Electric kart

nuxland · Jun 13, 2021

Building some oil/liquid a no. I just can justify it to myself

There is a lot of work.
But there is one thought that I can cool down pushed in air. I could make some 1 liter pocket out of aluminium outside of the motor, where this thin 1mm aluminium is. And then just put dry ice inside at the start, that ice will make the whole side of that aluminium extra cold and in therory colder air should enter the motor. But in reality air is a very bad heat exchanger so this could only bring some 5 degrees down if that much. But that is one thing that is easy to do.

But the second problem is distance. If only 7-9 laps then I can drive with 60% and motor is 130 degrees at end.
But when more than 12 laps, I also have battery capacity problem, because I use like ~2,2Ah per lap, so 10 laps is 22Ah (add here warmup laps 2 of them 2,2Ah also) and it's already 24,2Ah. And 30Ah is max from LiPo if I want that this lipo will last also.
So this will make 12 laps max (24,2 + 2x2,2 = 28,4Ah) and cooldown lap ~1Ah will make ~30Ah.

We raced 14 laps in wet and used 33Ah and that was already hurting that LiPo

Chalo · Jun 13, 2021

stan.distortion said:
fluids downsides are added weight and complexity plus there's going to be some additional drag from an immersed rotor

Drag at low speed means cavitation as speeds go higher. All the energy wasted as fluid drag in the motor turns into heat in the system you're trying to cool that way. There's a lot of tail chasing in that approach.

Ianhill · Jun 13, 2021

Nuxland

You can add mass to the motor alloy plate and increase the size of the thermal well.

You can attempt to cool the motor with dry ice but the air will move past the ice quicker than it can absorb the cold so it will come out simular temp the key to air cooling is masses of it flowing fast if i put my hand out a car window at 10 mph vs 100mph ill get cold much sooner at 100mph larger my hands surface area and less mass the quicker i will lose my heat to the environment.

Skinny tall people die in vold water in under 2 hours a large fat man can push on 24hrs ive heard of so shape and mass makes a bug difference to your heat loss

We are water based so we pass heat fast don't believe me jump in a cold shower metals pass heat slower than water but csn still outperform coolant based liquids that have half the thermal tranfser of water.

Race cars use less coolant more water for a higher specific hest capacity and dragsters eliminate it completely and add just enough mass for a large enough thermal well to take a full power run and end up at a desired temperature all predetermined before the run the water jacket in some instances is filled with cement to give structural support to the block cooling has gone out the window.

Ianhill · Jun 13, 2021

Ive got a qs138 in the post and going to build a kart to cool my motor i plan on using a fin setup with a ram air chamber to give me surace area and fast flowing air without a fan all solid state, i don't do fancy computer drawing im oldschool we had a drawing office in my old job so i use pencil and paper but ill try and find something to flair some inspiration

Ram air will increase the air velocity and the fins will increase the airs surface area interaction by then using 2 thick direct connections to case i can wick the heat out into the fin stack and away air flows over and out the back of the motor unimpeded so the original air cooling is ramped up with no restrictions

No need for ice or fan power as a 12v squirrel cage fan can pull 4amp and i got yellow dipped white full beam lights to go on the front of mine as a pair (60w) so ill need aux battery 12v and separate traction 88.2v make it easier on the contactor setup too no dc converter needed.

Sorry for adding a ton to your thread.

Hillhater · Jun 14, 2021

For serious heat dissipation (eg, on heavy truck brake rotors).. a water spray direct onto the heat sink area is very effective.

nuxland · Jun 15, 2021

Hillhater said:
For serious heat dissipation (eg, on heavy truck brake rotors).. a water spray direct onto the heat sink area is very effective.

Motor outside is not that warm because i push air through. So water sprayng these will not give me that effect.
But I got another idea, to use sodastream or similar 425g co2 canisters and put it on side of motor and connect to air inlet scoop.
Then when I open it the co2 goes cold and makes everything around it cold. Just can not fine how long will this bottle empty itself when not opened fully. I actually only need it in second half of the race about 4 minutes max.

Ianhill · Jun 15, 2021

Those co2 are 25g, good call vent a few of them directly on the winding inside the case and rapidly cool the main source of the heat direct, no more than a few hundred grams and it gets you to the result needed.

How would you dispense the co2 manual trigger or automatic ?
small solenoid valve ,relay or mosfet triggered, by a esp32 or arduino etc, thats got a temp probe and a preset temp to open the valve.

