Gearing Question

[evaderst69]

Im new on here and am kinda new to the whole brushless motor world but i have a setup question.. i have a duratrax evader and i wanna set it up to have a top speed of about 55 mph so i can hang with my friends who all have nitro truck.. if i run a mamba 7700 what gearing would yeild me a speed close to my goal

[evaderst69]

by the way ill be using unmatched ib4200 batteries

[ElectricThunder]

You have to pretty much figure out the gearing yourself. The 7700 is going to run pretty warm geared for 55mph I would bet.

What diameter tires are you using and what is the transmission ratio for the evader? I can probably figure out a rough area where you should be for 55 and assuming around 1 volt per cell under load.

[evaderst69]

im really new to the whole brushless motor thing.. is there a better motor choice for these betteries to abtain these speeds.. everthing is stock on my truck.. i plan to def get a metal idler gear though

edit.. the gearing is 4.88:1 (Internal 2.66:1) and the tires are standard 2x2.2 stadium truck tires

[ElectricThunder]

It depends on how much you want to spend, what you have now, etc.

I think a GTB 3.5R on 6 IB4200 cells would certainly get you that speed. Or a 4.5R would probably do it as well. This is if you plan on sticking to low cell counts. If you have the budget to go higher voltage (like a 3s lithium pack), then a Mamba Max 4600 or 5700 is probably a better bet.

Another cheaper system (that will require some higher voltage to get the speed you want) is the new Traxxas Velineon System.

Decent 3s lipo packs are not cheap though. A 3s pack for the Velineon or Mamba setups I mentioned are going to cost you around 125-150 bucks for just the battery.

There's a few options (your MM7700 option is still on the table too).:)

[evaderst69]

i def plan on stickin with 6 cell batteries im no racer just a basher who want to keep up with his nitro brothers.. i saw the novaks but i like the fetures of the mambas and the price i just want somthing reliable that will get me to about 55-60 mph so what do you think will be better a 7700 or the novak 3.5r.. i would like to run the mamba but need a good opinion on what to do or how to setup the mamba to run reliable at these speeds on 6 cells

[SpEEdyBL]

The 7700 is a slower motor than the 3.5r. I think the novak's are more reliable. They wont overheat as easily as the mamba motors and they are rebuildable, so you can replace the bearings, rotor and wires. The mamba motors are not rebuildable and you have to send them in to castle to get them repaired. One thing you also need to consider is your battery pack. I know you would like to stick with 6 cells, but chances are, the battery would fail before anything else. In any case, unless your nitro friends are all running Jatos, you will be fine with just 6 cells. I don't even think you'll even need 50 mph to hang with them and have a blast.

[evaderst69]

i think im just gonna run the mm 7700 with 6 cells for a while and mayne gear it for about 45 mph and just have fun with that and i will upgrade to lipos if i wanna go faster

[ElectricThunder]

The 7700 is a slower motor than the 3.5r. I think the novak's are more reliable. They wont overheat as easily as the mamba motors and they are rebuildable, so you can replace the bearings, rotor and wires. The mamba motors are not rebuildable and you have to send them in to castle to get them repaired. One thing you also need to consider is your battery pack. I know you would like to stick with 6 cells, but chances are, the battery would fail before anything else. In any case, unless your nitro friends are all running Jatos, you will be fine with just 6 cells. I don't even think you'll even need 50 mph to hang with them and have a blast.

I agree with you on the Novaks (I never thought of them being rebuildable as an advantage until I wanted to shorten some wires....haha!).:D

evader- The 7700 will get you 45mph, but monitor your batteries (especially the IBs) and the motor temperatures. I suggest investing in a motor heatsink with a good fan bolted to it to help keep temperatures in check if you go the mamba route.

[evaderst69]

will do ill get a heatsink for the motor and prolly a fan for the ecu.. im starting from scratch hear so dont expect any updates on the motor or setup any time soo

[evaderst69]

about how fast would the novak 3.5 be campared to the mm7700 on 6 cells.. also what would be the aproximate top speed on the 3.5 with ib4200

[ElectricThunder]

In a Rustler, I've seen GPS speeds of 47.7mph on 6 IB4200s and the GTB 3.5R system (I think he was geared a little more on the conservative side too).

I'm pretty sure that the Evader is quite a bit lighter than a Rustler, and 50mph would be a very sure bet with "normal" gearing on 6 IB4200s and standard sized tires.

I've read from numerous people on various forums that the 3.5R is faster than the 7700 (the 7700 can still hit a good 45-50mph also, but I think it'll run much hotter than the 3.5R system; I'm basing that on pure conjecture though). That makes some sense, considering the 3.5R has a kv of around 10,500 RPM/v and the 7700 is 7700 RPM/v. Wattage is probably similar for either motor (around 600 watts; the 3.5R is rated at 620 watts and the mamba systems can put out around 1000, but I'm assuming that's on their max voltage- or 8 cells for the 7700) on a 6 cell pack as well.

[evaderst69]

i have been considering the traxxas system um i kinda like the price and the availaliblty to be able to do about 70+mph.. i was curious how would these batteries do with a brushless system they are 8 cell here is the link.. according to their wesit with a 7 cell nimh with 8.4v and 4000+ mah with 28/83 gearing its capable of hitting 45mph how would it do with the battery in the link would it be a little faster because of the extra cell and volts or no

Click Here (http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLFW6&P=0)

[ElectricThunder]

A few things first: The traxxas system hits 70mph because A) it uses higher voltage (3s lipo), B) it's a 3500 kv motor which probably has a 540 sized rotor (torque up the wazoo), and C) 70mph is attained with a gearing of roughly 31/76 in a Rustler or Bandit on 3s lipo (something that's good for about 100 amps continuous btw).

