Thorn Me’n’U2 Electric Conversion – Conclusions

The motor is now fixed, the speed sensor wire is lengthened and the sensor fitted, and the rear brake sensor is now fitted. We’ve just done an 18 mile ride with lots of hills. How well does it work?

Background

I’m around 85kg, the kids are around 50kg between them, and the bike is around 35kg with the electric motor fitted. Plus luggage. Say 180kg total – quite a lot to haul up a hill.

Most of that weight is on the front wheel.

No more worries about hills

The biggest change is that hills are no longer a problem. I used to be aware of all the hills I would have to climb – not worried but I would always have them in the back of my mind and would choose a route to minimise hills. Now I don’t think about them.

I’ve normally got the power set on 3/5. This is enough to easily climb hills (almost any hill) at about 8mph with low battery consumption. If I increase the power to 5/5 (max) then the speed will increase to about 12-13mph but the battery drops fast.

I no longer use the small chainring at the front – it isn’t necessary. Bottom gear in the middle ring is low enough for any hill I’ve found so far.

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Bafang BPM front hub motor cable replacement part 2

As mentioned previously I used the existing cable – just shortening it a bit. The remaining length is ok and I didn’t need to get a cable through the axle from scratch.

I carefully drew a diagram of the colours of the wires and reconnected the new ends to the correct colour. The soldered joints were covered in heat shrink and self-almalgamating tape.

I didn’t use any glue, putty or sealant. I reused the existing wire ties and added another around the omega clip.

Recut wire soldered in

Note that the wire exits the axle inside the motor on the same side as the aperture on the end of the axle. This means that if the aperture on the end faces downwards, and any water gets into the axle, it will drain into the motor. Whereas if the aperture on the end faces upwards then water cannot get out of the axle into the motor.

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Bafang BPM front hub motor cable replacement

As mentioned in a previous post I damaged the cable for a Bafang BPM front hub motor. I found various instructions on the web for strip-down instructions – notably this strip-down on Endless Sphere.

My motor isn’t exactly the same as any of the stripdowns I’ve seen – mine is a front hub 250W motor without sensors. I’ve put some details here if only for me when I need to do this job again!

The cover plate comes off easily enough and the motor unit can then be pulled out of the hub. Note any washers between the outer hub and the motor unit!

Two shim washers on the non-wire side of the hub

The clutch and planetary gears can be pulled off. The sun gear can then be unscrewed from the motor and the circlip underneath it removed.

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Thorn Me’n’U2 Electric Conversion Part 3

Good and bad news.

Good news

The conversion is finished and the motor works well.

LCD fitted and connected
Lots of wires everywhere. One day they might be tidier.

We did a 20 mile ride including 1100 feet of ascent and descent. It would have been a killer without the motor, but with the motor it was fun. It isn’t sophisticated but it is certainly effective – it can pull all of us up a steep hill without any pedal pressure but the battery doesn’t last long under that treatment.

I’m happy with the front-wheel drive and positioning of the components. The bike is very stable – and in slippery / muddy conditions the bike feels more stable with the front wheel driving as well as the rear.

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Thorn Me’n’U2 Electric Conversion Part 2

Some progress on the conversion.

Pedal Sensor

I’ve made a new pedal sensor rotor and sensor mount. I wanted a bigger rotor so that the sensor could be positioned outside of the radius of the tandem eccentric bottom bracket. Not knowing exactly how the sensor worked I kept the same distance between magnets, so the rotor now has 16 magnets instead of 12. The rotor is made from Tufnol as I had some, it is non-magnetic and glues well.

Test fitting the new rotor on the front crankset

The rotor bolts onto the drillings for the inner chainring. Most bikes will either have an inner chainring fitted or (for a tandem) a simple crank arm. The triplet tandem is probably unique here. I’m not sure if it makes any difference but I did make sure that the magnets are the same way round as the original rotor.

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Thorn Me’n’U2 Electric Conversion

The bike is fantastic, however pulling a total of about 180kg up long hills leaves me worn out. It is ok until I hit bottom gear but at that point there is nowhere else to go other than leg power. We’ve always got up the hills – and I am definitely fitter and stronger than I was – but with my partner having an electric bike she has been suggesting routes that I don’t want to do due to the number of hills. I’d like to be able to ride further without worrying about the hills. I’m also curious about the kits and how they would work in practice.

