Project ThunderCat: Catrike Expedition w/Grin All Axle

[colsaunders2]

I've wanted to put dual hub motors on a recumbent trike ever since Grin announced the single-sided All Axle and I read ecat's build thread. It's a pricey undertaking so I decided to split this project into 2 phases: (1) try a single front motor, then (2) buy a second if it works out.

Phase I is complete, using this pre-2013 Catrike Expedition as a host. I installed the GAA on the left side along with a CA3 and tucked a Phaserunner V6 under the seat.


Now you are probably thinking, "how the heck does that handle?!" Surprisingly well. You can feel the motor pulling during acceleration or braking but it doesn't cause the trike to veer much,as the other wheel pulls it back to center. The standard wind (6T) All-Axle has sufficient torque to squeal the tire when applying full power from a stop; 20" really is the sweet spot for a direct-drive hub motor. I'm watching the left spindle carefully for any signs of play; this was an issue on ecat's trike.

I carried over my 52v 18ah battery with Molicel P45s from Bicycle Motor Works and get ~ 50 miles per charge with a top speed of 28 mph and generous throttle use. The pack fits right into the cruciform. If I feel like wrestling the cranks, I'll swap in an ERider T9 torque sensor. Before moving onto Phase II I need to tame the bumps - the previous owner installed a skinny 700c wheel but that's not gonna cut it for ThunderCat. I think a proper 26" wheel with a Big Ben tire will help.

 

[neptronix]

Nice ride!

26 x 2.6" Schwalbe pick up would be fun at reduced PSI if it fits!

 

[colsaunders2]

Grin warns that the single-sided kits aren't necessarily drop-in and they are correct. The torque arm bolts were too short (maybe meant for a different version of the adapter) so I'm getting longer ones. Had a nice chat with Miguel and "The" Justin about this, QR skewer weirdness, and some possible updates which I may have volunteered to test

Also I hate IS brake mounts with a passion. The Avid BB7s were fine with stock wheels, but once you add in the torque arm some disc rub is inevitable - can't adjust the caliper inward. Are thinner PM adapters a thing? Even 1mm less would help.

While the motor is secured to the spindle via the brake mount, it's still meant to use the QR axle skewer. I can clamp it semi-tight and all is fine, but if I crank it down the motor gets pushed into the caliper Grin's axle adapter/end piece is likely designed for newer Catrikes as I can't even get the skewer tight enough to close. Anyone have a post-2013 Catrike who would be willing to take some measurements?

Nice ride!

26 x 2.6" Schwalbe pick up would be fun at reduced PSI if it fits!

I considered the Super Moto X but the reddit-sphere is reporting 2.15" as the max clearance. Thinking an MTX33 rim (26mm internal) with the Big Ben Plus 2.15 will allow for max air volume within these constraints.

 

[G8trwood]

How is the motor at slower speeds like maneuvering around obstacles, or do you, cough, pedal then

 

[colsaunders2]

How is the motor at slower speeds like maneuvering around obstacles, or do you, cough, pedal then

The motor itself is very responsive, 85 Nm of torque from a stop. If anything the limiting factor is the trike. It'll never be as nimble as a diamond frame bike.