Thoughts, suggestions on a REALLy straight section?

Lee,

Not sure if 15 feet will give you the results you're looking for when testing stuff.  Even at a relatively slow speed my trains seem to cover 15 feet very quickly.

Still, moving 15 feet to gain real estate for modeling purposes can't be all bad

The wood will change with humidity levels, you should use something more substantial, like air craft grade aluminium I beams.

well if you really want to pull your hair out measure your 15 feet, drive a nail at each end and tie masonry cord to both nails . This will give you that laser beam straight edge. Drive 2 more nails one at each end of the rail itself tie another length of masonry cord around each nail and slide it down to the top of the rail. This will let you know it's perfectly flat.

After your finished post some pictures of you standing beside it so we can call you "Old Baldy"

David

Zero your laser at the range according to the zero point on your ammo chart.

Return home, work out the math down to 15 feet and then do it.

Don't forget to move everything sideways a bit when you are finished and realign.

I recall a Satellite show in which a set of USA Rail was used for rocket sleds. They say those rails have a tolerance easily exceeded prior to a test by temperature or even planetary motion/curvature.

I don't have anything near that straight. I rely on a large long wheelbase engine to pick the bad spots. When it's all picked and runs flawless, I know I am straight.

Don't forget to level according to the plumb, not the house you are inside.

All joking aside, the section of straight I am laying is about round 41 feet. It will have a error of about 1 inch over that distance in pitch and about 3 degrees in roll axis.

The machine shop I used to work for back in the early 70s built a "Wing Vortex Vehicle" for NASA.  It went down a 1/4 mile long track to test different wing tips and the vortices (wind turbulence) that developed.

They kept increasing the speed of the vehicle (it also pulled a number of trailers containing the wing tips) but forgot to increase the brake pressure...ended up driving it thru the rear wall of the building!!!

If you plan on doing any speed tests remember you must also slow down at the end, taking up some of that 15 feet length.

That reminds me. It aint the starting that gets you, it's the whoa nellie.

Physics has a hold on you sometimes. I almost lost my life when my brakes faded on me with a container load of PBJ above a river and traffic light.

I often post pictures and discussions of my little victories and fun projects, so I will fess up and report this did not work.  Not a disaster, but not what I wanted.

The section is indicated on the diagram of my layout below.  I was moving this section "north" by 7 inches to make room for the beige line (a two-lane superstreets highway) immediately next to it in the diagram and decided to "true it up" in all dimensions just because I had the opportunity to . . . 

Anyway, the new section is done and it is 15 feet of truly straight track (I used a laser to adjust it in both dimensions - it runs like a bee line and it is flat as a board), and it is very level side to side.  However, it is not level from left to right: it turns out that between the curve on the left and the curve of the right end of this fifteen feet, there is a 1.6 inch rise (just a bit less than 1% rise to the right).  There was no easy way to fix that.  Turns out I did not see that because my benchtop was not truly level (it is off by about 1.2 inches over that length.  I think I knew this when I built it, but forgot. 

Anyway, the trains are running again. That is most important. 

In reading this, I have to wonder what the real utility is for making a "perfect" track.  Since the "real world" will never be that perfect, what does it accomplish.

This is not a criticism, I'm just trying to understand what you will gain from going to all this trouble.   Exactly what would you be testing that could only be tested on this "perfect" track?

My original thought was that it might be useful to have a perfectly level straight track to test locos on: 10 volts gives you 13.35 mph scale and 15 gives you 22.5, etc. 

This track section has always been fairly straight - a 'display section' where a train can stretch out and you can see it all in a row (at least if < 16 ft long)) it comes around and heads back toward \the operator (me) and any guests.  It just made it laser straight this time mostly to learn what was involved in doing so. 

Lee, that's where cruise control comes in, makes figuring this out easy.

CTT had an article a few months ago on a very easy way to measure train speed.  Instead of measuring the track, you measure the train and time the train from the point where the engine first passes a fixed point until the last car passes the fixed point.  Measuring the train is much easier then trying to measure distance over track curves.  The longer the train, the more accurate the speed measurement. 

The train speed on a non-cruise equipped train will vary somewhat, especially on curves.  But honestly, who cares that "10 volts gives you 13.35 mph scale and 15 gives you 22.5, etc." other then a licensed professional engineer.  

Taking the mph to the nearest hundredths is not realistic, since your voltage measurement was only to the nearest volt.  Additionally, lubrication, operating temperatures and other factors will prevent repeatable accurate speed measurements to the nearest hundredths.

Earl

What Earl said plus the fact that the earth is hurtling thru space at 25 thousand or so miles an hour and there goes the math and accuracy. 

Better to fill an MTH steamer with mega steam, set it on HIGH and see how long it takes the wife and kids to get out of yer hair.

Well, it was a fun idea, it just did not work out.  By the way, I have the Lionel speed sensor: looks like an overhead pedestrian crosswalk and connects to a meter to tell you scale mph as a train passes.  Very cool and pretty accurate.