Why standard GEARBOX for EV's

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Goombi
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Why standard GEARBOX for EV's

Post by Goombi » Thu, 18 Jun 2009, 16:47

Hi everyone,

Modern gearboxes are engineering marvel with synchromesh they can handle any Hp and torque. Gearboxes lifespan is anything up to 500.000km these small gearboxes for 1.5 litre motors   weigh around 20 kg.They are easy to repair and or replace.Gearboxes are a Most inportant part of EV conversion.
Direct drive is fine for limited top speed
2 speed gearboxes do not exist as such for cars and are also not effective for conversion. Why would anyone bother when all gears are already in the gearbox. You can use one gear or all gears. why be limited with alternative when all is there and free

Lets compare; how fast and with what power do you want to drive your EV on a car thrailer. First gear in your gearbox will do it.
Long steep hill or house drive First gear will do it.
How fast will EV go with 2800rpm rated motor with standard gearbox. in top gear
How fast will ICE go with 2800 rpm? in top gear( small car)
I estimate about 100Km/h. EV+ICE.
The basic difference between Ice and EV is relatively zero.
Conversions can only be made sucessfuly with gearbox and replace ICE motor with Electric motor. Simple and inexpensive.

So welcomre gearbox to the conversion world. There will be no successful conversion without you.

If gearbox was not necessary for Ice why do they make them?
If gearbox was not nesessart for EV why do we use them?

And i hope the Bullfrogs will agree

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One for the Government and one for the this planet








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woody
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Why standard GEARBOX for EV's

Post by woody » Thu, 18 Jun 2009, 19:13

My thoughts on the topic: other feel free to repost and add their own.

Why standard gearbox:
* front wheel drive & the diff is integral to the gearbox
* AC IM + DC Brush motor has a peaky power + efficiency curves - gearbox changes the road speed for motor speed
* Motor speed too fast for final drive ratio (e.g. AC24-LS)

Why not standard gearbox:
* motor is too torquey for gearbox and/or drivetrain through low gears
* gearbox is inefficient (85%-95% depending on gear) and motor is torquey enough to get away without it
* PMAC / BLDC motor has flat power band, making gearbox useless
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

Goombi
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Why standard GEARBOX for EV's

Post by Goombi » Thu, 18 Jun 2009, 19:33

Woody have you not forgotten the Controller for motor to be too Torquey
No more torque is tranfered to gearbox then if you rev. ICE and let clutch go. So El. motors are not too severe for gearbox. No El. motor has enough Oomph to go from 0 - 95 km/h without gearbox --unless you are using aircraft DC starter that goes to 11 000 rpm. I wouldnt like to live with that speed or its noise.
Build happy EV cars with gearboxes and you will do well..

And precisely this is not what i wanted to hear an argument and division. If one has no alternative that will do as good as job as a gearbox then one should keep quiet. There is no EV without gearbox. Amen

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woody
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Why standard GEARBOX for EV's

Post by woody » Thu, 18 Jun 2009, 20:20

Goombi wrote: Woody have you not forgotten the Controller for motor to be too Torquey
No more torque is tranfered to gearbox then if you rev. ICE and let clutch go.
Maybe. My Gearbox is tiny, ancient, I don't think it would last with 400Nm input when the original motor was 90. I'm very sure that the diff would not last with 1600Nm (400Nm x 1st gear 4:1).
Goombi wrote: So El. motors are not too severe for gearbox. No El. motor has enough Oomph to go from 0 - 95 km/h without gearbox --unless you are using aircraft DC starter that goes to 11 000 rpm. I wouldnt like to live with that speed or its noise.
Build happy EV cars with gearboxes and you will do well..
Mr Tesla will disagree. It goes 0-100 in <4 secs with no gearbox. But redline is 13000rpm. Very quiet.

Chrysler had 75,000 rpm motors in their turbine test cars in the mid 60s which they lent to families to test.

But if you are starting with a 100Nm motor then you'll need a gearbox to get the car moving quickly.

