Direct Drive: Do I have enough torque?

Technical discussion on converting internal combustion to electric
fuzzy-hair-man
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Direct Drive: Do I have enough torque?

Post by fuzzy-hair-man » Tue, 09 Dec 2008, 21:36

Hi,

I'm toying with the idea of an electric mini using direct drive AC, and I was trying to work out how you decide if you have enough torque to take off.

I figure that taking off in an ICE by slipping the clutch is just letting the revs stay at a level where the engine is producing enough torque to take off without stalling, ie there is no mechanical advantage to slipping the clutch in fact it would waste energy as heat. Am I correct in this thinking?

So if I had a AC motor producing similar peak torque to the ICE and I can take off by slipping the clutch in the ICE then I should also be able to take off with a similar gearing using the AC motor right? Image

Here's the problem though I'd be certain that I could take of in 2nd using the ICE (overall gearing ~ 6:1) but I can only find suitable size diffs to about 5.3:1 (Daihatsu Rocky or Suzuki Sierra) which puts the gearing somewhere between 2nd(6.5:1) and 3rd(4.6:1).

Working out 0-100km times and it actually makes it marginally quicker with a 5.3:1 diff than it does with a 6:1 diff but I don't think that tells me if it will be able to get moving in the first place. I'm not certain about these numbers either, could someone run some through their calculators to confirm?

So how do you get an idea of what sort of direct drive gearing will suit?

PS: using the original gearbox is out because I don't think it would survive as they're weakish already and the mini gearbox might present troubles to try to connect to an electric motor, because the motor would need to sit on top of the gearbox.

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Direct Drive: Do I have enough torque?

Post by Richo » Wed, 10 Dec 2008, 01:46

fuzzy-hair-man wrote:...ie there is no mechanical advantage to slipping the clutch in fact it would waste energy as heat. Am I correct in this thinking?

Yep.
At 0kph the motor is 0rpm.
There is no need to slip the clutch or even use it at take off.
The only time you would want to use the the clutch is to change gears.
When you hit the accelerator you should get full torque basically from 0.
fuzzy-hair-man wrote:
So how do you get an idea of what sort of direct drive gearing will suit?


Best way is to run the numbers through a prupose built calculator.
Other factors need to be included such as:
Torque vs RPM.
Max RPM -> top speed of car
Ability to climb hills from start
physical losses such as Wind resistance/aerodynamics
weight of car after conversion.

Generally the best way is to oversize the motor so it produces a similar torque at the diff as if it was using a gearbox in first gear.
That way you can leave the diff as it is.
Obviously if the motor has a higher rpm this would need to be taken into account.
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Direct Drive: Do I have enough torque?

Post by Goombi » Wed, 10 Dec 2008, 02:37

Unless one uses High speed motor   1-5000rpm your torque will only be strong if you pump High amperage through controller and i am talking 300-450 amp. There is a lot of power loss and voltage amp loss.
My motor runs 1-2300rpm/ it is good to have a gearbox and i never use high amperage usage. Max 200amp There is no hill that i cannot get up. and mostly second gear. its nice to see the car travelling at low consumption in 5 th gear. and i can keep up comfortably with the traffic.

If you were to be more speciffic about what type motor -dimension and voltage you will use. I know someone else that is coupling e.motor to diff. i will report of the result soon..
Not sure if AC system will do any better ?
Last edited by Goombi on Tue, 09 Dec 2008, 15:42, edited 1 time in total.

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Direct Drive: Do I have enough torque?

Post by fuzzy-hair-man » Wed, 10 Dec 2008, 03:18

Richo wrote:
fuzzy-hair-man wrote:...ie there is no mechanical advantage to slipping the clutch in fact it would waste energy as heat. Am I correct in this thinking?

