Peter Wallers Robot Ramblings

[peterwaller]

Just dug out the other half of the cluster and I have another 15gms I can add (or another alsoran).
A couple of shots to show the difference in size.

[Remote-Controlled Dave]

That spinner is pretty nasty as it is. Another Also Ran would increase chances of winning battles I reakon, long as your drives can keep them away from your own blade.

How many Also Rans can you get in a 3" cube? Could have a 5-way cluster in the fleaweights!

[Psychostorm]

That spinner is pretty nasty as it is. Another Also Ran would increase chances of winning battles I reakon, long as your drives can keep them away from your own blade.

How many Also Rans can you get in a 3" cube? Could have a 5-way cluster in the fleaweights!

Having driven Also Ran, I'd say a second botlet would be synergous. If the spinner (as it frequently does) goes flying out the arena, Also ran was left the sole focus of a full antweight (Bulletproof?).
A second botlet would add confusion by being an attacking force as well as a literal distraction.

[Remote-Controlled Dave]

Yeah, I agree. Especially now they're quicker.

[peterwaller]

Having met mark_m at Brighton on Saturday he has convinced me that there is a stability problem with blades like that on my exploding spinner.
By throwing his mobile in the air spinning in each of the three planes he demostrated that one was unstable.
Back home I have been able to replicate this with my blade which when thrown into the air with spin imparted in the plane that it spins on the robot it does exhibit a rotation at rightangles to that spin.
Obviously this is a small force but as you wind up the speed I can see it explaining the problem I get.
Here are some frames showing in the left column the spinner as standard which twists so through 90 degrees and in the right column with a flybar type piece of plastic that mark suggested which seems to fix the problem.






The flybar I tested with is too big for the cube and I need to get the weight down to enable to be added but I think it has given me a chance to maybe sort this problem and even a way to test the blade without destroying the robot.
Thanks again mark.

[joey_picus]

Might be a bit late in commenting (hello from Edmonton incidentally) but I really like the new Alsoran - are those the Solarbotics pager gearmotors or similar motors? I've thought repeatedly about building something around one of those but lack of suitable wheels was an issue before - now I'm wondering if Lego wheels could be bodged onto them for more stability fighting things four times their weight...

The news about the stability problems potentially having a resolution is promising incidentally - I'd noticed that effect a lot in robots with that sort of design at all weight classes but didn't realise it had a name before! Hopefully you can fit it in the cube and it does some nice damage at the AWS

[peterwaller]

I have now machined a new weapon arm the incorporates flybar type arms and sure enough when spun in the air it appears to be stable with no tendency to turn at right angles.

As before with the vacuum running I can take it up to full speed but without it it becomes unstable and leaps into the air spinning.
http://youtu.be/-7dGTiXsb4c
The good thing is although the wheels came off with the battery now tie rapped in place it didn't suffer any damage.
It is beginning to look as though I will have to rely on the suction or limit it to about half throttle.
Looking at the video again I am not sure the failure is quite the same it appears to vibrate and start to turn before leaping out of the arena.

[josh]

What if the two bars were a disk with the teeth bolted on, you could then support the disk with bearings at the outer edges to stop it tilting and hitting the floor?

[peterwaller]

I don't think that would really help as the robot can always tip enough for the blades to touch but I don't think that was the problem.
If you look carefully the blade is rotating an an anticlockwise direction so if it is a torque spin due to the tyres loosing traction or the blade catching you would expect the chassis to spin clockwise but it spins anticlockwise as well.

[Remote-Controlled Dave]

When you turn the suction off, does the entire suction pad lose suction all at once? Looks like maybe one side lost it slightly quicker than the other.