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-   -   mamba max very weak braking...why? (https://www.rc-monster.com/forum/showthread.php?t=22445)

eovnu87435ds 07.23.2009 11:16 AM

It smells fine to me. the properties of inertia work in both directions. if it is geared too high, not only will it be hard to start moving, but to stop as well, since the wheels want to keep spinning

Arct1k 07.23.2009 11:25 AM

I think you all missed one - rebind the TX to the MM so that so that the MM gets the end points again...

emaxxnitro 07.23.2009 12:35 PM

Quote:

Originally Posted by Arct1k (Post 306803)
I think you all missed one - rebind the TX to the MM so that so that the MM gets the end points again...

+1 try this it may work.

Andrew32 07.23.2009 02:09 PM

Quote:

Originally Posted by blueb8llz (Post 306719)
i have the newest firmware.

not what i ment. reload the firmware. mine had problems going from brake to reverse and i tried everything and nothing work. I just reloaded the firmware and poof...started working.

redshift 07.23.2009 04:54 PM

...You have air in your lines, must bleed.

:mdr:

blueb8llz 07.24.2009 12:16 AM

Quote:

Originally Posted by Arct1k (Post 306803)
I think you all missed one - rebind the TX to the MM so that so that the MM gets the end points again...

what does that mean? how do i do this?

Quote:

Originally Posted by MetalMan (Post 306748)
Have you tried a smaller pinion gear or different battery? My guess is the gearing is too tall and the motor isn't able to provide the braking force (torque) you desire.

this maybe the answer. because when i used the vileleon motor, i remember i was using a much smaller pinion. i think it was 8 tooth smaller! haha
well, ill try putting a smaller pinion and see what happens, but i wont be keeping it that way because im happy with the speed now.
but i still dont see how gearing so high makes it slow at braking.
my emaxx is geared super high as well and it stops on a dime with only 50% brakes with the mmm.

eovnu87435ds 07.24.2009 01:00 AM

lets say for example, the final gear ratio is 1 motor revolution is equal to 10 wheel rotations. if you want to get moving from a stop, it is hard on the motor, but once you are moving along its alright. this is because newtons law of inertia states that an object in motion wants to stay in motion, and a nonmoving object wants to stay non moving. when wanting to stop, the motor wants to stop those wheels from spinning, while the inertia of the car wants to keep the wheels rolling. this is where the wheels can easily overpower the motor, because of that 1:10 ratio.

All the clues fit here. you're geared to the moon, and have big big wheels on there. This means it is hard to get the vehicle moving 1. because of the high gear ratio and 2. the additional rotational mass. once moving, the rustler is really trucking. it flies. all because it is already moving, and wants to keep moving. it doesn't want to stop because the motor cannot easily change the speed of the wheels(due to tall gearing) and the foward and rotational inertia wants to keep moving.

In the R/C world, this equals more amps being pulled to change speeds. when it is too much for the motor or speed conroller or batteries, they will start to fail. So while it may be fun and fast, it may not be for long. if you want to keep the high speed shenanigans, I would highly suggest investing in a medusa or neu motor. The mamba motors of this size are not very good, while a neu or medusa can give you more torque, speed, and efficiency.

blueb8llz 07.24.2009 01:08 AM

ahh i hear what your saying. but does this still come into play even when im going 5 mph?
because even going at 5mph. the brake's suck.

Metallover 07.24.2009 01:11 AM

If you were geared so high you could have damaged the motor from temps....

eovnu87435ds 07.24.2009 01:55 AM

physics-wise, yes, but it should not be as much as a problem as when you are faster

blueb8llz 07.24.2009 03:23 AM

Quote:

Originally Posted by Metallover (Post 307035)
If you were geared so high you could have damaged the motor from temps....

i just bought the motor used. i only ran one pack through it so far. highest temp was 162 then i let it cool down. and that was only that one time.

when i get a chance, ill try a smaller pinion and report back with results. its not a big deal to me, i just was wondering if i got scammed into buying a defective mm or motor, that's all.

Arct1k 07.24.2009 08:02 AM

Hold full throttle when you turn esc on - Wait until it flashes and gives you tones and goes to flashing red.

Then hold full brake - more tones and it should change to orange

Release throttle to neutral - lots more tones - done

The fact that you don't know this would imply that the MM doesn't know the end points...

SpEEdyBL 07.24.2009 04:59 PM

Maybe your packs are bad or a connection in the wiring is so bad that during breaking the voltage seen by the esc automatically gets detected and corrected by reducing the breaks. I know its a big stab in the dark but worth a shot! TBH, my tekin 632 3200 kv motor locks the wheels in my 4wd XXX-4 even with 20% brakes. Wierd huh?

J57ltr 07.25.2009 09:58 PM

Quote:

Originally Posted by blueb8llz (Post 307033)
ahh i hear what your saying. but does this still come into play even when im going 5 mph?
because even going at 5mph. the brake's suck.

+3 for metalMan's idea.

Its even worse at low speeds with a high Kv motor. I run a 7700 and when it it geared high (20/87) I have to up the brake so it will stop but when I run a much smaller pinion (15) I have to change the brake curve because it locks up to easily. High Kv motors don't put out enough back EMF to fight against, unless they are spinning faster (numerically higher gear ratio). They are going to have lower braking than a low Kv motor. II have to drop the braking from about 75% to about 40% when switching from my 7700 to say my 4436 Feigao using the exact same gearing.

Jeff

blueb8llz 07.26.2009 02:27 PM

Arct1k- i already tried that.
speedybl- i use the same lipos on my emaxx with no probs. and i dont see any loose wiring.

im pretty sure metal man's guess is correct. i just havent gotten the chance to try another pinion. been real busy with job. will try in a few days.


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