TITLE: Building adjustable tree mounts for camera traps
DATE: 2022-03-15
AUTHOR: John L. Godlee
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In the SECO Project we want to monitor seasonal patterns of leaf
production (phenology) of trees and understorey plants in savannas.
Most of this work is being led by Patricia Morellato and a
post-doc, Desirée Ramos, both based in Brazil. They have been
developing a system for monitoring leaf phenology using camera
traps, the same kind that one would use to monitor animal activity.
The camera traps are set to capture images every hour during
daylight hours, facing towards either a grass sward or looking down
over the top of a tree canopy. The images can then be analysed to
ascertain how green the vegetation is. Using cameras to monitor
phenology will help us to separate the phenological signal of the
trees and the grasses, which is difficult to do using aerial or
satellite imagery.
[SECO Project]:
https://blogs.ed.ac.uk/seco-project/
[Patricia Morellato]:
https://fapesp.br/5972/patricia-morellato
[Desirée Ramos]:
https://www.researchgate.net/profile/Desiree-Ramos-3
Up to now, the cameras have been mounted on large tower scaffold
structures called flux towers, which measure atmospheric and
weather conditions using various sensors. These towers are
expensive to set up however, and are quite rare, especially in
southern Africa where I work. I have been thinking about ways to
attach the cameras to the upper branches of large trees, so that
they can look down on the main canopy below at an oblique angle. I
came up with a design for an adjustable tree-mounted support. The
mount needs to be made of metal, as plastic will become brittle in
the sun. The mount also needs to be very solid, as we aim to leave
these cameras in place for a whole year.
[flux towers]:
https://en.wikipedia.org/wiki/Eddy_covariance
Parts I used:
- 3x M10 washers, 30 mm external diameter
- 2x 1/4" UNC eye bolts, 120 mm shank length, 15 mm eye diameter
- 2x 1/4" UNC nuts
- 2x 1/4" washers, ~15 mm external diameter
- 1x M10 split-ring washer
- 1x M10 flanged head nuts
- 1x M10 set screw, 60 mm length
- 1x large worm clamp/hose clip
Note that the M10 bolts, nuts and washers were chosen because the
M10 bolt fits through the eye of the eye bolts. This could be
altered to a different size depending on availability and the
particular eye bolts used. I chose a 60 mm long set screw because I
wanted to be sure I had plenty of excess length, but in reality the
length of the washer, eye bolt, head nut stack is only ~30 mm, so I
could have got away with a 40 mm long set screw.
The eye bolts need to be 1/4" UNC thread. This is because the
camera traps I am using, along with most other camera equipment,
use that thread size to attach to tripods and other mounts.
The eye bolts are only 120 mm long because I couldn't find any
shorter bolts with the correct thread size. In the UK at least,
it's quite hard to find imperial threaded bolts. I will cut these
bolts down to about 60 mm with a hacksaw, then re-thread the ends
to get rid of any jagged edges.
The size of hose clamp needed will vary depending on the size of
the tree branch where the camera is mounted. I chose clamps with
diameters: 40-80 mm, 70-120 mm, 110-170 mm.
You will also need a power drill to drill a hole in the hose clamp
to fit the end of the eye bolt through it.
The split ring washer helps to keep everything tight by creating
friction between the flanged head nut and the first washer. I
experimented with putting split ring washers between the eye bolts,
but the washers I had were too small.
