Outrunner info??
 

I was downstairs looking at my unfinished Hyper 8 buggy (waiting for cash) and was wondering what my next project was going to be. I still keep drifting back to a custom dragster/musclecar idea. I thought maybe using a direct motor to rear diff drive system using an outrunner motor may be nice for this. I wouldn't be using a spur/pinion setup nor a transmission so the only reduction would be in the rear diff.

I went to a LHS today and checked out what they have for outrunners and discovered I know nothing about them. Well, I do know the rotor is on the outer can, that they typically run much lower kv, and they have huge amounts of torque. But, I don't know what the ideal max rpm is or really any way to compare them to a typical inrunner style, power-wise.

The guy at the LHS said the model numbers (of whatever brand they have) are what they would equate to if it was a Nitro motor. So, a 46 motor would be equivalent to a .46 size Nitro motor. That really didn't tell me a whole heck of a lot. I then asked him what the typical max current draw is and he said the 46 (~800kv) draws upwards of 60A at 11.1v in a plane. So, I asked him if that was constant draw or pulsed draw and he wasn't sure. Also, if 11.1v is the recommended voltage for that motor, then does that mean the max recommended rpm is <= 10k?

Huh????

Hi,
you can reach much more rpm also with outrunners:
I had a Cyclon brushless one capable of 5500 kv/volt and I ran it with lipo 2s.

Everything depends by the motor design. They probably shown you some motor
to run propellers directly to the shaft of the motor without reductions.

I think you should understand how many rpm you need looking for the car gearing.
If you suppose you need to reach 50 mph, you simply will find the right rpm
using your speed formula "inverted" (difficult to say in english for me, I hope this
stay understandable).

When you will have understood the right rpm, you will choose the right motor design.

BTW have a look to the Cyclon ones, I think they are really good motors.
www.cyclonbrushless.com

Ciao,
Daniele

From what I understand most outrunners have a relatively low rpm limit because of the amount of mass they are turning. Also, I think most outrunners are much higher pole counts. Like 10, 12 or more poles. This may also have something to do with the extra tourque.



Its actually funny that you say this. I just ordered (ordered on Monday)an ourunner I am planning on testing in a BL Cen Matrix project I am starting.

There is actually a company that makes outrunners specifically designed for car and truck applications.

www.cyclonbrushless.com

I have been wondering about these motors for quite a while but I havent found ANYONE that has tryed them yet. So, I decided that this would be a good place to test it. They are a little diferent than your typical outrunner. They are supposed to be good up to 40K rpm. I'll let you know what happens. Although its probably going to be while since I am lieterally just starting and this is going to be my ''winter'' project. I am going to use the Cyclon Car 2000 (2093kv) motor on 5s (if your gonna test it why not push it right to the limit :018: ) with the Quark 125 set to ''outrunner'' mode. Its the only car controller I have ever seen with a setting for outrunner mode.

My thought was I could go with a lighter motor and get just as much/more torque out of it cuz its an outrunner. We'll see I guess...

Captain: What do you mean by "huh"?

danverz: Thanks. I understand how to figure out the rpms using all the reductions, etc. I just don't know enough about outrunners to know what the "guidelines" are.

jhautz: Yeah, I also knew about the high pole counts and the rpm limit dues to the mass makes sense. Since the weight is so far out, it would also act as a flywheel of sorts as well. I wonder what kind of effect that would have. Those cyclone motors look nice. I guess I'll let you be the guinea pig - it's better on my wallet! :)

Gotta be careful with the Quark programming though:
So I guess it depends on the poles and/or kv value...

I like the fact that these motors are physically shorter and the lower kv allows me to eliminate the tranny/spur/pinion, which do have some losses. Not to mention it would eliminate any possible weak spots in those areas.

A direct drive like you are thinking would be pretty cool. You would only need around 3500 RPM to get 60 MPH on a max size wheel. A 240kv ourtunner on 4s would get you over 60 mph. The question is.... Can you really get that much torque out of one motor. :002:

What about getting 2 of them and setting it up on a pair of tank tracks and just use motor speed to steer as well as drive.:p

I seen a crawler with an out runner in it. It was a little bitty motor.
It had more torque than the 55t lathe motor according to the builder.
An out runner has more torque for it has a larger type rotor.
It has a 28 mm can. It is like running a 28 mm rotor. He was only
running like a 22 something.

HAH! Awesome BrianG!!! I was going to do the same thing with my emaxx truggy conversion, before i went with a 7XL setup instead.

