Bart,
There are lots of examples of first class low weight to strength examples of
ply design structures, namely racing yachts, Mosquito aircraft & other WW1
airframes, home built small aircraft etc.
In my experience, the problems when they occur, are at the high stress
joints & it is difficult to get the design "right" without eitehr rigorous
testing or by using experience gained over a range of design/build projects
with a common thread.
I would see your project as difficult but achievable if you are gifted &
understand engineering principles, or alternatively, have something quite
close to "copy from".
Otherwise you face a very time consuming & potentially disastrous task.
To my knowledge most plywood design has been replaced these days by GRP
composits, which have their problems, but outperform plywood & where the
total body of experience is now considerable.
Of course its your choice.
Regarding the MGB:
Well I think you know the mechanicals are crude & the engine has a poor
weight to power ratio, to say nothing of the difficulty of utilising modern
developments such as fuel injection, electronic spark, computer engone
management etc.
Bearing in mind your ply construction objective I would look around for a
lightweight engine for example the 2.0 liter Subaru flat 4 which is much
used by home plane constructors.
Again most of what I have said probably echos what others have advised.
On completion would you not rather be responsible for a succesful modern
creation featuring reliablity, stucturak integrity, & outstnding
performance.
Using plywood & MGB bits you are likely to achieve something much less
elegant in terms of achievement at least IMHO.
Good luck
Pete
"bartbrn" wrote in message
So far, I've been laughed out of every Britcar DL in which I've posted
this query -- if no-one here can help me, or if this is the wrong place
entirely, please point me to another more likely place (and not that
HOT place down below -- I've already been given THAT suggestion!)
I'm building what I suppose would be called a component car, except all
I have is the bare GRP body, a metric ton of mechanical gubbins (mostly
MGB), and an enthusiasm for clever engineering. I have a splash of an
Ambro body, the original of which was designed and produced by the team
of Bill AMes and Dewey BROhaugh in about 1959. The body was originally
to be fitted on a Triumph TR2/3 chassis to compete in SCCA Modified
classes, and indeed many were. Others were mounted on everything with a
fram you could think of, and Ambro eventually offered a bespoke chassis
that was run with everything from a 2-cylinder Panhard (maybe) to a
Ford V8 (definitely). Ames and Brohaugh were also responsible for the
bizarre-but-effective "Peyote" special, and if you've ever seen it,
you'll know how it got its name.
So much for the body, except that it is designed in five pieces to
accommodate wheelbases from 88" to 100", and a track of about 50". It
looks very much like, and in all dimensions is nearly identical to, a
Lister "Knobbly." Some people, including the guy at CARS in Oklahoma
City who's still producing the bodies as the Dio "Tipo" think it looks
like a Tipo 60/61 "Birdcage" Maserati, but I can't see the resemblance
myself. BTW, the owner of CARS is producing the bodies with the consent
of Bill Ames, and CARS made the molds from a splash of what Ames
claimed was the last, surviving original Ambro... now it's thought that
the body Ames had might have been *itself* a splash from an earlier
body, but as there's little fine detail, once painted, you truly can't
tell the Dio "Tipo" from the Ambro. The fiberglass work on the newer
bodies is technically much better, however
Sorry, I get long-winded.
Now for a chassis (and this is the point where people usually look at
me like I'm a Martian. I'm *not* a Martian): as a keen admirer of the
work of Frank Costin on Jem Marsh's Marcos cars, a casual student of
experimental aircraft construction, and a great believer in Herb Adams'
"torsion box" semi-monocoque chassis construction, I'm making the
chassis out of 1/4" and 1/2" marine-grade plywood. I could show you
scads of drawings, but let's just say that if you're familiar with how
the Marcos GT and GT1800 were constructed -- not only interlocked
torsion-boxes and deep sill structtures ( a lá M-B 300SLR) to
compensate for the big, open cockpit hole, but 'glass bonding of the
wooden chassis structure to major areas of the fiberglass body as well
-- then you'll know what I'm attempting to do.
A lot of people take these bodies and put them on a whomping great
steel-tube chassis, then stuff some American iron lump in the thing --
like people used to do with Devin and suchlike bodies in the '50s. I
don't want to do that.
What I want to do is mate as much MGB running gear, including engine
and transmission, with the wooden chassis as I can. I'll be using
sandwich-steel-plate reinforcement at all suspension mounting points,
and I was particularly drawn to the MGB because, even though it's
unit-body construction, the separate (bolted-on) boxed stressed-steel
front crossmember carries ALL the front suspension AND the steering
rack, at least keeping (one hopes!) the suspension and steering in
alignment.
My primary question (I *knew* I'd get to it eventually!) is about
caster. I've searched through the Bentley shop manuals and everywhere
else to find a value for the correct camber, but apparently no-one
envisaged mounting the crossmember to anything BUT a unit-body MGB
shell. I want to make sure I design the mounting right to maintain
original caster -- anyone have any ideas?
I'd also welcome any thoughts, suggestions, ideas, tricks, hints,
whatever -- as long as it's not *personally* obscene! I'm an ex-model
machinist (ex-a lot of things, actually...) and a dab hand at
woodworking. I'd like to keep the MG drivetrain (though someone on one
of the Britcar lists told me the engine block is a spongy old load of
codswallops): the 91" wheelbase and 50" track drop it right into the
parameters. I hope I won't even have to alter the prop shaft.
There's my story. Lemme have it!
Cheers
Bart Brown
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