Material Rigid Thickness

[PJ-27]

It's a bit of an odd question, and not one easily answered through web searches so thought I'd simply ask what were other peoples experiences.

I need a material for my BW that is as light as possible for it's size while maintaining rigidity. At the moment it uses 1mm HPDE (Light strong, NOT RIGID) and Grade 4 Ti (Light, incredibly strong, very bendy!).

So I'm looking for alternatives:

Would Polycarb be more ridig at a similar thickness? And what would the weight increase be?
What about Aluminium for the chassis, this would be less bendy than G4 Ti, but what thickness? And what would the weight increase be?

Also if people have Density stats for the materials (and the specific grades) that would be great. I don't know if there is a measurement for rigidity? And I'm assuming this in some way relates to overall size of the sheet.

Thanks,

ps. I don't think I could have gotten the word rigid into this post more times if I wanted to......

[Mouldy]

Re: Material Rigid Thickness

id suggest 1.5-2mm ali, bend it up at the edges to make a U section down the length... that way you will get the rigidity of thick material while keeping it light.

[maddox10]

Re: Material Rigid Thickness

Stiffness is more a question of shape than thickness.
For example, a tube is stiffer for the weight compared to a simular diameter rod.

Another example is corrugated sheet metal.

The ultimate weight/stiffness ratio record is held by Aerogel. But I guess this material ain't good for RW.

[PJ-27]

Re: Material Rigid Thickness

Neat idea, do you think it would work with the Ti?

[maddox10]

Re: Material Rigid Thickness

Bending Ti into a U , why not, but keep in mind Ti doesn't like sharp corners. (most metals don't)
Bend it over a piece of rod, 2 times the thickness of the sheet in radius.

[PJ-27]

Re: Material Rigid Thickness

The thickness is 1.9mm so the rod has a diameter of 3.8mm. 3.8 x Pi = 11.9mm of material to make the curve (assuming a full circle is formed). I'll have to check if I have that much available on either side of the chassis.
Any advice/resources on how to machine it?

[maddox10]

Re: Material Rigid Thickness

Machining Ti?
Anglegrinding gives nice sparks.
TIG welding is possible with an inverter (DC) and loads of argon.
Use enough coolant/cutting oil to keep the drill in reasonable shape. But a normal good quality steel drill will do fine.

[PJ-27]

Re: Material Rigid Thickness

Sorry, I mean to do the bend? A rod that thin I can see being impossibly difficult.

And yes you get amazing sparks! Dan spent quite some time in the workshop just grinding an offcut for laughs.....

[maddox10]

Re: Material Rigid Thickness

Any rod of nearby diameter will do. Twice material thickness is a minimal guideline.

Another option is to use a thick walled box section , that has a nice round corner too. Is also easier to put in the vice together with the Ti plate.

[gizz]

Re: Material Rigid Thickness

I'm not sure on the difference in bending between different grades of TI, but my 1mm grade 2 seems very stiff.
Thought the higher the grade the harder and stiffer it would get?

[PJ-27]

Re: Material Rigid Thickness

I believe Grade 4 has the highest elasticity rating of them all.

[typhoon_driver]

Re: Material Rigid Thickness

get a bit of heat in it too. Not enought to turn it red hot but a couple hundred degrees won't be a bad thing

[Mouldy]

Re: Material Rigid Thickness

As Gary said, stick it in a vice- blow torch it, then bend it over...will bend like butter... thats how i did 360s selfwrighting bar...thats 10mm ti.

or... take it to a local engineering shop and ask them nicely... would bend easy in a press or even a hand bender...

for the reccord when grinding Ti as suggested above... wear a mask as the dust is a carcenagenic.

as for TI flexibility...they get more bendy the lower the grade... grade 1 being real bendy- 4 being pretty stiff... 5 being un bendable without heat....all todo with the alpha beta particles in the Ti...

i used to have a sponsorship deal with http://www.titanium.com until the manager i knew left the buisness... he told me alot of stuff and gave me plenty freebies.

[jonny]

Re: Material Rigid Thickness

you can bend grade 5 cold, i've done so on antweights.

[Mouldy]

Re: Material Rigid Thickness

yeah.. on thin stuff sure.. how thick was it and what angle?