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Long straight edges

IronSkull

Plastic
Joined
Dec 6, 2011
Location
Dearborn, MI
Good evening folks.
I am currently taking measurements so straighten a large cast steel frame. To do this I must attach two straight edges that are 20ft in length to this frame. These straight edges must be set parallel to each other and equal distance from the median centerline of the frame, at a similar height. We are currently using 2x2 structural tubing and it bows and sags too much over that length. And thoughts on a better straight edge. Again the length is 20 feet. And must be set parallel to each other to within 1/64”. With this, we can more accurately gauge irregularities in the frame.
Thank you.
 
Either use an alignment telescope and travelling targets or a taut wire gauge and micrometers or water gauges (yes, really!). You are in the territory of machine lineout, not localised flatness.

Any of the above will achieve what you need. You just need to find what will work best for this job and future ones.
 
I will be pulling wire to check alignment of piston bores in this frame in the near future. (Tomorrow) I also have a tram wire pulled through the median center of frame that will be used to set the parallels. The need for ridged physical parallels as opposed to optical or wire is that I must be able to set and clamp squares to them to check that other sections are perpendicular and evenly spaced.
 
Wow. Although there would be room for them that certainly is massive. I might add that these straight edges do not need to be self supporting. They will be clamped or suspended be brackets attached to the frame. The original practice called for 5/8 x 3 bar but we’re finding that over 20 feet it is difficult to keep it straight. That is why we tried structural tubing as it bends less over large spans. Perhaps cold rolled as opposed to hot rolled would prove more ridged?
 
Wow. Although there would be room for them that certainly is massive. I might add that these straight edges do not need to be self supporting. They will be clamped or suspended be brackets attached to the frame. The original practice called for 5/8 x 3 bar but we’re finding that over 20 feet it is difficult to keep it straight. That is why we tried structural tubing as it bends less over large spans. Perhaps cold rolled as opposed to hot rolled would prove more ridged?


How about upper and lower tubes - some verticals - and some turnbuckles and cables and make yourself a TRUSS - that you can adjust to suit rigidity and straightness?

As to cold rolled flat bar - last I bought any 12 feet was the max length - maybe that has changed?
 
I have a simple straight edge made for doing similar work as you describe, it is made out of a small wide flange beam. Might be 5" wide and tall and 6 or so feet long, milled on both sides to be straight and parallel. If you had a light weight 12" tall beam that might work for you. It would probably need machining on both top and bottom surfaces to really be good.

Or just get a larger sq tube. 8x8 or bigger, aluminum if possible.
 
I will be pulling wire to check alignment of piston bores in this frame in the near future. (Tomorrow) I also have a tram wire pulled through the median center of frame that will be used to set the parallels. The need for ridged physical parallels as opposed to optical or wire is that I must be able to set and clamp squares to them to check that other sections are perpendicular and evenly spaced.

It's not 1885 any longer. Yer playin' wit' yerself.

You want to get DONE before the next ice age? Bite the "optical" bullet and be glad it is now laser, cheap, readily had, and even easy to use.

Folk that hang suspended ceilings, large office buildings, or pave high-speed jet aircraft airport runways have had this down cold for ages - even BEFORE the age of small, light accurate, lasers.

Basically, you'll establish a master point of reference, propagate it to the intermediate "relay" points you need where "the plan" had you bracketing-on physical squares, and cross-shoot off those to "targets" and/or via mirrors.

"Basically".

Yah need SERIOUS accuracy, better-yet can be had off the use of differential laser collimeters.

Folks who do this all-day, every day can be hired as an already expert team, equipment choice "their job", be it owned or rented, and it is not a large headcount. "Team" can be ONE guy who knows his shit, more often two, plus mebbe an "assistant" to mostly tote & carry!

Or.. yah can research it, acquire the goods, learn to DIY, be happy yah no longer have to lift and position, handle, and store so damned much awkward and heavy s**t to do it "the hard way" and rather badly.
 
Give us an idea of what you are trying to accomplish and you will get better replies. There are (relatively) cheap rotary construction lasers that use receivers that will read to .050". For perpendicular, an ordinary level will work. Or if an angle, a clinometer.
 
There are (relatively) cheap rotary construction lasers that use receivers that will read to .050".

..and not TERRIBLY expensive ones that will read to thousandths and tenths-of.

Millionths is harder..

But then again? Just how closely controlled is the TEMPERATURE of this whole rig, and what is the plan for compensating for these unavoidable buggers:

Earthquake Fast Facts | FEMA.gov
 
I was using piano wire to get .060 over 200 ft lengths as recently as 1996. (bridge construction....)

