Dock Springs Info Page

Dock Springs are made with new truck springs of the proper size and strength and solid steel round bar forged into shape.

Forged right here on Lewis Smith Lake in Cullman Alabama with my two hands and fire.

By me, Jon Grigsby, retired police sergeant, commercial sport shooting range owner, where I have designed, fabricated, and maintained hundreds of steel target systems. I know a little about making bulletproof things.
See foprange.com.

Coil spring dampeners are not a new idea.
They have been around for quite a while. The idea is simple. They are effective at helping your dock's anchor system live in a dynamic environment by absorbing shock and impact loading. The pair I have on my dock were made about 40 years ago by a neighbor who used to be a dock repair guy on my lake but is no longer in the business. I had a conversation with him about the springs he installed on my dock. He told me that every storm that came through tore the dock up until he made the coil spring dampeners and installed them.

I recognized the value in what they did and being handy in the shop, cobbled together a few sets for neighbors who were having problems and needed them. They urged me to make them for everyone. Seems like a good idea so here we are.

I made this set about 8 years ago. Still working like new.

What makes dock springs necessary?
I like to think about it like this... Your anchor is set in a couple hundred pounds of concrete on the shore. Feels pretty dang solid. If you apply pressure to it gradually up to the load limits of your winch, cable, and mounting hardware it will be just fine. Now if you were to take a huge hammer and swing it hard enough to generate the same level of force as the max pull described earlier, the anchor is going to get loose in the ground and pull out or bend over and shear, the winch mounting bolts can shear, the gears and spool locking pawl can strip, the winch frame can distend until the gears no mesh up and release all the cable on the spool, the cable clamps can slip and release the cable, the cable can break, or welds gluing things together can break. Your dock is the big hammer here. Every time it takes up the slack in your cable, it hits all the anchoring parts with the energy created by its momentum over a very short time creating a shock load on your cable and impact load on your hardware.

Another relevant analogy... Ever use a hammer to drive a nail into a piece of wood. If you were to place the hammer on top of the nail and push as hard as you can, you might dimple the wood with the tip of the nail but its not going in. Now swing the hammer and tap the nail. It goes in. This is an impact load on the nail caused by the momentum created kinetic energy of the hammer in motion. Again, your dock is the hammer. Dynamic loads (shock and impact) break docks. Static loads they can handle. Dock Springs mitigate dynamic loads. Its physics. Its math. The math is right.

For fun, I had Grok work through the following problem...
A hammer is used to drive a nail into a piece of lumber. The hammer is a common 16 ounce claw hammer and the nail a 3 inch common non ringed construction nail. The wood is common spruce 2x4. What is the formula for measuring the force of the hammer on the nail?

The force of a hammer striking a nail can be calculated using Newton's Second Law of Motion, which states: F = m × a
Where:

F is the force (in Newtons, N)
m is the mass of the hammer (in kilograms, kg)
a is the acceleration of the hammer at the moment of impact (in meters per second squared, m/s²)
The average force of a 16-ounce claw hammer moving about as hard as you would be able to swing it striking a 3-inch common nail into a spruce 2x4 is approximately 1087 Newtons (or roughly 244 pounds of force), assuming a swing velocity of 12 m/s and a contact time of 0.005 seconds.

So a 1 pound hammer can make 244 pounds of force for .005 seconds.

I had Grok change the contact time to 4 seconds. This would simulate a dampener on the hammer similar to a coil spring dampener on a dock cable. The math says that 244 pounds of force on the nail is now .31 pounds. Its just a push and completely ineffective at driving a nail into wood.

Time. Time is the deal. A coil spring dampener adding time to the impact of your dock's motion being stopped by a cable reduces the energy to a much lower level. To a level that the anchor system can live with.

This was a 2nd failure. 1st one pulled the pole out. Neighbor and I put it back with 1400 lbs. of concrete. Wasn't enough. A dock in motion has big energy. It is now held in place with 11 tons of concrete and has Dock Springs. Go big and add coil spring dampeners.