Yep.
At 0kph the motor is 0rpm.
There is no need to slip the clutch or even use it at take off.
The only time you would want to use the the clutch is to change gears.
When you hit the accelerator you should get full torque basically from 0.
Sorry I was talking about the ICE here, Image I'm trying to get a handle on what to expect from an engine delivering full torque at 0 revs (never having driven one) and what this would mean for direct drive gearing, most conversions that keep the gearbox end up using 2nd and 3rd gear right? and the engine I'm looking at (AC24LS) develops similar torque and power to the 1275 mini A series, so I should be OK for power and torque it's just a matter of what gear to direct drive with and if I can get rid of the gearbox.

AC24LS Specs
Richo wrote:
fuzzy-hair-man wrote:
So how do you get an idea of what sort of direct drive gearing will suit?


Best way is to run the numbers through a prupose built calculator.
Other factors need to be included such as:
Torque vs RPM.
Max RPM -> top speed of car
Ability to climb hills from start
physical losses such as Wind resistance/aerodynamics
weight of car after conversion.

Generally the best way is to oversize the motor so it produces a similar torque at the diff as if it was using a gearbox in first gear.
That way you can leave the diff as it is.
Obviously if the motor has a higher rpm this would need to be taken into account.

The maximum torque for the AC24LS is 90Nm and the 1275 is about the same but I have a 998 mini with ~70Nm and it takes off OK. I doubt I'd generally take off with the 3000 rpm that it would need to produce that torque so the torque I need to take off is probably somewhat less. The AC24LS revs up to 11000 revs but by then it's run out of puff if I geared it using the 1st gear and standard diff I'd have a ~ 11:1 ratio but I think I'd run out of revs pretty quickly, so the lower I can make the ratio the better my top speed can be (assuming direct drive) and generally the better 0-100 time (according to the spreadsheet I used) because it hasn't entirely run out of puff before 100km/hr.

The calculator I used was the spreadsheet here (I tried to do my own but it seemed to go too fast Image):
EV calculator

I tuned the times to the power the motor would put out at given revs to get a 0-100 time of just under 10 secs but I'm not good at physics etc so I don't have much confidence in that.

The numbers used were:
0.53 Co efficient drag
1.5m2 frontal area
Max RPM ~ 8000 - 9000
Desired top speed around the 100km/hr
Weight after conversion: ~710kg without the people. (638kg starting weight less almost 200 - 250kg ICE etc + 40 motor + 15kg controller + 250kg batteries with some other bits in there as well.)
Wheel radius 0.24m (10 inch wheels Image )

I'd rather not have to push it up hills Image What's a usual grade of hill? I have 5 - 10% floating in my head but I don't know where it came from...

It's a front wheel drive so I think the standard diff is no use.
Last edited by fuzzy-hair-man on Tue, 09 Dec 2008, 16:22, edited 1 time in total.

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Direct Drive: Do I have enough torque?

Post by acmotor » Wed, 10 Dec 2008, 05:26

Rule 1.
If you need a gearbox then the emotor isn't big enough.
A gearbox can make a small motor or one with an unfriendly torque curve work in an EV.

Rule 2.
See rule 1.

If you can climb 15deg (slowly) that will cover most situations.
If you can hold 60kmph on 10 deg you are doing fine.
If you can accelerate from any speed on 5 deg that is good.
What is Black Mountain, 10deg ?

In direct drive I find I need 300+Nm to do a reasonable acceleration take-off up a 10deg slope, but only half that to just move off.
1100kg EV, 6.5:1 to rear 15" wheels.

Emotors don't run out of puff with revs, you just run out of voltage to puff them !

AC24 at 90Nm sounds a bit light on for direct drive. Some additional ratio would be required to get the revs up. The 10:1 gearbox offered sounds good.
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Direct Drive: Do I have enough torque?

Post by Richo » Wed, 10 Dec 2008, 07:00

With the AC24LS in wye mode and using around 8.8:1 diff 0-100kph would be still be around 12.2secs.
And your top speed would be 100kph@11000RPM.
Sounds like a lot of revving for not much action.

If you kept the gearbox the AC24LS sounds ok.

