Jump to content


Photo

Could an electric formula car series work?


  • Please log in to reply
208 replies to this topic

#201 Rasputin

Rasputin
  • Member

  • 291 posts
  • Joined: February 10

Posted 01 October 2012 - 05:18

...
To continue on this same theme - there are model electric motors of 3 horsepower that can be held in the palm of one hand. Back in my days in industry, a 3HP motor was 415 volts AC and was not able to be lifted by one person. Being pretty ignorant of "electrickery" - how can the model motors be so powerful for their size?


I suspect that the paramount reason is the brushless motors with 100 000 Rpm?

Advertisement

#202 Kelpiecross

Kelpiecross
  • Member

  • 830 posts
  • Joined: October 10

Posted 01 October 2012 - 06:33

I suspect that the paramount reason is the brushless motors with 100 000 Rpm?


I was under the impression that this particular motor drove a 30 inch (or so) propeller directly (not geared) - certainly not at 100,000RPM - but I could be wrong.

#203 Wuzak

Wuzak
  • Member

  • 3,460 posts
  • Joined: September 00

Posted 01 October 2012 - 06:42

Possibly the duty cycle.

Industrial motors have to run reliably for far longer and/or have frequent start stops.

#204 MatsNorway

MatsNorway
  • Member

  • 2,025 posts
  • Joined: December 09

Posted 01 October 2012 - 15:27

AC industry motors can go beond 20 years ABB claims
http://www05.abb.com...ile/motorqg.pdf

Its not unlikely that there has been motors surviving far longer.

There is no Professional electric 1/8 scale onroad racing. But thats where i think the threshold is just about. If there was a 1/8 scale electric Pro scene with cars and electric systems designed spesifically for that they would be easily faster over a 10-15min race.



the norm is usually a converted nitro car.

http://www.motonica....CTRON-SERIES_17

Its only the smaller and older Brushless motors that goes very high on revs.

Once the size goes up the rpms goes quickly down. just like in real life getting enough power is usually not the problem. Battery weight and runtime is.

that said. without the motor size rules and so on they would have quickly made the motors smaller. as they are quite large on a 1/10 scale rc car.

http://jdandracing.blogspot.no/

http://i100.photobuc...zpsd289f2af.jpg


http://www.corally.com/
go do brushless motors and red series sensored their 3.5T is rated for 1800Watts burst.

a pro driver uses motors rated probably around 500-800Watts 90% of the time.

Edited by MatsNorway, 01 October 2012 - 15:45.


#205 Rasputin

Rasputin
  • Member

  • 291 posts
  • Joined: February 10

Posted 05 October 2012 - 03:35

...

http://www.corally.com/
go do brushless motors and red series sensored their 3.5T is rated for 1800Watts burst.

a pro driver uses motors rated probably around 500-800Watts 90% of the time.


But that thing was what, 11 kRpm per Volt, some 80 kRpm then, which means a torque of 0.2 Nm?

Difficult to translate to a 500 kW motor, isn't it?

#206 Tenmantaylor

Tenmantaylor
  • Member

  • 8,224 posts
  • Joined: July 01

Posted 05 October 2012 - 14:21

In other news, Radical Toyota sets new EV lap record of 7m22. That's faster than a Nissan GTR and Porsche GT2 RS!

http://blog.axisofov...lap-record.html

Video

#207 MatsNorway

MatsNorway
  • Member

  • 2,025 posts
  • Joined: December 09

Posted 05 October 2012 - 16:03

But that thing was what, 11 kRpm per Volt, some 80 kRpm then, which means a torque of 0.2 Nm?

Difficult to translate to a 500 kW motor, isn't it?



As said. they will not need that sort of power. thats close to 2000hp pr tonne...

a 500watt brushless motor is very managable. Even more so when they go full scale and are allowed to run more poles etc.

Gearing will not be a problem. Biggest gains is to be found in electronics thats where RC cars probably is more advanced compared to their motors. And they are still developing the ESCs in race pace. More power and smaller size.

In the link Tenmantaylor provided the motor is smaller than the ESC. (Electronic Speed Controller)

Im not sure about its weight but in rc car world the motors is around 170grams and ESC is around 40grams.

http://www.lrp.cc/en...regler/details/

They also said that they got issues with top speed. The ESC for RC cars go around that by altering the timing to make it rev more. its on a decline now but in the last 2-3 years there was usually allowed to have dynamic timing in most stock classes. this ended up making a 10.5T (typically 300watts now) way more powerfull than a motor without dynamic timing/boost/turbo in the ESC. one of the offsets was that some ESCs made the motors kick like a mule once the correct rpm was achieved. Later came more true dynamic timing systems to smoothen things out.. And then stock racing become blinky classes where no dynamic timing is allowed. they now only allow endbell timing who makes the motors run very hot.

Modified still allows dynamic timing. But its rarely in use. Unless they drive a tight twisty track with one big straight.

Endbell timing has been around since the beginning of RC cars.

Posted Image

Edited by MatsNorway, 05 October 2012 - 17:35.


#208 Rasputin

Rasputin
  • Member

  • 291 posts
  • Joined: February 10

Posted 06 October 2012 - 03:58

Again, the high power to weight ratio of an RC-motor comes from the extreme Rpm, like 80 000, a 500 kW motor could never go there.

The comparison is thus purely academic, if 100 g per kW was possible for 100 kW+ motors, the Tesla-motor would weigh 23 kg (225 kW).

#209 MatsNorway

MatsNorway
  • Member

  • 2,025 posts
  • Joined: December 09

Posted 06 October 2012 - 13:05

Again, the high power to weight ratio of an RC-motor comes from the extreme Rpm, like 80 000, a 500 kW motor could never go there.


They go that high because they are only allowed to run two poles. and to get say 800watts with two pole 540 motors they need to run as low as 3.5-4.5Turns (the copper wire only goes 4.5times around the magnet)

http://www.graupner.....5/product.aspx

double the poles and the rpm gets cut in half. By increasing turns the efficiency goes up.

Honda KERS claimed 99% peak efficiency.

with that sort of efficiency you could probably dump more voltage on it and get more power out.

Magnetti marelli claimed 5kg? thats probably because they realised that they don`t need 99% efficiency. losing X% efficiency is ok if you save space and 2-3kg on motor.


I see lithium ion batteries are preffered. RC cars prefer lipo. lithium Polymer batteries. Because they are lighter. But they are also more dangerous.

http://www.redrc.net...c-lipo-battery/