I am teaching a kids summer class regarding time travel. I want to travel both in the future and past. I would like to demonstrate how an LP works - since most young kids have no idea what an LP really is today. I will be comparing mechanical to laser (cds).

I was hoping to set up an experiment where I can use a standard sewing needle and somehow amplify the sound mechanically with a cup. I would like to stay away from any electronics if possible. My budget is limited (as the limit reaches zero)

Any ideas if this even possible?

Thanks,

Lou
LFFUCHS@USA.NET

I do not believe that you can do this as you indicated. I see that you would like to try and connect the sewing needle to the cup via a string which would be tight and allow the needle's vibrations from the grooves to be amplified in the cup.

When 2 people use the cup and string method to talk, the string is held taught between the bottoms of the 2 cups.

For an LP, the string would have to be tight from the eye of the needle to the cup while also holding the needle in the record groove without dampening the signal. Even in old phonographs, the ones with the horn to deliver sound, the needle was mounted in a crystal. This prevented the arm from vibrating with the needle.

You may try holding the needle in the tip of an pencil eraser or maybe a slot in a toothpick to allow some vibrations to go through while still being able to keep the string somewhat tight. Waxing the string would also help in the sound transfer. It will take a steady hand to keep the needle in the groove. You are more than likely to ruin the LP as the needle's point may be very sharp and being hand guided it would not track in the groove very consistently.

Hope this helped.

Hi Guys,
Maybe rather than reproducing an LP you could build a type of player piano wheel? Just a rotating cylinder with nubs on it and some metal prongs that get 'twanged' (scientific term of course) as the cylinder spins. This is generally the same principle.
Just a thought. Later,
Ron

Hi!
On any LP player, you can disconnect the loudspeakers and hear the needle and related hardware make a clearly perceptible sound - but not with 20 children around.

Older LP players had no electronics, the needle moved a membrane located at the apex of a horn. As loud as speaking.

So by attaching some surface to a needle, you'll get a well audible sound. I wouldn't take a sharp hard needle. A softer steel would be solderable with Sn-Pb to some sheet. You may try cyanoacrylate glue as well. Polyurethane foam would be nice as the membrane, with a better sound than thin metal.

Your idea should work just fine, except it's easier if you use a straight pin. Something with a head on it, so it won't fall through the hole in the cup or box.

Take a straight pin. Stick it out of the side of a box. Cheerios worked good when I was a kid. Towards the bottom, sealed end of the box.

Quaker Oats box might be good too.

EDIT: I guess it goes without saying that you do NOT want to use a record you care about.