A suitable industrial AC motor would be a 11kW 4-pole 132-frame.
But it would have to be re-wound for 200Vac.
So running 400Vac (approx 220 lithium batteries) system it would give:
210Nm Peak 0-3000RPM (Torque rolls off above 3000RPM)
22kW cont / 66kW peak
60kg
Using a 3.44:1 diff direct drive to the motor would get 0-100kph in 10secs.
(based on the data you provided)
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Direct Drive: Do I have enough torque?

Post by woody » Wed, 10 Dec 2008, 20:10

fuzzy-hair-man wrote: I figure that taking off in an ICE by slipping the clutch is just letting the revs stay at a level where the engine is producing enough torque to take off without stalling, ie there is no mechanical advantage to slipping the clutch in fact it would waste energy as heat. Am I correct in this thinking?
I'd go with that, but add if your clutch slipping results in the RPMs dropping then you are trading some of the kinetic energy from the flywheel + engine for torque too - the extreme version of this dropping the clutch at redline.
fuzzy-hair-man wrote: So if I had a AC motor producing similar peak torque to the ICE and I can take off by slipping the clutch in the ICE then I should also be able to take off with a similar gearing using the AC motor right? Image
Sounds good to me.
fuzzy-hair-man wrote: Here's the problem though I'd be certain that I could take of in 2nd using the ICE (overall gearing ~ 6:1) but I can only find suitable size diffs to about 5.3:1 (Daihatsu Rocky or Suzuki Sierra) which puts the gearing somewhere between 2nd(6.5:1) and 3rd(4.6:1).

Working out 0-100km times and it actually makes it marginally quicker with a 5.3:1 diff than it does with a 6:1 diff but I don't think that tells me if it will be able to get moving in the first place. I'm not certain about these numbers either, could someone run some through their calculators to confirm?
I don't think stopped is a special case as far as acceleration goes.
As a bonus, the danfoss drive and presumably others can boost the torque at low speed above the peak torque of the motor to give you a head start. This lets acmotor get 337Nm from his 11kW motor at low speed, which is way more than you need.

Based from these
Specs , I reckon with:

Rolling Mini with Sierra Diff (450kg?)
ABB 4 pole 11kW 132 frame motor rewound for ~175 Volts (59 kg)
Danfoss 5042 controller (44 kg)
224 EVPST 2882118 12 Ah batteries (112kg)

Should have enough torque/power to do:
0-100 in 10s
400m in 17s
100km range at 65km (80% DoD as recommended)
Pack should last ~ 150,000km (1500 cycles)

Assuming you don't break anything.

The AC industrial motors don't get much smaller than that in weight and still give enough power/torque for a car.

Another guy has done a DC conversion using a Suzuki Swift gearbox, that may be suitable for the AC24 motor + drive combo (AU$8K before the dollar dived).

The AC24 torque curve is flat at ~74Nm up to 4500 rpm:
Image

I prefer the industrial setup.
fuzzy-hair-man wrote:
So how do you get an idea of what sort of direct drive gearing will suit?

PS: using the original gearbox is out because I don't think it would survive as they're weakish already and the mini gearbox might present troubles to try to connect to an electric motor, because the motor would need to sit on top of the gearbox.
I have a spreadsheet which I use which I put in the vehicle info and then jigger about with these variables:
1) Motor (from about 10 ABB models)
2) Motor Nominal Voltage @ 50Hz which affects nominal current etc.
3) Diff Ratio
4) Cell Model (e.g. Thundersky LFP40AHA, EVPST, Greensaver)
5) Number of Batteries I.E. pack voltage
6) Controller Model (e.g. Danfoss, Telemecanique, Lenze)

Just about all of the above affect weight which affects rolling resistance + acceleration, they also affect the torque curve of the motor through different limitations (Controller Motor Current, Battery Current, Cell Equivalent Series Resistance - ESR)

I muck around with those 6 things while watching the resulting 0-100 time and 400m time.

Of course I haven't got the whole picture, I reckon acmotor's Red Suzi should do 0-60 in 13s and he reckons it only takes 6-7s.

