Building electric Indian bicycle rickshaw

[thorjorbin]

Hi there!

I am looking for advice or ideas about how to create a converted electric Indian Bicycle rickshaw that runs on a 250 Watt or lower motor. I am working for a company considering launching an electric bicycle rickshaw race.

Ideally, we want a solution where we retro-fit a traditional Indian 3-wheeler bicycle rickshaw with a conversion kit (attached a picture of the bike we want to convert). I have attached a picture of what kind of bicycle rickshaw we're thinking of. The bicycle rickshaws needs to carry minimum 2 people excl. luggage and bike ( so approx. 180-210 kg total), ideally have a range of 50km per charge and a speed of maximum 25 km/h. The batteries should be rechargeable and changeable. It is quite important that the motor is below 250 watt, which we know is quite a challenge. The terrain is fairly flat, but small hills will occur, I am especially looking for advice on how to get around the challenge of having such a small motor provide a strong enough support without overheating

I reached out to GRIN Technologies/ebikes.ca, who said that their Bafang and Shengyi could provide the speed with an adjustable controller, but that they would overload fairly quickly with the load (and backed this up with their cool simulator, linked below). They suggested that I reach out to you geniuses, and tried to get your input!

Hope someone out there is able to help

Thor

 

[glennb]

In India and Bangladesh at least, normal speeds are 5-10kmph. At 25kmph the wind resistance becomes significant, and the rolling resistance is already plenty, so you simply can’t have that parachute as well, it’ll have to go.

Is it just the manufacturer 250w label that’s important? Or you want a reaistic 250w motor? I have a cargo bike with 5kg direct drive hub labelled 200w. That’s an extreme example, but pretty well every 250w labelled motor is mislabelled.

If you want a genuine 250w motor, that’s on the verge of cooking at sustained 250w, it’d be nonsense to modify it. Sure, you can use active cooling on a 250w nominal motor, but then it’s no longer a 250w motor. Same thing if you vent the motor, or modify it in any way to shed more heat, you no longer have a 250w motor, and might as well have saved yourself the trouble by buying a mislabelled larger motor.

 

[PaPaSteve]

A motor to consider :

Top 10 best and Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit world's Fastest electri

www.cyclone-tw.com

Aerodynamics is certainly a key aspect to increasing range with minimum power.
Pedaling 200 watts of continuous power can achieve 43 miles in a one hour time trial.

 

[amberwolf]

Unless you have some paperwork reason to use a motor that's either actually 250w or labelled 250w, then the motor wattage is irrelevant.

What matters is the controller being limited to whatever current is needed to provide 250w to the motor at the battery voltage you choose.

As long as it is correctly limited, then any motor capable of at least 250w, or more, can be used, and you won't exceed 250w power output.


But: 250w is probably not enough by itself to do what you want, not with that kind of trike; as Glennb notes you have a giant parachute on there that will add significant drag, and if you have any crosswinds or headwinds it will be even worse.

If it's not flat ground, and has any uphill slope at all, or poor road / path surfaces...it probably will perform very badly with passengers.


I guesstimated things such as CdA of 0.5 (it's probably a lot worse), and using a "custom" 250w (36v x 7A) controller, and the GMAC 10T (which could probably do the job all day at this power level) with a 36v battery, 500lbs for three people plus the bike, you get only about 190W at the motor itself, but it gets you up to as high as 26.8kph if you can get the CdA down to 0.5 and low rolling resistance, too.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

If you have a higher CdA like 0.75, you only get 20.4kph.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

If it's a lot heavier than expected, or bigger people, then you only get 17.8kph

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

Just giving it a 0.5% slope on the last sim and it can't even move (says 0.6kph, but I doubt that would really work).

At 500lbs on that slope you get 17.2kph (instead of 20.4).

Etc.

Make it a 2% slope, and even at the 500lbs it won't move, even if it's only 0.5CdA (because at nearly zero speeds the CdA doesn't matter).



If you set the motor up as a middrive that you can shift gears for like a pedal drivetrain, and the gears are optimized for the speed range you intend, and is geared low enough at the lowest end, it would perform better, possibly much better, though you still will have problems with any slopes with that kind of weight, especially if you need to go faster than a slow walk (if that). The simulator can be setup to emulate this, too.

