The Outrunner Tutorial Thread

[microgoat]

The old Outrunner thread is only 21 pages, so I'll try to condense what we've learned in the last year into a few short posts so folks who want to try brushless can get started without spending a whole evening reading the old thread.

Why Do I Want An Outrunner? Outrunners have several advantages over conventional brushed motors: Weight (two ounces vs six) torque (virtually unstoppable with good batteries) efficiency (up to 75%) and lack of maintenance due to not having brushes. They also spin much slower than brushed motors. Depending on the wind, an outrunner can turn at half the speed of a 55t lathe motor at full speed, while developing the same torque or more.

What is KV? KV is RPM per volt. A 1000 KV motor will spin at 1000 rpm given a 1 volt input. The relationship is linear, and due to the huge torque generated, outrunners barely slow down under load, so the speed is perfectly predictable. Multiply the KV by the number of cells, multiply again by 1.2 volts per cell, and you have your motor's RPM.

Why are there 3 wires? Brushless motors are AC. You'll need a brushless speed control to run an outrunner. The Castle Creations Mamba-25 has so far proven to be the best all-around choice for crawling, despite its small BEC output. Use an auxiliary BEC, or a 5th-cell battery tap to get around this limitation. Choose your motor with care, as exceeding the ESC's limit can burn it up (although the Mamba has proven itself to be quite robust, powering motors that it theoretically shouldn't be able to handle. It's pretty burly for a little shrink-wrapped circuit board.) The Quark ESC's look promising as well.

One Motor per ESC: Clods will need two ESC's. The ESC is always "reading" the motor's position, so you can only use one motor per ESC.

Gearing: In a 2.2 rig, it's largely unimportant. Gear it how you like it; the motor will deal with it. I've tried everything from 12/87 to 18/54 on the same motor/truck comination, and the motor doesn't seem to care.

Technique: Outrunners don't like to be "gunned" from a standing start. Ease into the throttle to let it build speed gradually. Once the motor is going, then you can romp on it.

Motor selection: There is a mind-boggling selection of outrunners available. What you should look for is a max amp draw compatible with your ESC, a 1/8 inch shaft, and a KV in the 700-1000 range. Motors we know work well include the Axi 2212/26, E-Flite Park 400, and of course the Holmes Hobbies Revolver, which JRH has selected especially for crawling duty. The Revolver has another advantage in that it is already tapped for a standard mounting pattern, which eliminates the need for a custom mounting plate.
If your outrunner's shaft comes out the wrong side, don't worry. Most of them are reversible with a little work.

OMG! It turns the wrong way! WTF! Relax. Just swap any two wires going to the motor to change the rotation. Doesn't matter which two.

Batteries: Get some good ones. Brushless motors take a lot of juice on startup, so cheap cells are not your friends here. I like the IB1400 and GP1100 2/3A cells, and get almost 45 minutes with my Axi-powered rig. Lipos are also being used with good results, but they need protection. If you use a sub-C pack, get some sunscreen. You're gonna be out there all day.

ESC SETTINGS: (Save to file, and send to your speedo with the Castle Link)

Originally Posted by johnrobholmes

http://www.holmeshobbies.com/Common%...%20crawler.dat

http://www.holmeshobbies.com/Common%...%20crawler.dat

First one is my mamba 25 settings. Second one is mamba maxx settings. I Like 100% drag brake. Some people prefer more downhill coasting.

If I've missed anything, post up.

Welcome to the Revolution!

[JohnRobHolmes]

Awesome summary! A couple of points I would like to skim over again.

A 55 turn lathe motor spins around 1000 rpms's per volt too, so most outrunners are very close to the same speed. The difference would be the gearing adjustability, since it seems that overgearing an outrunner is really easy to do depending on size!

I will also add that good batteries ARE key. Without a good cell to give the motor punch, cogging and crappy power occur.

The mamba is very stout for a how little it is. So far I haven't found a rig that it wont power. Being careful with the voltage used watching the heat are advised with 10+ pound rigs.

[WRXronald]

perhaps you forgot this point...

BEEF up your driveline, and leave 1 piece in the driveline as a weak link... make sure that one piece is 'easily' accessible and cheap for swap-outs....

