which 7700 is the best mambamax or 7700 c4 bigstick

[suthernboy08]

Im planning on buying a 7700kv motor. I do know a lil
about the max 7700kv but i dont know about the c4
bigstick 7700 exp the specs says it can handle 6 to 12
volts. Is this true or not? So which is the best motor?
Im puttin it in a fully modded graphite and aluminum
evader st. I built this monster from the ground up. As
for tires 2.2 rpm slingshot rims wrapped in roadrage 2
tires. As for transmission i swapped out the reg st tranny for the ext with dogbones instead of the cvds which are stronger. My current motor is a feiago 5914 kv motor with a maxamps 4000 2s battery.This thing is a monster tons of tourque topend is ok but i want more. My gearing is 87/21. So which motor will be the
best bang for the buck? MM or the bigstick. Will i need
better batterys,different gearin and what kind of speeds will i be looking at. Also this thing sets real low
so low the slights bump will scrape my rear bumper. dont know if that helps any but i thought i put i down also.

[SpEEdyBL]

I'm pretty sure the c4 is a relabeled mamba motor. I could be wrong, but then it would be a quite a coincidence that the c4 motor happened to have the same kv, have the same physical characteristics as the mamba motor.

[suthernboy08]

I'm pretty sure the c4 is a relabeled mamba motor. I could be wrong, but then it would be a quite a coincidence that the c4 motor happened to have the same kv, have the same physical characteristics as the mamba motor.
but the specs says it can take more voltage(c4)

[GSMnow]

I would never put 12 volts to a 7700 KV motor. Something is going to give up at that rpm. Most 36 mm motors are limited to about 70,000 rpm before the rotor splits. 7700 x 12 = 92,400 rpm OUCH!! Even on 2S LiPo, they can get scary 7.4 x 7700 = 56,980

What is your run time withthe 5914 Feigao? How hot does it get?

If you get over 12 minutes and the motor is not hot, gear it up. OR even better, run the 5914 KV motor on 3S and gear down a bit. You will have a ton more power and top speed. VOLTAGE is our friend. Anything over 45-50 mph is running 3S or more. 5914 x 11.1 volts gets you a top out rpm of 65,600 or so. Pretty close to the 70,000 rpm detonation point, but safe.

Super high KV motors are only used when you are limited to a low voltage and you have to suck as much current as you can to make the desired power level. A 7700 will pull about 50% more current than the 5900 does. It will go faster, but you will likely need to gear a little slower to keep it from getting too hot. Start out with a 17 or 18 pinion if you do go with the 7700, this will be just a little faster, then you can watch temps and see where to go from there. 17 tooth is probably a good starting point for 3S on the 5914 as well. 2S to 3S is actually a bigger step up than going to the 7700 on 2S.

That reminds me, what are you using for batteries? I'll bet they are not cranking out the current you need to realize the full capability of a brushless system. Even my 6 month old tean matched EP4200's are not up to it any more. I love my new LiPo's.

[suthernboy08]

I would never put 12 volts to a 7700 KV motor. Something is going to give up at that rpm. Most 36 mm motors are limited to about 70,000 rpm before the rotor splits. 7700 x 12 = 92,400 rpm OUCH!! Even on 2S LiPo, they can get scary 7.4 x 7700 = 56,980

What is your run time withthe 5914 Feigao? How hot does it get?

If you get over 12 minutes and the motor is not hot, gear it up. OR even better, run the 5914 KV motor on 3S and gear down a bit. You will have a ton more power and top speed. VOLTAGE is our friend. Anything over 45-50 mph is running 3S or more. 5914 x 11.1 volts gets you a top out rpm of 65,600 or so. Pretty close to the 70,000 rpm detonation point, but safe.

Super high KV motors are only used when you are limited to a low voltage and you have to suck as much current as you can to make the desired power level. A 7700 will pull about 50% more current than the 5900 does. It will go faster, but you will likely need to gear a little slower to keep it from getting too hot. Start out with a 17 or 18 pinion if you do go with the 7700, this will be just a little faster, then you can watch temps and see where to go from there. 17 tooth is probably a good starting point for 3S on the 5914 as well. 2S to 3S is actually a bigger step up than going to the 7700 on 2S.

That reminds me, what are you using for batteries? I'll bet they are not cranking out the current you need to realize the full capability of a brushless system. Even my 6 month old tean matched EP4200's are not up to it any more. I love my new LiPo's.
I get about 15min run time with my 4000 mah maxamps lipo geared 87/21 which is better than
i thought the motor is a lil warm esc is just warming up.
As for the motor situation are you tellin me ill be better
off gettin a 3s lipo?

[suthernboy08]

Also is there other mfgs that sells good lipos at a better
price than maxamps? Dont get me wrong they're great
batteries but alil pricey. I also know in this sport in pricey electronics payoff but im on a lil budget this week.

[ElectricThunder]

Amainhobbies.com has their own brand called Protek R/C. A 3s 4000mah lipo pack from them is about 89 bucks. Cheapbatterypacks.com also has their Elite 4800 cells in a 3s configuration for about 120 bucks I think. I've read that the Protek packs are actually quite good; I'm considering buying a 3s pack from them over summer.

[GSMnow]

If you "join" Max Amps, you get an automatic 5% discount on your first purchase, and after I bought 2 packs and a balancer, I am now a bronze member with a 10% discount. It makes their prices very competitive.

YES, 3S will make 50% more power with your existing motor. The motor and ESC are both thermally limited to 100 amps, give or take. 100 amps at 7.4 volts = 740 watts, and 100 amps at 3S 11.1 volts is 1110 watts. You will most likely need to re-gear to make use of this new power, so you won't go 50% faster. 30-40% faster is possible, assuming you are not already over geared.

[suthernboy08]

I just ordered a protek 11.1v 4000mah battery.
Can someone out there tell me some more
about this battery. I bought it because it looks
like a good deal

[GSMnow]

The specs on the ProTek packs look good. You should be very happy with the performance with your 5900 KV motor. Just remember to drop a few pinion teeth and reset the low voltage cutoff for the 3S. Have Fun!

[suthernboy08]

Will i have to change my current 2s
setup for the 3s?

[GSMnow]

Unless you are using (and trust) the "auto LiPo" mode, you will need to change the cutoff voltage to be safe. Pulling a 3S pack down to just 6 volts would be a disaster. You really want a 9.3 or 9.6 cutoff voltage for 3S. LiPo packs hold their voltage so well, that it won't seem like it is slowing at all until it is too late and you are doing damage to the cells.

The other issue is that the motor will be turning 50% more rpm. Without changing the gearing, it will try to hit a speed 50% faster. If you were reaching 40, it would try to hit 60. Not impossible, but pretty hard on the system. What size pinion are you running now? If you were running an 18, I would suggest trying like a 14 for starters. This will still be faster, and give greater accelleration and/or lower current draw for a longer run time. Since you went from a 2S 4000 to a 3S 4000, you are carrying 50% more watt hours of energy. You can chooose to go 50% faster or run 50% longer, or split it and get say 25% more speed AND 25% more run time. Due to aero drag not being linear, you won't quite get the full 50% more on speed, but you get the idea. If you were drag limited, it would take something like 4 times the power to go twice as fast, but most rc cars are not fully drag limited. I hit 38 mph in only 200 feet and top out, so I could gear for more with the power I have, but I just can't use it on the track I race at.

[suthernboy08]

im using 21/78 gearing is this ok or do
i need to go down a bit

[ElectricThunder]

Go way down. Like....way way down. You're running a feigao 540 6s, and that rotor is firstly only good till around 50k or 55k RPM. Next, at that gearing, I don't think that poor battery will be able to keep up with that motor at that particular gearing for very long at all. You must drastically reconsider the gearing. Start with a top speed you want to shoot for (something reasonable), and then work backwards from total RPM (5900 times 11.1) to figure out gearing. There are gearing calculators out there; I can find you one if you need it.

Another note: a feigao 540 6s is just not a 3s motor. The rotor is a big enough diameter that it has a lower RPM limit than something like the mamba motors or Novak motors (which both have smaller diameter rotors than the 540 S can rotors). You can probably get by with a few speed runs, but to run a 540 6s on 3s lipo as your "daily driver", you're pushing the envelope and risk grenading your rotor.

[GSMnow]

21 to 78, WOW you were shooting for some insane speed. If you stick with the little 78 spur, go down to a 15 pinion or so to see where you are at. That still seems tall to me, you must have a huige open area to run in. I have a MM5700 ,lower rpm than you, and I run 15 to 87 on just 2S in my XXX-T. If I was going to run 3S, I would need to go with a lower KV motor or find a way to fit a 96 spur in there. I'll bet your lugging and the motor is never topping up, which is surprising that your temps are good and your run time okay.

I was not aware that the Feigao rev limit is so much lower than the Mamba Max's. I figured most 540 size brushless motors were pretty safe to 60,000 to 70,000. Your 5914 at 11.1 comes out to 65,000 rpm, give or take. I hope it does not let go on you.

[SpEEdyBL]

Feigao 540 motors have bigger dia. and longer rotors than the mambas. A 540 6S has .0034 ohms of resistance so you should be able to gear it so it goes faster than the cm 7700. According the the specs the max rpm for feigao motors is 50,000, but I think mainly because they get very inefficient beyond that.

