Heat from PSD

Too many variables...

https://www.f1technical.net/forum/viewtopic.php?t=4587

You have the energy inputs. All the mechanical motion should be converted to heat (force x displacement). You still need to characterize the energy outputs (conduction, convection, radiation) and the heat capacity (temperature rise per unit of energy, which is a function of materials and mass of each. Different parts of the shock absorber will be different temperatures depending on where the heat is generated and how it conducted away.

If you can get a hold of a thermal camera, you could set it up to take pictures and get a temperature profile. (Be careful that your body heat isn't reflected from metallic parts.)

Thanks for the insight. Since it is meant to be a sort of preliminary approximation done on excel, I will assume only convective heat transfer and specific heats of materials will be another input. As for the differing regions of the absorbers ( Base valve, piston head etc) let us assume the entire absorber is treated as one black body, regardless of the fact that the internals of the absorber have differing regions of heat generation. What would you recommend for a calculation given that I'll have access to the average power signal from the PSD/ASD? I was thinking a simple 1-D convective heat transfer calculation.

An example was given in the link I posted...about 1.2 watts per kilometer by my est average good smooth road surface at highway speeds with average weight car, of course the rougher the road and the heavier the vehicle, the more heat generated...

https://www.matec-conferences.org/articles/matecconf/pdf/2017/47/matecconf_bultrans2017_02006.pdf

<...1.2 watts per kilometer...>

Please revisit the units on this parameter, and reassess.

I would put it at about 34 btu/h for each single tube oil filled shock...at some point it would reach a temperature that would dissipate more rapidly and the temperature would level off, probably around 120°F at an 80°F ambient temperature...For rougher terrain, gas shocks would be more suitable...

Getting better: power per unit equipment is understandable; power per unit distance didn't make sense here.

It depends upon a lot of other variables, such as the ambient temperature and pressure, wind vectors, and the level of ventilation provided by its passage through the environment, etc.

It would be easier to strap a thermometer of some sort onto the side of it, and measure it.

...=²/₅f(all)³.

Reading between the lines I think you already understand this but I'll add it to this thread anyway. A shock absorber doesn't stop the vibration, it is just a mechanical low pass filter with, typically, as much loss as possible.

Your first approximation model might be a simple mechanical PSD in and heat out model. This effort probably can't go too far until the model expands to, at a minimum, mechanical PSD in, mechanical PSD out, thermal conduction out through metallic mounting rods/plates and thermal conduction/radiation out through the air. This last one could be made more complicated if the path to air is altered by splashing water at times and by dried mud at other times. Velocity of air flow will also be a significant factor.

I don't know if you are asking this as a student, employee or someone who is hard-core about their hobby. There are some free simulation programs available. In addition, most everything electrical can be modeled mechanical and mechanical modeled electrical. It is a little "bailing wire and chewing gum" but I have modeled mechanical systems using the free electrical simulation program "spice" before.

I am an off road enthusiast with a small shop, so definitely a Hobbyist. What kind of programs are they? I would appreciate some links. Thanks.

In a previous life I used the purchased optional thermal package for the purchased CAD system SolidWorks. That is probably out of scope for most hobby activities.

In a previous life I also wrote perl scripts to create large arrays of "components" to play around with heat flow in the free electrical simulation program "Spice". That is probably not a good choice for this activity.

I suggest taking a look at OpenFoam at https://www.openfoam.com/. If that seems like it might be in scope for you then look at some YouTube tutorials on OpenFoam. I have not yet learned how to use OpenFoam but it has been recommended to me by several people, it appears to be a very respectable package and it is Open Source (legally free).

(With a little Google work you can find other options but OpenFoam would be at the top of many peoples recommendation list.)

Thank you for this.

I would also add that I do not want to consider conduction and external environmental factors such as mud, water etc. for these preliminary purposes. I am just looking for a simple easy excel formula to roughly estimate temperature rise after x amount of time given a PSD/ASD RMS power input signal.

Another variable would be the proximity and the transfer of heat from the prime mover.

It's all getting a bit too difficult for numerical analysis...

I would probably just operate the vehicle in the environment I was curious about and shoot the shocks with an ir gun every so often...They do make temperature monitoring systems for shocks...If this is for off-roading, then I would go with pressurized 'for purpose' suspension system....

https://www.drivingline.com/articles/suspension-theory-with-king-shocks/