Mid-drive conversation kit for pulling heavy cargo bike

[Simonh82]

First time poster on here, looking for some advice about mid drive conversation kits.

I want to convert an old hybrid bike to an ebike. I really want to cut down or eliminate short car journeys that I make regularly. These are generally to the big supermarket and to a localish park which is well enclosed and where our daft whippet who loves to run away can safely be let off the lead.

Having been inspired by some YouTube videos I'm in the process of building a large foldable cargo trailer that I hope will hold a full load of shopping or a dog (carefully and fully secured) and child. To add to the fun my local supermarket has a largish hill with about 40m of climb and about 30m of decent between the shop and my house. I think the trailer plus shopping could be around 80kg on top of my 75kg and whatever the bike weighs.

I would like some advice about what motor/kit to get to allow me to get me and my shopping over the hill without killing me. I cycle to work regularly so have a base level of fitness but it's a flat commute and I don't think I'm ever going to win a polka dot jersey. Basically I need a good bit of assistance to get me home with a heavy trailer.

I've been thinking about a 500W Bafang mid-drive kit. I am aware that they aren't road legal in the UK but I would only use it at 500W for the hill and would set it back to 250W at other times. I know this may not cut it with the police if challenged but I'm hoping that a middle aged rider, not going too fast and riding sensibly would hopefully not attract too much attention. I'm also going to be upgrading the brakes to make sure I have enough stopping power as I don't want to be dangerous to other road users.

Does this sound like a reasonable choice of motor for my purpose? There are 750W and 1000W versions too but I don't want more power than necessary. I think the 750W version is actually the same motor as the 500W version but presumably it has a different firmware setting. I'm assuming that it's possible to put the kit back to 250W output after it has been derestricted. Is that the case?

Thanks for any advice.

 

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BAFANG BBSHD 1000W 48V -120MM FATBIKE GRADE A MOTOR KIT – Red Dragon Ebikes

more voltage more amps more power but just need to make sure the batt and controller can handle it a bbshd can do 30a at 48 or 52v

 

[matthewslack]

A 250W legal kit will do what you need. Every illegal bike is bad for everyone, and if you do get caught, it is your car licence that gets the points.

250W is not the maximum power output. Common sense might say it should be, and surely that's what the law was meant to mean, but it is not so. As long as your motor has been 'rated' by the manufacturer as 250W according to EN15194, it is legal.

Straightforward choices are Bafang BBS01 and Tongsheng TSDZ2B from various suppliers or TSDZ8 supplied as 250W by Woosh.

All mid-drives get up any hill you like because you choose the gear! If at first you don't succeed, install a smaller chainring or a cassette with a bigger lowest cog.

 

[soundwave]

burgerking needs some of those

 

[saneagle]

First time poster on here, looking for some advice about mid drive conversation kits.

I want to convert an old hybrid bike to an ebike. I really want to cut down or eliminate short car journeys that I make regularly. These are generally to the big supermarket and to a localish park which is well enclosed and where our daft whippet who loves to run away can safely be let off the lead.

Having been inspired by some YouTube videos I'm in the process of building a large foldable cargo trailer that I hope will hold a full load of shopping or a dog (carefully and fully secured) and child. To add to the fun my local supermarket has a largish hill with about 40m of climb and about 30m of decent between the shop and my house. I think the trailer plus shopping could be around 80kg on top of my 75kg and whatever the bike weighs.

I would like some advice about what motor/kit to get to allow me to get me and my shopping over the hill without killing me. I cycle to work regularly so have a base level of fitness but it's a flat commute and I don't think I'm ever going to win a polka dot jersey. Basically I need a good bit of assistance to get me home with a heavy trailer.

I've been thinking about a 500W Bafang mid-drive kit. I am aware that they aren't road legal in the UK but I would only use it at 500W for the hill and would set it back to 250W at other times. I know this may not cut it with the police if challenged but I'm hoping that a middle aged rider, not going too fast and riding sensibly would hopefully not attract too much attention. I'm also going to be upgrading the brakes to make sure I have enough stopping power as I don't want to be dangerous to other road users.

Does this sound like a reasonable choice of motor for my purpose? There are 750W and 1000W versions too but I don't want more power than necessary. I think the 750W version is actually the same motor as the 500W version but presumably it has a different firmware setting. I'm assuming that it's possible to put the kit back to 250W output after it has been derestricted. Is that the case?

Thanks for any advice.

You can't make a 500w motor legal by riding at low speed, nor by cutting down the power. If it has 500w stamped on it, you're out. That's all the police look for. Woosh do a powerful TSDZ8 kit that will do what you want.