If you have a couple of 1000Nm motors, then you can put one on each wheel and not use a gearbox or diff at all, assuming the speed is fast enough (~900rpm for 100kph)
Goombi wrote: And precisely this is not what i wanted to hear an argument and division.
I'm not starting argument & division, I'm continuing your "General EV Discussion".

Different people have different needs. Mine and your needs are quite different, but EVs can satisfy both.

I think your concept will probably satisfy more people than mine (price & simplicity), but I don't think one EV design can satisfy everyone.

Discussion brings the info into the open, and people can make up their minds.
Goombi wrote: If one has no alternative that will do as good as job as a gearbox then one should keep quiet. There is no EV without gearbox. Amen
I disagree strongly with all of your last statement :-( I don't think it's the members' place in the forum to tell others to keep quiet. We each have the power to ignore or unsubscribe from the threads we don't want to read about.

cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

Andrew
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Why standard GEARBOX for EV's

Post by Andrew » Thu, 18 Jun 2009, 21:05

OK guys, these forums are open for free discussion. Under no circumstances will abuse be tolerated between members. If you wish to voice your opinion, that's fine, but keep your comments constructive and friendly. Let's keep this a happy community.

Thanks, and keep it real.

Andrew

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Richo
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Why standard GEARBOX for EV's

Post by Richo » Thu, 18 Jun 2009, 21:38

Goombi wrote:
So welcome gearbox to the conversion world.
There will be no successful conversion without you.


Go to the eValbum and do a search on "Direct Drive".
Are all of these conversions unsuccessful in your opionion?

Sure a front wheel drive car with a low conversion budget would suggest you use a gearbox.
No point changing what suits the purpose.
So the short answer is NO but the long answer is YES.
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Why standard GEARBOX for EV's

Post by Bluefang » Mon, 22 Jun 2009, 17:05

Realistically the standard gearbox from a car is kinda a waste for most EV conversions as you will only likely use 2gears at most, would be great to find a easily adaptable supply of cheap second hand 2 speed gearboxes with like a 1:1 and 2:1 ratio so you can have good acceleration around town to say 70km/h and a reasonable highway cruise RPM. I know the power used wont be much different but would allow a much smaller motor to perform well in a much larger variety of applications

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Why standard GEARBOX for EV's

Post by Goombi » Mon, 22 Jun 2009, 17:17

Buefang,
Do you honestly think that you will gain anything by using 2 speed gearbox with unknown addaptations to all cars for front wheel drives??? or diff drive at rear? What do you mean smaller motors? Larger variety of applications? you means less variety!!! You have excellent acceleratiobn with 5 speed gearbox sellect the gear you need.. what variery have you got with 2 speed --zilch-- Do you have a EV to make comparisons?

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Why standard GEARBOX for EV's

Post by Thalass » Mon, 22 Jun 2009, 18:02

You're already adapting an electric motor with unsuitable stud patterns to a gearbox built for a different type of machine with different a bolt pattern.

Certainly if you are sometimes going to be towing something heavy, or going off road, then a gearbox may be suitable. I've been considering it myself for the latter reason. But then again if I have two motors with 300nm of torque and two 1:4.1 diffs (one per motor) I don't think I'll need one, even off road up a steep slope of loose gravel.

Though I beleive there is another subaru brumby conversion in the eastern states using a dc motor and the existing drivetrain. So if I can do my conversion with 2x ACIM we could compare directly!
I'll drive an electric vehicle one day.

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EV2Go
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Why standard GEARBOX for EV's

