maxn

Depends where you live - around here you can leave your car unlocked, heck you can leave your house unlocked !

When I lived in the UK I had my cars broken into just to get a couple of pound-coins left on the passenger seat !

I keep an M03 in the boot of my Mini along with a 12V charger and TX......

But, back to the original posts - despite running only NIMH batteries and a fialry softened ESC 'tune' the brushless motor not only out-performs any brushed motor I have used, but it is maintenance free, add to that the tuning potential and I absolutely will not go back - I fully intend to make the switch for everything other than spec-racing.

RURC

In garage, gated community, neighbor across street is THE chief of the sheriff department, alarmed, armed and dangerous owners with permits to carry (me and my lovely wife), lovely German Shepard named Rokko got him from through sheriff across the street, the truck comes with a cover that covers the storage area so you cant see them, and I have insurance as the last resort. Those with a death wish are welcome to give it a try. If the dog dose not get you one of us will. Besides you ever try to break into a H1?

morespeed

RURC,
Big concern here about battery connectors. right now i'm using power pole connectors
on my ni-md batteries. can i use these on the 3s 5000 lipo or will they melt. i can't find anywhere what the are rated at. i read that they are 3 times less resistance then deans.
i do have deans also, just not using them. tried them few times and they were kind of a
pain in the butt to solder and unplug.

will the MM5700 and 3s 5000 smoke um.

mbeatle

Resistance of powerpole/sermos connectors is less than the 12 awg wire you'll solder to them, so you won't have a problem with the connectors.

morespeed

RURC
thanks for the info. got another for ya.
charging nicd or nimd batteries. how do i ask this? let's say if you charge a battery at 2amps
and one at 5amps, which way is best for the motor.
A. slow charge longer run times. may run hotter cause motor is not running max rpm
B. fast charge less run time. run cooler cause motor can max rpm.
C.i know gearing has lots to play also,

reason i'm asking this is because, nobody has talked about what they charge there's at on here. could this be why the Mamba max motors are running hot also.

see, lipo's are another class of there own. compared to nicd and nimd.
some people have used ni md on here and everything is ok and others are smoking them.
i'm curious to what people are charging at. and what truck and gearing they are using.

RURC

There are several different Power Poles that will each handle different amperage. So I dont know whic ones you have . The ones generally available do not handle the power. I suggest you switch to 6mm Schulze connectors. They handle 200+ amps continuous. I know that they are not as dumb proof as Deans or Power Poles but just pay attention. Deans are good for 60 amps and power poles come in 30, 60, 100 amp sizes. In general 1/10 uses there will not be any problems but If you go larger there will be problems. THe Schulzes are the lowest resistance connector out. and the 6mm will work up to 10 gauge.

RURC

I have melted both PP and Deans connectors, even the 100 amp PP. That is why I have switched to the Sculze connectors. These are a 6mm version of the same connector that you get on your brushless motors.

morespeed

Thanks RURC,
when i ordered the lipo i also order the sculze connectors too. i saw that you recommended them in some early posts. just thought i would ask about the deans and powerpoles just to be on the safe side.

morespeed

hey Maxn
i'm with you 100% on the not going back to brushed motors.

robbie303

Since my BK9920/Feigao set blew-up in 5 minutes after I installed it, I've bought the Mambo Max 5700 combo.
RURC has been writing very positive/knowledgable things about the Mamba Max, and that made me decide to choose it above the Novak.
The thing however is that CastleCreations says the MM is not suitable for 1/10 scale monster trucks. No more explanation.
I phoned support and asked why's that ?
The person was very helpfull and explained that Brushless engines do not have a limiting resistor (the brushes) as motors with brushes do have.
Since the absence of the brushes, brushless engines are able to consume more current then brushed motor's. When a lot of power is asked from a brushless motor, it will be able to give it, as to a brushed engine will only be able to give less and less at higher powers.
So, since the Emaxx is to heavy, the MM might get to hot. That's the reason why CC says it's not suitable for the Emaxx.
So, the guy suggested that I put the batteries in parallel !
With that, the motor+ESC would run on 7V instead of on 14V. This would squareroot the maximum power the motor+ESC would be able to consume from the batteries. Power = Voltage * Voltage / Resistance
Running on 7V would greatly limit any possible extreme currents.
However, running on 7V would (I think) also lower the efficiency of the motor+ESC a bit. This is because the motor+ESC will work on a smaller Voltage, but still need the same drop voltage for them to work.
So, setting batteries parallel with a Mamba Max on an Emaxx would:
- Limit the power consumption during extreme usage.
- Lower the efficiency a bit.

Now my questions is: Do you think the temperature on the motor&ESC will be lower when running on 7V instead of on 14V ?

Access

Totally wrong. Run at the highest safe voltage, and if it gets too hot, gear it down. For an E-maxx, gear it way down (11/66 is the lowest I can take it). I have a 5700 in my E-maxx: videos here
http://www.youtube.com/my_playlists?p=9F829869AA869E90
with a custom cooling system, air-cooled and using 80mm 12V fan to blow air over the ESC and motor.
Run it off 12 NIMH (12V) and don't expect a great amount of top speed, check the motor temp often esp. if you don't have an active cooling system (forced air or liquid-cooled). I wasn't looking for super high speed, just to replace the twin titans as they had pretty much worn out.

