when sik said "A super low kv inrunner would make ALOT more torque" I thought he mean than an equivalent size/kv outrunner. Now I think I may have misinterpreted his response.

At any rate, it was Mike's narrow window of efficiency thing that got me. I want my cars to be efficient in as wide a band as possible. I think even when crawling you vary the motor speed coniderabley.

So where is the trade off? a 4 pole inrunner and 12 pole outrunner, of similar size and Kv. The inrunner I guess makes more power and can rev harder without anything going wrong. The inrunner is efficient over a much wider rpm range than the outrunner. The inrunner can run on a much higher voltage than the outrunner because its max rpm is a lot higher. The outrunner has more torque.

How much more torque? Te inrunner would have like a million winds to get into the 500kv zone so would have heaps more torque at the rotor than any inrunner we're used to. Furthermore, since the inrunner revs so much harder, gear the inrunner down to get the same rpm as the outrunner, you further multiple the torque.

Has anyone got any torque or power curves comparing similar sized motors?

The only application I can find them useful is in airplanes...when rpm is nearly constant, and everything has to be lightweight, so best do without the gearbox (ie low kv is an advantage).

Don't get me wrong, I don't want to argue for the sake of it, I am genuinely interested. But noone has really given anything more than their opinion on why they might of advantage in a car. A few claims that weren't backed up.

Also, I'm not knocking castle either, since I'm certain these outrunners are for their air guys (us car people aren't the only ones obsessed with castle gear you know :P)

you're still greatly biased. Look at some watt figures. Outrunners will be very similar to inrunners. Compare an Axi or Scorpion outrunner to a Medusa or Neu motor of the same size. Remember the Neu 15xx series are 39mm in diameter...

Torque output and ability can be directly related to the rotating portion of the motor, and its diameter. Outrunners cannot rev as high due to their design. However they produce more torque at lower rpm, due to the diameter and pole count.

It all depends what you want. If you need something slow revving with alot of torque then an outrunner is great. If you need a large rpm window, then get an inrunner.

I use quite a few outrunners, but still with transmissions. I have also done a few direct to diff conversions where the outrunner replaces the primary gearing. Those pose problems as well, such as high startup loads, and they generally do not spool up as fast as an inrunner (mainly due to the lack of gear reduction).

For most the normal setup of an inrunner and primary gearing will suit them better. For those of us that like to use outrunners, well, we will continue using them...

I'm not bias, I want to be convinced otherwise.

AXi 4130/16 Gold:
Can Diameter: 2" (49.8mm)
Length: 2.6" (65.5mm)
Max 8s Lipo = ~30V (Rounding up)
Max Current: 60A/60s

So thats nearly 1800W surge.

Neu 1512 series lists max surge power for all of them at 2000W
They have length 2.4" and diameter 1.53"

Significantly smaller, yet higher surge power.

Even at the AXi's max efficiency constant current (listed as 40A) thats a hair under 1200W, and the 1512's are 1000W constant, and theyre much smaller.

Go to a similar sized Neu, like a 1915: 1.96" diameter, 2.25" long. Still smaller. Constant 1800W, peak 3600W, heaps more grunt, still smaller, and lighter too (14oz vs 14.4oz).

I understand that, and I'm not trying to start an inrunner vs. outrunner war, I just want to know how theyre better in a car. Can you definitively say that an outrunner vs. an inrunner of similar quality and size, geared to the same output shaft speed will give you more torque at the wheels at the same rpm?

Look after all is said and done, I think outrunners are cool and I want to play with them and experiment, but I just want to know if they actually excel vs. inrunners in any land vehicle applications.

I think the only way that could be true is if the answer to my above question is a definitive "yes".

I guess I don't understand why we need to convince you? Me personally, I have no real data to share. It's likely others here don't either, they just have their experiences. Just keep in mind outrunners in cars are still relatively uncharted which means little quantifiable information.

From my experience, the answer is presently NO. That could change if the Castle outrunners are as good as Patrick seemed to indicate they are.

All good info, but you have not considered torque. Torque is what gets stuff moving quickly and more torque can change speeds faster. The 1512 will not make as much torque as the axi. The axi has twice the pole count of the new. Now the 1915 has a higher pole count, so it should make quite a bit of torque.