[ElectricThunder]

I think they limit the RPM because of what you said Speedy in terms of efficiency, but also because of the larger diameter rotor (like you also said), there is a much higher chance of things going kablooey. Although, when I think about it, centripetal acceleration should be less for the larger rotor at the same velocity, so I think it has to do with more physical mass.

GSM- "540" size motors is just can size now with brushless motors. The Novak rotors are actually "380" sized, while the 540 S feigaos are true brushless "540" sized. And then there are motors whose rotors are still 36mm in diameter ("540" sized can diameter wise), but their rotors are actually in between "540" and "380" (I think the lehner basics and even the CMS 36 castle motors fit into this category). I don't even know how the length affects things (besides greater surface area for greater magnetic field strength).

[suthernboy08]

Thank you guys so i will swap the 78 to a 87 spur
and go to the lowest pin i have 15t i think. Now will
this be ok or will i need a spur with more teeth? Also
over due time will it be safe to get another motor?
Or will gearing the motor low be ok and what is
a good motor to run 3s in a street staduim truck.
Also i drive in a huge parking lot to keep from crashing it but i think its took a toll on my maxamps 2s 4000
it doesnt seem to have the speed it used to but that
also could be due to the slipper i have to have it set
just right (loose) or the thing is way to powerful. In
a forum way back someone told me the feiago 6s
in a stadium truck was overkill is this true?

[GSMnow]

Setting the slipper to control brushless torque is a careul balancing act. I cheated a bit and added over 8 ounces of dead weight to my XXX-T to make it easier to control witht he MM5700.

The Feigao 6S on 3S will be totally ballistic. Your slipper will be doing double duty to keep you from doing 40 mph back flips. The RPM limit of the motor is a concern so I would recomend a bit lower KV motor. The Mamba Max 4600 would be idea. A Traxxas Vellineon is also good for 3S with a 3500 KV rating. Most motors under 5000 KV work very well. A Feigao 10S or so. With the 3S and lower gearing, you will have even more torque available to the wheels, so have fun.

How many charge cycles do you think you have on your 2S 4000 pack? Do you run it more than once every day? How long hjave you had it? Do you alwyas use it with a low volt cut so you don't over discharge it? I am very curious to get an idea what kind of life I should expect out of my Max Amps 3000's. I have about 30 cycles on each of mine, and they are every bit as good as new, if not a little better.

[SpEEdyBL]

There have been many reports of maxamp pack failures. I can report one myself. When I had first used my 5000 mah 4s pack, it had amazing punch. Wheelies in a 1/8 buggy with the novak HV4.5 were no problem, and the cutoff didnt kick in until the pack had no mah left in it. Later on the esc began to cutt power to the motor when there was still 2500 mah left in the pack, until finally, the motor wouldn't budge, until I turned off the esc and turned it back on again. Still the same problem. At first I though it was a bec issue, since the esc was not nearly hot enough to be overheating. I then switched to universal bec, which seemed to solve the problem. I got a 9 minute hard run before something began to thermal. The motor was 160 and the battery was 140 (Kind of wierd since I could hold my finger on the motor without too much discomfort and the battery seemed only warm to the touch, but the numbers didn't lie). After another minute of running the lvc started cutting out, but when i charged the pack the next week, it only took 3500 mah, and it lacked punch and began to cut out early into the run. I later found out that one of the cells was puffed and only read 2.8 volts before rebounding back to 3.4 volts. Either the pack got too hot or it was my fault for not matching the voltage of individuals cells often enough to ensure that the cells die at the same time. Either way, maxamps packs do not seem to be able to withstand as much abuse as other brand packs do such as my kokam 3s 3200 pack which two years old, has one cell that has 150 more mah than the other two, has survived my old mgm's 2.5v/cell cutoff voltage before I realized it, has dents all over the outside from my xxx4's slotted battery tray and crashes, and still works fine even in a 1/8 buggy, where it never exceeds 110 degrees, while my mamba max and feigao 9l are unable to stay within 160 after 5 minutes of running, even geared with a 12 tooth pinion.

[suthernboy08]

Well i only had the thing for about three or four months
now. Its been bad weather here and very cold and i
work alot so the pack only has about 20 charges on
it if that so could i have a bad battery and if so
how will i know? Oh yeah by the way my gearing
isnt 78/21 its 87/21 am i still overgeared for the feiago
6s with the maxamps 2s 4000 lipo?

[GSMnow]

Do you know your internal trans ratio (what truck is this) and tire dia.? With those I can figure back your theoretical speed and see where you stand. The Feigao 6S should be able to push you to about 40 mph on 2S.

[ElectricThunder]

He said it's an Evader ST, which I think has an internal ratio of 2.66:1 (I just checked tower, so I'm not 100% sure on that number; they mess up from time to time....;)).

[suthernboy08]

That is the same int ratio that i have

[ElectricThunder]

Looks like tower was right then. Whew!

