7xl specs?

What would the loaded kv rating of a 7xl be? I found that it's listed to have 2382 rpm/v, but remember hearing that Feigao rates their motors without load. Also, what do the bearings max out at, 50,000 rpm like the rest of the Feigaos? I would guess that I'd max out the cell count on my controller before I totally tapped the power of that motor, who knows whether the vehicle would take it too!

[Gustav]

BK quote the kv as 2145 which must be loaded i guess.rpm wise,i don't know but it'd be plenty safe on 18 cells.

The 7XL is pretty much at it's limit on 18 cells, I'll be running mine in my Savage on 6s, which is ~18.5 cells. Any more than that and the bearings might fail.

[maxxdude1234]

bearings on feigaos are rated at 50,000rpm. wanderers are 100,000rpm (might be 80,000 - cant remember)

Okay, thanks guys, sounds good then. I've seen a Savage running a 8xl and 6s lipo, that was flat out insane, the thought of doing that with a motor that's one turn faster is just scary......but still tempting. Too bad we don't have an "evil" smiley, so just pretend there's one here: ___ . :L:

[Dafni]

The main advantage is the additional torque. The motor struggles less, means less heat is produced.
From a racers point-of-view, the XL motors might be on the heavy side, though. But I think the additional torque makes up for the extra weight.

Dabid, this smily here is quite evil: :devil (just click Get More)

[Serum]

Yeah, the KV ratings of BK is loaded. I thought it had a 92% efficiency at a load of 2000 watts.

[Dafni]

They determine the "loaded" rpm rating with some big propeller on the motor.

Originally posted by Dafni
The main advantage is the additional torque. The motor struggles less, means less heat is produced.
From a racers point-of-view, the XL motors might be on the heavy side, though. But I think the additional torque makes up for the extra weight.

See, this is the first time that I've really heard anything specific as to why the 7xl would be a great motor for a 1/8 car or truck, now it's starting to make sense. Just for fun, if I were to put a 7xl in my Savage, would it still run okay on 12 cells, or would the new minimum be 14? I heard someone mention that running a 7xl in their 1/8 buggy on 12 cells was still very good, but I don't know if I want to give my Ofna's 2800xl the boot just yet.

[Serum]

No, 12 cells is good to go in a savage as well. The thing is; with BL motors, the voltage doesnt matter, The torque is always the same (with a motor from the same range (xl serie, L serie, S serie)

The energy it can deliver on more cells is easy to understand; the torque stays about the same, but the RPM's get higer. So you have got more power available.

Dude, this is crazy, how could I even call myself an electric whiz without knowing this?!?! And I owe it all to RC Monster's forum......:D

So, if I'm getting this right, the torque to get it going will still be there, it just won't really have the speed........but the speed is gained by upping the cell count, right? Therefore, if I were to run the Savage on just 12 cells, it'd pull like hell until it topped out, and that could be fixed with more cells.

And now that I just re-read that, my 9L would have the same torque as a 9xl, or did I get messed up? My main interest is in whether my Savage would accelerate (and have a higher top speed, for that matter) with a 7xl than the current 9L?

[Dafni]

Don't forget the gearing factor, Dabid. You can gear a motor with more torque higher.

And, I think you messed Serums statement up indeed. All L motors will have, by definition, the same torque.

Ah, I see.......not sure how I got that part screwed up, but I figured I'd be wrong on at least one of those accounts. :D

Im new to this, im trying to get it

So (just looking at the xl motors) on the same number of cells a 7xl has more torque than a 8xl but the 8xl will have more speed than the 7xl. so the higher the number( 7, 8, 9 etc) the higher the top speed, but the lower the number the higher the torque.

Does that sound right?

but serum said

"The torque is always the same (with a motor from the same range (xl serie, L serie, S serie)"

So the torque of a 7xl is the same as a 8xl, 9xl etc. and the torque of a 7l is the same as a 8l 9l etc?

[coolhandcountry]

You accually have it backward basketti. The lower the number the higher kv you get. I am not sure if the torque changes. which in turn give you faster speed.
@dabid the 9xl has 50% more armature magnet on it I believe. So that is why it has the more torque.