Electric propulsion and other musings

[mzso]

Where do you get this "gearboxes waste a LOT of energy" from?

I don't know exactly. Maybe it was just implied often. I guess I was wrong.

Conversely, a typical electric motor, like the one I linked previously (http://www.neweagle.net/support/wiki/do ... /PP150.pdf), has efficiencies ranging from 65 to 95%across the RPM range at "full throttle".


Not only would his overall efficiency be better (0.985x0.95= 93.7% efficiency, verses the previous 88 to 90%) at Clay Pigeon, but he would also have 50% more power in the 30 to 35mph region than with the direct drive arrangement....

Umm... Not sure that this overlaying has much validity. You just overlaid vehicle speed and rpm, right?

[rscsr]

Where do you get this "gearboxes waste a LOT of energy" from?

I don't know exactly. Maybe it was just implied often. I guess I was wrong.

Conversely, a typical electric motor, like the one I linked previously (http://www.neweagle.net/support/wiki/do ... /PP150.pdf), has efficiencies ranging from 65 to 95%across the RPM range at "full throttle".


Not only would his overall efficiency be better (0.985x0.95= 93.7% efficiency, verses the previous 88 to 90%) at Clay Pigeon, but he would also have 50% more power in the 30 to 35mph region than with the direct drive arrangement....

Umm... Not sure that this overlaying has much validity. You just overlaid vehicle speed and rpm, right?

The speed and rpm are directly proportional, meaning that it is the correct approach he did without unnecessary calculation and so on. The other chart hast the same power curve at another speed ratio so it is also absolutely valid what he did.

[mzso]

The speed and rpm are directly proportional, meaning that it is the correct approach he did without unnecessary calculation and so on. The other chart hast the same power curve at another speed ratio so it is also absolutely valid what he did.

No, it depends on the diameter of the tires.You need to compensate by scaling the graph. Some proportions of the rpm might not be used or the speed range might be extended, etc.

[rscsr]

The speed and rpm are directly proportional, meaning that it is the correct approach he did without unnecessary calculation and so on. The other chart hast the same power curve at another speed ratio so it is also absolutely valid what he did.

No, it depends on the diameter of the tires.You need to compensate by scaling the graph. Some proportions of the rpm might not be used or the speed range might be extended, etc.

The Tire size is part of the transmission rate and is almost constant. And it doesn't matter as every speed related transmission rate changes will be the same at the same speed at the same power.
You don't need to do all those stuff to make an educated guess if something is possible.
To get the desired speedrange you have define the longest gear. You can do it different ways. For example if you want the maximum efficiency at higher speed you will use a longer gear or a shorter for the maximum at a lower speed. But it just doesn't matter.
The only proposal of his chart was to show that it is possible to get a higher usable efficiency with a 2 (or more) speed gearbox instead of direct drive.

[mzso]

The Tire size is part of the transmission rate and is almost constant. And it doesn't matter as every speed related transmission rate changes will be the same at the same speed at the same power.
You don't need to do all those stuff to make an educated guess if something is possible.
To get the desired speedrange you have define the longest gear. You can do it different ways. For example if you want the maximum efficiency at higher speed you will use a longer gear or a shorter for the maximum at a lower speed. But it just doesn't matter.
The only proposal of his chart was to show that it is possible to get a higher usable efficiency with a 2 (or more) speed gearbox instead of direct drive.

The tire matters, especially with direct drive. If it RPM graph is scaled down horizontally, because car reaches the speeds with higher RPM those huge peaks will fall into the high efficiency zone Also what I linked has a lot more high efficiency zones at higher half of the rpm range, which would be the bulk of the speed graph.

[Pierce89]

The Tire size is part of the transmission rate and is almost constant. And it doesn't matter as every speed related transmission rate changes will be the same at the same speed at the same power.
You don't need to do all those stuff to make an educated guess if something is possible.
To get the desired speedrange you have define the longest gear. You can do it different ways. For example if you want the maximum efficiency at higher speed you will use a longer gear or a shorter for the maximum at a lower speed. But it just doesn't matter.
The only proposal of his chart was to show that it is possible to get a higher usable efficiency with a 2 (or more) speed gearbox instead of direct drive.

