child's bike rim makes a good enough pulley for a belt. Then a 1.5” belt pulley on the motor would be close to an 8:1 ratio.

It would be very easy to add sprockets to the right side if you could find an adapter for a light motorcycle sprocket for #35 chain to fit onto a free-hub body behind a 6 or 7speed cassette. Then a ratcheting one-way bearing on the motor, so you don't have to crank the motor when it is off.

And thinking about a greasy chain splashing road crud on a disc rotor, it would be best to use only a belt drive on the left side.


Regenerative braking:

Direct drive hub-motors even just for bicycle use are not a very good option for true cargo hauling ability at least in my experience. For a cargo hauling a manual transmission with manual clutch that allows aggressive downshifting regen braking (and also downshifting for getting those big loads moving or dragging them up hills) is a very good idea. Why do you think the big 18+ wheel tractor trailer rigs still use manual clutch transmissions? In-fact due to the greater downshifting regen braking ability of electric motors compared to IC compression braking the argument for this kind of drive system is even stronger for heavy cargo hauling.

Setting a controller for climbing steep hills with cargo:

Best to probably take a Kelly controller and set the output motor phase end amp limits to the exact same as the battery input side amp limit. That will give you nearly constant stable torque, if that's too low to do the controlled front wheel pop up you desire on take-off then slowly up the output motor phase end amps limit while leaving the battery input side amp limit the same which in each step will increase the bottom end torque slightly and just keep upping it in increments a little at a time until you get the level of bottom end torque that gives you what you want.

Choosing a battery

Try to carry enough battery to keep your discharge rate under 2c.
For 10 amp hour size, that would be a 20 amp controller and about 700 watts.

To keep your self from being ripped off when choosing a battery please read this article!

Lead acid batterys are now costing about the same as lithium-ion per watt-hour and life expectancy. I hope that lead acid will eventually cost much more than the light weight cells; even if they do need to go to the moon to get the lithium materials.

Belt or Sprocket Adapters ???

Fixed Gear Drives

BIG BLOCK alternative Motor (for a larger motor)

NOTE: The motor wires are color for color on the Lyen controller (post 12 on page 2 of this thread: https://endless-sphere.com/forums/viewtopic.php?f=28&t=59122&start=25)


Best thing to do is to use a large sprocket like this one and just bolt it onto a large sprocket from a used cassette, or possibly two. then use a smaller cassete for the leg powered chain. 

sprocket calculator


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