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Sep 04, 2019, 09:28 AM
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Optimal Power to Weight Ratio


Hey guys, for an engineering project we are looking for a motor with a very high power to weight ratio. We are looking for very high rpms, in the order of 65000 rpm. The power to weight ratio should be above 20 kW/kg. Very new models are welcome, preferably from the last two years. Any suggestion is welcome and the budget is not an issue . Thanks!
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Sep 04, 2019, 12:19 PM
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Fourdan's Avatar
Hi
To get >20 kW/kg you need probably a liquid cooling
By air cooling you get 3 ... 4 kW/kg in continuous running
What is the required power (or torque) in continuous ? EV ?
Good hunting (65000 rpm ?)
Louis
Sep 04, 2019, 05:20 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
What is the project? User requirements, restrictions?
Motor run time? Power? Operating voltage decided upon?

Vriendelijke groeten Ron
www.modelbouwforum.nl
Sep 05, 2019, 02:09 AM
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The motor has to run at peak power for approximately 10 seconds. The operating voltage is still open, we are free to choose our batteries as well as cooling. The high RPM is not necessary, but the high power to weight ratio is (Above 20kW/kg).

Are there any liquid cooling motors that you know of that have these properties?
Sep 05, 2019, 07:32 AM
An itch?. Scratch build.
eflightray's Avatar
I would suggest asking in the next forum down --- Electric Motor Design and Construction forum

They are likely to know if something exists, or whether it's possible to rewind a motor to give that sort of output.

.
Sep 05, 2019, 07:55 AM
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Thanks, will do!
Sep 05, 2019, 09:17 AM
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Fourdan's Avatar
Hi
It is impossible to help you, if you are not indicating power, rpm of your design.
Why are you searching a high ratio power/motor weight ?
In a project there are also the weights of the vehicle and the batteries and possibly the cooling system.
Read again Ron's questions !
Louis
Sep 05, 2019, 03:56 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Planes, trains, automobiles? Or boats?

Highest power/mass motors in RC land I know off are www.lehner-motoren.com. You could ask for their 10second rating.
www.plettenberg-motoren.net
www.torcman.de
www.neumotors.com

Vriendelijke groeten Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
e-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC
Sep 05, 2019, 04:18 PM
Registered User
Hi,
there is only Lehner Motors as they are the only that can handle 70000 to 100000 rpm and higher up to 200000 rpm by quest of spezial rotodesign and has the highest efficancy as they are only two pole motor where the frequenz related loss are the lowest and has slotless winding that also has lower loss as they have no iron that minimize the copperfilling and lower iron loss as magnetic flux has no lower and higher fluxpath like motors with sloted winding.
Fastes modelboat , fastes Hyperloop , best electric turboblower,

Happy Amps Christian
Sep 05, 2019, 04:38 PM
H-1
H-1
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H-1's Avatar
Quote:
Originally Posted by Christian Lucas
Hi,
there is only Lehner Motors as they are the only that can handle 70000 to 100000 rpm and higher up to 200000 rpm by quest of spezial rotodesign and has the highest efficancy as they are only two pole motor where the frequenz related loss are the lowest and has slotless winding that also has lower loss as they have no iron that minimize the copperfilling and lower iron loss as magnetic flux has no lower and higher fluxpath like motors with sloted winding.
Fastes modelboat , fastes Hyperloop , best electric turboblower,

Happy Amps Christian
Hi,
A FUNDAMENTAL solution to the problem is always nice.

Thanks for the additional lesson shared.

What kinds of things seperate a lehner from say a feigao slotless 2 pole or a kb 45 style 2 pole slotless motor.
Last edited by H-1; Sep 05, 2019 at 05:02 PM.
Sep 06, 2019, 03:09 AM
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Thread OP
We are making an electric dragracer and the run is for approximately 10 to 15 seconds. We have looked into the Lehner 3080, as this would have a high power to weight ratio and the high rpm.
As we can vary the wheel size of the dragracer, we can also use lower rpms but we do need the high power to weigh ratio. Does Lehner remain the go-to company for this or are there any other motors that you know off with a high power to weight ratio?

Thank you all for the responses by the way!
Sep 06, 2019, 03:42 AM
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Fourdan's Avatar
Hi
For an electric dragster you need probably a gearbox (chain, pinions, crowns)
So, why a very high rpm at the motor level ?
Other problems are
* High power (how much? 20kW?) for 10 s
* cooling (air or liquid)
* Batteries
* ESC (high acceleration)
* tyres
...
Regarding the motor you have a study to do yourself because a classical RC hobbyist is not used in that domain
There are 3 types of BLDC
* Outrunner (could be Scorpion HK 7050-340 limited to 8000-9000 rpm, or Rotex)
* Inrunner (Lehner, Neu ..)
* Axial flux motor (Enstroj ..)

Not a common project for the complete system !!
Louis
Last edited by Fourdan; Sep 06, 2019 at 08:56 AM.
Sep 06, 2019, 08:19 AM
An itch?. Scratch build.
eflightray's Avatar
This sort of thing ?,
Garlits Sets Electric Dragster Speed Record (1 min 6 sec)


or model ?

RJ Speed Dragster & Pro Mod With River City RC Drag Racing and Gabes Hobby Shop (3 min 1 sec)



.
Last edited by eflightray; Sep 06, 2019 at 08:21 AM. Reason: Added the model version
Sep 06, 2019, 08:26 AM
An itch?. Scratch build.
eflightray's Avatar
A search of thread titles containing 'dragster' in the 'Cars' sub-forums, found 19 threads.

https://www.rcgroups.com/forums/sear...query=dragster

.
Sep 06, 2019, 08:52 AM
H-1
H-1
Registered User
H-1's Avatar
A torqstar is a Lehner outrunner with still more power density than any scorpion. For comprable performance look at plettenburg possibly. Head to head the scorpion wont match the Lehner . You wont need any motors the sizes reccomend for a good 1/4 scale dragster anyway. You dont nneed anything nearly that big to produce those surge numbers at the tree. I'm sure ull land on that discovery soon enuf. 2 stroke Gas motors they use are lucky to make 10 hp at their best. Even a modest sized brushless can do this.

The limit will be the tires ability to hold together at speed. You need to look up nic case and castles journey in fast straightline development . The Neu 15 and 20 series motors use topology that is also very clean harmonically. With the small air gap and winding sequence they produce tremendous torque very efficiently.
Last edited by H-1; Sep 06, 2019 at 09:09 AM.


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