I have been debating about this for a while and I think I am going to try it but I would like your opinions. I like the front face of the unit but the plastic knobs and buttons never really did anything for me. Since the replacement knob now uses a gromit to grasp the turn knob, I was thinking it would be easy to cast new buttons in metal (steel, platinum, etc.) to finish giving the unit a brushed metal look. I have started reading books on casting so I can create a negative mold from the extra knobs I have as a test.

Knowing that the plastic knobs are probably machine cast, is there any major problem you might see me running into? What metals do you think I should avoid casting in? (i.e. Gold is a very soft metal and I don't believe it would be a good canidate for small buttons) Would metal knobs and buttons screw up the internals of the unit or conduct electricity away from where it needs to go? Are the connectors too custom that casting in metal will not provide the amount of grab really needed for the knobs to work. Finally, the all important "if I am successful, would anyone be interested in metal replacement knobs and buttons" question?

Greg

Titanium would be cooler than a snowmans cold bits but i think that an aluminum alloy would be a far more practical option. I would be a set of titanium buttons but only because i have a titanium fetish.

But be warned that i have had an experience with alloy things in cars i bought an alloy gearknob and first thing in the morning after a cold night it was cold as rude word to touch

Not sure you can actually cast titanium; if you were able to melt it you probably wouldn't need it, if you know what I mean

You could do simple lost-wax casting with a variety of materials, the cheapest of which would be to cast white metal. However, the quality of this is debatable. Casting Aluminium would require a seriously expensive electric smelting oven or furnace and has explosion risks (Al spontaneously combusts under certain conditions near its melt point). It also requires a lot of finishing on the finished article as what comes out of the mold is pretty primitive.

One nice alternative is resin casting, which would give a good quality finished product without much finishing or great expense. You could mix Alu or anodised powders with transparent or coloured resins and cold cast it. It is pretty noxious stuff though and requires a lot of precautions to handle it safely.

You could always spray paint the buttons silver....

One of the few remaining Mk1 owners... #00015

One thing with metal casting, metal shrinks a lot more than it cools than plastic does - if you want knobs and buttons the same size as the plastic ones you are going to need a mould that is a bit bigger than the originals. Are lots of other issues too. Will try and remember a bit more from my metallurgy lectures and give you some more tips later on ...



(list 6284, Mk1 S/N 00299 4GB blue [for sale]. Mk2 S/N 080000094 6GB blue)

Greetings!

If you are really into the titanium thing, there are specialty places on the web that machine blocks of titanium for rings and jewelry. If you gave them a knob, they might be able to machine one for you - for a price...

Paul G.
SN# 090000587 (40GB Smoke)

In reply to:

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explosion risks

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Can you say thermite ?

Hans


Mk2 - Blue & Red - 080000431

He he - you've been reading your chemistry texts recently then

That's in combination with any iron contamination; there's also an oxygen issue as well, and thaleine.

One of the few remaining Mk1 owners... #00015

Ah, the good old thermite reaction

As I recall, it was the only thing our chemistry teachers could do to guarantee the undivided attention of a class of teenage boys...

Biology teachers had a potentially more effective attention-grabber, but unfortunately they stubbornly refused to stoop so low

Geoff
---- -------
Got one of the first Mark 2 empegs...

Hey don't forget good old water!! Throw a bit of that in your crucible of molten metal and see what happens!!!

(list 6284, Mk1 S/N 00299 4GB blue [for sale]. Mk2 S/N 080000094 6GB blue)

I loud popping sound I expect...

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Unit serial number 47 (was 330 in the queue)...

my physics teacher showed us the basics behind building your own atomic bomb but he was a bit mad

They use it in powdered form for rocket fuel.

Calvin

While i am thinking about who remembers that experiment where you get some candles and float them in a wee boat thing and then place them inside an upside down bell jar to show the oxygen being burnt away and then the water rising up the glass.

I have been told that this is a fake experiment as if you do the calculations about oxygen being burnt and CO2 being produced you discover that it should only rise by about 0.02% the real reason is due to heating of air expanding and the escaping and then the air contracts and pulls up the water.

Correct me if i am wrong.

Thought We really should have an non empeg forum

One of my chemistry teachers used to perform the experiment that demonstrated that oxygen and hydrogen are explosive in a 2:1 ratio. The difference is that he didn't use a large coffee tin for the experiment, he used a trash can full of hydrogen instead. The lid of the trash can would normally reach 60 or 70 feet (he did the experient outside).

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Unit serial number 47 (was 330 in the queue)...

Sounds like George Goble, the teacher who lit barbequeues with LOX. He's got a web site, and Dave Barry wrote a column on him once... funny stuff.

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Tony Fabris

Derek, your point about the thermal properties of metal is a good one.

Kazama, something to consider is that the shape of the knob's "Gripper" section is only engineered to work as a plastic unit. For instance, it expects that there will be a little flexibility to the plastic.

If you cast it in metal with the same shape, it will have different properties, and therefore won't work right. It will either slip off too easy or it will get stuck on so bad that you'll damage the PCB when you try to remove it.

So you'll have to come up with some alternate way of securing it to the shaft. A side-screw sounds like the logical way to go.

___________
Tony Fabris

Don't the MK2A's (Rio Cars) have an actual keyed knob? Something to keep in mind.

lit barbequeues with LOX

...and I'll bet that the chicken was still raw on the inside .


