The Racers Room


I’m just going to lightly chime in… because it really means nothing.

But at 50battery amps per ESC on 13S, so around 4600-5400watts total) Ican sustain 29-31mph up 16-20% varying grade hill for about 3 miles, then it starts thermal throttling. But I’m also only 130lbs…

Not sure how long your runs are. Or your weight… But I’d likely agree with you if we’re talking focbox without external cooling. A couple factors I think that play into this is High P groups or a battery with high enough discharge/low enough IR that the sag is kept to a minimum. So that the amps don’t skyrocket from voltage sag…as well as the already high voltage, keeping the current lower.

3.8 miles is the longest DH run I know of around here…and I can only make it up just over 3 before my speed starts to get limited to around 23~mph from thermal… I’ve been considering adding exposed sinks so that I never run into thermal throttling…even though it is already a rare case for me…

Your setup is drastically different however… Especially your KV range. So it is unfamiliar territory for me to comment on…


The simplest solution is usually the best. And to me, that’s 4wd instead of 2wd if heat is an issue. Getting a big heat sink exposed seems problematic to me. More can go wrong there then just adding 2 motor esc’s and motors.


Not sure how more can go wrong…

I’m going to cut rectangles into the enclosure. Then mount a thin alu plate inside and seal it. Then screw these in from the inside(sink below outside) to pull the the focbox mounting plate and the sink together to clamp the enclosure and hold the gasket sealed.

s-l400 (3)s-l400 (2)

Focboxes are at the very back of my enclosure and these sinks aren’t lower then the motors and would only be a couple inches before the motors…so likely won’t strike for my riding style. I avoid curbs, humps ect…


needs sealing then. high heat sealing. Other wise, moisture can get inside.


Ya. Simple. :wink:


Still think more motors are simpler personally, lol. Or at least, better on the electronics. Spread the heat out between more vesc’s instead of trying to essentially overclock 2.


Overclock? If your keeping it cool and it’s operating within specs of the fets. I don’t see how it’s overclocking…as the stmf4 still runs at 168mhz(iirc). The DRV switching frequency isn’t changing… nothing is changing. Your simply removing the heat to allow it to continue to operate at normal operating temps…

That’s like switching cpu coolers… Not overclocking. :expressionless:

Also more motors + focbox more money and not necessary. But that’s my opinion…


ok, there’s no point in arguing anything with you. I could poke holes in your statements too. I never said it is overclocking, just that it’s like overclocking. Basically, your going to pump up the heat, like overclocking. No your not changing the clock frequency or anything. But I was using it to compare what your doing in terms of heat prodction. Then, your trying to pull that extra heat away with extra cooling. If you go 4wd, you solve that heat issue, you add more traction, and potentially, even more power than just adding a heatsink to 2wd. Then if it still over heats because your running way more watts now since you can in 4wd, you can add heatsinks for a beast of all beasts :stuck_out_tongue:


I don’t get why you think I’m trying to argue… But if you add thermal mass… Your effectively increasing the efficiency of the component… because it can run cooler.

Hot components have higher resistance. If you keep them cool and within the data sheets operating range. I’m failing to see how increasing thermal efficiency is like what your talking about…

I never over heat, in the 900ish miles I put in the board it’s only twice that I’ve gone up that run as fast as the board would take me…


I agree with both, just a matter of how much $ willing to spend. Roughly $700 an axle (2 motors, 2 foc’s + gears/mounts) vs. $ 2x aluminum heat sink.


For me with the risks involved with speed. It is always a better setup to not hit working limits on electronics. If the potential used doesn’t go over 65% of what, from the batteries TO the motors are capable of I believe a safety factor then is purposely built into the equation. An extra 700 to increase my chances of not hitting face to street at 40mph I think is a worth while investment. Heat sinks is also a doing the right thing. Someday electronic delivery systems won’t be a second thought. Till then we work with what we have and try to not make magic smoke.


dude, get your world record


The thing is @Deckoz & @evoheyax once you start producing the wattage MoeBro is, batteries and weight become your problem and to a large degree I think that’s why Moe is where he is at.
You will need 4x 6.4 based controllers to get where MoeBro is (or 6 x 4.12…).
And any 4 vesc/motors/drive system that can use 75a a piece will be heavier than Moe’s 2x…
Then think about a battery that can deliver 300a :exploding_head:
12s15p 30q? I don’t think so…

With that said if either of you build one I’m sure MoeBro will welcome the competition :hugs:
I Personally can’t wait for you (evo) to get your 4wd hummie hub board dialed in although I can’t help but feel in a head to head power challenge Moe’s RBII will leave you wanting :thinking:

@MoeStooge one of the fighting robot guys has made a monster 6.4 based controller, tested at 16s 150a…
But (x2) 20kw is more than anyone will need without being strapped in IMHO :crazy_face:
& BV is building a 300a capable vesc, which is essentially just three 6.4 controllers in parallel so nothing new there really :neutral_face:


Yea I can see that… I just don’t know if my mass requires that ammount of wattage for maintaining 30mph uphill on my evo… At this point I was just saying to myself. I would probably never run into thermal if I added heatsinks exposed to air…as it’s already rare and mostly stays right at 113F for most of my rides…


Do you think your Evo would go up and down a hill like at Tepe’s? I’m sure it is only a matter of time before the Stooge does another event you should go along to test your board, if you can it might help get others interested, be awesome to get a electric train going up & down a hill! :sunglasses:


Complete other side of the country. But maybe at some point :slight_smile:


ah :neutral_face: you’re still closer than me :upside_down_face:

edit: I think there is a reason 30mph/50kmh comes up often, on a track bicycle in a velodrome 50kph is the speed where half your energy goes in to breaking air resistance. Past 50 you progressively need more and more watts to go faster, or put equipment under more and more stress.


I’ve preordered one from his second batch of 20. Going on Ebike. Might try and smoke one 6374 on 16s for science.


Yeah 10kw per esc is a bit big for eSk8 IMHO :crazy_face:

but for a eBike…
make sure you drop us all some pics, what sort of motor will you be running bro?

Did you see he is working on a 450a controller as well, that would make a nice electric dirt bike :smiling_imp:


My 16s Battery will only be like 7.5kw. Which is overkill all over the place for eskate.

The controller is going on a 6kw Tangent Mid drive on a Downhill Bike Frame, haven’t decided on the frame yet. Tangent Dave said he runs his at 8kw on 12s. That’s V1 of his drive while v2 has better cooling. 300A peak with the current one is more than enough on 16s. On a under 50lb bike its already like a dirtbike with a roughly 65mph top speed and crazy torque.