Jake's Direct Drive build, NSW, Australia - Success!

What do you mean by W/mk?

That is the unit for heat conductivity. A higher value means better heat transfer.
You assume 15 Watts of losses in a single transistor on your Vesc for 90A motor current. This assumption is a little bit on the safe side but you have more losses the hotter your transistors get. Your thermal pad has (example values I found: Thermal Pad Materials for Thermal Solutions_ SinoGuide Technology) for example a thermal condutctivity of 6 W/mK and is 1mm thick. The surface area of the transistors you can use for cooling is about 1cm². So you can calculate the thermal conductivity of your thermal pad to be 0.6 W/K = (0,0001m²/0,001m)*6W/mK. This means with 15W of losses your temperature rises 15W/(0.6W/K)=25K (or 25°C) because of your thermal pads alone. If your thermal pads were pure aluminium with about 170 to 200 W/mK your heat would be removed much better with only a rise of <1°C under the same circumstances.

What this really should suggest is using only very thin thermal pads if you need electrical isolation to the heatsink. I have done many experiments with the Vesc 4 in my setup myself and can only suggest that for running any currents higher than 60A conitnously addidtional cooling beond a simple fan is necessary.
Removing the heat through the plastic case of the transistors (i.e. heatsink on plastic back of transistors) is not really worth the effort. Soldering some from of cooling to the remaining metal tabs on the transistors like PowerGlider did can help to acheive higher currents but the Vesc 4 is really hard to cool beyond 80A. You might just get there for your motor current with cooling fins soldered to each remaining tab on the transistors and a fan. I went a little bit beond that and have remounted all fets and attached a big watercooler to all fets on the metal cooling pad, the fets stay cool with over 100A now. But I have trouble with the current measurement shunts now. Those also make 10W of heat and are even harder to cool.
My suggestion would be to test your current setup with your current cooling. If you find you need just a little bit more power you can solder small copper cooling fins to the mosfet tabs. In any case add a fan to blow some air over the shunts and your cooling devices. Altough your heat is trapped in the waterproof box this should give you more time until your vesc throttles back.
In any case keep up the good work. I think I might have to add a second motor to my 6374 and go from my jet drive to your setup. Thanks for sharing your findings!

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Ah!ah! On your back, opposite side than foil! As soon as you feel getting close to the point on ‘non return’, jump out!

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Well, if you go beyond 60A cont. in dual setup you will have battery problems (discarge rate of multistar should not exceed 5C over longer period and runtime will decrease to like 10mins) before you have thermal problems…
So my guess is, that there is not very much missing…

@Flo @Giga Ok I see, Aluminium alone is a lot better!

The heat sinks did help a bit I can ride continuously for over a minute now. Heres the youtube video of it now, I’m getting a bit better at riding, the heat sinks let me fly for much longer than before…

@MaB yes I see what you mean, it is very important to do it, otherwise its so easy to fall into the wing!

I might try water-cooling the heat sinks that are touching the top of the FETS for now, so i don’t risk stuffing the VESCS, if its not enough, Ill try something like what @PowerGlider did with his VESC.

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Has anybody tested other potential solutions such as:

  • to avoid salt contact (even if circuit is rinsed after each session), fresh water closed-circuit cooling as done on CNC router spindles, computer CPU. Water in a small bottle might require a separate safety compartment in/on the deck due to battery proximity though.
  • thermoelectric/peltier cooling ?
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Thermoelectric does not work. Power requirements too high and cooling is not very much.
Also, they only transfer heat a very short distance

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thermoelectric:peltier cooling does work (see Peter setup), i have tried 3 peltier in the row without sucess only because my heatsink on the hot side was to small and i need a fan when in static , the heat was going back to the cold side and the esc

i let go this type of cooling only because i have enough air cooling just by the heat sink on top of my case

cpu water cooling may work in closed loop, but this is starting to be heavy

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Is your dual 6364 motor setup still working? That’s my next attempt, if I get the time.
BTW, nice Cyclone videos on your Youtube channel. That’s my favorite ebike kit, as close to a dirtbike and still be able to pedal as possible.

