Help me with my first disability e-trike (and 1st ebike)

[vogelfrei80]

Hi, I need your help with my first ebike.
It will be a present to my brother-in-law at his next birthday. He has a disability and weight about 260 lbs. I already own a DIY trike:

I want need to help him starting from a stop, from a traffic light or anything else. I usually push him after a sudden stop to get him cross roads quickly, but I also push him when we find a little uphill road. It's important that he could go on riding and making movement, so I don't want to give him an e-trike that doesn't need his effort.

I'm a complete noob and looking for information on the web I thought:
1) I need a Mid-drive with no gears and any kind of trigger or display (he couldn't understand how to use them)
2) I need the engine work as soon as he moves the pedals
3) the mid-drive should work harder as he moves slower (and since he start moving) and totally stop working as he reaches 12 mph
4) I need a link for a guide on how build and assemble all the parts!
5) I need your help choosing what parts buy!
6) I cannot spend more than 500$ (could it be ok a 3000W cyclone kit?)

Thank you for all your help.

 

[Chalo]

My approach would be to get a smallish hub motor and hang it from a bracket under the rack, with a single 16t freewheel on the left side. Then run a chain from the freewheel down to a 28 to 36t sprocket mounted on the trike's axle. The speed of the motor will dictate your gear ratio, but a free speed of about 14mph should yield a practical top speed of about 12mph. Using a roughly 2:1 reduction will approximately double the torque at the wheel.

Put the battery on top of the rack. Use a controller with PAS, and don't install a throttle.

 

[flat tire]

Is this dude physically or mentally disabled? Sounds like the latter. If so, does he ride by himself or does he always require supervision?

I think pedal assist probably is the way to go. There's no off the shelf way I know of to give a boost just when starting out unless you replace the battery with a shitton of supercaps and make him regen after depleting them taking off or something.

 

[Rassy]

Some of the same questions as posted above, plus, where are you located?

Chalo's ideas would work good if you are fairly capable and can build the necessary brackets, etc. needed to mount the motor.

However, if you need something fairly easy to install a 36 volt Bafang crank drive at 500 or less Watts would be straight forward. The 3000W Cyclone you mentioned is way more power than needed for this application.

Your limit of $500 is a little low by the time you include a decent light weight battery and charger.

What trike is he riding now? The one you pictured does not appear to be in riding condition.

 

[vogelfrei80]

My approach would be to get a smallish hub motor and hang it from a bracket under the rack, with a single 16t freewheel on the left side. Then run a chain from the freewheel down to a 28 to 36t sprocket mounted on the trike's axle. The speed of the motor will dictate your gear ratio, but a free speed of about 14mph should yield a practical top speed of about 12mph. Using a roughly 2:1 reduction will approximately double the torque at the wheel.

Put the battery on top of the rack. Use a controller with PAS, and don't install a throttle.

ok, the bolded text are easy to understand.
the underlined part are a bit difficult for my English. I cannot understand the use of the freewheel. Do I have to use that to lower the motor intervention?

Is this dude physically or mentally disabled? Sounds like the latter. If so, does he ride by himself or does he always require supervision?

I think pedal assist probably is the way to go. There's no off the shelf way I know of to give a boost just when starting out unless you replace the battery with a shitton of supercaps and make him regen after depleting them taking off or something.

He's mentally disabled and he requies supervision. He's also very strong and fat
"shitton of supercaps" means?

Some of the same questions as posted above, plus, where are you located?

Chalo's ideas would work good if you are fairly capable and can build the necessary brackets, etc. needed to mount the motor.

However, if you need something fairly easy to install a 36 volt Bafang crank drive at 500 or less Watts would be straight forward. The 3000W Cyclone you mentioned is way more power than needed for this application.

Your limit of $500 is a little low by the time you include a decent light weight battery and charger.

What trike is he riding now? The one you pictured does not appear to be in riding condition.

