Hi,
I just got an old fashioned peerless lufkin engineers tape 200' long. I am new school, so I am not sure how to use it correctly. I looked up the specs for pulling tension on flat, fully supported surface. States correct tension on flat surface for 100' tape is 10lbs, 200' is 20lbs. Say if I was to pull an 80' measurement, would correct tension be 8lbs if I've got it not fully unreeled, or would it be the full 20lbs for my 200' tape? Thanks for your help in advance. I can't find documentation, and I don't want to be an idiot.
Fully suspended, something around 60 lbs. You have to compensate for sag. And, you would want the specs for that particular width, and thickness of tape.
It's been a while for me.
I like a tape claw, though we rarely used them. It's a cam pincher, so you don't curl the tape. Take a piece of paper, pull it tightly and slide it around a 90 degree corner. It'll curl it. Same thing will happen to a tape, near its ends, if you curl it. And will happen anywhere, if you pull it too tightly around a sharp corner. You can use a leather thong in the end, if you like, as a handle. The ends will crystalize, and break off, if you curl them.
It's just the way tapes need cared for. (Or rather, don't need abused!)
My dad could lecture on this for 5 min!
I can still hear it...
🙂
zac stanton, post: 369427, member: 11630 wrote: Hi,
I just got an old fashioned peerless lufkin engineers tape 200' long. I am new school, so I am not sure how to use it correctly. I looked up the specs for pulling tension on flat, fully supported surface. States correct tension on flat surface for 100' tape is 10lbs, 200' is 20lbs. Say if I was to pull an 80' measurement, would correct tension be 8lbs if I've got it not fully unreeled, or would it be the full 20lbs for my 200' tape? Thanks for your help in advance. I can't find documentation, and I don't want to be an idiot.
Do a search for:
Measurement Systems; Taping Corrections, by
Robert J. Mergel, July 2004
Columbus State Community College
It's a very cool Powerpoint presentation on everything you'd ever want to know about pulling steel tapes (plus a lot of formula that will make your eyes water). I was using it a lot until my inherited Lufkin 200' tape broke for exactly the reason pointed out by Nate (by a previous user of course).
It's 4 mb big; I can email it if you can't find it.
The tension matters most for an unsupported tape because the sag changes a lot with varying tension, particularly on a long distance. On a flat supported surface, your errors are likely to be greater for calibration ( is the tape really 200.00 feet long?, is it kinked? ) and for temperature correction (about 0.01/100.00/15 degees F. if I remember) than your errors for improper tension if you just pull it snug. Try varying the tension from just a little pull to as hard as you can pull and still be steady and you will get an idea of how big your errors are.
Very shortly as the sun rises across the country, you will get a ton of advice.
zac stanton, post: 369427, member: 11630 wrote: Hi,
I just got an old fashioned peerless lufkin engineers tape 200' long. I am new school, so I am not sure how to use it correctly. I looked up the specs for pulling tension on flat, fully supported surface. States correct tension on flat surface for 100' tape is 10lbs, 200' is 20lbs. Say if I was to pull an 80' measurement, would correct tension be 8lbs if I've got it not fully unreeled, or would it be the full 20lbs for my 200' tape? Thanks for your help in advance. I can't find documentation, and I don't want to be an idiot.
All you need to know is 0.00000645. 🙂
Kris Morgan, post: 369462, member: 29 wrote: All you need to know is 0.00000645. 🙂
That's burned in my memory, right next to "two times the radius times the sine of the deflection angle".
James Fleming, post: 369465, member: 136 wrote: That's burned in my memory, right next to "two times the radius times the sine of the deflection angle".
We use to have to remember stuff like lc=2R(sin ëü) and 5729.5778...but not anymore
zac stanton, post: 369427, member: 11630 wrote: Hi,
I just got an old fashioned peerless lufkin engineers tape 200' long. I am new school, so I am not sure how to use it correctly. I looked up the specs for pulling tension on flat, fully supported surface. States correct tension on flat surface for 100' tape is 10lbs, 200' is 20lbs. Say if I was to pull an 80' measurement, would correct tension be 8lbs if I've got it not fully unreeled, or would it be the full 20lbs for my 200' tape? Thanks for your help in advance. I can't find documentation, and I don't want to be an idiot.
No, correct tension for fully supported is whatever the spec. says, no matter how much tape is being used, as long as you are at standard temperature. When using it supported only at the end points, the sag correction formula does depend on the length between endpoints. The tension correction has to do with the modulus of elasticity properties of the steel material. They come up with this from destructive testing procedures.
paden cash, post: 369466, member: 20 wrote: We use to have to remember stuff like lc=2R(sin ëü) and 5729.5778...but not anymore
[USER=20]@paden cash[/USER]
I used all of those yesterday placing culverts from a plan onto the calculated polyline to see how well the structures fit to work out about 7000' of right-of-way.
