Major Update: Commuter Booster - Proto #2
Amazing what you can get done, when you find a spare 4 hours to work in the shed.
Behold Commuter Booster - Prototype #2
- Turnigy 6374-200
- single swing arm design
- easily adjustable (spring preload, engage deadstop, and disengage deadstop)
- suits 34.9mm seat-tube.
- weighs in at 1.2kg, 0.9kg of which is the motor itself. Not bad since I have made no effort to shave weight down.
Really happy with how this one has come together.
The single swing arm is defintely stiff enough, and the motor has a skirt bearing so no stress issues.
The deadstops are adjust via two M4 screws. So it is ultra easy to adjust how far the motor sits from the tyre, and limit how much it will rotate in to the tyre as well. So it will be really easy to tweak the amount of engagement to minimise losses. I will need some method of locking them in place once adjustment is done. i.e. lock nut. And I will probably add some rubber to soften the blow when it hits the deadstops.
I have also made the spring that takes the weight of the motor easily adjsutable too. So this will allow for more subtle tuning of the drive engagement. All you have to do is rotate that little collar that retains one end of the spring, then tighten the grub screw. (Note that little collar comes with the motor)
Here is a pic showing all the parts that make up the drive. On the left is the fasteners, in the centre the custom parts, and on the right the parts required from hobbyking. A total of 7 parts (4 custom, one modified), plus 10 fasteners (6 new, 4 came with the motor).
Definitely happy with that. Can't see any way to reduce that while keeping the level of adjustment I have.
The custom parts:
- The main clamp/pivot block. Made from Acetal with a drill press, hole saw, various drill bits, M4,M5 & M6 taps, and a dremel. Size and shape is still totally un-optimised. I just used the blocks that I had laying around.
- The swing arm. Made from aluminium with an angle grinder to cut to size, drill bits, & M4 tap. (Note the centre clearance hole is too big as this was originally a right hand swing arm that took a bearing.)
- A spring. Repurposed from an extension spring using a dremel to cut to size, then lots of swearing to bend it into the shape I needed.
2x M6 screws to clamp it to the seat tube
2x M5 screws for the dead stop adjustment
1x M4 screw which is what the adjustment screws act on
1x M4 grub screw to lock the shaft to the swing arm (should probably have two)
The OEM parts
1x $60 Turnigy 6374-200
1x $8 Turnigy AerodriveXp 63-74 SK Series Shaft
Now I just need a chain ring, and brakes on the Avanti then I can mount it up and give it a run.