Cytronex ebike kit on Thorn Club Tour

[jr970]

I think there was a post on this a few years ago, so FYI here is an update for anyone considering this. Following a tendon operation last year I decided I'd like the option of some mild assistance for a tour we were planning in Germany. I already had a Cytronex bike conversion (on an old Orbit Romany) so it was a cheap option to convert my Sport Tour and re-use the battery/controllers I already had.

I ordered the kit from Cytronex in August & fitted it a few weeks before the tour. As I had the lighter (MER853VC) forks I decided to get a new heavier duty Thorn Steel fork (the type with front low loader mounts) for the fit. To fit the new rim/motor from Cytronex I needed to file off the Lawyer Lips & a remove a layer of paint off the dropouts, but otherwise the fit was OK. The rest of the kit is straightforward to fit with a little fiddling with the the cable routing.

As you can see I took two batteries. The ride was a reasonably flat "river ride" (Main Radweg, but in the "uphill" direction from Maniz to Bischofsgrun) so I was able to use the bike "engine off" for about 60% on most days, saving the battery for hills & headwinds (which plagued us for five of the nine days). I carried about 14Kg of luggage, spares & water bottles etc, plus the weight of the cytronex system  (about 5.5Kg with two batteries, motor and charger). You also need to remember to carry a 17mm spanner for the front wheel!

Used this way a single battery was good for up to 45 miles, so with our schedule I only needed two batteries on our longer days (55-60 miles) and for the last days climb (1600ft ascent).  I very rarely needed more than the 1st level of assist (which uses about 50W) - this took out the headwind (15-20mph) and on the climbs counteracted the weight of the luggage fairly effectively. Levels 2 and 3 were used briefly on a few short very steep sections (1:8 or worse) as my quads are rather weak post-surgery.

My experience is that the system works well, does'nt add a lot of weight and is fine to cycle "off" on the flat or if you have tailwind (I wish!). It's not torque sensitive so you have toggle the levels of assistance manually and be sure to toggle off when not needed (it will continue to provide the selected level of power as long as you are turning the pedals). It was very convenient to be able to carry the bottles into our accommodation for charging, although many places in Germany are set up for ebikes in their bike garages.

I also have a "full" ebike with a Bosch Hub motor for comparison & the Cytronex system is a very different experience,  in use it feels more like a "normal" bike ridden with a gentle tailwind, whereas the full ebike is noticeably heavy but flattens out the gradients so you go up a moderate hill with minimal additional effort. Both of course are limited to 15mph assistance - the "full" ebike is noticeably more effort once the assistance is off, where the Cytronex bike just feels like a normal bike with an extra 5kg of luggage. There is a tiny amount of drag from the cytronex hub motor but in freewheel test I could'nt see any difference from my mate's unpowered Raven Sports Tour.

The other thing I like, made easier by having two sets of forks, is that it will be a relatively short job to convert the bike back to standard if needed.  My experience with support from the Cytronex team (based in Winchester) has been excellent with a few queries responded to within 24 hrs.

I'm sure this voids all sorts of Thorn warranties, but as you see I've already fitted a kickstand (almost universal in Germany) 

[Andyb1]

About 5 years ago I converted my wife’s alloy framed hybrid to electric with a 250W front hub motor.   

It was a fairly crude system with the battery on a rear rack and the motor was controlled by a thumb throttle (so I had to remove the front changer) - but it worked fine.  I had to gently file the dropout to take the motor’s 10mm axle as the fork was designed for 9mm, otherwise very easy to fit.
The advantage of a powered front hub was that without power it rode like a normal bike with no extra drag.  It also gave her two-wheel drive, useful in slippery conditions.  Like jr970 she just used the motor on uphills and headwinds and we never had any battery issues.
Negatives
- it was quite a heavy system, but modern batteries have helped reduce weight
- she had to constantly push the thumb throttle to get power
Otherwise great, we only changed it this year as she wanted larger tyres and her hybrid had small clearances (700c wheels in a small frame alway seem a bit too big to me).

One other thing, when I fitted the motor a friend advised that I add stainless steel torque brackets to the wheel axle.  These are slotted to stop the axle spinning and bolt to the mudguard stay bolt holes.   With an alloy fork as she had I think they are essential but even on a steel fork they stop any chance of the axle spinning, which would cause a lot of damage.

[jr970]

Thanks Andy

In case anyone wonders the Cytronex system comes with slotted torque washers to secure the axle (which is why you need to file off the "lawyer lips").  It fits standard 9mm diameter dropouts, but they need to be at least 10mm deep to accommodate the torque washer. They have printable templates which you can use to check the fit & clearances....

[Andre Jute]

Thanks for sharing, JR; an interesting read.

I've fitted two aftermarket electric motor kits, both to the same Utopia-velo Kranich, both motors from Bafang, the first one a front drive motor, which burned out its control electronics in around 3500km, the second one a bigger Bafang centre motor. I didn't reuse the battery from the first kit, opting for something near enough twice the capacity with the new motor, which is more powerful by 40% than the first one, which I though was a bit undersized for my size and the mass of the loads I sometimes carry.

Someone may ask why I bought a second Bafang motor after the first one failed. Saying the motor failed is shorthand, it was actually the control electronics that burned out, though there were signs of the nylon gears inside the front hub motor being under thermal stress. I had in fact bought the first motor and battery and controller kit to get the hang an electric bike, and decided in advance that it would be a sacrificial installation, an educational cost. So I thought it good value to get 3500km of all-steep-hills out of an underpowered but legal (in England, where I bought the kit) that I had calculated would suffer some level of thermal stress due to the character of the lanes I ride and lugging all my painting gear; in fact, it wasn't even all a write-off as I was left with a good 8Ah bottle battery, and the motor was still operational if I want to make or buy new electronics.

The replacement was a more powerful motor, which I calculated to possess the minimum torque required for the terrain and kind of use I put the bike to. I've been very satisfied with this installation, the proprietary software, and the large battery.

The need for a large battery arises because I use the electric motor as a fill-in, not an electric motorbike, controlling the motor by my heart-rate as reported by my iPhone on the handlebars, which means the motor is normally required near the top of a hill, and for several seconds or at most a few minutes of high current output. For this need I appropriated the unit Coulomb, which for electrified touring and utility bike purposes is the maximum current instantly available for a sustained but short term high-current delivery. Interestingly, the current BMW-built Rolls-Royce has no rev counter but instead a residual power meter, which meets my redefinition of the Coulomb. Also, if you have a power bar on the control facia for your motor, that too reports instantly available current, so it too meets my redefinition.