Direct Drive to Diff E Revo Build

[sikeston34m]

You know, come to think of it, you could be onto something Brian.

JohnRobHolmes uses them with his outrunners and Rock Crawler setups. Way LOW gearing but they work for him.

Perhaps the Quark has a different "kick in the pants" startup routine. I'm not sure.

[BrianG]

The Quark definitely has a different startup routine than a MM. Actually, I made a thread about that a while back noting the differences.

[lincpimp]

Originally Posted by BrianG

The Quark definitely has a different startup routine than a MM. Actually, I made a thread about that a while back noting the differences.

Also seems like the quark, when turned all the way up, can really provide some starting power. I had mine set for the outrunner in the redcat and then moved it into my ls10 with a feigao 12l on 5s lipo and it would lift the truck completely off the ground and flip it over. And that was with smooth throttle input, no stabs! I turned it down quickly, as I could see that I would be snapping some driveline components soon!

[zeropointbug]

Originally Posted by BrianG

Isn't there some kind of rule-of-thumb that states the motor has to spin a certain minimum percentage of its kv rating for the ESC to get the proper back-EMF pulses? Don't know if the same rules apply to outrunners, but it may be something to think about as far as cogging is concerned.

And HOLY COW that's a big motor! You plan to sit on your vehicle while you drive it?

Yes, but the outrunners have higher potential back EMF than a inrunner for given rpm... right?

[BrianG]

linc: The difference I noticed was with what happens if the motor doesn't get started (geared too high, too much load, etc). The MM progressively adds more and more power until it starts. While good to a degree, this could end up causing the ESC to go up in smoke if there is too much trouble getting that motor started since a motor can pull a LOT of current in its stalled state. The quark OTOH simply keeps trying to move the motor, but not with any more power than the "start power" setting. IMO, this is safer for the ESC.

ZPB: Yeah, that's why I wasn't sure if the same percentage applied to outrunners. I'm sure there is still some kind of value, just different. Makes sense that the motor would have to spin a certain speed to generate the needed EMF signals since a coil induces a voltage while in motion only.

[MetalMan]

I run a 14pole outrunner in my rock crawler on 3s Lipo using a Mamba 25. The motor's rated at 45amps continuous, and the little Mamba 25 runs it very well. Granted, the gearing is low, but I've run the truck geared for higher speeds as well. However, the Mamba 25 doesn't like that so much, and does sometimes have difficulty starting the motor. I blame that problem on the Mamba 25 being so small...

[Mod Man]

I can tell you that the HV110 has no cogging and runs phenominal with outrunners. Part of that is due to being designed for aircraft use (the brakes suck, though).

If you do not mind parting with some coin, the MGM Com Pro is the best running car ESC I have ever had. They have the best start up, are reverse capable, and run cool. But, they are super expensive and tough to get serviced if need be.

Matt

[aqwut]

I find that outrunners don't cog too often, except when using some cheapo ebay ESCs.. Seen the size of that motor, had a lot of batteries coming.. and couldn't resist picking one up.. and as for the 10mm and 12mm shaft, I now have a taig lathe.. so I can do something with it....

Sikestorm, that truck you have is just beautiful man..

what are the maximum RPMS an outrunner can take?.... about 12000rpm?

I got lost when you guys started talking about EMF pulses....

[zeropointbug]

It's more of a sine wave than a 'pulse', but while in operation, it is probably distorted somewhat... if it were running as a generator, then it would for surely be a sine wave.

[sikeston34m]

Originally Posted by aqwut

I find that outrunners don't cog too often, except when using some cheapo ebay ESCs.. Seen the size of that motor, had a lot of batteries coming.. and couldn't resist picking one up.. and as for the 10mm and 12mm shaft, I now have a taig lathe.. so I can do something with it....

Sikestorm, that truck you have is just beautiful man..

what are the maximum RPMS an outrunner can take?.... about 12000rpm?

I got lost when you guys started talking about EMF pulses....

You must be looking at Modman's truck Aqwut. I haven't shown my truck here yet. LOL

Yes, around 12,000 max. rpm's for this style outrunner. There are outrunners that are high speed though capable of 40,000rpms.

[Mod Man]

Most outrunners are capable of around 20,000 RPM. That is true for most Orbit outrunners as well as AXIs. That is due to magnetic saturation. Beyond that heat tends to build up and efficiency goes way down.

Much depends on each individual motor, though.

EMF is "Electro-magnetic-fequency". Back EMF is the back pulse the motor creates as it rotates. A motor requires voltage to run, but it also creates voltage as it spins. This voltage is read by the ESC to give a rough calculation of the motor's RPM thus eliminating the need for position sensing. Software is EXTREMELY important in eliminating cogging as is high torque capability of the motor. High voltage normally reduces cogging as well.

Matt

[sikeston34m]

Hey Modman Was that the AXI 4120/18 that you were running?

It's the only one that I see with a 515kv rating.

[sikeston34m]

I thought I would show you the difference in the Outrunner used in the E maxx 40mph setup (direct drive to transmission) and the AXI 4130/20 that is going in the Revo. Big Difference!

[Mod Man]

Originally Posted by sikeston34m

Hey Modman Was that the AXI 4120/18 that you were running?

It's the only one that I see with a 515kv rating.

I believe so. I will check it and get back to you. It is not here at the house.

That motor has alot of use on it. It started in a twin rotor helicopter, then it proceeded to run my truck, now it is running the head of my Taig CNC. :)

I love outrunners.

Matt

[sikeston34m]

Here's a few pics of the progress. Still in it's rough form. I plan to line the lower part of the battery tray with the "loop" side of some velcro. This will cover up the counter sunk screw heads and help protect those precious Lipo's.