Yeah its going pretty well, i can ride for over 15 mins now but it still certainly needs tuning to make it more efficient, it cruises at 2800w which is to much i want to get it to around 2000w or less.

Thanks about the cyclone vids…I’ve done a few mods since those videos. I’ve gone to single speed drivetrain with thicker BMX size sprockets as regular bike sprockets wear out to fast.

Whats your cyclone setup? it is an awesome motor :slight_smile:

Thanks for the reply. One more test hopefully today with the Boma motor and if that doesn’t work, I’m going with the dual 6364.

I have the Cyclone on the EEB frame and another on a Kona Stinky. Both setups are beasts. I know its off topic, but how did you attach the BMX sprocket? I’m running a single speed on the EEB with a single speed conversion kit using BMX chain, but would love to have something tougher. Only problem with the Cyclone is having to beef up the motor mounts. I wish they’d fix that. I still have to spend time dealing with chain issues due to flex randomly. I’m going to make a custom mount when I get time to work on that project. I did end up buying the Sur-ron which is awesome and in the long run will probably costs less.

I remember a while back you were looking at using 2 motors to drive a single shaft in order to increase the power. It seems it has been done on the onean boards if you look at motor system diagram: https://www.produzionidalbasso.com/media/projects/15589/files/Specifiche%20Tecniche%20ONEAN%20JET%20PACK.jpg

It would be very interesting to see what speed controller they are using to drive this setup!

Good work here Jake !
How did you go from 1 minute ride-time to 15 minutes ride time ? Watercooling the FETS of the Vescs ?

What is the Boma motor?

Nice bikes to do it on :slight_smile:

To make it single speed is fairly straightforward, you can buy single speed sprockets that slide on where the cassette mounts on the free-hub, so you just have to unbolt the cassette, slide on the single speed sprocket and space it with washers to suit the chain alignment, and screw back in the lock ring. Then I just modified an old derailleur for single speed chain tensioner by holding it steady with hose clamps. It is very sturdy and there is no chain skip or coming off because the teeth are much higher. You can do away with a chain tensioner if the bike isn’t dual suspension.

To minimise motor flex I made a bracket to attach the far side of the motor to the clamp, the takes away the flex and it can easily take to torque of the motor from this. here’s a picture:

Thanks! I have different ESC’s now, YEP 120A HV. They do get warm but not to bad.

It looks like a nice setup they have, I’d imagine there is a separate ESC for each motor, but i think its possible to use one ESC for two motors if the stators and rotors are perfectly aligned.

I’m not quite sure about onean, from the picture it seems there is a single unit, but it may be a double ESC unit.
I have also fount that AXI used to make a dual motor setup: DOUBLE AXI 5330/20 GOLD LINE | AXI MODEL MOTORS s. r. o. which gave around 5kw I think.

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Wow, this certainly isnt a new idea!

Hi Jake!

I am new to this hobby, but already have plenty of experience in the rc hobby. I got really interested in the relative simplicity in your build compared to other, geared builds. I am planning to order two 6s 16ah lipos, two vescs and two of the same motors you use from hobbyking and design the control circuit including temperature, current, voltage and consumed mah monitoring with an arduino pro mini. I am firstly going to build it on a surfboard for primary testing.

The main components that i’m worried about are the propellers. I already converted smaller foam bodybords to electric for kids with smaller brushless motors, escs and lipos, but I used rigid miniquad propellers cut down to size and they worked great. Now that I’m planning to build a “real” electric surfboard, I am figuring out about 3D printed props, since they are the best option for me because I own a 3D printer (with a volume of 200mm x 200mm x 250mm). Can you post your cad files for the props you`re using? Also, is the rigidity of them enough for long term use (considering that I will only run it in freshwater)?

If you want to go with this setup, I do not recommend VESCS, they overheated after 1.5 min of riding with heat sinks installed. I would go with dual flier 300amp or similar. the 3D printed props are a long term solution in my opinion, ill post all files for this build below. However I recommend going with a single 80100 motor for better efficiency. Although this build is cheap apart from the ESC’s and does work reasonably well.