Base Plate

Andrew_Hibberd · Post by **Andrew_Hibberd** » Sun Jun 06, 2010 11:56 pm

I am looking at my new robot designs and like most of my designs they have got 1mm polycarb bases. However i have found it to be a little too flexable. Has anyone else had any sucess with other materials for base plates that isn't too heavy?

peterwaller · Post by **peterwaller** » Mon Jun 07, 2010 7:39 am

I think the best material is fibre glass PCB material preferably with the copper removed. I would use it even if my chassis was not the controller PCB. If that is too heavy then carbon fibre sheet is probably a bit lighter although you have to remember it does conduct. I have never worked out the exact weights of these materials maybe I could check that out as I have some of most of them.

joey_picus · Post by **joey_picus** » Mon Jun 07, 2010 10:55 am

Carbon fibre sheet's good in my experience, although I have found it somewhat prone to breaking when hit by spinny things so if the robot's at all likely to get hit on the underside you might want something else, or use thicker sheets than I did (0.5mm)

The best base material I've actually used has been half-hard aluminium as it's very tough and strong but drills easily, that might well be actually heavier than the polycarb though

EpicentrE · Post by **EpicentrE** » Mon Jun 07, 2010 12:18 pm

With regards to the weight of materials, here's some useful info. These values are approximates, and can vary slightly dependant on grade, etc. Let me know if there's any mistakes.

Polycarb: 1.2g/cm?
Carbon Fiber: 1.8g/cm?
Aluminium: 2.7g/cm?
Steel: 7.75-8.05g/cm?
Titanium: 4.5g/cm?
Fiberglass: 1.5g/cm?
PCB Fiberglass: 1.9g/cm?

Note: The fiberglass information is from this page, and the 70/30 mix of resin to fibers might be completely different to what is used for PCB boards.

Edit: Added PCB fiberglass weight, thanks Pete.

peterwaller · Post by **peterwaller** » Mon Jun 07, 2010 1:29 pm

I have just measured a lump of the circuit board material without copper which I guess is made under pressure to get such flat surfaces and therefore slightly more dense and that comes out at 1.9g/cm3.
Normally this material comes in 1.6 mm thick but I have found a place on ebay selling some 3.2mm x 100mm x 120mm sheets for ?1.99 for 5. This stuff is really tough for structual parts like flipper / axe arms but with each sheet weighs 74gms a bit heavy as a base plate unless you do a lot of drilling.
http://cgi.ebay.co.uk/Epoxy-Glass-armou ... 53e051fe9a
I have just ordered another 4 thats 20 sheets for ?14.56 including P&P.

Post by **BeligerAnt** » Mon Jun 07, 2010 7:13 pm

For comparison, the density of HDPE is about 0.95g/cm3, but it is more flexible than polycarbonate so 1mm is not suitable for a baseplate/chassis.

I used 3mm HDPE for RONNY's chassis and drilled LOTS of holes to get the weight down. 2mm might be stiff enough, especially if you can brace it by welding on some stiffening strips.

I think I managed to remove almost 50% of RONNY's chassis, but it did involve drilling over 500 holes! The 3mm HDPE is still quite rigid even with that much drilling, but the welded construction also helps a lot.

If you want to go to the effort of extreme drilling, a hexagonal pattern is most efficient. I ended up with 4mm holes in 3mm material as a good compromise between retaining strength and not having the drill too many holes!

alasdair · Post by **alasdair** » Mon Jun 07, 2010 7:17 pm

Try TUFNOL. A material slightly more dense than it, but it is a very similar material. Great stuff i find.

Andrew_Hibberd · Post by **Andrew_Hibberd** » Mon Jun 07, 2010 9:27 pm

I will try and aim for a 1.6mm PCB base on one of the new robots and see how it gets on. I have got enough room to add a 2mm base but the weight is going to start being an issue. I think if i can stop the base plate flexing so much anticide could be more effective 8)

nyditch · Post by **nyditch** » Tue Jun 08, 2010 1:51 am

I've seen some good success with 1/16" carbon fiber rod assemblies. It's a little more complex to make, but can be extremely strong and good on rigidity. Using some kevlar thread, you can lash rods together or sew plates to the carbon fiber. Then use some black CA glue to glob all over it. The glue partially dissolves the carbon and polycarb if you use it, then hardens. Here's one brand, though there are more sources than this for it. It's the IC 2000 (Burgandy Cap) here: http://www.cstsales.com/cyanoacrylate_glue.html
The accelerator works great as well for fast drying during a competition.

razerdave · Post by **razerdave** » Fri Jun 11, 2010 8:53 pm

I have made the mistake of making Baby Hell's new base from 1mm HDPE, its not very tough, so I was wondering, how stiff is 2mm HDPE if I were to AK47* the base? I can't see much attacking the robots underside directly.

* AK47 = put a lot of holes in it, like the gun does