BECAUSE your JRB Revolver will not hesitate to shread spur gears, shread ring gears, and snap steel drive shafts at will... or round out plastic tmaxx hex drives as well.

where the 55lathe may stall, the JRB Revolver will just keep turning if you foolishly tell it to... and that means your driveline will pay.

not to worry too much, most of you know 'when is when' when wheels are completely locked and whatnot...

course i do power mine on capable 11.1volt lipos... so i suppose that generates a good bit more powerful Revolver than say 7.2volt NiMh... but still, this motor is WICKED powerful. and i love every bit of it, except the broken dogbone part

[JohnRobHolmes]

I rounded out a hex yesterday since I have no slipper. The cross pin jumped out of the slot. My tires arent glued either, but one tire got wedged under an overhang.

The only rig I dont worry about power with is the twin force crawler. The shortened maxx sliders shear before anything else gives. Aluminum idlers and bearings in the pede tranny are a must.

[JasonInAugusta]

My SW2 (with HH Revolver) is doing much better than it did at Buford Dam when it comes to breakage. The Jato shafts are holding up, I'm assuming that the ring and pinon will now be the weak link. Not exactly the easiest parts to replace, bit it's not that hard either.

I've ran the brushless NN around the house a bit, it's a damn powerful rig. Hopefully I'll have time to get a few more packs through it later this week. The way it's currently set up (seperate channels on the DX6 for throttle - no "Y" harness) I'm looking at dialing in a bit of expo on the two throttle channels to hopefully soften the "spool up" of the Mamba controller and make digs easier to manage. Once on the throttle it picks up RPM quick. Bottom end response isn't quite as smooth as some brushed ESCs I've used, and from what I saw when JRH was in town running his Quark, the Quark has superior slow speed response.

When it comes to bottom end throttle response, think of the Quark as a Super Rooster. The Mamba is more like an EVX. Bottom end isn't as good, but it's not designed to operate at low RPM. Just as with the EVX, the Mamba was designed to be used in speed applications. I think it'll work just fine with a little tinkering.

[JohnRobHolmes]

From what Bernie at Castle told me, the minimum speed of the motor might be tweakable with a combination of programming. The soft start would be an interesting feature to try- the motor will still start, it just doesnt jump to life. I would still rather use a mamba for a Comp setting because of the reliability of startup direction. Sometimes the Quark grunts a mistake (maybe once or twice a pack), and then corrects itself. We shall see which I use at the next comp I guess. Life was easier before there were choices.

[JasonInAugusta]

No doubt! I did like the silent operation of the Quark, though.

When I have more time (under deadline crunch this weekend) I'll mess with the Clod some more. You're right, I think I have the drag brake and startup set to 100%!

[microgoat]

JIA, did you try adjusting the throttle curve using the Castle Link? One hell of a handy tool. Once you find one you like, you can save the profile and load it onto the other Mamba so they both have the same curve.

[Espeefan]

Something I'm a little confused on here - if brushless outrunner motor cans spin, how do you mount the motors up to a tranny or gearbox? Do the motor shafts still turn and the pinions still mount up the same? I'm a bit confused with this brushless outrunner stuff.

[JohnRobHolmes]

The face plate is stationary where it mounts. In the faceplate sits a bearing that the shaft pokes through- just like a normal motor. The shaft extends all the way through the motor to the rear end that attaches to the can (that spins). The spinning can causes the spinning shaft.

The spinning can limits gear choices to to degree, as the motor cannot touch anything. Otherwise, its just a motor.

[Espeefan]

Ahh, that answers my question! Thank you John. I appreciate it.

[JohnRobHolmes]

No problem. Any time.



Brushless related- sheared teeth off my diff today using a double-stack (mp jet 2820-7). I shouldnt have pushed the throttle so much with the tires bound.

[dezfan]

Want to see some power? Zzzzrrrrrrrrrrrrrp! Oops!

[microgoat]

Yep, it's a real beeyotch having too much power, isn't it?

[JasonInAugusta]

I destroyed a set of Clod gears yesterday.

[JohnRobHolmes]

I told ya the gears would break! Which ones gave out?

[JasonInAugusta]

Middle counter gear is munched, trac gear has seen better days.

There's actually a 5mm E clip folded/embedded in the middle counter gear. Apparently it popped off at some point during the trashing.

[Rockpiledriver]

Wow, that's power.

Was it completely bound when they gave out?

[dezfan]

I've said it several times, the slipper on my 2.2 has once again come into play. The Revolver is just impressivly powerful!

W/o the slipper, I could see many parts having to have been replaced on my 2.2 already!

[JohnRobHolmes]

I broke the diff the other day because the slipper was too tight. Traxxas pegs not good enough.