I haven't got anything to model the danfoss torque boost, which obviously makes a big difference.

Whichever way you go, you should be better than original 0-100 in 29.7 seconds :)

cheers,
Woody
Last edited by woody on Wed, 10 Dec 2008, 09:19, edited 1 time in total.
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Direct Drive: Do I have enough torque?

Post by woody » Wed, 10 Dec 2008, 20:23

Not a lot of room in there:

Image

:-)
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Direct Drive: Do I have enough torque?

Post by Goombi » Wed, 10 Dec 2008, 20:50

Am I noticing that everyone is sidestepping the principle for conversion?
We are all now talking about 0-60km/h in 6 sec 400 m in 17 sec-- What the in the hell does it matter? Safety- general performance on par with ICE and distance are the prerequisites for conversion..
All this talk is a distraction from the real thing --Convert and Drive.
There is alo enough confussion about and the ones that are now driving their cars are best qualified to express their opinions and share their experiences.. Please separate the DC from AC in another website Folder
New folks that are contemplating conversion are confused   which way to go AC or DC-- and in a long run will abandon the project. In the meantime i am running happily with my Barina all over the town saving money and spreading the word that it is easy to convert and not confusing.   High School demo's is now booked for next year to infect the young brains with alternative driving power. Kill the wroom wroom's

One more small item. Motors that run to 10.000 revs/min.
What is the purpose for such speed. If the motor was coupled to gearbox it will run the gearbox at twice the allowable speed and demolish it in no time. Motors that run at 10.000 rpm will need special bearing cooling.. Motors running at 2959rpm are safe and proven performers.
All this talk is experimental-- that is not needed. we need positive IDEAS. Honestly lads it does not help... Perhaps this chatroom has evolved a bit higher and is no longer beneficial for newcomersand newbeas
Last edited by Goombi on Wed, 10 Dec 2008, 10:14, edited 1 time in total.

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Direct Drive: Do I have enough torque?

Post by Johny » Wed, 10 Dec 2008, 21:18

I know I talk about these subjects a lot because an EV is a sizable investment in time and money. The more I discuss with others and read threads like this one, the less likely I am going to end up with a costly mistake. If done correctly, the improvement from modest to good performance does not appear to be much more costly to implement.
The original creator of this thread stated using an AC motor, you are the only post mentioning DC.
This thread is interesting guys - keep it up!

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Direct Drive: Do I have enough torque?

Post by woody » Wed, 10 Dec 2008, 21:32

Hi Goombi,

I agree with you in principle, don't bamboozle people with technical stuff.

In this case fuzzy-hair-man was already looking at AC, asked for calculations, already talked about torque and power conversion, so hopefully I've given him what he wanted :-) (he may correct me on that!)

We all have different goals and enjoy doing things differently. Your conversion is perfect for you, I would not be happy with it for me.

So your prerequisites are different for mine and others. We're all different, which is why White Zombie and other extreme conversions have been built.

An EV is something you're going to driving for years for it to be successful, so a car which you're happy to be driving for years is a sensible prerequisite.

Safety is not a factor for many people (e.g. motorcyclists)

Distance/Range depends on the person, some people need 200km between charges, others only need 20.

Cost is less relevant for the wealthy. Up-front and ongoing (battery) cost are separate issues for different people.

Performance is a factor for many people, which is why many ICE cars have a choice of engines and there are cars on the road which do 0-100 in 3 seconds and some which take 30 seconds, and some which never get that fast.

I think it's important to be a bit faster than original simply so that people don't have the negative in their mind that EVs are slower.

Anyway, we're all on the same team, but we're not all the same :-)

cheers,
Woody
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Direct Drive: Do I have enough torque?

Post by acmotor » Wed, 10 Dec 2008, 21:33

It is all done by wires and magnetism either way !
Image
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Direct Drive: Do I have enough torque?

