Penny Sorting Aluminum Channel - weight discriminate trap door.

[LEberhart]

I want to build a trap door about an inch long in a 1/2 wide aluminum channel down which pennies will slide. I want new pennies (weighing about 2.5 g) to continue, but old pennies (weighing 3+ g) to drop thru the hinged piece.

Can I use opposing compression and torsion springs to optain such fine control?

Any other top of the head ideas welcome.

 

[Ron]

Why do you think that there would always be such a difference in the mass of new pennies and old pennies? Old pennies are worn but accumulate debris. Have you done a study on this?

 

[LEberhart]

Yes, Ron. To date I have collected 203 pounds of pre-1982 pennies. It is well documented on the net, and by my back where I return pennies in weighed bags. The old pennies have about a 2-1/2 cent value each based solely on copper value.

Glad I could answer your question.

 

[Ron]

I would consider a tilting hinge over a spring design. The tilting hinge would allow the heavier penny to slide through a slot whereas the lighter penny would pass by. You will have to play with the slope of the channel to keep the pennies from going too fast by the slot.

The hinge pin should be parallel to the direction of the penny travel. If you do it perpendicular, the trailing pennies will fall like lemmings over a cliff.

The hinge "counterweight" can come from an actual weight or from the hinge material extending past the hinge to counteract the 2.5g pennies but not the 3.0g pennies.

Good luck.

 

[LEberhart]

OMG, so simple. I thank you so very much.

 

[berkshire]

You realise of course that it is illegal to melt pennies for their copper value.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[LEberhart]

Yepper, and it is illegal to send them out of the good old U.S. of A. However, they are already trading on eBay for those who are anxious. I expect that someday, after my demise, it will become legal to melt them as it now is for old silver coins.

Could not find tilting hinge of appropriate design, but can readily fabricate from wood, the bracket to hold a likewise fabricated calibrated teeter-tottor.

 

[berkshire]

I do not know if this would be relevant, but in the early 1970s I was involved in making a sorting machine to get silver quarters and half dollars out of clad coins for banks. Since the coins weighed the same, the only difference was the ring tone of the coin.
we made a sloping chute where the coins would roll down and strike an anvil, as the coin bounced, a microphone would pick up the ring tone. Depending on the tone a solenoid would activate, or not, deflecting the coin into one of two bins. one for the silver and one for the clad.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor