Electric Bike Conversion

 Ged suggested I should put a few words down for those that are interested in my electric bike conversion.

So here goes. I decided in early 2021 I wanted to build a Gates Carbon Drive touring bike with Rohloff 14 speed hub gears. The problem with this plan was that there are very few frames made that can cope with the tolerances for the hub. Indeed Rohloff won't supply the hub unless it is through a wheel builder. Bikes of this sort started off at £5000 plus so I was hoping for a lot of luck. I chose an all steel Soma Wolverine frame made in Taiwan weighing 3.8 Kg as it had a following in the US.It was versatile enough to be set up with derailleur,single speed, or ,yes you guessed it-Rohloff hub gears. To cut a long story short I built the bike with hydraulic disc brakes and got the weight down to 13 Kg. However the riding experience was mixed.The Gates Carbon drive is very smooth and consistent in operation and the TRP Hylex brakes with kevlar pads worked well. The ride was also comfortable.The difficulty was with the weight at the back due to the hub gears and the operation of gears 1-7 which uses a peripheral internal cog. This has a friction element which whines and makes harder work of ascents. However gears 8-14 were smooth and silent. So when out for a Wednesday ride I would tend to choose my 8.5 Kg Van Nicholas or 9.5 Kg Canyon. The Wolverine tended to be left at home more often than not despite having fast rolling Continental GP 5000 tubeless tyres, and it became a winter bike because of the low maintenance factor. Nevertheless I have completed 2600 miles on it trouble free. Total cost of the build was £3700.

One ride we did, Mark Gladwyn suggested I convert it to an e bike. Now I had this idea at the back of my mind when I built it and so I set about researching crank motor kits online. Eventually I spoke with Whoosh Bikes in Southend, who supply Chinese imported kits. I chose a Tong Shen 48 volt, 250 W kit with a 720 W h battery. It came with a 44 tooth chain ring which I had to swap for a 50 tooth CDX alloy carbon drtive sprocket. I also had to get a Spyder adapter with 130 BCD to fit the new sprocket to the motor. Removing the old chain ring was easy, just 5 allen bolts. I managed to get a spyder from China via Ali Express and found a front carbon drive sprocket on ebay for £55 instead of 120 euros from Germany. The kit came with a couple of riv bolts for fitting the battery case, but as the battery was 3.7 Kg and was supposed to be screwed to the down tube of the bike without any other support I wasn't happy. The flat surface of the battery mount would soon have torn out the riv nuts from the round frame. So I bought four Zefal Gizmo bottle cage mounts and cable tied these to the down tube. Not a very elegant solution, but the battery sits firm and stable in its mount.

The rest was straightforward fitting the wiring and using amalgamating tape to waterproof the connections. I know it looks a bit Heath Robinson, but it all works. I dispensed with brake levers, remote control and lighting and just fitted a speed sensor. The motor works by a torque sensor inside, which senses how hard you push on the peddles and assists in kind. When you stop peddling the motor cuts out so it is easy to change gear on the move. There is a display which shows your speed, time, distance and four levels of assistance. When the speed gets to 15.5 MPH or 20 KMH the motor cuts out.

One of the dilemmas of this configuration is that rear wheel removal is not viable in use and so a rear flat tyre would be painful. So I have fitted a 38 mm Schwalbe Marathon Green Guard rear tyre along with Tannus Armour tyre insert, which is a 20 mm foam rubber insert. I am hoping the combination will prevent the puncture gods from visiting. Just in case I also carry a Gaadi inner tube, which is like a long sausage, so you can replace the inner tube without having to take the wheel off. The front tyre is a normal 32 mm Scwalbe Marathon Supreme, because I am able to remove the front through axle by quick release.

So what is it like to ride? Well when I pushed the bike up my drive to go for my initial ride I could feel the weight of the 22 Kg I had ended up with and I thought 'I have created a monster!'. However after a couple of miles I go to grips with it. The bike handles well and once you are moving, the 90 Nm motor feeds the power in gently. The motor is very quiet and in the first level of power assist you don't think anything is happening until a rise in elevation and then you feel the bike surging forward as you peddle harder. The second level is about right, which give a nice kick up hills and then cuts power as you stop peddling to cruise downhill. That's when you feel the weight where a small incline down gets you past the 15.5 MPH speed and the motor cuts out. So really it is a different technique to learn with an e bike. I was surprised at how powerful the motor is, making the 14 speeds in the Rohloff mostly redundant and I was peddling comfortably in 11 gear on undulating terrain. I have to confess the ride was hard with the Tannus insert in the rear tyre, but it has a 20/28 mm inner tube which I will have to try and adjust the pressure for more comfort and to stop the tyre crashing over rough road surfaces. I have a lot more experimentation to do yet, like peddling the beast with the motor switched off, but the object of turning an unloved steed into something much more desirable has paid off.

If you fancy converting your own bicycle I can recommend Whoosh Bikes. They also do a range of electric bikes that are very good value. Despite the Chinese motor, the kit is good quality and they use Japanese Panasonic batteries in the battery build so they shouldn't explode and burn your house down. My kit was £705 including delivery. I had to get another £100 of sprockets and fittings to convert to carbon drive, so quite reasonable. My kit also came with a 48 volt 15 Ah 720 watt battery which theoretically will last 3 hours at 250 watts or full power. However, the way the motor feeds power in only when needed means it will probably last 6 hours depending on the level of assistance, because you are only really drawing on the battery by ascending. Anyway I hope you find all this interesting.

Steve D.