Stainless Vs. Aluminum

[RockNRollDr]

What is the difference in using stainless steel instead aluminum for the chassis of an Express? Does it have something to do with interference or do people use aluminum because its what Ken used?

[UR12]

It has to do more with aluminum being a good conductor and having no magnetic properties. Aluminum is usually compared to steel which has iron in it and can become magnetized. Stainless has nickle in it and the nickle changes the magnetic properties of the alloy. Stainless is very hard and makes it more dificult to work with when it comes to drilling and punching holes.

[Structo]

Also isn't aluminum better for heat transfer than steel?

[lastwinj]

cost as well. stainless is wicked expensive, especially the non magnetic stuff.


germ

[CaseyJones]

What is the difference in using stainless steel instead aluminum for the chassis of an Express? Does it have something to do with interference or do people use aluminum because its what Ken used?

IMHO the biggest differnce between stainless and aluminum is that stainless can be a bastard to work with. There is a mind boggling array of alloys available ranging from the food grade alloys through the harder than the hinges of Hell material intended for knife forgings. The thing that most stainless alloys have in common is that they're harder to machine than regular old high ferrous content steel or (non ferrous, they don't make it any other way!) aluminum. Aluminum... almost any alloy of aluminum... carves like soap. High nickel stainless also carves like soap... wet soap! Only with much greater effort. There are "free cut" stainless alloys intended to be easily machined, otherwise the material galls and smears rather than cutting.

Mr. Fischer used a Bud box in a 17" wide size that's no longer available. If you use a similar Hammond box in aluminum you'll find that it's easy to drill and punch but the material, 22 guage 6061 I think... is far to flimsy to be gig-worthy with heavy transformers mounted to it. Ken thought of that, he used a wooden dowel near the PT to keep the chassis from deforming from the weight of the transformers.

The Hammond chassis is spot welded, that's good enough if you use it like it's intended... as a stationary housing for lightweight solid state circuits. Hang some beefy transformers from it and take it on the road, you'll find its limits pretty quickly.

Final answer: Send Allyn some dough and save yourself the aggravation, dude!

[nickt]

What is the difference in using stainless steel instead aluminum for the chassis of an Express? Does it have something to do with interference or do people use aluminum because its what Ken used?

R&RDR - just reading between the lines - are you thinking of stainless for asthetic purposes? I think the Komet folks have gone with painted steel - the important thing being that the Mojo around aluminum didn't matter - but (as usual) I could be mistaken. However if this is the case you could use a steel chassis and get it chromed for the "holy crap! that's beautiful" effect.

Yeah I'm assuming alot

Hope it helps

[mhuss]

Stainless is a lot heavier than aluminum as well. Not that the express is a heavyweight to begin with.

--mark

[geetarpicker]

For what it's worth I'll chime in. My original '89 Trainwreck Express has never shown any issues from the thin chassis giving in with hundreds of gigs played and alot of travel, some in a road case and some not. On an original Express there are actually two wooden dowels. One ties the two transformers together, and is simply siliconed in place. The other has a hole drilled through it and is basically sandwiched between the bottom plate and the top of the chassis. To simplify installing the bottom that dowel it is glued to the inside of the chassis on one side. Since the bottom plate is screwed on with a ton of screws, once the bottom is installed and the top to bottom dowel screw installed it's more solid than you would think.

Heck when I built my pair of "dead on" clones I even sought out a couple of original BUD .050 thick chassis.

Still, most everybody believes that the chassis thickness has nothing do with the tone but the aluminum material (over steel or other?) probably does. So, a thicker chassis of aluminum is stronger and probably gives the same tonal qualities. Most folks build these amps on aluminum of a thicker variety than the original .050 thick BUD boxes. I'll still probably always be thought as "crazy" to think that even the thickness of the aluminum may even play a small part in these amps tone and response.
If it's true it might even have been a lucky accident. I'm pretty positive Ken used the chassis because they were cheap and available. However Ken really liked JTM45s and other originals of those have very thin chassis too. With those there tends to be problems, as most have no extra reinforcement.

That said, I just got lucky yesterday and found another original BUD 17x8x2 chassis on Ebay for $20... Not that I plan to build any more amps, but just in case I need the parts someday...

[FUCHSAUDIO]

Stainless wears out the dies used to punch the material "at least ten times faster" than similar dies used for steel or aluminum.

If you plan to maintain a pretty finish, you have to use the stainless coated in a plastic film (which is peeled off after punching), which means they must be very careful in the metal shop. Very few people use it for chassis, as the cost of material and cost of handling and making the chassis just too expensive. Sonics ? I doubt it sounds any better or worse than aluminum, as it's non-ferrous (magnetic) as well. Pretty yes, practical no.

BTW: if you use acceptable thickness aluminum, or reinforce where needed, there are no strength issues. We're using .092 for everything these days, without incident.

[drhulsey]

... especially the non magnetic stuff...

What is it about stainless steel that makes it non-magnetic- lower iron content I have a SS table that I was disappointed to find would not attract a magnet
Metallurgy is, among many other things, not my strong point

[Structo]

I believe the high nickel content in stainless makes it non magnetic.

[RockNRollDr]

Thank you everybody for your help, and Glen I just got your CD in the mail Saturday. Great Work, the tone is incredible, it's in my computer right now at work.

[Lonely Raven]

Thank you everybody for your help, and Glen I just got your CD in the mail Saturday. Great Work, the tone is incredible, it's in my computer right now at work.

That reminds me that I need to put Glen's CD on my new MP3 player I got for X-mas.

[novosibir]

If you plan to maintain a pretty finish, you have to use the stainless coated in a plastic film (which is peeled off after punching), which means they must be very careful in the metal shop. Very few people use it for chassis, as the cost of material and cost of handling and making the chassis just too expensive.

I'm one of the few, using stainless steel chassis:

[img:800:533]http://www.larry-amplification.de/dino9 ... 077-01.jpg[/img]

They've been coated with plasic film and are laser cutted, bended & welded, before the metal shop removes the film. And yes, they are expensive - here in Germany I pay 145 EUR for each, what's about 205...210 US$

Still before I've switched to regulated DC for the preamp heaters I've switched from regular steel to the stainless steel chassis back in 1995 - and I've noticed, that my amps with the stainless steel chassis have had a remarkable lower background hum, which before especially was present in the high gain channel. So I assume, that the reduction in hum was caused by the fact, that the stainless steel doesn't lead magnetic fields from the PT to the more sensitive areas of the amp, while the regular steel did.

After switching to regulated DC heaters in 1997 the remaining hum disappeared entirely.

Larry

[Lonely Raven]

Wow that's some sexy SS!

Interesting thought about how the chassis would flatten the magnetic field. Makes sense though.