Every now and then we learn something when it isn’t expected. This just happened to when testing the stiffness and damping of the Jobu Design Killarney tripod. The Killarney has a unique design for the feet. Instead of feet that screw in via a standard 3/8″ thread, a solid metal spike is glued to the bottom leg tube and then a rubber cap is placed over the spike for normal use, as shown below:
This rubber cap fits somewhat loosely. So to make sure that I was getting the best possible performance out of the tripod, I removed the rubber caps and tested the tripod with the spikes on the concrete floor. The results was a shockingly low amount of damping in the tripod.
Here is the damping and oscillation curve for the tripod with the rubber caps:
The damping here is poor, but not outside what I have seen in other tripods. Now with the spiked feet:
Note the difference in time scale. The damping is about half, all the way down at 0.082 Js/rad. This is beyond the point of being bad and actually becomes really cool. Nearly half a minute later after the initial excitation, it is still vibrating. Often, designers want as little energy loss in an oscillating system as possible, such as when building a clock. You want the clock to run for a long time without needing to be wound up again. For tripods though, we want the opposite, for those vibrations to damp as quickly as possible.
By removing the rubber feet, we have removed a major source of energy loss from the system. The small amount of rubbing between the spike and the rubber, and the rubber and the floor, was accounting for about half of the damping in the system. The sharp point of the spike directly on the hard concrete floor of my garage removed all of this friction and thus damping. Note thought that the stiffness of the tripod increased slightly from 1308 to 1353 Nm/rad. This increase in stiffness is likely not worth the massive loss in damping observed though.
I don’t mean to imply here that spikes are worse than rubber. The story would probably be very different on a softer surface where they spike could actually embed itself somewhat into the ground. Testing this further is on my to do list, but currently my test setup is confined to the lab, so it won’t happen soon. We can probably safely conclude that spikes are not the best solution for use on firm surfaces.
This also tells us that the feet of a tripod can make a big difference in the damping performance. I didn’t expect this as I have typically seen only marginal differences in the performance of the system based on foot type. Here though, the Jobu Killarney has so little inherent damping to begin with that the damping effect of the feet is amplified. This piques my curiosity as to whether a foot with exceptional damping performance is possible.
- Apparently the choice of foot on a tripod can have a big impact on its damping. This could be an interesting avenue for further research.
- Probably don’t use spikes on hard floors.
- How much does damping even matter anyways? Working on it, stay tuned
- What are the best feet for different types of surfaces? Concrete? Dirt? Grass? Sand?
- Is it possible to make a foot that adds a lot of damping without any loss in stiffness?
7 thoughts on “Rubber and Spiked Foot Damping on the Jobu Killarney”
I hope you’re going to test how much th
e different kind of feet do impact stiffne
ss and damping.
I’m shooting the 800mm on the PMG ful
l Katana and a series 5 Gitzo.
The latter is equipped (standard) with s
piked feet with rubber caps which do ne
ed a lot of effort to remove them so I go
t long spikes (Leofoto) with a screw on
protector cap, but it’s very hard materia
Guess they’re even worse than the short
spikes you tested, so I’ll put the original
feet back on.
Thanks, love this site.
I have briefly tested the effect on the type of foot for hard surfaces. It is reasonable to expect different results on different surfaces.
There are a variety of damping feet available for
different industrial uses, could be fun to play
around with a few.
Or maybe I could wrap my tripod in Sorbothane
The ancient Bogen/Manfrotto adaptable 3/8″ tripod feet worked perfectly. The male foot threads into the
lowest leg segment female threads Thee is a concentric rubber ring on the foot which can be rotated down to
contact the floor, or rotated ujp to expose the metal ,pointed spike, hence is useful in any environment. The
adapable feet work well on carpets, polished wood, concrete or dirt/sand/irregular ground. They originally fiit
my ancient Manfrotto 3221 and 3001 tripods, which are usable but I now use more recent vintage CFand
aluminum Benros and the venerable Manfrotto Carbon One, The adaptable feet (above) are better than
anything now sold, but no longer available from Manfrotto, unless you know of a source. I very much liked
y0ur tripod ratings column but hate to abandon my menagerie ( not in your comparison)for the superb
functioning models you list. They may be no better than what I have. Also, IMHO the flip locks are faster,
easier to adjust , and reliably locked while the twist locks are not ‘fail/safe.”
Any of your thoughts would be appreciated.. Thanks.
I wonder if the damping can be applied in a different way other than the feet. In a carbon
fiber tennis racquet, players sometimes add a foam widget in between the strings to
dampen the feel of the racquet. So would a foam grip on the tripod help dampen it? Or yet,
a rubber weighted pendulum attached below the base act as a counterbalance to dampen
This makes me curious about the “rock claw” foot offered by RRS and others. I’ve never used them, but always
wondered if they would be useful, especially because rocks can be slick in some situations. I have second
thoughts after reading this since the rock claw is a stainless foot for hard surfaces.
Yeah, I’ve never quite understood the rock claw. Seems like the damping wouldn’t be great.