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1970s Design Indulgence

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 12:56am
Originally posted by peterb peterb wrote:

You can achieve the same result with 2.5/3 mm drilled holes. If your Brake press has a segmented upper it might be possible to flip the job and fold in the opposite direction? 
Personally I am not fond of Nuts and Bolts/Screws in assemblies, where possible I try to use Hank bushes or if space allows, Avdel bushes. They seem to make assembly easier and faster, for a small extra cost. Smile


I'll try modelling corner holes, but SECE is a bit awkward in the direction the panel thickness and bends are extruded. I want to use a 200 x 210 cut piece, and if I subtract the 2 x 4.76 folds (that give 5mm "platform height") then it gives a 190.48 x 200.48 model. And it does if you extrude upwards, but if you extrude downwards (both thickness and folds) it adds the thickness to the folds. If you then trim back to 5mm, when it's flattened it loses around 3mm from the panel size and it's obvious it isn't going to work.

I found that after doing all the hard work of placing the hole locations. It's not that you can change the model's overall size, because that stretches the "rip out" clearance at one end. Basically you have to see the entire thing before you draw it. Seems a bit pants.

You can fold by drawing a fold line, but only in "ordered", but in ordered you can't do other things you need to do.

My thoughts for the corners were to simply crop them at 45 degrees as that will do, although it won't draw that.

I really like the Avdel nutserts, but at £150 for the tool and nutserts is more than I can now afford. Amazon has plenty of super cheap alternatives which I wouldn't touch with a bargepole, so it's nuts and screws unfortunately. Embarrassed

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 1:03am
Originally posted by BAK BAK wrote:

Where the AL bottom rests on the bottom wood panel,
 use a 5mm thick piece of bar stock either end as a spacer to attach to the bottom wood in 4 places. 
This will stiffen at the sides and make the corners stronger.

 Then only need to use the brake for the other 2 sides, bending them up to join with the front and back.

Unfortunately, the height below the aluminium sheet is 3.8mm. The overall height being 5mm to the top face.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote BAK Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 1:15am
Originally posted by Graham Slee Graham Slee wrote:

Originally posted by BAK BAK wrote:

Where the AL bottom rests on the bottom wood panel,
 use a 5mm thick piece of bar stock either end as a spacer to attach to the bottom wood in 4 places. 
This will stiffen at the sides and make the corners stronger.

 Then only need to use the brake for the other 2 sides, bending them up to join with the front and back.

Unfortunately, the height below the aluminium sheet is 3.8mm. The overall height being 5mm to the top face.

 The height below the aluminum sheet is 3.8mm, is that about the thickness of 2 or 3 stacked nuts?

4mm bar stock may suffice as a side-stiffener?

Bruce
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 8:25am
Originally posted by BAK BAK wrote:

 The height below the aluminium sheet is 3.8mm, is that about the thickness of 2 or 3 stacked nuts?

4mm bar stock may suffice as a side-stiffener?


As my imagination won't run to building a fully enclosed metal chassis inside the wooden case, which would be ideal (I guess because of its 360 degree shielding), it will be a collection of metal panels and metal platforms, all grounded to each other by wires.

The "inspiration" came from the "hi-fi" valve (tube) amplifiers I've seen. Sometimes there's only a chassis plate - the rest is wood. The signal levels at the input stage of a valve amp are very similar to solid state, but all the circuitry above and below the chassis plate are wide open to atmospheric noise. Yet they seem to be "effectively shielded" and are never subjected to noise problems - it's always some 360 degree shielded accessory that causes all the problems... LOL

So, internal height is 81mm and wanted usable height is 75 to 76 mm (which is what the metal cased version had), and that leaves 5mm for a sub-chassis metal platform on which each section is built (all things associated with that platform bolted to it).

The 3.8mm internal fold (5mm external because of the 1.2mm material thickness) is the thickness of one M4 nut and one M4 plain washer, and because of the compression of wood, it might also take a shake proof washer - then each metal platform sits on these four corner mounts. All will be revealed as soon as I can get the drawing right.

Another problem is my computer. The Think Centre MT720 seems to be a few slates short of a full roof. It is having trouble running SECE, especially if I want music while I work. Therefore, all those things that happen instantly on the Youtube tutorials, take some time for it to "click" on my computer, which is really confusing, and means that I can't do all the slick placements like they do. To adjust for a misplaced hole means forcing it to move by using "smart dimension" which has a "driving end", and that uses up even more memory... Ouch

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Post Options Post Options   Thanks (0) Thanks(0)   Quote peterb Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 9:42am
Originally posted by Graham Slee Graham Slee wrote:

I'll try modelling corner holes, but SECE is a bit awkward in the direction the panel thickness and bends are extruded. 
My thoughts for the corners were to simply crop them at 45 degrees as that will do, although it won't draw that.
I really like the Avdel nutserts, but at £150 for the tool and nutserts is more than I can now afford. Amazon has plenty of super cheap alternatives which I wouldn't touch with a bargepole, so it's nuts and screws unfortunately. Embarrassed

I am afraid I would have cheated and just drilled the holes and ignored the the tiny notches! After all it is all 'in house'.
I made a crude Avdel setting tool by brazing a SS Bolt on to the end of a piece of square bar, an 1/8" plate with the correct bolt clearance hole and clamps. A spanner then provided the crimping force. A bit slow and clumsy but cheap! I did wonder about modifying a good quality Pop Rivet gun, but never got around to it.
Peter
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Post Options Post Options   Thanks (0) Thanks(0)   Quote peterb Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 12:17pm
PS. SE has several Ali Alloys to choose from and they have different materials properties. If the bending allowance it has provided seems not to suit your material you could try changing to another alloy to see if it is a better match.
I am still trying to finish my SE drawn MDF box for my Son's Sub, learnt lots but still not enough to do exactly what I want!
Peter
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 5:54pm
Originally posted by peterb peterb wrote:

PS. SE has several Ali Alloys to choose from and they have different materials properties. If the bending allowance it has provided seems not to suit your material you could try changing to another alloy to see if it is a better match.
I am still trying to finish my SE drawn MDF box for my Son's Sub, learnt lots but still not enough to do exactly what I want!

I think "cheating" might be the way to go.

Aluminium tables show 1050 grade of 1.2mm thickness has a bend radius of 0.5t, so 0.6mm. The pan brake fingers aren't chamfered so if I adjust set back to 0.6mm (or even 0.5mm by sight), and scribe a line 4.76mm from the edges of the panels using my Vernier (not supposed to use a Vernier like that), then it may produce the 5mm (external) return.

SECE doesn't list 1050. It does list 1060 whatever that is.

I can use the hole puncher using the 3/16 punch on the scribed line corners and snip the corners to that. OK, it's a bit big but I'm not after fancy corners.

Then if it bends right, I can sit the inside corners flush to the 3/16 die, and I should get something like 12mm in from the adjacent faces. That should be repeatable for the corner holes, and the wood base panel can be drilled for it to fit.

Therefore, no drawing required!

But I'll be able to do a hole positions drawing to stick on top of each pan, or even make a flat template for hole punching.

Fully squeezed nutserts make excellent stand-offs provided you're not too bothered about the board height. And I won't be bothered as I'm hard wiring to the power transistors. We had an Avdel tool but it gets used on Communicator cases, so I've lost that to John C. Unhappy

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