Also, look at the prices... The 1512 is more expensive than the axi, as it the 1915 (by quite alot). And they are for different applications. Axi makes a great outrunner, and castle will have to step up to excede axi's standards.

We can all agree that neu motors are some of the best in the world, so they should perform well. If I was making anything to race i would go with an inrunner, for both construction and performance. If i was making a crawler I would go with an outrunner. As for a dual purpose vehicle, it all depends on the speed desired...

I have a 6x6 maxx based truck, and I run an axi 2826/10 in it. It is geared for about 20mph in 2nd and 8-10 in 1st. It has tonns of torque and can crawl with the best of them. It will also jump and has plenty of speed for bashing, plus it has exceptional throttle control (due to the multipole design and the great firmware on the MM).

As I said, it all depends. HP (watts) is not the be all and end all of rc. Just read a car mag and you will see that the shootouts are not always won by the big number car...

You don't need to :) I guess I'm just asking to be. I just think it's a cool idea and worth exploring, but don't have the $$ to do it myself at the moment :p. So yeah, basically experiences would be good, but most people who have run outrunners have built the car for the outrunner, or changed the car significantly to run the outrunner.

Like has anyone gone from an car running an inrunner, then bolted an outrunner in its place, geared it up to a similar speed, and compared performance?

That's why I keep asking about torque :) That's why I keep talking about gearing down to the same shaft speed. Power and torque are directly related via rpm.

Sikeston 34m has done this with his emaxx. went from a 2826 axi with 22/40 (something like that) gearing to a medusa...

I will say that 99% of people will find an inrunner preferable over an out runner in a land vehicle.

Sweet. Is there a thread or post about the experience? I'm not having luck finding it, I found the outrunner e-maxx thread, didn't mention any medusas though.

P.S. Sorry eveyone who was subscribed to this to read about castle outrunner information. I didn't mean to perform such a significant hijack.

At 5250 rpm in a gas engine they are the same (if memory serves me correctly).

As far as taking 1 of each design that produce similar output (watts) numbers and setting them up in matching vehicles that are setup to go the same top speed... You will find the outrunner has more torque off the line due to its design. It should also startup smoother due to the multi pole design. The inrunner may spool up faster, and will feel more responsive once it is spinning. That responsiveness is more desireable in a land vehicle due to its reasonably large speed window. Plus the sealed can and lack of spinning parts also makes it better for the application.

Also, the fact that the outrunner can produce the same horsepower while spinning slower should indicate its performance ability...

Look at a big block gas engine versus a turbo 4-banger. Both can push out 600+ hp, but the big block will do so turning slower and will produce more torque. If you want to do 200mph the slow revving big block may not be the best choice due to weight and gearing options, but neither would putting the turbo motor in a tow truck... And just because the big block can make 700ft/lbs of torque does not mean the turbo motor can...

The application argument is the most important one from my perspective.
For example, right now I am building from the ground up an outrunner-powered belt-driven truggy with no gear reduction aside from the main pulleys. The kv on the outrunner is 360, and it will be powered by a 6s Lipo.
An outrunner would spin much too fast for this design, and would require at least a pinion/spur. One of my objectives with this project is to make it as quiet as possible, not for any real reason, just because I can.

I thought for any rotation that power is directly proportional (not equal to) to torque * frequency? Then figured that a motor of any kind will put out a certain torque at a certain rpm, and you look at the torque and rpm to figure out the power output and said rpm.

4-banger? I take it you mean 4cyl not a 4-stroke (as two stroke obsessed dirt bike riders use 4 banger to refer to the engine of superior design). Interesting comparison with the truck, most of the medium rigid trucks run 4cyl turbo diesel motors but I get what you're saying. Low rpm diesel motors vs high rpm jap sports car motor. Still, I think the choice in 1:1 cars is more of a cost thing. A little 4cyl turbo sports motor would go fine in a tow truck geared right down, but they would be stupidly expensive and unreliable compared to a big ol' clunkin V8 whose design hasn't changed for the past 30 years.