Post by Richo » Wed, 10 Dec 2008, 21:34

Goombi wrote: Am I noticing that everyone is sidestepping the principle for conversion?
We are all now talking about 0-60km/h in 6 sec 400 m in 17 sec-- What the in the hell does it matter?
Well he is asking about AC direct drive.
The motor he asked about is too small to work.
The next size up is the ones we have discussed.
As a down side he will go much faster.
As we have pointed out the motors don't come smaller than what we have suggested.
Goombi wrote: Safety- general performance on par with ICE and distance are the prerequisites for conversion..
Everyone has different opinions as to thier prerequisites for conversion.
Goombi wrote: All this talk is a distraction from the real thing --Convert and Drive.
Nop - he is planning which is a valid step to getting what he wants.
Goombi wrote: There is alo enough confusion about and the ones that are now driving their cars are best qualified to express their opinions and share their experiences..
Everyone has equal right here to express opinions.
Goombi wrote:Please separate the DC from AC in another website Folder

He is contemplating an AC conversion.
So your DC currents in your conversion are not relevant to this thread.
Goombi wrote: Motors that run at 10,000 rpm will need special bearing cooling..

Maybe you should read the spec sheet fot the motor he has discussed.
It is designed for this RPM.
It does not need special anything.
It has a gearbox available for it as well.
Goombi wrote: Motors running at 2959rpm are safe and proven performers.
2959RPM is very specific.
Are the ones going 2960RPM bad?
Goombi wrote: All this talk is experimental-- that is not needed.

AC in not experimental.
Azure motors and controllers have been around for a while.
Industrial AC motors have been around for even longer.
Danfoss controllers have been around for longer than any cheap chinese controller in any DC eV.
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Direct Drive: Do I have enough torque?

Post by Goombi » Wed, 10 Dec 2008, 21:49

Good luck RICHO ...../...../

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Direct Drive: Do I have enough torque?

Post by fuzzy-hair-man » Wed, 10 Dec 2008, 23:48

Thanks guys

Goombi, I do have AC in mind for a couple of reasons:

regen.
higher revs particularly on this motor seemed useful especially for direct drive, I might be wrong here though...
high efficientcy.
Little or no maintenance.
I'm also impressed by the robustness and reliability (water sealing etc) of AC motors.
I'd like to get rid of the gearbox, because the mini one probably won't take it and I'd rather avoid trying to put in a gearbox out of a different car (although this might not work out).

A high reving motor looks to deliver more power in a smaller lighter package, for example the Solectra AC55 delivers 3 x as much torque but only 12kW more power and weighs more than twice as much.

But I'm not good electrically or with physics so I don't get a lot of the stuff about VFDs and pullout torques etc so this is why I've tended towards the Solectra stuff...

I think people end up talking about 0-100 times etc because they want to know what they are getting, I don't want to spend a heap and put the effort into a conversion without knowing what I'll end up with. I had AC in mind before I ever found this board so I haven't been swayed although cost is an obvious issue.

This is all really window shopping (so whilst cost would need to be reasonable I'm not buying at the moment, sorry if this means I've wasted anyone's time) I might someday get to do it but for the moment I'm trying to understand and I have trouble getting my head around it and the practicalities of getting peak torque from zero, ie what it means to drive without a clutch. I was hoping that the slipping clutch example might be able to help other people as well decide/understand which motor size and torque might best suit their application.

Thanks Woody you confirmed what I was thinking, and I understand what you mean about the flywheel and dumping the clutch, I had left that bit out...Image

I'm still a little confused why everyone says the motor is too small though I mean the Mini Cooper S (not the 850) has peak torque of ~90Nm and makes and 57kW this is not that far from what the AC24LS(90Nm and 47kW) (not AC24 they increased the torque in the LS model) I figure I should get some advantage from generating torque from zero so should be able to drive a steeper gear than the ICE. The Cooper S does 0-100 in something like 12sec and ideally this would be the performance I'd be aiming for but I have a 998 (41kW and 71Nm) and it's extremely usable especially around town. <edit> I guess it comes down to could I do a clutch type start in 2nd gear up a 10% or 15% hill... that might be asking a bit much... Image I'll have to try sometime </edit>

Blade EV's Electron looks to use the AC24 and I'd place bets that the Getz is heavier than my mini, so it seemed to me a matter of finding the right gear or perhaps (but hopefully not) gears.

