Lowering BL Revo CoG.

[zeropointbug]

We're talking some explosive High Geared Torque coming from an Outrunner here. So Yes, the lack of a slipper is partially to blame for the problems. If there were a slipper, it could have been utilized with the setup. Inrunners don't have this type of Torque Period.

-IMO, I don't think that would matter would it? I mean if it's an inrunner of equal power is geared for the same speed, then the torque to the diffs would be the same, as all brushless motors have to the same torque curve (straight line)... and yah, it's too bad that any type of slipper can't be used with a setup like this.

There's a difference in the "flyboy" rating and our Land Vehicles. The Most Major one is airflow. The ability to shed heat is one thing that affects ratings alot.

-Completely agree with you on this one, cooling is basically the limitation to the continuous wattage rating (to a point), the better the cooling the closer the continuous rating will be to the peak rating. But still, that said, 2400watts for 440g is huge, so maybe the rating is taking into account that the components they use can handle high temperatures? However, that does not mean the efficiency would be very good at that output, if anything below average, maybe 85% or lower, whereas a Neu, IIRC, is roughly almost 90% efficient at it's rated output.


Another thought... I was just moving stuff around on the truck and was tilting the transmission 45 degrees one way and putting the motor centered in the chassis. Now if only I could make it work that way without heavily modifying the chassis to make room for it. If it could be done, then the motor would be centered, trans tilted to the left with steering servo on left as well, with Rx/rx batt on right side, and then twin packs on each side, should be 99% balanced then. Still thinkin on the ideas though.

[sikeston34m]

Originally Posted by zeropointbug

-IMO, I don't think that would matter would it? I mean if it's an inrunner of equal power is geared for the same speed, then the torque to the diffs would be the same, as all brushless motors have to the same torque curve (straight line)... and yah, it's too bad that any type of slipper can't be used with a setup like this.

I think there are some major differences between outrunners and inrunners in how they make power. The Gap between the two used to be large when I first got into discussions about this. Those were the days of the two pole inrunners.

The Gap has been closed somewhat with the rising popularity of 4 pole inrunners. (I LOVE 4 pole motors btw)

Ok, Let me explain my thoughts as best I can, this way.

What makes power in an electric motor? Any motor?

It is the repelling/attracting forces of the magnetism. Correct?

How much power we can make depends on the strength of the attracting or opposing magnetism. Correct?

So in the Engineering World for Motors, one would think the bigger/stronger the magnets AND the stronger the electromagnetic field is, then the more overall power is going to be produced.

Bigger is More!? Well yeah. But we only have so much space to work with, right?

This is where I feel the outrunner shines.

Measure the stator on an outrunner. I believe an inrunner would be required to have a rotor almost this big to make the same amount of torque simply because of the obvious leverage advantage.

Now, consider the total mass of the magnets spinning inside the outrunner's can. Think about how large an inrunner's rotor would have to be to contain the same magnet mass.

Then let's add up the poles. A 12 pole motor shaft shifts 30 degrees for every commutation from the ESC. This is where the lower kv comes in, BUT there's a torque multiplier at work here too.

How many degrees does the shaft shift on a 4 pole motor? To be honest, I would have to look it up, but it's alot more.

Long Story Short, the outrunner makes its power at a much lower rpm, but it's still all there. Condensed Power at a much lower rpm. This is what I was calling "Explosive".

Where as, the inrunner makes it's power through it's ramp up (spool up) time, and much higher rpm.

Another thought... I was just moving stuff around on the truck and was tilting the transmission 45 degrees one way and putting the motor centered in the chassis. Now if only I could make it work that way without heavily modifying the chassis to make room for it. If it could be done, then the motor would be centered, trans tilted to the left with steering servo on left as well, with Rx/rx batt on right side, and then twin packs on each side, should be 99% balanced then. Still thinkin on the ideas though.

I think what you're doing is great. Please share more and take some pictures.

[zeropointbug]

Well, I don't know what you think 'kind' of power an outrunner has, all I know is that an electric motor has watts, and the wattage is a product of speed vs. torque, and every motor has 100% torque at zero rpm and drops from 0rpm to max rpm. I really don't think there is anything different in an outrunner, except for motor inertia (although it's spinning alot slower, so that is near canceled out), it has many times more torque, but spins many times slower, so power ends up being the same as well.

