My Terrible S7 came with a tribrach which didn't have an opt. plummet, so I bought one and have been using it since.
Today the locking knob Broke. (See pic) is there any way to repair it or should I buy a new one?
I'm thinking of replacing the broken locking mechanism with the one from the original tribrach. Has anybody done it before? I'm still able to lock the instrument pins on the tribrach by rotating the parts underneath but I'm worried about it not locking tight in place.
On buying options, there are original Trimble one for around $500 and a Seco European-Style Tribrach with Optical Plummet - 2152-05-BLK for $183, what the deal? am I missing something hear?
Sounds about right.
We had a rule-of-thumb at my last employer...
"Take a fair price and 'trimble' it!"
Do yourself a favor and buy a Leica tribrach. The Trimbles seem to be an overpriced Seco style. The Leica GDF322 is around $600 but far more stable. Why spend all that money on an instrument only have it sit on a inferior tribrach and legs. I'm amazed at how many Trimbles I've seen with green tribrachs.
Some of the green ones last really really well - especially if continually exposed to the weather - like in monitoring. The coating flaking off and the metal corroding is a common problem with the cheap(er) units
You can easily dis-assemble a tribrach and swap parts; it may be an enjoyable task for a rainy day, but not a good use of your time. I have torn down and re-assembled every brand of tribrach, and the return on time investment was rarely worth the results.
Just get a Leica GDF321 without plummet and don't look back.
The plummet in any total station is superior, and stays in adjustment.
Tribrach adaptors "carriers" with plummets can be checked and adjusted in the field at any set-up.
The leveling screw mechanism in a tribrach is more complex than it seems from the outside. It needs to hold the screws to the upper plate of the tribrach with no play, but allow the threaded action to move smoothly. The foot of the screw needs to be able to tilt and slide radially, with no motion in other directions.
Leica tribrachs have a brass block that slides in a little track, with a single ball bearing in a point on the end of each leveling screw. This is held in place with a spring plate that tensions the screw through a collar with a ring of tiny ball bearings.
The result is the Leica tribrach will last a lifetime, with no rotational play to throw off your total station angle accuracy. (all bets are off however, if you drop it and dent the bearing races)
Cheaper tribrachs lack the slide block, or lack the ball bearings, or the mechanism is roughly made. Without ball bearings, wear in the leveling screw mechanism will eventually allow play that will negate the accuracy of your total station.
Dittos on the Pro level Leica tribrachs. There are none better. The extra up front cost is well worth it. Cheap in the long run.
Note that Leica also sells cheaper, more pedestrian tribrachs under its brand name that are no better than what you have.
Most of the places I've worked have left the tribrach attached to the instrument. You have to buy an extra tribrach but then you don't have to mess with the lock.
One more detail to watch out for if you are mixing brands of equipment....
All tribrachs have 3 little bumps in the surface of the socket that the total station rests on, creating a reference plane for repeatable vertical location.
All tribrachs have a circular opening with tapered sides that guide the base of the total station into a repeatable horizontal location.
Some Leica tribrachs of different ages have a small ridge or step at the bottom of the circular opening that is not exactly co-planar with the 3 bumps.
All Leica total stations and tribrach adaptors have a beveled edge on the bottom that will not contact the step when seated in the tribrach.
I have encountered some older Sokkia instruments and Seco accessories (most notably the tribrach adjusting cylinder) that have a squared off bottom edge; this causes them to improperly seat into a Leica tribrach. I have notified Seco, not sure if they fixed their design.
Any instrument or accessory can be easily beveled lightly with a file if you have this problem.
Thank you guys, I purchased the Seco European-Style Tribrach with Optical Plummet – 2152-05-BLK
before I read all you comments. The last one (Trimble) lasted 7 years.
The type of tribrach for robotic instruments matter. Years ago I was at a company and we bought several tribrachs and used them interchangeably with the ones that came with the robots. Many of the ones we bought had the locking pin break because the whole locking mechanism get out of whack because of all the rotation. So the Wild style that Trimble robots come with are good. And since then Trimble bought a company that makes tribrachs, so they essentially make their own now. And by the way, when you buy a Trimble robot, you can have a tribrach come with it that has an optical plummet for about $200 more. Just specify with your vendor when discussing details. I have done that.
On the repair, all depends if you have a local supplier that does repair. I might guess $150 for that repair which would probably include a clean and calibration. If you buy a new tribrach, you're going to have to check/calibrate it yourself because you're going to get a new one right out of the manufacturer's box.