On to the battery you linked to; yes that one extra cell would make a noticeable difference (8 cells on a brushless system is pretty powerful). When you up the voltage, however; it is generally wise to regear down on the pinion a tooth or two to control current draw.

In an evader, that system would probably perform really well though (since the evader is most likely lighter, and I'm willing to bet has at least a somewhat better transmission in terms of efficiency). The price is attractive too. If you're willing to go higher voltage, a whole slew of possibilities opens up (runtime can increase, lower operating temperatures if set up right, and way more power on tap).

You do realize that a stadium truck doing just 40mph gets a little uneasy at speed, right? I would hold off on going above 45mph until you learn to drive the Evader and get a better feel for it. I've run my Rustler on 12 cells and an HV4400. That was pretty wild, and I had it geared on the mild side too (plenty of room to gear up!).

[evaderst69]

im not worried about the speed my first truck an assiociated t2 was my unlce s old race truck it was set up with a reedy 9x2 motor and geared for speed and it was damn fast.. i had no trouble with that and should be fine with this one too

[ElectricThunder]

Brushless has a lot of torque. Keep that in mind.:D

But anyways... Go with the Traxxas when it comes out. You should be able to gear it pretty high (like....9:1 FDR- that's what the VXL Rustler comes with out of the box I think, or something around there) and still wheelie provided you run good batteries.

[evaderst69]

another thing i like about the traxxas system is that you can run any brushed, sensored brushless or unsesored brushless motor so i could upgarade to one of the faster novak motors or run one of the mamba motors.. so im just gonna get it and run it on the 8 cell pack i posted earlier and if i have a need for more speed which i prolly will ill upgrade the motor to somethin different

[ElectricThunder]

You can do that on the Mamba too (there's supposed to be a firmware update to run the novaks even better too). The max also runs brushed. They have the same basic features; it's all "flavor" now and tunability.

[evaderst69]

oh yea i forgot about the program update they are coming out with.. oh well im just goona stick with gettin the traxxas system and once i get used to it ill prolly get the novak 3.5 for some crazy speed.. will the novak run properly on the 8 cell battery or is it strictly 6 cell batteries

[ElectricThunder]

oh yea i forgot about the program update they are coming out with.. oh well im just goona stick with gettin the traxxas system and once i get used to it ill prolly get the novak 3.5 for some crazy speed.. will the novak run properly on the 8 cell battery or is it strictly 6 cell batteries

The 3.5R is best kept on 6 cells. Running that motor on 8 cells is going to make it ridiculously current hungry, and it will probably overheat. Just stick to the traxxas motor for a while, and throw some more cells at it if you want to go faster.

[SpEEdyBL]

Once you get the traxxas system you'll be able run the higher turn novak motors on more cells. You might be able to run a 4.5R on 8 cells or a 5.5R on 3s lipo, which would give you some rediculous speeds.

[ElectricThunder]

Once you get the traxxas system you'll be able run the higher turn novak motors on more cells. You might be able to run a 4.5R on 8 cells or a 5.5R on 3s lipo, which would give you some rediculous speeds.

True. I just wouldn't do that with their hottest wind motor (the 3.5R).:eek:

[GSMnow]

I just want to know where you plan to run a 55 mph rc car? Do you realise how fast that is? I have had my XXX-T up to 45 mph and it is crazy insane speed that eats up huge distances in a big hurry. I am geared down to just 35 mph now so I can drive it on a real track. It is plenty fast to stay with the Nitro guys and it out pulls them from low speeds and runs for over 12 minutes on 6 cell IB4200's. By the way, I run a Mamba Max 5700. It is a very flexible setup that will run over 40 mph on 6 cells in anything with proper gearing and with a 3S LiPo or 10+ NiMh cells it will easilly run to 60 mph. The 7700 may turn more rpm on 6 cells, but it does not make as much torque. Work your rpm back from the tires. Find the motor that will go the speed you desire with some room on each side for adjustment. I probably should have gone with the 4600 as I am down to a 15 tooth pinion on my 5700 now.

[welshy40]

guys, worth pointing out that there is a way to keep the esc cooler. I am buying a novak (the black one as its stronger) fan and will be making it fit onto the green heat sink on the Mamba max esc. I use it on a 4wd buggy and currently am using a Peak on a ratio close to 10.5 to 1.

[GSMnow]

Yeah, with the 110F heat we have been having here, I am running a 25x25x10 mm fan on my Mamba Max. It is a perfect fit, some 2.5 mm self tapping screws, about 15 mm long and they thread right between the heatink fins. I have it running off of the BEC output frmo the ESC as it is a 5 volt fan. It dropped my ESC temp from about 160F to 130F. I also run a clip on heat sink around the motor can on my CM36 5700. It dropped the motor temp from 170F to 160F with no fan and less room around it. I can rig a fan above it, but it will be my rear bumper as well. I thought about using a radial blower and running a tube through the rear shock tower to the motor. The ones I have are all 12 volt and pretty heavy. Propbably not good for racing, but maybe worth it for bashing with an 8000 LiPo and gearing for 60 mph. Right now I am geared a very easy 14.62:1 with standard stadium truck tires, just under 4 inches high without ballooning.