FPE panel thickness - 3mm?

[Shannon Parks]

I'm planning to order a Front Panel Express top plate for my 300B amp and will use a Hammond walnut base: http://www.hammondmfg.com/HWCHAS.htm
I'll order a HWCHAS1710BK and use the black top plate as the bottom cover and order a 15.75" x 8.75" top plate from FPE. What thickness would you recommend? I'm thinking these heavy outputs will require 3mm, but anything more might be overkill. Thoughts?

Shannon

[EWBrown]

I'm SWAG'ing that the three Edcor trannies would weigh about 26 pounds, and the 3 mm thick panel should be plenty strong enough for that. The trannies will be closer to the rear edge, so the Hammond chassis base will help support the weight. The rest of the chassis mounted parts, circuit board, etc shouldn't add too much additional weight, and that would be more or less evenly distributed across the plate's surface.

If you have an unused / spare 3mm plate, try supporting it by the two ends (on 2X4s) , and stack up some weight onto the middle and see what, if any flexing may occur.

In a couple of cases where I had a regular (read that as thin and flimsy) aluminum or steel chassis with a heavy iron load, I used a 1/2 or 2/4 inch aluminum angle bracket under the chasis, with the front-most mounting holes of the trannies all drilled in a straight line, and put the (matching-drilled) angle brace under these, and thechassis load bearing capability was greatly increased.

This would take a relatively flimsy thin chassis top and make it nearly as rigid as a steel plate... With a 3mm plate, it could probably hold up a hundred pounds
without noticeable flexing.

/ed B

[Blair]

Hi Shannon,

I'm a fairly young guy in decen shape, and I can't put this on a shelf:) it's 3mm.

[EWBrown]

That looks like a real "herniator" with all that heavy iron onthe plate.... The 300B's ironloading is about 26 pounds, plus perhaps another 5-6 pounds
of small chokes, and the rest of the small parts,PC board, etc. The 3mm plate should work out well with that!

That's a SERIOUSLY huge choke !

/ed B

[Geek]

My 845 tilts the scale at 84 pounds and uses 3mm no problem!

*edit*

I just re-read this and see you're thinking Hammond.

Hammond uses a very soft grade of aluminum and I'd put their supplied top aside and get a chunk of 3mm 5052-H32 from a local shop.

[nyazzip]

you could always brace it internally using aluminum "angle iron" stock or square tubing from a home improvement store, and rivets or screws....but you'd have to plan the inside layout for it....

[Geek]

you could always brace it internally using aluminum "angle iron" stock or square tubing from a home improvement store, and rivets or screws....but you'd have to plan the inside layout for it....

I've had to do this with some chassis and it works quite well!

If you use U-channel on its side or square and affix it with the power/OPT mounting bolta, you can use it as a rail to mount auxillary iron or PCB's without making extra holes in the top chassis!

[Shannon Parks]

My 845 tilts the scale at 84 pounds and uses 3mm no problem!

Cool.

Hammond uses a very soft grade of aluminum and I'd put their supplied top aside and get a chunk of 3mm 5052-H32 from a local shop.

I'm going to use the supplied Hammond 2mm top plate as the bottom cover (they discretely note that they are the same dims), and get the 3mm top plate from FPE. I think the bottom cover will add the last bit of rigidity.

Shannon

[TerrySmith]

If you need aluminum stock www.onlinemetals.com will cut any size / thickness you want for very reasonable prices.

[EWBrown]

I'm sure that you could specify harder/ stronger aluminum panel from FPE, like you say, use the hammond plate for the bottom cover.

I just checked the erstwhile KT88 "Herniator" chassis panel from FPE,3mm, 17 X 10 inches, it is pretty darn stiff, I could just barely flex it, with maximum effort.
With support from the four sides of the base, it should be able to hold me up, and I'm around 100 kg of massive rippling muscles
and sinews

/ed B

[Shannon Parks]

While going over datasheets for AC with fuse snap-in connector and the power switch, 3mm also seems to be the limit of their design. Good to know. I printed out a 1:1 drawing of the near complete top panel using the tile print mode, and MAN, this thing is huge!

Shannon

[Shannon Parks]

Got my Hammond 17x10x3 walnut chassis (HWCHAS1710BK) yesterday, made a couple measurements and inspected it, and just now ordered my FPE top plate this morning. I ordered mine from Mouser with $7.99 shipping from FedEx - not bad for a big box. Anyhow, the quality is a solid 'B'. I'm tempted to refinish it, but I haven't the time for that. The recess was about 3.2mm, so my 3mm panel won't stick up over the edge. I did see that one of the #8 screw inserts was just slightly off, so I changed my chassis mount holes to #10 on the panel for a little slop, otherwise the screw would have gone in at an angle. Finally, I probably will squirt some more wood glue along the edges on corners for good measure. I'll post pix after I see that everything fits. So the Hammond was about $100 shipped, and the FPE panel is $110 shipped (I won't be surprised if that gets revised upward due to the older pricing in my software from 2010).

One nifty thing regarding my top plate: I made two sets of transformer mounting holes. One supports the Edcor series and the others support the Triode Electronics series. I plan to mount and test both.

Shannon

[Blair]

What do those Hammond chassis run? I've been curious about them as a cost savings, but if the quality is just OK, then it's a waste.

Thanks,

Blair

[Shannon Parks]

What do those Hammond chassis run? I've been curious about them as a cost savings, but if the quality is just OK, then it's a waste.

Thanks,

Blair

It was $92 plus $8 shipping. If it seems solid after I bolt it all together, then it's an OK value. They seem to be in stock everywhere, too.

Shannon

[Blair]

Hi Shannon,

This may be if interest to you. .125" aluminum and no bends. This should hold about anything.

http://item.mobileweb.ebay.com/viewitem ... 0227594241

Blair