NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/alt/hotrod/432

Text File | 1992-12-22 | 7.6 KB | 167 lines

Newsgroups: alt.hotrod,wiz.hotrod
Path: sparky!uunet!rsiatl!hotrod
From: [e-mail] (The Hotrod List)
Subject: Re:  Cosworth BDG?
Message-ID: <vmfr=[e-mail]>
Date: Mon, 21 Dec 92 19:51:40 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.
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reply-to: [e-mail] (Timothy J. Drabik)

 Hi, Timothy -

 I hope you aren't offended I replied in the list instead of via email.
It sounds like you have a nice project, and I'm sure others may have
comments.

-> The Porsche box sounds pretty good.  Would you happen to know whether
-> the transaxles on the 924s and 944s are the same thing?  Gee, a
-> 6-speed ...

 Nope, the 911/914 box is a variant of the VW box; the 924 and 944 use
an entirely different layout.  Frankly, you'd be better off with the VW
- it's possibly not quite as strong as the Porsche in stock form, but
once the offroad boys get done beefing them they'll take enormous
amounts of power.  We're also talking under-$700 here for all brand new
parts.


-> it out.  I also have a line on Cosworth in Torrence (Torrance?), CA.
-> I have assembly drawings from them of their BDG from quite some time
-> back.

 One of the reasons I didn't care for the DFV was reading all the stuff
in Cosworth's packet about swirl pots for the coolant, plugging coolant
leaks, porous castings, etc.  It sounded like the engines had problems,
perhaps localized boiling in the cylinder head.


-> I think I'd like to stick with a longtitudinal configuration so I can
-> get longer suspension links with less difficulty.

 I don't think there's more than a few inches difference there.  The
problem with longitudinal mounting is it fixes your wheelbase pretty
firmly, unless you're willing to sit crosswise with your feet between
the front wheel boxes.  If you demand a reasonable amount of steering
lock and want to run 8" or wider tires, the wheel tubs get enormous
quick.


->  I'd prefer inboard discs in the rear, and will likely use two
-> parallel links on the bottom with a third long, forward-mounted link
...
-> I'm hoping to identify a complete set of hub carriers to simplify
-> implementatio of the four corners.  Perhaps 300ZX, Miata, Porsche
-> 944, who knows?

 That means you'll have to run some sort of system to take care of
halfshaft-length changes.  Fortunately, most FWD cars' halfshafts
allow for length changes.  Scout the junkyards for something that looks
to have adequate brakes, then take the whole strut and halfshaft.  Cut
and modify the upright as required to use your links, then run the
tierods back to the chassis structure.  Toe would be easily adjustable,
and you could design in roll steer if you wished.  Up front, you can
also modify the common tubular McPherson strut into an upright, or you
could take a complete upright/hub/brake assembly from something.


-> will be conventional unequal-length wishbones.  For structure, I
-> envision a fabricated tub between firewall and rear bulkhead.
-> Stiffness will come from wide sills on the outside concealing big box
-> sections that will house the tanks.  Driver and passenger will be
-> seated closely together as a result.

 That's the traditional layout used on older CanAm cars and Jags.  It
works OK, but it's a pain in the ass to feed the loads from the tubular
structure to the center section.  Since the sills/tubs are so far apart,
they provide little torsional stiffness without extremely stout front
and rear bulkheads.  A fabricated-tubing backbone chassis like the TVR
or Lotus would provide at least equal stiffness (and relatively easy
to figure via conventional engineering formulae); be lighter in weight,
and a hell of a lot cheaper and simpler to make.  Don't succumb to the
lure of making the engine and transaxle structural parts of the chassis
- if God had intended cylinder bores and bearing journals to be
elliptical, He would have made them that way to start with.


-> I'd like to try either a completely sheet aluminum structure, or an
-> initial sheet aluminum structure to give shape, followed by composite
-> layup for high stiffness.  Shrinkage of the composite W.R.T. the
-> aluminum skin and delamination are issues.  Any thoughts?

 The SCCA has an /SR class.  These are mid engine, technically two
seater, and usually open cockpit.  How about one of those body shells?
I don't have any actual dimensions or sources, but maybe someone on the
autox list would know.  Failing that, how about a kit car body?  You
might even put an ad in one of the racer magazines for a *real* race car
body - surely those old cars go somewhere to die.  You might even get a
whole rolling chassis to scavenge for parts.  I have a set of photos
from a British car magazine showing some geek who found an old Surtees
CanAm car, just the chassis and body, but he put an injected big block
Chevy into it and scavenged up enough pieces to do the suspension.


-> That's it, just about.  I'd like about 200 horsepower in a 1700 pound
-> car. It's got to have lights, windshield wipers, and be registerable
-> in GA. I haven't looked up the kit car registration rules lately,
-> though.

 200hp - real horses - is going to be an awfully vicious
normally aspirated 2-liter. That's in Dixie Cup territory for the
twincam Escort motor, and even Cosworth suggests regular overhauls.
I'd say a more realistic figure would be 150, given a usable *street*
powerband.


-> (I use AutoCAD v. 12 on a SparcStation)

 Back when I was doing such things (long before Sparcs!) I bought a
5-foot Mutoh track drafter and drew in 1:1 and 1:4 scale.  I cut out a
human figure doll from an ergonomics book and articulated the joints
with little clips, then cut out cardboard "parts" like the engine,
transaxle, battery, wheels, etc.


-> It's got to have lights, windshield wipers, and be registerable in
-> GA. I haven't looked up the kit car registration rules lately,
-> though.

 John DeArmond would probably be the guy to know for GA.  In Arkansas,
it has to have lights, horn, parking brake, and muffler.  Roof, fenders,
hood, bumpers (indeed, entire body), windshield, speedo, etc are not
required. You just sign a statement at the DMV saying it has never been
registered before, and there's $10 for a new title plus $17 reg, plus
whatever they assess you for sales and property tax.  Since Dollar
Billy decided autos were a good source of revenue, Arkansas now has both
new and used car tax; they'd probably have a stroke trying to value a
homebuilt, but you'd have to pay some tax before you'd get your plate.


-> will complete the chassis.  Suspension will be 2 1/4" coil springs
-> and tube shocks (Koni steel racing if I can afford them).  Steering

 That's an expensive way to go.  I like Firestone Airmount units and
conventional tubular shocks.  The Airmounts are smaller versions of the
rubber bladder units you see under "Soft-Ride(tm)" trailers behind
18-wheelers.  It's a rubber air cell with a post that moves in and out.
Firestone makes them in various post configurations, for constant,
rising, or falling rate, etc.  The proper ones for your application are
probably about the size of an old-style quart oil can.  They can be
mounted in any direction, and by shimming the mount and playing with air
pressure you can adjust both basic spring rate and ride height.  I like
to mount my shocks 'way out by the wheel where they do the most good -
and as far as I'm concerned KYB makes good shocks, nobody else comes
close.


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Posted by: emory!chaos.lrk.ar.us!dave.williams (Dave Williams)