Problems and Solutions…
- PROBLEM - Ground clearance, drive-deck interference, motor-baseplate clearance
Parts: BN Fixed Baseplate (40 deg) + BN M1 Gear Drives + 63XX Motors + Flat deck
The core problem with this combination is the mounting positions available for the gear drives in relation to the truck hanger. There are 15 mounting holes, at 360/15= 24 deg increments, but effectively you only have 2 (forward) mounting positions - drive close to deck (up), or drive close to ground (down), 24 degrees apart. As seen here:
With a flat deck and a short neck, the drive up position causes rubbing between the case and the deck when you start to turn (see black sharpie marks in later photos). It also causes issues with wire routing - if the enclosure is too close to the truck assembly, the phase wires hit the enclosure when you turn.
The drive down position does not give enough ground clearance between motor can and the ground, even with 110mm wheels - around 20.4mm measured.
On wire routing - There are 4 orientations for mounting the motors (up, down, backward, forward) in the BN Gear Drives, with no halfway rotation possible. With essentially no gap between hanger and motor (result of the very tight c-c distance in gear drives), orienting the motor phase wires backward/rearward is not possible. A ground-ward wire orientation would invite damage. That leaves upward towards the deck, or forward. On this board geometry, upward hits the deck in a turn, so forward is the only option. (One more thing to look for in choosing a deck I never expected).
- SOLUTION -
Attempt 1:
- Use ‘drive up’ position (solves ground clearance)
- Add riser pads as needed (solves deck & wire interference)
- Grind down baseplate (solves motor clearance).
Turns out “enough riser” is ~16mm. I printed 6mm rise pads in PLA for testing. I got to 3x pads before I had enough deck clearance. That was too tall for my taste and suboptimal, as it didn’t actually solve the core mounting problem, just acted as a band-aid workaround.
Grinding the baseplate is easy enough, but doesn’t inspire confidence. I also took off more than necessary.
All in all, not a great solution.
Attempt 2:
- New baseplate w/ smaller angle (solves all 3 issues)
Randal downhill 35 angle baseplate:
This potentially would’ve worked fine, with new Riptide pivot cups to tighten things up. However, I didn’t want to throw out the BN precision baseplate just yet, and I didn’t want to be forced into a 35 degree baseplate angle.
Attempt 3:
- Drill new mounting holes! (fix the core problem)
Per @b264 on ground clearance:
My experience is 8mm is “extremely ridiculously terrible” and 20mm is “not enough” and 30mm is barely enough to be comfortable but does work.
May as well optimize. Via the CAD model:
‘drive down’ position - 20.4mm clearance
12 deg rotation - 29.8mm clearance (+9.4)
15 deg towards deck - 32.1mm clearance (+11.7)
17 deg towards deck - 33.7mm clearance (+13.3)
19 deg towards deck - 35.2mm clearance (+14.8)
Designed and printed a drill guide for that 30mm clearance. Added 4 new holes to the existing 3 holes, at half increments (12 deg).
Upgraded to zinc plated steel screws and reassembled.
Right on the money.
3D files for anyone else to use:
BN Fixed Baseplate Riser - 6mm.step (25.2 KB)
Boardnamics M1 Drive_Drill Guide - 12 deg.step (71.5 KB)
Boardnamics M1 Drive - Rough Model - v4.step (3.1 MB)