looking for a conversion

[janz70]

hi. I'm looking into converting my canondale hybrid into an e bike and would like some suggestions on which kit or bits to buy.
it will need to do 15 miles min on a charge in the depths of winter and be a able to steadily climb 140m over a few miles.

 

[vfr400]

Show us a photo of the bike. How heavy are you?

 

[janz70]

Im a big unit - 21 stone 6'2"

unfortunately where I live in the country side the roads are really rough and knock the hell out of me on the cannondale contra so might choose my old trek 930 antelope instead for the front suspension but its fairly heavy bike to start with - not that it matter with my weight on it

 

[vfr400]

At 21 stone, most of the off-the-shelf kits are going to be inadequate. That includes the 1000w ones. I'd be looking at a relatively slow 48v motor. Ideally, you want something like a 250 rpm 48v rear motor, a 20 amp controller and a battery capable of 25 amps.

I'd be looking at a steel catalogue-type bike with a triangle frame and disc brakes as a donor. One with seven gears at the back will also be ideal so that you can use the more robust and more powerful freewheel motors. You can use those motors on any bike, but they become too wide if you use more than 7 speeds. If you have say 9 speeds, you have to change the shifting system to go down to 7 speeds in order to get accurate shifting.

You can use a cassette motor if you have free-hub gears (any number of speeds), but you give up a bit of power and robustness compared with the freewheel motors. Also, you need a large dish in the wheel because of the length of the cassette spline. Dishing is not good for heavyweight riders because of the difference in spoke tension from one side to the other, which makes the dish.

 

[Mdoodles]

For what it's worth, I have a commute similar to yours: 14 miles with a total elevation of 400ft for a single leg, mostly on tarmac. I converted my 26'' hybrid with the Woosh (non-throttled) TSDZ2 kit. I can do 3 legs of that commute on a single charge and the maximal assist level throughout, although I am currently doing two: recharging at work so that the battery is at its freshest on the return leg. I am 'only' 14 st and live on Scotland so crap weather is a given. So you are 50% bigger than me and have slightly more elevation to contend with so with luck/lower assist levels you might do 2x15 miles. I don't see 15 miles being a problem tbh.

The kit is a crank drive with a torque sensor so that, in contrast to cadence base sensor you have to provide some of the effort when it is needed (33% of it I believe) and you might shed some of the pounds too...

 

[vfr400]

I forgot to add that the Woosh SWX02 48v kit will meet your requirements for torque and power if you don't want to buy from China. Bear in mind what I said above about free-wheel motors.

 

[janz70]

I thought all motors had to be 250W in uk to be road legal, so if a 1000w motor is powerful enough surely nothing will be ?
I have checked out the woosh at £570 - is a little pricey what chinese ones would you recommend?
Mdoodles - not looked at middrive units - is it easy to fit - need any special tools - I can only find 500W models, are these legal in the uk.?

I can charge my battery at work after the commute there so it wont have to do more than 1 x 15mile journey before being fully charged again
I am not expecting it to carry me to work without any pedaling, just for it to give me a hand on the tough climb and when I am flagging on the second half of the journey.

How do they actually work, I ve seen some provide 80% of required pedaling or do they just pull you along to upto 15mph backing off power the more you pedal upto 15mph and once at 15mph do they they stop providing any power.?

 

[sjpt]

I have checked out the woosh at £570 - is a little pricey what chinese ones would you recommend?

By the time you factor in decent battery, quality controller and head unit you may see the price difference for Woosh isn't as much as you think. And you are gaining excellent support, the knowledge all the bits will work properly together, and the assurance there won't be any nasty import/VAT surprises.

How do they actually work, I ve seen some provide 80% of required pedaling or do they just pull you along to upto 15mph backing off power the more you pedal upto 15mph and once at 15mph do they they stop providing any power.?

Torque sensors give you a power multiplier of what you put in; on highest rating that might be 4 times, so as you say you do 20% and it does 80%. If you don't put in any effort it won't either.

Cadence sensors usually just sense if you are pedalling or not. If you are, it turns on to give the amount of power you have selected. You can 'ghost' pedal just to keep it going, it puts in all the effort, If you pedal properly, your power is added to its power.

Torque feels more natural, but it is really nice to be able to put in no effort sometimes. Torque is more common with crank drive and cadence with hub drive, but that is by no means an absolute rule.

 

[vfr400]

When you're heavy, it's torque that you need, not power. Power =torque x speed. Those 1000w motors make their maximum power at high speed with low torque.

Those 1000w motors have low efficiency at low speed, so if you put 1000w in at 5mph, you'd be lucky to get 250w of output motive power. The remaining 750w would turn the motor into a nice three-bar electric heater. Generally, motors have low efficiency when they're running less than half of their maximum speed.

