Sunday, June 28, 2020

Report on T-post driver

I wimped out and simply took video of the testing. No analysis.


Fourteen second video. Driver still ringing after eleven seconds. The sound is very bright, very loud.


Eleven second video. Damping applied to outside. Damping is 2mm of butyl rubber, a material known for energy dissipation and it is held on with radiator clamps. Three bands were installed. One at the opening (bottom in the being-used position), and one each next to where the handles are welded to the body of the driver.

The handles are involved in many of the modes. I know this because I can change the sound characteristics of the ringing by how tightly I grip the handles when driving posts. I suspect the handles are beating like butterfly wings in that mode and "pumping" the sides of the driver. That is why I chose the positions I did.

The most common source of butyl rubber is bicycle inner tube. Each layer is about 1.0mm thick.

This option worked better than I expected.


Runner-up: T-post driver with a 1.25", two-pound steel weight added to the impact surface. The weight and the driver are separated with a 3mm butyl piece.

This did not work as well as I thought it should but did slightly better than the exterior damping.

The steel weight came from This Supplier. The butyl pad was made by gluing layers of inner tube together. 

While the over-all reduction was pronounced, the driver continued to ring after the impact. Touching the handles damped out the ring so it was clearly a handle mode.


Overall winner: T-post driver with 2 pounds of lead shot and oil added. In the interest of expediency, I did not weld on a cap. I turned the driver upside-down (from being-used position) and poured two pounds of #8 lead shot into the driver. Then, I impacted the outside of the impact surface.

Two pounds of shot was used because the steel hockey-puck weighed two pounds and I wanted an apples-to-apples comparison.

The experiment was repeated both with and without oil. I didn't notice any difference.

Repeat of the baseline, unmodified post driver.

All three strategies made marked improvements to the sound level and duration.

Apologies for the shaky video and lack of analysis. I wanted to get the monkey off my back before July started.

8 comments:

  1. Plus you'll find the shot to drive better, as well as being quieter.

    The oil will keep the shot from sticking together and will be the better option in the long run.

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  2. You're getting a harmonic resonance off the handles... sigh

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    1. I think much of that will disappear when I have hands on the handles. In the interest of trying to make the experiment repeatable, and due to only having two hands, I suspended the driver as shown.

      Some problems fix themselves.

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  3. Ya man! Dead blow with noise dampening is the ticket.

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    1. Fred, that sounds like...well...necrophilia.

      You did mean "dead blow hammer?"

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  4. Joe, not understanding. You added shot and oil to the head of the drive chamber - how would you keep that in place, or were you just testing for sound dampening?

    Suggest you get some Scotch tape #130C, rubber splicing tape, 30 ft. $12. You wrap your handles with this, stretch the tape slightly as you go and it activates and will fuse to itself into a single mass. Good for grip and will dampen out the vibes.

    Just got one of these myself from Lowe's and it's got some kind of plug already installed at the head of the chamber.

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  5. Sorry - meant to ask: How much does your version weigh?

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    Replies
    1. I was just testing for sound.

      I deemed it expedient to apply the impact on the outside of the end as-opposed to the T-post impacting the inside. Likewise, I flipped the driver mouth-up so it was like a big cup and put the shot-and-oil inside the driver instead of in a separate chamber on top of the driver.

      Again, it was a matter of expedience.

      I am probably going to cut the solid, steel hockey-puck off the outside and wrap with enough bicycle inner-tube to make it a snug fit on the inside. Then I will ram it down the hole.

      I also intend to add a single wrap of inner-tube on the body of the driver below where the handles join the body and attach with double radiator clamps. I have all the parts. I might as well get what benefit I can.

      Thanks for commenting. I will weigh the driver when I get a few minutes.

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