You're right Woody there's not much room in there, I've been sticking my head under Sierras lately to look at the diffs (and getting strange looks) and I'm not sure there would be room for both the diff and AC24.... maybe I'll have to look at other options. I found this guys mini too Mike Laba's Mini. I think I've used the back seat in my mini once for people so getting rid of the back seat and putting batteries in there would be an option too, another option for batteries would be cutting out the boot floor for a battery box but I figure that comes later. Image

acmotor: Not sure what the grade of Black Mountain is I rode my pushbike up there once and haven't done it again so by that measure I guess it's pretty steep. Image Thanks for the advice re grades I've tried plugging grades into the calculator but with a 7:1 it tells me (I think) that I could go up a 15% grade at 90km/hr (the spot where the power required to maintain speed equals the power produced right?)... I don't think I believe it.

Where do you find specs on these ABB motors? I found there website but I find it sort of incomprehensible.
Last edited by fuzzy-hair-man on Wed, 10 Dec 2008, 13:43, edited 1 time in total.

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Direct Drive: Do I have enough torque?

Post by Richo » Thu, 11 Dec 2008, 01:36

As I already said the AC24LS would get you 0-100kph in around 12secs.
That's with 8.8:1 diff ratio and top speed of 100kph.
ie 100kph=11000RPM.

So it would go.

Obviously if you dropped the diff ratio down your top speed would go up
but your 0-100kph time would drop to something more like 15-20secs.

I guess it depends if you want something that goes or something that GOES Image

Abb motors
see the catalogues.
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Direct Drive: Do I have enough torque?

Post by KDRYAN » Thu, 11 Dec 2008, 01:37

On the subject of diffs that may suit your needs. Daihatsu Terios front diff 5.3:1 alloy housing (light)and very short from drive flange to axle centre.

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Direct Drive: Do I have enough torque?

Post by Johny » Thu, 11 Dec 2008, 18:31

I think the meaning behind "too small" is that without a gearbox you really do only have motor torque to get you off the mark. The petrol Mini with 90NM of torque has that multiplied by the gear box ratios. First gears tend to be nearly 4:1 which means 360NM of torque (at peak revs and dropping clutch).

Going direct drive means a compromise between starting (and low end) torque, high end torque and motor weight.
I.e. Select the lightest motor that gives you acceptable performance.
But there are fiddles you can do to the motor...

There is a complicated thread where we procrastinate about AC motors and rewinds and such but I agree it's got a bit complex. Even as I plan my conversion and buy bits and pieces now - it's not turning out like a kit. It's difficult, so I understand why you may not want to go that way. The saving part is has the capacity to be a LOT cheaper with a better result than a commercial semi-kit approach.

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Direct Drive: Do I have enough torque?

Post by EV2Go » Fri, 12 Dec 2008, 01:27

Hey FHM I would probably take another look at your base figures, my 78 model clubman with a 1275cc (1360cc bored and stroked) was 660kgs without me and the motor isn't that heavy.

Long time since I owned the mini but fairly sure while I was rebuilding the motor and gearbox I lifted the whole lot up by myself so it cant be anywhere near 200kgs.

Did you get to the AEVA field day? there was a very neat mini conversion there (photos around here somewhere).

It is a little hard to compare a motor with an ICE when it comes to power and torque figures.

Still dont know how you can have peak torque at 0 rpm, if the motor isnt turning how can it possibly be producing torque. I must be superman because I can hold the shaft from turning at 0 rpm :) I digress...

e-motors are generally going to be a compromise when it comes to top speed compared to the equivalent ICE by their very design, but for simplicity of fit using a gearbox like the one out of a Suzuki makes the most sense.

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Direct Drive: Do I have enough torque?