Or, as was mentioned, an alignment telescope. ($$$)
There may be lasers that can do this relatively cheaply
but I'm not familiar with them.
 
Here in Europe, Aluminium rulers are used in building, these are extruded ladder section, 4" x 3/4"I know they exist in 6meter lengths. Extruded,they are surprisingly rigid, and straight because they are very light, something like 1/16" walls!

Regards, Matthew
 
I was using piano wire to get .060 over 200 ft lengths as recently as 1996. (bridge construction....)

Or, as was mentioned, an alignment telescope. ($$$)
There may be lasers that can do this relatively cheaply
but I'm not familiar with them.

Three ("pre laser" AKA visible light) Davidson D600 Differential autocollimaters here ran me about $300-$400 each, used. Figured I'd need three to get ONE good one. All 3 are good! The calibration wedge and the special mirrors were harder.

Laser goods, obsolete but still useful are already as cheap or cheaper.

That said, yah RENT this s**t, proven, not bleeding edge, but "current" technology, and CALIBRATED, nonetheless - not stale nor of dodgy spec.

Main reason is the newer it is, the less-fussy it is, the "smarter" and easier to use it has become so the SOONER the job is done, and the less $$$ spent on expert time & overheads. "F***king around" shouldn't really be on the menu.
 
Three ("pre laser" AKA visible light) Davidson D600 Differential autocollimaters here ran me about $300-$400 each, used.

What I don't understand is this was at a company that was valued somewhere between 50 - 100 million. The secretary (down boy!) could pull a grand out of the petty cash drawer without blinking. The bosses wanted it done this way (in the shop, where I was doing dry assembly). I have no idea how they did the final assembly in the field, but I was wondering why the hell didn't they spring for some lasers even back then???

Regardless, the inspectors said my numbers were good even with the piano wire, so it shipped. Quarter million of product per day. With piano wire and some very very old ancient techniques (plumb, level)
 
What I don't understand is this was at a company that was valued somewhere between 50 - 100 million. The secretary (down boy!) could pull a grand out of the petty cash drawer without blinking. The bosses wanted it done this way (in the shop, where I was doing dry assembly). I have no idea how they did the final assembly in the field, but I was wondering why the hell didn't they spring for some lasers even back then???

Regardless, the inspectors said my numbers were good even with the piano wire, so it shipped. Quarter million of product per day. With piano wire and some very very old ancient techniques (plumb, level)

Well.... Whatever is good enough.. is good enough to the NARROW mind of the average counter of beans. Somebody has to SELL 'em a better way off the merit of it being more profitable, having a one-year "payback" .. reducing risk of fail & penalties.. etc.. not just newer nor fancier.

2d generation USACE, here, and Dad with US Coast and Geodetic Survey prior to 1931?

We "ordinarily" only work to decimal fractions of a foot, not INCH... but then again.. the miles involved are hardly trivial, and we HAVE been at it "for a while"!

See also Great Pyramid of Cheops. Accurately laid out Mike Foxtrot it was and is.
Greatly pleased to have had a private tour of ALL of the inside of it.

"Run what you got", but no need to not have "got" better goods when yah can get 'em and end up saving coin as well as time!

Drucker: "Nothing HAPPENS until somebody SELLS something."

Better ideas and better techniques need to be "sold" internally, too. ELSE, "surprise, surprise" ..... "Nothing HAPPENS".


:D
 
Ja, the pyramid. I have been studying their ways. Evidently the north corner was shifted off true north by about 5/8 of an unch by an earthquake around 950 AD. The stones were fitted within less than .003 using saws and red ochre for marking out.
 
Ja, the pyramid. I have been studying their ways. Evidently the north corner was shifted off true north by about 5/8 of an unch by an earthquake around 950 AD. The stones were fitted within less than .003 using saws and red ochre for marking out.

Check the ancient "rebuild" project on the adjacent Temple of The Sphinx.

The flat-as-surface-plates facings had their back sides hand cut to fit tightly over the OLD rough stones. See also the "Grand Gallery" stones and their guidance structures, inside.

Bronze Age technology. Or so we think it was, by then.

But the stone age was long enough, mankind must have learnt a thing or three, already.

And we haven't quit yet, given stone is still in inventory here and there...
 
If you go wire there was a good thread here on it with links for sag tables (the first link is dead, another couple later in the thread work). I didn't know this but CERN and Stanford use taught wire for alignment on linear accelerators, get something like 2 micron precision in 140 meters.

With the wire in place it should be fairly simple to set up a "portable" station to clamp your alignment squares to wherever you want.
 








 
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