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profdant139's avatar
profdant139
Explorer II
Jul 26, 2014

Tripod support for too-short stabilizer jacks

Since I flipped my axles for extra ground clearance, my stabilizers don’t reach the ground; I usually bring a stack of big wooden blocks to make up the difference. But the blocks are a little bit unsteady. So I made some collapsible tripods, and they really get the job done.

They are 16 inches high, with legs made of 1 3/8” closet pole dowels. Both ends of each dowel are rounded. The base is made up of four pieces of 8x8 3/4” plywood squares, screwed together to make a block three inches thick. Using a 1 3/8” Forstner bit and a drill press, I drilled three holes in the block, angled at 30 degrees. The legs slip into the holes, and the whole thing is easily disassembled for storage and transport.

Here is what it looks like in action:



Here is the bottom of the base block, showing the slanted holes:



(The red duct tape on the bottom of the block is for color-coding -- the red legs go with the red base, and so forth.)

Here is a side view of the block:



We used it in soft soil, rocky soil, and on pavement, and it worked perfectly. Since the tripod is higher than the wooden blocks but does not wobble at all, the stabilizer jack is not overextended and seems to provide much better support and stability.
  • nice job. I was lazy and just carry some aluminum jack stands. don't use the threaded part, just drop the stabilizers down on the stand that looks like an oil derrick.
    bumpy
  • Newman, I did not understand your comment -- could you clarify? And Bumpy, I tried those "oil derrick" things (I had a couple sitting in the garage), but the base was a little too narrow, and it rocked a bit. The tripod thing distributes the load over a wider area, and the angle of the legs means that the "force vectors" from the jacks run straight down the legs, instead of coming across the top of a narrow "derrick." (As you can see, I did poorly in high school physics -- not sure if this is really an example of vectors, but how often does one get to use that word in a sentence??)
  • profdant139 wrote:
    Newman, I did not understand your comment -- could you clarify? And Bumpy, I tried those "oil derrick" things (I had a couple sitting in the garage), but the base was a little too narrow, and it rocked a bit. The tripod thing distributes the load over a wider area, and the angle of the legs means that the "force vectors" from the jacks run straight down the legs, instead of coming across the top of a narrow "derrick." (As you can see, I did poorly in high school physics -- not sure if this is really an example of vectors, but how often does one get to use that word in a sentence??)


    my RV probably has less frantic movement in it than yours, vectoraly speaking. :)
    bumpy
  • Bumpy, that is a very insightful comment -- it never occurred to me that different people might generate different internal force vectors inside an RV, either in terms of magnitude or direction. I would guess that younger people would create greater vehicular instability, since they move around more rapidly than we do. I just qualified for my lifetime national park pass, so I would guess that I am on the low end of the vector spectrum. Nevertheless, DW prefers a rock-solid jack, so that is why we are using these tripods.
  • newman fulltimer wrote:
    u needsupport at the bottom of thema cable toeach leg


    I, too, think you need a base plate. Pressure in that design is likely to spread those legs and weaken the joint where legs join the top plate. This will be exacerbated by loose ground material.
  • Now I see what you are saying, Kiwi and Newman! Yes, that is a good idea, but it just adds more complication to the design -- the goal was to have something sturdy and easy to assemble and disassemble and store. To make up for a base plate, I have those very deep holes in the top of the tripod, so that the legs can't spread out -- they are firmly in place.

    Precisely because there was no base plate, I was worried about what would happen on loose ground -- on our most recent trip (the maiden voyage for the tripods), one of the tripods was on rocky soil, but the other one was on very loose dirt. I cranked the jacks down quite firmly -- the legs barely budged. They did not penetrate the soil much, because the legs are so wide.

    This design, by the way, is based on an old style three legged milking stool, a very sturdy object that can support a very sturdy milkmaid! Usually, of course, the legs are permanently attached with a wedged tenon coming through the top -- I have made several pieces of furniture using this joint, and it is rock-solid. But in this instance, I wanted the legs to pull out of the hole for storage.