mamba max very weak braking...why?
 

is it the motor or esc giving my rustler weak braking?
its a mamba max w/ 6900kv motor on 2s lipos geared 55 mph on a rustler with stampede tires.
at first, i thought maybe it's because of the bigger tires, but i put my friends vilenion esc and motor on 3s into my rustler with exact same setup, and the brakes work on a dime.

i could be going pretty slow and the brakes are still weak. i have the brake at 100% and even have 10% drag brake because the braking is soooo weak.
any clues???

maybe the brake setting on the radio?

Is the MM old? Maybe the caps are dead...? Does the motor get hot quickly? If the magnets are weakened then it will heat up quickly AND have weak brakes.

demagnetized motor?

im using the stock radio that comes with the mini rc18, i dont believe it has a brake setting. but anyways, i used this exact radio with the vilenion system and it worked great.

i bought the mm6900 combo used so i dont know the past, but he claimed it only had 10 runs hahah thats most likely a lie.
the motor doesnt seem demagged...how can you tell anyways.
it still has plenty of power, and goes fast..havent gps yet but looks around 45+
the motor does heat up pretty fast cus im geared soooooo high especially with them big o tires. it gets to about 150 degrees in 20 mins. so does this sound like a weak magnet causing weak brakes?
how can i check if the caps are dead?

Try your friend's Velineon ESC with your motor and see if the brakes are better. If not then the motor is probably fried. Keep an eye on temps just in case, so that you don't take the Velineon out, too. You might also try recalibrating the radio to the MM.

maybe the previous owner turned the brakes down in castle link? that might be your problem

good idea to try his vilieon esc but he left now. dunno when ill see him again haha. he lives pretty far from me. so there goes that idea.
so the motor can be fried even though forward and reverse speeds are great.??
i already tried recaliberating the radio. and i have the brakes at 100% on castle link.

What about the braking curve? It's on a different tab all by itself...

reload firmware. it may help.

i have the newest firmware. and the brake curve is in stock form.
o well, doesnt bother me that much, i was just wondering what the problem is.
but i do encounter alot of close calls because of the weak braking.
the funny thing is, i had the same problem when i installed a 6 turn brushed motor with a novak cyclone esc. and that braking power was even weaker haha. and that motor was almost brand new.
so now that i think about it, i dont think its the motors causing this.

My mamba max at 50% braking had enough power to cause my esavage to launch forward and somersault from top speed. 10% brake was wat I used in the past.

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.

+1 for metalMan's idea. try a setup with some stock tires if you have em, and take the pinion down a few teeth if you can.

no something dont smell right. any motor that is not demaged should lock at 100% brake

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

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.

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.

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

:mdr:

what does that mean? how do i do this?

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.

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.

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.

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

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

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.

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...

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?

+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

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.

What is your gearing? 87/19?

Jeff

no, try 86/25 hahah i told you i was geared super high.

It will go faster if you gear it down (numerically higher). I have a friend that has the same combo I have and he will eat my lunch if I am geared too high. You are geared for about 75mph, it'll never get there. For sure this is the reason you are have weak brakes. If my friend is geared 87/15 and I am 87/20 I can't even come close to catching him. We both run A123's and the 7700 in a rustler. It won't even pull a wheelie with that gearing in my truck
(87/20) Even his top speed is faster than mine if I am geared too tall. And I usually have to have 100% for the braking force and it will slow the truck from top speed but as the truck slows the braking force drops.

Jeff

I agree. When geared high, the motor is turning less per mph so the coils/magnets will have far less braking force. I bet you probably have max braking at high speeds only, but then gets weaker the slower it goes. Also, I wonder if gearing so high caused excessive motor heat and the magnets are starting to weaken?

yup, i think you guys are correct! i am geared so high its actually making my truck slower. i was wondering why my rusty seems so slow. ive had it for a 6 months now, but it only has like 45 mins run time hahah. never really have a chance to mess with it since im usually busy having fun with my other trucks.

it seems as though its only going about 45mph. and your right, it doesnt wheelie even with the slipper at the tightest. i would drop in a smaller pinion right now, but the rusty is outta commision due to some soldering i need done with the motor bullets. during the last run, i guess it got soooo hot, it unsoldered one of the motor bullets. when i get the time to solder it back, ill let you guys know the results with the smaller pinion.

Running when geared too high and/or with a partially demagnetized motor will harm the ESC and even your batteries. The coils need the rotor spinning to develop back-EMF and if the magnet is weak, those coils are looking more like a straight piece of wire.

Unless the solder joints were done crappy, desoldering wires is a sure sign that wayyy too much current is being pulled.

so i finally got the chance to solder the motor wires back (been very busy and non rc status) and the ones that said i was geared too high, was correct. i was geared 25/86 with a 6900kv mamba in a rusty with stampede tires/wheels.

i put in a 19t pinion and it has maximum braking now. itll do those 180 to 360 degrees spins when i brake now .
but the top end still looks to be about the same speed. but the low end is defininetly punchier. but still no wheelies.

im gonna try a 16t pinion and see if that will make my top end quicker. if what j57ltr is true about gearing lower for more speed (two post above) then it should do the same for my rustler.