how hard should I try to fabricate with two equal seats

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n1gzd
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how hard should I try to fabricate with two equal seats

Post by n1gzd » Mon Jul 11, 2011 8:44 pm

Hi,
I am at the stage where I need to decide exactly how the supports for headrest and seat belts are to be fabricated for my Midget. It is pretty straight forward how you would do it for a 1 seat car. I looked at all of my pictures of similar cars and none of them has two seats. It seems that I have two choices, keep driving my Saab when I need an instructor or figure out how to install two seats with belts and headrest without causing the roll cage bracing to be a strange design.

This is my dilemma. Do most people build a single seat race car and just do the training in a regular car or is it smart to figure out how to fabricate exactly the same setup on both sides. It is much more difficult.

thanks for your comments.

Rebecca

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Re: how hard should I try to fabricate with two equal seats

Post by n1gzd » Mon Jul 11, 2011 9:03 pm

perhaps an instructor would not want to ride in an MG midget anyway.
Also, the rollbar might be the wrong height for a tall instructor (not to mention the rest of the seat and belt geometry). It seems that when you build this kind of thing it needs to be built for a specific person and in this case, I don't know who it is. I am sure that I might stick an optional seat there (possibly for right seat autocross but not track).

any opinions?
Rebecca

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Re: how hard should I try to fabricate with two equal seats

Post by breakaway500 » Mon Jul 11, 2011 10:27 pm

One of my favorite cars had zero HP and would do 50 mph..according to the Fathers that owned my "race track". :D

I think most instructors will ride in anything safe.

Having a passenger seat can be very useful.Instructors..students....Inlaws... :shock: :lol:

A nicely built double hoop bar would allow for an occasional passenger,and keep the car looking..vintage.(in my eyes) Something along theses lines....this is for a Miata..,but I am sure something like it could be built. If you make both sides low for shorter people,you will limit the seating capabilities.
If you make both sides able to take taller people..you limit nothing,for the same money. :wink:
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McMahonRacing
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Re: how hard should I try to fabricate with two equal seats

Post by McMahonRacing » Tue Jul 12, 2011 7:58 am

Design for SAFETY, think a full halo ....... not a big fan of single rear bars or the double hoop deal .... Vintage or not, Passanger or not it is occupant safety that should be the # 1 concern ..... that being said, a full halo will create better head protection esp. when you consider measuring from the top of the rear bar to the best structure in the front w/a string (fyi this doesn't count a windsheild or screen) .....

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Re: how hard should I try to fabricate with two equal seats

Post by 6PAK72 » Tue Jul 12, 2011 2:29 pm

grp44tr6_tr7.jpg
grp44tr6_tr7.jpg (71.18 KiB) Viewed 951 times
When I turned turtle, the bar that would have helped most had I had a full cage, would have been the center bar from windshield frame to seat frame, or a bar diagonally from above the driver seat to the passenger side A post down tube.

This would have prevented the roof from coming in.

If you're going roofless, I REALLY would advocate for you to get a 3-point connection over your head - the driver A to B post transverse, the Driver B to Passenger B post transverse, and some sort of diagonal from Driver B to Pass. A. And, your passenger might feel better if he had the same over his head.

Take a look at this cage in a vintage. The TR6 is a true vintage cage - no overhead safety. The TR7 in the background is a 1979 SCCA rules cage, and you can see the cross frames.
Jeff Baker
Wilton, NH
#42 95 Miata
72 TR6
79 TR7 V6 in shed

n1gzd
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Re: how hard should I try to fabricate with two equal seats

Post by n1gzd » Tue Jul 12, 2011 9:46 pm

We have decided on a solution that will enable both seats to be installed with the same requirements.

Here is a descripition (I will post pictures as soon as it is interesting - half built right now). I am using the SCCA rollbar specifications with some extra stuff added. The tubing is 1.5 inch DOM with a wall thickness which is appropriate for a car that is over 1500 lbs (the car was lighter than that before we started). The reinforcement plates that the tubing is welded to (and that is also welded to the body) is the same gauge. The welding is TIG of course.

There is a main hoop behind the seat which is 3 inches higher than my head (designed for me to be the driver). It is square with rounded corners (as is commonly seen in vintage cars like mine).