If the folding bike has 20" wheels or smaller, you'll be OK with a hub-motor if you get a 201 or 260 rpm 36v one and run it at 48v, which converts it to 260 or 328 rpm. The slower one will have good power up to 12 mph and max out at about 15mph, and the faster one will have good power at 15 mph and max out at 20 mph. The slower one is slightly better for climbing.

Hub-motors are generally more reliable and easier to fix.

 

[thelarkbox]

I agree with the above that in all but exceptional circumstances a bike that conforms with the regs can be configured for most situations.

If determined for a mid drive solution a Woosh sourced TSDZ8 with its 250w stamp should provide ample power, Otherwise overvolting and overamping a 'slow' 36v hub motor could provide you with the solution needed.

Dont risk your new bike and possibly the roof over your head for the sake of a watt rating on a motor when if you can recall school physics lessons Watts = Volts x Amps, regs limit us to 48v batteries, but give no limits on controller amp output - Now overamping a motor for an overly long duty cycle could generate heat and damage the motor, but if limited to short load durations (climbs only) there should be no problems.

 

[Simonh82]

Dont risk your new bike and possibly the roof over your head for the sake of a watt rating on a motor when if you can recall school physics lessons Watts = Volts x Amps, regs limit us to 48v batteries, but give no limits on controller amp output - Now overamping a motor for an overly long duty cycle could generate heat and damage the motor, but if limited to short load durations (climbs only) there should be no problems.

Is this something you can do with the standard interface? On the Whoosh website it mentions flashing the controller with OSF firmware but advises against it, whilst it is in warranty.

 

[Raboa]

BBS01ET

Woosh Bikes - Online Shop

Online shopping for electric bikes and conversion kits. All models are in stock unless otherwise indicated on the web page and can be despatched on the same day or next business day. We will email you the tracking link as soon as the item has been despatched.

wooshbikes.co.uk

 

[Nealh]

I tow a Carry freedom trailer with two bikes both are used for large shops and for carrying heavy loads of up to 100kg .
Both drives cope easily with the load.
Bike one is a Cotic Roadrat frame self build with a small 250w Bafang G370 front hub, unintentionally I have carried over 125kg of bagged manure from a garden centre a few miles away.
My other is Kona Ute cargo bike with a 48v 250w TSDZ2 mid drive.

Which drive system one uses depends on the riding style one wants to use , the TS mid drive requires one to make more input effort , whilst a hub will gamely pull a load with less effort .

For a hub one needs a low rpm winding and 48v will be far better then 36v .
For my needs I use Alfine 8 gears on the Roadrat with a double front 32t/42t chain ring .

For the mid drive I use 11t/36t rear cassette with the same 32t/42t chain ring set up.

My tsdz2 is modified for better internal heat transfer , temperature sensor and OSF firmware to aloow me to configure the power settings .

 

[matthewslack]

A 40m climb is a non-event unless it is vertical!

My puny 40Nm Shimano E5000 has taken me up 625m of continuous ascent (Bealach na Ba) at an all up weight of at least 130 kg without a problem.

All I did was change the cassette from 11-36 9 speed to 11-51 11 speed.

Any of the options described above are likely to be a pleasant surprise on the hill.

 

[thelarkbox]

Is this something you can do with the standard interface? On the Whoosh website it mentions flashing the controller with OSF firmware but advises against it, whilst it is in warranty.

my limited experience is with hub drives only and with hub drives and separate controllers, over volting and over amping is just a shopping list of replacement components to bolt on and plug in, Mid drives however contain the controller pcb internally so your limited to software cracks to eek out more power however the woosh tdz8 is a motor classified as upto 750w in other locations so it should be ample out of the box.

EDIT- I should add my bike is a conversion using a standard 36v rear wheel kit from yose-power, I regularly load up with a weekly shop 4-6kg spuds, 3-4kg of other veg/salad and at least 1 x 1.7kg bag of frozen chips and ofeten 2x 8xpop tins, alongside other less heavy items.. I mass circa 90-100kg , and only ride up about 10m or so over the 3-4miles back from the shops - While im aware of how to 'upgrade' my bike and have even ordered replacement controllers with higher output capacity than my basic stock controller- it turns out there is no need, Having little desire to ride any faster than 15mph (my bikes gears/chainring wont let me pedal comfortably any faster anyway..) and being able to lug about a pretty heavy load ok IM more than content with my bike as is..