[suthernboy08]

So will the 87t spur be alright to gear this thing

[ElectricThunder]

If you're going to use a 21 tooth pinion with that spur, you'll be at a roughly 11:1 final drive ratio. That's something like 6000 rpm at the wheels, which is pretty fast.

I'd suggest starting off with a smaller pinion and working your way up so at the very least you don't kill your lipo and ESC.

[suthernboy08]

so will the 87t spur be alright to gear
the 5914 with the 3s

[suthernboy08]

Ok so i will use the lowest pin i have
Ive been trying to use the gear wizard
also but i dont understand it. I need
some one to break it down to preschool
terms so i can figure it all out.

[GSMnow]

5914 x 11.1 volts = 65,600 rpm rounded down a little.
4 inch tall stadium truck tires = 12.6 inches per revolution.
40 mph, good safe starting point = 42240 inches per minute
42240 / 12.6 = 3352 rpm at the tires.
65600 / 3352 = 19.6 FDR / 2.66 internal trans ratio = 7.36 pinion to spur.
87 / 7.36 = 12 tooth pinion to start.
So here are the top out speeds
12 tooth goes about 40 mph
13 = 43.3
14 = 46.6
15 = 50
16 = 53.3
17 = 56.6
18 = 60 MPH < I would not try any higher than this.

[suthernboy08]

Since there isnt a 12t pin as i
know of ill start out wiyh a 14t.
Also where can i find a esc fan with
the mounts. Ive already have a 40 mm
fan but its way to big to mount it because
when i moved the esc from the side of the
chassis to the rear shock tower. With a 40 mm
fan with no mounts its just to big and its impossible
to mount it. This issue bothers me because i love
having the insurance of a fan.

[ElectricThunder]

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKKN0&P=7

Just screw that into the heatsink with I think M3 size screws. That is what I do with my Mamba Max.

[suthernboy08]

Thats pretty cheap too.
So with a lower kv motor
on 3s can this thing be a
nitro killer lol ?

[suthernboy08]

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKKN0&P=7

Just screw that into the heatsink with I think M3 size screws. That is what I do with my Mamba Max.
could you give me a address where
to buy those screws

[chewie]

rofl this thread reminds me of my t3 with a 3.5r in it that was a wicked ride.. 10500 rpm per volt..

[ElectricThunder]

could you give me a address where
to buy those screws

I don't remember exactly where I got them; I think they were spares from my T3. I go home tomorrow, so I'll try to get some measurements of them and look 'em up on tower for you.

[suthernboy08]

Thank you very much.Who
out there has pretty good
prices on brushless motors?
low kv

[ElectricThunder]

You can get the Traxxas Velineon motor which is 3500 kv. On 3s lipo, it can take some very high gearing (enough to push a heavy Stampede to 65mph give or take). That motor runs about 75.

The feigao motors also come in lower turns and run about 50 bucks off of offshoreelectrics.com (I think that's their site; google it and it should come up).

The mamba motors run around the same as the Traxxas motor, if not maybe 5 or 10 dollars more. The lowest kv mamba motor is 4600, which is fine for 3s lipo since it has a smaller rotor diameter and length wise than the feigao 540 cans, and thus is rated at 65,000 rpm.

Tekin has some new motors out also, but I have no idea what the RPM limit is on those things. Their 6 turn motor has a kv of 3200, and their 5 turn a kv of 3700. Their redline lineup of motors are supposed to be some stump pullers torque wise, and on 3s, are probably ballistic. Their motors are about 90-100 bucks, so more expensive.

There's also all the sensored motors, which run about 80-100 bucks.

Other than those motors, I can't think of anything else. After those motors, you start getting into the 100+ dollar range easy.

I must say, that you get what you pay for with these motors though. The Novaks and LRPs are good motors for the money in terms of quality and efficiency, and the lower kv variants can certainly take some larger gearing. I think most of the lower kv motors that are out there running on 3s won't disappoint you in terms of power, torque, and efficiency though.

The choice is up to you though.

[suthernboy08]

Theres been a site i used to go to
its called something (warehouse)
they have low kv feiago motors
from 30 and 40 bucks but catching
the L and XL motors instock is a matter
of timing. Is there anyone out there know
the site that im talking about?

[ElectricThunder]

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LX2839&P=X

Those are the screws I use to screw a fan into my mamba's heatsink I think. I'll see if I can get some pictures up eventually; I just got home, so I'm a little beat.

Nothing is coming to mind with the warehouse thingy.

[suthernboy08]

It was hobby warehouse but they have a recall or
something on the feiagos so ill go another route.
As for the screws do i need nuts on the end? Do
i have to drill anything? How do i make them
work? (the screws)

[GSMnow]

The screw will go right between the fins of the heat sink on the ESC and take a hold with no nut and no drilling needed. It is almost like they meant for it to fit.