Post by zeva » Fri, 12 Dec 2008, 01:46

EV2Go wrote: Still dont know how you can have peak torque at 0 rpm, if the motor isnt turning how can it possibly be producing torque. I must be superman because I can hold the shaft from turning at 0 rpm :) I digress...

Torque can be thought of just like rotational force.. So maybe easier to think of it in linear terms. e.g if you try to push a Mack truck it probably won't budge, but you are still pushing i.e applying a force. Power on the other hand is indeed necessarily zero at 0rpm, since power is velocity x force (or rotational velocity x torque).

In physics lingo you're not doing any "work" unless the object you're applying the force to is actually moving. And "power" and is the rate of the "work".

If you can hold your EV's motor from turning yes you must be superman - or maybe there's something wrong with your motor/controller Image because if you can stop it turning, it surely won't have enough torque to get your car moving!
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fuzzy-hair-man
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Direct Drive: Do I have enough torque?

Post by fuzzy-hair-man » Fri, 12 Dec 2008, 02:08

EV2Go wrote: Hey FHM I would probably take another look at your base figures, my 78 model clubman with a 1275cc (1360cc bored and stroked) was 660kgs without me and the motor isn't that heavy.
That's cause a clubby is heavier than a roundnose Image

Here's what I figured roughly:
Original weight (I couldn't remember but found it somewhere)
635kg(rubber cones..)
Engine 100kg
Gearbox 50kg (I found a website that suggested these were 150kg not sure how much of the accessories it included)
exhaust 10kg
fuel tanks 25ltrs each so 50kg.
radiator + fuilds 10kg
alternator 3kg
starter 3 kg
battery 15 kg
giving 241 kg loss.
If you assume the 150kg included the accessories add 16kg back on....

Electric bits to add (found weights at various spots round the web):
Motor 40kg (specs)
Controller 15kg (specs)
charger 5 kg
DC DC Converter 2kg
small 12 battery 1kg (not sure if it'd be big enough but could also use DC-DC without)
EV2Go wrote: Long time since I owned the mini but fairly sure while I was rebuilding the motor and gearbox I lifted the whole lot up by myself so it cant be anywhere near 200kgs.
I can lift the block and crank by itself and I can lift the gearbox by itself but it took myself and my brother to move the engine and gearbox (with alternator and starter) together.
EV2Go wrote: Did you get to the AEVA field day? there was a very neat mini conversion there (photos around here somewhere).

It is a little hard to compare a motor with an ICE when it comes to power and torque figures.

Still dont know how you can have peak torque at 0 rpm, if the motor isnt turning how can it possibly be producing torque. I must be superman because I can hold the shaft from turning at 0 rpm :) I digress...

e-motors are generally going to be a compromise when it comes to top speed compared to the equivalent ICE by their very design, but for simplicity of fit using a gearbox like the one out of a Suzuki makes the most sense.
No, I didn't get to the field day, I'm restricted to Canberra at the moment. That mini does look nice!

The way I figure is performance above 100km doesn't really worry me it'd just get me in trouble but less than that and around corners(handling) is where it's useful. Image something between 998 and 1275 performance would be good.

If I can get away without a gearbox it would be good because they would seem to only add weight complexity and inefficientcy that is provided the motor can do what's required.

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EV2Go
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Real Name: Paul
Location: Brisbane 1963

Direct Drive: Do I have enough torque?

Post by EV2Go » Fri, 12 Dec 2008, 02:18

zeva wrote: In physics lingo you're not doing any "work" unless the object you're applying the force to is actually moving. And "power" and is the rate of the "work".
Well if I stood at the front of a Mack truck and pushed my guts out it would sure feel like I was doing some "work" even if the truck wasn't moving Image
zeva wrote: If you can hold your EV's motor from turning yes you must be superman - or maybe there's something wrong with your motor/controller Image because if you can stop it turning, it surely won't have enough torque to get your car moving!
I reakon at 0 RPM I could hold it from going anywhere, wouldn't make the same statement at 1 rpm though Image

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EV2Go
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Real Name: Paul
Location: Brisbane 1963

Direct Drive: Do I have enough torque?

