Looking for alternative to a spring mechanism

[rahul.dhir]

Hey!
I'm trying to find a more cost efficient alternative to a spring for a design that I'm working on.
Basically, I'm designing a tile that you step on and drops about an inch and then comes back up when you step off.
I have been researching and trying to find springs to use, but my cost is coming up to $50 to $80! I need this mechanism to cost under $10.
There would have to be 4 supports for the tile (ex. 4 springs) and it would have to be able to take a total maximum load of 500 pounds. The mechanism would have to lower one inch when 200 pounds are placed on it.
What is a mechanism that i can use that would be stable and under $10?

 

[Danger]

Welcome to PF, Rahul.dhir.
The only thing that immediately comes to mind is some sort of rubber, but getting properly calibrated reactions could be mighty tricky.

 

[Reptillian]

You could try some sort of memory foam like they use in mattresses.

 

[rahul.dhir]

The main thing that i need with the spring is for the tile to return to the original location. The exact distance it drops is not important. I'm thinking that memory foam would have a hard time holding this weight. I think that i might have to stick with springs. Do you guys know any places where i can get some cheap springs??

 

[jedishrfu]

you could use weights and a lever if you have space under the tile.

or perhaps spring steel as used in a car suspension.

EDIT a leaf spring might be cheaper than a coil spring.

 

[rahul.dhir]

I know i can use the spring.. i need it to be under $10 and have a spring rate of 200lb/in

 

[berkeman]

(Why am I thinking that this is a spam setup?)

 

[huntoon]

how about Belleville washers?

 

[jedishrfu]

Could you get some old springs from a junkyard for cars and trucks, since your rating is in that range?

 

[Danger]

(Why am I thinking that this is a spam setup?)

Quite possible. I hadn't thought of that, but I can see where you're coming from.
Meanwhile, though, I'll give him the benefit of the doubt.
My other suggestion is something that I've used for all sorts of things in the past. Plastic hypodermic syringes cost next to nothing and are very well sealed. If the outlet is plugged, one of them makes a pretty good gas strut type of spring. A 50cc unit once supported my full weight without compressing to the maximum. Simply choosing the right size can determine the force needed to sink the tile if it's supported by 4 of them.

 

[jedishrfu]

(Why am I thinking that this is a spam setup?)

What criteria determines this conclusion? Is there some advertizing benefit to the op?

You could pm me if it's suspect.

 

[Danger]

What criteria determines this conclusion?

We occasionally encounter someone who makes up a fictitious problem, gets everyone involved, then claims to have discovered a "miracle cure" and links to a commercial site that he has a financial stake in.

 

[jedishrfu]

Okay thanks

 

[huntoon]

We occasionally encounter someone who makes up a fictitious problem, gets everyone involved, then claims to have discovered a "miracle cure" and links to a commercial site that he has a financial stake in.

Man, I thought the "miracle cure" was your suggestion to use syringes.. Flippin brilliant, if implementable!

 

[jedishrfu]

I get the feeling though that this is car related due the spring rating and I don't think $10 is going to cut it unless you can get the parts from a junkyard.

 

[huntoon]

I get the feeling though that this is car related due the spring rating and I don't think $10 is going to cut it unless you can get the parts from a junkyard.

i don't think so, he stated "Basically, I'm designing a tile that you step on and drops about an inch and then comes back up when you step off."

 

[Danger]

I get the feeling though that this is car related

Maybe, but I don't see how that ties in with stepping on a tile. Sounds more like he's trying to set up an Indiana Jones trap.

Huntoon, I've been using hypos for stuff since I was about 12. They particularly make great pneumatic or hydraulic cylinders.

 

[rahul.dhir]

Huntoon, I've been using hypos for stuff since I was about 12. They particularly make great pneumatic or hydraulic cylinders.

I was considering hydraulics as well, but i doubt that will meet my required budget..

 

[Danger]

was that what you were expecting me to say?

Pretty much, although the real scammers are very slightly more subtle.
My whole point of mentioning syringes is that they're dirt-cheap at a drugstore. Depending upon the laws where you live, you might even find them in a hospital garbage bin. That's illegal here, but different localities have different rules. Also, I didn't mean to use them as hydraulic cylinders in your case. Just coat a sheet-metal screw with silicone sealant and drive it into the nozzle from the inside. You'll have a perfect seal, and the unit will behave like a gas strut as is used on automotive hatch-backs.

 

[rahul.dhir]

hmmm alright.. like an air brake mechanism?
do you know of any tutorial for this?
also what is the formal name for this mechanism?

 

[Danger]

hmmm alright.. like an air brake mechanism?
do you know of any tutorial for this?
also what is the formal name for this mechanism?

There is no name or tutorial. As far as I know, I'm the only one who's ever done it.

CAUTION! I should have said this before: if you do go rooting around in hospital garbage, use very heavy (leather) gloves and boil anything that you find in soapy water before handling it further. You never know what might be in a syringe, or if it might still have a needle attached. It could have contained blood from an AIDS patient or snake venom.