The tire matters, especially with direct drive. If it RPM graph is scaled down horizontally, because car reaches the speeds with higher RPM those huge peaks will fall into the high efficiency zone Also what I linked has a lot more high efficiency zones at higher half of the rpm range, which would be the bulk of the speed graph.
http://abload.de/img/y400-rpm-torque1byar.png

Direct drive is already going out of style, because of the huge torque needed to produce power at very low rpm. That huge torque creates huge heat. Look at your own chart, below 1000 rpm is ~50% efficient, not so great. Each launch would just EAT power if using that motor with direct drive. With a direct drive your charted motor would only be efficent at very high speed.

[rscsr]

The Tire size is part of the transmission rate and is almost constant. And it doesn't matter as every speed related transmission rate changes will be the same at the same speed at the same power.
You don't need to do all those stuff to make an educated guess if something is possible.
To get the desired speedrange you have define the longest gear. You can do it different ways. For example if you want the maximum efficiency at higher speed you will use a longer gear or a shorter for the maximum at a lower speed. But it just doesn't matter.
The only proposal of his chart was to show that it is possible to get a higher usable efficiency with a 2 (or more) speed gearbox instead of direct drive.

The tire matters, especially with direct drive. If it RPM graph is scaled down horizontally, because car reaches the speeds with higher RPM those huge peaks will fall into the high efficiency zone Also what I linked has a lot more high efficiency zones at higher half of the rpm range, which would be the bulk of the speed graph.
http://abload.de/img/y400-rpm-torque1byar.png

So I hope you agree, that the changes in the gearing to tire slip are the same for both circumstances. And it doesn't change the fact that you have awful efficiency at low speeds. Therefore you are able to increase the efficiency with an additional gearing ratio.

Could you please provide something substantial about the tire slip vs. speed, instead of repeating the same words. And what do you say to the fact that a circumferential change (--> longer gearing) and the tire slip (--> shorter gearing) counteract each other?

[autogyro]

It has taken nearly three years for the general opinion to change from direct drive to using a gear box.
Amazing.
I consulted with Hewland on this very subject in 2010.
I wonder how long it will take for experts to finally realise that the lay shaft gearbox is only used in FE because it is what the gearbox companies currently make and not what is the ideal for electric traction?

[mzso]

Direct drive is already going out of style, because of the huge torque needed to produce power at very low rpm. That huge torque creates huge heat. Look at your own chart, below 1000 rpm is ~50% efficient, not so great. Each launch would just EAT power if using that motor with direct drive. With a direct drive your charted motor would only be efficent at very high speed.

From where, and when when was it in style? I haven't even seen one good, high powered direct drive engine with specifications for cars.
I wonder though how much could it be improved for racing applications by increasing poles as much as technically possible. That would work similarly as a reduction gears. That would bring the low efficiency part down to lower rpms and widen the high efficiency zones.
Also it would interesting to see a similar graph for an induction motor like the Evans electric I linked before

BTW the way. Does anyone know what speed does the RPM mean with "usual" wheel diameters?

[mzso]

So I hope you agree, that the changes in the gearing to tire slip are the same for both circumstances. And it doesn't change the fact that you have awful efficiency at low speeds. Therefore you are able to increase the efficiency with an additional gearing ratio.

Could you please provide something substantial about the tire slip vs. speed, instead of repeating the same words. And what do you say to the fact that a circumferential change (--> longer gearing) and the tire slip (--> shorter gearing) counteract each other?

Probably a stupid question, but what do you mean by "slip" exactly? My vocabulary's lacking apparently.

So I hope you agree, that the changes in the gearing to tire slip are the same for both circumstances.

Huh? This makes zero sense. What two circumstances? There's no gearing in direct drive

Could you please provide something substantial about the tire slip vs. speed, instead of repeating the same words. And what do you say to the fact that a circumferential change (--> longer gearing) and the tire slip (--> shorter gearing) counteract each other?

