Date: Wed, 21 Aug 2002 04:12:11 +0100
Reply-To: Clive Smith <clive.harman-smith@NTLWORLD.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Clive Smith <clive.harman-smith@NTLWORLD.COM>
Subject: Re: SURVEY - I need a metal fab. project
Content-Type: text/plain; charset="iso-8859-1"
>The main purpose for me is crumple zone
If thats really the case, then aluminium would not be the best choice.
A crumple zone is usually a complex structural arrangement of panels and
that aims to
absorb the maximum amount of energy for a given displacement, effectively
using strain energy to
to its maximum. Surprisingly, mild steel is a good medium for this, as it
work hardens considerably with strain and
has quite a high ultimate. Most ally alloys don't, although I imagine that
careful design and choice of material
can give good results, although you'd probably end up with a fairly weak
bumper to start with.
As an example of how difficult this engineering science is, the Chevy
Spacewagon thingy sold here (UK), that looks like
some sort of space ship at the front, came about 1 on a scale of 10 when
tested against comparative vehicles in Europe.
Not that other people carriers weren't quite shockingly poor as well,
particuarly in a rear shunt - this goes against what
a layman would imagine by looking at these vehicles - they're big, shiny,
flashy high tech looking things - surely they are
at least as good as 80's and 90's old fashioned looking cars? - NO.
If I were you, I'd just make sure that bumper's pretty stiff in the fore-aft
plane, so that small dings don't distort it alarmingly,
and large blokes jumping up and down on it don't either - a properly
designed crumple zone might well not suffer those insults
without needing replacing soon after.
Good Luck - I'm sure it'll look a lot better than most bull bars and
transfer its loads properly into the chassis.
Now a fully composite energy absorbing bumper might really interest me.
Honeycomb interior, kevlar facings and ribs/webs with maybe a bit of carbon
thrown in for stiffness.
Mmmm - anyone out there with composite experience and autoclaves in their
workshop that could fab that if I drew up a design,
NOT that I'm looking for a winter project - I've a van that needs a thousand
jobs before its ready for a jaunt through Europe.
Clive
'88 Syncro
----- Original Message -----
From: "Steven Dodson" <steven@EPOCHDESIGN.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, August 21, 2002 1:08 AM
Subject: Re: SURVEY - I need a metal fab. project
> I am going to fabricate custom bumpers for Inga next summer.
> I'm planning on modeling them after the big truck aftermarket bumpers.
> Definitely the "DFWM" kind. The main purpose for me is crumple zone. I'd
> like to get a few more inches of deceleration between me and the next guy.
> They'll be lightweight aluminum and will double as something to climb on
and
> attach things to. I plan some holes for lights, spots for winch and hitch,
> tread plate on top and round corners to increase the aerodynamics. I have
no
> idea how much it will cost me but it will be a fun project and look very
> cool.
>
> -Steven Dodson
> Kneeland, CA
> "Inga" the 87 Syncro
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
> Of Chris S.
> Sent: Tuesday, August 20, 2002 3:52 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: SURVEY - I need a metal fab. project
>
>
> I vote for BUMPERS! please?
>
> Chris.
| 