So I did my research and bought a BPM kit from Woosh. Woosh have a great reputation and Andy’s patient answering of my innumerable queries has been outstanding. The BPM motor has a good reputation for lugging heavy bikes up steep hills where other motors simply melt – very important given that I’m expecting this motor to cope with pulling anything up to 250kg up 17% (1:6) hills. It is a front wheel motor; as mentioned before the rear wheel of the bike doesn’t have much weight on it and I get wheelspin on slippery surfaces with pedal power.

The kit arrived promptly and quality was good.

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Boardman HYB 8.9e electric bike review

My partner needed an electric bike – it is hilly round here so an ebike was the only viable option. There were two important criteria:

  1. She isn’t particularly small, but the trend towards large wheel sizes means that most bikes are far too big.
  2. Her top priority was that it shouldn’t look like an electric bike – no bulky battery.

One of the few bikes that met both criteria was the Boardman HYB 8.9e with the Fazua battery and motor system. Both the battery and motor are in a removable lump that clips into the bottom of the downtube. The motor drives the bottom bracket via a three-lobed rotor (that forms the Fazua logo). It is a mid-drive unit – the motor power is transmitted via the normal gears and chain – with torque sensing.

Overall the bike seems to be good quality. The first bike seemed to have been dropped during assembly – the plastic top downtube liner was broken – but Halfords shipped out a replacement quickly and that bike has been fine. It rides nicely and the Fazua system works very well, providing plenty of power for even steep hills.

I did upgrade the firmware in the motor to version 2.0 and tweak the settings via the Fazua toolbox. This was easy to do and very worthwhile – the bike is much more powerful and responsive now. It is still entirely legal – the changes are better performance at a wider range of cadences, plus less rider pedal pressure for given level of assistance.

I’ve fitted mudguards and a rear panier rack. I like the way that the front mudguard eyelets are part-way up the forks. This is an important safety feature as it stops the front mudguard getting jammed in the front wheel if road debris gets between the tyre and mudguard. With the eyelets close to the wheel the mudguard gets closer to the wheel as the debris moves up, causing a jam. With the eyelets further up the mudguard moves away from the wheel releasing the debris and avoiding a jam. The panier rack is so she can lug the heavy stuff up the hills!

The bike is nice and light – about 14kg including battery and motor. It doesn’t feel heavy and is easy to lift around.

The only downside is the downtube. This isn’t actually a tube as it is part of the Fazua system – it is just a C shape so the battery and motor can be clipped in. This means it has very little torsional ridgidity – readily apparent if you watch closely while pressing on a pedal. In practice this doesn’t matter at all – the motor power means you never press hard on the pedals anyway!

Overall – recommended. My partner loves the bike and is happy to go on rides with big hills.

Mazda 6 Mk2 Rear Seatbelt Issue

I’ve got a 2010 Mazda 6 with about 100,000 miles on the clock. It’s a great car – lovely to drive and very reliable. However it did something interesting to me the other day.

I folded the rear seats down to get a bike in the boot. When I tried to put the seats back up one side wouldn’t move – the seat belt had locked itself. I suspect the inertia reel units have something to stop them locking in the down position and this has stopped working due to age.

The seat is designed to be worked on when it is in the upright position – locked down everything gets much harder! I wanted to take the car to the garage for them to have a look but all the Mazda garages are closed due to COVID-19.

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Vitruvius on lead pipes

I recently received a copy of Vitruvius’s On Architecture. This is a guide for professional engineers written in about BCE10. Vitruvius worked for Julius Caeser and was granted a pension by Augustus.

The first impression is of a modern attitude towards engineering. Whilst some of the conclusions are not in alignment with modern thinking the overall impression is that you could take this book, follow the instructions and the results would be satisfactory. The theory as to why you should do certain things is dubious, but the conclusions seem sound.

I’ve only browsed the book so far, but my biggest surprise is that he says lead pipes are poisonous:

Besides, water from terracotta pipes is much more healthy than that taken through lead pipes, which seems to be particularly damaging seeing that white lead, said to be harmful to the human organism, derives from lead.

So it is obvious that water should never be conducted in lead pipes if we want it to be beneficial to our health.

This was over 2000 years ago. I’d always thought that lead being toxic was a modern discovery. I grew up with:

  • Leaded petrol
  • Lead in paint
  • Lead water pipes (lots still around and in use)

So I am boggled that lead was known to be a problem over 2000 years ago!