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How to set tacks with plumb bob for pole calibration
Posted by J Philpott on November 22, 2014 at 9:58 amCould somebody please describe how you set tacks/nails to calibrate a prism pole bubble in a door frame using a plumb bob. I see it mentioned here that it is a frequently used method. Thanks.
brad-ott replied 9 years, 5 months ago 12 Members · 12 Replies- 12 Replies
J,
Here’s a post on that topic:
[msg=279762]Template for Rod Vial Adjustment[/msg]Dave
Or you can buy one of these:
http://www.hayesinstrument.com/cgi-bin/webc.cgi/st_prod.html?p_prodid=2135
Which I found pretty useless. Mine is mounted outdoors where it’s slowly rusting its way to the dump.
I went down my basement and drilled a small dimple in the concrete floor. Then used a plumb bob to measure a point directly over the dimple in a door frame. Then drilled a 5/8″ hole about 1/2″ deep in the door frame. I can then set a prism pole securely between those two points to check the bubble, rotate it around for double check, and adjust it if I want while it is held securely in place. Cost? – nothing!
I was waiting in traffic a couple weeks ago for a scraper to clear the road and saw a fella with a GPS rover carrying a tripod. Curious, I pulled over and watched from about 30 meters away:
He set the tripod down, stabbed the pole into the hard packed clay.
After leaning the pole on the tripod he carefully adjusted the tripod to make the pole plumb.
Then he spin the rod 180, adjusted the bubble, check, recheck, minor adjustment, recheck.
Then spun it 90 and followed the same procedure.
Several rechecks and he was done in about 5 minutes, put the tripod into his pickup and went back to work. I pulled back into traffic and went on my way.
I think that should work just fine. Thinking out of the box.Basically what Peter said. No fancy gizmos or tacks required. Lean up against a hard edge (table, workbench, etc.). Adjust bubble until level all the way around. I use the seco stedi-rest that I got free with a purchase of something else mounted on a tripod.
I’ve found it is easier to work from the top down. I screw an eye screw into the top of a door frame or rafter and hang a bob from it. Adjust the bob so that it is barely touching the floor. Drill a small divot in the floor. Remove the eye screw. Place a point on the “top” of the rod and wedge it between the holes. Same idea, but smaller holes.
Ditto. I used to do the door entrance and two tack trick, but now I use one of these. Set a tripod low and offset to a control point with a dimple, attach the stedi-rest and prism pole, plumb the pole and rotate 180. Adjust bubble if needed and recheck. Turn the pole 90 and do again. Easy, cheap, quick and can do it in the field anytime.
My first surveying company had one of those deals setup. They tried to show me but I never really got it. We also had one of those wall-mounted jigs which I became good with. Unfortunately too good. The boss decided he was going upgrade all our rod bubbles. I honestly don’t remember but it was something like replacing a 10 second bubble with a 2 second bubble. (like I said, I don’t remember but something like that). I got tasked with that job. I didn’t mind. Made me feel important in a way. I was the over-educated 40-something year old green horn so what did I know.
That’s ok. I showed them a little something when they kept sending me to mud pits. 🙂 It was all good.I agree the bottom piece of that kit is useless. What I did was mount the top piece on a wall, then marked a spot on the floor that would be close and drilled a pilot hole for a PK nail in the concrete floor. Once the nail was set the fine tuning of the top piece screws took a bit of time but now it is ideally set up for a quick check, IMHO.
Jacob
Jacob WallWe work from the top down . Put a tac in the upper door frame . Hang plumb bob .drill hole in floor .
We take off prism and screw a pole tip in the top of the pole as well.
Turn four ways adjust . We do it every wed or every new big boundary.I ended up just putting a tip on the top of the pole, extending to the top of the door and levelling. Rotate 180 and adjust the bubble halfway. Repeat over and over covering all quadrants.
Thanks for the replies.
> I ended up just putting a tip on the top of the pole, extending to the top of the door and levelling. Rotate 180 and adjust the bubble halfway. Repeat over and over covering all quadrants.
>
> Thanks for the replies.:plumbbob: :gammon: :good:
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