Astroflight Cobalt 40's

[jamesb]

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

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]

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

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]

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]

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

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

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

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

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.