microgoat
I wanna be Dave
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)
If I've missed anything, post up.
Welcome to the Revolution!
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)
johnrobholmes said:
If I've missed anything, post up.
Welcome to the Revolution!
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