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Old Mar 06, 2014, 04:16 PM
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Question
Astro 05 FAI Racing Motor - brushed

I have gotten an older Astro 05 FAI Racing Motor with gearbox (about 3:1) and 80 amp brushed ESC. I have run it on 3S with a wood 9 X 6 and taken it up to 375 watts. It definitely needs some cooling, but I expect it could put out more power under the right conditions.

I'd like to put this in an old-timer to fly just for fun. While I have done a lot of brushless stuff, this is my first time in dealing with a brushed motor of this size.

I don't know if these have a KV rating or how you pick a prop and determine the operating conditions, other than watching the current and case temperature to keep from smoking it.

Any data or ideas would be welcome.
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Old Mar 06, 2014, 04:28 PM
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See if you can pick your one out here: http://brantuas.com/ezcalc/dma1.asp They came in 5T, 6T, 7T flavors.

I saw this: The 05's will do about 350-400W allegedly. Cobalt takes the heat well.
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Old Mar 06, 2014, 06:36 PM
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Here ya go, straight from Astro Bob.

Larry
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Old Mar 06, 2014, 07:11 PM
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Not saying I know anything about these motors , but whoa, that is a hellishly high Io isn't it? I'm also surprised by the efficiency curve.. if you look at efficiency curves in DriveCalc most motors peak at perhaps 20% of max amps... this one is >50%.
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Old Mar 06, 2014, 08:54 PM
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Thanks guys, this info helps. I don't have it mounted - or even a mount, have to make one - so I held this thing in one hand and ran it to 375 watts. While it does get hot, some air flow will help.

This motor/gearbox has been extensively worked on, with most of the case cut away for cooling. I'll post a picture soon.
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Old Mar 07, 2014, 03:44 AM
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9x6 on 3S at 375W suggests it is the 5T (Kv=3214) with the 2.38:1 Superbox, giving an effective Kv of 1350.

For an old timer, you should be able to run 2S at up around 45-50A with a 12" prop. A 2S 4500 is only the same weight as a 3S 3000 and will easily handle 50A. Check this chart: http://loke.as.arizona.edu/~ckulesa/propulsion.html

Thgis might be of interest: http://www.wattflyer.com/forums/showthread.php?t=2303
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Old Mar 07, 2014, 06:15 AM
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More good info, thanks. Here are some pictures. The case has been cut away - a lot - perhaps for some reduction in weight, but mainly for cooling. I'll check the gear ratio to see what I have.
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Last edited by Louierc; Mar 07, 2014 at 06:53 AM. Reason: add pix
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Old Mar 07, 2014, 06:55 AM
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How do I mount this motor ? I am thinking of a bracket with a hole for the main bearing and use the two gearbox screws to secure it -
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Old Mar 07, 2014, 08:34 AM
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Do not use the gearbox to secure the motor.

Here are three common methods that we used.
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Old Mar 07, 2014, 09:39 AM
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The largest reaction torque is present at the output shaft, and it seems to me that if not anchored at the front housing, but at the motor can, this could result in twisting the gear box and its mounting bolts to the motor. Not to mention any vibration from the prop can be adsorbed up front at the main bearing and mount rather than being sent to the motor, plus the moment arm is longer when not mounted at the front bearing.
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Old Mar 07, 2014, 02:16 PM
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Don't know if the diameter is the same, but Maxx Products has clam-shell mounts for Cobalt 05 motor: http://www.maxxprod.com/mpi/mpi-29b.html

http://www.espritmodel.com/clamshell-mountheatsink.aspx
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Old Mar 07, 2014, 02:23 PM
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Yep, that could work. The heatsink finned version would be OK too.

I'm still hung up on the torque issues when mounting by the motor case instead of the gearbox. Plus my motor case is cut away a lot on both ends for airflow.
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Old Mar 07, 2014, 02:45 PM
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Avoid slamming the throttle quickly full on or full off can help. I used the method in Ken's middle picture to mount an Astro 40 cobalt geared motor on 18 round cells, as well as a least a couple other pretty powerful motors. I placed a piece of rubber sheet on the bed the motor rested on and pieces of rubber band under the U shaped hold downs (made from sullivan yelow pushrod inners) to help prevent the motor from rotating from the torque. It worked fine.
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Old Mar 07, 2014, 02:49 PM
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I never used the mount shown at the far left. I most often used the one on the far right where I made a motor tube out of 1/32" plywood and ran it through a couple of formers and the brush holders were captured in the plywood tube. I also used the Nyrod example from Bob Kopski, the one in the middle, on some planes as well. Sandpaper goes on the bottom of that mount to keep the motor from rotating. The Nyrod holds quite well.

Do not put anything between the motor and gearbox. No matter what you do it will misalign the gearbox.

The gear lash is set with a small strip of regular computer paper wound through the gears and the box tightened to the motor.
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Old Mar 07, 2014, 03:18 PM
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Quote:
Originally Posted by Louierc View Post
Yep, that could work. The heatsink finned version would be OK too.

I'm still hung up on the torque issues when mounting by the motor case instead of the gearbox. Plus my motor case is cut away a lot on both ends for airflow.
Mounting by the motor case, albeit the rear of the motor case is almost standard for outrunners.

You're only talking about 1 inch ounce of torque per amp, so perhaps 50 in.oz max. That's about what a reasonable mini servo like a HS-225 can generate (of course not at the rpm a motor can )
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