 

[Nealh]

With my heavy trailer I have only used PAS2 (only a few times ) out of the five PAS levels with my Cotic hub Road rat , if one is cylce fit then one won't need much more input . Mostly PAS 1 is plenty for me with gearing to tow at 12- 15mph on a offroad bridle way for 6 miles.

With my TSDZ2 I have only ever needed Eco mode , I have yet to use other modes as it has enough oomph for me , I use gearing rather then power to get around and can still hit 20mph. Eco mode I have tweaked with OSF to proivde an extra 15 - 20 watts rather then the stock setting just so there is no need to go in to sport turbo mode.

Wher I live terrain is fairly flat, I need to go and find ascents to climb them but tbh I prefer to find flatter routes.

 

[AndyBike]

For what you have in mind, it isnt going to be wholly about the power in the motor, its going to be about the gearing.

As such a mid drive is going to allow for a wider choice on the back hub, though I admit to not knowing how many gear cogs you can fit on a rear hub drive.

But one thing is clear, which is the system, (if mid) then the hub, chain etc is going to need to be very robust.

 

[Nealh]

Rear hub will accept what ever gearing one fits, I have always used CST hubs with 9sp cassettes as they are cheaper to buy.
One can fit any gearing one want's typically I use 11t/36t or have used 11t/42t as well.

Any one who hasn't used a nice CST hub with a nice torque contol /current control KT control system won't know how much better they are then crappy speed controllers. Imv and from experience , I'd rather a cadence sensing KT with hub drive over a cadence sensing BBS middrive.

As with any hub one has to fit one with an ideal rpm winding for towing and ascents.

I like my TSDZ2 on the cargo bike on a run out it requires more rider input , the hub drive gives a more relaxed ride locally for town errands .

 

[Simonh82]

Thanks for all the advise. I've contacted Woosh Bikes about the TSDZ8 to check I can get it through the cycle to work scheme.

The kit looks like it comes with replacement wired brake leavers. That should be fine if I am convinced the V-brakes are strong enough. I'm also considering buying a second hand hybrid with hydraulic disc brakes as an alternative. Does anyone know if these conversation kits will work with hydraulic brakes?

 

[thelarkbox]

For Hydraulic brakes the common solution is stick on hall sensors and magnets that get stuck to the underside of the levers, usually offered as an alternative kit option.

 

[soundwave]

 

[guerney]

I'd like more details about the trailer, sketches, photos. Will the hitch be secured via a QR axle? 115.22kg combined weight of trailer+cargo, was deffo too much for the QT axle on mine, got yanked out of the rear wheel by the hitch. Fortunately I was only transporting water, nothing valuable or particularly alive.

https://www.pedelecs.co.uk/forum/threads/heaviest-haul-with-the-homcom-trailer-so-far.43921/post-661817

I really don't want that happening again, especially on a steep hill of course because the Homcom folding trailer has no brakes, and it's a busy hill. 115.22kg of trailer and cargo bouncing downhill and through a windshield doesn't bear thinking about...

https://www.amazon.co.uk/HOMCOM-Folding-Trailer-Bicycle-Storage/dp/B078W39W37

 

[saneagle]

Thanks for all the advise. I've contacted Woosh Bikes about the TSDZ8 to check I can get it through the cycle to work scheme.

The kit looks like it comes with replacement wired brake leavers. That should be fine if I am convinced the V-brakes are strong enough. I'm also considering buying a second hand hybrid with hydraulic disc brakes as an alternative. Does anyone know if these conversation kits will work with hydraulic brakes?

V- brakes are not going to be right for a cargo bike with small wheels. You'll wear through aluminium rims very quickly, and the braking force will be unreliable. If you going to spend all that money, you should do it properly.

Another thing to think about is the gearing. Crank motors are designed for large wheels. When you use them on bikes with small wheels, the gearing can be too low, especially if the bike has a freewheel rear hub (typically 7-speed or less).

 

[guerney]

I've become accustomed to the Bafang BBS01B's high cadence - wasn't a huge adjustment for me, because I was a "twiddling"/fast pedalling cyclist in the 80s. Gearing was too ludicrously low with the supplied 42T (>32T: 26.25 gear inches) chainring supplied with my BBS01B. Bafang's stock 48T (>32T: 30 gear inches) was bearable, but wasn't fast enough on the flats when not dragging trailers, Bafang's 52T (>32T: 32.5 gear inches) is about right for both speed (>11T: 94.5 gear inches) and uphill trailer hauling on my bike, but now that I've increased the controller's amperage limit from 15A to 20A, I'd spring for a 56T (>11T: 101.8 gear inches, >32T: 35 gear inches) if I was certain the chainline wouldn't cause problems using a BCD spider adapter.