Post by EV2Go » Fri, 12 Dec 2008, 02:38

fuzzy-hair-man wrote:
EV2Go wrote: Hey FHM I would probably take another look at your base figures, my 78 model clubman with a 1275cc (1360cc bored and stroked) was 660kgs without me and the motor isn't that heavy.
That's cause a clubby is heavier than a roundnose Image

Here's what I figured roughly:
Original weight (I couldn't remember but found it somewhere)
635kg(rubber cones..)
Engine 100kg
Gearbox 50kg (I found a website that suggested these were 150kg not sure how much of the accessories it included)
exhaust 10kg
fuel tanks 25ltrs each so 50kg.
radiator + fuilds 10kg
alternator 3kg
starter 3 kg
battery 15 kg
giving 241 kg loss.
If you assume the 150kg included the accessories add 16kg back on....

Electric bits to add (found weights at various spots round the web):
Motor 40kg (specs)
Controller 15kg (specs)
charger 5 kg
DC DC Converter 2kg
small 12 battery 1kg (not sure if it'd be big enough but could also use DC-DC without)
EV2Go wrote: Long time since I owned the mini but fairly sure while I was rebuilding the motor and gearbox I lifted the whole lot up by myself so it cant be anywhere near 200kgs.
I can lift the block and crank by itself and I can lift the gearbox by itself but it took myself and my brother to move the engine and gearbox (with alternator and starter) together.
EV2Go wrote: Did you get to the AEVA field day? there was a very neat mini conversion there (photos around here somewhere).

It is a little hard to compare a motor with an ICE when it comes to power and torque figures.

Still dont know how you can have peak torque at 0 rpm, if the motor isnt turning how can it possibly be producing torque. I must be superman because I can hold the shaft from turning at 0 rpm :) I digress...

e-motors are generally going to be a compromise when it comes to top speed compared to the equivalent ICE by their very design, but for simplicity of fit using a gearbox like the one out of a Suzuki makes the most sense.
No, I didn't get to the field day, I'm restricted to Canberra at the moment. That mini does look nice!

The way I figure is performance above 100km doesn't really worry me it'd just get me in trouble but less than that and around corners(handling) is where it's useful. Image something between 998 and 1275 performance would be good.

If I can get away without a gearbox it would be good because they would seem to only add weight complexity and inefficientcy that is provided the motor can do what's required.


Mine had the rubber cones as well not the hydrolastic.
I really think the motor would be pushing to weigh 100kgs more like 80kgs maybe
Gearbox has an alloy case doubt it wouldn’t weigh more than 30kgs with the diff, who ever said 150kg must be dreaming Image
As I said I am fairly sure I picked up motor and gearbox together and moved it.
Exhaust might weigh 4 or 5
Duel fuel tanks were only on a few of the Coopers there not a standard item and fuel weighs about .7kg per litre, the tanks weigh nothing there like a big tin.
Rest might be fairly close

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Mesuge
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Direct Drive: Do I have enough torque?

Post by Mesuge » Fri, 12 Dec 2008, 11:12

KDRYAN wrote: On the subject of diffs that may suit your needs. Daihatsu Terios front diff 5.3:1 alloy housing (light)and very short from drive flange to axle centre.


Thanks for the tip, some more info:
http://en.wikipedia.org/wiki/Daihatsu_Terios
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fuzzy-hair-man
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Posts: 118
Joined: Wed, 12 Nov 2008, 16:40
Location: Canberra

Direct Drive: Do I have enough torque?

Post by fuzzy-hair-man » Fri, 12 Dec 2008, 16:56

Mesuge wrote:
KDRYAN wrote: On the subject of diffs that may suit your needs. Daihatsu Terios front diff 5.3:1 alloy housing (light)and very short from drive flange to axle centre.


Thanks for the tip, some more info:
http://en.wikipedia.org/wiki/Daihatsu_Terios



Yeah thanks Kdryan that's a good tip I'll check them out. Image

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