DIY Electric Car Forums banner
181 - 200 of 368 Posts

·
Administrator
Joined
·
6,370 Posts
Discussion Starter · #181 ·
Hi
I started off with batteries from China - nothing like as good as the Volt Pack and more expensive!

There is a local Hot Rod importer company that ships stuff over from the USA - my Volt pack cost $3,300 NZ all up - GST, transportation - the lot

They have also got a pack for a guy in Rolleston - dunno how he is doing

I would strongly recommend getting a Volt (or Leaf) pack

With FWD then you are stuck with using the gearbox - that does give you more choice and you won't need a reversing contactor

How much space have you got? - you may need to apply some violence to the inner wing to make space for the motor
 

·
Registered
Joined
·
14 Posts
Thanks Duncan, the motor should fit in the gap, it sort of depends on how far the shaft of the motor goes into the bell housing and whether I need to space out the adapter plate, I will be taking the old engine out in the next couple of weeks and will know more once I see the inside. Is the local hot rod guy Charlton in Gore by any chance?
Did you assemble the controller yourself or buy it ready to plug in?
 

·
Administrator
Joined
·
6,370 Posts
Discussion Starter · #183 ·
Charlton are the guys!
I bought my two post hoist off them as well

I assembled my first controller - learnt a great deal - and managed to blow it up!
Then I got another one (or at least new boards)(kept the rest of the hardware) - went really well until Paul (of Paul & Sabrina) offered me a beta version of his High Voltage High Current Controller
That's what I'm running now
340v and 1200 amps
 

·
Administrator
Joined
·
6,370 Posts
Discussion Starter · #185 ·
Yep!
I gave it 8 degrees advance - which is about the most you want to give

As your DC motor spins you get back EMF - this is basically proportional to current and rpm
At 3500 rpm and 200 amps - I was getting about 110v Back EMF - and this current was what I needed to drive at that speed -100Kph

With 144v - I was able to reach 115Kph - 4000rpm

With 340 v - I can pull 1200 amps until my controller maxes out - then I am just on the battery

It feels as if it is still accelerating hard at about 135 Kph at the end of the 1/8th - 4700 rpm
It does not feel as if I have maxed the controller out - if anything it felt like it was really lifting it's skirts and flying then!

Am I being cruel to my motor?? I suppose I am - but it seems to be a tough old beast
 

·
Registered
Joined
·
6,997 Posts
Remember to keep all four wheels on the ground.
:D

Many cars do lift one wheel in extreme cornering. It's not desirable, but may result from excessive roll stiffness bias toward the end which lifts, due to an attempt to manage other chassis problems. It may be the lesser of two evils.

On the other hand, it is the non-driven end which lifts a wheel in any reasonable vehicle: the rear in many front-wheel-drive cars (VW Rabbits/Golfs were known for this), and the front in some rear-wheel-drive cars (most commonly Porsche 911, but I've heard of it in BMWs and I'm sure it happens to a lot of cars). Lifting a wheel at the driven end (such as the rear of that Fiero) indicates a chassis setup problem... or at least that it's doing something for which it was not set up. ;)

Even if you have an aggressive limited-slip differential - so you don't spin a wheel out of control - lifting a driven wheel is generally still not good. On the other hand, with separate left and right drive motors or no differential, it can work - karts (with no differential) routinely depend on completely unweighting the inside rear wheel on corner entry to get them to turn.

And of course, sometimes one wheel comes up because of a bump (usually a curb), not indicating any problem.
 

·
Registered
Joined
·
1,664 Posts
Karts depend on lifting th e inside rear wheel for critical handling.
As they have basicly no suspension they rely on chassis flex and front end geometry (king pin inclination) to jack weight off the inside rear when cornering. Kart chassis set up is much more complex than most folk think, with many more settings to adjust than most amature tracck race cars.
Many of the best chassis tuners learnt their craft setting up and racing karts.
 

