wondering if anyone is using some type of laser measuring device....even better is if someone is using one for diy allignments

reason i ask is most ones in the 150 and below range have an accuracy of up to +- 1/4 of an inch in like a 60ft range...i'm wondering how it would do in a 2 ft range so i would like to see some experienced people let me know (design and model as well of course)

if this were effective it would make my life a lot easier and not have to deal with strings....and when measuring from wheel to string i see it as being very very unaccurate as you have a lot of angles to reach the string with...just an idea i though of though..not sure if i'll commit

 

I use a laser while doing alignments, but I use it just like I would a string. Not an actual laser measuring device. It is just a beam that fills a whole plane, instead of just a line like the string. Plus it's hard to trip over.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by azian21485 &raquo;</TD></TR><TR><TD CLASS="quote">...most ones in the 150 and below range have an accuracy of up to +- 1/4 of an inch in like a 60ft range...i'm wondering how it would do in a 2 ft range...</TD></TR></TABLE>

(2ft / 60ft) * 1/4" = +/-0.0083" It'll be fine.

Just get the $40 laser level from Sears...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">(2ft / 60ft) * 1/4" = +/-0.0083" It'll be fine.

Just get the $40 laser level from Sears...</TD></TR></TABLE>
I'm not sure you can go with that kind of analysis. I can't find good information right now on the exact measuring method that these instruments are using, but it's easily possible that the error is not proportional to the measurement.

These devices also often have a minimum range.

If you do buy one, I would do some independent verification of the measurement accuracy before trusting it or the specs, especially if you are hoping for accurate results.

 

Your going to have to get the manus specs for it. There is usually a chart that shows accuracy in relation to distance.

I have a FARO unit that I use to make sure my chassis is aligned on all planes. Its accurate to .0001mm over 1m so its plenty accurate for my purposes..

Check out ebay. I got mine off there and I know there are some good ones from time to time.

As for the unit you mentioned, what does it have an A and B part that talk to each other or does it use a reflector plate ? avoid plate systems!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MechE00 &raquo;</TD></TR><TR><TD CLASS="quote">I'm not sure you can go with that kind of analysis. I can't find good information right now on the exact measuring method that these instruments are using, but it's easily possible that the error is not proportional to the measurement. </TD></TR></TABLE>

How can it not be proportional, the light's not curving. It scatters but doesn't curve. Besides, the way *most* people do alignments is to use a tape-measure or ruler, so realistically the repeatative accuracy isn't going to be better then 0.030" anyway.

About the FARO with 0.0001mm accuracy, that resolution is very misleading. Virtually every part of the car chassis, wheels, and tires, have tolerances far greater. Even air temperature and density will make everything vary far more then the 0.0001mm. Plus, compliances will make a repeated identical measurement impossible.

 

If you have a stopwatch and you are measuring how long it takes for someone to complete a ~60 second course, you can probably measure it to within a 1/2 second. So actual value may be something like 60 seconds +/- .5 sec.

But that does not mean that one a ~3 minute course the actual measurement is 3 minutes +/- 1.5 seconds.. the error magnitude in that case is independent of the measurement magnitude.

The instruments used to make the observations that the calculations are based on in the laser range finder may have an error mechanism that is not based on the magnitude of the measurement (as with the stopwatch example). Surely there can also be a signal-to-noise ratio issue that will scale with the magnitude of the measurement and give you a max range.. but that may not be the dominant source of error for the full range of measurement.

Without knowing more specifics about the technology used for the measurement and calculation, you're just guessing. I'm not talking about light curving, I'm talking about the electronic doo-dads that are making the measurements...

Of course, you're right about the .0000001 mm accuracy stuff. These days it's possible to have measurement accuracy way beyond meaning in the "real world". Of course the measurement device may _actually_ have that level of accuracy, if your test is set up to access it. It could also just be a bogus spec that a marketting department thought nobody could ever possibly check on..

blah.. rambling.. must eat lunch

 

I have the Smart Racing string setup.

It worked pretty good at first, but then the string began to wear out and accuracy went to hell. And then I think the batteries went dead and I can't find them.

It just hangs on the wall now, and I do the alignment by eyeball.

Scott, who's even having trouble with that now...I think I need special glasses.