Larger diameter means higher speed at the same RPM. Nothing to substantiate.

[rscsr]

So I hope you agree, that the changes in the gearing to tire slip are the same for both circumstances. And it doesn't change the fact that you have awful efficiency at low speeds. Therefore you are able to increase the efficiency with an additional gearing ratio.

Could you please provide something substantial about the tire slip vs. speed, instead of repeating the same words. And what do you say to the fact that a circumferential change (--> longer gearing) and the tire slip (--> shorter gearing) counteract each other?

Probably a stupid question, but what do you mean by "slip" exactly? My vocabulary's lacking apparently.
--> car speed is different to the circumferential speed of the drive tires

So I hope you agree, that the changes in the gearing to tire slip are the same for both circumstances.

Huh? This makes zero sense. What two circumstances? There's no gearing in direct drive
-->if there is no gearing, the gearing is 1. And the circumstances are direct drive and use of an actual transmission.

Could you please provide something substantial about the tire slip vs. speed, instead of repeating the same words. And what do you say to the fact that a circumferential change (--> longer gearing) and the tire slip (--> shorter gearing) counteract each other?

Larger diameter means higher speed at the same RPM. Nothing to substantiate.
What about some data,chart, formulas or something that has a bit of value. To say something with nothing to back it up means nothing.

[J.A.W.]

It has taken nearly three years for the general opinion to change from direct drive to using a gear box.
Amazing.
I consulted with Hewland on this very subject in 2010.
I wonder how long it will take for experts to finally realise that the lay shaft gearbox is only used in FE because it is what the gearbox companies currently make and not what is the ideal for electric traction?

Layshaft (vs 'indirect') gearbox design offers a 1-1/direct top gear ratio with less loss of transmission 'efficiency'..

Perhaps a compact/annular mounting epicylic-type gearing set-up - is what you are angling for A-G?

[filbs]

I like Formula E because it seems a series where the design of the cars follows function more than being dictated by an incredibly complex set of rules, and I'm excited by the prospect of seeing the cars' performance increase markedly over the next few years, and seeing the technology developed get used in road cars.
The obvious area for improvement is the storage capacity of the batteries, but I imagine there's a lot of room for improvement in power that can be delivered/recovered - both by increasing the charge rate the battery can cope with, and having regenerative braking on the front wheels too.
The two cars per driver thing seems a bit of a joke. Guess the cars could go the full race distance as they are by slower driving, longer braking. imagine won't be many years before they do. Watching the China race, there was quite a lot of battery percentage left at the end of the race. Wonder whether this will be the norm for the rest of the season.

[autogyro]

Layshaft (vs 'indirect') gearbox design offers a 1-1/direct top gear ratio with less loss of transmission 'efficiency'..

Perhaps a compact/annular mounting epicylic-type gearing set-up - is what you are angling for A-G?

Lay shaft gearboxes running in so called 'direct top' gear still have the complete gear train rotating in oil.
Even in top gear they can be compared directly with a washing machine.
The torque loss is huge, try turning one by hand.

It is possible to produce a stepped ratio gear box with no engaged gear movement at all and only one shaft bearing in direct top gear.
An eight speed version goes into an 84 mm box with no need for a clutch.

[autogyro]

Layshaft (vs 'indirect') gearbox design offers a 1-1/direct top gear ratio with less loss of transmission 'efficiency'..

Perhaps a compact/annular mounting epicylic-type gearing set-up - is what you are angling for A-G?

Lay shaft gearboxes running in so called 'direct top' gear still have the complete gear train rotating in oil.
Even in top gear they can be compared directly with a washing machine.
The torque loss is huge, try turning one by hand.
As to figures for efficiency, the losses from oil drag is conveniently ignored in most cases and always has been.

It is possible to produce a stepped ratio gear box with no engaged gear movement at all and only one shaft bearing in direct top gear.
An eight speed version goes into an 84 mm box with no need for a clutch.