How many of you guys have had problems with your plastic legs moving when set up on hot days in direct sunlight? I am talking about high dollar Crain Tri-Max not the cheap ones. I have tried 5 sets of these with a S6 and they all go out of plumb in in a short time period while in direct sunlight. The wood legs with the screw clamp (tried 4 sets of these all old sokkia to test my theory) stay plumb about 90% better. My theory--- the hot direct sunlight makes the plastic legs loose and floppy?
I have never had any problems with either set of my Crain TriMax tripods. I use them for my robot and regular total station.
Yes, but how does this affect the RTK solution posited below......oh my word, we are going to be soooo far off!
🙁 :'( :pissed: o.O :woot:
I'm sure Kent will be along soon to tell us how lazy we are for relying upon some report of tripod stability in the Swiss Alps. I would expect there will be no direct correlation admitted between the study and a local surveyor's actual practice. After all, shouldn't we all be performing our own redundancy analysis of each individual tripod as it is erected over each point we set? I'm sure that multiple setups over each point under varying weather conditions (solar constellations) should be taken into account before we can reach the 95% confidence level to assure compliance with the ALTA requirements and Texas minimum standards.
Ya, right...:'(
JBS
I will have to say that I never had the problem before while working in the East where the sunlight is not as intense as here in Tx. ie there if you lay a hammer on the tailgate there it MIGHT get too hot to tough on a 100 deg day whereas here in Tx you are going to get burned. Also these observations are from 30 min+ very solid setups. Not the shorter setups experienced in traversing.
Have not used the Crain ones, have used a few of the Dutch Hill tripods in the past, my experience was the same, not good in direct sunlight or wind, however they were good in wet conditions because they didn't swell. I remember it was very hard to keep an instrument leveled when using those tripods.
SHG
> I'm sure Kent will be along soon to tell us how lazy we are for relying upon some report of tripod stability in the Swiss Alps. I would expect there will be no direct correlation admitted between the study and a local surveyor's actual practice. After all, shouldn't we all be performing our own redundancy analysis of each individual tripod as it is erected over each point we set? I'm sure that multiple setups over each point under varying weather conditions (solar constellations) should be taken into account before we can reach the 95% confidence level to assure compliance with the ALTA requirements and Texas minimum standards.
>
> Ya, right...:'(
>
> JBS
I would suggest rather than busting his chops you listen to him and learn something.
If you disagree with the guy, you don't have to be a smart ass about it, just don't respond or instead put forth an intelligent counter argument that will educate us all.
I for one, find his posts informative and always take away something positive regardless of the manner presented.
Jim Vianna
I use Dutch Hill tripods and I have not experienced the same issues you have. Yes, from time to time there are issues with the instrument coming out of level in direct sunlight but it only seems to be due to 1) frozen or icy pavement thawing out, taking the legs with it or 2) the pavement heating up to the point it gets soft. When these scenarios happen its time to take out the flats and put them under the tripod. I have never experienced an issue due to direct sunlight on natural soil. Perhaps due to the weak sunlight in the NE as mentioned above?
My experience was in the NW, and it has been a few years. We went back to all heavy duty wood tripods at the time, so I don't have any experience with the current products being sold, I do know that the drift was directly from sunlight on the tripod, and not necessarily due to being set up on frozen ground either.
Sounds like maybe the new models don't exhibit the drifting behavior in sunlight.
SHG
Seems there is room for a "better" solution in the marketplace.
> I would suggest rather than busting his chops you listen to him and learn something.
>
> If you disagree with the guy, you don't have to be a smart ass about it, just don't respond or instead put forth an intelligent counter argument that will educate us all.
>
> I for one, find his posts informative and always take away something positive regardless of the manner presented.
> Jim Vianna
I, too, appreciate Kent's posts when they are informative. Any time he's posting about subjects within his area of expertise, he's got important things to say that we all benefit from. I can agree that his recent posts on RTK precision (I believe there were actually two or three) were very informative. The remainder of the posts accomplished little but "bust the chops" of a few individuals with equal expertise along with the majority of the profession who uses RTK.
I stood back from the posts and kept my mouth shut as there were many involved who I recognize as having a greater level of expertise on the subject than I. I simply found Kent's comment about the "Swiss Alps" RTK study quite humorous. Apparently, my attempt at projecting the same humor has been misinterpreted. I never said anything about "disagreeing with the guy." I just disagree with his off-handed and snide dismissal of meaningful reports with meaningful data which may contradict or expound beyond his argument of the day.
JBS
P.S. I've always found that the largest factor in tripod stability has been the routine adjustments that should be made to maintain the proper tension on the legs and head. If there's a problem with stability, it's more likely that it suffers from maintenance issues. The coefficient of expansion between wood and fiberglass isn't that different.
Wood cannot handle the outdoors... swells when wet and what not.
Seco/Crain Trimax... cant go wrong here.
I am not alone in this and have found several other surveyors as well as 2 former employers that would not use plastic legs, they simply said "We use wood legs around here" I never understood until seeing it for myself in a direct comparison. And yes the legs are routinely tightened. Like I said these are long setups for construction and monitoring with a S6 as well as for an RTK base also different guns have been used so I know that its not the level bubble on one particular gun. I now use lightweight wood Leica legs for traversing and heavy wood sokkia legs for the long setups. Yes wood swells in humid environments but with the thumb screws I feel that they are still more reliable.
I find it interesting that we can purchase equipment that can measure to the nearest millimeter, and second, but we still rely on the same old legs, tri-brac's, rods and rod bubbles that have been around for 50 years. Legs were never a concern when you threw the instrument up on a set of legs wrapped a set of angles and traversed on to the next point. Now you set up on one point for extended time and wrap to everything you can possible see from that set-up, and we notice that the instrument is moving because of a lot of different factors. Good post about a relatively simple thing. We have found that if we set the instrument as soon as possible and let it get acclimated to the conditions before we start using it we achieve better results. Jp
