Astro-05 cobalt help please - RC Groups
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Apr 02, 2012, 03:40 PM
Registered User

Astro-05 cobalt help please

Hi everyone. I need a little advice and help on an Astro-05 cobalt motor with gearbox and speed controller.
While searching an car boot sale just recently i noticed a 7 foot glider in lovely condition for sale. When making the purchase the stall owner when handling the glider fell and smashed the thing so vastly knocking down the price!!
I got this MUCH cheaper.
Not able to repair i dismantled and i have an Astro -05 cobalt and a Astro model 211 speed controller. max 25 volt/ 65 amp.

I ahve looked at the Astro site and i gather they no longer do this model, however i have found they were/ are a very good motor to use.
Yesterday i decided to run her on test just to see what kind of power/thrust output i could get.
I ran it with a 11 by 7 prop on 12 volts/2400ma.

I was impressed with the output and the length of time it ran.
I know nothing about these motors and assume they were great in the US mostly used for glider power.

Will try and post a few pics on here to let you see, but but what i really am asking is, what type of airframe could i use this motor in and what size. ie weight, wingspan ect
I am not into gliders really but i have built a few warbirds and nice flying wings on nitro and do use overlander brushless in some.
Can anyone tell me anything about this motor please? i would be most gratful for any help.
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Apr 02, 2012, 11:07 PM
Registered User
Philipp's Avatar
From the picture it looks to be a 7 Turn motor which was rated as 2125 rpm/volt. Good for 30 amps or more. The gearbox that is attached will, of course, lower the KV and it looks to be a 3.69:1 ratio. You will have to count the teeth on each gear to be sure. The standard GB was a 2.38:1 If it is the 3.69, it was shown to run on 10 NiCad cells. (15v max, but many have exceeded this somewhat) They recommended a 12.5 x 10 prop for normal flying.
The speed controller is one that is in between any that I have any info on, but it will not have any LVC built in and should be good for 30 amps also. It should say how many cells (NiCad) are recommended on the surface of it.
Parts and service and information are all available from Kirk at New Creations RC Excellent motor and controller!
Apr 03, 2012, 02:18 PM
Registered User
Hi Philipp, thanks so much for your reply and help in this matter. Last year I built a hurricane from some old plans. Only had a 30 inch wingspan and run on a small nitro. I really did like it and it flew so well. I was just thinking would this be ok as a power source to build another and slightly bigger or an old vintage bipe of some kind?
I will take a look at the controller and see if the quantity of nicad cells are recommended.
Once again thank you and if you have any further information on this, please let me know.
Apr 03, 2012, 03:15 PM
Registered User
Hi ya. I took a look and it has no nicad recommendation on it. Just says astro model 211 digital speed controller with brake and recommended inputs.
I counted the teeth on the motor gearbox and it 13/31. Thanks.
Apr 03, 2012, 04:10 PM
Registered User
Ken Myers's Avatar
That is the standard gearbox on it, not the Superbox, so the gear ratio is, as reported 2.38:1.
Apr 03, 2012, 04:37 PM
100% electric since 1990
twest's Avatar
Replace the connecters with anderson, astro, or deans. Use it up to 3s lithium and up to 30 amps. It would work well in any plane that runs on 300 watts - lots of 50 - 60 inch trainers, and many 3 lb or so sport planes.
Apr 03, 2012, 06:35 PM
Senile Member
Lnagel's Avatar
I suppose you could run this motor at 300 watts if you wanted, but Astrflight recommends running it at 7 volts with a 12x8 prop. With that the motor should pull about 24 amps at around 170 watts and about 75% efficiency.

Apr 04, 2012, 02:50 PM
Registered User
Thanks so much for your help and information on this for me. Having only ever flown nitro apart from few shop bought electric, going into the electric scene is daunting. A lot to learn and know. But for what you have all told me its been a great help. Thank you.
I will take the advice and change the connectors and look for something to build or convert in the ranges you have stated. Its a nice solid, well built motor and i will now put it to good use.
Apr 04, 2012, 03:08 PM
100% electric since 1990
twest's Avatar
Over in the "sport planes" forum, there is a link to a new version of a kit of Bob Benjamin's "tigerkitten", a classic design from 1992 (classic for electric design, that is.)

Now people are flying these on outrunners and such, but the original flew with an astro 05 geared on 9 nicad cells (very close in voltage to a 3s lithium) and a 12-8 prop, close to 300 watts. Check it out, it is a real "builder's kit", with lots of intricate parts and builds into a sharp looking sport plane. I have a kit from the 1990's that shows the astro 05 right in the plans.

Edit, here is the link:
Last edited by twest; Apr 04, 2012 at 03:14 PM.
Apr 04, 2012, 05:09 PM
Closed Account

specs for 05

Grossly underated on specs- probably could add 30-50%
Last edited by jim e; Dec 08, 2014 at 06:15 PM.
Apr 04, 2012, 06:32 PM
Registered User
vintage1's Avatar
1/. I have a lot of Astro spares should you need them

2/. As its geared you can go up to 3s LIPO and it will run forever on sub 30A. Over that I believe that they tend to burn the brushes quickly.

3/. you should be OK on a 10x7 on 3s - meter it and see. Maybe an 11x7.

4/. I like these best on big old vintage models. This will fly a 72" model that way you can have peak static amps up at something in the mid 30's but generally cruise in the 10-20A range. They also make great scale power plants. down on 2 cells with a 12" prop on say its enough to balance a 36" sopwith camel.

lovely quality motors - probably the best brushed motors ever made, though some of the German and czech motors come close. And, given 2.4Ghz, any interference issues ewe used to have with brushed should not be any problem. I wouldn't use them in a competition glider any more though.
Apr 14, 2012, 02:53 PM
Gravity sucks.
mrittinger's Avatar
I have plans for quite a few 42" warbirds that would work fine for this setup...fancy a Spit Mk 1 or Hurricane?
Apr 14, 2012, 07:33 PM
no more glow models for me!!!!
iflyrc1012's Avatar
i just ran across 2 of these motors. no gearboxes, never run. if anybody wants to buy them, shoot me a p.m.

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