@olemanriver Thanks, from what I've read so far, having an atomic clock in the receiver doubles vertical height accuracy. Does anyone on the forum use a receiver with an atomic clock?
AUSPOS provides a local antenna calibration service. This sort of setup would work well during night hours, when there is minimal distortion, or interference from sunlight etc.
I'm still reading up on Geomagnetism, there's a lot to process.
On another subject...
We used to set the rails on the draglines using a K&E telescope, optical square and calibrated Starrett micrometre (very long). Old tech now, but we'd do our finish machining cuts in the early hours of the morning, and aim to be finished by 4 am, to eliminate temperature influences.
We set the dragline in it's working plane, floated on jacks, with load in the bucket and grout the rails into position (or machine the upper rail pad). We'd set the dragline on its base and use a dummy pinion with optical targets set in the swing rack to align the swing bores. The engineers would carry out the roller load tests (slew bearing) and we'd have 40+ year life predictions on the rails.
The mines choose to engage people who take shortcuts to reduce down time duration (we can't compete with this and do the job properly), and as a result it's not uncommon to see roller load tests with only 7 year life. I've seen swing pinions with up to 3/4" of backlash or destructive tip root contact. The guys that do this set up their laser tracker on the ground and take their measurements during daylight hours, but it's not the laser tracker, if we were doing it, we'd weld a mount to the revolving frame to eliminate movement on the jacks, and we used a lot more jacks, but the surprising thing is some of the results, you could do a better job with a steel tape measure. I'm not joking.
In this photo, they're measuring swing bore locations.
I usually get called after things go wrong, I've only had one customer who was prepared to add 10 days to their shutdown duration to do the job properly. There are people who want to do it properly, it's just their numbers are small, or they're overridden by management, not enough to for a viable business.
Here the upper rail is inboard too far by 5/8", see the rollers sticking out underneath.
Swing pinions jammed hard into the swing rack (too close).
3 month old roller.
We did have plans of setting up two laser trackers, on a brace at a known distance apart, setting active targets on gear & pinion shafts, then slowly rotating the gearing under load, to measure the alignment of gearing, so customers could better scope their machining for their shutdowns. Another idea we had was setting up a Taylor Hobson telescope with digital targets, mounting it on a Hexapod and writing some software to auto align to bore targets, by setting the hexapod to rotate about the back target, when aligning to the front bore target. Normally this is a manual iterative process, where you get closer into alignment each time you change from the back target to the front and vice versa, until you are satisfied you are properly aligned.
The problem is management at the mines who make the decisions are only there for a couple of years before they move on, if it only lasts 7 years, that's good enough, they're long gone by the time it fails and they saved the mine a few million dollars, they leave a mess for the next bloke, their focus is minimum shutdown duration and lowest price. The other problem is when the coal price is up, no one wants to shut down their draglines for maintenance, and when the coal price is down, no one can afford to shut down the dragline for maintenance.
I'll send a few pics of how we did things.
Cheers,
Peter.
Jacking system, used to float the dragline in its working plane.
Tub machining, the tarps are there to stop sunlight interfering with laser levelling of the mill.
Swing rack segments - Cleaning and dressing (with a hand stone) any surface damage.
Hand dressing following machining, we had the swing rack trammed within 1.5 thou of concentricity. Tolerance was 20 thou. About a year prior, I had to watch a contractor tram to 30 thou, 10 outside tolerance, but it was the best they could get as they were lazy on the prep, we had to change the centre bush wear tolerance to avoid tip root contact on the swing pinions.
Laser aligning IBS rope lug install.
Cheers,
Peter.
@pfirmst yeah laser trackers with the right smr holder are awesome and so are radial arm scanners. But they have to be understood and what influences them. Having the right tool for the right job is something the metrologist has to understand. I doubt any surveyors that practice daily are using atomic frequency standards aka atomic clocks. Not cost affective for what we do. Only reason i know of them is i was an orbital scientist for a while and we used them. What software do you use for laser tracker etc. here i used spatial analyzer. Meshy and a few others depending on what i was doing etc. I wish i could use meshy for building topo surfaces somehow. But my surfaces for parts and reverse engineering were a different animal than a topographic survey
And getting yelled at by the boss, memories of when we discovered how to edit photographs.
@pfirmst geomajic I fiddled with a little. You are in a different world with those toys than what is needed for most Land Surveying task. I went from land surveying to geodetic then to metrology now back to land surveying. Took a while to get my head wrapped around the acceptable tolerances again. You will probably have a very unique understanding of least squares with your background. I had a friend that was doing some bridge work that got thrown into using a laser tracker for some tolerances needed for swing bridge parts . He almost pulled his hair out getting the terminology down as similar wording didn’t exactly translate to same meaning.
He almost pulled his hair out getting the terminology down as similar wording didn’t exactly translate to same meaning.
Good point, it's not always obvious. Topcon's Scanmaster calls the elevation angle "zenith angle", when I was running the observations through least squares I was wondering why the scanner was getting big errors with zenith angles, until I twigged that the greater the slope the worse the error was, I had to subtract it from 90 degrees to get the true zenith angle, then the errors were small. The interesting thing was the effect it had on total station observations at distance (where we didn't level), causing up to 10mm height errors.
There's always something to challenge the brain, never gets boring.
Cheers,
Peter.
