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!

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.

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:

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)

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

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

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.

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?

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?

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.

The motors in a series, like all of the L motors, for example, are rated the same in terms of power. At their rated amperages, they should in theory all have the same torque. But, they will all have different torque constants, with the fastest motor having the lowest torque constant, which is why it pulls all of those amps.

not entirely true metalman. It's the power of the magnet that decides what power the motor can put out. The copper normally isn't the limiting factor.

It's brushless, think different.. :p the energy that is needed to turn the shaft around takes more energy with a higher KV rated motor, than with a low kv motor. it takes more energy, because the magnet give the resistance to the magnetical field, because of this magnetical field moving faster with a higher KV number, the amount of energy is the same if you calculate is back. the torque stays about the same. it's the current and the rpm's that differ.

The reason why i got to this;

My plettenberg bigmaxx made wheelies with the savage on 16 cells. It did the same wheelies on 8 cells. because a motor can't deliver more power in a certain rpm range, because of the limit that the magnet/magnetical field has got. with this high eff. motors, you are in this limit. (otherwise you would have got a motor with 100% + eff.)

You can see ALL motors from the same range, loosing their efficiency at a certain point (it all is at the same point of torque they need to deliver) they all suffer a sudden eff. drop.. (they start getting hot at this point, which is a logical consequence)

reason for this is the statisfaction point of the magnet. and that is what i'm talking about. ALL motors from a certain range can deliver the exact same torque. Question is ; have you got the A's to feed the high KV monster... :D

So the lower the number the faster it can go, the more rpms it has(7xl is faster than a 9xl), but they have the same amount of torque.

So whats the point of having a 9xl if the 7xl has the same amount of torque and is faster?

Runtime. and the max current the batteries can deliver. and the fact that the 7XL might be too hot for the setup (like running 20 cells on it, it takes a 8 or 9XL to do so)

oh ok. so the 9xl has more run time than the 7xl, and it can also handle more cells than the 7xl? i see:). thanks for clearing that up for me :).

I might get a 7xl and a 9xl when i go brushless and use the 7xl for bashing at the park and doing jumps, and use the 9xl when im at home or dont need the extra speed but will be nice to have extra run time. good idea or not?

why not just an 8xl. alot cheaper.

Why not just gear the 9xl up to do your jump and such? Unless you trying to jump a house. :D It has some good power and run time. Just a thought. A 8xl may be a good choice. I have not run a 8xl so can't help you there.

Jump a house, hmmmm maybe lol. i'll try and jump the carport first lol.

how much difference in runtimes and speed is there between the 7xl, 8xl, 9xl?

9xl 25 min 16 gp 3700 can tell you after the weekend on the 7xl. same truck.

wow 25mins thats cool. were you going slow or going pretty hardout?

Im gonna use 16 ib3800 cells so it should be about the same as what your getting with the gp3700's.

oh and another question, i read somewhere on here that the bearings in the 8xl and 9xl can handle more rpm? why dont they put the same bearings in the 7xl cause its a faster motor?

well not really sure about the bearings on the 8 and 9xl but i would spend the extra 10 bucks and get the wanderer. its got better bearings than the feigaos. basically the same motor though.

oh yeah that was it, mike was getting the wanderer 8xl and 9xl and they have better bearings. i think i'll get a wanderer then.

If you get the 8xl I am curious to how they run as well. I only got about 10 min with 7xl. Not sure why so big of a difference. that was with 18 cells same gp 3700 just they was newer at the time.

farout 10mins, must be because the batteries were new aye? cause it takes a few charges and cycles before the batteries are at their full potential. I dont know what i'll get lol. it'll be like a month before i order anything so i have a bit of time to make a decision. Im gonna use 1st and 2nd gear and gear it up a bit from stock. I'm keeping 1st gear cause i use my truck alot at home in my little back yard, just climbing over mums old plants and towing stuff lol, and it will give me better run times. Then when i take it out for a bash or take my dog for a run i use 2nd gear.

How much faster than stock is the 9xl? will i reach around 40mph with 16 cells with stock gearing?

the 7xls will be the wanderer version when they come back in stock as well.

mike, are you gonna have the 9xl in wanderer to?

yes

Any update on when these motors will be in?

i just got my 7xl and bk 9920 anyone know good gearing for it, i have 16t pinion and stock spur gear running on 12 cells
im looking for the perfect gearing.

Thanks

im not sure but that sounds close. i do know that your gonna need a aftermarket slipper. i would recommend the strobe with the ofna derlin spur and a sprong kit. this will require mod 1 pinions though.

-corey

The sprong thing doesn't work with a Savage tranny, does it? After racing my 9L'ed Savage today, I've come to the realization that it's just not working as good as I want, and I think I really need the 7xl now. There's a few other things I'd want to try, but right now the tranny's blown up, so I gotta have some "getting to know you" time with it first.

you wouldnt need a sprong kit with a savage cause the slipper pad set up the savage already has is pretty good. you need to for a maxx cause the slipper peg set up just isnt up to the job. Thats just what i think.