Grin All-Axle connector re-design

offGridDownUnder · Sep 2, 2021

if there is a better place for this, please let me know.

I have two of the Grin Technology All-Axle motors, and I'm having problems with the cable outlet on one bicycle, which leads me to wonder why they designed it the way they did.

Both sides of the axle have static hubs which contact the bicycle frame and don't move in reference to it. Both sides then transition to the moving casing that contains the motor and flanges for the spokes, etc. One side has the mounting for the moving brake rotor, and the other mounts the torque arm that contacts the bicycle frame.

Why is the cable coming out millimetres from the spinning brake rotor, when it could instead come out, and be supported by, the torque arm? Perhaps even with a molded right-angle wire guide to contain the cables and remove all possible interference with the moving parts - as the torque arm must clear the spokes, so the cables can be routed the same way to guarantee that as well.

Grin themselves in their page suggests buying a brake rotor from them because "SOME 3RD PARTY ROTORS WILL DAMAGE CABLES!"

What haven't I thought of here?

ZeroEm · Sep 2, 2021

Justin wrote an article on the All-Axle hub motor. Had described the design issues encountered and the limitations, while trying to fix a larger bearing. I don't remember much now. I will try to find it and link it in and may help you. I don't have one so not much help there.

JackFlorey · Sep 2, 2021

sadhak said:
Why is the cable coming out millimetres from the spinning brake rotor, when it could instead come out, and be supported by, the torque arm?

?? The torque arm is removable on the All Axle. You can't have the cable come out of it.

The safest place (in terms of overall drive train interference) for the cable exit is the centerline of the axle. But on the All-Axle that wouldn't work either, since the axles are replaceable - and the axial design has problems with cable damage if the bike falls over.

There's no one perfect place for the cable to exit. Some are better than others; no one location will make everyone happy.

offGridDownUnder · Sep 2, 2021

JackFlorey said:
sadhak said:

Why is the cable coming out millimetres from the spinning brake rotor, when it could instead come out, and be supported by, the torque arm?

Click to expand...

?? The torque arm is removable on the All Axle. You can't have the cable come out of it.

I accept part of the idea you write, but I don't accept "can't". I do not see any reason the cable can't come out of the same side as the torque arm - it doesn't rotate with the wheel. I also don't see any reason there can't be 6 holes in the torque arm for the cable to pass through, or just 6 notches from the centre opening to which the cable can be laid to so the torque arm can mate in any of the 6 positions it could be fitted now.

I think it's a better idea, and can be done, and I'd prefer it, and I want to get feedback so Grin can consider it. Putting that cable millimetres from a spinning rotor does not seem like the best approach, and there is an unequivocal reason, I'd like to know it.

Perhaps they had the 'single-side' use case in mind? In that application, all three items must be on one side - cable, torque arm, and rotor. As I wrote in another thread, the thru-axle use case means the entire 20mm bore of the motor is off-limits, so no cable routing through the centre.

Looking at the page for the motor, I do see that the v1 motor had the cable exit on the torque arm side, and they moved it to the rotor side for single-side mounting (see the comparison table). So, Grin agreed the cable could come out of the torque arm side.

In that case, I'd prefer the cable exit radially from the 'rose' that provides the mechanical contact for the torque arm and the torque arm be relieved in between the lobes so that the cable could be drawn to the outside - in all cases being kept positively away from the spinning rotor.

That is an improvement I'd like to see.

ZeroEm · Sep 2, 2021

by sadhak » Sep 03 2021 12:28am

I accept part of the idea you write, but I don't accept "can't". I do not see any reason the cable can't come out of the same side as the torque arm - it doesn't rotate with the wheel. I also don't see any reason there can't be 6 holes in the torque arm for the cable to pass through, or just 6 notches from the centre opening to which the cable can be laid to so the torque arm can mate in any of the 6 positions it could be fitted now.

I think it's a better idea, and can be done, and I'd prefer it, and I want to get feedback so Grin can consider it. Putting that cable millimetres from a spinning rotor does not seem like the best approach, and there is an unequivocal reason, I'd like to know it.

Perhaps they had the 'single-side' use case in mind? In that application, all three items must be on one side - cable, torque arm, and rotor. As I wrote in another thread, the thru-axle use case means the entire 20mm bore of the motor is off-limits, so no cable routing through the centre.

Looking at the page for the motor, I do see that the v1 motor had the cable exit on the torque arm side, and they moved it to the rotor side for single-side mounting (see the comparison table). So, Grin agreed the cable could come out of the torque arm side.

In that case, I'd prefer the cable exit radially from the 'rose' that provides the mechanical contact for the torque arm and the torque arm be relieved in between the lobes so that the cable could be drawn to the outside - in all cases being kept positively away from the spinning rotor.

That is an improvement I'd like to see.

They run these motors on trikes where the cable and TA are on the same side. Ask Grin about that.

Grin All-Axle connector re-design

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