KM5VI

Fabrication of Hoist Supports

This page shows some custom supports I designed & fabricated to raise two of the towers that I did not have raising fixtures for.

The elevating is accomplished with a 2-ton chain hoist. The hoist is supported by pipe supports that are embedded into the tower foundations.

The foundations were elongated to accommodate the pipe supports and additional steel reinforcing was added to the rebar cages to handle the

additional loads. The pipes were sized based on a stress analysis. The initial stress analysis was done on a spreadsheet and the

predictions were verified using computerized finite element stress analysis. Whereas this installation may not have been economical

had I bought all new materials, I already had the hoist and almost all of the materials on hand - so I just did a little re-purposing...

This is an Overview of FE Stress Analysis Model in Simplified Form

The Vertical Column on the Left is the Pipe Support.

The Horizontal Member is the Tower & Mast with Superimposed Loads for the Antennas & Rotor.

The Diagonal Member is the Lifting Chain.

Maximum Loads are Developed Just as the Tower is Lifted off the Ground from Horizontal.

This is Graphical Output of the Lifting Pipe Under Load.

Primary Stress Values Appear as Colored Bands Along the Outside Edges of the Pipe.

Note the Dark Blue Band About 1/3 Up on the Right.

This is Where the Maximum Bending Stress Predicted at ~28,500 psi in Compression (Negative Value)

The Yield Strength (Threshold of Permanent Deformation) for the Steel is ~36,000 psi.

The Ultimate Strength (Breaking Point) is ~60,000 psi.

The Theoretically Factor of Safety for Permanently Bending the Pipe is ~1.25:1, and

2:1 Factor of Safety for Ultimate Failure.

It is Prudent to Not Permit Anyone in the Fall Zone During Lifting.

One Way to Beat the Scorching Texas Summer Heat... Work After Dark!

This is the Fitup for the Hoist Bracket on 6" Sch 40 for the W51 Tower.

The Thru-bolt is 1.25" ASTM A325.

The Washers were Placed as Spacers During the Fitup and Welding.

The Top Plate Serves Several Functions - Top Support for the Bracket, Attachment Point for Guys,

and a Cap to Keep Rain & Critters Out of the Pipe.

This is the Hoist Bracket on 8" Sch 40 for the LM470 Tower.

It Shows the Supports Above & Below the Bracket.

The Bracket Edges were Ground Tapered to Accept the Fillet Welds

Welds were Made at ~180A.

Test Welds were Prequalified on Scrap with a Simple Bend Test in a Press to Verify

Failure of the Base Metal Prior to Failure of the Weld Metal..

Welded Out & Ready to Go

This Shows the Arrangement of the Additional Rebar for the Pipe Hoist Support.

Thwer are (4) Additional Vertical Bars and (9) Additional Loops

at the Top and Bottom of the Assenbly Where the Foundation Stress Concentrates

under Hoisting Load..

.

Another View of the Cage After Placement.

Lifting the Pipe into Place...

Putting it in was Easy.

Getting it Aligned into Position & Plumb... That's Another Story!

This View Shows the General Arrangement with the Pipe & Tower Base in Place

Hoist Support Installed & Temp Guys (good use for old lifting cables).

6" Hoist Support Being Used to Raise the W51 Tower.