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isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689
Posted: 09:28pm 15 Oct 2012
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Just a thought..or pipe dream..
I am wondering about a possible transitional ev
configuration, based on some info re "locking" automatics.
They are said to lock after a certain rpm, ie the fluid
drive is bypassed for more efficiency.
So it seems a coupled 3phase motor could "idle" at low
rpm - thereby driving the standard air con and most
accessories as normal - and still drive with efficiency at speed.
Once the 3phase motor is turning at few hundred rpm, it is
generating the needed control phases...if Basslink can
use DC and a 3phase transformer to feed the grid, and a
3phase motor is a rotating transformer, then some nifty
wiring/SCR's should be able to feed pulsed DC into the motor phases
once it is running (!!???) thereby saving an expensive
control box. (at the expense of motor/rotor rewiring of course).
A small dc motor would "start" the main 3phase motor rotating.
And you would get a satisfying "startup" very similar to everyday
cars and driving.
Probably fairly less efficient though. (edit) And a special
rotor/rewire probably not worth the expense. Pity.Edited by chronic 2012-10-17
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 01:46pm 16 Oct 2012
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The automatic transmission has two input shafts, a solid inner shaft, and a hollow surrounding outer shaft.
These are both splined and "plug into" the back of the torque converter.
Now I am not certain which is which, but for the purpose of explanation here, it probably does not matter.
One of these gearbox input shafts is always directly coupled to the engine, and goes into a hydraulic lockup clutch within the gearbox. When this lockup clutch is engaged, the engine and gearbox are then directly coupled together.
The other gearbox input shaft plugs into the output of the torque converter, and directly drives the internals of the gearbox.
So there are two alternative ways of coupling the engine to the gearbox internals, which both effectively operate in parallel.
1/ Engine > lockup clutch > gearbox ... This is a direct mechanical connection
2/ Engine > hydraulic torque converter > gearbox ... this is a fluid connection
Normally when stationary with the engine running, or when starting off, the torque converter fluid connection must be used.
As a VFD and three phase motor can develop full torque at zero rpm, you don't need the torque converter. Just couple your motor straight into the gearbox, that's all you need.
With an IC engine, in the higher gears, above a certain road speed, the lockup clutch is engaged to eliminate the speed and power loss through the torque converter for better fuel economy.
This lockup clutch is electrically actuated from outside the gearbox, so you can operate it any way you want.
With your electric motor you can either run it direct into the gearbox through one input shaft. Or run it through the lockup clutch into the gearbox through the alternative input shaft, but I cannot see any advantage in doing that.Edited by Warpspeed 2012-10-17Cheers, Tony.
just to add to the 3 phase discussion, do people use big induction motors like these in cars?
http://www.bmms.com.au/details.php?id=13421
running at 415v means the amp draw would be lower for the same kw
or am i way off base here?
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 10:59am 26 Nov 2012
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The main problem with using a motor like that in a vehicle would be the huge physical size and very high weight for the power it produces.
The reason being that three phase induction motors are relatively slow turning high torque devices, and they require large heavy cast iron frames and a lot of copper to work as efficiently as they do.
That particular one, (four pole) would turn at maybe 1450 rpm at 50Hz to generate it's 30Hp. As a guess, it probably weighs about 150 Kg and might be 350 mm diameter and 400mm long.
A comparable high speed dc motor might generate 30Hp at 8,000 rpm, but be a quarter of the diameter and one eighth of the weight. With a light weight reduction gearbox the high speed dc motor would be much more suitable for a vehicle.
Cheers, Tony.
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 01:44pm 26 Nov 2012
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Warpspeed,
Are you 100% sure that is how a auto trans works, because it aint how i remember them.
Lockup or stall is when the fluid in the torque converter and the converter reach a 1:1 ratio hence causing a lockup of the converter, in drag racing you often use a high stall converter, with a lockup of say 3500+ rpm, this way you sit on the line waiting for a green light holding the engine revs just under 3500, and as soon as the light is green, you off the brakes and floor the throttle, giving a instant 3500 rpm to the trans and a converter lock up.
Then there was no electronics in a auto trans when i played with them.Sometimes it just works
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:34pm 26 Nov 2012
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Things have changed quite a bit since the old "slush box" automatics.
These days most automatics are controlled by a computer which opens and closes solenoid valves in the transmission to change gear. All those passages, balls, springs, valves and control diaphragms in a maze of passages that used to be located in the pan under the auto transmission are no longer there.
A fluid filled torque converter can never by itself completely lock up solid with zero slip.
In an effort to boost fuel economy, the auto manufacturers started fitting a mechanical friction clutch directly across the fluid torque converter which CAN be locked solid totally eliminating any converter slip, by totally bypassing the fluid coupling.
Notice that there are two concentric splined inputs to this "electronic" automatic gearbox.
One is directly coupled to the engine crankshaft, the other coming out of the back of the fluid torque converter.
The gearbox can internally select either as it's input.
Edited by Warpspeed 2012-11-28Cheers, Tony.
M Del Senior Member Joined: 09/04/2012 Location: AustraliaPosts: 155
Posted: 10:41pm 26 Nov 2012
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Hi Guys
There was a bloke on the MEAA elec veh site in the US that was modifying autos by removing the torque converter and direct driving the box input shaft then adding a small pump to supply the required fluid pressure.
I will chase my notes to try and confirm the design and gearbox type. Probably would not work on a late model electronic auto box.