I live in Italy.
he's now riding another trike which suffers from a sort of misaligned structure, so the rider needs to sit misaligned. The trike in the picture needs new colour, tires, brakes,saddle and lights, but its a present from an uncle and I tried it... runs quite smoothly and comfortably
Can you suggest me exact bafang cranck drive, a decent light battery and charger? What do you think about the idea of the freewheel, would it be compatible with the Bafang's?

 

[Rassy]

Can you suggest me exact bafang cranck drive, a decent light battery and charger?

I would look at EM3EV for the 36V 500W crank drive Bafang and compatible battery. Also Ping Battery. I've made multiple purchases from both and they both provide good products and good service, but you will see the prices and shipping run well over $500 USD.

What do you think about the idea of the freewheel, would it be compatible with the Bafang's?

Apples and oranges. The freewheel Chalo mentioned would be added to the motor he suggested so that when you coast or pedal with the motor turned off there is no drag from the motor, plus it acts as an adaptor that allows the motor to be connected to the chain. The Bafang kit includes built in freewheels, etc. that accomplish the same thing.

 

[Chalo]

Then run a chain from the freewheel down to a 28 to 36t sprocket mounted on the trike's axle. The speed of the motor will dictate your gear ratio, but a free speed of about 14mph should yield a practical top speed of about 12mph. Using a roughly 2:1 reduction will approximately double the torque at the wheel.

the underlined part are a bit difficult for my English. I cannot understand the use of the freewheel. Do I have to use that to lower the motor intervention?

I'm talking about using a rear hub motor, but running it backwards so the motor drives the freewheel instead of the freewheel turning the hub. Look up Stokemonkey by Todd Fahrner for a good example of what I'm talking about.

However, in your case I'm suggesting the motor driving the trike axle at a reduced speed, so that net torque approaches zero as the trike approaches 12mph/20kph. Because hub motors are almost all designed to run at 18 to 30mph or more, you need reduce the ratio to the wheel to reduce the speed.

By using a 16 tooth freewheel on the motor (a regular right side single speed freewheel but turned around to the left side) and running a chain to a larger sprocket that is mounted on the axle, you can reduce the wheel speed and increase its torque. That way, you get a quick takeoff but a low top speed. I was suggesting a size range of 28 to 36 teeth to reduce the hub motor's speed to a rate that would give a top speed of 12mph/20kph. That assumes an average hub motor which would give 20 to 25mph when laced into a bike wheel.

 

[vogelfrei80]

ok Chalo, I undestood.
What about a Tongsheng TSDZ2 with torque sensor? Will it be ok with a 16 tooth freewheel on the motor and a 36 on the axle? Will my brother in law make too much pedals' rotations to have a decent speed (15-20) mph on flat roads?

 

[Chalo]

The motor you mention is a mid drive. I doubt the gear would have to be as low as you suggest. Go to Sheldon Brown's gear calculator online and figure out what ratio gives 15mph at 100 pedal RPM (cadence), with the wheel diameter you have. That's the ratio you need.

 

[dogman dan]

Give him a 250w front hub motor kit. Not much power, with Pedal Assist, no throttle.

Get it in Europe, so it has the slower speed limiter on the controller. That way he won't outrun you. Could even be a 24v kit. Lead battery, so it's both cheap and he can't go that far.

Can't recommend a vendor, I'm in USA, and completely unfamiliar with EU kit vendors. When I pull up ebay, I don't get EU vendors.

You are going to need a welder to put some brakes on that thing.

 

[Drunkskunk]

The Tongsheng or the Bafang mid drives should work just fine. I would start with one of the 500 watt or larger units since he is heavy. it is easy to program them to provide less power, but it would be impossible to make a smaller unit provide more power.

As Chalo said, select the gears for a cadence of 100 at 15 mph. I would also suggest adding some form of brake to the rear axle.

 

[docnjoj]

Beware of Tongxin (Tongshend?) because if they are the same they have a very high failure rate, at least as of a few years ago. The roller gears are a great idea, but the execution is not well done.
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