Brushless Maxx XL2800/7XL/9L
 

I need to just ask a few questions on the motors since the 9920 is still not in stock it gives me time to pick my perfect motor.

I'm looking for something fast, high 40s.

I don't want insane power, sounds daft but is it possible to reach mid to high 40s with out loads of power?

I would also like 5minute run times...

I will be running 14 cells but hope to upgrade to 16. They are GP3300s with lots of punch and read at 3700+mAh.

I looked at the following all with 9920:
Feiago 7XL
Feiago 9L
Lehner XL2800

Heard alot of good points on the 7XL and I like the idea, where needed I can expand in cell counts, just intrested in its capabilities with 14 cells, quick?

9L I'm not sure on because I don't want to be the same as everyone else, would prefer something different and unique, although it might be the one that meets all my demands?

XL2800 I'm not to sure how many cells it can run, if it would handle 16? 5minute runtimes?

I hope someone can answer a few or all of my questions and that my demands on brushless is not to high?

I know alot depends on how much you pull the throttle and what gearing you use but a general idea would be great.

Thanks alot, :D
Nick.

The 7XL would be an excellent choice for your cell counts, and many would agree. Also, since it is so powerful, it can be overgeared on 14 cells and still remain in the safe temperature range. The 9L shouldn't be run on 16 cells, so that might leave it out of the picture. The Lehner XL2800 shouldn't be run on 16 cells either.

One thing that will help your truck go faster without thermalling in 5mins. would be to make it lightweight. Whatever you go with, you will get more than 5mins. of runtime, so don't worry about that.

Here's what I (my son has the same setup) have in my slightly lighter than stock Maxx;

18120 (son has 9920)
2400xl
14 gp3300's (matched, 1.17+)
18/64 gearing
80mm PC fan, heat sink, Arctic Silver 5 thermal grease


I have an EagleTree but haven't really had a lot of time to play w/ my truck lately so its not hooked up and I don't have *hard* numbers for you. :-(


I race on a large track (very large) and extremely fast. The track on which I run there are about 4 long straights (couple aren't exactly straight, but full throttle is used). I finish the 10 minute main w/ enough juice to be competitive. I pull the MT's (gas Revo's...everybody here runs gas) with ease and can basically run w/ the 1/8 buggy's (in the more open sections). I estimate w/ my combination around mid 40's.

My truck (w/ the fan, heat sink, and thermal grease) runs about 120-130f (100f ambient)...until the batteries are low then it runs around 140-145f.

If you're running a lighter than stock truck (mine is 10 pounds 7 ounces, ready to race) you should be able to acheive the same runtime and speed that I do. If you're going w/ a lot of aluminum you'll probably need a motor w/ a little more torque, and w/ more torque (lower RPM's/volt) you'll probably want to run 16 cells (to account for the lower RPM/volt).

W/ regards to which motor, I believe the Feiago 7XL has roughly the same rpm/volt as the Lehner 2400XL. And I believe the Feigao 9L is roughly equivalent to the 2800XL.

Hope that helps.

Thanks alot, looks like the 7XL. If anyone has any specifications of runs they have done with it, speed/runtime etc' please let me know!

A technical question, not that it really matters but whats the difference in a 7XL to a 7L? I predict the 7XL is physically larger in can size?

I believe the longer can = more torque.

Total horsepower is about the same but notice the torque and rpm difference between the two motors.

Here's the 7XL on 16 cells at various amperage;
~~ [19.2 volts, 30 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 45334.2240
powerin: 576.0 watts
powerout: 485.3160 watts
HP: .6505
efficiency: 84.00%
torque: 13.44 oz-in

~~ [19.2 volts, 40 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 45200.8320
powerin: 768.0 watts
powerout: 673.6480 watts
HP: .9030
efficiency: 87.00%
torque: 19.20 oz-in

~~ [19.2 volts, 50 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 45067.4400
powerin: 960.0 watts
powerout: 860.8600 watts
HP: 1.1539
efficiency: 89.00%
torque: 24.96 oz-in

~~ [19.2 volts, 60 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 44934.0480
powerin: 1152.0 watts
powerout: 1046.9520 watts
HP: 1.4034
efficiency: 90.00%
torque: 30.72 oz-in

~~ [19.2 volts, 70 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 44800.6560
powerin: 1344.0 watts
powerout: 1231.9240 watts
HP: 1.6513
efficiency: 91.00%
torque: 36.48 oz-in

~~ [19.2 volts, 80 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 44667.2640
powerin: 1536.0 watts
powerout: 1415.7760 watts
HP: 1.8978
efficiency: 92.00%
torque: 42.24 oz-in