·
Administrator
Joined
·
6,370 Posts
Discussion Starter · #191 ·
Hi John
I am using the 8 year old tires that came with the wheels so I am a bit grip limited!

My last 1/8th I lost traction, lifted, then lost traction again - then it just went
I got 9.2 seconds and 87 mph

My cunning plan is to buy some nice sticky tires before next years drags

I would like to sort out some form of traction control - when it goes it goes fast - but not sure when I will be able to do that
 

·
Registered
Joined
·
551 Posts
I think Arduino is your friend. They can be made to do almost anything and at a reasonable price.

My initial thoughts are an input into the arduino from either:
a GPS module
a speedo (assuming the speedo isn't run off the driven wheels)
a G force meter

and another input from the tacho

Have the arduino do a mathmatical comparison of the two inputs. Set some limits (if x revs is between y and z kmph then thottle =100% otherwise throttle at 90%)

I think it's doable
 

·
Administrator
Joined
·
6,370 Posts
Discussion Starter · #193 ·
Hi Galderdi
That was my plan - I'm a complete novice at electronics but I have an arduino kit in the attic awaiting the traditional "round tuit"

I was worried that some people have said that the arduino is no use in an EV because of the electromagnetic environment

I was going to ask - arduino - or what??

But first I need to replace the ABS tone wheels That I used to have on each corner before an attack of stupidity made me remove them
 

·
Registered
Joined
·
551 Posts
I am a novice too but I have successfully programmed one to control my reversing contactor so my confidence is building.

My next task is to build a better timing system for our club. That is massive by comparison. But I plan to just take it one requirement at a time and then string them all together.

I would understand a recommendation not to place it within a couple of feet of the motor. But other than that I can't see why arduino electronics would be any different from all the other electronics we have in our EVs. Any any way, even if it were an issue, you could alway build a little faraday cage around it.

It is a good point though. I think I should program up some way to test the impacts. Any thoughts on a suitable test?
Maybe have 2, one in the EV and one away from the EV both with the same timer program both triggered from the same switch so they are syncronised at the start. then drive around for a while. If they remain in sync then I would assume there hasn't been any significant disruption.
 

·
Administrator
Joined
·
6,370 Posts
Discussion Starter · #195 ·
I have been "invited" to a burnout competition

I can put a switch in my brake/throttle isolater so that I can use the front brakes

Do you have any idea what happens if I'm spinning my back tires? - what happens to the revs?

I'm worried that if I just keep the foot down I will over rev -

Any ideas?

My controller does not have a rev limiting feature
 

·
Registered
Joined
·
1,615 Posts
My experiences from the dark ages of the '60s when everything was mechanical:

You get on it hard until they light, the onboard mark 2 visual monitoring system observes tach readout and causes the lower right throttle servo to back off a touch. Feedback loop increases throttle as tires warm up and get sticky and decreases throttle as rpms get near redline.

If the programmer did his job properly selecting proper gear, rpms dont go insane. Really shouldn't go above 3/4 throttle.
 

·
Registered
Joined
·
1,469 Posts
LOVE your stickers Duncan! So cool!

I have a sign hanging up on the inside of the hood for when I go to car shows (bonnet is always open at those, to draw the bewildered stares!) It contains this picture I stole from the internet, and says, "Warning- best to keep hands OFF the electric bits"

Motor vehicle Traffic sign Yellow Vehicle Car


I didn't feel the need to add the other warning I read somewhere which I really liked: Warning: do not touch. Not only will this kill you, but it will hurt like hell the whole time you are dying"
 

·
Registered
Joined
·
1,469 Posts
Given that some people at shows with cars that are polished like a mirror have signs that say "do not approach this car unless you are naked", mine is pretty tame...my voltage is pretty low at around 108V nominal, and everything in my car is "finger safe" or I wouldn't be opening the hood around strangers- but a warning inside the hood can't hurt. And Duncan's sign is entertaining!
 
181 - 200 of 368 Posts
Top