I like this idea but the motor case can not be kept closed dumping all that cold in the motor will create condensation its ok on the outer case but if your spraying the windings direct then a airflow also needs to be present to remove the humidity build up from a direct dump.

Surrounding the outer motor fins wouldn't present the damp problem the humidity would be kept outside the case.

Edit

Looks an expensive way of doing it unless you can refill c02 yourself

Hillhater · Jun 15, 2021

Why not just force the cooling air through a “bed” of dry ice (solid CO2) before it get to the rotor.
Much more volume of cold CO2 / + chilled air that way
Or, For the water misting, direct into the rotor cooling air. Intermittent spray depending on temp or motor load ?
If you use distilled water it wont hurt the windings and will evaporate off clean. ( probably cleaner than the cooling air ?)
Maybe follow up with something like a WD40 spray when the motor has cooled down.
Its the latent heat for the evaporation which makes it so effective.

Ianhill · Jun 15, 2021

Id be tempted to start with a 3.5oz paintball cyclinder see if that can cool enough see a good temp swing from a full dump of that plus its refillable with lots of size varients past 22oz if its not enough.

If we got the copper and lam mass we can get an idea of the specific heat capacity how much energy is needed to cool back down.
But as for spraying the co2 im not sure on the science needed to calc it theres a phase changing pulling heat away to work out how much to use not sure but its damn cold so i see where your going

Ill have a dig about on the phase changing see what i can find.

laapmetot · Jun 22, 2021

Great work nuxland on the kart! I'm also running a zero 75-7 with a gen4size 6 sevcon. Its not slow, but not nearly as fast as yours..... It draws 350 battery amps while on video I see yours instantly draws 600 battery amps. Would you be willing to share your dcf or do you have some pointers?

nuxland · Jun 29, 2021

Installed water mist cooling using clutch leaver

Now need to find time to go to racetrack and to test how it works.

fechter · Jun 30, 2021

I'll be curious to see how that works out. You could add a bunch of ice cubes to the water.

nicobie · Jun 30, 2021

I wonder if this could run on DC? $29 !

2021-06-30 13_11_08-Best Deals Online - Today's Best Daily Deals.png

SlowCo · Jul 1, 2021

A small membrane pump should work also:
https://nl.aliexpress.com/item/32439742285.html

laapmetot · Jul 1, 2021

fechter said:
I'll be curious to see how that works out. You could add a bunch of ice cubes to the water.

Actually the phase change (evaporation of the water) has much more cooling effect. Maybe an idea to use dryice, or CO2 canisters. This is done on intercoolers for turbo applications. Lots of cooling due to phase change liquid to gas, large pressure drop which also cools, no conductivity and no corrosion. This phase change is forced due to the pressure drop, while in case of water its still possible the water exits the motor without much evaporation, especially with large droplets.

Edit: aquamist makes good water injection kits for turbo applications. (in a previous life I made and drove a >300hp turbo motorcycle) It has 10bar pumps and atomizing nozzles. I can imagine this fine water spray in the airflow will help. The smaller the droplets the more evaporation hence cooling effect.

nuxland · Jul 12, 2021

laapmetot said:
Actually the phase change (evaporation of the water) has much more cooling effect. Maybe an idea to use dryice, or CO2 canisters.

Dryice is one option, but I have not figured out how to make a wire mesh and then put it inside to cooling chamber before race.
CO2 I actually bought 425g canister and ordered from ali adapter, but right now have not found any valve to use it with(it should tolerate 200bar pressue and have spring closing, so I can open it with my clutch leaver).

So the easyest was to install water mist injection and try that first. Original mist end that came with the bottle was not mist enough, so I bought regular spray bottle and did some modification. Will try that in wednesday on track.

nuxland · Jul 21, 2021

Have now tried in two different tracks and this water mist cooling is helping.
In our latest test on most demanding track in Estonia we managed to drive 15 laps and keep motor temperature under 110 degrees.

[youtube]1Q1KalURGqw[/youtube]

hallkbrdz · Jul 21, 2021

nuxland · Aug 5, 2021

Again this stupid "DSP Encoder Fault" is haunting me.
Last Prokart race in Põltsamaa we could do very good qualify time and then in the first final we could not drive out of the box because of that error.
Then I tested all the connections wires between motor and controller and they worked. Also wiggled the connector that came from the motor and it started to work again. Did no had the means and time to open that connector and test, because I had to remove the motor mount and open encoder cover to test it.
So in the final 2 we did drive very well but in the 7th lap got the same error and had to restart sevcon twice.
Loosing total 20 seconds for that and finished third.
[youtube]bGswM_Xlcw4[/youtube]
Our best lap time 36,116 was only worse from dd2 karts in that raceday (and there also first 3 out of 15 were faster then we)
We raced with retros 6gears and were faster over 1s per lap.