Here are a few of my notes:

THere are few motors that suit car applications (outrunners), HOWEVER, one of the few that i found that would work very well is the newly released E-Flite Power-46 outrunner motor. It's an 800-watt motor, here are specs:

-Up to 800 watts of power (continuous, maybe, for airplanes, constant load...)
-670 kv (RPM/V)
-0.04 Ohm Resistance
-voltage range: 14.4-19.2 (4-5 LiPo's)
-continuous current 40 Amp, max current 55 Amp
-6mm shaft, so you can machine it to take a CV shaft (also reversible)
-290 g weight
-Diameter: 50mm, Length: 55mm

http://www.greathobbies.com/products...d_id=EFLM4046A

This motor on 4s LiPi pack should take a typical 1/8 buggy to 45mph direct drive. Or 55mph on 5s LiPo pack.

This was the setup i was planning to run, however i did not know enough to actually take out my wallet. I have no idea how hot the motor will run, and also you have zero flexibility as far as gearing (fundamentally). If you want to try that would be cool though ;) Also, on one side of the motor you have to mount it with 4 screws, and the other side will ride on a bearing, you can also take the shaft out and make a longer one to make it work with 4wd setup.

The E-Flite Power-46 motor is $130.

This setup would be VERY quiet. Almost inaudible, besides the tire noise.

Well, the one I was actually looking at (just to see it, not to buy) was this one. One neat feature is the reversible shaft so I can decide which way I want to mount it. It certainly looked beefy enough, but again, I just don't know enough about them.

I want to set it up like a real RWD car; motor centered up front, driveshaft to the rear diff. Probably using a custom ladder frame design with 2s2p on each side (to keep CG low) for a total of 4s2p. Maybe use two A123 M1 3s2p packs instead. This type of design would also leave me PLENTY of room to lay out all the electronics on top for optimal cooling. Then, get something like a 1/8-1/10 scale old-style dodge charger body with proline on-road street tires or slicks mounted on mag-style rims. I was thinking of using Revo shocks since they are short and offer quite a range of spring rates. I'll probably make a wheelie bar similar to those seen on real dragsters. I definitely want at least 60mph. Something to turn heads. I'm thinking of incorporating the ability to add weight (steel blocks or similar) in the rear to keep wheel spin to a minimum.

A lot of this is on scratch paper right now, but keeps getting pushed aside because I didn't want to deal with a way to reduce ~35-40krpm down enough to use direct drive. For a while, I was looking at using a planetary inline gearbox like this or this, but really don't want to deal with ANY kind of transmission. It's just one more thing to go wrong, and they aren't cheap!

One of my LHS places has a bunch of flight guys, maybe one of them knows more about the out-runners. Actually, it would be nice to talk to someone who has used BOTH inrunners and outrunners and knows how they compare.

[QUOTE=BrianG]Captain: What do you mean by "huh"?


Nothing.
I'm quite very simple when it comes to these sort of topics. You talk alot of science:032: and I'm frankly not that type of guy who would dig deep into things like that. I really dont understand many of the terminologies used in this hobby and specifically what regards brushless and all.

Haha! I was only joking when I said "huh?", though.:p

Do not take me wrong.:)

Lol, that's OK. It's just that the statement was a little open-ended and was wondering specifically what the confusion was about. :)

The E-Flite has a 6mm shaft that is reversible BrianG, so you can take it out and put in a longer one for 4wd if you ever wanted to. Or to simply flip the motor around...

Interesting timing on this thread. I just bought and installed yesterday aDualsky MX2839CA-12 outrunner motor in my crawler. I did a little reading on this forum and decided to give it a try. I'm running a Mamba 25 ESC with a 2s 2100 lipo. I haven't had it out of the garage yet but it does seem to have at least the same, if not more, torque than the stock Tamiya TXT motor it replaced. It's pretty amazing. I had doubts that the motor would even move the 8 lb truck let alone crawl. The motor weighs only 55 grams but is very capable. I don't know how much of that info on the Crawler forum will be useful to your application Brian. Keep us all posted with your project.

Thanks for the info. I really want to finish my buggy project first before I start on the muscle car thing. It'll probably be about 6 months before I start on it.

Thanks again all!

This is interesting Brian. I was thinking the same, the reaso why they have tons of torque is obvious. so is their low KV, My only concern is due to their magnets being relative far from the centre, it won't be as easy to spin up quick and spool down fast. That's a good reason to keep it low kv. (less KV means it takes less energy to spin up)

Their weight is relative low. Which is a good thing too.

I thought about putting an output cup directly onto the motorshaft and use two, turning in opposite directions. One for the left, and one for the right wheel..

