Astroflight Cobalt 40's

[ewan]

Astroflight Cobalt 40s

Ed does has a point there

[geoff]

Astroflight Cobalt 40s

Astro + 1.7:1 reduction + reasonable load = 1 bloody hot Astro!! (even @ 14.4V!)

[james...venom]

Astroflight Cobalt 40s

thanks guys. didnt know how acurate that rpm per volt equation is as i wouldnt of thought it would be an equal rise between the voltages. increased heat and all that gubbins may play a role in slowing the increase to speed down as the rpm goes up? guess not lol

geoff i plan to add another 2:1 on it. hopefully it wont burnt out.

On another point do you know how good the astro 25s are at takeing load? hopeing to use one in the selfrighting arms.

[geoff]

Astroflight Cobalt 40s

1.7:1 X 2:1 = 3.4:1... I wouldnt want to go any less than that for something like a spinner drive.
As for the 25s, had no dealings with them.. sorry.

[james...venom]

Astroflight Cobalt 40s

ye im actualy after a 3:1 or 2.5:1 reduction but RS only do the 2:1 bevel gears.

the astro 25 would be geared down 30:1 then attached to a thread which will make the arms move. it may come close to stall as the arms are on a 10:1 leverage?

[jamesb]

Astroflight Cobalt 40s

30:1 on an astro 25? very fast that, 100:1 on standard 540 motor is about the same torque but a lot less cash. (without doing any maths on torque im making an educated guess).) i have some of these for sale if you think they might be suitable.

as to the spinner, listen carefully to geoff and john from scorpion, i am sure nobody in the uk knows more about these in this application, and problems that occur as a result. shame you gave up on the nitro engine though

[big_nipper]

Astroflight Cobalt 40s

James, I dont know what kind of calculations or system youve done but 30:1 seems small for a lifter. As an example we use 900:1 on Big Nipper, ok its not on a lever but still stalls the motor when 2 or 3 robots get on it, to help we also current limit the motor. Also running an astro near stall for more than a few seconds will destroy it so be careful when you test it or use a current limiter.

[jamesb]

Astroflight Cobalt 40s

speaking of which, for the weapon and arm motors, why not buy a sidewinder? perfect for this job eh?

[james...venom]

Astroflight Cobalt 40s

send me some specs james.

ye the nitro engine was just far too unreliable.... real shame :sad: besides i doubt many events could run an engine safely as if the feul cought fire you wouldnt see it burn easily.

the gearbox on Venom is 22.5:1 which works out at 355rpm and that is a nice speed. the arms on predator have a 10:1 disadvantage which speeds them up again. i did work out the power in the arms, it was good for selfrighting. 30:1 works out at 466rpm i think which should raise the arms in 3 secs.

[jamesb]

Astroflight Cobalt 40s

all specs for sidewinder on http://www.robotpower.comwww.robotpower.com
prices around £250

specs for 100:1 motor
voltage 4.5V 6V 9V 12V 15V
100:1 rpm 35 50 77 103 134
prices £20 each

email me if interested

[robjones]

Astroflight Cobalt 40s

we run our 3kg disk on a 940astro at 14.4v. Also fitted a cpu cooling fan above the motor. Pulley ratio is 3:1 giving a tested max rpm of 3150. No problems with overheating so far.
Rob

[jamesb]

Astroflight Cobalt 40s

thats 9450 rpm at the motor rob.
defies physics, or your batteries are giving a lot more than 14.4v
with any kind of teeth, or any kind of mass, a realistic maximum you can expect is 66% of no load speed (this varies a lot but is a ball park figure.)

for 14.4v, to get 3150 on a 3:1 ratio, you must have zero air resistance, zero transmission resistance, and measure it after an hour of spin up starting. I would suggest your rpm meter is inaccurate Rob, or your batts are amazing and produce a lot more than 14.4v

or astrolight have varying rpm/v specs, or any one of a thousand reasons, but as is cant happen

[robjones]

Astroflight Cobalt 40s

dunno james, ive used the rpm meter for a couple of years and i think its ok but it could be wrong. can a pair of gp 3300 mAh 7.2v cells deliver much more than 14.4v, doubt it. its probably the battered old rpm meter. ill get the strobe on it next week.
rob

[jamesb]

Astroflight Cobalt 40s

you can expect as much at 16v plus from good barreries labled 14.4v, but still, seems too high.

[james...venom]

Astroflight Cobalt 40s

i get 8.6v out of my 7.2v Nimhs easy and thats not directly after chargeing. 16v for 2 packs i would not be happy with.