RC-Monster Forums - mamba maxx is shipping woooo hoo

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- - mamba maxx is shipping woooo hoo (https://www.rc-monster.com/forum/showthread.php?t=3469)

Quote:

Originally Posted by sleepy23

i am trying to go around and hit most of the threads i am subscribed to, the mamba 770 came in today and all i can say is DAMN....
most here are not familiar with my t4, but lets just say its about the most custom and insane stadium truck around...
ok, popped the 7700 in and took it out for a quick run on a 2s lipo that hadnt been charged in a couple of months ( i was just planning on tooling around, nothing big). i was out driving around and of course punching it a bit to see how hard it hit. so basically with the punch control still on, it was spinning the road rage tires for about 2ft before finally looping around, well during this process of tire spinning, i managed to break a titanium rear axle in half. there were no jumps, no crashes, no acts of God...just pure power from a half dead lipo hooked to a bada$$ motor...

So thats you in the rcu, i thought so

yep, thats me.. i usually spend most of the time there, then stop by here and rc10t4.

That's outragous! To break the Ti axle expecially given the lack of traction! Wow.

how would you know what the right set-up is for you?

Controller Only Mamba Max ESC Only - no motor included
4600 Package Mamba Max ESC and CMs-4600 Motor (540 size, 4600Kv)
5700 Package Mamba Max ESC and CMs-5700 Motor (540 size, 5700Kv)
7700 Package Mamba Max ESC and CMs-7700 Motor (540 size, 7700Kv)

i know what kv is but how mutch? #(kv)??? whats the best choice for an e-revo or maxx?

The first release is not intended for monster truck apps. The forthcoming "Monster Mamba Maxx" is what you would want. The above part numbers are for staduim trucks, buggies, Touring Cars, etc. All of the 6-cell/7.4v crowd.

Also, The concensus seens to be:
Look for a motor that has a 1600-2100KV rating. With the standard 14.4V Maxx set-up you end up with 23,000 rpm to 30,000 rpm output vs the stock titans which I believe max out at 19,000rpm. You can add batteries (twin 7-cell or 8-cell packs) for additional rpm and power output. The wattage output on the Titans is 119 per motor or 238w total. Most of the brushless motors produce 700 - 1400 watts in comparison. You end up with a ton of extra torque and a significant increase in top speed. It's been suggested by many I've talked to to keep the max motor rpm below 40,000 to save your running gear (trans, diffs, cvds ,etc.) plus it keeps the amp draw down which is easier on the controller, batteries, and motor.

Hope this helps.

they didn't really say anything on normal nimh battery just 3 s lipo.

Well based on 7700Kv and a 3s Li-Po which produces 11.1v (3.7 x 3 cells) the end result is 7700 rpm/volt x 11.1v = 85,470 rpm!

Even with the 4600 it's 51,000+

A 2s lipo is more appropriate which is 7.4v and nearly the same the std 6-cell packs and would produce 34,000 rpm for the 4600 and 57,000 on the 7700kv model.

ya, can you push over 3s lipo with that? which is close to using 7 or 8 cell nimh?

What you really want to do is go with something like the Warrior 9920 and the Feigao 9L or 9XL or the next step would be a Quark Monster 125b and either the Feigao 9XL or the Lehner 1950 7 or 8-Turn. These combos are far better suited to use 3s, 4s or 5s. My plan is to go with the Quark Monster 125b, Feigao 9XL, and initiall 8 NiMH which will be replaced by (2) 5s packs with a minimum of 3000mah.

Lehner Motor Specs Chart

Motor Power(Watts) @ Amps RPM's / Volt Weight
1940/6 1400 Watts @ 50 Amps 2613 290g
1940/7 1400 Watts @ 50 Amps 2239 290g
1940/8 1400 Watts @ 50 Amps 1959 290g
1940/9 1400 Watts @ 50 Amps 1742 290g
1940/10 1400 Watts @ 50 Amps 1568 290g

Feigao / Nemesis Blue Motor Specs Chart
540 - S,L,XL

Wind rpm/v

540 L
Size - 36mm x 61mm
Weight - 282g rpm/v
540 XL
Size - 36mm x 75mm
Weight - 372g

S L XL
6T 5915 4096 2779
7T 5070 3511 2382
8T 4436 3072 2084
9T 3943 2731 1853
10T 3549 2458 1668

The info below is directly from the Mamba Maxx Tuning guide. You cant just throw 3s on the 7700. Youll blow up the motor. But, from the recomendations, it sure doesn't seem like they are worried about pushing the 65000 rpm limit of the motor

This is my favorite quote... ''In internal and beta testing, we were unable to find gearing options that would actually thermal the controller when used within spec:''

So in theory, you could gear your truck to have retardedly high top end for some silly speed runs. Granted the acceleration will suck.

Quote:

Where are the “real” limits and what is the fastest?

In internal and beta testing, we were unable to find gearing options that would actually thermal the controller when used within spec:
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.

So how can you get the most speed? You might think the 7700Kv motor having the highest Kv would automatically allow you to have the fastest setup right? Let’s find out:
7700Kv x 2 cell lipo voltage (max with this motor) = 53,900 motor rpm.
5700Kv x 3 cell lipo voltage (max for the motor and ESC) = 59,800 motor rpm
So the fastest 5700Kv motor setup is actually 6,000 motor rpm faster than the fastest allowable 7700Kv motor setup!

Now if you are racing with 6 cell packs only, then obviously the 7700Kv motor will be the fastest option for you, but we are routinely asked “what is the absolute fastest setup for my car/truck?” The answer in this case, is the 5700Kv motor with a high quality and high output 3 cell lipo pack made for 10th scale cars.

The one area no one talks about is drivetrain rpm. I've talked with several people who ran high rpm brushless in their touring cars and off-road buggies only to find out that they regularly "blow up" with the high rpm usage! Highly modified brushed motors hit peak power around 15,000 - 17,000 rpm and probably wont spin past 27,000 - 30,000 rpm so looking at a brushless rig that can spin more than double logically sounds like trouble! Not to get to technical but the drivetrain vibration/harmonics of that kind of rpm without careful attention to balance and assembly tolerances, not to mention bearing speed ratings would be a problem. I don't doubt they come apart. Most everything mechanical has limits. You wouldn't take that new Z06 Corvette you bought and rev it up to 12,000 rpm and expect it to live would you? How can you expect an rc car to handle 2-3 times the rpm the engineers could have anticipated!

Sorry for the long winded post, but think about it..............

Quote:

Originally Posted by Procharged5.0

Thats how all of the aftermarket companies stay in business. If that wasn't the case companies like UE, Robinson racing, MIP wouldn't be in business. Seems to me that this is what a large part of the forum is discussing... Upgrades to the rest of the model to handle the brushless power.

Fortunately I started with the mechanics and worked my way up to the brushless so hopefully I won't suffer from breakage!