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Horská doska - Dougie's mountain board build

So in the past I’ve been very bad about documenting any of my builds, so this time I thought I’d start with the documentation in the hopes that while I build it I won’t have any excuse not to put down the details here while it is in progress.

The board will be a dual motor mountain board. In my inexplicable tradition of giving all my boards Slavic names I’ve chosen horská doska, roughly translated from Slovak as Mountain Board.

The budget is about $100 per month, plus the occasional splurge. So it’ll likely take me until next summer to get all the pieces.

The design I’ve been using in the past, extruded rail drop decks, has worked really well and this one will be the same. I will spend some time rendering it in Solidworks so will post renderings here.

  1. batteries will be 10S6P of the new 4kAh Sanyo 20700’s. While these will give me epic range, they are only 15A batteries so the 6P will give me 90 Amps, which seems to be a pretty good budget for a dual motor (45A per motor) https://liionwholesale.com/pages/search-results-page?q=sanyoncr20700b I spent this month’s budget on the first 12 of these.

I thought about making a carbon fiber frame, but with such a ridiculously heavy pack and 2 motors there isn’t really any point in trying to shave weight.

Wheels will be 6" pneumatics. I’m currently thinking about converting Evolve’s conversion kit: https://evolveskateboardsusa.com/collections/gt-carbon-parts/products/gt-series-all-terrain-conversion-kit#tab3

Probably, since I want this to be a super-reliable board, I’ll steal the VESC6 out of the WidowMaker (which used to have a slavic name before it tried to kill me) and get another VESC6. Or B) if the dual FOCBox comes out in time I might get one of those.

This opens up the possibility of turning Widowmaker into a dual 5065 using 2 VESC4.12’s.

I really want to play with the flexboardz suspension, but I don’t have sufficiently detailed drawings or models to reproduce one, so that would be a big experiment. Failing that I’ll just go with mountainboard trucks.

I’ve been looking for another Tacon Bigfoot 160 to use in this build, but you can’t seem to get them anymore. So I’ll probably go with the 6355’s that I put on my first dual motor build. products/electric-skateboard-motor-6355-190kv These are sensored, which is probably better anyway.

I’m also going to try for direct drive. Years ago I made a gearcutter, so I guess I’ll have to dust it off and try to remember how it works.

There are some great projects for remotes going right now, so by spring I expect there to be some great new products (or DIY’s) available, so that’ll be the last thing on my list.

More to come!

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dont go evolve at kit, go w/ psychotiller wheels. i have the at kit its been a pain w/ the 6355 and cutting shafts ect…

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I can vouch for the psychotiller wheels they are awesome. I’m riding my Raptor 2 right now and it feels sketchy I’m already used to Pnumatics lol

Thanks for the guidance - I was trying to save a bit of dosh, but I definitely don’t want to muck around with having to re-machine the wheels.

Expensive but worth it for wheels. 6355 are great motors also just got me a new set same ones. I used liion for my cells I hear imr cheaper.

I cadded up the frame tonight - just so you can see what the thing will look like.

Trucks are off GrabCAD and are just temporary. I need to fit the batteries next to determine the rail width.

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The first 12 20700’s have arrived :slight_smile:

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I started working on the FlexBoardZ replica suspension but didn’t get very far.

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Mostly because I got distracted by a taillight.

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I have a trip coming up on a newly paved road called the Middle Fork Road. It’s long and windy and beautiful, but it has no painted lines and there is vehicular traffic on it. So I decided a hi-vis vest and a really bright taillight was in order.

image (proving once again that digital cameras and LEDs don’t match - it’s red)

There’s not much interesting about taillights (this one is 3D printed out of clear PLA) except that there are these incredibly bright LEDs called Luxeon Z’s. They are tiny and put out an incredible amount of light using a very small amount of electricity. I’m pretty sure most cop lights use Luxeon Z’s.

Luxeon Z Digi-Key

I use 18 in series with an 80 ohm current limit resistor. It’s tied into the anti-spark switch, so gets the full 10s pack voltage.

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Ok, based purely on looking at pictures of this type of suspension I found on the interwebs here’s what I think it will go together like

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I’m still missing the lower links, but a beer and a burger are calling my name.

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I 3D printed the mount block last night for test fit. It looks really nice but I don’t think I’m going to be able to use that design.

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I spent some time last night puzzling over how to attach it to my frame, and while I could attach it to the same mounts I usually attach the trucks to this seems like a hack. I’m going to spend some time braining up a more integrated attachment. I think I can integrate the lower links nicely into a slightly modified version of the drop plates I’m currently using.

Next up is ordering some aluminum extrusion to make the cross bar. Ironically OnlineMetals is local to me. I’m going to pick up 1 inch and 1 1/4 inch

I also need to find some ball joints for the lower links. McMaster 2458K32 look good on first blush

Also it seems prudent to get some UHMW sheet with adhesive on one side so I get nice smooth action between the parts. Probably McMaster 1441T91

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Made a little bit of progress on the trailing arms

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and mounting the thing to the frame

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Probably those plates don’t need to be so long - that’s kind of a relic of the previous design. But then again it’d be nice to have someplace to put all the electronics. I could see tucking a little box up in there with a couple of FOC’s.

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Metal has arrived :slight_smile:

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Got a small windfall from a computer job so I put in my order for Psychotiller pneumies. Very likely they’ll get tested out on Farkassem, (the dual motor board), before they go onto this one. Unless the trucks aren’t wide enough.

I tried to ride in Bend, Or, but the trail out of the park was cobblestone and then turned to gravel. So I didn’t get very far. Sunriver has 26 miles (!) of curvy, hilly, smooth beautiful trails, but they don’t allow skateboarding, wah wah.

The first trailing arm is complete(ish). Clearly I forgot to think about wire routing but that’s an easy fix.

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I really need the Psychotiller pneumies to come in so I can test-fit everything and figure out how long of an 8mm bolt I need to order.

In the meantime I’ll work on the cross-brace. But I need some 1.5" 6061 round stock which I don’t have, so I’ll have to wait for another order. Which is ok, I only have today and the anti-spark switch on Widowmaker has failed on (which I guess is better than failing off) which makes me cranky.

Update: the anti-spark switch problem turned out to be a loose wire. Perhaps using screwterms in a high-vibration environment was another of my not-so-bright ideas :slight_smile: In any event, screwed the wire back in and Widowmaker is back on the road.

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This looks awesome man! Looking firward to watching the progress of this build. I’m using 20650’s for my current build. Lg’s, but for different reasons. They are legit 30 amp discharge so I’m using them for a smaller pack. Keep the awesomeness coming!

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I just also put in an order for another 24 20700’s. That gives me 6S in case I want to do some test riding before I can afford the rest of the batteries.

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Mmmm, shiny things…

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I know all y’all have been wanting to ask me, “but Doug, what happens if the material you designed to isn’t the same as the material you ordered?”

Well, I’ll tell you…

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THE PARTS DON’T FIT! :slightly_frowning_face:

Turns out this is kind of a fortuitous mistake, though, because the wider box channel means I don’t have to mill out the other side of the cross-brace which will make it considerably stronger.

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I am so following this!!! Good to see more swing arm designs coming out! If this works will you consider posting the cad files so people can make their own?

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@High-roller - Absolutely. I’d love to see people improve on the design. I will post the files once I know that the thing actually works. It’s completely designed based on pictures I found on the Google. There aren’t any documented swing-arm builds out there that I could find.

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