What the heck is this thing?

So, I have about 6000mi on the 2016.5 LR4 HSE. I was crawling around and exploring this beautiful piece of British steel and came across something I've never quite seen before. I've spent only a moderate amount of time under cars but all of them have, to date anyhow, been American.

Near the rear of the LR4 mounted on top of the frame near the exhaust tail pipe is a metal weight. It is shaped sort of like an inverted "U" and has a mount that permits it to swing fore and aft several degrees. I like to think of myself as a moderately intelligent man and yet, despite that, I simply cannot sort out what this contraption is or what purpose it serves.

I cannot tell for sure, since it's mounted upon the frame, but I feels about 10-15lbs. It's mounted quite solidly and not easily removed. My theories are it may have something to do with the HDC in order to determine the downward angle of the LR4 since it has fore-and-aft travel but none laterally. I don't see any wiring to or from the weights but perhaps they run internally in the frame to safeguard any wiring present.

My alternate theory? Zip. I have none. Hence, I'll turn to you wiser and more knowing Land Rover aficionados. Fire away.

Nothing that high-tech I'm afraid... They are (there's two of those pendulum weights down there, one behind each side of the rear bumper) harmonic mass dampeners / absorbers, designed to counter resonate frequency vibrations coming off the frame of the truck. They are a very low tech way of reducing mechanical frame vibrations, minimizing long-term wear and damage to the vehicle, and improving ride quality at the expense of fuel economy, handling and nimbleness.

They weigh about 40-50 lbs each, so in a bloated truck such as ours (those giant truck nutz have been there since the LR3/RRS days) they don't really affect performance much... But they are stupid dead weights nonetheless. It's like LR engineers decided to throw some concrete blocks at the problem instead of earning their money and coming up with a more sophisticated solution when this platform was designed in the early 2000s. In fairness though, they are not the only car manufacturer using them. Here is a general explanation of what these dampeners do in automotive, mechanical and building / construction applications: https://en.wikipedia.org/wiki/Tuned_mass_damper

umbertob said:

Nothing that high-tech I'm afraid... They are (there's two of those pendulum weights down there, one behind each side of the rear bumper) harmonic mass dampeners / absorbers, designed to counter resonate frequency vibrations coming off the frame of the truck. They are a very low tech way of reducing mechanical frame vibrations, minimizing long-term wear and damage to the vehicle, and improving ride quality at the expense of fuel economy, handling and nimbleness.

They weigh about 40-50 lbs each, so in a bloated truck such as ours (those giant truck nutz have been there since the LR3/RRS days) they don't really affect performance much... But they are stupid dead weights nonetheless. It's like LR engineers decided to throw some concrete blocks at the problem instead of earning their money and coming up with a more sophisticated solution when this platform was designed in the early 2000s. In fairness though, they are not the only car manufacturer using them. Here is a general explanation of what these dampeners do in automotive, mechanical and building / construction applications: https://en.wikipedia.org/wiki/Tuned_mass_damper

Click to expand...

^^^^ What he said.
Although as low tech as it may be, almost all ladder frames use some form of the pendulum/dampener weights, from the G-wagon to many modern SUVs, and trucks. I get what you saying, but time is money and this is an easy proven solution.

Well, fantastic. I've never seen that before. Thanks for the input. I had attached a photo but it didn't seem to go through.

It is nice that these weights are somewhat movable. Made it easier to work around one when installing the Atlantic British trailer wiring harness.

Sometimes ballasts are placed in vehicles to counter NVD and harmonic occurrences. These are found in many vehicles. I would not be surprised to see if this were the case.

Umbertob,
It's interesting to learn something new. Since sharing that link with me I've read a bit more about them. One of the largest of these tuned mass dampers in the world is in the uppermost floors of Taipei 101. I had occasion to see this twice while visiting Taipei on business and it was really fascinating to see. I guess it's interesting think of that being in the tailbone of my LR4.

Forty Deuce said:

Umbertob,
It's interesting to learn something new. Since sharing that link with me I've read a bit more about them. One of the largest of these tuned mass dampers in the world is in the uppermost floors of Taipei 101. I had occasion to see this twice while visiting Taipei on business and it was really fascinating to see. I guess it's interesting think of that being in the tailbone of my LR4.

Click to expand...

Interesting to see what us humans have come up with in the last 100 years. I remember getting under my truck for the first time seeing that damper, trying to figure out what the heck it was. All along thinking it was some fancy braking or body roll sensor. hahah

I tried to remove mine, but looks like a PITA has anyone removed them?