Electric kart

[nuxland]

Nuxland - Nice! I would have like to have made the support all aluminum, but metric tube supply here is - difficult. Oh well, maybe the next time.

I had to buy 6m lenght tube and I only used like a 1m from that
Finished welding and aluminium is lighter than original.

I have to cut out parts and make battery base plate also lighter. Actually I do not need the middle part at all, it is there for correct distance between front and rear fixations. So will be making big holes there

 

[nuxland]

Left SidePod holder and battery baseplate holder is now finished and compared to my old tony frame the new is 520g lighter

Made my battery baseplate also 580g lighter

So together I was able to make left side about 1100g ligther compared to my old frame.

 

[nuxland]

Finally completed new motor cooling sideplate. Comparision to my old one, the new one is like 1,17kg heavier

In initial test with cardboard box and hole inside in front of the opening old fans where able to push 20m/s wind through hole and new ones 23m/s. So not so big improvement but it's still more air through motor and every m3 counts

Here is motor weight together with baseplate and cooler plate.


In my calculations I will save that 1,17kg from lighter controller heatsink 8)
There was also extra aluminium plate in old tony frame that will not be in the new frame.

 

[Solexelec]

hi Nuxland

have you ever thought about using water spray?
I tried on outrunner it works well.
they were outdoor misters for the terraces.

 

[nuxland]

have you ever thought about using water spray?
I tried on outrunner it works well.
they were outdoor misters for the terraces.

When I had closed motor with oil inside, I thought to cool with compressed nitrogen (these little bottles that airguns are using) and to spray it through some misters to motor fins. But it did not go nowhere.

Almoust finished controller baseplate and heatsink. Baseplate is fixed to the frame with 2 x M8 bolts. Right now there is regular bolts, but there will be countersink bolts, because space between heatsink and holder is like 5mm only.

Then heatsink is fixed to baseplate with 4 x M6 rubber holders that you can see in controllerbase image

And then controller is fixed with 4x M6 bolts to the heatsink. (there is also contactor fixed to the heatsink)


At first will try with heatsink only (and it should be enough considering my test with watercooled controller)
But if it is not enough then I have this little 5mm spacer that I can install between controller and heatsink.
And then make little holes through controller heatsink and add watercooling to the setup

 

[hallkbrdz]

Nice heatsink/mount design, and now with quattro ventole cooling for the motor. :thumb:

 

[nuxland]

Weighted new controller parts, new is 6,51kg lighter and that with contactor.

Old watercooled with big heatsink and without contactor

Also installed accelerator unit and cable

It's 3 degrees celcius outside, so can not work more than 1h in a row

 

[nuxland]

Finally could move to garage and finish up all the wires in the new frame. As this so called "turbo" button on the wheel (that actually activated profile 2) was very hard to use in races (you have to look and then keep it pressed). Then now I installed 2pcs of tumbler switched instead ON-OFF-ON. So the right one will be configured Down-Profile 1 and Up-Profile 2, in the middle - Base Profile. And Base will be configured max 5000 rpm and max 60% of torque. Profile 2 like now 6000rpm and 100% torque. And Profile 1 to 4000rpm and 40% of torque. Then it is easier before the corner to switch to profile 2 and exiting the corner already full power available to pass someone in front of me
But have not figured what to configure to left switch (I have wired there actually one Digital Input and one Analog input so if needed just change switch to something else in the future)
Made also a little video about the progress: https://www.youtube.com/watch?v=gAUEnLZVcoc

 

[louis raaijmakers]

nice to folow this build and see the updates!

congrats to the great work! just for comparising, howmany cc 2stroke karts are no problem to beat?
250cc shifter karts?

keep up the good work!

 

[hallkbrdz]

Agreed - great build as always.

Louis - 250cc shifter - is that a vintage kart engine? 80cc, 125cc, 175cc - but I've never seen a 250cc engine.

 

[nuxland]

In Estonia there is no 250cc shifters (they use these in big tracks in other countries and their top speed is over 200km/h).
But we have 125cc three versions 1. without gears (rotax max) 2. with 2 gears (rotax dd2) 3. 6 gears (KZ2).
Also ProKart events there are also old soviet karts both 125cc, 1. 4 gears Minsk and 2. 6 gear CZ
(some use old soviet frames with old soviet tires and others have put these motors to modern kart frames.

