RE: Something to engineer

["Brian Shorey" <bshorey@domain.elided>]

> It seems to me that what is really needed, is a track legal Spider rollbar
> that you can put the top over.  Which probably means a removeable rollbar
or
> even better for street use, one that can be extended for track use, but
would
> still provide some measure of protection in daily use.  (My helmet
increases
> my height by about 2 inches, so a bar that would be legal if I was sitting
> there with no helmet, becomes illegal simply by putting on the helmet.
And
> yes I am aware that not having a helmet makes me illegal anyway.  I have
> spent a few minutes pouring over the AROC competition code in the last few
> months getting ready for Nancy Mackey to look over my shoulder at the
> national convention.)
>
> Being able to do this with say a 20 minute install and removal, or one
with
> an add on 4-6 inches would probably make that person rich.  (Certainly
would
> get a lot of appreciation from Spider owners as well as orders I would
hope.)

any bar with a break in the main hoop (i.e. adjustable height) is not legal.
one other somewhat important point is that the rear supports must connect to
the main hoop no more than 6" from the top of the main hoop.  (many thanks
again to those who provided roll bar data).

here's the solution i used, recommended to me by paul glynn.

first, we started with an autopower race height bar.  the shankle and
autopower street bars measure up at around 31.5" tall, the autopower race
height bar measures 34.5" tall.  curiously enough, with the stock spider
seat and a helmet i have clearance, but not a full 2" (solved that problem
by fabricating a new seat bottom).

the first part of the solution was to make up four plates out of 5/8" thick
stock, and weld them into the car.  these plates are drilled and tapped such
that the bar can be bolted and unbolted from inside the car.  for those
interested in the process, the plates were fabricated, drilled, and tapped,
bolted up to the bar, then tacked into place in the car.  then the bar was
removed and the plates were properly welded.

a couple of notes here - it is important to weld the plates to some vertical
surfaces.  we used the entire lip at the leading edge of the rear shelf
area, plus we used the vertical sheet metal along the sides of the car
(under where the convertible top bolts in).

note also that there are three bolt holes in each of the pads of the stock
bar.  because we were not bolting in from the bottom we were able to add a
fourth to each of the pads on the main hoop.  paul also added a bar going
across the roll bar behind the drivers seat, both to keep the belts up and
to prevent the seat from going underneath the bar.

you can stop there, but we went a little further.  we fabricated a removable
bar that connects to the main hoop at the top, sort of near the middle, and
bolts to the passenger floor right against the inner rocker.  we laid out
this bar with someone sitting in the car, so it's not too uncomfortable with
a passenger in place.

the entire assembly can be removed in less than fifteen minutes, maybe even
less depending on how hard it might be raining.  for non track use i can run
the bar without the fore/aft brace, i can also remove the race bar
altogether and run with no bar, or i can bolt in a street bar.

the fore/aft bar really adds to the stiffness of the car, more so than the
chassis stiffener did.  between the two the car is now pretty rigid and
rattle free.

speaking of chassis stiffeners, there are a couple of mods we did to mine.
first, we welded in some triangulation to the front cross member.  boxing
that area in made the whole thing more effective.  second, we added some
1/4" spacers between the rear cross member and the mounting pad, to lower
the rear cross member a little bit.  i found that under some circumstances
the exhaust would hit the rear cross member, the extra 1/4" makes all the
difference.  it is wise to consider adding this spacer during installation,
as the hardware that comes with the chassis stiffener isn't really long
enough, and you need to remove the trailing arms (which is done during
chassis stiffener installation anyhow) to get at all the hardware.

the chassis stiffener makes a great place for a floor jack or lift arms.

bs

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