With the right electronics, and 4 of these babies, you can make your own stabilizing system for corners..

Serum, last year i was going to do a true AWD setup with 4 Hacker outrunner motors. They are 550watt each so 2200 watt peak, this would be so kickass, this would prob be the best way to break the world speed record, no tranny, no diff's...

Eventually, i would like to make the motors right in the wheels, however you would have to make them light enough so not to make too much UN-SPRUNG mass, which would affect suspension abilities a lot.

I dont think it's the way to brake the world record. It takes 1 motor to do. 1 motor is lighter and will run more efficient.

Yes, one 'bigger' motor is usually more efficient. Howver, because the outrunner would be running RIGHT at the wheels, there would be no transmission in between, you know you lose a lot of power through a transmission. THe outrunner's would end up running more efficiently.

No, that's plain rubbish.

the drivetrain doesn't take that much energy. wind resistance will be affecting it more.

Why do you think it is that the speedrecords are set with 1 motor?

wind resistance IS the main thing it would be fighting against.... fundamentally.

if there was no wind resistance, any car could go 200mph, so long as the tires can could do it, not likely. Tire resistance also affects it too, not as much. But the heavier the car, the more resistance is put on the tire...

Besause that is the conventional setup currently used in almost all RC applications.

Don't rule out outside the box thinking just because ''most'' peple arent doing it that way now.

Creative thinking is the way technology gets advanced.


That said....
I do agree w/you that the energy lost in the drivetrain is negligable.
The bigiest problem I see w/ a 4 motor system is getting them all synced perfectly enough to keep a system stable at 100+ MPH. Getting 2 synced perfectly would be hard, 4 seems darn near impossible.

A 4 motor system seems to me like it could be one hell of a crawler setup though!

Seperate motors on each wheel would take a different type of controller, or at least some type of signal adaptor. Since each wheel would have to spin at different rates when steering (which is normally taken care of with a diff) the controller would have to adjust the pulsewidth of the signal to the slower wheel based on the steering adjustment. So basically, if you are going straight, both motors get the same power. When turning left, the left wheel has to spin slower, so the controller would have to somehow factor the steering signal into the throttle signal to know that the left wheel is to spin slower. I guess basically how a tank controller operates.

So, the easiest way to do this would be to use a controller with two throttles and use that for steering and throttle control. Not very intuitive compared to a typical pistol-grip controller.

The other way to do this would be to feed the throttle and steering signals from the Rx into another "box". This box would then have two throttle outputs. The signal on these would be a processed signal based on the input throttle and steering.

I've done some thinking on this already. A typical output singal of a receiver is a series of square wave pulses at a frequency of 50-60Hz. The actual frequency really doesn't matter as long as it is consistent and not too far from these values. The positive part, or "on" portion, of the square wave pulses range from 1ms at min throttle/full left turn to 2ms at max throttle/max right turn. Steering center/neutral throttle is 1.5ms. So, a circuit would have to be designed to create two 50Hz squarewaves for each throttle signal whose pulsewidth is equal to the single input throttle pulse except when the steering is engaged. If turning left, the left throttle channel signal would be reduced in proportion to the steering pulsewidth. The same for the right side. I think this can be done relatively simply with some cheap linear analog circuits (op-amps, transistors, etc).

Maybe if I have time this weekend, I'll try to breadboard a couple of ideas. Might be a neat thing to market...

Well jhautz, i thought you knew me better than a person that rules out the outside of the box thinking..

I was making a statement towards this sentence;

'you know you lose a lot of power through a transmission. THe outrunner's would end up running more efficiently.'

Which is plain rubish..

agreed

Glad we got this straight.. :005:

ME TOO !!!! :027:

I also don't think ANY car could go 200 without wind. Motors themselves have limitations. RPM's and such. It would only be able to wind so much, not infinately. Maybe the design of any car with the right application could do it yes, but not just any car.

that may be a bit technical! LOL

Actually, almost any car could go 200mph without wind resistance. The difference between different power systems would be how quickly they would get to 200mph.
Without wind, there would still be the friction between the tires and the ground. This is pretty much the only thing that would limit a vehicle from going 200mph when there is no wind resistance, but its effects could be reduced by using lower-friction tires.

Here's my reasoning:
Kinetic Energy (KE) = 1/2 x mass (m) x velocity^2 (v^2)
One way to express the unit for power is: Joules (energy) / time
The power of a system would be the determining factor for how fast the car would get to 200mph. Theoretically any car could go 200mph without friction.