Design Dilemma

**RogueTwoRobots** · 9th January 2012, 19:34

I stand corrected then Ewan. I thought your change to 2WD was gyro-based, but now that you've mentioned it was more a weight issue, I seem to remember reading about that. Having said that, it was 5+ years ago so I blame my deteriorating brain cells :wink:

**ewan** · 9th January 2012, 19:42

Know the feeling, I'm struggling to remember myself!
When I changed to an Astroflight on the weapon at an XFM event (before it blew up..) it gyro-danced to a ridiculous degree, but that was after I'd gone to 2WD I believe- so even having wheels pretty much in line with the disc isn't going to solve the problem entirely. The gyro effect will depend on many factors, having a smaller diameter disc and relatively wide wheelbase ought to help though.

**Eventorizon** · 9th January 2012, 20:37

I can see myself doing quite a bit of research in the near future.

The 4wd was intended to counter the gyro force and the beveled edges at the rear were to not let spinners get a good grip. The idea at the front was, if you want to hit me then you are going to have to let me his you, as the angled front edges guide you straight to the disc!

What would happen if s swapped out the Alu chassis for say Nylon, kept the 4wd, the disc and the shrimech, got Lipols or LiFe/A123's and then covered the exterior with 2mm Ti? (we have a sheet of it at uni going spare (Titanium going spare!))

**RogueTwoRobots** · 9th January 2012, 20:49

What would happen if s swapped out the Alu chassis for say Nylon, kept the 4wd, the disc and the shrimech, got Lipols or LiFe/A123's and then covered the exterior with 2mm Ti? (we have a sheet of it at uni going spare (Titanium going spare!))

Ali to Nylon will be a good alternative but don't go too thick or the weight saving won't be that great. 12mm minimum would probably be my recommendation (15-16mm if possible). That should be plenty strong enough for your needs, although you'd still probably have to cut the triangles out of the Nylon bulkheads too. Going to some form of lithium batteries and thinner ti armour will also help save weight, although 2mm ti isn't invincible against the more powerful spinners. I can't say for sure if that would save you enough weight to keep 4WD and the sri-mech, but if you can alter the material densities in your CAD file and search around for some rough weight values of lithium packs, that should give you some idea of what the weight will be.

**Gabe01** · 9th January 2012, 20:54

I still maintain the Bot is too wide reducing this will save loads of weight. I am aiming for a maximum width of 300mm

**Gabe01** · 9th January 2012, 20:56

Yours looks to be about 440-450 mm ish

**RogueTwoRobots** · 9th January 2012, 21:01

400-450mm width isn't too bad for a featherweight. A lot of them are close to that. Obviously the smaller the better, but the GR01s (and most standard drill motors) measure ~150mm from tip to tail, so to fit inside 300mm you need to have them butted right up back-to-back. This isn't too bad in theory, but stick a disc in between them and it's hard to keep the width minimal. With this sort of design however, more width makes the robot more stable/controllable.

**Gabe01** · 9th January 2012, 21:16

You are right indeed Sir, I love designing Robots, I forgotten how much fun it is and a lot easier with a feather. I do applaud the design of this one as it looks interesting. I will unveil mine in a build diary soon. I have to use yellow gas pipe in mine, so the design will be interesting.