Post by EV2Go » Sun, 12 Jul 2009, 19:59

It’s dangerous to make sweeping statements one way or the other, as the conversions are as different as the reason people do them.
To make an informed decision you have to first work out what it is you are willing to sacrifice to potentially gain in another area.
For example few would argue that direct drive simplifies a RWD conversion, by virtue of the fact there are simply less parts. There is no need to consider adaptors/ clutch plates / flywheels / parts to work if they are not required or present.
On the flip side on that same coin is a slower acceleration and a limited top speed, but with no gears to change the power delivery is flawlessly smooth.
It is also hard to ignore the fact that doing a FWD conversion with the factory gearbox / diff is not only cost efficient but saves a massive amount of re-engineering and adaption.
But again it doesn’t come without penalty. Remembering that the factory gearbox was designed specifically with an internal combustion engine in mind, and while it can be adapted with some success it should not be considered the definitive solution for an EV.
Piston based ICE are designed with multiple main bearings to support the weight of the crankshaft and flywheel, but even more importantly the ICE is designed with thrust capacity in mind, for when heavy loads are applied to the back of the engine through the application of the clutch.
Yes you can remove the weight (10-15kgs) of flywheel and thrust load from the equation, and have the EV motor drive the gearbox directly, but regardless of what BS people may try feed you, a gearbox designed to have a clutch will not work as optimally without one.
You can machine up a light weight alloy flywheel with far less weight, but you are still loading up a bearing not designed for those kinds of loads.
The other major consideration is the instant torque of an electric motor; ICE cannot reproduce the same off mark figures, nor keep the same flat torque curve that gives an electric motor a far more usable rev range, which results in less need for a gearbox with lots of gears.

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Why standard GEARBOX for EV's

Post by Goombi » Sun, 12 Jul 2009, 20:49

Will a motor coupled directly to Diff work from 0 to 95 Km/h "NO"
Will fly-wheel with a clutch change the gears any faster? "NO"
Will damage be made if full AMP are applied for start---- "NO"
The controller will only allow certain amount of amperage to propell the motor from the start then increase the supply as revs increase.
The reason why motors have CONTROLLERS is to control the process of input. Modern controllers have function to supply amps to motor on account of voltage.. Ealy DC motor were relying on VOLTAGE Step up contactors were used to increase the speed and power.
Only a roque controller will give you wheel spin from start. A matched controller with Motor will supply power for relatively quick uptake without burning rubber on par with normal take-off from ICE.
There is only one way --do it right and properly and the reward will come to you. EV2Go. When my mind is running a havock i throw in an anchor and stop and think for a while on one line of thought.Then I think about the Positive only ---and the negative I place in rubbish bin

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Why standard GEARBOX for EV's

Post by EV2Go » Sun, 12 Jul 2009, 21:39

Goombi I am not quite sure why you see things as “positive” or “negative” as there are just some irrefutable facts of life. I can choose not to breathe to save wearing out my lungs, but the repercussions of taking that action will lead to a worse one.
So therefore I choose the lesser of two evils, doesn’t mean it is ideal, but life is one big compromise. I don’t know why using or not using a gearbox would be any different.

If you honestly believe that driving a car with and without a clutch is the exact same experience then there is no more to say, but I drove my own car for 7 years with the exact same gearbox as an EV I test drove that didn’t have a clutch, and I can tell you from driving the EV about 50klms it is far from the same experience.

While it is “acceptable” it is still a compromise. I am not saying either is the right way to do it, merely that the decision has to be made based upon all the influencing factors .i.e. time, money, performance, longevity, experience etc.

To answer your questions
Will a motor coupled directly to Diff work from 0 to 95 Km/h: Yes it will with the right diff gears
Will fly-wheel with a clutch change the gears any faster? Most definitely

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woody
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Why standard GEARBOX for EV's

Post by woody » Mon, 13 Jul 2009, 00:01

Sorry Goombi, I have to agree with EV2Go, but we 2 are at the opposite end of the "need for speed" scale to you ...
For most peoples needs, a gearbox with no clutch is fine, and a suitable gearbox nearly always should help both accelleration and top speed...
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

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Why standard GEARBOX for EV's

Post by Simon » Mon, 13 Jul 2009, 02:30

In my opinion engineering is all about compromise. Keeping the gearbox is clearly the simplest option with a Front Wheel Drive car. But with Rear Wheel Drive it becomes much simpler to go direct drive.

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Why standard GEARBOX for EV's

Post by Tim » Mon, 13 Jul 2009, 05:06

I have never in any of the stages of design and planning for my (future) EV conversion considered retaining the gearbox. It does not suit my desired outcome or performance.

That said, retaining the gearbox and even the clutch would suit other conversions or others ideas of what they like. Or maybe it is the better choice given the other components selected or available.

As has been said above... neither choice is particularly right or wrong.
Don't listen to what I'm saying... just understand what I mean.

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