The same track track all time records are following:
Rotax max - 35.783
DD2 - 35.706
KZ2 - 34.297
Retro Minsk - 38.616
Retro CZ - 36.441

So now I will open that connector from motor and check all the pins one by one.

Egor.dp.ua · Dec 2, 2021

Hello
In 2018-19, we built a children's kart, on which we installed a modified 6 kW AC motor, a 24-felt controller of our own design and a Nissan Leaf 36v battery. The tests were carried out in conjunction with petrol karts participating in real competitions. In the second year, the car was already confidently driving faster than the RATAX micro. The speed reached 100 km / h.
Our test pilot was 7-8 years old.
But now I decided to build a more powerful kart. In search of a motor, I came across your project. I was extremely surprised at the enormous power you are using. Now I don't know what I want.
I am well aware of the problems you are facing.
I haven't met for a long time who will build a go-kart for real competition with gasoline engines.
You have a very cool project !!! I really like it !!!

https://www.youtube.com/watch?v=ucfFay_HTb4

SlowCo · Dec 2, 2021

Egor.dp.ua said:
Hello
In 2018-19, we built a children's kart, on which we installed a modified 6 kW AC motor, a 24-felt controller of our own design and a Nissan Leaf 36v battery.

Great work and nice project :thumb:
Could you start a thread about your build especially the controller and motor you used for this kart? It sounds very interesting!

Edit: I found your video with motor and controller:

[youtube]F6PkdWQ6myo[/youtube]

Egor.dp.ua · Dec 2, 2021

Industrial AC 380V engine, turns reduced 10 times, wire about 16mm2, 1 holl speed sensor.
Controller PIC18F2431 PICASM, 24 Fet, Sine, Vector, all functions and settings at my discretion. The motor can rotate indefinitely (16-20-25k rpm), but the torque drops. At the beginning, they twisted up to 16k rpm, but then they switched the windings and optimally up to 10k rpm.
Tuning card corresponds to rotax 125 micro max, about 6kW mechanical.
Judging by the heating, the efficiency is not very good, the motor heats up to 100 C. Batteries nissan leaf 5 pcs, 36v,> 200A load, they are also heated.
For more than 90% of the time, the throttle is full.
The throttle only controls the engine torque.
Very good roll-forward! Really like the sound of the engine.)
Kart weight <110 kg with a pilot.
Our goal: low cost versus gasoline engine
there is some video: https://www.youtube.com/user/egordpua/videos

Ianhill · Dec 12, 2021

Egor nice effort, the squirrel cage rotor will always get warm theres no stopping that theres around 3% loss to a decent rotor in that tyoe of setup so 6000w could see 200w of heat dumped into the squirrelss bars alone...

This guy got some decent explanation and picture vids for a basic grasp.
https://youtube.com/c/Lesics

Hillhater · Dec 12, 2021

Egor.dp.ua said:
Our goal: low cost versus gasoline engine......

I would not make that a essential feature, it is likely impossible !
Club level karting is dominated by either the Rotax Max based motors for the wealthy racers, whilst the bulk of the club level and junior classes, and starter classes are being taken over by 4 stroke , 6-10 hp “industrial” based motors that can be bought for $100 new ! .
Any electric solution must be simple, reliable, with low level of expertise required to maintain...”Plug and Play”

nicobie · Dec 12, 2021

Hillhater said:
Egor.dp.ua said:

Our goal: low cost versus gasoline engine......

Click to expand...

I would not make that a essential feature, it is likely impossible !

I'm not so sure about that.

Years ago I was part of a team that ended up US west coast Champs in a couple classes of non shifter karts. Most of the teams had their motors pro built, and like all racing stuff, in order to win everything has to be on the edge of blowing up. That means going through a lot of expensive engines (and clutches) every season.

Going electric might end up being cheaper in the long run.

However I'm not too sure what hauling around those batteries will do to your kart's handling or chances of winning. But for sure it's worth testing.

Electric kart

100 W

100 TW

1 MW

1 MW

100 TW

100 W

1 MW

100 TW

1 MW

100 mW

100 W

Attachments

Administrator

Moderator

1 MW

100 mW

100 W

Attachments

100 W

100 W

100 W

1 µW

1 MW

1 µW

1 MW

100 TW

Moderator

Similar threads