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  #1  
Old 04-27-2007, 07:27 PM
bumbaiboi808 bumbaiboi808 is offline
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Mamba 5400

Just installed a Mamba 4200 in my son's 18MT and it seems a tad bit slower on 6-cells than the 370 that it replaces. At first I thought it was my imagination as I was the first to try it out after I installed it while my son was at school. But when my son came home, he tried it and he said it isn't any faster than the stock 370. He's 5 and he can tell. I didn't do anything else to the truck except exchange the motor and ESC so everything else is the same. I taped a Garmin GPS unit to the the truck and it maxes out at 15.5 MPH. I'm pretty sure it used to go around 17 or 18 MPH with the 370. Can anyone verify the stock speed for the 18MT?

Anyway, since I installed powerpoles on his ESC and batteries, I tried connecting two of his 6-cell packs together to run 12 cells. Granted, it is much faster this way, and my son is barely happy with it, but running two 6-cell packs on this little truck is not practical. The body can't even fit when running two 6-cell packs this way. BTW, it clocked 24.5 MPH with 12 cells.

I have a 3S lipo for my 1/10 truck and connected it to the 18MT just to see how much the tires ballooned while holding the truck in the air and going WOT. The 12 cells balloon the tires more noticably than the 3S in comparison. This suggests to me that even a 3S lipo will run slower than the 12 cells. I am unable to run the 3S on the truck since it's too big and probably weighs as much as the 18MT so I don't have a clocked speed for the 3S.

I figure that increasing the size of the pinion will produce higher speeds, but how much will that affect the heat of the motor and accelleration of the truck? Would just getting a 5400 be a better alternative? My son is happy with the torque the 4200 has. Will the 5400 have less torque or more?

I know I should have posted these questions about which motor to get before I bought one...well, live and learn is what I say. Please post any suggestions you have.
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  #2  
Old 04-28-2007, 12:20 AM
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sescallier sescallier is offline
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4200 should be good, just put in a 3 cell lipo, and do something like a 16-55 gearing...



Should be a 30-35MPH truck in pretty short areas...



This rating motor and gearing is what the guys were using at RCmadness and they were hitting 32ish MPH on the straights...


Even though the 12 cells balloon the tires better, the 3 cell lipo would be waaaaay faster for bashing on the ground since it would be about 1/4 the weight of 12 cells...



I would do a 4200 with somewhere between 14 or 16 with a 60 tooth, and try the Agpogee li-mn 1500 pack, its a direct fit...


http://pfmdistribution.com/secure/sh...d=242&catid=61



I like the 4200 because its got great low end torque and runs for a very long time between charges...
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  #3  
Old 04-28-2007, 06:09 AM
bumbaiboi808 bumbaiboi808 is offline
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OK, cool. Very good info. I feel better with the choice I made now. I will try the gearing change and look into that lithium batt. Thanks a bunch!
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  #4  
Old 04-28-2007, 10:35 AM
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sescallier sescallier is offline
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Tell us how it works for ya...



4200 is my favorite motor overall...


Also you should get a good heatsink for the motor...



The heat sink I have on the mamba is from MPI, 20MM heatsink for fan unit,number ACC3922, it takes a bit of dremel trimming, but it fits perfectly then, really the perfect non fan heatsink.



When you cut off the recessed area it fits perfectly, this is the best non-fan sink for the Mamba...

Last edited by sescallier; 04-28-2007 at 10:37 AM.
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  #5  
Old 04-30-2007, 01:34 PM
bumbaiboi808 bumbaiboi808 is offline
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Update:

I decided to get a MaxAmps 3s lipo. Oddly enough, it seems that this pack will run the truck just as fast and quick as the 12 cells through the 4200. Still, when I WOT while holding the truck off its wheels, the 12 cell balloons the tires way more than the 3s. I guess that the lipo can handle load way better than the 12 cells.

Anyway, my son is really happy with his truck now. In fact, a wheelie bar is now on order since it is really easy to flip this truck on its lid now. I think I'll also gear up to 15 to tame the wheelies and get a higher top speed.

Thanks for all of your recomendations...they worked!
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  #6  
Old 04-30-2007, 07:32 PM
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sescallier sescallier is offline
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Sweet!


Even though the 12 cell might spin the wheels as fast, the lipo will be waaaaay better and have better runtimes...


Depending on how you gear it, you might want to consider a heatsink for the motor...


Basically run it for 20 minutes, then feel it, if its blazing hot consider a heatsink.


And if you eventually burn out the motor PM me and I can give you some recommendations on some 4200 motors that are better and cheaper.


Also you can adjust the starting power through the mamba, this can help alot with the wheelies, and also will help the drivetrain from wearing out too fast...



Anyways, give another report sometime and tell us how your doing with this.



Last edited by sescallier; 04-30-2007 at 07:34 PM.
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  #7  
Old 05-07-2007, 09:14 PM
bumbaiboi808 bumbaiboi808 is offline
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OK, here's a little update. I got a wheelie bar and installed a 15 tooth pinion. With the larger pinion, the 18 flies. However, I have a new problem. The truck doesn't track straight on hard accelleration. In fact, it will sometimes just spin out if I pull WOT from a stop.

I think it has something to do with the diff because if I readjust the diff, the problem goes away for a while then returns. I'm using the stock plastic diff tubes but have ordered MIP diff tubes and carbide balls. I'm hoping this solves the problem.
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  #8  
Old 05-07-2007, 09:22 PM
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sescallier sescallier is offline
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Always make sure the front diff is tighter than the rear...


Also your servo might be to blame...


Also you could install a gyro?
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  #9  
Old 05-08-2007, 02:10 AM
bumbaiboi808 bumbaiboi808 is offline
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Oh? Front tighter than the rear? I thought it was supposed to be the opposite. I will try tightening the fronts and loosening the rears.

A gyro? Hmmm...interesting. This is the first time I've heard of doing that. Where can I get one and where do I mount it?
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  #10  
Old 05-08-2007, 08:48 AM
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sescallier sescallier is offline
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If your rear is tighter thats why you are spinning out.



Get back to me about a gyro if this doesn't work.
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