Dock Spring catching my dock in a 50 mph breeze

Here is one of my dock springs eating a big gust of wind. It is doing its thing.

A spring mounted on your cable will absorb that load and spread its application to your hardware over the span of greater time. Watching my dock springs work in a storm, seeing the spring compress solid, opened my eyes to how much energy the wind and current really has on my dock. In a heavy storm, I observed that the spring took more than 10 seconds to reach a state of solid compression. At solid compression, it was up to the rest of my hardware to hang in there. The dock springs gave my dock a fighting chance of surviving high winds and the dynamic loads they create.

Availability...
They are not available anywhere else on the planet that I could find. You either made them yourself if you were handy and had some metalworking skills/equipment or you paid someone with metalworking skills/equipment to make them for you.

That being said, I want to be your dock spring fabricator. I have now made hundreds for dock owners who were having problems with dock survival. Upon deciding to enter into this business, I spent months searching for proper components needed. I found 3 types of truck springs that will work as intended.

Light Duty Dock Springs. 600 pounds per inch constant compression rate
Progressive Rate Dock Springs. They start at about 1000 pounds per inch of compression and the rate goes up as the spring is compressed.
Overkill Dock Springs. 2100 pounds per inch compression rate but with 1 inch diameter compression rods instead of 3/4 inch because overkill is underrated. This is the strongest set of dampeners I make. I also refer to this set as the "Ozark Heavy Duty Dock Springs". I began making these for dock owners on Lake of the Ozarks who told me stories about what they were having to deal with there. Bigger is better and Overkill is under-rated.

To determine the strength of an automotive spring I searched manufacturer's web sites for spring specifications. None list a compression rate. I use the data available from the automotive coil spring manufacturers, plugged the numbers into a custom coil spring manufacturer's calculator and shazam!... I had real world numbers based on them making a duplicate spring for me. However, they wanted about $490 per custom made spring so the automotive parts suppliers will be the better source.

The difference is the thickness of the wire used for the spring, the number of coils, how tight the coils are arranged, and the outside diameter of the spring. The progressive rate spring in a vehicle gives a softer ride but resists bottoming out with its tighter coil structure on one end. Constant rate springs are just that, have a constant compression rate.

Below is an example of this info.

Spring rate web page. Research was done.

New springs are not cheap but will ensure long, consistent, and reliable performance. I could use junk yard springs but most will have fatigued from use under a heavy truck and have an inconsistent spring rate. I looked at having springs made just for this application but found that would be cost prohibitive at several hundred per spring. Auto manufactures ordered hundreds of thousands of each spring produced and OEM quality replacements are pretty reasonable.

$500 for a pair of Dock Springs is also pretty reasonable when you compare it to having a dock repair company come out and fix your broken walkway and anchor hardware. If your dock breaks loose and takes out your neighbor's dock, you are responsible for fixing their dock too. Installing a pair of Dock Springs is something most dock owners are capable of doing themselves. I have included installation instructions on this site with tips on making it easier.

You can pick them up here at my shop or I can ship them to you.

A pair of the Light Duty springs ready for building.

They are not available from any other source I can find. Your choices are to make them yourself or have them made for you at a fabrication shop. I want to be your dock spring fab shop. Every time I go fishing on the lake in my back yard, I see a few more docks that broke in recent storms. All have anchor system failures. There is a need. There is no better solution for helping your dock live through a bad storm and survive the pounding that large wind and wake creates.

Here are a couple of jigs I made to build Dock Springs.

I build them in 3 sizes. Click on the images to go to info pages about each.

Light Duty

Progressive

Overkill HD

Dock Spring comparison: Light Duty, Progressive, and Overkill HD.

Each pair will ship with new 3/4" anchor shackles so you won't have to hunt down a set for your installation.

I hope that I have given you enough information for you to make an informed decision about this method of enhancing your dock's anchoring system. I am available at 205-966-2137 if you have questions. If you want a set, they are available through the store on this site or through stopping by my shop and picking them up in person. Shipping anywhere in the country is going to eat $100 easily as they are pretty heavy.

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They are ready and waiting for a new home..
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