333pg333

Just getting to the end of the cage part of the project and I am wondering on the effects of the Gusset that I see in many cages. Not in all of course. Seems to me that the Gusset on the 'X' door bars is to assist in reinforcing during a rollover when the stresses go downwards through the cage (or is that upwards when you're on the roof). My instincts are saying that the 'X' bar is there to protect from side impact so I can't see that these Gussets are a whole lot of value in this situation, but I'm no expert so that's why I'm asking the question.

We also decided not to go back too far in the interests of keeping plenty of crumple zone. The cage has gone into the engine bay and the seat is off it's runners and they made fabricated some box tubes which are built into the chassis floor to bolt the seat to. Position is further back and lower for better c.o.g. and overhead clearance. Swapping to a non sunroof roof has helped a lot in both those depts also. Tilton pedal box has been mounted further back to match new seating position. Engine bay to get 'stitched up' once motor out.

A few pics so far.

67King

Going through this, now. I would speculate, but it is only speculation, that gussets on X braces are for fatigue relief. You are really prone to fatigue failure when you have sharp angles, which act like cracks. I doubt they help with in the event of a crash. Gussets on other sections, such as tying into the body will help improve rigidity. I'll be adding gussets to tie into my body in the front part of the roof and the B-pillar. I'll try to post up some pictues later.

DanR

looks a nice cage Patrick, you may struggle to use a halo seat (if you wanted) with the extra A pillar bar. I was going to have one of those in my last 44 but decided against it a it litterlally left 3 inches to get out

333pg333

I'll bring this up with the builder. Yes, post pics.

Thanks Dan. I actually was just looking on the site that you got your cage from and there are some pics of the 951 on there. Very stout cage in your last car for sure. I won't be going for a Halo. As you point out they make access very difficult, plus my car will still spend a very limited time on the street. (To and from Track + Workshop). I had a halo some years ago and got rid of it after a week. It was dangerous on the street. No vision in certain angles.

Gator_86_951

I am in agreement with 67king's speculation, with the understanding that my engineering background is computer and not mechanical. Seems the gussets are a backup. They won't "fix" or prevent failure otherwise because they are going to bend/fail otherwise.

67King

My cage is a bit more simple than yours, and in these pictures, it is still incomplete. I'll post up more when it is finished up, but that is probably a couple of weeks away. The first picture around the roof. I'll be adding a gusset tying the bar to the roof. It will go from the bar to the reinforcement sheetmetal just ahead of it (closest to the windshield). The second picture is around the B-pillar. It will be gussetted from roof to floor, front and back to box it all in. The fabricator likes to gusset the A-pillar, too, but that requires windshield removal. If I eventually get to that point (probably more like when), I will add gussets at that point in time.

dand86951

Patrick, Gussets in the x would in my opinion help in a side impact, however is it strictly required, I can't say. I would suggest strongly that you get into your seat and make sure your right elbow is not going to be hitting the x bar anywhere while you are in the driving position.

ace996

the gussetts are supposed to help keep the cage together on impact, spreading the forces to other parts on the bars where they are not joined/welded. If you can distribute the "shearing" forces over a larger area of the "X", then it should help keep the "X" together...if that makes any sense. I'd hate to be in a car that's been t-boned and have one of the door bars separate at the welds in the center of the "X" and then become a pointed weapon.
Be good,
TomK

Greg Smith

I would do taco gussets on the top and bottom of the door X bar. You have a weak spot in the middle because you've really only got 1 tube in the middle(although it satisfies most rule books as 2 tubes) and it's surrounded with a heat affected zone on top and on bottom. So if it fails it's very likely it'll fail there.

spare tire

Gussets help a couple of ways. The Taco gussets of a cup car are areally good idea. A tube has a certain strength depending on its diameter and wall thickness. The other factor is the length of the tube that tube that butts into another tube 21" away has an ability to withstand a certain amount of force.

If a gusset laps 4" in from a connection, then the tube will be stronger as the span is 17" now. And that is if a gusset is only on one end of the tube. The other thing that makes gussets so strong is the shear plain is in two different locations. The heavy hit shown above sheared the connection of the tubes. When you gusset, first you weld in the tubes fully. Then you weld in the gussets
and the first tube welds are covered by material that can bend and deform and stretch. Welds are strong but more brittle than tube.

Oddjob

Do you know specs of the broken cage in the picture? Diameter, wall thickness or material (DOM or 4130)?

333pg333

We'll be putting some gussets in on the door bars at least. Although we have no idea of the specs on that Blue Miata shown in the pics, it's enough to convince me that it's a good idea.

Window net went in yesterday. I take it we should have one in the middle also.

Greg Smith

Nope.

kurt M

Have you tested the seat yet? Based on the pictures you just posted the door X looks set a bit high. that and the front bar might combine to make getting out in a hurry a tough one.

333pg333

Well I've sat in it but the car was a foot or two in the air on the hoist so a bit hard to tell. Ingress and egress wasn't easy in that position. I'll just have to deal with it. Heck some guys have their doors welded shut.