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Old 05-14-2007, 08:02 PM   #1
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Default confused about 6900 kv mamba

ok, it says in the description on the website that it does well with 6 cell nicad and nimh packs and great on 2s lipo. but then when i went to buy it it said NOTICE: the 6900kv and 7700kv motors are subjected to 8 cell packs. so whats the truth??????
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Old 05-14-2007, 08:14 PM   #2
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you cant run more than 8cells with it and no more than 3clipo.
my 5700 is the same but real do you want too

Last edited by wallyedmonds; 05-14-2007 at 08:29 PM.
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Old 05-14-2007, 11:29 PM   #3
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I believe the Castle site actually says that the 6900 (and 8000, for that matter) are limited to 8 NiMh cells or a 2s (not 3s) lipo. A 6-cell NiMh is fine.

The 5700 can handle up to 3s lipo and ... had to check ... 12 NiMh cells. I think this is also the limit of the Mamba Max esc.
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Old 05-15-2007, 01:39 AM   #4
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Quote:
Originally Posted by apenn
I believe the Castle site actually says that the 6900 (and 8000, for that matter) are limited to 8 NiMh cells or a 2s (not 3s) lipo. A 6-cell NiMh is fine.

The 5700 can handle up to 3s lipo and ... had to check ... 12 NiMh cells. I think this is also the limit of the Mamba Max esc.
That is correct, that is why they say the 5700 is the fastest because it is the fastest motor that can handle 3 cell lipo and can go 60+ mph with a 3 cell lipo

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Old 05-15-2007, 06:51 AM   #5
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You just have to stay below the Max RPM rating of the castle creation motors! Thats why the slower kv motor spins faster with more juice...Max input voltage for ESC: 3s lipo or 12 cell NiMH/NiCah
Max RPM for CM36s motors: 65,000 rpm
4600Kv motor max voltage: 4s
5700Kv motor max voltage: 3s
7700Kv motor max voltage: 2s

The Kv of a motor is the number of rpm’s it will turn per volt of input. So the 4600Kv motor will turn 4,600 rpm per volt of battery. On a 6 cell pack we can presume good cells are holding around 1v per cell, so 6v x 4600Kv = 27,600 motor rpm. If we use a 4s lipo pack, lipos carry about 3.5v per cell under load, so 3.5x 4 = 14v. And 14v x 4600Kv = 64,400 motor rpm . This is right at the top of the motor rpm limit and is OK, but is beyond the voltage limit spec of the ESC and cannot be used.

On the other hand, if we take a 3 cell lipo pack with the 7700Kv motor, that gives us 10.5v x 7700Kv = 80,850 motor rpm which is safe for the ESC, but well over the safe motor rpm limit so it cannot be used either.
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Old 05-15-2007, 02:56 PM   #6
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ok, so im running 6-cell nimh packs, but if i want to go lipo, which is the faster motor?? o and what is ur guys suggestion on mamba motor. it will be going into a xxx-t
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Old 05-15-2007, 05:33 PM   #7
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5700kv with 3s lipo is what castle says will give the highest RPM's and not exceed the limit of motor. I think the 5700 will be perfect for a 1/10 stadium truck. And if its not you can blow'em away with a simple LiPo upgrade!
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Old 05-16-2007, 01:58 AM   #8
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Quote:
Originally Posted by TH691
ok, so im running 6-cell nimh packs, but if i want to go lipo, which is the faster motor?? o and what is ur guys suggestion on mamba motor. it will be going into a xxx-t
If you are going to be running 3 cell lipo you can only use 5700 or lower. If you are going to run nicad/nimh cells I wouldn't go no faster than a 6900 but even that will be hard to control in a 2wd stadium truck. Remember though, if down the track you want to run 3 cell lipo you can just buy a 5700 motor

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Old 05-16-2007, 04:36 AM   #9
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Guys,

can I easily make 60+mph in a touring car ( Cyclone, T2, etc) with the Mamba Max 7700 setup?

It seems very possible, theoritically.
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Old 05-16-2007, 07:52 AM   #10
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I wouldn't think that would be a problem.. 7700kv x 7.2volts= 55,000 RPM.
With a peaked battery it should be closer to 61,000 RPM. The only problem would be gearing/ heat...I don't think mamba's have a problem over heating. but if you gear it to do 60 MPH, it may run hot.?
I would also keep in mind that Novaks 3.5 turn brushless system turns an amazing 10,500 kv...Wow...
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Old 05-16-2007, 08:15 AM   #11
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But the 3.5 makes a 10,500 rpm/v at no load.
The Mamba Motor makes a 7700 rpm/v under load.
The 3.5 would give a similar KV to the Mamba7700 if it goes under load. Not to mention that the Novak is quite weak and ineffecient in comparison to the Mamba Max.
The real BOMB is the Lehner 1920/4 which makes an incredible 7838rpm/v under load. This one is plain superior over the Mamba Max and the Novak, but it's three times as pricy as the others( $240!!!). Well worth every penny, though.
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Old 05-16-2007, 08:26 AM   #12
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I would definitly say that the Mamba 7700 would be sufficient to reach 60 in a touring car...Hell I almost had my xxx-4 going that fast...but that didn't last long..
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Old 05-16-2007, 09:08 AM   #13
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Why? did you break you car or fried your setup?
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Old 05-16-2007, 02:17 PM   #14
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yea, i do plan on running lipo, but couldnt i just run 2 cell lipo in the 6900kv??? o and can the 6900 handle 6-cell ib 4200 nimh?
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Old 05-16-2007, 02:26 PM   #15
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i run 3cell lipo with my mamba 8000 all day long no problems.

kyle
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