Using a gasket between the motor and the motor mount seems to be a bad idea.
Firstly, you will thermal isolate the motor from the mount which takes away heat transfer from the motor to the mounting plate.
Secondly, even if the gasket is made out of a hard rubber or will soften over time or when the motor gets hot. If the motor position is designed to be variable, the motor will start to move and mess with the backlash.
9 Likes
The gasket could be a thermal pad 
2 Likes
Thermal pads are really bad at transmitting heat though. They are only used because something needs to be used for insulation and these are the ābestā choice for rough and/or uneven surfaces. But their thermal resistance is huge compared to direct metal-on-metal contact. Especially if a verrrry thin layer of thermal paste is used between the motor and mount.
7 Likes
Hmm. Good to know 
2 Likes
Spray the inside of the gear case with a thin rubberized coating so you can boast SilentMaxx technology 
3 Likes
Oring for the win, will seal it really well, while keeping most of the surface area
2 Likes
Thanks for the advice @glyphiks this is really helpful!
I have designed the truck camp so there isnāt loads of axel left, so you just use the standard axil nut. I will make 0.5mm wide PTFE shims to go in between the hub and the hub mount on the gear drive to cater for different hub thicknesses, the MBS Rockstar Pro hub needs 3mm of spacer in between the hub and gear drive hub mount when using the MBS Matrix II trucks.
I need to get my hands of on some Apex Air and Trampa trucks so I can design truck clamps for them, I will aim to design them in the same way, so you donāt need additional spacers.
I didnāt realise that some motors have circlips that are proud of the mounting surface! My Flipsky motors have the circlip recessed. I have modified my design to so that this will not be an issue for people anymore.
4 Likes
I am using angular contact ball bearings for the drive gear and the pinion gear will be attached to the motor shaft using the keyway and Loctite 638, I think this will be enough to cope with the axis force generated by the helical gears.
1 Like
Admittedly, Iām not sure about the motor gasket either, I think it might be a pain to adjust the pinion gear position with the gasket in place. And there could be issues with thermal conductivity and motor movement.
I think Iām just going to test how well it works on the first prototype, and if it causes issues remove it. Every other interface is well sealed, so it would be shame to not do anything here.
Iāve been looking at thermally conductive silicone gasket materials today, I might consider using that depending on how expensive it is.
1 Like
As @jack.luis said Iām using metal gears because I want them to last forever. Iām sure plastic gears are very quiet if designed correctly, but they are basically a sacrificial item, you will need to periodically replace them if you break teeth or they wear out, which is not an issue as they are much cheaper to manufacture.
I havenāt looked into 3D Servisas very much, Iāve seen people comment on how quite they are and they look well made. It seems their approach has been to go for big teeth and softer materials like plastic and aluminium. I notice they make their gears in-house, so I assume this must make them easier and cheaper to manufacture compared to steel module 1 gears. My design is quite flexible, so I might try out some plastic module 2 gears in the future.
Thanks for the advice everyone! I am taking it all onboard and tweaking my design now 
3 Likes
Iād recommend taking that one step further and making the hole in your motor mount plate larger than the pinion gear.
Iāve used the BN M1 drive and Moonās drive and one thing i really appreciated was that on Moonās you can disassemble the motor from the drive with only those 4 mounting bolts.
With how youāve got it designed, once you loctite on the pinon gear to the motor shaft, youāve now trapped your motor to your mount plate. If you assembled correctly, now you have to take a blowtorch (or similar) to the whole drive to get the pinion off and motor free.
If someone wants to do maintenance, swap gear ratios, disassemble for any reason, a large hole there makes things a lot easier.
One more general comment - i question the necessity of all your waterproofing efforts. Iām not sure this is actually a problem that needs solving. I defer to the more experienced off road guys here, but i havenāt heard a lot of chatter about mud filled drives or excessive wear/maintenance from water ingress. Typically itās the opposite - someone opens an āunprotectedā drive and it looks basically brand new.
Now, if you are convinced thatās an effort worth undertaking, youāve got to make some additional decisions.
- Most (all?) motors ppl are using arenāt watertight. The motor mount fasteners are a pt of ingress that render your motor gasket ineffective unless you add sealing washers under the fastener heads.
- Similarly your drive casing fasteners need sealing washers under the heads
- Those threaded holes in the mount plate canāt be thu holes bc again, youāve got multiple pts of ingress
- Same thing with your truck clamp - canāt have thru holes and need sealing washers
Etc etc
Recognize that youāre only halfway solving your intended issue. If i were you Iād reanalyze if thatās worth the cost and complexity.
