David VS. Goliath!!

[RC-Monster Mike]

Sound advice, Barry. Slower motors are the better way to go. Send me a copy of the video, if you don't mind!

[Chase023]

Thanks Promod, that really helps confirm what I was thinking as well. I wanted to use the Bolido with its slow 810 kv but I think with proper gearing it could be fast and very smooth.

[Promod]

Chase023, how many cells are you planning on running with the Bolido.

Thank you,
Promod

[Chase023]

I am thinking of running 30 - 32 Nimh Cells or 10s Lipoly pack.

The first Bolido I am thinking of running is on my FG 1:5 scale Car, then maybe two of em on my Custom Juggy but I think the Two BigMaxximums on their now is enough,but who knows.

That 2240 is a beast on that E-Maxx.

[Serum]

Promod, i am digging up this topic again, i find it very informative, considering some users here wanted to power up their trucks with such motors as well. (incl me)

Did you shot a movie of this monster in action?

[starscream]

I am also very interested in this topic.
The 2240/10 and the 2240/12 motors are great prospects for higher voltage applications. I believe that you could reduce your amp draw/efficiency by increasing your voltage and gear reduction a bit. From what I've read the amp draw (current) will increase if you are below or above the motors efficiency range.

I would be very interested in your results with the 2240/10 at 9s with a 10/51 gearing. This should give you similar speed to the 6s with 16/51 gearing but with less amp draw.

It would be awesome if you could test this :cool:

Thanks

[JOHNNYMAXXIMA]

Hmmm, wonder how 2 of those motors would run in my truck? j/k.....I think.
Anyone know the weight of that truck? Looks pretty light.

[Serum]

starscream;

With higher voltage systems, your better of using a lower kv rate, and gear up , than the other way around..

[starscream]

Hey Serum,
I guess the appropriate question I should ask is what's the efficiency range of the motor (say the 2240/10)?

Here's a quote I received from an electrical engineer:
Higher voltage allows a stiffer gear ratio and thus requires a lower current to make the same power that lower voltage and higher current produces.
Higher efficiency comes from running cooler at the lower current....if the current is high enough to be in the max efficiency range of the motor.
Since you're racing, you can relate to Formula one cars. They make power with small, very high revving engines. They rev to 19,000rpm on a V10! The same approach applies to electrics. A small high revving motor geared properly will be more efficient overall that a larger, heavier, lower revving motor.

This is also what I have recently read, if you are below or above the efficiency range of a motor, the current will increase so max efficiency should be somewhere in the upper limit of this range.

So, it seems that Promod should be able to add enough voltage to the 2240/10 to be in the upper limit of the efficiency range of the 2240/10. 9s should put him at 49284rpm which should suffice thus achieving the same or more power with less current. I think if Promod tests this the numbers will tell us if it is correct. I believe the amps will drop and the motor will be more efficient if he runs 8s or 9s with the 10/51 gearing.

We really need to know what the specified efficiency range is to be completly accurate.

I would love to get a 2240/10 but I'd like to see some numbers first.

Thanks

[Serum]

You can't compare gas motors to electric.

the theory behind electric is that the higher the voltage, the more efficient the motor gets. A bigger motor has got more torque, that's why it doesn't need the rpm's to make the torque by gearing it down, like smaller motors.

It's very simple;

to produce 1500 watts with 100 volts requires 15A to make 1500 watt with 10 volts require 150A. Mostly, the higher the current, the less efficient. the more the internall resistance of the system becomes relavant.


Overall, a large lower KV motor runs less hot than a small high reving one. it is not said that a smaller high reving motor is more efficient. Far from that. (assuming it are both motors from the same serie)

I like a bigger low KV motor over a small high reving one. less heat means more efficient. A big motor has got more magnetical energy to power a car with more ease. resulting in less heat as well. When a magnet becomes hot it becomes less efficient as well, because of the magnet getting less efficient, it gets hotter etc etc etc..

The most efficient range of the setup depends on the gearing ratio, voltage and the resistance of the vehicle (mass etc)

Efficiency of electronics has got more to do with the high frequency of the electronics and the speed that the controller has to build up a clean as possible pulse. That's what makes a BL setup efficient. It's not about high rpm reving setups. . A setup certainly knows his sweetspot, mostly this point is under the 38000 rpms

It depends on so many factors.

[starscream]

I agree Serum,
I am really interested in the 2240/10 and would like to see where the sweet spot is. It would be cool to see the numbers between the lower voltage 15/51 gearing and the higher voltage 10/51 gearing :cool:

Thanks

The Star Screamy Screamin Screamer ;)

[maxxdude1234]

I am a little confused by what starscream was trying to say in his earlier post. But here are some tables that make for some interesting reading

Lehner BASIC XL 1200, http://www.lehner-motoren.de/diagram....18v_liste.txt

Lehner BASIC XL 3600, http://www.lehner-motoren.de/diagram...6.7v_liste.txt

These 2 links show data from lehner's website. Both motors are doing 21-24krpm. One can cleary see that the XL 1200 is a good 4-5% more efficient than the XL 3600, it has about 50% more torque, and 50% more power (output). Lastly the XL 3600 is pulling double the current of the XL 1200 ( and yet the XL 1200 has 50% more torque!! ). I hope these figures prove to everyone that slower turning motors are more efficient, more powerful, far more torquey and draw much less current.

Ps. in the links, you see the bit that says 'basxl-12.18v' and basxl-36.7v', do you think that they are the more accurate kv ratings of the lehner motors. ie the XL1200 is infact 1218kv and the XL3600 is infact 3670xl? Seems likely......

[starscream]

Right on maxxdude, I'm not sure why I didn't see those graphs before (my german's not so good, actually really bad :o )
I'm not sure what the differences of the following are:
TIMING 15ø
STERN TIMING 15ø
TIMING 15ø STERNSCHALTUNG
"STERN"-GESCHALTET TIMING 15ø

So I took a look at the STERN TIMING 15ø for the 2240/10.
http://www.lehner-motoren.de/motordia.php
http://www.lehner-motoren.de/diagram...22s_grafik.gif
http://www.lehner-motoren.de/diagram...26s_grafik.gif
http://www.lehner-motoren.de/diagram...33s_grafik.gif


Correct me if I'm wrong, but those graphs for the 2240/10 show that both 26volts and 33volts are higher efficiency with lower current versus running on the lower 22volts.

[maxxdude1234]

Thats to do with what Serum was talking about; the sweetspot. All motors (and engines) have a certain RPM range when they are most efficient, known as the 'sweet spot' (I'm sure it hs many other names). The sweet spot varies for all different motors, but for motors of the size we are using it is just under 40krpm. At 22volts the motor is only doing 19000rpm, but at 33volts it is doing near 30000rpm, nearer to the sweetspot, hence higher efficiency.

[starscream]

Cool, it looks like I was correct without looking at the graphs. 8s or 9s would be closer to the sweet spot (higher efficiency). Higher voltage being 7s to 9s and geared lowered (such as 10/51). I think it is very clear what lower kv motors are capable of. My point of clarification is where the sweet spot is. It seems that the sweet spot is toward the upper limit of the efficiency range (which requires lower gearing which is relative to the application). If these graphs are any indication of the efficiency range of this motor it seems that it is around 22 to 33volts (33 volts being closer to the sweet spot).
I would still like to see what numbers Promod would get from his 2240/10 on 8s or 9s with 10/51 gearing. Thats the only way to know for sure :D