Air resistance and wm2d

[oustneocons]

Hi,

Medium time lurker, first time poster. I recently stumbled across this whole PM wheel project and with not being a follower of the "official line" in physics to dissuade me, think the only real impossibility was that it couldn't be done. So after absorbing all the info the net had to offer I thought I'd try some designs. The problem I'm having is with Air Resistance setting in wm2d. I'm getting the opposite results of what I think I should be getting and I'm unsure if it's a glitch or my lack of understanding on how it actually works. I would have thought that High Air would provide more resistance, but it's the Low air setting that stops my 50lb wheel almost immediately. I've included a pic showing both outputs and detailing the wheel size. Any guidance would be greatly appreciated.

BTW Wonderful site and kudos to all of you.

[graham]

Good question.

Jim ??

Graham

[jim_mich]

In the real world air resistance acts differently at high speed than at low speeds. So in a simulation you choose which situation you think should apply. Since air resistance is a result of complex air flow patterns around real life 3D object, a simulation can only give a hint of what would happen. This is why there is no fixed and absolute air resistance factor. Only an experienced engineer might be able to estimate an air resistance factor that would be somewhat accurate to real life.

I normally leave air resistance off. Then if a simulation slows down I know it is consuming energy and definitely not producing any. If it maintains a somewhat steady speed after settling down from any initial out of balance then I know the system balances and it is just coasting. If I ever see a simulation speed up then it's interesting. I will then put a reverse torque load on the wheel that kicks in after so many seconds. If the wheel then slows down and turns in reverse I know it's not a PMM. If I were to turn the reverse torque back off after a few seconds and the wheel were to speed back up then I have found the answer we are looking for.

[graham]

In the real world air resistance acts differently at high speed than at low speeds. So in a simulation you choose which situation you think should apply.

OK I get it . Thanks for your answer Jim.

Graham

[oustneocons]

Thank you Jim for your response. I'll try to incorporate those procedures into my wheel testing. What might be a a good torque setting for a reverse torque load test, for say a avg 50 to 100lb wheel?

[jim_mich]

A good torque setting is found by trial and error guessing because it depends on the wheel's mass. If it's too small nothing happens. If it's too large the wheel immediately spins way too fast. You will know when it is about right.

[rlortie]

Eric Vogles, computer programer and owner and moderator of minatowheel@yahoogroups.com recently downloaded the demo WM2D. He is also a member of this forum but we never hear from him here.

He has somehow figured out a way to save his screen shots then animate them in .bmp file format! A sample of this can be found at

http://www.fdp.nu/dualpistondevice/default.asp

Note! you may have to register in his group to gain access, but for those who use WM2D and do not have a license to "save", may find it very interesting.

Ralph

[Dave Chippy]

how do you make mu metal on wm2d

[wheelrite]

aha!, i know nothing of wmd but a little about aerodynamics. Accurate modelling of the res is possible but LOTS of work, well beyond the justification of a 'quick' wheel test. You need a great deal of accurate input data on the components and their movement to get a very good idea of what it SHOULD do. There really are no short cuts/software etc. thats just the way it is. Jim's rule of thumb steps seem the best 'screen' to tell if its promising.