Compact Electric Skateboard questions

I’m pretty experienced in the quad industry, that’s actually where I got the idea to do it this way in the first place, as re-purposing the motors designed for ~300-400mm sized racing quads would give me four 500-550 watt motors for under $15 a pop, and escs rated for continuous draw of 60 amps on 4-5s lipo, with active braking (albeit not regenerative) for about the same (the ones I’m currently looking at cost $17 each). making motor mounts isn’t a huge issue, I’ve got access to a couple 3-axis cnc mills through the university, and they have a 6-axis arriving in about a month. also, if people on here are working on custom motor controllers (just started reading up on the vesc), you should look at some of the custom firmwares for multirotor escs, like blheli or simonk, along with oneshot. Most people building multirotors these days are running escs with 499hz tick rate, which allows for incredibly smooth and low-latency control of the motors. The only thing I can really see that I lose by going with multirotor hardware is regenerative braking… I don’t know much about it but anyone have rough figures of the percentage of the range you can generally expect to gain by having regenerative braking?

Regen braking won’t make a huge difference, and I definitely wouldn’t worry over it. It’s a ‘nice to have’ but no where near a ‘need to have’

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Thanks so much for all the responses guys, really looking forward to this project and already loving this community finished a rough part-out of the electronics and so far it’s coming out to around $170 for four 28-15 400kv 500-550W motors, four 60 amps escs that I’ll be writing a custom firmware for based on the blheli source code, but adding active braking, a gt-2b that I’ll be doing darkwolf’s mod on, and two 5s 4ah packs that I’ll be splitting up and soldering into a custom pack to fit within the housing.

Bonus, I got a bit bored in my cad lecture today so here’s a few more concept renders in alternate materials.

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sounds like you got it all figured out. cant wait to see your results!

I like that your thinking outside the box, we need more people willing to try new concepts and considering the reasonably low cost you mentioned for the motors & ESC it seems like a viable project… also your area of expertise is using those smaller components, so you will be able to effectively gauge how they perform and make educated decisions better than others who don’t have the knowledge!

I would suggest 3mm pitch belts, near 5;1 reduction ratios… the belts will need to be 15mm wide.

Drivetrain something like: 12T motor pulley 60T wheel pulley 83mm Wheel 500kv 15volts

= 7400rpm 23km/h

I suppose this all depends on how fast you want to go? 23km/h is fairly slow. Maybe need 6S batteries.

It should have impressive torque whilst running at fairly high RPM and hopefully with the high reduction ratios with less load on the motors overheating will be minimized.

Thanks so much. Since I’ve gotten most of my experience from aircraft power systems the reduction ratios and belt drive systems are where I lack knowledge, and you’ve literally just given me all the information i had been trying to figure out in one post. not really looking to go much faster than that, 23km/h is about the fastest I’d want to go on this thing, at least at first. it’s a 24" deck after all. and the low speed with ~2kw of power should be really nice for climbing hills too. I’m gonna order the parts in a couple days, and I’ll start posting pics of the build as it progresses. thanks for all the help everyone!

Can you list exactly which parts you are using? I love howmuch you can do on the quadrocopers now. With the naze 32 the possibilities are endless. It’s kind of like what the vesc has done for our community.

also you might want to read this

This could be a really cool build. If this sort of mini board is feasible for (what seems to be) a really reasonable price compared to the longboards all of us are using, everyone would want to have one to keep in their trunk, dorm room, office, etc.

They would be light, cheap and they don’t need to be crazy fast (in fact going fast on a Penny is terrifying) so they really make a lot of sense.

I was originally thinking that this was a perfect case for hubmotors (or maybe just one hub motor) but maybe this way could be even better. Looking forward to seeing it.

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Also, if you use really small motors, that also means the wheel diameter can be much smaller so the total weight goes down as a result, big wheels are heavy, also you get more torque too.

Its packing over 2000 watts of motors onto an 18 volt, 8ah lipo penny board. we’re looking at what… 144ish watthours … what kind of range were you expecting? With a top speed of 14mph it seems like a 150 lb man might get about 4-7 miles out of it if you kept it around 10mph? a little kid could probably haul ass on this thing half the day.

seems like the ideal board for dicking around in the park or letting your kids ride around with you. and it probably won’t take long to charge, either. This has a ton of potential and i might buy one if they go to market.

I wonder how this would effect the weight to power ratio. This allows you to have a relatively small low voltage battery but still get some decent speed with the high kv motors which leads to a small light board, however you would have to add the weight and space(not really that much) for 4 escs and the 4 motor mounts which if you make the mounts light and small this difference would be almost eliminated. I might have to try and take the plunge as well this is an interesting idea that inwould like to try. I think chaka and a few others touched on in the 4wd electric skateboards thread (didn’t have any full blown designs like here). If I do build one I might yolo it and hook up the space cell. EAT MY DUST!!!

I’d be careful hooking up a space cell, the small, relatively high kv motors are usually not intended for more than 4-5s, maybe 6s lipo.

yep, current design is for 60mm wheels.

depends on the final charging setup. If I try to have a charger built into the board it would have to be a small, probably <1A charger, so charge times would not be great, but that would allow a really simple system of just plugging in a dc power supply. if I use a proper external li-po charger, it could be charged in under two hours without wearing down the battery.

cost of the one-off (not including labor of course) looks like it’ll come in under $350, so if that works out and we can set up an effective way of producing them in decent quantities, and therefore buying components in bulk (currently hoping if the prototype works well to take it to kickstarter sometime in 2016) we could probably have commercial versions going for between $300 and $450 while still turning around enough profit to make it commercially viable.

I share your desire for a small and light board. I am currently using a ~30 inch board with a single motor and dual batteries.

The one question I didn’t see by skimming through the posts was what kind of range and top speed you expect?

The idea of fitting as much as I can into the least space possible has lead to towards the VESC and Hub motors.

I am studying computer science, not design or engineering, and thus, I have little CAD. And that is my limiting factor, but I see the concept of build a board, slightly thinker, with the components inside of the board rather than in a compartment under it. Then, 3d printing such board.

Any news on this one? How has it progressed?

i’m interested in how this turned out. You there @PennE?

If I had the tools to make a board, I’d go for the design like bolt motion, which has a super cool look imo.

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Quick update since I’ve ignored this thread a long time: project is currently sidelined due to discovering some inherent issues with the high kv motors, namely their lack of torque. They can maintain solid speeds (23-25mph) but acceleration is practically non-existent due to lack of torque, and maximum hill grade was 4-5% before the motors were just stalling out. wouldn’t recommend this setup.

mh so 400kv is way too up in the sky… 300kv is what is the highest here, I think…

270-300kv.