Roll cage advice
#16
Racer
Thread Starter
Join Date: Mar 2005
Location: Park City, UT
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by earlyapex
Here are pictures of my cage. The current version goes to each shock tower and may not be legal for your class. I have enclosed a picture of the old roll bar that shows where it is welded to the rear bulk head are.
You can look some other examples of cages and bars on Tony's web site.
http://tcdesignfab.com/porscheprojects.html
You can look some other examples of cages and bars on Tony's web site.
http://tcdesignfab.com/porscheprojects.html
A lot of the pictures in the pdf came from the tcdesignfab web page.
Cheers,
Jeff
#17
Drifting
Do a search and you will find a couple good discussions about cage design - one with some FEA analysis that is pretty good. Also, are you running full steel doors? Keep in mind if you are going to gut your doors with NASA then you need door bars that protrude into the gutted door such as NASCAR style door bars or the pyramid based bars such as the 997 Cup cars have. I personally like the pyramid cross bars with the taco gusset as in the Cup cars.
#18
Racer
Thread Starter
Join Date: Mar 2005
Location: Park City, UT
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
Hi Skip - doors will remain steel and will not be gutted. I will use RSA style door panels.
"pyramid based bars" - do you mean the X bars with gussets where they cross?
"pyramid based bars" - do you mean the X bars with gussets where they cross?
#19
Race Director
Originally Posted by jaydubya
Not sure that I follow you? My understanding is that the diagonal and the cross bar for the seat belts must be in the same plane for SCCA/NASA. This is illustrated on Page 3 of the pdf.
Originally Posted by jaydubya
By the last set, I assume you mean the last page of the pdf?
Which "first set of door bars" do you mean?
Hmm, I thought it was a fairly strong design with easy access. The alternative is a straight "X". Compared with that design, I don't see the shortcomings of the curved bars with the gusseted reinforcement... Could you elaborate?
Which "first set of door bars" do you mean?
Hmm, I thought it was a fairly strong design with easy access. The alternative is a straight "X". Compared with that design, I don't see the shortcomings of the curved bars with the gusseted reinforcement... Could you elaborate?
The "first set of door bars" where the first ones fully shown in the pdf document.
#20
Race Director
Originally Posted by jaydubya
"pyramid based bars" - do you mean the X bars with gussets where they cross?
#21
Cows-4-Rent
Rennlist Member
Rennlist Member
They are primarily a BMW shop they work on a couple of 996/997 cup cars but will build cages for the plebs like us old 911/944 guys too. I haven't received my quote for the S2 but I'm hoping they go easy on me b/c I have never seen such nice work. The cages are finished to a level that matches exterior paint, welds are all 360* and perfect. They gave me great advice on bar placement/how/why/what each bar does. Got a good lessen on energy dissipation.
The owner runs the Rolex series
The owner runs the Rolex series
#22
Racer
Thread Starter
Join Date: Mar 2005
Location: Park City, UT
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Geo
What I mean is that the main hoop is being shown attaching about 3-4" in front of the plane of the front of the rear seat. Where the floor pan stops and the sheet metal rises about a foot to form the front of the rear seat. I'd attach (I did on my cage) the main hoop in this same plane (move the attachment back about 3-4" from what is being shown).
Originally Posted by Geo
Yes, I meant the last set from the pdf. Easy access should be low on your list. Strength and stiffness should be high on your list. When you bend tubes you make them weaker. Sure they are reinforced, but I'd personally (again, I did) go with straight tubes in the X or NASCAR bars.
#23
Rennlist Member
Here is Mark McMahan's site: http://www.rollcageguy.com/
He does Nonamakers and some other Rolex cars...Just had him do a cage for the 944 and it is perfecto! There are some decent 911 cage pics there.
He does Nonamakers and some other Rolex cars...Just had him do a cage for the 944 and it is perfecto! There are some decent 911 cage pics there.
#25
Racer
Thread Starter
Join Date: Mar 2005
Location: Park City, UT
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
Any advice for tubing diameter and thickness? The shop is suggesting 1.75" diameter by 0.095" thick, which seems to meet requirements for PCA, SCCA, etc.
#26
Race Director
Originally Posted by jaydubya
Any advice for tubing diameter and thickness? The shop is suggesting 1.75" diameter by 0.095" thick, which seems to meet requirements for PCA, SCCA, etc.
#27
Rennlist Member
If you are going to have steel doors with door bars still in tact, just flat X across door opening. Not pyramid one (which probably would not fit). It's strongest and lightest. Like Earlyapexes.
#29
Race Car
i don't like the "knee bar" in any cage. it's way too low and is a potential threat to your lower body. in my BMW 325 (and most BMW racecars I've seen including the ones at tcdesignfab.com) the knee bar is replaced by a dash bar going behind the dash. i mounted this successfully in my car but i don't know how it would work in a 911
lighter by how much and stronger by what definition? i have 1.5" by 0.120" and i think with proper cage design and gusseting, "stronger" is a relative term
Originally Posted by Geo
That's stronger and lighter than 1.5 x 0.120". However, you cannot make quite as tight a bend with it either (r=5.25" vs. r=4.5"). Like most things there are trade-offs.
#30
Mr. Excitement
Rennlist Member
Rennlist Member
1.50 X 0.95 is 1.426 per foot. 114 pounds per 80 feet
1.75 X.095 is 1.679 per foot. 134 pounds per 80 feet
1.50 X .120 is 1.769 per foot. 141 pounds per 80 feet
1.75 X.120 is 2.089 per foot. 167 pounds per 80 feet
i like to think in 80 foot batches as this makes the real weight savings or weight cost more relatable.
The thought is that 1.75 X .095 dia tubing is stronger pound per pound than 1.5 X .120 is in the fact that it has a larger cross section and is a geometrically better shape. If space is not a factor and you have to use 1.5 X .120 or better then 1.75 X.095 might be used to make a slightly lighter cage that will be slightly stronger too, all other things being the same. As you see the weight delta between 1.5X.120 and 1.75X.095 in an 80 foot batch is only 7 pounds.
1.75 X.095 is 1.679 per foot. 134 pounds per 80 feet
1.50 X .120 is 1.769 per foot. 141 pounds per 80 feet
1.75 X.120 is 2.089 per foot. 167 pounds per 80 feet
i like to think in 80 foot batches as this makes the real weight savings or weight cost more relatable.
The thought is that 1.75 X .095 dia tubing is stronger pound per pound than 1.5 X .120 is in the fact that it has a larger cross section and is a geometrically better shape. If space is not a factor and you have to use 1.5 X .120 or better then 1.75 X.095 might be used to make a slightly lighter cage that will be slightly stronger too, all other things being the same. As you see the weight delta between 1.5X.120 and 1.75X.095 in an 80 foot batch is only 7 pounds.