Is there a Quick and Simple Tripod Test?
One of the most overlooked part of any Surveying Equipment Kit is the Tripod. The Tripod is the foundation on which your Automatic (Dumpy) Level, your Theodolite or your Total Station will be mounted on. If your tripod isn’t sturdy enough to adequately support the survey equipment you need it to, then the potential accuracy you can achieve will be greatly reduced. If the tripod is not maintained or checked then the consequences could be expensive.
How much movement is in a good condition tripod?
In the video below I have set up a Leica TCRP 1205 total station. I have selected the internal levelling system. I have then applied decent pressure to the head of the tripod so that the internal level bubble moves. This tripod is in good serviceable condition.
What does a poor condition tripod look like?
In the video below is a tripod that is in poor condition. This tripod was being used by an engineer for setting up a robotic total station. Using know good control he was unable to achieve a good 3d quality resection. The total station was not at fault, it was the down to the tripod. Fortunately the total station didn’t fall over but this tripod could have failed. This tripod was only about 6 months old at the time. You should carry out the tripod test regularly.
How to check a Tripod.
This is a quick and simple test (the tripod test) to check whether your tripod is up to the job of supporting your Survey Equipment. It works for all tripods no matter the size or the materials it is constructed from. If your tripod doesn’t pass this simple tripod test then your tripod will not adequately support your surveying equipment and will adversely affect the accuracy of your surveying equipment
The Quick and Simple Tripod Test.
- Take the tripod you wish to test into an open area where you can freely extend the legs fully.
- With all the legs together, extend the legs of the tripod to their working height. (This should leave between 25mm(1inch) to 150mm(6inches) of travel left to fully extended).
- Raise one leg of the tripod to a horizontal position (holding the other two legs of the tripod vertical).
- The horizontal leg of the tripod should just be self-supporting and should be able to be pushed back to the vertical position with the lightest of touches.
- Repeat the above test for each of the legs of the tripod.
- If a leg of your tripod does not support itself in the horizontal position then the tripod will not be stable enough to support your survey equipment and will not allow it operate to its full accuracy.
The above tripod test should be carried out at least monthly, however you should be able to feel if a tripod is loose during the setting up phase. Also, when setting up the tripod you should examine the milled face on which the survey equipment is to placed on. If this milled surface has been damaged, then setting up any survey equipment above a known point will prove difficult. It is easy for this surface to become damaged as the aluminium used for the tripod head is a soft metal. This is why it is important to keep the tripod head protector on when not in use.
If you can’t tighten up the legs of your tripod or they keep getting loose then it is time to buy a new one. If you are using your tripod for Automatic (Dumpy) Levels then you can buy an aluminium one like this one that I found at a good price on Amazon. But, if you are using the tripod for a total station or a scanner then I would only buy a wooden or composite one like this one.
At the bottom of the page you will find some recommended tripods for different types of surveying equipment. Or you can always call or buy from your local survey equipment dealer if you wish.
Why do the screw clamps come loose on a Tripod?
It’s annoying when you pick up a tripod only to find one or all of the legs extend. You are sure that you left them tight when you packed them away the previous day, but there they are extended, or have just spiked your foot. Why is this? Well it is all to do with the expansion and contraction rates of different materials. When you collapsed and put away your tripod it was probably at the end of the day, at this point the Tripod has slightly expanded due to soaking up the warmth of the day and the sun. During the night, the tripod will have cooled and so contracted, hence why the screw clamps are loose. This is true for wooden or composite tripods.
If you have an aluminium tripod then you may well find that the reverse is true. You have great difficulty in undoing the screw clamps in the morning. Again it is due to the expansion and contraction of the materials.
Recommended Tripods for Surveying Equipment.
Automatic (Dumpy) Levels.
Theodolite and Total Station Tripods.