Calibration tool suggestion

I've always adjusted a rod by putting a nail in the rafters in my shed, use a plumb bob to set a drill hole in the concrete floor. I use a rod end on the top of the rod and extend it up to the nail with the bottom in the drill hole and adjust the level bubble.

I have a tribrach adjusting tool that places a second brach on top of one on a tripod, then it uses the same points I have for the rod adjustment. It works with a known good brach on the pod and adjusts the unknown on top. I've had the tool for so long I don't know where it came from anymore.

Hope this helps

Dito, Seco sells the adapter. Jp

That works great, sometimes the wood in sheds will flex and it does make a difference, they also make an adjustable piece with a hole for the plumb bob to hang down to so that you can adjust it daily.

Best tool for calibrating a rod, by far, is the ChrisNik True Plumb. I have 2 of them in my shop. One for prism poles and fixed height GPS tripods and another for doing 2m poles. Makes rod calibration into a 30 second job.

Here is a link for them ChrisNik True Plumb

For tribrachs I use the Seco part number 2002-00 It is a machined aluminum "puck" with a bubble level set in the top. Use the bubble level to adjust the bubble on the tribrach to center and then you can use the puck to stack the tribrach in question on another tribrach to check optical plummet. That and I have a target under my stand on my collimator range to check optical plummet on the guns that have them built in.

would highly recommend both..

I use the vial bubble on the instrument to check the bullseye bubble on the tribrach. I then hang a plumb bob (yes, I still have a tripod with a hook) and mark the spot with a pencil. I trace the outline of the tribrach on the tripod head, adjust the optical (if needed) to match the plumb bob point, then turn the tribach inside the marks on the tripod, and check again. Takes ten minutes, with no gadgets!

-JD-

> What's the best device for calibrating tribrachs? What's the best device for calibrating a rod?
>
> Is there any tool out there that does both? Some kind wall mounted beam/platform that could let check and adjust rods and brachs?

I don't know if it's the absolute best or not, but this simple jig is what I use for adjusting prism pole bubbles.

As far as tribrachs go, I'm in the same camp as JD Juelson.

I too use a plumb bob and drill holes if available. Where I currently am located have no place to make one (I rent)

So use the total station for my rods with my bipod. For left and right I sight and adjust and for front back I rotate 180 and keep shooting, rotating, and adjusting until I can repeat the same distance forward and reverse.

I use the same jig as Alan Cook. I have it on the wall in my office. I also use the SECO "hockey puck" with the spirit vial in it for my tribrachs.

I have a Seco level vial puck for the tribrac

Prism and 2m poles I set on a point and setup two instruments at a 90 from each other about 20ft from pole and sight for true and adjust bubbles.

Will use these same setups to fine tune tribrac with 1m extension.

Has been a good training fete for junior instrumentmen.

"Has been a good training fete for junior instrumentmen."

Exactly what I do with my guys in Nome, plus we make pegging the level a monthly ritual.
Basically, just to "peg" all the gear in the chariot
Check and adjust all the tribrachs (this also checks the vial bubbles on the TS)
Stick a puck with a candy cane in an adjusted tribrach and check the hand rod bubbles.
Use the hand rod bubbles to check the fixed rod bubbles on the prism poles, then check them as Mr. Harris does as a final check. Keeps the boys busy in the warehouse on a crappy day, and I get a better warm and fuzzy!

-JD-

I use a tribrach adapter screwed to an extension pole that I clamp to a rafter or stud or anything solid above me.
Then I rotate the tribrach 360° marking 3 points on a board below at 120°± and adjust the optical plummet to the centre of the 3 marks.
Adjust bubble against instrument bubble.

Rod I adjust against a staff bubble rotating same around pole. Quick, accurate and easy.

The method we use in our shop to adjust the OP in a tribrach is to place a plumb bob target on the ceiling above a stand or tripod. Using a tribrach-adjusting cylinder which is a machined cylinder of the appropriate diameter to fit into the tribrach and rest on the stud that the base of the total station or adapter ride on when in use, place an empty tribrach on the tripod in the normal position and insert the adjusting cylinder and then invert the tribrach to be adjusted on top of the adjusting cylinder. Using the leveling screws of the base tribrach, aim the OP of the tribrach you are adjusting at the target on the ceiling. Then rotate the inverted tribrach to check for proper adjustment.

The adjusting cylinder is in the $40 range and the one with the plate vial for adjusting the bullseye level bubble on the tribrach is closer to $100. (I am not marketing...)

Sure, but how do you calibrate your plumb bob?

I do the same. I have a target on the ceiling near my desk.

A field check is: set up the tribrach to be checked as normal over a point. Set up the TS on a tripod about 15' away and aim the target (nail or magic marker cross or whatever it is) on the ground. Look up at the tribrach and you should be in the middle of the threaded stud on the adapter (or use a prism target). Rotate the tribrach 90°, relevel and center and check again.

I field adjust pole bubbles by double reversion using a push button tripod. Then for fine tuning I check it with the total station similar to tribrachs.

I have found (prism poles) that if you turn the adjusting screws down a few turns when you get them from the SECO they will stay in adjustment and generally you will just be checking them, most of the time no need to adjust.

Here' s another field check of a tribrach, one that does not require a total station. Level the tribrach over a point. With a pencil, outline the tribrach base on the head of the tripod. Loosen the tribrach, rotate it 120degree, and clamp it exactly in the traced outline. Relevel the tribrach and you should be on the point again.

Do they make a version of the True Plumb for Leica poles or is there an adapter from someone (SECO)?

I have the very basic SECO rod plumbing fixture, but have always thought the True Plumb looked like a better idea.

SHG

I've used both and would take the simple Seco jig over the True-Plumb in a heartbeat. I found that unless you have a block or concrete wall in a protected area to install the True-plumb it will get knocked out of adjustment. If you have to get out the plumb-bob and wrenches to adjust the jig each time you use it, it takes longer to plumb a rod with the True-Plumb than with the Seco jig in my experience.