Roger - not necessarily speaking for empeg

The lid of the trash can would normally reach 60 or 70 feet

That brings back memories of a story my friend Joachim, a machinists apprentice in Germany, told me. He and his cousin went out in the countryside and built a campfire in a firepit with a cooking grille. They suspended a bottomless 55 gallon oil drum over the grille. Then they took a coffee can with a tight fitting lid, filled it half full of gasoline, put the lid on it, and set it on the grille. When the gasoline boiled, it blew the lid off the coffee can which filled the oil drum with gasoline vapors which in turn promptly ignited. He said the oil drum went so high in the air that it was just a little speck, turning end over end. The noise was pretty impressive, too.

Another little prank that would have ended his apprenticeship had they known who to blame... he welded up a box out of 6mm plate steel, about 15 centimeters on a side. He drilled and tapped a hole in one face of the box, filled the box full of water (about three liters), screwed a bolt into the tapped hole, and tossed the box into the annealing oven during lunch break just to see what would happen. The results exceeded all expectations -- the door of the oven was blown right off its hinges and across the room. Reminiscent of another experiment back in 1896... here.

tanstaafl.



"There Ain't No Such Thing As A Free Lunch"

Casting Aluminium would require a seriously expensive electric smelting oven or furnace and has explosion risks (Al spontaneously combusts under certain conditions near its melt point).

Well, speaking from experience, casting aluminum isn't all that difficult or expensive to do. I've used sand-casting techniques in the past to make a few things, and had no problems with the mechanics of it at all. A simple crucible, a small furnace made from a dozen or so firebricks, and a big gas blowtorch allowed me to melt a few kilos at a go no trouble.

My first attempt was making a heater block for a homemade smoke machine, and I melted down a load of old hard drives for the metal. It worked, although my moldmaking skills were decidedly primitive. The end result bore a marked resembalance to a cast aluminum cowsplat.

I'm slowly putting together better facilities to do casting, so I can make some bits for a supercharger. It'll probably be better in the end than machining the part I need from solid, which would require a 10 inch cube of the stuff. I can get it, but god it would take a while.

As far as the risks go, the main one is spilling molten aluminum all over the floor. This is not completely safe.

The explosion risk is more from steam, if either the metal you're putting in the pot is wet (bad) or the mold is damp (very bad). Mind you, when melting scrap aluminum, it's best to make sure it actually is aluminum, not magnesium. That was... exciting.

However, that said, making something as small as the knob or buttons in cast aluminum is a non-trivial task. For an acceptable result, you'd need to do a cast in a ceramic mold, which has to be about 3% oversize in all directions, and centrifuge it to get the detail. The end results of this technique are amazing, but it's not easy.

If you really wanted one-off knobs, they could be cnc-machined, but it would cost. The buttons may be a little small to be economically viable to produce that way.

Incidentally, titanium can be cast in a tungsten mold, but making the mold is the really tricky bit. Tungsten has a seriously high melting point, and what do you cast it in? (hint - it's either sintered or produced by chemical vapour depositation)

Hey, it's just a subject I have an interest in, okay?

Patrick.


Opinions expressed in this email may contain up to 42% water by weight, and are mine. All mine.

Ah, the good old thermite reaction

I like thermite. I've had a lot of fun with it in the past.

Hugo may remember one Guy Fawkes evening, involving about five pounds of the stuff, a hole in the back field, and a long fuse. You could see the flare for miles, probably.

The white-hot hole in the ground that glowed for two hours was pretty impressive as well.

I've always wanted to bury about fifty pounds of thermite in damp sand, and see how big a glass sphere I could make, but unfortunately recreational experimental pyrotechnics are frowned upon in this country, even though strictly speaking thermite isn't an explosive.

Mind you, I've also always wanted to fill a five-gallon glass jar with fine magnesium wool, pressurise it to about 40 psi with pure oxygen, and put it on a high hill with a timer. World's biggest flashbulb...

Oh well, I'm getting too old for that sort of irresponsible applied chemistry.

Patrick.

Opinions expressed in this email may contain up to 42% water by weight, and are mine. All mine.

You know between this, your casting interests and the Beanie Baby Horror Show (tm) I am starting to really feel like a normal guy here.

Oh scrap that, lets face it, if I had the time and the space I would probably be doing similar things. Guess we will both have to face up to the fact that we are NOT normal.

Cheers,
Hans


Mk2 - Blue & Red - 080000431

My chemistry teacter did the same experiment, only he used condoms instead of a tin.
He filled two of them with the gas (to about 3 feet long!), and one of the girls in the class offered to hold the strings (they floated).

The whole class went outside to a school field. He attached a weight to one of the strings, and lit the first "balloon" via the technique of throwing a lit match at it.

The bang rattled the windows on the side of the school, this caused people in other classes to open the windows to see what the noise was. Imagine the scene they saw of a girl holding the string to a 3 foot long floating condom.

Suffice to say we had a large audience for the second explosion... =)

Jazz
(List 112, Mk2 12 gig #40. Mk1 4 gig #30. Mk3 1.6 16v)

Hi Guys. A really quick question: so it seems that the knob can be replaced by empeg with a new version that does not slip? I am asking because mine does. Did I understand correctly?
Thanks


Taym
______________________________
empeg mk II blue 12Gb 090000923

just email support and they will send you a new knob that is what normally happens

I just did it. Thank you!


Taym
______________________________
empeg mk II blue 12Gb 090000923

For the Mk.2 the non-slip knob approach would work best - use a captive rubber grommet to make the friction contact.

The 2A (Rio branded player) has a keyed rotary shaft, and in this case a grub screw may be required.

Either way, I think this would be an ambitious project.

Rob

Hugo may remember one Guy Fawkes evening

I think Hugo's parents may still remember what you did to their driveway..

Rob

Privatly owned speedbump ?

Hans


Mk2 - Blue & Red - 080000431

post hole digging most likely

Murray 06000047
I don't think, therefore I am not.