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Date:         Sat, 9 Aug 2008 00:41:04 -0400
Reply-To:     Jim Akiba <syncrolist@BOSTIG.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jim Akiba <syncrolist@BOSTIG.COM>
Subject:      Re: [NVC] Engineers: quick and cheerful vibration analysis?
Comments: To: Mike Elliott <camping.elliott@gmail.com>
In-Reply-To:  <489D178C.8080202@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

No worries, I didn't get offended... except by the mention of mythbusters, I can't watch that show... sometimes they're fine, but more often I find myself explaining to the TV how they don't really know what they are talking about... it never seems to work.

Using low cost low budget tricks can work very well if done thoughtfully though... here's a link to an audio test setup I did for collecting DB and frequency data from the passenger seat of a vanagon(little lower than where an ear would be though)... the DB meter is cheap with no logging or output capability, the video cam is pretty cheap but has a low-enough-noise mic input to use the decent ECM mic suspended and shown in the background for a reasonable input. The rig cost nothing since I had all the bits and pieces already, including software, and only took about two hours from build to final output of the video data. It's a big file to DL(126mb), and you need a reasonably fast CPU to view it without dropping frames... but if you do, the cool part is the WOT pull where you can "see" exactly where the loudest drone is in the frequency range(which is very useful for making quantified and objective comparisons) again the absolute accuracy of such a setup is highly questionable, but relatively speaking across test to test with the same rig it's extremely good... and that's all that was required in this case too.

http://www.bostig.com/files/autosubieej22.avi

Jim Akiba

On Sat, Aug 9, 2008 at 12:05 AM, Mike Elliott <camping.elliott@gmail.com> wrote: > No insult intended! This idea spun so wildly out of control! What started as > a mild curiosity -- whether I could use vibration analysis equipment to > study a not-terribly-important seemed to take on a life of its own. I was > not intending to put down your practical solution, instead, I was goofily > spinning things toward absurdity. I just don't express myself as well as I > wish I did and sometimes don't know when to put a sock into it. > -- > Mike "Rocket J Squirrel" Elliott > 71 Type 2: the Wonderbus -- NOW SOLD TO THE BUYER OF OUR HOUSE > 84 Westfalia: Mellow Yellow ("The Electrical Banana") > 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano > KG6RCR > > > > On 8/8/2008 8:53 PM Jim Akiba wrote: > >> Ah my mistake, I thought you actually wanted to get an answer as >> quickly/easily as possible ha... R Goldberg is about using creative >> unneeded steps to get the desired result, and make the whole process >> an interesting and fun distraction with the end result the punchline >> to the long setup. If anything is goldberg, this thread, the sensors, >> laptop, and software are it... you could have been done by now with a >> video camera.. hell even a piece of cardboard, elastics, and weighted >> magic maker will give you the peak to peak displacements of the >> trailer bounce! It's a *very* simple thing you're trying to find out, >> why complicate it? You don't need absolute data at all, only relative >> information is needed to reach the desired answer, and that's a piece >> of cake with very little... if it wasn't so dangerous indeed riding on >> it and reporting back would be even simpler. If you want an excuse to >> buy toys, that's different, but totally understandable as well... but >> at least acknowledge the fact that the simpler path to the solution is >> never by definition the goldberg one. You know the simplest thing to >> do would be to start the trip, adjust it on the road, and see if you >> can tell during the drive.. it might be obvious.. and if it isn't, >> it's not likely to matter all that much in any case so long as you >> aren't wildly out of range. >> >> Jim Akiba >> >> On Fri, Aug 8, 2008 at 7:02 PM, Mike Elliott <camping.elliott@gmail.com> >> wrote: >>> >>> Well. Yes. Of course. One /could/ use such a *sniff* low tech approach. >>> One >>> might as well plant a small boy back there with a video camera, Blair >>> Witch-style, and review the tapes later.* >>> >>> There is something about your solution that I like: it appeals to my >>> inner >>> R. Goldberg. But my inner Mythbuster (read: Grant Imahara) wants >>> accelerometers and graphs. >>> >>> I, personally, would combine your approach with my approach (subjective >>> ball-watching v geeky graphs and stuff AND would add to it some means to >>> inflate/deflate the tires remotely while in motion as well as sense and >>> report back sidewall temperatures. I'm telling you: with sufficient >>> funding >>> this could quickly mushroom into a completely absurd project! >>> >>> ==================== >>> >>> * Actually, if that wasn't so darn dangerous and illegal, it would be a >>> great way to evaluate tire pressure v ride harshness! >>> >>> -- >>> Mike "Rocket J Squirrel" Elliott >>> 71 Type 2: the Wonderbus -- NOW SOLD TO THE BUYER OF OUR HOUSE >>> 84 Westfalia: Mellow Yellow ("The Electrical Banana") >>> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano >>> KG6RCR >>> >>> >>> >>> On 8/8/2008 9:41 AM Jim Akiba wrote: >>> >>>> For what you're trying to do, software, sensors and data are way >>>> overboard I think. Match the solution to the problem... you simply >>>> want to be able to verify that at X tire pressure you do or don't have >>>> an additional level of "bounciness" whatever that means correct? >>>> >>>> What not just grab a cheap video camera, some bungees, a plastic wide >>>> mouth jar big enough for a tennis ball, a ping pong ball, and a >>>> softball for example(you might need something much heavier/lighter >>>> depending on the displacement and frequency of bounce). Put the tires >>>> at X pressure, write that on a piece of paper and "show" this to the >>>> running camera(to link that tire pressure with the video with >>>> certainty) that is now strapped to the trailer and recording the ball >>>> in the see through plastic container. Ride in a set path that you will >>>> repeat at whatever speeds you would like. Concentrate on road safety >>>> and consistency in driving. Change the tire pressure a few times and >>>> repeat. Simply watch the tape, and "see" what you can see... You >>>> could likely run this test and have an idea of what you want in the >>>> same amount of time it would take to track down a good sensor for >>>> cheap, install the software, run the test, and analyze the data.. and >>>> I'm almost 100% certain that interpreting the simple visual data will >>>> be much more intuitive for your average bear than raw numbers... >>>> especially if you aren't sure of what range of displacements and >>>> frequencies you're starting with(which you would really need to >>>> ballpark to even pick the correct sensor) >>>> >>>> Hope this helps, >>>> >>>> Jim Akiba >>>> >>>> On Wed, Aug 6, 2008 at 12:06 AM, Mike Elliott >>>> <camping.elliott@gmail.com> >>>> wrote: >>>>> >>>>> This is a question for the engineering geeks here. >>>>> >>>>> Say you were towing a little trailer behind your Vanagon. Say that the >>>>> trailer had a rudimentary suspension consisting only of leaf springs. >>>>> Say >>>>> that this trailer also had tires, the pressure of which could be >>>>> adjusted: >>>>> higher pressure results in a harsher ride, while lower pressure results >>>>> in >>>>> a softer ride. Say you wanted to determine the optimum pressure of ride >>>>> vs >>>>> tire squishiness but were unable to find a small boy to ride in that >>>>> trailer to report back about smoothness of ride v tire pressure while >>>>> the >>>>> experiments were being conducted, so lacking that small boy, your >>>>> thoughts >>>>> naturally turn to instrumentation. Okay, so say you had a laptop >>>>> computer >>>>> (WinXP) which could ride in the passenger seat, and /three/ business >>>>> days >>>>> in which to acquire the needed sensor (accelerometer?) as well as the >>>>> software to display the ride bounciness. >>>>> >>>>> Could it be done? >>>>> >>>>> -- >>>>> Mike "Rocket J Squirrel" Elliott >>>>> >> >


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