Electric kart

Electric cars, trucks, ATVs, NEVs - things bigger than a motorcycle.
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nuxland   100 W

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Re: Electric kart

Post by nuxland » Jun 13 2021 12:31pm

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.
DryIce.jpg
DryIce.jpg (212.04 KiB) Viewed 504 times
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 :(
Last edited by nuxland on Jun 13 2021 12:38pm, edited 2 times in total.
Electric kart 60kw: viewtopic.php?f=34&t=68543
100v 35Ah LiPo battery: viewtopic.php?f=14&t=97763
100v 25Ah LiFePo4 battery: viewtopic.php?f=14&t=85912
Scooter battery: viewtopic.php?f=14&t=108227#p1582703

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Chalo   100 GW

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Re: Electric kart

Post by Chalo » Jun 13 2021 12:34pm

stan.distortion wrote:
Jun 13 2021 10:34am
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.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

Ianhill   100 MW

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Re: Electric kart

Post by Ianhill » Jun 13 2021 1:06pm

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.

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Re: Electric kart

Post by Ianhill » Jun 13 2021 1:13pm

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   100 GW

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Re: Electric kart

Post by Hillhater » Jun 14 2021 2:23am

For serious heat dissipation (eg, on heavy truck brake rotors).. a water spray direct onto the heat sink area is very effective.
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nuxland   100 W

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Re: Electric kart

Post by nuxland » Jun 15 2021 1:38pm

Hillhater wrote:
Jun 14 2021 2:23am
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.
Electric kart 60kw: viewtopic.php?f=34&t=68543
100v 35Ah LiPo battery: viewtopic.php?f=14&t=97763
100v 25Ah LiFePo4 battery: viewtopic.php?f=14&t=85912
Scooter battery: viewtopic.php?f=14&t=108227#p1582703

Ianhill   100 MW

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Re: Electric kart

Post by Ianhill » Jun 15 2021 2:30pm

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

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Re: Electric kart

Post by Hillhater » Jun 15 2021 7:11pm

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.
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Re: Electric kart

Post by Ianhill » Jun 15 2021 8:39pm

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.

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laapmetot   100 mW

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Re: Electric kart

Post by laapmetot » Jun 22 2021 11:30am

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?
zero1.jpg
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zero2.jpg
zero2.jpg (756.22 KiB) Viewed 354 times
zero3.jpg
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zero4.jpg
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nuxland   100 W

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Re: Electric kart

Post by nuxland » Jun 30 2021 1:42am

Installed water mist cooling using clutch leaver :) Now need to find time to go to racetrack and to test how it works.
Attachments
ClutchLeaver.jpg
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MistBottle.jpg
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Electric kart 60kw: viewtopic.php?f=34&t=68543
100v 35Ah LiPo battery: viewtopic.php?f=14&t=97763
100v 25Ah LiFePo4 battery: viewtopic.php?f=14&t=85912
Scooter battery: viewtopic.php?f=14&t=108227#p1582703

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fechter   100 GW

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Re: Electric kart

Post by fechter » Jun 30 2021 8:02am

I'll be curious to see how that works out. You could add a bunch of ice cubes to the water.
"One test is worth a thousand opinions"

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nicobie   1 GW

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Re: Electric kart

Post by nicobie » Jun 30 2021 3:17pm

I wonder if this could run on DC? $29 !
2021-06-30 13_11_08-Best Deals Online - Today's Best Daily Deals.png
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SlowCo   1 MW

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Re: Electric kart

Post by SlowCo » Jul 01 2021 5:26am

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

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laapmetot   100 mW

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Re: Electric kart

Post by laapmetot » Jul 01 2021 10:29am

fechter wrote:
Jun 30 2021 8:02am
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.

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nuxland   100 W

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Re: Electric kart

Post by nuxland » Jul 12 2021 12:08pm

laapmetot wrote:
Jul 01 2021 10:29am
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.
Attachments
MistBottle_Installed.jpg
MistBottle_Installed.jpg (228.96 KiB) Viewed 139 times
Electric kart 60kw: viewtopic.php?f=34&t=68543
100v 35Ah LiPo battery: viewtopic.php?f=14&t=97763
100v 25Ah LiFePo4 battery: viewtopic.php?f=14&t=85912
Scooter battery: viewtopic.php?f=14&t=108227#p1582703

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nuxland   100 W

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Re: Electric kart

Post by nuxland » Jul 21 2021 2:24pm

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.

Electric kart 60kw: viewtopic.php?f=34&t=68543
100v 35Ah LiPo battery: viewtopic.php?f=14&t=97763
100v 25Ah LiFePo4 battery: viewtopic.php?f=14&t=85912
Scooter battery: viewtopic.php?f=14&t=108227#p1582703

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hallkbrdz   100 W

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Re: Electric kart

Post by hallkbrdz » Jul 21 2021 9:23pm

:bigthumb:

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