Speed 900s

@ 12V the original Speed 900 draws 54A max. Let us take that as a given. (I messured more, but hey, that's another matter)

54A for 3 minutes is 54/20= 2.7A used. LiPo doesn't like to be deep-discharged,so, we add 25% to that= 3.375A

A 3S 3500mAh 20C pack will do. Theoreticaly.

What kind of relay would you need to turn on and off 2 real Speed 900's? Something that can be linked directly to the Landing Gear PWM output of a transmitter would be good :)

i believe the set of you require is a battle switch linked to an automotive relay, I think 70 amp and upwards is the norm

However I don't have any first-hand experience

Get yourself a battle switch and one of these

http://www.jaycarelectronics.co.uk/prod ... rm=KEYWORD

The battle switch provides the RC interface to the receiver. You wire it up in such a way that when the battle switch is operated, it operates the solid state relay control side. The motor(s) are hooked up to the power side of the solid state relay. One of these will happily handle two speed 900s as long as it's attached to a metal panel to act as a heat sink

With little else to do this morning I have drawn up the following circuit diagram

http://imgur.com/skP9N

It should only be used as a guide! The important things to note are that the solid state relays are polarity sensative. Make sure that the negative pole goes to the negative connection on your batteries and same with the positive. You won't damage the relay if you hook it up the wrong way around but you will instead have a weapon system that will fire up when you put the removeable link in (not recommended)

I know it has been done in the past but will I have the only current robot with two speed 900's to power the weapon; just curious? I am also using a quite a low ratio 2.667:1 so the top speed will be really high (Approx 2500 RPM), I just hope that I can get it up to that in a fight!

Inertia XL uses 2 Speed 900s.

http://www.youtube.com/watch?v=5J6D7vZh6zk

2500 rpm is slow for a spinner and a single speed 900 will get there in seconds.

hi, omen runs 2 speed 900s.

2500 rpm in seconds pfft go brushless then get 0-8000rpm in 1 second :twisted: