Formula E-kart

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Post by roddilkes » Mon, 12 Jan 2009, 18:49

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Post by acmotor » Tue, 13 Jan 2009, 23:44

Yes, we quite firmly blamed Rod for dragging us kicking and screaming along to the event (actually, it was a good hoon around).

It was interesting to turn the mind to the advantages that electric propulsion could give to this sport.
The first being the very different torque curve of electric drive compared with the ICE.

We need to work on some regs for this e-kart class. Hopefully standardising on motor / frame / tyres and allowing a fair degree of flexibility in batteries and energy management in general.
IMHO, a general opposite to the Swan EV challenge thinking. This one is sport !
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Post by Striker » Tue, 13 Jan 2009, 23:49

acmotor wrote:Hopefully standardising on motor / frame / tyres
Would there be any merit in the possibility of adopting the current standards for petrol karts as far as non-motor/battery things are concerned?

Same frame, same steering/brakes/everything, other than the motor.

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Post by Simon » Wed, 14 Jan 2009, 02:21

Yes I think the plan is to use standard second hand kart frames.

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Post by acmotor » Wed, 14 Jan 2009, 03:34

The thinking is to adopt the J class chassis with fixed rear axle (spool), chain drive, single rear disk brake (no front brakes in this class). Reasonably enrty level, but a good place to start.

Dicken (the relaxed gent on the left in top photo) is an ICE go-kart owner already and is researching (!) specs for us. He is up to speed with the various options (Hi Dicken !)

I'm thinking we need to lock in a motor size / type / kW or actual model such as the MARS BLDC 5kW 48V unit to establish a class.
(even if just because Rod and I both have one)
Voltage / controller / batteries / energy management being the variables with perhaps a 72V limit, then maybe not.

The aim would be to get more than 1 e-Kart on the track and have them compete on some degree of even level otherwise you just end up with an exhibition machine and not sport.
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Post by Electrocycle » Wed, 14 Jan 2009, 05:38

what controllers are you using on the Mars motors?
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Post by roddilkes » Wed, 14 Jan 2009, 07:32

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Last edited by roddilkes on Sun, 05 Apr 2009, 20:20, edited 1 time in total.

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Post by Electrocycle » Wed, 14 Jan 2009, 08:07

how are you finding the Kelly's performance?
I've been trying to find out if it's worth buying one because my controller has issues with takeoff from a standstill, and can't handle enough volts.
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Post by Gow864 » Wed, 14 Jan 2009, 17:35

Electrocycle I have a KBL48301 running a Mars BLDC and it works fine. smooth takeoff great acceleration, no problems at all really.

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Post by Electrocycle » Wed, 14 Jan 2009, 19:22

hmmm, I might have to try one.
The problem is that I can sell my complete setup, as it'll work really well in some applications.
But if I change controller I can't really sell my leftover one so easily.
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Post by acmotor » Wed, 14 Jan 2009, 20:53

I have a KBL48301(48V) and Mars BLDC. Not fired in anger yet.
What model is the 72V Kelly ? does it work with the Mars BLDC for higher revs, same 300A max, 100A cont ? or is it a different motor as well ?
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Post by Electrocycle » Thu, 15 Jan 2009, 01:38

there's only one Mars brushless motor at the moment.
It's rated for 4000rpm max, which is about what it should do at 72v (with light load)
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Post by acmotor » Thu, 15 Jan 2009, 03:41

Just dug out the link again...

Mars and Kelly

ON 48V KBL72301 ... same with 48301 ?
Image

ON 54V KBL72301 ... same with 48301 ?
Image

What is the x axis ?? torque ? units ?

There are some significant differences in performance.

So can the Mars motor be run on any higher voltage ? Any advantage.
It would be worth knowing so we can decide on 48 or 72V for the cart standard.
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Post by Electrocycle » Thu, 15 Jan 2009, 03:48

I'd say the x axis is amps.


The motor is rated for 48v, but since it's a brushless and seems to have decent insulation it'll take plenty more than that.
Kelly are selling 120v controllers for them.

If I was to standardise things I'd probably go for the Mars brushless motor and 48v - but I think the performance will be much better at 72 (can run lower gearing)

48v gives more options for controllers, but in the end you're probably best all running the same controller and motor - with a choice of battery technology for different budgets (you could have two or three SLA packs to cover a day's use and still spend a lot less than a Lithium pack.

As Geoff has found, the extra weight an e-kart is carrying really takes its toll on the tyres, so you might need to find some harder compounds or something or you'll kill a set every meet.
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Post by acmotor » Thu, 15 Jan 2009, 04:03

It's just that when I went to school and plotted the same value on x and y axis (neatly on the drawing slate) it gave a straight line showing the same value at any intersection and going through zero.

I'd be happy with 48V.

Do we need to specify a weight range ?

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Post by zeva » Thu, 15 Jan 2009, 04:12

acmotor wrote: What is the x axis ?? torque ? units ?


