[cargo trike] Swapping 250W mid-drive motor with 750/1000W rear motor?

Hello,

Someone I know rides a Triobike Boxter cargo trike.

It was fine while she used it in a flat area, but the 250W, 90Nm Brose Drive S mid-drive motor is showing its limits in a much hillier area, and the kids are only getting heavier.

It uses an Enviolo Heavy Duty (380%), 135mm OLD hub with a Gates belt drive.

Replacing the original 50T + 24T cogs with a 46T + 28T did help, and the 46T will soon be replaced with a 39T, at the expense of riding on the flat.

Since the frame is meant for that mid-drive motor and it's just not possible to install eg. a Bafang BBS02/BBSHD, I was wondering about replacing the rear wheel with an (affordable, as money's tight) 750/1000W motor + derailleur, and just disconnect the mid-drive for when she'll sell that bike or move to a flatter area again.

Provided there are 135mm OLD 750/1000W rear hubs available, do you recommend direct drive or reducted? The former has the advantage of helping when going downhill.

Also, the frame might not accommodate a derailleur hanger. In that case, and considering the powerful rear motor… would using that bike with a single cog do?

Thank you.

I doubt the 1000w system, which could be almost impossible to DIY with a belt drive, would be better than the mid for hills. If it were possible to incorporate a rear hub, I would use in conjunction with the mid.

How about a front hub motor in one of the front wheels. It would add power.

She won't mind ditching the belt drive for a chain if that means more power to climb hills.

A rear motor seems to make more sense than one in the front wheels.

I highly recommend taking a look at the ebikes.ca motor simulator, and use the data from the actual terrain/etc along with actual system/trike/rider/etc weights, riding conditions, etc, to determine actual power / torque / etc requirements to do what hte rider wants. Then you can use the results to figure out what actual system will do that for them.


A middrive that can go thru the bike's gearing, as long as that gearing is suitable for the situation, is almost certainly going to be more optimal than any hubmotor in a wheel.

For the same power level, it'll be tough to find any hubmotor system that could do it at all, most likely.

It is likely to take a lot more power to do it with a hubmotor in a wheel, and so a much bigger and more-capable battery, and a more-capable controller as well as the bigger motor. Probably not a cheap conversion.

If you have to go with a hubmotor in a wheel, I would take a look at ebikes.ca GMAC rear motor, as that is a geared hubmotor but it has (or can have) no clutch / freewheeling internally, so it can also be used for regen.

Disadvantage to any geared hubmotor is that there are two airgap layers so it builds heat up faster and gets rid of it slower than a DD hub, and it is harder to do cooling methods of various kinds (and things like ferrofluid / statorade don't work as intended because of the second airgap).

Advantage is that gh's are usually more startup torque for the same size controller/battery/wheelsize/etc.

The only thing I didn't really like about my GMAC was the noise, but that would be true of nearly every gh.



Front hubmotors on a trike built like that would be a challenge, but it is possible, using ebikes.ca All Axle Motor and one of their adapter kits made for that type of trike, or if those don't fit a custom-made one. There are some threads here on ES showing how they were used on various tadpole trikes. (and you can use just one on one side, it will torque-steer/brake but you can learn to control that easily enough).

Going single speed in a super hilly situation would necessitate a motor with a rating of 2000w or higher if you're climbing significant hills... since the human power can't be geared to help the motor.
This would require a bigger battery, new controller, etc..

There exist side shaft motors from the front but i'm not sure if you need a pair of them or if you can get away with just one.
Grin All-Axle Hub, Single Side Build

This bike is quite difficult to improve on due to it's proprietary nature :/

FWIW, you can still install other middrives, even if they can't go into the frame's BB, if you can mechanically create attachment points for them.

Some that normally go on the BB would require engineering a solution to drive their inputs from your pedals, or bypass the mechanics of that and direclty input the necessary sensor input to make them work.

Hubmotors can also be made into middrives (there are a number of examples around the forums) to still use your gearing, and they could even be setup to work with your existing drive system, though they'd need their own controller and battery.

Shohreh said:

Hello,

Someone I know rides a Triobike Boxter cargo trike.

It was fine while she used it in a flat area, but the 250W, 90Nm Brose Drive S mid-drive motor is showing its limits in a much hillier area, and the kids are only getting heavier.

It uses an Enviolo Heavy Duty (380%), 135mm OLD hub with a Gates belt drive.

Replacing the original 50T + 24T cogs with a 46T + 28T did help, and the 46T will soon be replaced with a 39T, at the expense of riding on the flat.

Since the frame is meant for that mid-drive motor and it's just not possible to install eg. a Bafang BBS02/BBSHD, I was wondering about replacing the rear wheel with an (affordable, as money's tight) 750/1000W motor + derailleur, and just disconnect the mid-drive for when she'll sell that bike or move to a flatter area again.

Provided there are 135mm OLD 750/1000W rear hubs available, do you recommend direct drive or reducted? The former has the advantage of helping when going downhill.

Also, the frame might not accommodate a derailleur hanger. In that case, and considering the powerful rear motor… would using that bike with a single cog do?

Thank you.

Click to expand...

As much as I like hub motors, I agree with the other respondents that a hub motor will not solve your problem, at least not cheaply. A hub motor with the power to do what you need would require a huge controller and battery, and if you factor in the cost to convert to a derailleur and chain, you are looking at a very expensive fix, that probably wouldn't help much.

As this is a trike, the front motor option is not ideal as you would need two motors to balance out the pull. I would not recommend just one front hub motor in this situation as it would make the steering VERY unpredictable while under power.

I recommend looking for ways to get more power out of the existing motor and proceeding with the gearing swap.

Thanks everyone for the great input. So rear hub is out.

It looks like the frame is too specific for that motor to take a BBS02/BBSHD :-/

And the few LBS around certainly don't have the expertise to even build a bespoke adapter. Only one even accepted replacing the original sprockets to get a lower gearing.

I'll report back after she swapped the 46T for a 39T.

get the kids some harnesses and play 'chariots' up hills

1.500 or 2.000 Watt motor as your kids are not going to grow smaller but they're going to grow heavier and they probably want to carry more on the cargo bike.