1. Originally Posted by funklab
I was led to understand we are indeed on the metric system. Apparently an inch a pound and a gallon are all defined by their metric equivalents now. For example there is no "standard pound" measure against which all other pounds are measured because the pound is an exact fraction of the standard kilogram.
I can't tell from your profile where you live...but clearly the United States that I live in still uses the pound measurement instead of kilograms, inches instead of millimeters, and gallons (of gasoline) rather than liters.

2. Although pounds, ounces, inches, etc. are still used for commercial enterprises in the USA, engineers, scientists, and health care providers use almost exclusively the metric system now. It is more accurate and precise, easier to use in math calculations, and makes comparison with and sharing of scientific data with the rest of the world so much easier.

Here is the US agency that maintains the standards for this: https://www.nist.gov/

(KLD)

3. Originally Posted by chasmengr
As a mechanical engineer (retired) I wholeheartedly agree!!!!
For example - length:
IP units include IN, FT, YD, Rod, chain, fathom, mile, furlong, . . .
SI = meter

USA stuck in IP is a real pet peeve of mine, but no matter now because I'm retired!!
Exactly the problem that cause the crash of the Mars lander about 10 years ago...some of the engineers were actually using inch vs. cm. measurements in their calculations for some reason. A very expensive mistake for using an antiquated system!

(KLD)

4. Regarding "... metric system ... It is more accurate and precise ..."
The metric system; indeed any system, is neither more nor less accurate or precise than any other system. Accuracy and precision are not characteristics of these systems.

5. Originally Posted by funklab
But back to the topic at hand, if tilite is so precise that the measurement is within 0.05 inches, why can't I get a chair that is exactly 13.35 inches wide?

My chair is such a tight fit that I literally cannot fit a finger between my hips and the side guard. And when I measure my current chair the proper way it is within about 1/8 of an inch, but it is wide by an eighth of an inch. If it happened to be an eighth of an inch narrower than spec (so a quarter inch narrower than it is currently) I wouldn't be able to fit in it.
To try to keep this on topic. Why would you want a chair that tight? Gain a couple pounds or get thicker pants and you could end up with a pressure sore.

6. Originally Posted by chasmengr
I agree - virtually zero tolerance on welded components (i.e., frame). TiLite's CAD drawings show units with one decimal place (e.g., 17.0, 19.0), which is an industry standard (known as "significant digit") indicating dimensions will be accurate to within half (i.e., 0.05) of the smallest indicated dimension.

from current ZR order form:

So, apparently your opinion has changed since you posted this:

Originally Posted by chasmemgr
When drawing a 3D TR3 in Google SketchUp, I quickly learned how one dimension can affect so many others. I recognize tolerances are appropriate because, at several locations, the designer must chose which dimension is more important allowing another dimension to float a bit. Then, during fabrication, accuracy and tolerances factor in. The final product will never quite match what's been drawn. Accuracy is relative; published tolerances are appropriate

To try to keep this on topic. Why would you want a chair that tight? Gain a couple pounds or get thicker pants and you could end up with a pressure sore.
Have you ever had a chair that fits you like a glove? At least with regard to width, mine does and it's friggin amazing. Firstly it allows me to be as narrow as possible, my chair comes in at just over 21 inches in overall width measured at the widest part of my chair (the bottom of the handrims with two degrees of camber). Fitting through a 22 inch door gets me into a bunch of the tiny half baths people have at their houses.

But leaving the obvious advantages of narrowness aside, I also "feel" (it might not be reality) that it gives me more stability and control. If I have my brakes locked I can grab onto something and pull myself onto one wheel without shifting at all in my seat, because the sideguard (which is essentially pulling my entire chair over in this situation) is already resting against my side. I can shift my upper body and adjust direction slightly rolling down long hallways without touching the handrims or making myself sygoggled (just now realized I only speak this word and have no idea how it's spelled) in the chair. In theory (were I actually still fit and strong enough), I could pull myself up a flight of stairs without ending up dragging my ass to one side of the cushion.

I don't think I'm adequately putting into words how nice it is to have such a precise fit, but my dump and front seat height on this chair are all messed up and I spend much more time worrying about losing the perfect width I have rather than trying to guess the precise dump and floor to front cushion height, so that ought to tell you something.

8. Originally Posted by gjnl
I can't tell from your profile where you live...but clearly the United States that I live in still uses the pound measurement instead of kilograms, inches instead of millimeters, and gallons (of gasoline) rather than liters.
I live in the US as well.

https://en.wikipedia.org/wiki/United...ustomary_units

"The pound avoirdupois, which forms the basis of the U.S. customary system of mass, is defined as exactly 453.59237 grams by agreement between the U.S., the United Kingdom, and other English-speaking countries in 1959. Other units of mass are defined in terms of it."

So at this point in time we choose to stick with the pound, but have yielded to the fact that because of the overwhelming need for precision in measurements we have to definite the pound by the gram. We discarded the former definition of a pound in the treaty mentioned above and since that time have been measuring all weights in grams by technical definition, but have chosen to continue reporting that measurement in grams by the arbitrary, but precise unit of 453.59237 grams because we are nostalgic.

It's like running into an isolated tribe in the amazon that has never met other humans and developed a number system that was base 453 instead of base 10. They agree that if they are going to interact with the rest of the world for ease of communication and trade they will use the "standard" number system with a base of ten for all calculations and then translate this into their native 453 base math just because that's how their ancestors did it.

9. Originally Posted by funklab
Have you ever had a chair that fits you like a glove? At least with regard to width, mine does and it's friggin amazing. Firstly it allows me to be as narrow as possible, my chair comes in at just over 21 inches in overall width measured at the widest part of my chair (the bottom of the handrims with two degrees of camber). Fitting through a 22 inch door gets me into a bunch of the tiny half baths people have at their houses.

But leaving the obvious advantages of narrowness aside, I also "feel" (it might not be reality) that it gives me more stability and control. If I have my brakes locked I can grab onto something and pull myself onto one wheel without shifting at all in my seat, because the sideguard (which is essentially pulling my entire chair over in this situation) is already resting against my side. I can shift my upper body and adjust direction slightly rolling down long hallways without touching the handrims or making myself sygoggled (just now realized I only speak this word and have no idea how it's spelled) in the chair. In theory (were I actually still fit and strong enough), I could pull myself up a flight of stairs without ending up dragging my ass to one side of the cushion.

I don't think I'm adequately putting into words how nice it is to have such a precise fit, but my dump and front seat height on this chair are all messed up and I spend much more time worrying about losing the perfect width I have rather than trying to guess the precise dump and floor to front cushion height, so that ought to tell you something.

Amen.

10. How about when ordering your new chair, you tell your dme rep to have tilite make the frame width 12.37" between the frame members

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