Thanks man 
Not sure, I forgot to weigh them before installing on my board 
the aluminium parts are pretty well optimized already, but the 90T gear feels heavy at the moment.
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Just for reference, here’s a great photo of the Kaly drive and how it uses what look like threaded spacers on the hub adapter plate to link wheel and gear motion
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Not seen those drives before, they look chonky, very cool! Similar principle to what I am doing with my wheel hub spacers.
This first prototype is relatively heavy at 1600g per pair (including everything), the production version will be around 1350g-1400g per pair, similar to Boardnamics’ M1 drive. I think they will be very hardwearing, can’t wait to thoroughly test them on my board. Here is a sneak peek of the production version with weight saving measures and other refinements:
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Update! Testing
I’ve put around 100 miles on the gear drives now and I’m happy with the performance 
I’ve been riding exclusively offroad down mountain bike trails and on grass. I’m really enjoying the torquey 5.29:1 gear ratio, I feel like I can bast up any hill and the top speed is high enough for me 
Compared to by belt drive board with 6374 motors this setup is quite bit louder, I think it’s mainly because the FlipSky 6384 motors are loud AF! When free rolling the gear drive is not very noisy considering the metal-on-metal contact of the gears meshing. I think I could make them smoother and quieter by increasing the gear helix angle for the next iteration.
I’ve been actively trying to break the gear drives to find any week points that I can improve for the next iteration. I’ve been jumping and keeping the throttle on, doing loads of full send accelerations and hard breaking, and deliberately landing hard when jumping. The gear drive itself has held up well to this abuse, it’s super sturdy.
However, I have managed to break the truck clamp, as you can see it’s started to come loose from the hanger. I think this happened because the fit onto the hanger was too loose, I designed a 0.1mm clearance fit, and thus all the force goes through the 4 grub screws. I think I underestimated how much force goes through the truck clamp, those motors are heavy and that results in lots of torque on the truck clamp when the motor is bouncing around whilst riding on rough terrain and jumping.
I think I can resolve this issue by using a double row of set screws, using lager M6 set screws instead of M5, and having more of transition fit with the hanger rather than a clearance fit.
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Nice work so far.
Tightening up that tolerance to .01-.02mm max, will work wonders over the additional set screws. A slight press fit is even better.
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Thanks mate 
I think a slight press fit is a good idea!
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Update! Prototype V2 – 3D printed mock up
I have been testing the first functional metal prototype on my mountain board for the past two months, I am really pleased with the performance. I’ve put the drives through some serious abuse! But they have proven to be very robust The only thing I manage to break is the truck clamp attachment, as described in my previous post.
Now the design concept is proven, it’s time to optimise the design and refine the product. The second prototype will have the following improvements:
- Weight reduction of 200g - reduced from 882g to 682g per drive unit
- Better ground clearance – overall drive width to be 4mm thinner and diameter reduced by 11.6mm
- Less grease required - the space between the casing a gear has been significantly reduced
- Improved truck camp - two rows of M6 grub screws and a tighter press fit on to the hanger
I’ve completed a mock up of the gear drive assembly using 3D printed parts and I’m happy with the design.
I will send the parts off to be CNC machined this week 
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What are you looking at for retail pricing? Or will you sell the files so we can get them machined ourselves?
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My plan is to keep testing the prototypes myself until I’ve ironed out all possible issues and weak points, hopefully Prototype V2 will be the last one before release 
Once I am happy with the quality of the design, I will do a beta release at a discounted price for people that want early access. I don’t want to put an exact figure on the pricing yet, as it depends on manufacturing batch size, but it will be competitive.
Who knows I might find that manufacturing and selling gear drives is a ball ache, if that happens I would consider selling the design files or open sourcing it.
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Update! Prototype V2 – CNC machined metal parts assembly
Sorry about the lack of activity on this thread, I’ve had the metal parts for a while now, but my day job has been pretty hectic over the past 4 months, so I’ve taken a break from eskate.
I’m really happy with the new truck clamp design, I think it should be much more robust compared to the 1st prototype. The press fit onto the truck hanger is tighter, it has two rows of grub screws, and the grub screws are larger M6 instead of M5. Here are some pictures of the finished part:
I’m very please with the machining quality and the black anodising turned out great. This prototype is functionally the same as V1, however a lot of effort went into saving weight whilst preserving durability. The design also changed slightly to retain grease close to the gear teeth and the drive is smaller compared prototype V1 for better ground clearance.
The weight of each drive is now down to 683g per drive which is 200g lighter compared to prototype V1, I could make the drive even lighter if I reduced the gear face width to 10mm instead of 15mm, but I don’t want to compromise the durability of the drives. My initial design goal was to produce a gear drive that is hard wearing and will hopefully outlast your board.
Over the next week I will be installing the gear drive on my board and completing some functional tests. I will put them through some thorough tests this winter with the aim of releasing the 1st batch to the public in spring.
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These are so pretty, I might just have to postpone my eMTB until spring. Really really pretty.
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Thanks mate really appreciate that! I do like how proto V2 turned out, the functional changes made it look nicer too 
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Update! Prototype V2 – Installation and testing
The installation for the gear drives was straightforward, it’s pretty much the same process as for prototype V1.
I’m happy to announce that the new truck camp design works wonderfully! Now the clamp has a tighter fit onto the hanger and an improved grub screw design, it’s rock solid even after lots of testing
One thing I noticed during testing was that these drives are noticeably quieter compared to protype V1, which is weird because the fundamental gear design hasn’t changed (helix angle, No. teeth, face width etc…). I think the weight saving measures and tighter spacing around gears has helped with noise. Here is a short video showing what they sound like, it’s mainly motor noise:
I’m pretty sure I have ironed out all the kinks in the design now, I haven’t found any faults whilst testing. Expect a pre-order campaign to drop relatively soon 
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any plans for straight cut gears and matrix III compatibility :))
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Yes As soon as I can get my hands on the MBS Matrix 3 trucks, I will design a truck clamp for it, they seem to be out of stock at the moment. I will also be supporting:
- Apex Air
- MSB Matrix 2
- Trampa CNC 19.5mm
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mbs Europe have a preorder on and i believe atbshop is due there delivery any day now.
whats the thickness of the drives?
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Thanks for the heads up, I will be keeping an eye out on ATB shop The design is well optimised in terms of thickness, I don’t think there is room for making them thinner without compromising on the gear face width of 15mm.
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TBF that’s pretty wide. IIRC the BNM1 is only ~10mm
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wide gears increase the life span before you need to replace them
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Exactly a key design goal of this design were gears that never need to be replaced. After completing my gear simulations 15mm face width seemed like the most robust option.
Boardnamics weigh in at 675g per drive my drives weigh in at 683g, so not much difference there even though my face width is 5mm wider.
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