I can't speak for others. But I aim for 20A per mm². I also rather double up thinner wires than go up a size. Thinner wire solders easier, is easier put un corners and so on.
I can't speak for others. But I aim for 20A per mm². I also rather double up thinner wires than go up a size. Thinner wire solders easier, is easier put un corners and so on.
Gearing calculator; http://howto.killerhurtz.co.uk/calculator.htm
For a very rough estimate, use the Run Amok Spinner Weapon Calculator. Bear in mind that it's only as good as the information you put in.
Let's take, for example, the following:
- 457.2x101.6x25.4 spinning bar (18'' x 4'' x 1'' because most of the online calculators are American save for this one, plus bars are a bit more simple than discs to work out)
- Ampflow A28-400, as you suggested.
- 8s Battery (29.6V)
- Mild Steel Material
Thanks to the Ampflow website, we know that the Ampflow A28-400 has the following characteristics:
Diameter (inches) 3.0 Length (inches) 6.7 Peak HP 4.3 Stall Torque (oz-in) 3560 Efficiency 83% Nominal Voltage* 24V* RPM @ 24V 4900 No Load Amps 4.4 4.4 2.1 2.5 3.2 2.1 Resistance (Ohms) 0.044 0.064 0.076 0.081 0.089 0.190 Kv (RPM/Volt) 205 257 189 287 240 237
We know that our battery puts out 29.6V, and the Kv (RPM/Volt) is 205 - which gives us a no-load RPM of 6068, assuming 100% efficiency. In real terms, again helpfully provided by Ampflow, the efficiency of that motor is 83%, which gives the no load RPM as
5036RPM (rounded down)
Pop that into the calculator with a 3:1 gear ratio and you'll see that the bar above will give you a spinning bar at 1679RPM, with a tip speed (which must be under 250MPH for Robot Wars) of a hair under 90MPH and with a kinetic energy of 2.5ish KiloJoules of energy at the tip of the bar. You'll want a fast spin up time (larger gear ratio, such as 5:1) so that your weapon is up to speed before your bot hits someone else in the arena.
2.5KJ is not enough for a heavyweight. It's barely enough for a featherweight.
(as a guide, the feather weight that I'm designing at the moment has over 15KJ of energy)
Hope this helps
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