Also, in conjuction with (Sin 1/2 delta)*2 = LC, I worked backwards with delta/Degree*100=L all using the degree/5729.578. Then, just for kicks, I calculated the BB intersection angles from known corners using law of cosines.
It's faster for me this way, and if I'm anything, I'm a model of efficiency (at least in my own mind). 🙂
James Fleming, post: 369465, member: 136 wrote: That's burned in my memory, right next to "two times the radius times the sine of the deflection angle".
Is that two times the radius times the sin of half the deflection angle? Or are you talking about something else?
Tom Adams, post: 369489, member: 7285 wrote: Is that two times the radius times the sin of half the deflection angle? Or are you talking about something else?
The deflection angle is half of the delta in the colonial states 😀
James Fleming, post: 369491, member: 136 wrote: The deflection angle is half of the delta in the colonial states 😀
You got me. I was (obviously) thinking of the delta angle that is the deflection of the tangent lines. But the deflection of the curve is the tangent to the cord.
James Fleming, post: 369491, member: 136 wrote: The deflection angle is half of the delta in the colonial states 😀
I think geometry is the same in all States. Delta is an included angle, not a deflection angle. Although I guess delta could represent anything you want it to. Screw it, I'll go with James, colonial states are most correct:)
Tape calibration is by NIST is 50 newtons, 20å¡C, fully supported. Independent of length.
A 300' tape, 50 N. Fully supported; 11 lbs pull.
At longer distances tension errors return more easily observed error.
And I've never seen 10 lbs for 100' and 20 lbs for 200'.
Do you have a link for that?
10 lbs and 68å¡F is about the same as 20 lbs and 64å¡F. But independent of length. And in catenary it's much much harder, and tension of 0.5 lbs can be noticeable. The formula for catenary is not simple.
I use a fish scale and chaining clamp. A good sporting goods shop had them, not too much $. Makes a big difference, if 0.03' matters.
20lb is the minimum pull be at 10ft or 200ft.
The headchain I followed claimed that you could never pull too much, only too little.
When the chaining pin fell in someplace where you had an awkward stance, he enjoyed testing your metal.
A Harris, post: 369547, member: 81 wrote: ..The headchain I followed claimed that you could never pull too much, only too little...
I took my responsibilities as a tail-chainman seriously. Although we carried a tension scale, we rarely used it. But I had a pretty good damned idea what was too much.
I wish I had tail-chained behind the fella you mentioned...I'd let him get about 99% of his pull, then let go...;-)
Fully suspended or flat?
You can pull too much. A chain has a correct tension, not 'can never pull too hard' tension. A 300' chain can be off 5/100 above 30 lbs.
At the top of the thread was stated 10 lb at 100' and 20 at 200'. That's misinformation.
And correction formula include pulled tension v calibrated tension. If calibrated at 10 pounds, you pull 20, the formula calculates the delta. And that's fully supported, if you expect chain distance to agree with EDM distances. Which is per the link you included.
It's a mature science, lots of docs by NGS NIST and universities.
Larry Scott, post: 369553, member: 8766 wrote: Fully suspended or flat?
You can pull too much. A chain has a correct tension, not 'can never pull too hard' tension. A 300' chain can be off a 1/10th above 30 lbs.At the top of the thread was stated 10 lb at 100' and 20 at 200'. That's misinformation.
And correction formula include pulled tension v calibrated tension. If calibrated at 10 pounds, you pull 20, the formula calculates the delta. And that's fully supported, if you expect chain distance to agree with EDM distances. Which is per the link you included.
It's a mature science, lots of docs by NGS NIST and universities.
Not necessarily misinformation. The company may have calibrated the tape, sounds like company specs the poster is mentioning. There's no mention of calibration by NSIT. Also possible the longer tape was made with a larger cross sectional area, hence they used a harder pull in calibrating. But, could be misinformation as you say.
And, it's all theoretical anyway at this point. The poster should have it calibrated to see what pull it now requires in the controlled atmosphere. Could be much different than when it was first made.
He describes one chain, not two. And different tensions at 10 lbs at 100 ft v 20 lbs at 200 ft. And was asking if that means 8 lbs at 80 ft. I have never seen that in any reputable doc. Please link a doc that describes length dependent tension fully supported.
And, I guess it's project requirement specific. If you only need 1:5000, or if you need to be 1:25000 in 500-600 ft. And will another company measure across your work looking for a couple of hundredths.
Layout a bridge abutment with chain and consider what 0.05' is worth.