Unless I didn't get the idea you were trying to convey? Explain in more detail?


On a side note, I posted some pics of roughly what I was thinking of when I said tilting the trans and making a mount for the motor in the center of the chassis, and lowering it. Check it out. Looks like a pretty balanced setup?

[zeropointbug]

The batteries would be mounted on CF angle mounts and will be sitting 1 inch lower than in the picture.

[sikeston34m]

Originally Posted by zeropointbug

Well, I don't know what you think 'kind' of power an outrunner has, all I know is that an electric motor has watts, and the wattage is a product of speed vs. torque, and every motor has 100% torque at zero rpm and drops from 0rpm to max rpm. I really don't think there is anything different in an outrunner, except for motor inertia (although it's spinning alot slower, so that is near canceled out), it has many times more torque, but spins many times slower, so power ends up being the same as well.

Unless I didn't get the idea you were trying to convey? Explain in more detail?


On a side note, I posted some pics of roughly what I was thinking of when I said tilting the trans and making a mount for the motor in the center of the chassis, and lowering it. Check it out. Looks like a pretty balanced setup?

yep, Watts is Watts but could there be something more? LOL

KV versus gearing versus final efficiency rating. I get that.

That's an interesting way to look at tranny position. I like that, but how are you going to secure it?

This should be good.

[zeropointbug]

Isn't there a website that is going to be doing dyno tests for popular motors in R/C? That would put this debate to rest I think, just to see a torque/power curve of some of these motors. Another thought, maybe it's the ESC firmware that is causing a different 'feel' or level of power between a in and outrunner type?

As for the mounting of the transmision, I was thinking about getting a small bracket made that screws into the aluminum plate on the trans and goes around and mounts like the regular plastic stand-offs. I would have to grind the plastic mounts away of course.

[sikeston34m]

Originally Posted by zeropointbug

Isn't there a website that is going to be doing dyno tests for popular motors in R/C? That would put this debate to rest I think, just to see a torque/power curve of some of these motors. Another thought, maybe it's the ESC firmware that is causing a different 'feel' or level of power between a in and outrunner type?

As for the mounting of the transmision, I was thinking about getting a small bracket made that screws into the aluminum plate on the trans and goes around and mounts like the regular plastic stand-offs. I would have to grind the plastic mounts away of course.

If there is a website like that, I'm not aware of it. I sure hope there is one in the future.

Watts is a measure of the power put into a motor. Volts X Amps

Actual work being done is HP and Torque values.

Efficiency is how well the incoming power is utilized. Watts changed into work versus watts burned off as heat energy.

I like to keep an open mind. Not everything that will be discovered has been discovered.

There is alot to be said about Motor winding also. Then there is the scale of measure for the strength of a magnet. With limiting factors being saturation and demagnetization temperature.

I've done alot of research. I get lost around the point where it gets in depth about eddy currents in the Magnetic Harmonics. I do know this also effects efficiency. Clashes or opposing forces that spend energy fighting each other instead of doing work.

Your setup will be almost dead on as far as being centered.

I really like the look.

[zeropointbug]

I thought I would update the progress I have made making my Revo more and more 'race worthy'... and where I have got it at now is nothing short of amazing, performance wise. Everyone at the track comments on how it doesn't 'look' like a Revo when racing, more like a truggy they say. I would have to agree, the weight distribution and center of gravity seems like it is just right for the chassis, and really seems to shine in the handling department, compared to a stock Revo 3.3.

The battery mounts are 1.5" CF angle from SierraComposites.com, the mounting brackets (alum.) are made from 1/2" x 1/8" 6061-T6 strips, a little small, but has held up fine so far after some pretty nasty crashes. The packs actually sit 1/4" lower than the E-revo battery compartments, and are a few mm above the bottom level of the servo guards.

The Rx pack mount is made from some CF I had laying around, which I cut, and glued with some CA glue, sticky Velcro all-around, including main power packs, which take the securing to the next level, really works well.

I was worried about the CF getting quite scratched and damaged from landings on rocks, and scrapping on stuff that commonly occurs at a track.

Enjoy.