Running it off fewer batteries, while gearing it higher (to get similar top speeds) will generate more heat, not less. You want high RPMs (as for as the motor is concerned, torque = current, so more RPM geared down is better than less RPM geared up). When I first made my mamba max E-maxx setup, I had the same gearing and ran off only one 6-cell NIMH. Top speed was barely 15mph, and geared even 13/66 the motor got way too hot too quickly. The thing that inspired me to make the setup in the first place was this video:
http://www.youtube.com/watch?v=nD-nJS9gqp0
of Shawn riding around in the mamba-powered barbie jeep.

RURC

The real reason they dont recommend the Mamba Max for trucks is the dreaded warranty. It has not problem running these things. I use it in 1/8 , 1/6, 1/5 cars and we do just fine. Not your run of the mill conversions on the 1/6 and 1/5 but that scale none the less. They also tell yo that you cant run it above 11.1 volts. Well I run them at 22.2 and there has not been a problem. Just dont go higher than 22.2 it will let the all important smoke out of the system. To be real safe stay at 5 cell lipo and below. I generally build the large scale cars to run at 4 cell lipo. Then I can go faster if I want and goto 5 cell or make it more manageable and drop to 3 cell.

robbie303

Are you guys really sure, that going to a lower Voltage will not give lower temperatures, even though CastleCreations support told me it would ?
Torque = current. That sounds logical though.

The BK9920/Feigao setup which I bought from KershawDesigns, blew-up after 5 minutes of light usage.
At half throttle, often it wouldn't spin, but instead start pulsing and make strange robot noises. Like it had strouble starting-up.
Even in idle state (no servo's, and motor not running), the BK9920 ESC sucked 400mA of current from the batteries and became quite warm.
A standard Emaxx in idle only sucks 100mA, and that's including the receiver.
So, I think the BK9920/Feigao setup I received from KershawDesigns was defective right from the beginning.
Do you guys know what a MM setup sucks when standing still ?

RURC

Telll me who you talked to. I will call him to be sure HE was not mis understood. If he thinks as you say I will call Patrick DeCastle and inform him that there is a problem in the tech department.

I promise you that the higher you go in voltage the lower current (amps( you draw and therefore the lower the temp. Current = temperature, the more of the one gives you more of the other.

The problem you describe on the BK 9920 sounds like either wiring or real cogging to the point of destruction. The noises are generally made by the motor. Something is wrong here with that. I have 5 BK 9920 and they work flawlessly with the occasional cogging. Cogging can ruin a esc.

RURC

I saw Shawn on Wednesday. He is as ugly as ever. I was picking up my next project Schumachers from him.

Access

Look at it this way. If you are making a 10-pound truck go 30mph from a dead stop, two things happen. First the truck accelerates from 0mph to 30mph. This draws lots of power but only lasts a few seconds. Then you keep a level speed at 30mph. The energy going into the system (power) is being used only to overcome the friction of movement (transmission resistance, air resistance, etc.), plus some waste heat in an imperfect world. Now the physics of doing these two things are the same, no matter what is on the inside of the truck. The physical energy over time, or power, you have to deliver to keep the speed is a constant.

You can go 30mph with the 5700 motor, geared 11/66 on 12V.
Or you could do it with the 5700 motor, geared 22/66 on 6V.
Or you could do it with the 7700 motor, geared ~16/66 on 6V.
or so on. The first setup will perform the best (fastest acceleration and no receiver dropout or anything like that).

But they all have to provide the same amount of power once you reach your top speed.
I've always gone for highest voltage, highest RPM, and lowest gearing I can, I find this makes for the most efficient setups.
There are pleanty of reasons to stay away from the second and third setups, especially when you are pushing the system.

robbie303

When you do not ask power from a motor (brushless or not), the motor will not suck a lot of current.
But, when power is asked, it will lower it's internal resistance and start sucking more current, untill the point where its internal resistance is at its lowest, this is the point where the motor is delivering all it can, its maximum. (this can be at any RPM)
Since brushless motors have no brushes, their internal resistance can become very low, and thus the maximum current can become much higher then with brushed motors That's why brushless motors are stronger.

If you lower the supply Voltage, you lower the maximum power any motor can deliver. (Power=V*V/R)
For example: If the lowest resistance which a particular motor can become is 0,2 Ohms, then at 12V it can deliver maximum 720Watts
Now if you run it on 6V, it can only deliver 180 Watts.
So, going from 14V to 7V will squareroot the maximum power your setup can deliver.
So, when asking MAXIMUM torque from the truck (this is something else then full throttle), the 14V truck will suck 2 times as much current, deliver 4 times as much power, and will be 4 times as hot.

But, when you stay UNDER the maximum, the following is true for a truck running at any speed:
- On 7V, the motor will consume double the current as compared to running on 14V.
- On 7V, the motor will run the same RPM as running on 14V.
The higher the current through your motor, the higher the temperature of your motor. (Power=I*I*R)
Thus at NONE maximum torques, when running at 7V, the temperature will be 4 times higher then when running on 14V.
And also, the efficiency of the ESC will be lower because the ESC still needs the same drop voltage, which will higher the temperature even more.

