4 replies to this topic

[ozz1]

To me the most straight forward way of making a miglia bulkhead is to remove the bulkhead and weld a sheet of steel to the top and lower dash rails from the inside of the car, however I have never seen this done...is there a reason for this?

 

Thanks

Edited by ozz1, 11 May 2017 - 01:07 PM.

[tiger99]

If it is for normal mileage road use, yes there is a very good reason. It will suffer fatigue fractures after a while, and as it is the most highly stressed area of the shell, and essential for driver protection, the consequences of a structural collapse could be very bad. The loss of vital stiffness in the bulkhead decreases shell torsional stiffness and degrades the handling. And, too much stiffness in the lower dash rail and parcel shelf is very dangerous to the front passenger, which is why in about the 1980s large parts of the steel parcel shelf were cut away. Mess with safety-related structure at your peril.

 

In general, things that are intended only for the very low total mileage accumulated on the track are unsafe and illegal on the road. Changing parts of the monocoque like that also requires that the car is subjected to an IVA test, which it will fail.

 

What can be done for competition use only is determined by the rules of your particular governing body.

[ozz1]

If it is for normal mileage road use, yes there is a very good reason. It will suffer fatigue fractures after a while, and as it is the most highly stressed area of the shell, and essential for driver protection, the consequences of a structural collapse could be very bad. The loss of vital stiffness in the bulkhead decreases shell torsional stiffness and degrades the handling. And, too much stiffness in the lower dash rail and parcel shelf is very dangerous to the front passenger, which is why in about the 1980s large parts of the steel parcel shelf were cut away. Mess with safety-related structure at your peril.

 

In general, things that are intended only for the very low total mileage accumulated on the track are unsafe and illegal on the road. Changing parts of the monocoque like that also requires that the car is subjected to an IVA test, which it will fail.

 

What can be done for competition use only is determined by the rules of your particular governing body.

Didn't know that was the reason for the solid parcel shelf in mk1 vs one full of holes in the mk3! Would be for a track car that's already been mucked about with...think I'll stick with the standard Weber box though.

[tiger99]

There is an additional complication because a MK 1 has sliding window doors with external hinges and a very different structure around the A pillar area, whereas a MK 3 has internal hinges. The stress distribution will be different, and that may also affect the design of the shelf. Just in case anyone thinks of putting a later shelf in a MK 1! I suppose you could always weld up the holes...

[waddle]

iv got to do mine soon, I am  thinking to take the turrets to the dash bar  and then panel on top