eMTB build

[awol]

I want to start going off road so decided on a mid motor conversion, I picked up a Carrera Vulcan on sale.
----To add to the challenge when this build is complete I don't want to see any wires !!
I think I have achieved that.

I decided to go for a 250w GSM mid motor from Woosh since I already had spare external KT controllers etc to use and wanted to use parts I already had which added work to the wireless challenge.
Also wanted it road legal and speed cutoff will be 15mph as I don't think I will need more than that off road anyway.
At first the chain line was way way out so hand filed 3mm off the bottom bracket to move the motor over a bit.


Then fitted an offset 42t lekkie chain ring which now touched the chainstay frame, couple of dings with a hammer and some touch-up paint fixed that to give clearance.



I want to hide any wires out of the way through the frame so time to drill and file slots in the frame then touch-up the paint.




Same with the speed sensor, can't have that wire showing or catching on anything.



Motor wires head straight up to the controller hidden in the small tool bottle.



I could not get the internal PAS to work with my controller so installed an external one and epoxy glued the magnetic disc to the crank arm and now works fine.


The battery is my old 8ah 10s Lipo's with my favorite Speedict bluetooth connected BMS hidden and held quite firm in a large saddle bag big enough to upgrade when I get another Speedict BMS.

Battery wires hidden in the vertical frame, up and out through the seatpost directly into the bag. Seatpost movement is limited by the bottle mounting screw to prevent any wires getting cut.

My first rides with the GSM mid motor were different to a hub motor and I did not get on with it when changing gears so I added a gear sensor to cut the power when changing gear and give smoother gear changes when powered although I could do with the power cutoff a bit longer when travelling very slow, it's just visible at the top of the gear cable under the carrera logo.

Total weight with battery 19.5kg
Customer service and help from Woosh was excellent and the bike and motor combo is great and at 15a has plenty of power for me.
Now to go off-road and get some photo's to add to the emtb owners photo and ride thread.

 

[Dom T]

Well done to you, most impressive indeed. My first MTB was a Carrera Vengence (women one as stating the obvious) and it wasn't too bad a bike. You should be very proud of yourself.

 

[Nealh]

Nice job.

 

[EddiePJ]

Nice job, and nice write up.

 

[Fat Rat]

I hope you had that frame stress tested after you hacked holes in it .......

Only kidding nice build

 

[awol]

A look on the other side just to show now wires showing there either.

 

[awol]

Took it up a mountain to see how it performs and have decided the 42t Lekkie chainring is far too large for this type of riding for me and the motor, I think the 42t would be fine for road riding. Good job I ordered the smaller 36t at the same time to try. Will fit that this evening.

 

[peter.c]

Nice build
How did you get on with the 36 chain wheel I found it would not line up as it is not dished the 42 is the smallest I could get to align, the newer Carrera seems to be an odd bb must of been hard work with a hand file I cheated and used the angle grinder

 

[Denis99]

Some of the better equipped bike shops have a bottom bracket facing tool.

This is primarily usd to ensure that the bottom bracket shell faces are parallel to each other , and sometimes removing excess paint etc.

Could be used to trim the one side of the bb shell in this instance with some cutting fluid.

 

[anotherkiwi]

My external 42 tooth is fine as long as I don't try to use 1st and 2nd gear. The chainline is perfect in the top 3 gears - precialps spider and standard 104 BCD steel chainwheels. As where I live now there are some challenging slopes when commuting in white shirt and tie I have started using the 32 tooth chainwheel. The chainline is OK without being fabulous. A 36 tooth with a wide range 11-40 cassette would definitely do the job.

I admire your wireless frame - I won't be doing that to the trike however

 

[awol]

Nice build
How did you get on with the 36 chain wheel I found it would not line up as it is not dished the 42 is the smallest I could get to align, the newer Carrera seems to be an odd bb must of been hard work with a hand file I cheated and used the angle grinder

The chainline is clearly further out in 1st to 3rd but I have just been on a test ride on some bumpy ground and the chain did not drop off, the narrow-wide design helps I think, so will take it up a mountain again to try it out.

 

[awol]

Some of the better equipped bike shops have a bottom bracket facing tool.

This is primarily usd to ensure that the bottom bracket shell faces are parallel to each other , and sometimes removing excess paint etc.

Could be used to trim the one side of the bb shell in this instance with some cutting fluid.

I could have done with one of those, just looked at how expensive they are to buy too, but the bb being aluminium didn't take too long to file down.

 

[awol]

My external 42 tooth is fine as long as I don't try to use 1st and 2nd gear. The chainline is perfect in the top 3 gears - precialps spider and standard 104 BCD steel chainwheels. As where I live now there are some challenging slopes when commuting in white shirt and tie I have started using the 32 tooth chainwheel. The chainline is OK without being fabulous. A 36 tooth with a wide range 11-40 cassette would definitely do the job.

I admire your wireless frame - I won't be doing that to the trike however

I might give a 32t a go to get some serious torque up the toughest of slopes.

 

[peter.c]

A good result for piece of mind you could try a chain guide where the front derailleur used to be, mine used to come off at the least expected most time
one area the gsm is better than the bbs01

 

[awol]

A good result for piece of mind you could try a chain guide where the front derailleur used to be, mine used to come off at the least expected most time

The first time the chain drops off I will fit some sort of chain guide on, as you say it would no doubt happen again when I least expect it. At the moment I am actually trying to make it fall of by using gears 1 and 2 over a bumpy field as a test and seems ok so far.
One problem I have found about the 36t chainring is if I leave the bike in low gears, I cannot push the bike backwards into the garage without the deraileur clunking and getting all messed up because of the chainline being further out.

 

[peter.c]

Mine played up most in the garage if I pushed the bike backwards to move it /reposition it , also the derailleur was protesting when I put a new chain on old chain had just a small amount of flex in it

 

[awol]

Decided to go down to a 32t narrow-wide chainring. It pulls like a locomotive up the muddy inclines in 1st gear, almost losing traction in PAS-5 (15a). The chainline is even further out but hasn't dropped off yet.

 

[grecoa]

Nice job Awol

Looks very neat!

 

[Dom T]

Well tidy, how's it going ?

 

[awol]

Well tidy, how's it going ?

It's going really good and considering it's based on a cheap Halfords bike I am quite impressed overall. The gearing is great for off-road and getting up some steep muddy sections, or even through any deep mud.
Ideally I would like the chainline a bit better as when in 1st gear the chain makes a scraping feel as it's pulled across onto the front chainring but has not dropped off yet.
Although I would still like to compare power levels and also a battery range test against a purchased emtb sometime.
I found this forest about 15 mins from where I live when out exploring over the holidays, no way could I get around in there with any of my other bikes. Fantastic..