I cut my own on a small CNC mill and a small manual lathe. I wrap the back in aluminum because Delrin laugh’s at threadlock.
My standard is 11 tooth. I can post all the files (somewhere) if you want to take a look.
in answer to your other questions:
How long has it been working? - I’ve got 3 boards, one is dual 6355’s and the single is a 6380 but was a 6375 most of its life. I’d say that on those boards the sprockets have been running for 2 summers.
How do you ride? agressive? moderate? - Moderate to easy. I used to be more moderate but after my last crash I’ve backed off a bit.
Ya got hills in your area? - I’ve done short hill climbs - steep ones with the dual motor but I’ve not done sustained hills often. I did a 26 mile run on the 6375 board, so I’m confident they’ll go the distance.
I don’t think you’re going to have any luck 3D printing sprockets - The #25 chain only allows for 0.120" teeth and I just don’t think anything additive is going to be strong enough at the teeth nor at the set screws.
Thanks for the info. I did´nt have any problems with drilling holes on my second sprocket from “gears and sprockets”. And the 25mm pre-drilled hole through the hub saved me a lot of time and trouble. Everything went fine…
My first wheel sprocket from “Conrad” was a b*#ch though. I wasted all my step up drill bits on that sprocket now I´m hoping that at least I can use it on plastics and wood…maybe even on some softer aluminium. I also killed a 3.5mm drill bit while drilling through that son of a b*#ch sprocket
Seems quite a bit of work…good results! I read through your thread - very impressive! Now that I have slept over the idea of printing plastic sprockets, I realised that I would be investing time again in something that is unnecessary. I have´nt got a chance to try out the new drive train. My board ist sitting there with full cells waiting to get man handled…but I have my duties first…pleasure and fun later!
So I´ll enjoy the rest of this summer with my new chain drive and possibly postpone making plastic sprockets for colder winter days.
So…this drive can take abuse! really heavy accelerations and braking and what can I say…I´m soooo glad I decided to switch to a chain drive.
Heres what I can definately say.
pros
absolutely no slipping
reliable power transfer from motor to chain to wheels and to the ground.
way less friction than a belt drive - easier to push when necessary (empty cells)
high pitch noise audible to pedestrians - they know your coming and get out of the way
uphill climbs are not limited by your belt anymore
cons
dirt collected on the chains after first ride with “Squirt” applied (no biggie - gotta observe how bad it gets)
noise - cops will notice you so be prepared for that. yes it´s loud.
The noise isn´t that bad. I noticed that pedestrians were not as annoyed compared with a belt drive. I don´t know why…maybe the high pitch reminds them of a high power vehicle and they automatically “respect” that and move to the side. That being said, I give them back the courtesy and pass them in a civilized manner meaning I slow down to a safe speed especially when I see kids. It makes accelerating even more impressive when you give them a good look at your board!
I’ve been using the 25H 14:27 Banggood chain and sprockets for over a year. Started out with belt but tired very fast of all the slipping. Bought a 10 tooth sprocket and, ofc, the acceleration improved and everything, but the noise increased dramatically. Ultimately, I went back to the 14 tooth to get rid of the noise. Now I have vesc heat troubles instead Looking for buying 12 tooth now
I also 3D printed the wheel sprocket in Nylon, 33 teeth. Nylon has lower surface friction than petg and is very durable. Ofc, the chain is not supposed to slide on the sprocket but still rubs against the sides occasionally. Used concentric setting with like 6 wall-layers. 0.1 layer height. Used a belt grinder afterwards to fix soft edges on the teeth. After 60+ km there is no sign of wear.
Had a bad accident this spring as I was accelerating up a hill and the motor sprocket suddenly came loose. Hard fall in 29,6 km/h so make sure that everything is tight and secure! Loctite is a must.
if you menage to drill the holes precisely they its totally worth it (maybe now they come pre drilled to fit flywheel cores)
its up to you if it will suck or not
My wheel sprocket has a 30mm hub. This is important because if you want to use this with flywheels then it´s very important that you work very precisely
First of all, make sure that your sprocket hub (if it has one) is 30mm in diameter. Life is easier if your sprocket does not have a hub (in which case you need a spacer according to your chains dimensions so you chain is not rubbing against the wheel).
The M4 holes (I used a 4.5mm drill bit) are touching the sprocket hub so there is not much space for mistakes. On top of that, you need to make sure that the holes are precisely 60° appart. BTW. this is the sprocket with an 8mm pre-bore that ruined my step-up drill bit. You can see my pathetic attempt documented in the pictures. The actual sprocket I´m using has a 25mm pre drilled hole in the hub - see in this picture I posted above.
Then you´ll need an adapter for the flywheel like this one.
When all is done correctly you should have a perfectly aligned wheel sprocket that is already correctly spaced
to accommodate the chain.
In the process of ordering parts, will update as I get farther along.
As a quick note, when searching for sprockets, ANSI naming convention for a #25, hubless, 30 tooth sprocket is 25A30. A #35, 15 tooth sprocket with a hub would be 35B15
Boring out a sprocket is going to be quite difficult without just a hand drill, but I think I can 3d print a jig that will make it possible by drilling 16x 1/4" holes. That’s going to be fun…
Going to go with 9:27, a little worried about noise and ground clearance, but we will have to see. Could go with a lower Kv motor which would help with both of those issues, but would reduce max torque by about 12%. Nah…
You could reconnect the spools in the motor to a star configuration instead of the original delta configuration. This will lower the kv-rating with a 1.73 factor. I did that to my SK3 motor, reducing the kv from 245 to 142. Took a few hours but its an easy mod.
If you take two otherwise identical motors just with different Kvs (achieved by turn count, not winding configuration), and you gear them to the same top speed, they will produce the same torque. The lower Kv motor will just waste more electrical energy as heat since it will have more turns and thinner wire.
Interesting idea with that re-wind. What are the disadvantages of going star?
Looking for buying 12 tooth now 
