Spider Roll Bars

["Bain, Bill" <Bill.Bain@domain.elided>]

There's a pretty significant amount of "engineering" required to mount a
roll bar properly in a Spider.  The area behind the seats is basically
an open box section and could collapse under the weight of the car if
the Spider is in "inverted flight", so to speak.  For that reason, the
areas *under* the bar's vertical mounting points need to be reinforced.
If I recall from Russ' article, he used iron pipe as anti-compression
tubes around the relatively long bolts that would go through the inside
area behind the seats down through to the underside of the car. Russ
does have the advantage of having a welder and knowing how to use it.
Alan Ward suggested cutting a slot in both the lower and upper sides of
the box section and welding a piece of sheet steel in the slot and then
cutting off and grinding the edges flush on the top and the bottom.
Note that the box section is NOT quite square so you do have to pay
attention to the angles so that the bolts are straight and not cocked.
In my case, the shop drilled 1" holes through the box section (watch out
for the battery cable!) and then made a jig to weld the tubes to the
bottom backing plate at the correct angle, welded the tubes to the
plate, then welded the tubes and plate into the car and then ground the
tops of the tubes flush with the top of the box section.  Finally, so I
wouldn't have to get under the car, they welded "weld nuts" to the
bottom of the plate so I could put the bar in without having the get
under the car.  Just drop the bolts in from the top and tighten, being
careful not to strip them.  The backing plates for the rear 2 mounting
points also had weld nuts installed so that I could do the install from
the top, so to speak. It takes about 15 minutes to get the bar into the
car and bolted down (longer if I'm in a hurry!).  The whole shop bill
was about $300.  On some Spiders, you need to be careful about the brain
box behind the seats but on mine it just fit without having to move
anything but it's cozy.  There is some variation in Spider dimensions so
you should definitely check and double check the fitment -- it would be
much easier to get my bar in if the shop had moved the bar's mounting
about 1/8" to the left.  You will not be able to close the top if the
padding is on the bar (at least on mine -- Russ' may be different) and
there's no way I'd drive around without the bar padding.

I use an Autopower race bar.  One thing you should know is that the
diagonal cross brace can interfere with the passenger seat belt if you
don't pay attention to the belt when putting the bar in.  (AMHIK)  I
really would rather have had a custom bar made so that it could be even
higher, but I got the bar for a very good price.  If I have one made,
the only thing that'll have to be changed is to move the rear mounting
pads up so that the rear braces will be at the correct angle.   I have a
rack to carry it either on my trunk or off my trailer hitch so that it
doesn't have to stay installed on my way to the track.  Other things I
would think about -- the package shelf is pretty flimsy stuff and
doesn't take to being removed and put back all that often.  I made a new
one out of birch plywood and hinged it in the middle so it's easier to
get in and out.  If you have a Bosch Spider, I would also make a rain
cover for the brain box out of a plastic box since it has been known to
rain at the track and getting the brain box wet is likely not good for
it.

Bill Bain 
AROC Atlanta 
'83 Spider -- Roebling bound if it ever gets warm enough to work on the
car! 
'87 Milano (still no brakes -- way too cold to work on this beast). 
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