DougM's latest build - Sand Runner

So the other weekend I took the mountain board out on the beach here in Washington state (Long Beach if you happen to be local). The nice thing about this beach is that cars are allowed to drive on it, so nobody even notices if you’re racing up the beach on a skateboard (actually a lot of people noticed, but in a good way)

The downside to the mountainboard is the motors are not sealed, it’s chain drive and the wheels are 8" but way too skinny to be of much use in sand. It worked, but it took a lot of battery to keep going. Also, by the time I got done riding it was starting to sound funny, so we’ll see how much damage I did :slight_smile:

Anyway, it was enough fun that I’m going to build a task specific board - a sand runner (caveat, wet sand). It will need to have large diameter wide but lightweight wheels, sealed gearboxes and some sort of covers for the motors. Basically the whole thing has to be sand-proofed.

This is currently in the planning stages, but I have started to assemble some parts.

MBS Trucks

Ali Express Kayak carrier wheels

I’ll be running 10S5P of 4k Ah 2170’s and, unfortunately due to budgetary constraints (and because you can’t get FOCBox Unity’s anymore) will be running some old VESC 4.12’s driving 6374’s that I have kicking around.

This is going to be physically a much longer board than your usual longboard - I’m thinking 4 1/2 feet long. The trucks are 16" wide so should piece together pretty nicely.

If you have a line on a design for a gearbox that can be configured for 10" wheels please let me know. Otherwise I’ll have to design the thing myself which presents a few challenges.

Anyway, I’ll keep this thread alive as I build it up, but it’ll be a slow build.

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You need to check out what @kaly has got going on, probably one of the best setups i’ve seen personally.


Check out Etoxx maxi gear drive from @Nowind

Would work with 10“ wheels too and you get a better gear ratio for that big tires. The kaly drives only come with 1/4 gearing.

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Interesting wheel choice… Can you seat a bearing in those or are you planning something more custom?

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Thanks for the feedback, but I can’t afford to buy a transmission. I’m going to build my own :slight_smile: I know what you’re thinking, and you’re right, but I have a little bit of an advantage. For a project along time ago - so long that I don’t remember what the project was, I built a gear cutter.

I spent the last couple of nights trying to figure out exactly what I was thinking when I built it, fixing some obvious weaknesses and getting it back up and running again, but last night I was successfully able to cut a test gear.

These are straight cut, not helical, so they’ll be a bit more whiney, but they’ll do the job. I’m thinking 20:125 which is 1:6.25 (same as the E-Toxx!) - I used the eskate calculator which thinks I’ll get about 30mph. Now, I chose this ratio because back when I made the gear cutter originally I cut a set of brass gears just for showoff and they are 20t (24 pitch) gears - so I plan to use them as the drive gears.

If it turns out that a 20 tooth gear is too big I will make some smaller ones. Brass obviously is a bit trickier than Delrin but the machine is up to it if I take several passes.

As to the transmission I’ve started working on the model, but I’ve got a long ways to go and there are way too many unknowns. I at least have to wait until the MBS trucks get here so I know what the mount will look like, but I think they arrive tomorrow.

@RyEnd in answer to your questions yes, the 10" wheels are a total mystery. It’s possible that they’ll be really good but it’s also possible they’ll be total junk. There were about 5 vendors all of whom showed the same picture but with dramatically different prices, so I just chose the cheapest.

The two mysteries are how to install bearings, which hopefully is just a matter of turning some properly sized inserts, but also how to interface the driven gear with the wheel. I won’t really know either of those until they get here, which isn’t for a month unfortunately. But I’ve got a lot of evenings to go in design and assembly of the transmission.


Awesome setup! following!~

Found some candidate bearings: The 60-78-10 for the outside and the 40-52-7 for the inside, but that depends wholly on the outside size of the truck arms, which I’ll know tomorrow.

In the meantime I did some best guess dimensioning on the housing

you built a 3-axis CNC mill and you can’t remember why… lol!

I can only imagine you must have some other really interesting stuff in your workshop/life to cause this forgetfulness… or perhaps Retrograde amnesia?

Or early onset Alzheimers :slight_smile: I have a lot of projects. I remember that this was for either a transmission or a transfer case and I definitely remember that it was a total failure. But a really cool one. I’ve been meaning to get back to that machine for a long time.

I’m going to move this build over to

Hope to see you there.


pretty much everyone is over there