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-   -   What bl motor to use with 3s lipos (https://www.rc-monster.com/forum/showthread.php?t=7154)

Heyitsme 06.13.2007 06:43 PM

Quote:

Originally Posted by crazyjr
I bet its the traxxas forums, they got a nasty case of more's syndrome there.

Haha, you are right on, it was the traxxas forums, and there are all still telling me to get the 5700 with 3s lipo, and I was and still am maybe thinking of going with the 5700, and get 1 5ah 2s lipo, and 1 5ah 3s lipo. But when I come to this forum, you guys make me want to get the 4600 and 1 3s 5ah or 6ah lipo battery and 1 7 cell IB nimh. An you guys are right im sure there are alot more people on this forum that know what there talking about and been in the hobby alot longer, including your crazy, and couple you said that you have switched from 5700 to 4600 to run with 3lipos, and you guys wouldnt switch for no reason right?. This is example of what traxxas forum people who run 5700 3s say.

(you can run the 5700 w/ a 2cell if you want and get about the same speed as the 4600 on 3cells, but for that price you can get 2 batteries or just 1 large one of a 2cell for the 5700. I run my 5700 at times w/ a pair of 6000mah 2cell's linked and I get bored way before I run out of juice You can always snag a small 4000mah 3cell for some speed passes high speed runs etc on the asphalt. I think if you gear your car right even w/ the 3cell on the 5700 you shouldn't have to worry much about heat. It's wicked fast so going down to a 12-14t pinion is fine even a 90t spur.)

( not w/ a 4600, get the 5700 hands down you can use the mamba software to control your motor all you want, but w/o a 3cell it's gunna be SLOW, slower than your Titan 12turn or at best the same speed.. why spend that much money if you don't want a little more or the possibility of a little more? A 3cell w/ the 4600 could be decent... but otherwise you can buy an aweful lot of titan 12t replacements if all you want is the performance you get w/ that.)

and another 3s 5700 user said Get the 5700.
thats why im stuck inbetween the two Im getting diffrent anserws on diffrent forums
Thanks so much guys, im going to wait for a few more response and then make the order in the next 5 hours. still dont know whitch one tho, and does anyone have an idea how fast 4600 will go on 7 cell nimh?

BrianG 06.13.2007 07:04 PM

If running it on 7 cells, then go with the 5700. If 3s or 10 cells, go with the 4600.

To calculate motor speed, simply multiply the voltage by the motor KV. So, 4600kv * 8.4v = 38,640rpm. The idea is to use the lowest kv motor you can for the voltage you are using. Higher kv motors means more current, which means more losses, which means more heat. Basically, it's better to develop high power with high voltage and lower current than the other way around.

Heyitsme 06.13.2007 07:13 PM

Quote:

Originally Posted by BrianG
If running it on 7 cells, then go with the 5700. If 3s or 10 cells, go with the 4600.

To calculate motor speed, simply multiply the voltage by the motor KV. So, 4600kv * 8.4v = 38,640rpm. The idea is to use the lowest kv motor you can for the voltage you are using. Higher kv motors means more current, which means more losses, which means more heat. Basically, it's better to develop high power with high voltage and lower current than the other way around.

No Im planing on buying one 7 cell nimh, or 2s lipo for control and offroad, (AND one 3s lipo for sure, for high speed), I spent the extra money on the ice charger to charge lipos so im going with 3s no matter what. I just cant decide to what motor to run it on with out having heating issues. Crazy how fast is your 4600 on your 2s lipo setup?

crazyjr 06.13.2007 08:14 PM

Quote:

Originally Posted by BrianG
If running it on 7 cells, then go with the 5700. If 3s or 10 cells, go with the 4600.

To calculate motor speed, simply multiply the voltage by the motor KV. So, 4600kv * 8.4v = 38,640rpm. The idea is to use the lowest kv motor you can for the voltage you are using. Higher kv motors means more current, which means more losses, which means more heat. Basically, it's better to develop high power with high voltage and lower current than the other way around.

I agree with you on bashing, the 5700 is best on 2s and 6-8 cells. I choose the 4600 because mine will be raced and the 4600 feels better on the track on 2s. The 8000 pack is awsome in my T4 and fits almost perfect (had to move the strap screws up a little) and the pack is lower in weight (by 50 grams) than any 6 cell pack

bdebde 06.13.2007 08:36 PM

If you will be running 2s or 7 cell packs for the most part, then yeah the 5700 may be a little more what you want. If you do 3s on the 5700 for speed runs, just watch how hot ya get it. I only run 3s in mine, so the 5700 is ******* crazy, and heats up a lot. The 4600 can run all day on 3s.