 

[PaPaSteve]

There are two electric, pedal / electric racing events I've participated in, they both limited battery energy density and left the motor and controller options open.
1) Home | AMERICA | The Official Electrathon America Site
Electric power only, This series originated in Australia and was based on how far can a small vehicle go on one 12 volt Optima car battery.
The American version has changed the battery specs a few times but basically uses the same idea of using battery density as the equalizer.
2) World Solar Ralley had a couple pedal / electric classes that were were limited to 20AH of sealed lead acid batteries.

For both events aerodynamics was the winning factor.

 

[thorjorbin]

Thanks for the great input! I know its quite a challenge to get this design to work with the 250W limitation. As I probably should have shared before the 250Watt limitation is a legal one. Due to India's certification requirements for vehicles, I need to make a design with maximum a 250 Watt motor - if not I need to obtain vehicle approval as if I was building a motorbike, or possibly even a car. And it's costly and takes ages. So thats the reason for this hurdle! Therefore, its also a question of having the correct manufacturers label - so potentially having a motor thats in fact more powerful its actually okay, as long as it on paper is 250 Watt.

In terms of aerodynamics, it could be discussed to skip the parachute. Thats a possibility.

For speed its not that it needs to go 25 km/h. Again its just a legal requirement that it can't go more unsupported, but I guess thats not going to be a problem with this load. So anything above 10 km/h would be okay, ideally it should be fairly doable to reach 17-20 if pedalling fairly hard. so @amberwolf, lowering the cDA is a possibility and reaching high speeds is not paramount.

 

[thorjorbin]

In India and Bangladesh at least, normal speeds are 5-10kmph. At 25kmph the wind resistance becomes significant, and the rolling resistance is already plenty, so you simply can’t have that parachute as well, it’ll have to go.

Is it just the manufacturer 250w label that’s important? Or you want a reaistic 250w motor? I have a cargo bike with 5kg direct drive hub labelled 200w. That’s an extreme example, but pretty well every 250w labelled motor is mislabelled.

If you want a genuine 250w motor, that’s on the verge of cooking at sustained 250w, it’d be nonsense to modify it. Sure, you can use active cooling on a 250w nominal motor, but then it’s no longer a 250w motor. Same thing if you vent the motor, or modify it in any way to shed more heat, you no longer have a 250w motor, and might as well have saved yourself the trouble by buying a mislabelled larger motor.

Just the label is important - its a legal requirement to have it maximum 250 Watt so a mislabelled motor could be a possibility. Anything you would recommend?

 

[thorjorbin]

Unless you have some paperwork reason to use a motor that's either actually 250w or labelled 250w, then the motor wattage is irrelevant.

What matters is the controller being limited to whatever current is needed to provide 250w to the motor at the battery voltage you choose.

As long as it is correctly limited, then any motor capable of at least 250w, or more, can be used, and you won't exceed 250w power output.


But: 250w is probably not enough by itself to do what you want, not with that kind of trike; as Glennb notes you have a giant parachute on there that will add significant drag, and if you have any crosswinds or headwinds it will be even worse.

If it's not flat ground, and has any uphill slope at all, or poor road / path surfaces...it probably will perform very badly with passengers.


I guesstimated things such as CdA of 0.5 (it's probably a lot worse), and using a "custom" 250w (36v x 7A) controller, and the GMAC 10T (which could probably do the job all day at this power level) with a 36v battery, 500lbs for three people plus the bike, you get only about 190W at the motor itself, but it gets you up to as high as 26.8kph if you can get the CdA down to 0.5 and low rolling resistance, too.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

If you have a higher CdA like 0.75, you only get 20.4kph.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

If it's a lot heavier than expected, or bigger people, then you only get 17.8kph

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

Just giving it a 0.5% slope on the last sim and it can't even move (says 0.6kph, but I doubt that would really work).

At 500lbs on that slope you get 17.2kph (instead of 20.4).

Etc.

Make it a 2% slope, and even at the 500lbs it won't move, even if it's only 0.5CdA (because at nearly zero speeds the CdA doesn't matter).



If you set the motor up as a middrive that you can shift gears for like a pedal drivetrain, and the gears are optimized for the speed range you intend, and is geared low enough at the lowest end, it would perform better, possibly much better, though you still will have problems with any slopes with that kind of weight, especially if you need to go faster than a slow walk (if that). The simulator can be setup to emulate this, too.

Thanks for the great input. So yeah, lowering CdA will be important and we can shed the parachute The slopes are generally a problem that needs to be solved.

