D
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A guy I know had this rather expensive carbon fibre MTB and wanted it converted. He's the sort of guy that says. "where there's a will, there's a way". His forte is converting road cars. His Nissan Quashqai can do a no bullsh!t 230 mph, and it drives on the road like any other car even though it has 1800 BHP, which is nearly twice as much as a Bugatti Veyron:
The bike is top of the range Trek Pro Fuel 9.9 with carbon fibre frame and every nut, bolt and screw made of titanium. It's very light for a MTB, something like 10kg.
It has lots of problems when it comes to conversion:
Through axles means a hub-motor wion't fit.
Carbon fibre frame is virtually impossible to fix anything to and can't accommodate any torque applied.
BB90 bottom bracket is the wrong size for a crank-motor
Not withstanding the non standard BB, It looked like there would be insufficient clearance around it to fit a Bafang BBS motor. We decided to take a chance and hope that we could shoehorn it in, so I ordered the 1000w BBSHD and a 50v 19Ah triangle battery from Em3ev.
In the meantime, I disassembled the BB and found a web on each side that would prevent the motor shaft from passing through, so I removed them with my dremmel. It really worried me hacking this frame, which probably cost £3000 on its own. I then sketched up some special inserts that would fit exactly to the profile of the bit of the BB where the bearings were with a inner diameter to fit the motor shaft.
The motor arrived, but the shaft wouldn't go through, even without the inserts in place. The gear cable and rear brake cables go through the frame and exit at the BB right where the motor would go, so we decided to run then externally and remove the terminal plate, which added a bit of thickness to the BB. With all that out the way, the motor just fitted with about 1 micron to spare.
The next problem was to find a way to resist the torque from the motor. Bafang provide a clamp plate that stops the motor from dropping down and relies on the motor resting against the frame to resist the torque, but the shape of the frame around the BB meant that as soon as the motor twisted, it was giving a massive crushing force to the thin carbon fibre moulding. The only anchor point for a torque plate was the suspension pivot bolt, which turned with the suspension, so we couldn't clamp anything to it/ We therefore took out the pivot bolt and made our own with an extra arrangement on the end to locate the plate without clamping it.
That was all the hard work done. After that, it was only a question of switching connectors on the throttle for a left hand one, which fitted in the space left after the front changer was removed; modifying the bag that came with the battery because it was miles too big for the battery and frame; and rerouting the brake and gear cable down the outside of the frame. here's the finished bike, pending further battery bag mods. I kept the front derailleur to stop the chain jumping off. I used the end-stop screws to hold it in position.
What's it like to ride? Well, it was a bit of an anti-climax. it seemed very docile considering its power. The power was programmed to increase with increasing speed/time, so it was very easy to manage and easy on the gears, but if you kept the throttle open, it got faster and faster. 30 mph was pretty easy. I fitted the gear sensor that cuts the power when you change gear, It worked very well, much better than OEM systems I've tried. It's probably the most user friendly crank-drive bike I've ridden with no crashing from the gears, and it's totally silent. All-up weight is a mere 25kg, which is very light considering the size of the battery.
I've now returned it to the owner who seems happy with it. His mate has an ordinary BBSHD with a 48v battery. In a side-by-side test, he said that this one was noticeably more powerful, so it's worth getting this one set up for the 14S battery from Em3ev.
The bike is top of the range Trek Pro Fuel 9.9 with carbon fibre frame and every nut, bolt and screw made of titanium. It's very light for a MTB, something like 10kg.
It has lots of problems when it comes to conversion:
Through axles means a hub-motor wion't fit.
Carbon fibre frame is virtually impossible to fix anything to and can't accommodate any torque applied.
BB90 bottom bracket is the wrong size for a crank-motor
Not withstanding the non standard BB, It looked like there would be insufficient clearance around it to fit a Bafang BBS motor. We decided to take a chance and hope that we could shoehorn it in, so I ordered the 1000w BBSHD and a 50v 19Ah triangle battery from Em3ev.
In the meantime, I disassembled the BB and found a web on each side that would prevent the motor shaft from passing through, so I removed them with my dremmel. It really worried me hacking this frame, which probably cost £3000 on its own. I then sketched up some special inserts that would fit exactly to the profile of the bit of the BB where the bearings were with a inner diameter to fit the motor shaft.
The motor arrived, but the shaft wouldn't go through, even without the inserts in place. The gear cable and rear brake cables go through the frame and exit at the BB right where the motor would go, so we decided to run then externally and remove the terminal plate, which added a bit of thickness to the BB. With all that out the way, the motor just fitted with about 1 micron to spare.
The next problem was to find a way to resist the torque from the motor. Bafang provide a clamp plate that stops the motor from dropping down and relies on the motor resting against the frame to resist the torque, but the shape of the frame around the BB meant that as soon as the motor twisted, it was giving a massive crushing force to the thin carbon fibre moulding. The only anchor point for a torque plate was the suspension pivot bolt, which turned with the suspension, so we couldn't clamp anything to it/ We therefore took out the pivot bolt and made our own with an extra arrangement on the end to locate the plate without clamping it.
That was all the hard work done. After that, it was only a question of switching connectors on the throttle for a left hand one, which fitted in the space left after the front changer was removed; modifying the bag that came with the battery because it was miles too big for the battery and frame; and rerouting the brake and gear cable down the outside of the frame. here's the finished bike, pending further battery bag mods. I kept the front derailleur to stop the chain jumping off. I used the end-stop screws to hold it in position.
What's it like to ride? Well, it was a bit of an anti-climax. it seemed very docile considering its power. The power was programmed to increase with increasing speed/time, so it was very easy to manage and easy on the gears, but if you kept the throttle open, it got faster and faster. 30 mph was pretty easy. I fitted the gear sensor that cuts the power when you change gear, It worked very well, much better than OEM systems I've tried. It's probably the most user friendly crank-drive bike I've ridden with no crashing from the gears, and it's totally silent. All-up weight is a mere 25kg, which is very light considering the size of the battery.
I've now returned it to the owner who seems happy with it. His mate has an ordinary BBSHD with a 48v battery. In a side-by-side test, he said that this one was noticeably more powerful, so it's worth getting this one set up for the 14S battery from Em3ev.
