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Aluminum Chassis Question?

7/21/2000 8:18 PM
Aluminum Chassis Question?
Hi -  
Today I stopped by a local sheetmetal shop and inquired about their aluminum. This is what I found out. A 4 X 10' sheet of .090 aluminum costs $87.00 + tax (7%).  
I could take that home and do whatever I'm capable of doing and it would be plenty for me to mess with. Right now I'm interested in experimenting, prototyping, etc., so aluminum would seem to be the logical choice for the ease of constructing an amp. Also it would remind me of my ole high school electronics class (1965).  
However, I asked the owner to price out an 18" long by 10" wide by 2" deep box. Believe that's with welded corners - have to double check on that. Anyway, the price is $23 and change with tax. BTW, I have a set of punches for the sockets so just want blank chassis.  
I figure for a .090 that's not a bad price and I'd probably order at least two for now. The dimensions I gave the shop were just approximations, have to decide on the final dimensions before placing the order. Any popular dimensions for prototyping? Or the final product.  
I'd be making SE and P-P amps not to exceed 50 or so watts, whatever I can get from two tubes max. I do want plenty of room for flexible preamp stages, line in/out etc, a variety of switching arrangements, maybe switching from 9 pin to octal preamp tubes also.  
Does the price seem fair for what I described? All opinions are welcome.  
Thanks, take care, T.B.
7/21/2000 9:01 PM

Hey TB, I've just been through getting a chassis made so maybe I can give some ideas. First off, .090 is really overkill unless you've got some extremely heavy trannies and I doubt that with a 20-50W amp. Now, if you're planning on a SE design, you may want to go with that since the OT's are usually heavy (except the Hammond "universals").  
.080 is the heaviest I would go and really ~.060 is fine for most jobs. Unless you're going for multiple channels ala Fender, Dumble, etc. I would have a chassis made that's 17"X8"X3" and there's a lot of room for a single channel push-pull amp.  
Sounds like a decent price on the box and if you go down from .090 they'll probably come off the price some more.  
7/21/2000 9:23 PM

I did 16 guage steel (16 guage is about 0.060") 2x8x16, for $17, no ends, no welds.  
Welding aluminum isn't as easy as welding steel: $23 seems light.  
The 2" isn't deep enough. My 2cents.
7/22/2000 1:34 AM
Holger Notzel

Why wouldn't you use Hammond boxes? They are neatly made and come in all sizes for about the same price. Check Angela's web site. Hogy
7/22/2000 2:14 AM

I think the Hammond boxes are too thin. A friend of mine bought a steel chassis and we couldn't believe how flimsy it was. However, after he mounted the trannies and the board, etc., it stiffened up some.  
Also, I can get the local shop to build to suit. Not sure exactly what dimensions yet. I'll be using the chassis for prototyping initially. I will place an order for one Monday and see how it comes out. I wasn't able to get into details with the owner this morning as he was quite busy.  
I see Hoffman has a blank chassis similar to the one I described in my original post and he wants $60 for it.  
Thanks for all your replies thus far. Have a great weekend everyone! T.B.
7/22/2000 3:37 AM
Bryan James

I think the Hammond boxes are too thin. A friend of mine bought a steel chassis and we couldn't believe how flimsy it was. However, after he mounted the trannies and the board, etc., it stiffened up some.  
hmmmm haven't had this problem.  
i've been buying the 17x10x3 20ga steel chassis, and there nice and strudy. built my 1959 clone and november on them. personal i think 3inch height is to much, looking for aroun 2 1/2"  
7/23/2000 1:07 AM

I got one and built a 1987 clone,I think it was 16*8*2 and well yeah the 2 1/2 would be ideal cuz it was hard to tighten up parts with such lil clearance.I think it was .056 alum which I though was thin but I already dropped it in a move in the winter with no damage, guess I'll never be a good roadie!  

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