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Possible precision problem - not sure.

Started by kenhoganson, November 07, 2019, 10:44:31 pm

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kenhoganson

I noticed that Lionel O-gauge FasTrack small sections are showing as not the correct length by AnyRail - probably due to rounding error.   Using English Decimal to 3 places for Measurement System:
1-3/4 straight is identified as length of 1.752.   Correct length is 1.75.
1-3/8 straight is identified as length of 1.374.   Correct length is 1.375.
So, is this an error in the stated length by AnyRail?
Or is this an error in the actual length of the section (within AnyRail).   
The other straight sections are identified precisely correct.   I am not sure why there is ANY deviation in track geometry.
Are there deviations of this size with the curved track sections?

If these small deviations are in AnyRail's length of these sections, then could a problem occur as these small deviations accumulate.   Seems like it would take a lot of section deviations to be noticable.   Could a curving track section with many small O48 and O36 sections, plus many small straight sections end up with a 1/8" deviation?
Can you please analyze and explain?   Thanks, Ken.

David

This is only in the stated length.

The cause is that this length is part of the part description, which is accurate to 1/10 of a millimeter.
So, for instance, the 1-3/4 part has in its internal description:
"STRAIGHT 44.5mm."

The word "STRAIGHT" is translated into the target language the user has set: French, German, English, Japanese, etc.
The specification "44.5mm" is converted into the units the user has set: cm, mm, inches.

So this could be slightly off due to rounding errors.


The internal track definition is correct, a straight with a length of 44.45mm.



We might need to walk through all the descriptions once again to check this.

The reason we make a difference between the description and the definition is that in some cases a track part is known as 10" but is in reality 9.9". If we would put 9.9" in the description, this might confuse people even more.




David Hoogvorst. Founder and Owner of DRail Software. Creator of AnyRail.

kenhoganson

November 08, 2019, 04:38:42 pm #2 Last Edit: November 08, 2019, 04:45:39 pm by kenhoganson
Thank you, David!
At first, I thought this was happy news, that the descriptions vary.   But then I read your last para about a 10" section actually being 9.9".   Are you saying that Lionel actually makes the sections at 9.9", not 10"?  Lionel confirms that they manufacture them at 9.9" and not 10"?  Is that on their web site somewhere?   I checked their website and Lionel states the length at 10.00".  I hope that you just mean this as an example; that manufacturing results can vary in the actual track piece.

David

No worries, it's an example, FasTrack is very accurate, but older Lionel track often has this.

For instance, Lionel O gauge part 65505 is in the catalogue as 5.5" (13.97cm), but in reality it is 5.55" (14.1cm). At least that's for the sample we have here. Batches seemed to vary slightly.

David Hoogvorst. Founder and Owner of DRail Software. Creator of AnyRail.