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Building a Module: Legs

Building sturdy legs is an interesting challenge with a 40 inch length and only 3 inches to work with for support under the module. Somewhere there has to be a compromise between sturdy, light weight and easy to set up. A small force at the bottom of a leg results in significant torque trying to rip it out of the soft pine base.

There are two basic choices—wooden legs or Electric Metal Tube (EMT) legs. Rodney Bohlmann, who was building his module about the same time, constructed a very nice set of wooden legs. After lots of research, I decided to try the 0.75 inch EMT legs, which seem to be the current preference in the club. The design used addresses two challenges: solid support in soft pine module corner blocks and a rigid support for the eye-bolt at the bottom of the leg.

Materials

Perhaps a list of materials used is the best way to start this description since a lot of search time was involved in finding the right components for this project. Where there is a unique source, it is also listed.

  1. 3/4” Electric Metal Tube (EMT) (Home Depot).
  2. Corner blocks cut from pine 2x4, 3 1/2” on a side.
  3. 1” washer to go in bottom of hole.
  4. 3/4” PVC 1120 drinking water pipe rated at 200 psi. Inside diameter is critical and was tested with a piece of the EMT that was to be used. (Lowes).
  5. 1” by 1/4” thumb screw.
  6. 2 inch “mending plate” drilled and tapped for 1/4”-20 threats per inch.
  7. 5/16” by 6” eye bolt with threads for at least 4 inches. Most are threaded for only 3 inches. (Lowes)
  8. 5/16-18 Tee-nut.
  9. 7/8 inch dowel rod.
  10. #4 by 3/8 inch metal screws
  11. #4 by 3/4 inch metal screws.

Top support

The pine blocks, used on most modules with EMT legs are, in this case, drilled out to 1 1/16” to accommodate a 3” long section of PVC pipe. Since a bit this size is not available, a 1-1/8” spade bit was ground down to size with a power tool and file. It was actually fairly easy to do. As shown in the drawing, the hole is not drilled all the way through the top block with ¼” of wood left to absorb the thrust of the leg.

The outside of the PVC pipe was roughed up with sandpaper so glue would hold it in place. A 1” washer was put in the bottom of the hole for the EMT leg to but against and the assembly glued and clamped. Once the glue has set, a 1/4” hole was drilled in the long face of the bottom block, through the PVC pipe, for a thumb screw. The thumb screw was held in place by the mending plate and two #6 by 3/4” screws. This assembly was attached to the module base with glue and screws.

For the bottom of the leg, 4” and 2” lengths of the 7/8” dowel rod were cut. A 5/16” hole was carefully centered and drilled in each dowel for the eyebolt, asshown. A drill press was very helpful in getting the holes straight. The dowel rod diameter was a little too big to fit in the EMT so some filing and sanding was needed to get a proper fit. Slots were cut in the bottom of the 4” dowel to match the Tee-nut so it would not split the wood.

The Tee-nut required a little grinding on the edges with a power tool. With all the pieces in the EMT ,as shown, two #4 by ¾ machine screws were inserted near the top of the 4”dowel—beyond the reach of the eye bolt when fully inserted. These screws must handle the upward thrust on the leg. Two smaller machine screws, #4 by 3/8, were used to hold the 2” dowel in place and to keep the Tee-nut tight.

The EMT was cut to a length so that the module roadbed was 40” above the floor when one thread was showing on the eye bolt. This allows the module to quickly set to the right height. For example, for a module with a ½” plywood top the legs would be 36 3/4 inches (40”- 0.125 for cork - 0.5 for plywood - 0.25 in pine block - 0.0625 for washer - 2.25 for remaining eye bolt length at one thread = 36.8125 so 36 3/4 is close enough). The eyebolt can be screwed in or out for the required plus/minus 1 inch.

Yes, the legs can be stored in the frame of both a POFF and corner module.