Astroflight Cobalt 40's

[jamesb]

which assuming no friction anywhere in the system and no voltage drop under load gives 3910rpm at 17.2v

meaning for the calculation to still work, loosing no voltage at all (defying physics again) the gearbox, air resistance, and assuming the disk has 1 hour to spin up, means you cannot be less than 80% efficient.

still doesnt add up, but glad your batts are so good JC, at that rate you batts would have 43v instead of the rated 36v

nice

My 19.2V NimH pack (16 cells)is standard 22.3V - 22.4V, even after 3 fights in a row it doesnt go below 20V.

[big_nipper]

We tested little spinner with an rpm meter and got 2050rpm after a few seconds, which worked out to be around the no load speed of the mag motor also, so i dont see where the fuss is coming from. RPM meters (not non-contacting) are 99.9% accurate so I for one would say rob measured it correctly.

[robjones]

JUst tried it on our old physics dept strobe and on a scale of 1-10 the disk is first stationary at 5. Its flashing very very quickly so I think its 50Hz, There arent any other markings on the strobe so I not sure what it means!

having just tested half of my batteries (yike! how many!!) i see where this has come from.

seems ive been doing all my calculations for years based on 66% of no load speed, which is fine on its own, but the batteries have basically cancelled the need to do this by having much higher voltage than stated. I did measure my batts a few years ago and knew they sat higher than stated voltage, but almost always dropped under load to near stated voltage. My newer stuff doesnt drop so low under load.

Appologies, seems Im wrong there Rob, but also right. If batts have the stated voltage, or drop to stated voltage, your measurement cant happen, but based on the 60 battery packs i tested last night, your measurement my well be bang on.

means any robot ive built in the last 2 years was 30% higher rpm than i thought.
inludes the ones coming out this year to then i guess.

Id put it down to cautious ratings on motors and batteries. When first tested (with a caled tacho) pimp 2 went well over 8600 rpm and went over 6k faster than the ideal world values we had should have allowed.

[geeza]

Just out of interest has anyone had their magnets move inside their astros, cos thats whats happened to mine. I think the motor is ok, it smells a bit but not to bad. Anyone got any advice as to the best method to glueing them back in, otherwise I will just do it as see what happens. Thanks,

Ed

[typhoon_driver]

Ed no idea about astros but I remember seeing an article on an american site about putting magnets back into a mag. I would imagine that the same process could be used on an astro.

[aliboy]

Is this it Gary ?
http://www.madoverlord.com/Robots/MagMotorRepair.thttp://www.madoverlord.com/Robots/MagMotorRepair.t

[geoff]

We have had the odd magnet come loose, after trying a few types of adhesives we found Araldite 2014 (RS part no. 372-174 is about as close as we have found to Astroflights original glue.
You need to carefully remove any old glue from both the magnet and motor body, make sure both surfaces are TOTALLY greese and dust free and once the magntet is in place leave well alone for at least 24 hours for the Araldite to cure.
Hope this helps.