Here is a custom build that has several features I’d like to make sure the ebike world sees and understands. It is a non-hub motor that is only a one-speed, but…with enough power? Having only one speed might be all that you need. Deven lives in Canada.
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Revolt RV-120
Revolt is a company that makes several sizes of outrunner motor, a configuration that is familiar to RC enthusiasts around the world. Below is the CAD drawing that Deven used to help him plan out the mounting bracket for his swingarm-mounted motor.
A Revolt RV-120 with a custom mount. Deven ordered the version with a low 45-Kv
With an outrunner, the shell and the shaft both spin together. This provides a specific set of benefits and challenges to each application.
“There is a Russian forum that has guys using RV-120/100’s, but…with limited data/results”
A common industrial bearing flange, to support the shaft on the left.
The pic above shows the bearing flange that Deven used to support the motor-shaft on the left side.
The mounted motor and drop-out extensions.
Here, in the pic above…Deven has mounted the RV-120, and also the custom drop-out extensions that he needed, to move the rear wheel backwards enough for the rear wheel to fit. One benefit of this Norco frame is that the stock drop-outs already used a ‘bolt on’ interface, so it is fairly easy to make a version that is a different shape.
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The right side drive
There were actually several versions of this drive system that Deven tried, but here is the one he settled on. Deven took an aluminum adapter that allows a Shimano-splined freehub to accept a brake disc. Then…he attached a large-diameter brake disc, and after that…he bolted a large chainring onto it. This may seem to be a long and winding road to get to the goal, but it works, and…it allows Deven to drive a large chainring on the right side of his custom ebike.
Attaching a chainring to a brake disc, and bolting that to a splined adapter.
Here is a close-up pic of the Shimano splines that will mesh with a common and robust freehub.
A Shimano freehub normally holds a cassette of 8 to 11 sprockets. This adapter puts a large chainring there.
Here, in the pic below we see three individual sprockets that have been attached to the freehub. This is one of the several benefits of the freehub design. If there is one particular gear that you use more often than the rest? You can replace just that single sprocket when it wears out.
Here, Deven is only using three sprockets for the pedals to drive.
Here is a pic of the resulting rear wheel assembly. The drop-out extension has been anodized black, for a very professional look.
The swingarm, with the modifications installed. He added an idler wheel to deflect the lower chain-run over the chainstay. In this pic, the pedal-sprockets have not been installed yet.
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CNC, and Battery Holders
Deven had several ideas for parts that were not readily available, so what could he do about that? He bought a home CNC machine…so he could just make his own parts from scratch.
“The learning curve with the CNC machine was hard. Now I have SolidWorks and solidcam. I can make any parts. If you want a custom torque arm, just provide me a drawing and I’ll make it happen. I have redone the extended dropouts to make them more stiff and symmetric to the frame line”
A desk-top CNC mill.
Deven decided to mount a large battery pack onto the front of the ebike. This is not a common configuration, but…I have seen several full-suspension frame-builders take this path, due to the way that the rear shock intrudes into the center of the frame (which is the best location for the battery, if possible). Deven machined some mounts that clamped to the front-suspension fork stanchions, and they also incorporate a detachable flange for the battery box to connect to.
Custom battery box mounts
Below, Deven is showing how the detachable battery-box mount would fit.
These custom mounts really turned out beautifully.
Here is a pic of the battery box mount, all bolted together.
The final result. All that’s left is to bolt the battery box onto the mounts.
Now, we move on to the actual battery. Because of the way that Deven is mounting it, the battery pack can be a simple rectangle.
Dry-fitting the 18650-format cells to a plastic grid that Devon CNC’d
This pack uses 160 cells in a 20S / 8P configuration, which translates into…4.1V per cell X 20 = 82V when fully-charged.
Deven mentioned that the weight of this pack mounted on the front helps keep this ebike from pulling wheelies.
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The 2009 Norco Aline frame
The motor drive-sprocket has 11 teeth and the wheel sprocket is 52 teeth, giving a ratio of 4.7:1
Notice that the motor doesn’t run any power through the bottom-bracket, which is how most mid-drive systems work. If he had done that, the motor would have had the use of the gears on the bike, but Devens system has enough power that…it really only needed one gear. This configuration does not put any stress on the pedal crank-set, and it does not require a freewheeling crank.
“…The bike is almost too scary to ride at full throttle…Its a 4.3 kilo motor that can pull 15-kW peak…I’m using a 60A Crystalyte controller (stock). So I only push it to 6-kW now, and I want to mention that the motor only gets warm, even after some crazy and repeated hard accelerations…I’m waiting on the [Adaptto] Max-E controller, to really see how hard I can push that thing…Even now with just 6-kW the motor responds with authority…The back wheel is 26-inch, but I’m planning to change that for a 24…”
“…I have used many controllers with this motor. A 24-FET (4115), 18-FET (4115), and a 12-FET (4110)…I really like the acceleration with 18 FETs…All of my controllers are customised for higher power…”
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Written by Ron/spinningmagnets, December 2016