Heyitsme 06.13.2007 08:52 PM

Quote:

Originally Posted by bdebde
If you will be running 2s or 7 cell packs for the most part, then yeah the 5700 may be a little more what you want. If you do 3s on the 5700 for speed runs, just watch how hot ya get it. I only run 3s in mine, so the 5700 is ******* crazy, and heats up a lot. The 4600 can run all day on 3s.

I will be running it on 3s lipo and 7 cell nimh or 2s lipo . Im planning to use them equaly after one dies put in the other or what mood im in and what terrain, but I will probley mostly use 3s lipo if I can control it. thats why im trying to get an idea how fast, a 7 cell nimh or 2s lipo goes with 15/86 gearing on the mm4600 motor on a rustler. im hoping at least 30 to 35 mph a good controlable speed for when i dont want crazy. Anyone have an idea on thoese speeds? thanks

3 more hrs to order time. the more feedback the better, still undecided

BrianG 06.13.2007 09:54 PM

Even if 3s is too fast, you can always not go WOT you know. ;) Or, cut back on the throttle EPA. This will also help runtime too.

Heyitsme 06.13.2007 10:20 PM

Quote:

Originally Posted by BrianG
Even if 3s is too fast, you can always not go WOT you know. ;) Or, cut back on the throttle EPA. This will also help runtime too.

Ya thats true, im think more along the lines of not being able to control it in dirt,or off pavment with it spinning the tires and spinning out with 1/16" movement of my unsteady finger and 11.1 volts. But yes I plan on mostly using 3s lipo, so im still leaning towards 4600, but how long bdebde does your 5700 3s take before it starts getting to hot, with medium to slow bashing speeds?, and more high speed use? thanks guys for your help. After tonight I wont be bugging you guys no more, and hopefully this thread will help others in my situation.


Edit: and whats is EPA?

BrianG 06.13.2007 10:36 PM

epa=end point adjustment. It's a setting found on the transmitter that limits the servo travel (or throttle in this case). Some of the more inexpensive radios may not have this setting though.

bdebde 06.13.2007 10:38 PM

Medium to slow speed tend to heat up the ESC faster. After 10 - 15 min the 5700 is too hot, and that is about how long the 3800 li/mn batt lasts. I get 15 to 20 min runtime with the 4600, so if you want longer run times, go 4600. I even have a hard time getting the 4600 up to full speed, without a large parking lot.

SpEEdyBL 06.14.2007 03:51 PM

From what I hear from the traxxas forums, it sounds as if most of those people haven't even tried a mamba max, let alone any brushless system. The 4600 is no doubt faster than the 12 turn titan motors, even on 2s lipo. In fact the 4600 on 3s lipo will blow away the 5700 on 2s lipo. All most anything, really, on 3s lipo is faster than most 2s setups. In fact, I'd expect the 4600 on 3s to be on par with the 7700 on 2s lipo if not faster. I have a feigao 380c 9t, which is similar to the 4600 and the front end of the vehicle (modified xxx4) can start to lift off the ground if you don't watch it, especially on the road surface in front of my house. Actually my 380 12s (3300 kv) on 3s is just slow enough for running right in front of my house (300 foot straights). Unless you run on a track, its not the control you have to worry about (well depending on the vehicle. 4wd is easier to drive). It's really the buckles in the road that can send your vehicle flying if you don't watch it.

Heyitsme 06.14.2007 05:07 PM

Ya I dont know about the traxxas forums, most the people there registerd in 2007. Does anyone think I would be able to gear up a rustler with the 4600mm and 3s lipos to go around 55, with out over heating the setup, for on and off road bashing?

Or should I change my order to 5700 for thoese speeds.

bdebde 06.14.2007 05:39 PM

I would say keep the 4600, if you really need more speed then get the 5700 (try gearing up first). I went the other way and got the 5700 first. It was way too fast as well as getting pretty hot, so I had to get the 4600 so I could actually have fun with it.

crazyjr 06.14.2007 05:42 PM

shouldn't be a problem, I had my T4 on a 5700 at 45 it flipped backwards and skided about 75feet, it took the outer most holes in the shocktower, all four of them. I know it was doing 45 because a friend, was radaring it, I was trying for 60;) need a couple ounces on the front. I think the 4600 could be faster, because you should be able to gear it higher than the 5700.

SpEEdyBL 06.15.2007 06:40 PM

Are you sure 55 is what you are looking for? What was your previous setup? Most 2wd vehicles can't even reach that speed unless you are running at an airport or a perfectly smooth parking lot and 300 feet of radio range. Otherwise the vehicle will just wheelie unless you carefully guide the trigger to full throttle. And you definately can't reach that speed offroad. Anyhow 55 is doable with the 4600 incase you are still in doubt, but you will have to watch the temperatures as you would with any setup geared for 55.


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