Cage building: Plates and touching

[fairgentleman Z]

So we are building our first cage and wanted to clarify a couple things.

The two front roll hoops are currently touching the a-pillar/roof at the top, without the plates installed yet. So we definitely need to some cutting to get plates under there. Our goal is to get them as close as possible. Advice on how close is to close (I remember a post showing a jacking point that allowed a piece of paper to slide through). Our method is to wedge wood between the chassis and bar and then weld, hoping the gap will remain after the wedge is removed.

Mounting plates, do they HAVE to be one continuous piece? I want to get three planes for the main bar, but to fit the contours of the floor better it would be easier to do it as two pieces. The resulting plate will be under the 100 sq in.

Dash bar, since it is not a required element am I correct to say if we elect to install one it can have a smaller wall thickness?


Originally posted by GCR 18.2..1.5.E
One (1) bar is recommended in a horizontal plane between forward cage braces in the dash area.

Thanks,
Jeremy

[lateapex911]

Im my opinion, touch all you want...just don't attach. I made my certer tubes bigger than needed, or my tubes a bit long, and hammered into place to spread my bars into the chassis wherever I could. I think the operating definition of "attach" is to physically join at that point, via welding or mechanical fasteners.

My understanding of the rule is that all non required elements may be constructed of elements that don't meet the sizing requirements of the required parts...errr..long way of saying"Yes". I see this as more useful in making triangulated gussets and so on.

I have seen many, and am in agreement that multi plane plates may be fabricated from multiple components. Welding is the method to do so, and I have a few of those on my car.

The good book encourages you to mount to vertical sections or rocker boxes when practical, but also uses the "floor" word. So my front plates start on the floor, climb the rocker and then lap over onto the top of the rocker, with the tube being welded to the mostly vertical surface. Tech liked them.

[Speed Raycer]

Jeremy,

You're right on target. IMO, the closer you can keep the downbars to the A pillar and the A pillar/roof joint, the better. Same with the hoop. The example of the jacking pad is a completely different topic than bars TOUCHING the body.

My suggestion would be to fit everything up first before welding anything solid. The one big downfall of tight fitting cages is that you may build yourself into a spot where you just can't get in to weld the doorbar joints or hoop joints. IT's a little more work and takes a little longer to prebuild rather than weld as you go, but it's worth it.

[lateapex911]

Yup, good points on the welding. You really need to think it thru in advance because you can build yourself into a bind if you don't! I did mine witht he glass out, and used a hole saw to open two holes in the roof to get to the top of a couple joints. Easy weld back in with the kerf from the holesaw.

[joeg]

All good advice.

I have plates made both ways--with a bender and a welder.

My plate bending tool is kind of neat (and real simple) but you would not want to get crazy with it. For a complex plate--one going in different directions at different angles--mock it up in cardboard pieces(with tape).

You can even mock up the tube attaching to it with the cardboard tube remaining at the end of a roll of paper towels.

Have fun.

[latebrake]

I read somewhere that SCCA allowed you to (tab) the cage. Weld the tubing to the body. You cant cross great gaps with it but seen it done. Seen pictures of this too but dont remember where as it was a long time ago. The GCR addresses this I am told. Lots of this on the prod site some time ago. Is this a prod allowed thing only or is it a NASA allowed cage build? I know,I should look it up,i'm not,i'm not building a cage I just bought it up as a heads up for anyone who is. I know I wasent dreaming :birra: just cant bring up the info right now.

Lawrence

[Greg Gauper]

'Tabbing' is permitted in Production & GT classes. It is not permitted in IT. A tab becomes another attachment point. You are permitted a maximum of 6 points in IT with two additional optional mount points to the firewall. A tab is another attachment point.

But you can make the cage an interference fit! The hot set up seems to be to cut holes in the floor to drop the cage down to provide access for welding to the top joints, then wedge the cage up and cover the holes with your mounting plates. The 'jacking' point idea is, IMHO a very clever yet legal interpretation of the rules. It 'touches' but is not attached.

After I converted my IT car to Prod, I (legally) added tabs to to tie the 'A' and 'B' pillars to the cage. It made a world of difference to the chassis stiffness!

[latebrake]

'Tabbing' is permitted in Production & GT classes. It is not permitted in IT. A tab becomes another attachment point. You are permitted a maximum of 6 points in IT with two additional optional mount points to the firewall. A tab is another attachment point.

But you can make the cage an interference fit! The hot set up seems to be to cut holes in the floor to drop the cage down to provide access for welding to the top joints, then wedge the cage up and cover the holes with your mounting plates. The 'jacking' point idea is, IMHO a very clever yet legal interpretation of the rules. It 'touches' but is not attached.

After I converted my IT car to Prod, I (legally) added tabs to to tie the 'A' and 'B' pillars to the cage. It made a world of difference to the chassis stiffness!
[/b]

Thanks Greg, clears me up on taps in IT.

Lawrence