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Mats · Post by **Mats** » Fri Mar 17, 2006 2:42 am

Yeah, FEM is like statistics, you can make anything look good..

Designing to Rp 0.2 works until you come unstuck.

Suddenly all the forces are not transmitted through the wheels and you are in big trouble.

la_strega_nera · Post by **la_strega_nera** » Fri Mar 17, 2006 3:21 am

Mats wrote:Yeah, FEM is like statistics, you can make anything look good..

Designing to Rp 0.2 works until you come unstuck.
Suddenly all the forces are not transmitted through the wheels and you are in big trouble.

Not quite following how the loads wind up not being transmitted through the wheels?

Or are you talking about when you punch an alfetta shaped hole in the scenery?

Mats · Post by **Mats** » Fri Mar 17, 2006 3:30 am

Yeah...

Unstuck - as opposed to stuck on the black stuff.

zambon · Post by **zambon** » Tue May 09, 2006 5:02 am

I know that rules are different everywhere, but has anyone heard of rules that require TIG welds on cage work?
Also, I was told by an unreliable source that mandrel bends are a requirement for the main hoop for SCCA rules (USA).
Can anyone confirm or deny?

Mats · Post by **Mats** » Tue May 09, 2006 5:26 am

Never heard about TIG rules, maybe related to CrMo-cages that are popular in the fraction mile crowd?

Here in Sweden we don't have a mandrel bend demand but the pipes must be cold drawn seamless pipes and the difference in diameter in the bent (compared to an undeformed pipe) part must be lower then a certain percentage.

Not sure if that helps though.

zambon · Post by **zambon** » Wed May 10, 2006 10:43 am

Thanks for the reply Mats
I finally got the scca rules pdf to work.
6. Material:
A. Seamless, or DOM (Drawn Over Mandrel) mild steel tubing
(SAE 1010, 1020, 1025) or equivalent, or alloy steel tubing
(SAE, 4130) shall be used for all roll cage structures. Proof
of use of alloy steel is the responsibility of the entrant.

I think this is where the bs about mandrel bends came from.

All welds shall be visually inspected and shall be acceptable
if the following conditions are satisfied:
1. The weld shall have no cracks.
2. Thorough fusion shall exist between weld metal and
base metal.
3. All craters shall be filled to the cross section of the
weld.
4. Undercut shall be no more than 0.01 inch deep.
C. Aluminum bronze or silicon bronze welding technique is
permitted, but extreme care shall be used in preparation of
parts before bronze welding and in the design of the attaching
joints.

Seems that they only require the welds to look good, nothing more. I dont understand the parts that are in bold, however. Craters? Undercut?
Can anyone explain?
Thanks
James

MD · Post by MD » Sat Mar 31, 2007 4:24 am

A little while back we were debating the merrits of bracing techniques in the engine bay. Here's some photos of a strong set up for an old banger Ford Fairlane 500.

Note the triangulation from suspension turrets back to the firewall. If you had the room, (and clearly on the 4 cylinder Alfas I am sure you do) you could also add a bar across the top of the engine to fully triangulate.

What a tough set up? !! Sometimes it pays to look back. A lot of the time its has all been done before...

x-rad · Post by **x-rad** » Sat Mar 31, 2007 6:28 am

You can't ignore the merits of triangulation, but your triangle can't act like a hinge, either, in response to a force applied perpendicular to the plane of the triangle. In the Fairlane, the majority of strut force is perpendicular to the brace triangle. In this case, the triangle acts more as a front fender brace(to the limits of flexion at the flat metal around the strut mount bolts).

I am not saying that the brace does not do anything(I noticed the crack in my windshield got MUCH bigger after a simple strut cross brace), just that the majority of the strut force is shared by the inner wheel well sheetmetal. The Fairlane brace does make the front box much stronger in case of impact.

Tying strut mounts with a cross brace does have some benefits based on the angle of the strut. But the flex in the brace limits the effectivness. Tying a cross brace to the body with additional attachment points (bracing) in any plane but perpendicular to the strut will have more pronounced benefits (Which is what the wheel well sheet metal is trying to do, but with forces in many directions).

x-rad · Post by **x-rad** » Sat Mar 31, 2007 8:05 am

Zambon: check this out for some basics..

http://www.advanceautoparts.com/english ... 0301rb.asp

Maurizio · Post by **Maurizio** » Sat Mar 31, 2007 10:08 am

What a tough set up? !! Sometimes it pays to look back. A lot of the time its has all been done before...

@MD Since when is any American designed car able to go around corners!

I'm not convinced. The firewall is not the place to place forces into. In designing for stiffness you need to work only with pull/push tubes.
Firewall gets bending forces like you use it!

I would set it up like the red in the picture.
(see it as an example, this will not clear the pedal box)

Jim K · Post by **Jim K** » Sat Mar 31, 2007 11:53 am

Same kind of bracing was the norm for all Mustangs at least until 1971. Was this just a Ford thing?
Jim K.

la_strega_nera · Post by **la_strega_nera** » Mon Jul 30, 2007 2:09 am

The top of the firewall on the fords is actually a big box section that doubles as the fresh air Plennum (and the home of soooo much rust!), so triangulating like that actually works fairly well (certainly better than not even trying to triangulate!)

Maurizio · Post by **Maurizio** » Tue Aug 21, 2007 12:39 am

Came across some pics of a imsa replica.
Engine bay and the front nicely stiffened. I like what I see

Mats · Post by **Mats** » Tue Aug 21, 2007 1:43 am

Yeah, it's amazing what you can get away with when you have a dry sump...

Maurizio · Post by **Maurizio** » Tue Aug 21, 2007 3:30 am

Mats wrote:Yeah, it's amazing what you can get away with when you have a dry sump...

and the rest, this car was probably done with a nice budget....
I like the way they did hide the space frame front in the original inner fenders.