One more -
I think itās a bit of a seductive trap to try to design a gear drive. It seems manageable and like a contained problem. Geartrains are one of the oldest mechanism in the book, and calculators are easy to find. After thatās itās just some quick ipad CAD right?
Whatās going to eat your lunch is testing and refinement. Thereās a reason Moon is on gen7 (8?) and the relatively newer BN AT drives continue to evolve. Reliability is fucking hard. I doubt most of the revs of the current drive offerings are bc of new features. If you can run some FEA & vibe analysis you get a jump start, but no one here has a sufficiently complex digital model of an esk8 with all itās loading scenarios.
How confident are you that this setup can handle the helix loads? How do you calculate expected noise? How are you handling backlash adjustment? (are slots enough?) Are 18deg mounting adjustment steps small enough? How are you managing the wildly large tolerances on the MBS trucks? The more trucks and hubs and gear ratios you support, the more configurations and features and compromises you need to make.
None of this is intended to discourage, just maybe try to simplify and set expectations for the road ahead
Ok, i swear this is the last -
If youāre going to the trouble of designing from scratch, brainstorm other ways to connect the wheels hubs to the drive than steel threads into aluminum holes. That just bothers my brain. Eventually, over enough miles, youāre going to have one wear on the other. Ideally you need something like threaded circular standoffs on the end of those fasteners. This way youād have aluminum slip-fit cylinders into the aluminum plate
7 Likes
I was hoping for something different.
4 Likes
Iāve seen metal break many times, just they donāt snapā¦
1 Like
Thatās a bloody good idea mate! Iāve now made a larger circular hole in the motor mount so you can remove the motor with even the largest pinion gear attached. I was thinking it would be a ball ache if the pinion prevented you from removing the motor from the housing, using a blowtorch to remove the pinon would be much easier if the motor is not suck in the motor drive.
I dont think water will get through the the cover gasket even if without sealing washers under the fastener heads.
You are right, if water gets into the motor, it could make its way through the screw threads and into the drive. But I think there would need to be a lot of water in the motors and require pressure (like being submerged in water).
I think the most likely place where water might leak in, is through the screw threads in the truck clamp, as you pointed out, I would consider putting some sealing washers around the fasteners there.
Where I live in the UK itās a wet sand muddy place, in winter our boards get caked in mud, I was thinking it would be nice to have gear drive that you can hose down without worrying about water going inside it.
It would be interesting to see if all the gaskets and additional shaft seals make a difference or not. I was thinking of building one drive with gasket and one without and then giving them a good spray down with a garden hose to see what happens.
Ahaha designing gear drive is a trap! I started off thinking it would be nice simple project to do over my Christmas break, and now Iāve put more hours than I would like to admit into this first CAD iteration. 
I realised that I need to do lots of testing and revisions before I have something that works well. Hats off to MOON for going through so many revisions and refining their product. I do kind of enjoy the challenge though, Iāve always got a project going on, so happy for that to be gear drive design for a while 
I did have some other ideas around the wheel hub connection, one of them involving slip fit cylinders rather than M4 bolt threads interfacing with gear drive hub mount.
5 Likes
Hmm one concern Iād have with a hole that massive is that when you receive impacts from the weight of the motor, there is a lot less meat there to prevent the case from bending
As someone who has destroyed a matrix 2 from jumping, I know a lot of force goes through that plate. Just something to think about. I imagine thats part of the reason the BN ones have a small hole. Maybe big enough for the circlip is the better idea
Thats actually not a problem I think, because the case will stiffen everythink up a ton. 
And those baseplates look quite meaty themselfes.
1 Like
If you did the stress analysis, Iād bet the meat equidistant from those 4 mounting holes has the least impact on strength. A little additional thickness elsewhere would easily reinforce the moment arm of the motors weight.
3 Likes
I mostly agree with your thoughts on waterproofing - itās probably not something to stress over. I spent a lot of time waterproofing my first two boards in practically every way you can - was mostly a waste of time, & I go thru puddles and ride in rain. Like, Iām happy itās done, but Iām not going to be as concerned in the future.
With regards to ingress from screw holes tho - butyl tape completely takes care of this. Very small blob of butyl tape on your screw, no water is getting past. It also somewhat acts as loctite does for mechanical retention.
That said, a small bead of butyl tape around the perimeter of the gear drive may work as well as a gasket would for those who want to be sure things are water tight. Scrape off the excess that gets pushed out on first assembly & aesthetically youād never know itās there.
But in the endā¦ if he has the means to easily make the gaskets, more power to him. I think from an outside perspective from somebody who isnāt part of our community it may be a minor selling point & a more refined looking product.
3 Likes
