Hand-Chaining: How much tension on tape?

Normal Tension Pt = 0.2W (AE)/(Pt-P)

W = total weight of tape in lbs

Here is a redneck solution.

It is supposed to be non corrected at around 65 degrees, Fahrenheit. So, go out to a nice flat parking lot, that is about that temperature, lay it out flat, pull it up to around 25 lbs, and make 2 marks that are exactly 100' apart. Now, you have your "Standard". Then, get 2 plumb bobs, pull it up at around waist high, and see how hard you have to pull it, to match the measurement, while the tape was laying flat. In order to properly do this, you will need to either place a nail in the end of the tape, or educate your helper on how to properly hold the tape, without curling it too tight, at the end. Maybe even some real GRIP gloves, to help you pull it and secure it well.

This was the general process we used to educate our field hands, on taping.

Been yrs ago.

I gettin old.

Nate

Lufkin steel tapes are made to government standards. Our bench standards for the Unites States are certified accurate by the United States Department of Commerce, National Bureau of Standards, and Washington D.C. Tapes for Canada are made to Canadian government standards.

Temperature standard for steel tapes is 68°F, which equals 20°C. Coefficient of expansion of steel tapes is 0.000645 foot per degree F; 0.0000116 foot per degree C. This amounts to 0.000645 foot or 0.00774 inch per degree F. on a 100-foot tape, and one-half as much on a 50-foot tape. As a figure that is reasonably accurate and also easy to handle, it is customary on very long runs of pipe to allow 1/10” per 100 feet for each 10° change.

The above illustration shows, for a 100-foot tape, the actual length variations of temperature within the range of 20° below to 120° above zero F. The terminal graduation on the lower edge is at 68°, this being standard temperature. Furnished only when specified and at additional cost. Standard tension for steel tapes 25 to 100’ long (10 to 30m) supported entire length on a horizontal, flat surface, is 10 pounds (4.5 kg.); for all tapes over 100’, 20 lbs., (9kg.). For steel tapes suspended horizontally and supported only at ends, there can be no set or standard tension for accuracy because of weight and other variations.

The following listings are averages of many tests made by the Bureau of Standards of Lufkin steel tapes supported ends only. These averages are taken from the experience of tests and should be used as a working basis only, and not to replace the test of any individual tape. All tape lengths are 100’.
width type inches kind of tape tension of accuracy
thru-out in # supported ends only #
1/4 chain tapes 10 24
1/4 engineer's(.012") tapes 10 18
1/4 engineer's extra heavy tapes 10 24
3/8 &1/2 standard weight tapes 10 18

> Hey, all,
>
> New guy here. I worked as a rod man on a survey crew one summer around 1985. We did a small amount of hand-chaining when the total station thing wouldn't work, but my memory is dim.
>
> I recently bought an old transit so that I can lay out and level a spot to pour a slab for a workshop on my property, and I need to use a 100' steel tape to reconstruct the boundary lines (and re-find the corners) that I had a licensed surveyor do on my property about 15 years ago...
>
> My question is, when you use a 100' steel tape for hand chaining, is there a specific amount of horizontal tension (i.e., 35 pounds) that you are supposed to put on the tape to get the most accuracy? I mean, the more tension you put on the ends, the less of a catenary curve the tape will have and the "longer" it will get, so it seems like there should be a specification for how much tension you should put on it.
>
> I have searched for this info online but can't find anything.
>
> Thanks for any help.

If you are only looking for previously set points and you are not very far away from your starting points (less than 100 feet), the tension should not matter all that much as long as you don't have a large sag in the tape. This will get you within a few inches of the same measurement than with the proper tension. Once again, if you are only looking, get close and then sweep the area with a metal detector and you should find it if it is there. If you are settting a new pin, well then that is what a professional surveyor is for and needs the accuracy of a properly tensioned tape. However, be cautioned, if you do find the corner markers that were set, only a professional surveyor could check them with the accuracy required to verify that they are correct. If space is an issue, it would be worth the money you would spend on a surveyor to give you the piece of mind that whatever you build is placed in the correct spot.

Thanks for the reply, A Harris. Now I know that "normal tension" is something I can Google, which led me to this ("Basic Engineering for Builders"):

where it says that the steel tape should be supported throughout its span AND have a tension of 15# which to me suggests that the tape should not have any catenary curve in it. Is that correct? Because when we hand-chained things in the 1980s, it sure wasn't supported throughout the length of the tape!

Also, it seems to me that one CANNOT have the tape be BOTH "supported throughout its length" AND have 15# of tension in it...unless the surface that is "supporting the tape" has a catenary curve to match the curve formed by a tape of weight x with tension y.

I guess I'll just go with 15# of tension and call it good. Thanks again.

Thanks, Nate (and everyone else who has replied) ... your approach sounds like a good starting point.

I appreciate all the help fellas, and I think I have what I need, for now.

Pull hard enough to make the other guy say, "WHoa! I lost it." Tell him to hang on tight and do it again and mark it. That's enough tension. Stay as level as you can.

You need this combination to go along along with all of the other postings. (I took it off the wall to take the picture)

Tension Spring bar for the head guy and chaining clamp for the rear guy.

Used it last year.

Randy

Chaining Clamp AKA "Monkey's *uts

TNAI