Also, the rating of the motor is not the power it outputs. A typical geared 250w motor can sustain around 500w of output power.

The amount of power that goes into the motor depends on the controller and battery, not the motor.

 

[Mdoodles]

Mdoodles - not looked at middrive units - is it easy to fit - need any special tools - I can only find 500W models, are these legal in the uk.?

It is relatively easy to fit (more on this below) and yes you will need specialised tools:
- to remove the cranks: a crank extractor as well and a cartridge bottom bracket tool. This is the minimum. To install the motor itself there is a tool that comes with the motor then it's bog-standard allen keys. Then there's this, possibly:
- To install the battery you might need a rivnut kit. The bottle holder nuts might not be in the right place in your frame so you will need to put extra holes and rivnuts (note an alloy frame will be easier than a steel one in that respect). Then there's this:
- I had to change the chain and the cassette because both were in a pretty dire state so I had to get chain removal tools and a cassette removal tool too. (NB: I had also to change the derailleur and the cable). Even if your cassette and chain are OK, you will need that eventually. Apparently crank drives go through these items quite quickly (I am carrying a spare chain at all time in case it breaks), especially if in daily use I expect. You won't need that if you use a hub drive.

Re easiness of fitting: My only bicycle repair skill before this was to repair a puncture. Now I can do all of the above plus index gear shift, change a fork (I have not done that yet, but I just checked I could take it out, will put a suspension fork in the summer maybe), etc. Basically, I don't expect to need a bike mechanic ever again for me and my family. It might sound daunting but you are not on your own: there's plenty of resources online on how to carry out these jobs (youtube, mainly). Note I have a completely unrelated trade (data analysis).

Cost: The kit cost me 660 (it was the non-throttled version) but the whole thing came down to 1.25K which breaks down into:
- 1k for the motor and a replacement push bike (+equipment) plus various equipment eg mudguards, pannier etc
- Aforementioned tools, which I will reuse anyway: 150£
- Aforementioned repairs/replacement parts, which I would have had to carry out anyway at some point: 100£.

I hope to recoup that within 1-2 years through saved train fares/petrol and car depletion. I went through woosh because i wanted a UK based vendor in case of problems (there weren't any btw).

Legality: Re the power 500W is illegal but it is a bit of a grey zone since even though my own motor (and all other legal ones) is rated 250w it can peak at higher power. I think 250w is an upper limit on the average power delivered (which raises my data analysis eyebrows). There are -I believe- two physical versions of the TSDZ2: 48V (the one I have) and 36V, the power rating depends on how much the controller lets electricity reach the motor.

The other legal (and less ambiguous) imperative is the upper assist speed limit (15.5 mph). Once you reach this speed, the assist cuts out and you *do* notice (there is an internal clutch and I suspect it to stay engaged above the speed limit). This is an annoying not-so-sweet zone, since it's a speed I can normally easily attain on the flat. I basically always pedal just below that limit and anytime I do surpass it is while freewheeling downhill. It is relatively easy to up the limit via the controller and I did try for a couple of legs but then reverted to the legal setting because: i) The time gain was not that great - I decreed my employer could afford an extra 10 minutes of absence ii) it hit my range, the battery was noticeably emptier iii) It voids the 1 year warranty iv) legality/liability in case of accident.

Crank vs Hub drive: Crank are the only types of bikes I tried and I liked them. I would advise you do the same (the trying, the liking is up to you). The closer the TSDZ2 was the bosch ALP system, which has a great acceleration (as opposed to the yamaha one which is less 'in your face' ). I fact I nearly bought a haibike/yamaha but it was out of stock. I read on forums such as this one that mid drives have better range and also are better at steep hill. I don't know about 'better' but it is certainly good enough: I have a >10% section on my commute and I don't break a sweat on it. Also, my particular donor had hydraulic disc brakes and I struggled to find hub drives which could accommodate that (this is also the reason I chose the non-throttled version). Hub drives, I heard, are less natural for keen cyclists. Again: do go and try different systems.

HTH

 

[sjpt]

The remaining 750w would turn the motor into a nice three-bar electric heater.

I absolutely agree with your points; except it will turn it into a 1 bar (approx) electric heater.

 

[vfr400]

I absolutely agree with your points; except it will turn it into a 1 bar (approx) electric heater.

I said three bar because there are three coils (phases) heating up.

 

[janz70]

I was enquiring about VFR400 reference to buying from china.

I forgot to add that the Woosh SWX02 48v kit will meet your requirements for torque and power if you don't want to buy from China.

 

[vfr400]

I was enquiring about VFR400 reference to buying from china.

You buy from China to get the best kit, not the cheapest. You can buy the cheapest kit from China, but it's not the best. The right stuff from China would cost about £600 upwards. It would give you the option of more torque.

You still haven't shown a photo of your bike.