Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Bub on November 02, 2010, 09:39:31 pm

Title: Galvanized chassis
Post by: Bub on November 02, 2010, 09:39:31 pm: Hi Gent's,

Is there any reason not to use galvanized steel when building a chassis.

Thanks

Rob
Title: Re: Galvanized chassis
Post by: dynaman1 on November 02, 2010, 09:56:57 pm: Not that I know of, but I'd grind to untreated bare metal for your ground and earth connections.
Title: Re: Galvanized chassis
Post by: Bub on November 02, 2010, 10:05:42 pm: Thanks dynaman 1,

Great tip. I would have never thought of that.

Rob
Title: Re: Galvanized chassis
Post by: eleventeen on November 03, 2010, 12:34:34 am: Ummm, there are several different types of galvanized. There is "hot dip", which will leave a much thicker layer of galv metal on the steel, often with small inclusions and irregularities in it which could cause problems if you need to achieve a nice finish somewhere. I'm not sure what the other types of galvanized are called, if anything. Other than what I said in the first sentence, I don't see any electrical reason why it would be a problem.

And also, there is the issue of whether the raw sheet metal was galv'ed and then bent, or, the already-bent chassis was galv'ed. I could see galvanizing flake off if it was raw (flat) sheet steel that was later bent around a curve.
Title: Re: Galvanized chassis
Post by: Bub on November 03, 2010, 12:49:36 am: I think I'll skip the galvanized and buy a plain sheet. A friend of mine has a skid of 18 ga galvanized sheet so free was better but I only have one chance to build the chassis.

Thanks

Rob
Title: Re: Galvanized chassis
Post by: kagliostro on November 03, 2010, 05:11:57 am: Galvanized chassis

galvanized with which metal ?

Kagliostro
Title: Re: Galvanized chassis
Post by: supro66 on November 03, 2010, 05:32:38 am: I built my first one that way
Homedepot heating duct and angles

(http://i282.photobucket.com/albums/kk243/supro66/Supro%20Amps/red2.jpg)

(http://i282.photobucket.com/albums/kk243/supro66/Supro%20Amps/redneck2.jpg)

(http://i282.photobucket.com/albums/kk243/supro66/Supro%20Amps/suproguts.jpg)

Doug sells the lugs drill hole attack a lug and you have a good solder point

Then I used leather contact paper

YES ALL SUPRO'S HAD THREE PIECES OF WOOD IN THEM

(http://i282.photobucket.com/albums/kk243/supro66/Supro%20Amps/leather2.jpg)

It plays well
Title: Re: Galvanized chassis
Post by: stingray_65 on November 03, 2010, 06:57:01 am: Quote from: kagliostro on November 03, 2010, 05:11:57 am
Galvanized chassis

galvanized with which metal ?

Kagliostro

Zinc

Galvanized steel is for use outdoors or where corrosion would be a problem. the zinc oxidizes and creates an inert, protective layer.

Galvanized sheet metal is designed to be bent on a brake without flaking. you should however increase the bend radius by 50% to avoid the flaking. So if for example your 18ga material. cold rolled 18ga sheet would have a bend radius of 3/64" your galvanized 18 ga would be about 5/64" (a little more than 1/16).

(Bend radius is measured inside the bend)

The issue with Galvanized steel is cosmetic, Paint does not stick well to it, even paint designed for it. The protective layer I mentioned before will form and paint will peel. Left raw it forms a mottled chalky grey color.

Dyna is correct in suggesting to get to the base material on ground points. Grinding sounds excessive, 100 grit sand paper and some firm thumb pressure will get you there quickly. You will see it clearly when you get there.

IF you decide to tack weld corners, be aware that the gasses given off are hazardous.

Ray