~~ [19.2 volts, 90 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 44533.8720
powerin: 1728.0 watts
powerout: 1598.5080 watts
HP: 2.1427
efficiency: 92.00%
torque: 48.00 oz-in

~~ [19.2 volts, 100 amps] ~~
voltageconstant: .0080
Kt: .0107 (oz-In/I)
rpm: 44400.4800
powerin: 1920.0 watts
powerout: 1780.1200 watts
HP: 2.3862
efficiency: 92.00%
torque: 53.76 oz-in



And the 7L on 16 cells at various amperage;
~~ [19.2 volts, 30 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 66789.7530
powerin: 576.0 watts
powerout: 475.5750 watts
HP: .6375
efficiency: 82.00%
torque: 9.60 oz-in

~~ [19.2 volts, 40 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 66582.6040
powerin: 768.0 watts
powerout: 663.7400 watts
HP: .8897
efficiency: 86.00%
torque: 13.44 oz-in

~~ [19.2 volts, 50 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 66375.4550
powerin: 960.0 watts
powerout: 850.7250 watts
HP: 1.1403
efficiency: 88.00%
torque: 17.28 oz-in

~~ [19.2 volts, 60 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 66168.3060
powerin: 1152.0 watts
powerout: 1036.5300 watts
HP: 1.3894
efficiency: 89.00%
torque: 21.12 oz-in

~~ [19.2 volts, 70 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 65961.1570
powerin: 1344.0 watts
powerout: 1221.1550 watts
HP: 1.6369
efficiency: 90.00%
torque: 24.96 oz-in

~~ [19.2 volts, 80 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 65754.0080
powerin: 1536.0 watts
powerout: 1404.6000 watts
HP: 1.8828
efficiency: 91.00%
torque: 28.80 oz-in

~~ [19.2 volts, 90 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 65546.8590
powerin: 1728.0 watts
powerout: 1586.8650 watts
HP: 2.1271
efficiency: 91.00%
torque: 32.64 oz-in

~~ [19.2 volts, 100 amps] ~~
voltageconstant: .0054
Kt: .0072 (oz-In/I)
rpm: 65339.7100
powerin: 1920.0 watts
powerout: 1767.9500 watts
HP: 2.3699
efficiency: 92.00%
torque: 36.48 oz-in

nothing speaks better than numbers.......basically, the 7XL has a higher torque than the 7L at a given current - but the 7L has a higher RPM than the 7XL for a given voltage ( torque is proportional to current and rpm is proportional to voltage ). Power is the product of torque and RPM, therefore they both have roughly the same power, although because the 7XL will draw less current it will run slightly cooler and more efficiently than the 7L.

The 7XL would be my choice of motor without any question. You may have to gear up slightly to get the same speed as a 9L, but you will get much better run times and much cooler temps.

How do you change how many Amps are going into the motor? Or is that done on a special tool to test the motor outputs?

I like the idea of the 7XL alot, definatly what I am going with now, especially to know I can always slap upto 4 more cells on if I needed abit more power!

When are the 9920s in stock? :(

In the data I provide I simply input the different amps you're likely to see.

The actual amps you'll draw depend on the weight, drive train friction, grade of terrain, gearing, etc. etc.

The 7XL has got a 45 mm long rotor, over the 30 mm long L serie..

That is 50% longer for the XL over the L.. if you multiply the torque of the L with 1.5 (50 % larger) you get the numbers on the torque of the XL...

;)

I prefer the 7XL over the 9L on 14 cells..

What's up, CHUD.......or should I say Chuck? I'm the kid up the street with the electric 1/8 Ofna buggy, and love my 2800xl. I got a Savage on the way with a 9L though, might have to take you on out at SV or at least bash some time. :D

As for the motor, just going off the name of the 7XL sounds sooo much cooler than the others.......:L:

I know who you (and your bro) are...I'm registered at lsarc also. ;-)

Yes, you gotta meet us at SV on a Saturday w/ your Savage to race race race. I'm always stoked when Friday gets here...means its time to get my ride ready! Gotta convert you two from bashers to racers. :lol
Or maybe we can come up and check out your home grown track!

I bet they'd let you race your brushless buggy against the gas guys (its *all* gas at SV, btw), but you'll need a few more mah for the long 1/8 buggy main.

I just prefer bashing over racing, but whenever the opportunity arrives (when I have Saturday/Tuesday off and $10 to race), I do!

Once I get my BL MT2 going, then maybe we'll head over to SV and see if they'd let me run it. How long is the 1/10 gas main?

1/10 gas truck was busy one weekend and not so busy the next. I think they run either 10 or 15 minute mains. I'll be your pit crew and swap the batteries. ;-)