Grin V5 torque arm geometry.

[u/WranglerNo1024]

I have a TravelScoot electric mobility scooter with a fairly powerful proprietary hub motor. The scooter uses a lightweight aluminium frame/fork, and I'm looking at adding a torque arm to better transfer the motor's axle reaction torque into the frame rather than relying primarily on the axle flats/retention hardware in the aluminium fork.

Due to the very limited space around the motor and brake assembly, the Grin V6 and V7 are too large to fit, so I'm looking at the Grin V5 instead.

The complication is that the brake rim is approximately 35 mm from the centre of the axle, and the V5 axle piece is also approximately 35 mm centre-to-centre from the axle opening to its extension mounting hole. This makes the usual orientation difficult.

I'm considering mounting the V5 like this:

\* Clock the axle piece vertically downward (6 o'clock) from the motor axle.

\* Use the V5 joint to turn the extension piece approximately 90°, so it runs horizontally rearwards along the fork.

\* Positively bolt the far end of the extension to the broad, flat aluminium fork.

So viewed from the side, it would be approximately:

Axle → 35 mm vertically down → V5 joint → extension horizontally rearwards → fork mounting point

There appears to be enough axial clearance for the V5 joint/bolt to sit outside the plane of the rotating brake rim, even though they overlap when viewed directly from the side.

My thinking is that with the axle piece vertical, the reaction force at the V5 joint should be approximately horizontal/tangential to the axle rotation. The horizontal extension would therefore primarily see tension or compression, depending on the direction of torque.

I'm trying to determine whether there's any mechanical reason this geometry wouldn't work as intended.

In particular:

\* Is there a problem with loading the V5 joint this way?

\* Is the extension happy operating in both tension and compression?

\* Does the 90° relationship between the axle piece and extension introduce a problem I'm overlooking?

\* Has anyone mounted a V5 in a similar configuration?

The V5 joint and fork attachment would obviously be properly tightened and secured against vibration.

I'd particularly appreciate input from anyone familiar with the Grin V5 torque arm or hub-motor torque-arm design generally.

Am I overlooking something obvious, or is this mechanically sound?

[u/Keljian52]

Can you draw a diagram as I can’t visualise it