If we compare my kart lap times then we have to take account that I have not raced with new tires (always used) so there goes at least 1s lap time Then My driving skills are not very good and there goes another 2s lap time.
Last test we did in Põltsamaa "Kuningamäe" kart track with a driver who races KZ2 as pro. He got lap time 37,79 (in 7th lap with used green vega tires and there was no rubber in asphalt as there is in competitions). Also that was the first time he raced with that kart and I think he could driven better if the accelator wire would not have broken .
He got to drive 4 minutes and 24 seconds only: https://youtu.be/rShP1MLI-p0
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 2 second slower than regular 125cc no gears and under 4s slower than KZ2 kart track record (you have to take account that record is from pro driver who knows how his kart acts and so one)

But if you take some Prokart Estonia competition then for example in kz2 races 4th place best time was 37,247 (about the same as we got)
DD2 winner best lap time was 36,343 so a little over 1s better.
https://speedhive.mylaps.com/Events/1418497

So I think that when I finish moving to a new frame then a good driver with brand new tires can drive lap time close to track record

 

[louis raaijmakers]

cool!

thats you need some serious power to beat 125 shifters. cool to see.
looking forward to the new frame and a new track time!

curious to see a few seconds of the lap time

greetings louis

 

[nuxland]

Made myself a wheeled table to configure motor and controller in the livingroom. Can't took the whole kart there
So now the second controller should be also configured to that motor. Had to change configuration laptop time to year 2017, because sevcon license is only for a year (I do not understand how this can be as I have bought it for quit a big sum of money) and you have to email and ask for a license every year. I had working official license from 2016 to 2017 so changing computer date works in my case.

 

[nuxland]

Finally finished installing everyting over the weekend. There will be race this sunday and bought myself a brand new set of wheels to see what times this new frame can give me
Tablet is now behind the wheel. It was very hard to find windows tablet with full USB port. But finally I found on in aliexpress and it got here like 4 months But working great and no issues so far.

Installed GPS on top of motor and everything looks more clean now.

 

[SlowCo]

Good luck with the race :thumb:

 

[Ianhill]

Co2 extinguisher is good for cooling the motor between runs.

Like this build alot must be a right blast and gives even the geared karts a roasting.

 

[louis raaijmakers]

cool build still folowing

 

[nicobie]

How did the race go?

 

[nuxland]

How did the race go?

It is this sunday 16.May 2021 (In Estonia week is from monday to sunday)
But will do a test today evening on the racetrack and hopefully can render video and some graphs today before midnight.

 

[nuxland]

Pushed my lipo battery to the limit to test can I race 14 laps with it. We raced 4 laps and then changed front wheel width to get better grip turning on to corners. And then raced 11 laps until I saw that minimum cell voltage wen under 3v and then we stopped.
So conclusion is that I have to top the battery to 4,2v instead of 4,15v and run warmup lap very easy and then run 14 laps and cooldown lap also very easy. Maybe also keep some race laps easy.


This was 11th cell group that went that low and only this one group. And I used 31,25Ah from my 28 pcs of 5Ah 7s lipo bricks. I have them configured 7pcs in paralel so together 35Ah should be there. But not in my power levels

 

[Ianhill]

Those plots are interesting to follow some high speed points that must of been downhill or less incline with lower amp pull at full speed and another area with the 120kph/75mph taking the full 50ish kw peak and a sub minute lap.

Like that alot.

 

[LuigiDesign]

That is amazing that voltage drop so positively affects motor temperature.
And when you look at this graph it is understandable why it is so.
There is less current to field weakening (the current that does not make torque but just heat) the blue one.
Motor current is around the same spot (orange one) and it should be, beause configuration and speeds are the same, only voltage sag is less

As soon as your voltage drops the mod index reaches the top on earlier rpms, so the field weakening starts earlier to keep the torque demanded, but it is not for free, it´s known that the field weakening means it change the angle of the controller phases compared to the Back EMF, therefore it causes a missalignment, more losses, more heat, less "clean torque", less range, etc...

Here you have the logic explanation of why the powerfull LIPOs are more efficient than the other ones because lets the motor works more time under(below) the max mod index...

PS: Try to increase from 90% to 95~96% the max drive mod index parameter, and check if the mod index graph still always below the max 95% in all scenarios, if yes, you will increase your efficient at 0 cost due to even less FW!

 

[nuxland]

Thanks for that info Luigi, will try that after the race

Finished rendering video also yesterday, but forgot to link it here. You can clearly see that in the middle of the last lap 10th cell voltage dropped below 3v. Also we drove the best time ever and around 1s faster than with old frame 43,245s.
With brand new tires target is under 43 seconds in sunday.
[youtube]8WxDaxFTrJs[/youtube]

 

[Ianhill]

The track was how i imagined great how thats visible on the graphs well worth the effort to log it all rich data set.

 

[LuigiDesign]

Thanks for that info Luigi, will try that after the race

Finished rendering video also yesterday, but forgot to link it here. You can clearly see that in the middle of the last lap 10th cell voltage dropped below 3v. Also we drove the best time ever and around 1s faster than with old frame 43,245s.
With brand new tires target is under 43 seconds in sunday.
[youtube]8WxDaxFTrJs[/youtube]

Let me know how it works! I´ve seen the video, my honest suggestion about your driving style is try to be more gentle and finest with the steering wheel and pedals avoiding as much as possible counter steering and skiding, think that you have an extra weight that forces tires, brakes, and is energy throwed to the tarmac... More finest you drive, more quicker you will be and will long last your packs. Trust me... Try to find some of the finnest drivers near to you and take from him some classes, you will appreciate it with such a beast! :wink: