'Shocking' question

[Gary Stockton]

Should you be able to compress a shock absorber by hand and then have it stay in a compressed state until you pull it out again?

I suspect not, in which case my left rear Tough Dog is goosed :-(

 

[OG.]

Not always. Gas shocks will extend again when released.

 

[clivehorridge]

I always question why "Shock Absorbers" are so named because that's not what they do!

Shock is absorbed by the spring, the "misnamed article" is there to stop the spring reciprocating (going boing, boing, boing in technical terms) i.e. as a damper to the spring.

IMHO they really should be called "Dampers" and I'm sure they used to be years ago.

Therefore, the damper is designed to compress without restriction (to allow the spring to absorb the shock) and then to restrict extension again, usually by the use of oil being forced through a small hole, thus slowing down the speed that it extends.

Of course, technology has developed on this basic principle and the use of gas, internal springs, multiple chambers, external chambers and the like makes them more complex, but they are still basic dampers to stop uncontrolled bounce in the springing of the vehicle.

I'm sure that there's many on this site that would have explained all that much better than me, but I'm sure I'm right in this basic approach. Any opinions?

 

[Gary Stockton]

Yep I'm happy with how they work but I suspect that when not fixed top and bottom (ie no restrictive bounds) the internal pressure should be enough to make the piston expand fully, which is why they're normally shipped with a locking band through them. I'll check the other side ...

 

[Shayne]

I've always wondered why the basic set up of motorcycle front suspension hasn't replaced separate shocks and springs . The only real difference is a bike has the spring inside the damper . My guess is it would simply last too long and so remove an income for manufactures . Take a 30 year old bike , change the seals and replace the oil and the fork suspension will work as good as they did the day they were made , as far as I can work out the only way to kill them is to bend them which would be almost impossible to do inside a wheel arch behind your wheel .

 

[clivehorridge]

MacPherson struts do you mean? Used since 1955 odd maybe the 60s on fords cortina, anglia, and so on up to the present day.

 

[Shayne]

MacPherson struts do you mean? Used since 1955 odd maybe the 60s on fords cortina, anglia, and so on up to the present day.

Could be Clive I bow to your superior knowledge of such things , for me it's been an idol curiosity for quite some time . Any idea why all suspension is not like this ?

 

[Chris]

Gary, the answer is - both. Some do self extend and some don't. It all depends on make and type.

Chris

 

[majic79]

As Chris says, some do, some don't. Anything that's got a sealed pocket of gas (ie, remote canisters, monotubes or gas dampers) will automatically expand out - how much depends on the gas pressure (force must overcome friction). Twin-tube arrangements (most common type of conventional car suspension) don't expand out and only work with the tube oriented vertical or close to it (put one upside down or on it's side and they just slide in and out with hardly any resistance)

 

[clivehorridge]

Could be Clive I bow to your superior knowledge of such things , for me it's been an idol curiosity for quite some time . Any idea why all suspension is not like this ?

Now now Chris...

Horses for courses and all that...

IMHO macPherson's are fine where they belong, sadly that ain't on a hard working hard driven 4x4. Neither are torsion "springs" despite Mr T using them on some of his products, again MHO.


Formula racing quite likes combined spring/damper units, verical or horizontally... must be something good about them...

 

[Chris]

Eh? Huh? What did I say?

C

 

[clivehorridge]

Eh? Huh? What did I say?

C

What didn't you say, more to the point! Naughty naughty

 

[Chris]

You've lost me Clive. All I said was some do and some don't. Which is factually correct. Not sure there's anything more I could have said.

Baffled.

 

[clivehorridge]

You've lost me Clive. All I said was some do and some don't. Which is factually correct. Not sure there's anything more I could have said.

Baffled.

My mistake Chris, pologies!

Ive just re-read the thread and I'd got myself mixed up. Too complicated to explain...

Ill get my hat and coat... !

 

[Chris]

Ahh, no worries mate. It's strong stuff the Romanian red.

C

 

[clivehorridge]

Ahh, no worries mate. It's strong stuff the Romanian red.

C

Tis too, but I wish. Alzheimer's more like!

 

[OG.]

As Chris says, some do, some don't. Anything that's got a sealed pocket of gas (ie, remote canisters, monotubes or gas dampers) will automatically expand out - how much depends on the gas pressure (force must overcome friction). Twin-tube arrangements (most common type of conventional car suspension) don't expand out and only work with the tube oriented vertical or close to it (put one upside down or on it's side and they just slide in and out with hardly any resistance)

Erm... didn't I say that at the start of the thread? ;-)

 

[majic79]

yes, and I'm just adding that some are not sold as "gas" shocks, but do have a pocket of compressed gas and give the same effect (e.g. Monotubes, the damping is from an oil, but because there's volume in the piston rod, it has a pocket of gas behind a membrane or other segregation device and that's what gives it the "spring" to return)

As he's asking for opinion, I thought he'd like additional input rather than relying on one persons say so, so I added mine to the heap