I am busy trying to get my head around springs and 'Dashpots' and their related stress Vs time and strain Vs time graphs.

I understand that stress is force/unit area and strain is the deformation of a body caused by action of stress.

Am I on the right lines?

So when a force is applied to a spring (or dashpot) can you assume that to be an instantaneous stress (in terms of a stress Vs time graph)?

Now imagine the same situation as above, but in a strain Vs time graph. The strain would increase proportionately to the time until the system is in equilibrium (in the case of a spring). Am I Ok so far?

Now for a dashpot, the stress in instantaneous and the strain will increase proportionately to time as long as there is stress acting?

So if I were to increase the viscosity of the liquid in the dashpot, the stress would be the same. Would the strain be less for a given time?

I also need to come up with graphs for springs and dashpots in series and parallel.... doh.

Dont be surprised if im totally barking up the wrong tree here, all advice much appreciated!

Iain

ps. I acknowledge all the stuff above is probably copyright by Newton or someone and i do not intend to copy, distribute or rip off anyone. I dont think there is any hidden meaning or racial undertones in my post but if you find some, feel free to shove them up your arse. Please dont call me a c*nt.

Most of that sounds about right. The liquid is there to act as a damper, so the thicker it is, the slower everything happens. So, the strain/time graph will be flatter/ have lower strain for a given time, until equilibrium is reached. How do you link them is series/parallel?

imagine a spring welded to the end of a shocker. Bolt the shocker to a wall and pull on the end of the spring... That would be in series. If they were both attached to the same bit of wall and you pulled the opposite end of each at the same time, i guess that would be in parellel...

a shocker or dashpot will never reach equilibrium as there is nothing to stop the thing moving (in an ideal model!)

The more I try to explain this the more I understand!

Ta, Iain

It should reach equilibrium or it would never stop! the force on the pitons/shocker end will be countered by the reaction in the spring. It may take a while, but it has to stop sooner or later. Hence the reason for the spring in the first place.

i was referring to JUST the shocker, no spring

A coilover shocker and spring could be seen as being in parallel i think (this WOULD reach equilibrium)

Ah, it makes more sense if I think of a shocker rather than a dashpot. All I can think of is the SU versions with air bleed hole and other complications! I think you're right about the series parallel bits. In series it won't reach equilibrium, it may reach a limit of travel on the shocker bit though. Parallel will reach equilibrium just as a coil over will. Probably easiest to think of it as a coil over actually.

Bang on.

Please dont bring carbs into it though!! We'll be here all night...

Iain

Do the graphs need values or just general shapes?

just general shapes, I think im getting there gradually...

Next thing is to derive equations....

Iain

That shouldn't be tooo hard to sort out! Is that specific or just with X value for spring, Y for damper extension rate etc?

the equations or graphs?

The graphs should be easy enough, the equations may be a bit harder though.

i found some of thes usefull
http://www.csgnetwork.com/scienceconverters.html

http://www.csgnetwork.com/automotiveconverters.html

I used to find this useful when doing uni work.....

http://video.google.co.uk/videoplay?docid=-7439171952665148194&q=crazy+frog

watch it three times in a row and I guarantee everything will click in to light. A bit like hypnotism for studying! Oli.