Peter Wallers Robot Ramblings

[haz]

That kinda thing looks like it would rule at minisumo.

[peterwaller]

Unfortunately fans and other methods of effectively increase downforce are not allowed in minisumo.

[Hogi]

i saw a little fan in maplin today that i thought might do the job in a fan pusher. it was less than a fiver. it was quite a large blade diametre and it came with an inbuilt brushless motor. if i knew how to wire in a brushless motor i'd have brought it as theres loads of weight left on transit ant that i could use to incorporate a fan. can the servo plug in port on a speed controller be used to drive a brushless motor?

[dcr raptor]

I don't think that the servo port on an esc can be used to drive a brushless motor as the signals sent to brushless motors are different to the kind used for brushed motors and servos. As far as I understand, servos and brushed motors receive the signal as a constant stream of information, whereas brushless motors receive the signals as impulses, which is why you can't use a standard esc for a brushless motor and also the reason that each brushless motor requires its own esc.

[Hogi]

oh right, where could i get a cheap brushless ESC from and how would i wire one in?

[Rapidrory]

More to the point, those brushless fans in maplin are for cooling. They have the ESC built in, but produce almost no thrust/ suction; I was playing around with one earlier as it happens, and even with it cranked right up to 30V it still didn't produce anything in the way of useable downforce.

[peterwaller]

The one I have doesn't produce much thrust, max of 100 gms in good conditions more like 30gms when the air intake is under the robot.
I am using it to generate a partial vacuum below the robot.
Initial results looked good the push on my measuring rig went from around 250gms to in excess of 600.
The problem is the unit is not really up to it as the impeller is on the end of 25mm long 1.5mm diam shaft which under load flexes enough for the blades to touch the case. The shaft is now bent and this causes a bad vibration so I need a different fan unit all be it that the principle seem to work.
I might try using the 40mm one I have but with a brushless motor which would greatly reduce the height of the unit.

[peterwaller]

Bit of a change of direction but I have just been having another play with molding tracks.
The problem I have been having is rubber that is soft enough to give good grip is stretches enough to come off the drive wheels in hard turns.
I have thickened the tracks to 4mm not counting the tread or drive teeth but although better in can still occasionally come off.
I tried adding 2 mm rims to the wheels but the grippy rubber just rides up them.
The answer I think is a guard around them so I have fitted them to my Dominant chassis which has wrap around scoops.

At the moment the scoops are off so I can fit the tracks but with a lump of ali angle to give a vertical front to fit my spring balance test rig dominat comes out to 117gms with the tracks and 115 with the old wheels with molded tyres.
The wheels give a peak of 270gms push and the tracks around 400gms so a significant improvement.
I might see if I can improve the scoops and may be slip it into the team for the next AWS.

[peterwaller]

I have replaced the Aluminium scoops with 1.5 mm thick polycarb which brings the weight down to 127gms.

So Dominant will replace Defiant in Termite cluster so the team for the AWS looks like this.

[Hogi]

awesome!