briangv99
1 kW
Five or so years ago I bought a run out special Nukeproof frame from ChainReactionCycles. At the time the appealing features of the Mega TR were the relatively large frame triangle for battery, removable dropouts that made for a easy conversion to steel plates for fitting a hub motor, all packaged in a frame with modern geometry suitable for some hard single tracks that we have locally.
After a detour, exploring using a Tangent Astro 3220 mid drive, I've come back full circle to the original plan of installing a MAC motor, but with a twist. Since my original MAC plans, Grin Bikes came out with the awesome GMAC. Grin addressed most of my lingering complaints with previous MAC builds. Number one, no more clutch bind up and fail. Two a much more robust and sophisticated slop free torque arm, eliminating the need for a separate torque arm. Three, cable exit the site of the axle instead of the end of the axle, which is much better protected from stray rocks slicing the wires.
The side benefits/disadvantages of no more clutch is the ability to implement regen and active braking. The downside is the motor will always be turning with the resultant drag from core loses of magnets passing over the stator at a 5:1 ratio. The ability to regen for the most part offset the additional core losses. To mitigate the extra drag while pedalling, I'll also be feeding in PAS through an E-rider torque sensing BB.
Now all that was missing to cap off the list of components was a suitable controller. Enter Nucular with their awesome 12 fet controller. This controller really does it all and supports all the tuning features I wanted and more. Regen couple with active braking gave me the opportunity to try out something I'd seen Ripperton implement with his Yamaha R1 race bike years ago, a pressure tranducer coupled to brake master cylinder.
https://endless-sphere.com/forums/v...=2&t=63341&p=947733&hilit=regen+bleed#p947733
I'm still amazed how well this just works. The modulation of the brake force through the Nuc is super smooth and quite strong all the way down to a stop. It doesn't have brake locking power, just smooth strong deceleration. Of course I'll still have the back up of a full friction brake on the front wheel.
A side benefit of ditching the rear disc rotor is that I'll be able to run ATF in the GMAC for cooling without any fear of any stray ATF lubricating the brake rotor and pads.
Now hub motors aren't light and unsprung weight isn't great for maintaining traction in rocky terrain, so I've shed as much weight from the rear wheel as possible. The GMAC is relatively light weight, coming in at less than 4kg. To keep that weight down I've laced the motor with a Lightbicycle carbon 26" 40mm internal width rim, using 15g spokes, rolling on Maxxis 26x2.8" DHR2 tubeless tyres.
I've only just got the bike wired and running on the weekend, so there's a list of things still to get done, like fitting a front brake, wiring the PAS, fit dropper post etc, so this is how it looks at the moment.
So far the few test up and down the local street has been very promising, the Nuc 12F GMAC combo is super smooth and quite punchy at 2500 watts. I did have a slight brain fart during the build and forgot to secure the torque arm, hence the rejoined wires near the back axle and having to replace a hall sensor.
After a detour, exploring using a Tangent Astro 3220 mid drive, I've come back full circle to the original plan of installing a MAC motor, but with a twist. Since my original MAC plans, Grin Bikes came out with the awesome GMAC. Grin addressed most of my lingering complaints with previous MAC builds. Number one, no more clutch bind up and fail. Two a much more robust and sophisticated slop free torque arm, eliminating the need for a separate torque arm. Three, cable exit the site of the axle instead of the end of the axle, which is much better protected from stray rocks slicing the wires.
The side benefits/disadvantages of no more clutch is the ability to implement regen and active braking. The downside is the motor will always be turning with the resultant drag from core loses of magnets passing over the stator at a 5:1 ratio. The ability to regen for the most part offset the additional core losses. To mitigate the extra drag while pedalling, I'll also be feeding in PAS through an E-rider torque sensing BB.
Now all that was missing to cap off the list of components was a suitable controller. Enter Nucular with their awesome 12 fet controller. This controller really does it all and supports all the tuning features I wanted and more. Regen couple with active braking gave me the opportunity to try out something I'd seen Ripperton implement with his Yamaha R1 race bike years ago, a pressure tranducer coupled to brake master cylinder.
https://endless-sphere.com/forums/v...=2&t=63341&p=947733&hilit=regen+bleed#p947733
I'm still amazed how well this just works. The modulation of the brake force through the Nuc is super smooth and quite strong all the way down to a stop. It doesn't have brake locking power, just smooth strong deceleration. Of course I'll still have the back up of a full friction brake on the front wheel.
A side benefit of ditching the rear disc rotor is that I'll be able to run ATF in the GMAC for cooling without any fear of any stray ATF lubricating the brake rotor and pads.
Now hub motors aren't light and unsprung weight isn't great for maintaining traction in rocky terrain, so I've shed as much weight from the rear wheel as possible. The GMAC is relatively light weight, coming in at less than 4kg. To keep that weight down I've laced the motor with a Lightbicycle carbon 26" 40mm internal width rim, using 15g spokes, rolling on Maxxis 26x2.8" DHR2 tubeless tyres.
I've only just got the bike wired and running on the weekend, so there's a list of things still to get done, like fitting a front brake, wiring the PAS, fit dropper post etc, so this is how it looks at the moment.
So far the few test up and down the local street has been very promising, the Nuc 12F GMAC combo is super smooth and quite punchy at 2500 watts. I did have a slight brain fart during the build and forgot to secure the torque arm, hence the rejoined wires near the back axle and having to replace a hall sensor.
I did consider going with a 6 fet Nuc, but didn't want to regret not getting a the 12f for its ability to dish out more phase amps.