The X axis of these motor dyno charts is almost always torque, as the way they're tested is to have the motor drive an increasing load (i.e torque) and measure how the rpm/volts/current/etc changes.

In this case I believe the x-axis units are inch-pounds, 1 in-lb = 0.113 Nm. This would make sense with the Watts Out curve where take the 160 in-lb mark for example = 18 Nm, x 2500 rpm / 60 * 2PI (converting to radians per second) -> power of 4716W, looks about right on the Watts Out curve.

Edit: Interesting though that the amps and inch-pounds happens to be pretty much 1:1 - coincidence I suspect, but hard to fault Electrocycle's assumption! Image (Being a permanent magnet motor, it has a constant amps to torque ratio.)

And I wonder why they chose such different scales for all the axes between the 48V and 54V plot..? Makes a visual comparison rather difficult Image Anyway I agree with Tuarn, 48V would give good performance and keep everything nice and safe. (Not that 72V is particularly dangerous, but 48V is better still?)
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Post by Electrocycle » Thu, 15 Jan 2009, 04:15

well the amps line *almost* goes through the same value intersections :)
Definitely some bad graphing anyway!

I think 48v would go ok but won't be particularly exciting on that motor.
It'll be decent racing but you won't be competing with the ICE Karts at all.

A weight range is a possible class definer, but can also add complication.
In the beginning you really just need as many people as possible doing it.
You could all run together and have results separated into two (or more) weight classes, or just have classes for lead acid and lithium.
People using more batteries will have more weight, so things should even out ok.
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Post by acmotor » Thu, 15 Jan 2009, 04:21

Hoops, that was the direction I was heading and just tried a power calc but couldn't imagine the unit on the graph !

Not wonder EVs are being held back if you measure torque in inch pounds....and the USA claims not to be imperialistic !

Point taken re added complication on weights Electrocycle.
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Post by Electrocycle » Thu, 15 Jan 2009, 04:29

ah yes, I thought there was a torque scale on the left as well for some reason :P

It seems that most motors are rated in different units for torque.
I've had to convert between them every time I try to compare motors!
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Post by Gow864 » Thu, 15 Jan 2009, 05:33

I'm sure you've all seen this. 48V Etek

This video brings up a point. Why bother competing or comparing with ICE karts? you could hold an entire event in an underground car park, they can't do that. perhaps a time trial event bottom floor to top?

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Post by Striker » Thu, 15 Jan 2009, 05:37

@Electrocycle - how many kilos do you think Geoff's batteries add to the kart?

@Everyone - I'd like to see some real-world testing (IE: A kart around a karting circuit) to compare the suggested combination against an ICE kart.

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Post by Electrocycle » Thu, 15 Jan 2009, 07:19

The batteries add about 50kw to Geoff's kart.
Doesn't seem to bother the acceleration much, but the tyres and the brakes are working hard!
Gow864 wrote:Why bother competing or comparing with ICE karts? you could hold an entire event in an underground car park, they can't do that. perhaps a time trial event bottom floor to top?


you'd need a lot of safety barriers, but it'd be fun!

I don't think they need to compete with ICE karts to be fun, but they need to be pretty quick to get people to take them seriously and really generate interest.

I've driven some electric indoor karts that weren't super fast, but they were surprisingly fun.
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Post by acmotor » Thu, 15 Jan 2009, 08:26

Sorry, Kart racing with concrete trees is just stupid. Call it population control.

Every race track in the world makes great effort to remove the obvious safety issues. The fun stops when someone gets hurt !

Princess Diana learnt about concrete trees the hard way. Why do you think the world spends billions on gaurdrails etc.

Nice kart though.
Clearly a 48V etek is more than enough power to get you into trouble.
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Post by Thalass » Thu, 15 Jan 2009, 12:15

That's awesome. This will be my second project! (though it'd be more logical to have it as the first one. heh)
I'll drive an electric vehicle one day.

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Post by Dicko » Thu, 15 Jan 2009, 15:19

Hi guys.

Here are the specs that I think we should go with on the mechanical side of things:

1. Any chassis used should conform to FIA specs and be suitable for either the local J or S class of Karting (free manufacturer).
2. Tyres should be Dunlop SL1 (hard and durable), this could be changed later if more grip is needed.
3. Single rear sprocket drive (free ratios).
4. Solid rear axel.
5. Single rear brake disk (free manufacturer).
6. Front wheel steer only.
7. No suspension systems except the natural chassis flex.
8. Min and Max kart weights to be decided upon later.
9. Open total weight (kart and driver).

Here are a couple of links to European EKart sites. It seems most Karts are running 48v but some eligible for the FIA Alternative Energies Championship are running 72v.

http://www.gravitron.co.uk/html/electric_vs_petrol.html

http://www.kartelec.com/f/en_acceuil.htm

I hope this helps. If there are any areas I have overlooked, let me know and I’ll sort it.

Cheers.

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