First Crawler; SCX10 with 400 outrunner?

[aramid]

I've been toying with this idea for a week or so now, and the crawling sections on the other RC boards I frequent are pretty dead. It looks like you have a lively forum here, so hopefully someone can give me some guidance.

I've been running electric RC for quite a while now, mostly airplanes and a bit of high-speed surface stuff (Traxxas Rustler). I've gotten bored with my Rustler and decided to sell it and get a crawler. I pretty quickly settled on building an SXC10 kit, but where I run into trouble is deciding what exactly I want to power it with. I'm not doing competition crawling, and I live in Iowa so it's mostly going to be rough trails and the like.

I've got a spare Castle Sidewinder, so I can run pretty much any motor with all the drag brake and direct reverse options you might want. I'm aiming to run on 3s 2200 mAh LiPo packs, because I've got a bunch from my planes. I'll use a brushed motor if that's what it takes, but I'm much more inclined to run a brushless; I know it'll last longer on that voltage, and keep the weight down. I've noticed outrunners were popular in crawling a few years ago, but seem to have been a passing fad, as everyone is back to brushes again. I'm not looking for competition performance, and I'm well aware of the limitations in a brushless setup.

So, after all that rambling, here's my real question. Will a 400-class outrunner (Chinese motor very similar to an E-Flite Park 400) work reasonably well in a lighter-than-average SCX10? I'd like to see a top speed close to a brisk walk.

The excellent "Which Outrunner" thread suggests that this motor would be appropriate for a TLT or half a Clod. Problem is, I'm new to crawling and don't have any idea how an SCX10 compares to a TLT.

If it's not a good idea, what should I look at for brushed motors to meet my speed goal on 3s packs? It'd probably be an inexpensive 540 can motor, but which wind? Seems a lot of trail rigs use a 27 to 35 turn, but with my extra voltage would I be better off dropping to a 55-turn, or staying with the ~35 and just running extra low gearing?

Thanks!

[WIDELOAD]

If it'll work in a TLT it'll work in a SCX10 fine.

Just keep an eye on the temps and gear accordingly and you'll be sweet.

[aramid]

Thanks for the response. I'm still debating with myself whether or not to do this, and I'm looking into a theory I have regarding throttle smoothness. I'm thinking if I use a motor with the same magnet/stator configuration but wound for a much higher Kv than typical, once I gear to the same wheelspeed I'll have better resolution and low-end smoothness. Essentially, my lower gearing will give me more ESC phase switches per wheel rotation, so any jerking and cogging should only be half as severe compared to the more obvious 700-1000 Kv choices.

If I do decide to go brushed, how many turns should I be looking at for a 3s battery?

Thanks!

[WIDELOAD]

No worries mate..its all experimentation when it come down to it.

But as JRH said, 'Volt Up, Gear Down' is the best way to treat sensorless brushless.
So go for 700-1500kv, shove big volts at it and gear it down as low as you can go.
It smooths out 99% of the cogging due to the low gearing, but it will still boogie with the volts behind it.

As for brushed.

If its going in a SCX10, stick with 35-45t on 3s...

I've found with my screwing around that Brushed motors aren't as sensitive to gearing change as what sensorless brushless it.
So you can gear up or down to get your speed, again just gear to temp.

[aramid]

Originally Posted by WIDELOAD

But as JRH said, 'Volt Up, Gear Down' is the best way to treat sensorless brushless.
So go for 700-1500kv, shove big volts at it and gear it down as low as you can go.
It smooths out 99% of the cogging due to the low gearing, but it will still boogie with the volts behind it.

That's essentially what I'm going for, but I'm trying to work past the voltage limits on my ESC. My gut feeling is that I'll get exactly the same results whether I volt up or simply use a motor wound for more speed, provided it's still got the same number of magnet poles.

For the $15 or so a cheap outrunner will cost to test my theory, I'm probably going to give it a shot. I really want to use a Scorpion SII-2212-1850, but that becomes an expensive experiment, so I'm left trying to figure out which of the Chinese motors comes closest, and teeth/poles are one of the specs those companies don't bother to publish.

[aramid]

Well, it's done. Unfortunately, it's not working quite like I'd hoped. I'm running this motor on a Castle Creations Sidewinder on 3s LiPo. Gearing is 93/12.

The motor starts the correct direction every time, and I can creep along pretty much as slow as I like. However, when the controller switches from the startup sequence to normal operation, there's a surge of power, causing the truck to jump forward. Before and after the surge, I've got all the control I could hope for, but nothing I've tried has been able to remove the lurch itself.

It's something with the controller, because I've tried a handful of other outrunners of different size and Kv, and they all show the same behavior. The ESC firmware is up to date and I've tried several combinations of voltage, timing, and start power. I don't remember seeing a jump like this on my stadium truck with an inrunner, but I also never paid too much attention to its low-speed finesse.

Here's what I'm talking about:
http://www.youtube.com/watch?v=Q8z9BEH4BY8

Ideas?

[JohnRobHolmes]

Have you tried different firmwares? That is one helluva jump!

[aramid]

Before I start picking random firmware versions to test, I've sent an email to Castle support to see if they can suggest a particular version.

[aramid]

Castle finally got back to me late last week. Their very helpful response was "Our car ESC were not designed to run outrunner motors. Try different versions of firmware and use the one that works best for you." So, basically, good luck.

Because I don't really feel like tinkering with it right now, I've gone to a Holmes TorqueMaster Sport 35-turn. It seems very happy with my lipos at stock gearing, and power draw is very similar to the outrunner - lower in most situations, in fact, if I'm remembering my measurements correctly. Maximum power is technically reduced, but I'm not exactly stalling it out anyway.

We'll see how long I can put up with brushed motor maintenance. I'll revisit this topic if I change my mind.

[new2this]

I run brushed 35t integy and I am very happy, although I am running 2s lipo.....getting a Tekin FXR in a few weeks.