First of all I want to thank all forum members for the big inspiration and great support, I love this place!
This is my third build and I’m an esk8 addict. 2 years ago I started with the intention to build a cheap longboard but ended up with 3 builds so far…
The evolution of the MountainFOCer (now called dirt machine)
I built version 1 of the MountainFOCer last summer and actually are working on V2. I describe here what I’ve done so far plus what I’ve changed and why. Also about real life experiences with the setups and more. For V2 there will be updates from time to time, so stay tuned.
V1 setup: trampa holypro deck 16ply | vertigo trucks 136kv 6364 sensored trampa motors trampa urban mounts dual esk8 4.12 controller DIY enclosure 10s 10Ah Turnigy Graphene Lipo bypassed 10s BMS for charging 8” trampa treads (hard compound) on superstar hubs 14T / 66T pulleys anti-spark switch with fuse
Range: max. 23 km / 14 miles Length of cables from battery to capacitors: 28 cm / 11 inch Length of phase and sensor wires: about 85 cm / 33.5 inch
But now some general details about this build and V1:
First thing I did is to get rid of all bling bling parts because I don’t like it shiny, it must be black. I went to a local shop for black anodizing and love the result.
The Trampa motors also got a special treatment with carbon foil, black bolts and black metal mesh against debris.
The urban mounts are sturdy and the grub screws keep tight. I like the look more than the pro mount but the disadvantage of an open belt system is that all that debris enters the drive system. I damaged some belts so far due to stones between belt and pulleys or by hitting the ground with belt/wheel pulley.
I tried idler pulleys on the slack line and it worked well but the tiny M4 bolts get loose and bend quickly, changed to M5 bolts but am not happy with the durability so I dismounted it. The motor mount is long enough (axle to axle distance) for most cases, but on hard braking the belt can skip, I like to have the belts quite loose.
The enclosure was bent from an 0.5mm steel sheet and was a lot of work but it did the job. Bottom and top are 4mm plywood. I would use 0.8mm -1.2mm aluminium sheet if I would do it again. The goal was to have battery and Vescs in one box in the middle of the deck which I like more than the look of 2 boxes. In the end I changed my mind because it was impossible to swap or change batteries with this setup.
Outside I put carbon foil and inside some pieces of foil I had to insulate the metal.
A short story about my vesc disaster. I started with 2x flier V4.12 but the hall sensor ports were not working so I switched to 2x Maytech V4.12. I realized that BLDC hybrid mode didn’t help with cogging at all, just a better control at low speed, that’s it, but feels like unsensored. After many different trials I knew FOC would be the only solution in my case. Bad that Maytech don’t run in FOC that’s why I ordered 2x esk8 4.12 controllerand finally it performed as I wanted, smooth startup without any cogging! Well, because I work on 2 builds (the Urban FOCer is not finished yet), I needed another 2 vescs for use in FOC, so I ordered 2x esk8 controller 1.1.
That should be enough vescs for a long time and I was totally broke. 2 weeks later my MTB didn’t run anymore and I was sure that I fried the vescs. That’s why I begged Frank to sell me 2x VESC 6 for a discounted price, what he fortunately did. 2 days later I realized that a solder joint of a phase wire was disconnected (couldn’t see it through the wire mesh) so all good, after resoldering everything was working again. Because of VESC 6 I sold all V4.12’s I had, only kept the esk8 1.1 controller for the Urban FOCer.
I started with 10s 10Ah Turnigy Graphenes (6s+4s in series) with bypassed BMS for charging only in combination with a 42V Li-ion 3A charger. Placed in a Lipo safe bag with some foam and wrapped in fabric tape.
Everything was working well until the day I forgot to switch off the board after a full discharge, 28 hours later the cell voltage was 0.887V. One more reason for V2 and upgrade to 12s…
As remote I have the steez but had some problems with scary dropouts in the beginning. The receiver was too close to the metal and after reposition the issue was gone.
I use motorcycle 5g adhesive lead weights against valve/wheel wobble and it works really nice , big up @whitepony AFAIK the first who tried this technique on MTB hubs. It is a big difference. After 600km some weights are missing, in the future I’ll take pictures of all wheels so I know where to add missing weights without balancing again.
First I used the 15T pulleys but after a couple times of reassembling the grub screws were stripped and got stuck. Thread locker on the grub screws was not enough, it came loose very often because of the play of key and keyway. I ended up with using a special non-permanent thread locker for shafts for the new 14T pulleys. I put plenty of it on the motor shaft and key and since a few hundred kilometers it holds up very well. It’s ridiculously cheap, both thread lockers are from hobbyking.
EDIT: This HK thread lockers are too strong, it needed heat to remove the pulleys, I switched to the genuine Loctite.
I use the 8” trampa treads in hard compound. Because of more tear on the rear tires I swapped the rear and front tires after 300km (186 miles) and had another 300km. In future I’ll wait until the rear tires are worn out, then replace the 2 and the next time all 4 and so on, less work.
What really sucks is a puncture, I had 5 within 600 km (373 miles). The tires had no visible damage and there were no stones inside the tire, no idea why this happened. I fixed the tubes with bicycle repair kit and they last so far.
I love the fact that I can ride without taking care of the battery and electronics, for MTB top mounting is a must IMO, it’s ugly but rocks! Here you see what happened to my nice Trampa sticker and why I enjoy top mounting
One Video tells more than 1000 words and pictures, so I uploaded this video for comparison of bldc and FOC mode. In the beginning you can see the annoying performance at startup with hybrid BLDC. Sorry for the length of this video, better skip sometimes
Meanwhile I’m working on the second (and hopefully last) version of the MountainFOCer and will post some more details soon.
Changes in V2: dual VESC 6 E-Toxx direct drive separate DIY box for electronics at the tail of the deck 12s bestech BMS for discharge/charge 12s 8Ah Lipo (+ 12s5p 15,6Ah Li-ion) Peli case for swappable Batteries direct fet anti-spark switch