The plan was indeed to have a geared system with very low gearing at the end. Do you think with a slightly lower CdA at maybe 0.7, a mislabelled motor and a geared system it could be possible?

 

[glennb]

I’m confident it’s doable, from working backwards from my experiences with these vehicles under human power. You need to translate everything to torque, but I’ll speak in loose wattages. I’d say 1200w peak will get you moving from stall, 200w would move you at a slow crawl, and 400w should achieve >10km//h. I can’t imagine 25km/h.

In the sub-continent the motors are typically <50kg of bone, sinew, and slow twitch muscle fibre. Mostly bone and sinew. They’re incredibly strong and scrawny, and would surely be averaging >250w over short journeys.

20km/h is achieved on long straight stretches with a single passenger, but never with a full load. Even then, it’s rare and takes minutes to build up that speed, so forget about anything resembling acceleration.

Furthermore, the rickshaws are always overgeared - I’m guessing because they prefer low cadence riding out of the saddle, because it’s not because they ever go fast - and with a 200kg payload the riders’ maximum effort is inevitably insufficient to budge from a stall. One passenger has to temporarily alight until the vehicle’s starting to roll, then hop back in.

The operators are ridiculously proud, making it nearly impossible to convince them to jump in the back and let you take control, but on the few occasions I managed it, I could get the vehicles underway and up to speed with two passengers, total >300kg, by giving it everything, even up slight inclines. So, that’s two points of reference. At that time I had huge legs and would’ve weighed nearly 85kg, and at a guess would’ve sustained 500w over these journeys and could hold 15km/h. A motor would’ve been nice though

 

[Chalo]

There's a difference between a motor that peaks at 250W under a single ideal condition, and one that delivers a steady 250W over a wide range of RPM and battery voltage. And there's another difference between either of those and a motor described as 250W that sorta-kinda averages 250W in foreseeable use, but peaks much higher. The latter is, I suspect, reality for a lot of nominally 250W motor systems. Either the steady-250W or the actually-more-than-250W kind would be applicable to the project at hand.

I would really like to see more systems that adhere to their ratings, but do so across the widest possible range of speeds and conditions. I think it would be both user-friendly and traffic-friendly to have bikes that deliver the same goods when grinding up a hill or pulling away from a stop as they do while flying down a flat smooth road. It would require a little more homework by the manufacturer, but hey, they should offer at least something that you can't easily DIY cheaper and better.

 

[PaPaSteve]

Most retrofit 250 watt motors for bicycles are hub style.
A motor that powers the chain would be an advantage.
Bosch and Shimano make nice 250 watt motors however they are not meant for a retrofit.
The cyclone motor mentioned in post #3 in this thread does drive the chain and is retrofit.

Is the rickshaw a single speed ?
Installing a 7 speed internal gear hub was a significant improvement for our rickshaw (pedicab).
It was geared extra low for start up and has just enough high gear for the weight it carries.
Nice thing about this setup is the ability to shift when stopped.
When used with a motor drive a momentary cut out switch is required or it won't shift.
Link to switch thingy.
Note the sprocket bolted to the left side spoke flange, this something I made and have drawings for Nexus 7 and 8 speed.

 

[thorjorbin]

Most retrofit 250 watt motors for bicycles are hub style.
A motor that powers the chain would be an advantage.
Bosch and Shimano make nice 250 watt motors however they are not meant for a retrofit.
The cyclone motor mentioned in post #3 in this thread does drive the chain and is retrofit.

Is the rickshaw a single speed ?
Installing a 7 speed internal gear hub was a significant improvement for our rickshaw (pedicab).
It was geared extra low for start up and has just enough high gear for the weight it carries.
Nice thing about this setup is the ability to shift when stopped.
When used with a motor drive a momentary cut out switch is required or it won't shift.
Link to switch thingy.
Note the sprocket bolted to the left side spoke flange, this something I made and have drawings for Nexus 7 and 8 speed.


View attachment 347310

Thanks for your reply! So you actually build one, would it be possible to see a full picture?

How big a load and what range can yours do? We were thinking to do a geared version to help with ascents and so.

 

[PaPaSteve]

Thanks for your reply! So you actually build one, would it be possible to see a full picture?

How big a load and what range can yours do? We were thinking to do a geared version to help with ascents and so.

Our rickshaw switched between a flatbed for hauling loads and people mover.
It was used often but never had a motor attached.
I've pedaled it up and down the hills in San Fransisco doing the Critical Mass rides.