Suspension question

alexo · Post by **alexo** » Mon Sep 12, 2005 8:41 pm

I noticed that most suspension jobs are dune using elastic cords.

Did anyone try metal springs?

vertigo · Post by **vertigo** » Tue Sep 13, 2005 1:12 am

I think it's easier to buy elastic than metal springs. You can buy elastic in any sewing shop. Where would you buy springs?

alexo · Post by **alexo** » Tue Sep 13, 2005 5:25 am

vertigo wrote:I think it's easier to buy elastic than metal springs. You can buy elastic in any sewing shop. Where would you buy springs?

I got some from Home Depot.

Assuming the availability issue is solved, are there any drawbacks?

hyperq · Post by **hyperq** » Tue Sep 13, 2005 6:26 am

I guess you will be the first one trying this. Please give it a try and tell us if it is better than elastics.

IsaacKuo · Post by **IsaacKuo** » Tue Sep 13, 2005 7:00 am

It's certainly possible to do, but my gut feeling is that it won't be quiet. I associate springs with "sproingy" noises.

Theoretically, the basic problem with springs is that they don't dampen vibrations much. That's why cars with metal spring suspensions also need shock absorbers. Without the shock absorbers, you'd just end up with an insanely bouncy ride.

I expect springs will transmit vibrations to the case, making moot the point of a suspension in the first place.

hofffam · Post by **hofffam** » Tue Sep 13, 2005 7:56 am

I think springs would work similarly to elastic. I think IsaacKuo is slightly wrong about shock absorbers in cars. Springs tend to go boing boing - which in a car will occur regularly. Shock absorbers slow the rate of up and down movement. A metal spring will transmit through the coil some vibration, but it is probably very frequency dependent. Audio turntables have used metal springs for decades to isolate the turntable platter from the base. Vibrations within the coil could be damped with soft foam inserted in the coil itself.

One of the challenges with springs is to prevent the suspended hard drive from rocking side to side if the hard drive is on top of a spring. A better choice might be to hang the hard drive instead. That is an inherently stable position.

alexo · Post by **alexo** » Tue Sep 13, 2005 11:40 am

hofffam wrote:One of the challenges with springs is to prevent the suspended hard drive from rocking side to side if the hard drive is on top of a spring. A better choice might be to hang the hard drive instead. That is an inherently stable position.

Yes, hanged from 4 springs.

Bluefront · Post by **Bluefront** » Tue Sep 13, 2005 12:37 pm

Ha....Been there, done that

These came from an auto-parts store...they were meant to cover head-rest posts. If you can find soft enough springs, it might work for you. I just played around with it.....

BrianE · Post by **BrianE** » Tue Sep 13, 2005 1:06 pm

I thought about springs very briefly at some point, but ran into a couple problems with the idea.

The biggest problem I thought about was selecting spring length and tension. You'll have to carefully select the spring tension so that it can support the hard drive(s) without over or fully extending, and without being so stiff that they don't extend at all. If the spring isn't extended you're essentially hanging the hard drive from 4 solid pieces of metal. With this in mind you will have to select the spring length.

Way too fussy to put together without some luck, trial and error, or very careful measurement and calculations I thought. I figured using shock cord ("bungees") is easier since they are made of rubber and always elastic, and you can do various tricks with them, like weave them sideways and tie them up and loop them around, so they seem more versatile.

Bluefront's method of resting the hard drive on compression type springs is probably a bit simpler to rig since they are already expanded.