It's reasonable to assume that during normal usage, the motor will rarely work at it's maximum.
So, conclusion:
Running 7V instead of 14V will give much higher temperatures.
The powerline distribution companies allready found this out long ago, when they decided to transport current on the highest voltage possible.

I can't remember the name of the support person of CastleCreations.

Access

No. You cannot use DC electronics theory to explain your motor. A "DC Brushless Motor" is using chopped DC or essentially AC. This is why you come to many false conclusion in what you say above. Like the statement "On 7V, the motor will run the same RPM as running on 14V." Likewise internal resistance of the motor does not change. It is a constant, and for a good motor, it is always very low. It's just like if you buy an "8-ohm" speaker or a "4-ohm" audio speaker. The internal resistance is close to 0 ohms. The "8-ohm" is a measure of impedance, not resistance.

The current limit comes from the ESC, not the motor. If you look at it from the ESC's perspective, whether you are running at 6V or 12V, you can suck 100 amps either way (continuos). So at 6V you may max out at 600W, at 12V you may max out at 1200W. This is why you can hook a novak motor to the mamba max ESC and it runs better than on the novak ESC. If the motor and the ESC is well-designed, internal resistance is a non-factor here.

The AC theory is complicated to explain but the gist of it is this.

- High voltage helps to (quickly) overcome the impedance in the motors coils so it makes the motor spin faster. Fewer turns means less impedance, more KV, the motor will spin faster.

- When 'torqued', in order to keep spinning the motor has a magnetic field generating opposing force. This draws current inverse proportional to the number of turns. Fewer turns (more KV) means that more current must be drawn to provide the same magnetic field strength.

So essentially you can have the same amount of torque (at the pinion) with 6V or 12V. But the 12V will have twice the RPM. If geared the same, the 12V will be twice as fast. If geared down to the point where the speeds are the same, the 12V would have twice the torque / acceleration.

RURC

Thank you ACCESS I didi not feel like typeing that much

robbie303

Access, I really appreciate your help and time. But at some points you are wrong or misunderstanding me.
So, please don't say I come to many false conclusions if the only one you pinpoint to, you are the one who is having it wrong.

Different RPM ? Don't think so.
I said at ANY speed. Thus if for example, the 7V and 14V trucks both run at 20M/H, with the same gearing, the RPM will be the same. Period.
How can the motor of a car which is running at the same speed with the same gearing run at a different RPM ??
The idea is to compare a 6V and a 14V truck. If you compare them, you must ask THE SAME TORQUE from both of them !
In other words, what we want to know is: "at the SAME SPEED, which one gets hotter ?"

The maximum current is determined by the sum of impedances of Motor, ESC and cable.
The motor its resistance is built from 2 components:
1) The resistance of the wires inside the motor.
2) The resistance created by currents inducing a magnetic field.

Anyways, the END conclusion we agree on, so no need to say things like I'm totally wrong.
I also think the 7V truck gets hotter then the 14V truck.

Slo-V Flyer

I get what you mean by motors spinning at the same speed, but you didn't say it that way the first time. Makes sense, if the trucks are both going the same speed, then yes the motors attached to them would be spinning at the same rpms, geared the same that is.

Lilredmachine

I don't see why maths or motor theory need come into this.

7.2v = crap.
14.4 and up = good.

There is no argument, no need for essay posts referring to this or that.

14.4v will be faster, period. Don't even think of running an E-maxx or similar on 7.2v, it'll barely move.

Slo-V Flyer

I actually just did run my E-maxx briefly on 7.2v last night to test out my new Feigao 9L motor, since I need to make a dual battery Y harness for my MM esc and motor connectors (I just shoved the motor leads into the ESC plugs...). On my half dead 6-cell IB 4200, geared 12/72, it was able to pop the front or rear off the ground in 1st, and slightly less in 2nd. I'm sure it'll only go like 10-15mph, but I'm thinking of running it on 3S lipo, or 12-cell Nimh anyway, so it was just a test to get over the excitement.

Lilredmachine

Hehe, glad to see it's looking up for you slo-v. That's gonna be a sick setup when you get the cells sorted.

Slo-V Flyer

Yeah thanks, actually I just came back from running it for a good 10 minutes from a fresh charge. Same gearing, on 7.2v IB 4200, pops wheelies in 2nd. But man does it go slow, of course, like something around 10mph in 2nd. Haha. The best part is (not recommended) I don't even have connectors soldered onto the motor wires, and it showed when ever I gunned it in 1st, it would sometimes hesitate as the connections weren't letting the amps pass through.

According to my DTX temp checker, the motor reached >120'F, and ESC was a few degrees cooler, batteries were hot from the charger to begin with, but stayed around 110'F. Batteries after this are at 8.0 volts. Yeah I definitely will have a wheelies popping machine on 12 cells just as soon as I figure out I do or don't need a UBEC for 12 cells for sure. Hopefully I'll hit the LHS on my way to work and get them Deans and some 12g wire for a Y harness.