People were worried about the oil overheating(no oil cooler required) but there is very little heat generated without the converter slipping in operation.
cheers
Mark Mark
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 11:41pm 26 Nov 2012
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It should still work on an electronic gearbox, in fact it would probably be the ideal solution.
With a main electric drive motor that works right down to zero rpm, the torque converter is not needed, and you could very easily program a microcontroller to change gears in the gearbox, and have the gearbox operate any way you wanted it to operate.
To select any gear (or neutral), it's just a case of energising or deenergising several low power 12 volt solenoid valves in various combinations. Some kind of engine or road speed sensor, a bit of fairly straightforward software, and you are set to go.
Edited by Warpspeed 2012-11-28Cheers, Tony.
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 01:01am 27 Nov 2012
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Its nice to see a todays input to present standards of a auto trans.
Im just a silly old bugger of yesterday that fired a few under 10 second missiles down the 400m straight line, when cubic inch meant everything, (there is still no substitute for cubic inches)
I will agree 100% lockup of a converter is not always the case, and why stage multistage clutches are used by the big boys (top fuel) in straight line racing.
Now to put the cat amongst the pigeons, the turbo 400 trans is the most bullet proof trans on an factory produced trans money can buy................. sorry Ford lovers ......... its a given fact Chevy rule the mantle on this one.
But i will quote the F....ord (Hard to say) 9 inch diff is as bullet proof to match the power requirement of the 400 trans.
Its always a hard point to admit you added a F...o...r...d, part to a 99% Chevy race car.
Pete.
Ps... who are you calling a slush box??
Edited by Downwind 2012-11-28Sometimes it just works
would it not be possible to remove the gearbox all together?
put the motor direct to the drive shaft and get rid of losses from the gearbox?
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 07:37am 27 Nov 2012
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I have only seen one of these motors up close, it was a 12 pole permanent magnet 3 phase motor. The blokes working on it told me that the voltages that the motor see's from the controller have to be reduced at very low revs, they were keen to use as large a rev range as they could, to the limit of their electronics. I should have asked a few more questions.
A wheel turns about 500 rpm for 100 Kph, so with a 3:1 diff your still looking at only 1500 revs at the speed limit. They were thinking of leaving it in second.
Pete
I have to put my hand up and admit that I tainted the purity of my beloved ford XY with a Turbo 400. The car finally felt the cruel hand of defeat by a Mazda station-wagon with a turbo'ed nitrous'ed ported 13B rotary motor. Smashed me by almost a second. A flamin shopping trolly!
The lock up friction clutch in the torque converter is most times just a flat disc that hydraulically presses against the front plate. They are a bit fragile and don't handle a lot of power. I have noticed often the car's owner has no idea it has stopped working. I'm confused, no wait... maybe I'm not...
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 11:25am 27 Nov 2012
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Hahaha Pete, the manual transmission guys used to call all automatics "slush boxes".
They were originally all controlled by hydraulics within the transmission itself.
To get it to change gear more firmly, or at a different rpm, you had to start changing springs, re drilling passages and all that was a real specialist job for the experts.
You could buy manual shift kits, and various custom bits and pieces, and some of the drag racers even ditched the torque converter altogether and fitted a manual clutch to the automatic transmission. Google "clutch flite" which was a very popular clutch conversion of the Torqueflite auto back in it's day.
The years roll by, and technology constantly changes, and the fully electronic automatic transmissions of today are very different to the all hydraulic originals of only a few years ago. All the internal functions are controlled electronically, except for the mechanical parking brake when in "park".
An electric vehicle works fine cruising down the road at constant speed, but without a gearbox the acceleration from a standing start can be quite poor. A gearbox offers extra torque when climbing steep hills or when very heavily loaded. It just improves both performance and efficiency. They even fit multispeed gears to bicycles for the same reasons.
You will get much better motor acceleration efficiency by letting it rev under light load in a low gear, than pouring amps into an almost stalled motor in a very high gear. Once up to speed, you slip into a tall gear.
Pete, probably the strongest automatic transmission around is the two speed Allison, they are HUGE, and commonly fitted to buses and those large garbage dumpster compactor trucks. They are also a favorite transmission used by guys building land speed record vehicles powered by Rolls Royce Merlin and Allison Aero engines. No other automatic transmission can handle the 2,000 to 3,000 Hp that some of these vehicles have.
An electronic automatic transmission/differential from a small front wheel drive car, direct coupled to a high speed dc electric motor would make an excellent electric vehicle. Very easy to control, simple, robust and reliable.
You can even buy suitable aftermarket programmable electronic transmission controllers that plug into your lap top computer.
With that, you can very quickly change the gear shifting points versus road, motor speed, and throttle position, to get the transmission to behave exactly any way you wish. With a bit of data logging and experimentation it should be possible to get the transmission to change gear in a way that gives best overall energy efficiency under a wide range of conditions. An adaptive self learning program should also be possible. Cheers, Tony.
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 06:03pm 27 Nov 2012
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Yes i know the Allison trans well, we had many of them coupled to screaming Detroits in the oil field for running high pressure triplex pumps.
We even had jet turbines and V12 Cats with Allison trans running frac pumps.
When you are pumping slime over a km beneath surface and hydraulically splitting the earth apart (fracturing) with pressures up to 15,000psi, it takes some huge horsepower, all driven through Allison trans in our case.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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