Today we are talking about... chassis specifications

[MARK1]

Oh,

The link works best without the comma........

[catears]

If you are making a custom chassis with a cnc cutter, you can always go this route: http://www.metalsdepot.com/products/alu ... 20&aident=

You can get several chassis out of 12 feet at around 20 bucks a foot raw material. If you put the time in, you can design something unique and have an indestructible chassis going with channeled aluminum. Depending on how big the machine is, you could cut all the chassis on one hit per dimension. Only draw back is the sides would be open, but you can cut a piece of aluminum to fit.

[roberto]

Thank you all.

On a mechanical-stress point of view I see no problem with 0,63" - 1,5 mm alluminium.

On an electrical point of view there are some preferencies? Aluminium should auto-passivate, so form a thin oxide layer that protect the metal from further ozidation. So when I ground potentiometers ther are in contact with this layer. Is there any difference? (conducibility shown is for the metal alloy, not for its oxide).

Anyway, Aluminium resistivity is more than 5 times less than AISI304 that is ok for me, so there should be no problems.

And for thin chassis I should have no problem of skin effects too:
http://www.engineerplant.it/tab_effetto_pelle.htm

(sorry for the Italian link. Oro is gold, argento is silver, rame is cuprum, alluminio is obviously alluminio, ferro is iron and ottone is brass).

[martin manning]

On a mechanical-stress point of view I see no problem with 0,63" - 1,5 mm alluminium.).

That's too thin to adequately support heavy transformers. I would use 0.090" (2.3mm) minimum.

On an electrical point of view there are some preferencies? Aluminium should auto-passivate, so form a thin oxide layer that protect the metal from further ozidation. So when I ground potentiometers ther are in contact with this layer. Is there any difference? (conducibility shown is for the metal alloy, not for its oxide).

In my oppinion its best to use a ground lug to connect to the chassis and not rely on the pot bushings (so don't solder to the pot case for a ground). I have not had an issue with the pot case itself being grounded via its bushing.

[roberto]

Really 2,3 mm? IIRC old Marshalls have 1,6 mm chassis.

It will loose the weight convenience, because it will weight 1,6 kg instead of 2 kg circa (2700 kg/m3 for alluminium, 7800 kg/m3 for stainless steel, but with a width of 2,3 mm the weight for specific area of the sheet of metal is only 20% less than 304).

The only pro is that aluminium is easier to be drilled if necessary.

[guitardude57]

Seems I've read on different posts, that the 5052 type bends
somewhat smoother without cracking.

1mm is probably great for many chassis, but I would imagine
that something closer to 2mm or slightly bigger, (.90-.125) for
those amps with the real heavy trannies, would insure against deformity from the weight.

A guy could have his head accidentally take a fall. The tranny deforms the chassis from the impact. I have seen power trannies tore off from chassis from a short drop.

One good thing about steel.
Everything stays together except for some tubes...