Date: Fri, 27 Jul 2007 10:27:00 -0400
Reply-To: Jim Akiba <syncrolist@BOSTIG.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Akiba <syncrolist@BOSTIG.COM>
Subject: Re: Decisions,
decisions which conversion-didn't intend to start a power war
In-Reply-To: <010701c7d02e$20b786c0$6401a8c0@TOSHIBALAP>
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Excellent question Scott! With a really easy answer. I'm from boston. Cars
melt here.
We wanted something impervious in the northeast. Remember, we started out
with a set of design goals for Brady's van.. not goals to start a business,
not goals to sell lot's of conversions, goals that WE wanted for Brady's
conversion. The 316L that we use has almost identical tensile strength to
1040 medium carbon steel, higher elongation, and a slightly lower yield.
Property-wise it is great unless you need it to take impacts greater than
the weight of the van regularly(dropping off an 18" rock directly onto
another rock for instance), however it can survive much of that as well (as
per Brady) on impact it will distort a bit, but the key point is it will not
fail.. you can take the distortion out if you need to easily you don't need
to touch the paint up cause there is none. But this isn't ideal either,
other folks have different wants than we do, and it's best to heed them.
But that is why there is another engine carrier option that will be
available as well. The important bit for us was that the cradle be zero
maintenance.. which the stainless is. This means that the as designed and as
built mechanical properties of the assembly will not change over time
either. Stainless isn't used by oems because of cost and cost of processes,
they must never do anything that isn't absolutely required. Hell the oems
didn't even start using higher grade stainless exhaust until recently... and
only because of aftermarket pressure making it into the mainstream. We do
not suffer the same limitations as OEMs, however the cost factors and
passing on the savings to those that don't need/want it is a good idea to
bring the cost down. Some guys are lucky enough to not rust, but not around
here! Again though, that's the reason to pursue other options for the
off-road cradle, which will either be mild steel or chromoly which as you
know is king of tough alloyed steels(other than some totally cost
prohibitive super alloys). You also assumed rigid was a desired property of
the cradle, but rigidity at what scale is what is important. The stainless
cradle is quite tough, and totally maintenance free, and will remain as
strong in ten years as it was the day it left us, that is not so of the
other materials we could have used. Additionally, along the way we've made
two chromoly stainless encapsulated cradles as well. This composite metal
cradle combines the toughness and strength of the chromoly with the
impervious skin of high grade stainless, still zero maintenance.. and even
more robust. But again, expensive, and some guys don't need the stainless...
we've gotten that loud and clear! I'll show you shortly just what I have in
mind.
Jim Akiba
On 7/27/07, Scott Daniel - Shazam <scottdaniel@turbovans.com> wrote:
>
> Hi Jim, thanks for posting that, the 'matrix' as you call it.
> I'm curious why you'd make a stainless engine cradle .
>
> In the cost/weight/strength blend and considerations.....
> Something built for brute sense like an engine cradle, would be thicker
> and
> more expensive in stainless, than the equivalent steel piece.
> The vanagon engine cross bar is a perfect example....for the
> cost/weight/strength balance.....simple steel is called for.
>
> To make the same part in stainless.....stainless is nice for corrosion
> resistance, but it's not as strong as mild steel for a given
> thickness.....
> would cost more, significantly more, I'd think, for the same strength.
> Hence you don't see stainless engine cradles anywhere ....
>
> Seems the 'next most rigid light weigh cost effective ' material would be
> cast aluminum, and you do see that in car design.....like the diesel
> engine
> mounts for example....light weight, doesn't corrode too easily, not
> expensive in mass production ( a factor for you as you are making say, 50
> to
> a hundred per year, , compared to 50,000 for a manufacturer, so exotic
> castings are not justified in small numbers, , leaves you with mild steel
> normally, from a cost/ strength viewpoint. There could even be a few
> bucks
> in saved money there you could pass onto your customers, by using steel
> there. Easier to fab , everything. Cheaper. Etc.
>
> Anyway, I think what you are doing is fantastic !
> Scott
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Jim Akiba
> Sent: Friday, July 27, 2007 12:37 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Decisions, decisions which conversion-didn't intend to start
> a
> power war
>
> I just posted the matrix that I started working on long ago(in 06
> actually). I never did anything with it as I was not certain of the
> value without oversight. But now with google apps, if anyone would
> like to help fill it in, and have collaborator access for editing
> please let me know.
>
> http://spreadsheets.google.com/pub?key=pTRYtmiQuaK3fqBbHuKk1OQ
>
> Thanks,
>
> Jim Akiba
>
>
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