[the4thseal]

yup yup yup......still working on molds....i hope mine turns out as well.

[307startup]

walter...
would you mind refreshing my memory as to what german site you are referring to? (regarding the mill that is...I remember a few pages back where it showed the molds made for that mill) Thanks...

[walter]

WYLD,

I believe it's this one http://5128.rapidforum.com/topic=110...6&search=beton
You have to register to get in.

[307startup]

Thanks much, I do appreciate it. You're pretty quick on the keyboard there, hoss!

[lgalla]

I was testing some surround sound subs on the weekend with an RTA and an old fashion sweep frequency generator.Steady 30 to 60Hz signals vibrated so intensely the cabinet walked around the room.I thought,what a good vibratory instrument for E/G LiquifyingE/G.Dial in or sweep to find the frequency of E/G where it changes to a liquid.
Check www.partsexpress.com and search" bass shakers",only for Mad Science Tists.
Larry

[jhudler]

search" bass shakers",only for Mad Science Tists.
Larry

Damn Larry! Stole my surprise! I have 2 of them I never put in the theater and wondered if I could bring myself to use them!

LOL
Jack

[lgalla]

Jack,good time to upgrade the surround sound,but the wife may not agree to using it in the shop.BTW I have never seen a cabinet move so much.It is a 12"cube of birch with a 10" and 12" passive radiator.The cabinet walls were shaken a good 1/2".I suppose an air vibrator would work just as well varying the air pressure which would vary the frequency.It is necessary to find the liquefaction frequency of the 10% E/G mix.
On a different tune,If your completed machine has annoying resonances use a variable strobe light from the seventies and you will see what is vibrating and the effects of damping.The strobe will freeze vibration and locate the source.
Larry

[the4thseal]

igalla-
so how are you controlling the frequency? sounds like a good idea.:-)

[jhudler]

Mass drivers would be great in a vacuum chamber because they don't need air. Damn I still can't believe someone else thought about this! Just goes to show you, every patent has already been thought of before, someone just decided to write it down first.

This crossed my mind back when Walter was looking for vibrators. It occurred to me that making a voice coil with heavy windings and a simple variable frequency AC power supply would do the trick. For that matter, just plug it in to the wall through an old fashion rheostat.

You can get 2x2 inch Neodymium cylinder on eBay for $100 that can pull 400 lbs so figure out the voice coil and power supply requirements for that!! Think I'd wrap the magnet in a thin PTFE sheet with an thin wall aluminum cylinder and wrap the voice coil on. Then E/G impregnate the coil and wrap it in a copper jacket to run cooling water in. And your set!

Hey didn't they make something like this on 'MythBusters'? Trying to reproduce a Tesla experiment on sympathetic vibrations causing building to collapse or something like that?

Jack

[lgalla]

the4thseal.Being of age or antique technology I use a Heathkit frequency generator.I am sure there is free sweep generators on the web.With my old technology I just klick in the frequency required.The free generators on the web are possibly only sweep but a steady frequency is desired.Possibly Cameron can elaborate as he has some audio experience.
Larry

[lgalla]

Jack,we had input many thousands of threads ago of speakers or voice coil transducers to shake.I discounted the process due to added costs.Now we have E/G addicts who will accept spending money to acheive their goal.Walter has spent mucho denero experementing for our benifit.Thanks Walter!!!
I don't know about knocking down buildings with high SPL,but my professional subs due 148Db/1watt.I cannot make buildings collapse,but cause 70Hz resonance of the chest cavity and 35Hz resonance of the bowels resulting in Diar...Ah!
Larry

[RotarySMP]

There are surely applications which require a perfect density E/G material with no air bubbles etc. Don't lose sight of the goals of many here though. For a hobby mill, I am sure you can get an outstandingly rigid frame despite defects such as air bubbles included. If you assume these defects, assume a material lower strength in your design, and just increase your feature thickness to compensate, you will be rewarded with a lighter, more rigid structure.

Perfect Airless EG is only going to be important when you are working near the limits of the materials capablities.

Here is a link to a very tasty Mill built with EG here in Austria. As you can see they didn't vibrate of vaccuum it, but simply rammed the material.

http://www.alpenheli.at/sites/cnc_fraese4.htm

[greybeard]

Mark - thanks for that Austrian link, very inspirational.
As I don't have any German, I have to guess - is that a college/university workshop ?

Regards
John

[RotarySMP]

Nope, it is the guys basement.

Have a look und tricks/tips he has a great method of making rubber bellows (Balgen in german).

Also the touch screen he added to the controller is pretty cool.

[greybeard]

Is that the small conical one for the helicopter you're referring to, or the bellows on the cnc ?
An amazing man.
Regards
John

[jhudler]

Here's what he said about it:
The fact that the concrete base (because of the weight of concrete and milling) is directly on the basement floor, I have an insane amount of sound transmission to the entire house note. Cutting at 24.000 rpm in Alu, the sound throughout the house is louder than directly at the mill.
At this point, is still absolute demand-currently given in the form of various experiments, which estimates the vibration coupling between milling and concrete plinth.

Yet here is the best solution is not found!



It appears he only cast the gantry, not the table or base sitting on concrete blocks. This would suggest that his "insane amount of sound" is due to the lack of damping from these missing E/G componets.
On the other hand, he could buy some vibration damping pads to reduce this. Like from one of our sponsers here; http://www.vibrationmounts.com/

[jhudler]

Just got through reading as best I could the German site on Mineral Casting.

Someone briefly touched on sphere packing but the subject never took off. Not one word on vacuum or Zeeospheres or similar aggregate.
In fact the whole discussion seemed rather... unscientific or let's throw this bit together and only use 10% epoxy to see what happens. Which most everyone found was rather grainy and didn't wet well. They settled on 12.5% as the formula.

Then the whole thing degenerated into a couple of guys taking it commercial, telling the other they were stupid and didn't understand it, and then the moderator (thankfully) shut it down.

Please let it not happen here.

We all know there are commercial aspects to this material but lets keep the formula and process public domain and if you have a private formula that works for you; great!

My 2 cents,
Jack

[jhudler]

Mark - thanks for that Austrian link, very inspirational.
As I don't have any German, I have to guess - is that a college/university workshop ?

Regards
John

Try this;
http://translate.google.com/translat...e=windows-1252

[jhudler]

Nope, it is the guys basement.

Have a look und tricks/tips he has a great method of making rubber bellows (Balgen in german).

That was pretty cool, have to try that with lost wax process.

[greybeard]

Try this;
http://translate.google.com/translat...e=windows-1252

Thanks Jack.
John