Author Topic: Pretty accurate long tape rule  (Read 530 times)

Offline PekkaNF

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Pretty accurate long tape rule
« on: October 04, 2018, 03:26:34 PM »
Long story short: Need some information about 15 m long tape rule that is very much more accurate than the ones used in building industry.

Least 20 years ago the crew has left the project and we had to check some alligments. No theodolite or such, one old hand had a german tape tule that needed 50 N weight to stetch with correct force and I think we used it to measure pretty small difference in 15 mm loop (or circumfrence).

Now we have some customers that don't have access to optical measurement system and they wold like to use tape and/or lines to identify problem to some extent without resorting to outsourcing the measuremet (with couple of days to wait and serious money).

My concern is not absolute accuracy, but comparision and repeatibility. Would like to measure realiably 1-2 mm difference in half an hour time span, make multiple measurement and notice a difference that might be close to uncertainty of the tape properties.

Only document I could find was about survey. Sort of right stuff, but wrong scale.

Any ideas where to find info an maybe to find a tape just to try out and satisfy my curiocity.

Also if there is manufacturer for modern accurate steel tapes that can be used to check alingments mechanical parts, when optical measurements are not an option.

Thank you,
Pekka

Offline hanermo

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Re: Pretty accurate long tape rule
« Reply #1 on: October 15, 2018, 11:37:19 AM »
Pekka .. if a comparison / reference is the main concern, any steel tape measure should serve.
So should a dti on a rigid rod, or ladder, etc.
As long as the temp is similar, the accuracy in repeatability must be there.

Google pi tape.

A port crane lifting containers, 70 m long, twists about 15 cm in x due to sunlight.

About 3C/micron/inch in D in steel iirc.
So about 40 microns error / m in length for 3C temp difference.

The better consumer laser length measuring tools are about 3 mm iirc in accuracy on 15 m construction-type sizes.
But they might repeat to a lot better.
And they are under 100.

You could rent one from a tool rental place maybe ?
Insert playing cards as shims and watch results ?
Does it repeat if a deck of cards is used as a gage ?

No idea, but in theory they should be very consistent.

The chicom cheap 1u micrometers for 20 are crap.
I tried 4.
The good ones are excellent, around 50 retail.
Similar should apply to the laser rangefinders.

The proper ones using interferometrics used to be 30k$ or so a few years back.
I suspect the prices on these will collapse similar to servo/stepper drivers and gps chips.

Offline PekkaNF

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Re: Pretty accurate long tape rule
« Reply #2 on: October 15, 2018, 01:13:09 PM »
Thank you.

This is exactly what I was lookng for, but least 10m long, ideal is about 15 m. I ahve seen one german made and one american made. Can't rememeber brand though. Like this, but longer:
https://pitape.com/specs/O.D.%20EXTENDED%20RANGE%20METRIC%20instruction%20sheet.pdf


This is a little special...lets't say there are many rolls like in a web processing machine and there are many rolls that only few are in a straight line of sight.

Obivious choice would be the use of tacheometer or theodolite and prism and and all sorts of stcks to bring the reference to line of sight.

Not everybody has the equipment and personnel to use optical measurement and stick micrometer bends badly around concrete and steel beams. But because material web makes it trought the mace, tape would be pretty intitive and to go same route.

Pekka

Online ddmckee54

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Re: Pretty accurate long tape rule
« Reply #3 on: October 30, 2018, 03:54:26 PM »
Pekka:

A little more information would be nice, if it's possible to share it.  I understand about confidentiality agreements - been there done that.

You refer to a web processing machine.  What's the problem, web not tracking properly?  Or is the web not being processed properly through the rolls?

What are they trying to measure, roll diameter or alignment between rolls?  A 10-15m tape would give you a roughly 3-5m roll which is a helluva roll under most conditions.  Then again a 10-15m tape isn't much for a long machine.

Is this a new installation, or has it been sitting there for a while?

Don
Too many irons, not enough fire.

Offline PekkaNF

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Re: Pretty accurate long tape rule
« Reply #4 on: October 31, 2018, 12:31:04 PM »
Pekka:

A little more information would be nice, if it's possible to share it.  I understand about confidentiality agreements - been there done that.

In priciple, nothing too secret about it, but customer confidentiality is very high on my list.

Think of paper /cardboard or glasfibre processing, slitting, winding, cutting, sheeting etc.

You refer to a web processing machine.  What's the problem, web not tracking properly?  Or is the web not being processed properly through the rolls?

There are host of problems on high speed if the material web does not track properly. e.g. the web is slit and sheets are separated (this is intentional) and then material web does moves sideways over the guide rolls and end up incorrect location on cross machine direction. This side shift migh be only 1-2 mm at 5 meter distance (machine direction), but it will create problems.

The problem migh be because material web profile is not straight, surface structure problems or guide rolls (or other rolls) are not correctly aligned.

What are they trying to measure, roll diameter or alignment between rolls?  A 10-15m tape would give you a roughly 3-5m roll which is a helluva roll under most conditions.  Then again a 10-15m tape isn't much for a long machine.

Rolls might be anything from about 300 mm to over 1000 of dia. And distance between each of them can be from 200 to 5000 mm, and there might be stuctures between them to prevent simple linear measurement. Machines are tens of meters long.

1) To measure distance between two rolls left and right: This is like to measure diameter of one roll, but the tape is looped between twol rolls and measured left and right sides. Rolls are cylindrical i.e diameter does not vary cross machine direction (no barreling or bow) but they might be of different diameter. I.E. diameter is constant, only explanation to different measuremet is alingment problem (or measurement error).

2) To measure group of rolls like case#1, but looped tape mimics material web track and on two measuremet you can check alingment of many rolls at once.


Is this a new installation, or has it been sitting there for a while?

Don

On new installation we have our installation group with a tachymeter (or theodolite) and they have some special equipment to see over the corner.

This is purely for customers that have no highly specialized equipment and personnel.

I have found one cheap tape used in building industry and specification is nearly good enough for this one. I think I'm going to buy one for my personal use, smuggle it to work and test there against proper measurement equipment.

Pekka