From the top of the hoop there will be two rear braces that go into the trunk and are braced against structural parts of the car. There is a hoop under the panel that would prevent the steering column from being mashed down if stressed from above. There are two braces that come from the main hoop across the door area and attach to the side parts of the under dash hoop. Currently I don't plan on puting any vertical connections between these to fill the gap in the door area (it could be added later if I change my mind). There is a center brace that runs from the top of the hoop down to the area near the right seat passenger left foot.
there are two diagonal braces in the main hoop which meet in the middle of the center bottom area under the hoop (bracing it from both sides added more weight but permitted exactly the same headrest mounting area on both sides). There is a horizontal brace that runs horrizontally though the diagonal braces. This is for attaching the seatbelts. they will be bolted not strapped. The back of the aluminum seats will also be bolted to this bar. The headrest will be mounted above this on the diagonal braces. It will be about 6 inches and either round or oval (stuffed with the appropriate stuff).

The seats are Kirkey 15 inch aluminum low back (vintage style) with apolstered insert that snaps onto them. One is mounted so far. I am happy with that so I will order another one for the passenger side. The passenger side seat will be mounted on the floor (about 1.5 inches lower than the driver side). This will help provide enough room for a taller passenger. The seat belts rear attach point will be very close to the the back of the seat and the seat belt attach point will be mounted 1/2 inch below the top of my HANS device. If I were not wearing it I think that the seat belt attach point would be either about shoulder height or slightly higher. I am expecting to wear it except sometimes for autocross type events.

There is enough space between the braces in the trunk to mount the 8 gal ATL fuel cell. The fuel cell will be mounted so that the bottom of it is 6 1/2 inches higher than the ground. The target is 6 inches higher than the ground but I may yet lower the rear of the car another 1/2 inch (allowing for that). It would be possible to adjust the height later if I need to change it but it would be inconvenient to do it.

Although the door bars are near my arm (if you assume that the padding is installed), the most limiting thing in the way of my arm is the side of the seat (where it wraps around your body). This would be the case with any racing seat so I think that the door bar is fine. The only thing that would improve this would be to make the steering wheel even smaller and shorten the steering column (already reduced it a little). The steering wheel is slightly close. I plan on modifying it at a later time and at the same time install a removable steering wheel.

I have not decide yet how to paint the tubing. I was thinking of painting all of it body color unless I decide to make the highest parts black or medium blue (like the Microsoft Windows blue).

I still did not find a pre-fabricated headrest. I think that I am going to have to buy the sanctioned padding material and then make my own.

The harnesses are 6 point safety solutions with a twist release lock. I am still researching the standards for installing it but it appears that it is ok for the two rear attach points to be closer together to each other (such as even 3 inches appart) so that the straps don't slip off the HANS device. Also, it appears to be ok if it is very slightly lower than the shoulders (should not be higher or too low). Originally I was aiming for equal but I wanted to make sure that it was not too high if the HANS device was not on (such as for autocross or something that does not need HANS).

Do they really require a rollbar inspection hole rather than using a scaning device to measure the thickness of the metal? If I drill a hole then moisture can get in (I suppose I can put in a rubber plug that will keep it pretty dry).

I am estimating that I am adding between 140 and 150 lbs to this car (including the fuel cell). However, I have removed close to that if you start from the way the car was stock. There is probably another 30-50 lbs of stuff left to remove if I decide to do it. I am not trying to make the car weigh as little as a competitive Midget (those cars weight 1420 lbs). My car weighed about 1440 lbs before the roll bar construction started.

I should have some pictures in a week or so (before it is painted so it won't be pretty).

Rebecca

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StephanAlfa
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Re: how hard should I try to fabricate with two equal seats

Post by StephanAlfa » Wed Jul 13, 2011 8:17 am

Not sure if this helps but in the case of the Alfa there IS a right side seat and a left side seat... Italians and Brits making cars are equally complicated to make sure if you make seats they actually fit on either side.
When I installed a race seat on my car I was lucky to find one that would a) fit on the same rails/frame as the original Alfa seat and b) did not have to mess with left or right side althought real estate was quite tight adding roll bar etc.

If you have original rail and frame, this is where I got mine from:
http://bomzracing.com/racingseatsnew.aspx
If you have to custom your race seat then I sugest our good friends at Driver Supply
Stephan de Pénasse - Classroom Instructor - http://www.comscc.org
2001 BMW 330i Sports Package (T-60 Class)

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