{"id":417,"date":"2019-06-09T11:30:14","date_gmt":"2019-06-09T11:30:14","guid":{"rendered":"http:\/\/3dprinterpartsandaccessories.com\/dad\/?page_id=417"},"modified":"2019-06-09T11:39:25","modified_gmt":"2019-06-09T11:39:25","slug":"truss-spar","status":"publish","type":"page","link":"http:\/\/www.n3ttt.com\/dad\/truss-spar\/","title":{"rendered":"Truss spar"},"content":{"rendered":"\n
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Spar made from 6061-T6 aluminum angle stock supports truss cables on Cushcraft XM240 yagi. (Photos by AA1K)<\/figcaption><\/figure>\n\n\n\n

Many beams with long booms use a truss cable for added support. While some manufacturers will include a spar mounted on the boom for this, many save a few dollars by having the spar attach to the mast.<\/p>\n\n\n\n

The disadvantage to using the mast is that it requires more time on the tower for the climber to attach and adjust the turnbuckles \u2014 usually requiring a few steps up and down to get at eye level with the beam to check the adjustment.<\/p>\n\n\n\n

Here is how Adam, N3TTT, and AA1K recently made up a spar for the truss on a Cushcraft XM240, a 2-element 40-meter yagi.<\/p>\n\n\n\n

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Truss spar is mounted on reflector side of boom-to-mast bracket on XM240.<\/figcaption><\/figure>\n\n\n\n

With this modification, the truss is installed and the turnbuckles adjusted while the beam is on the ground. <\/p>\n\n\n\n

This also allows the beam to be placed higher on the mast , instead of 3 feet or more down from the top when the stock Cushcraft truss bracket is used. <\/p>\n\n\n\n

A side benefit, if the beam is being trammed to the top as this one will be, a rope tag line may be attached to the top of the spar to tilt the boom to lift the elements above the guy wires.<\/p>\n\n\n\n

The angle material is 6061-T6 aluminum obtained from a Delaware salvage yard, 3\/16\u2033 thick. We bolted two pieces together for extra strength. With 1\/4\u2033 thick a single piece would have worked. We used two 1\/4\u2033 stainless steel U-bolts with saddle clamps to secure the spar to the boom. <\/p>\n\n\n\n

We used the original Cushcraft truss bracket and some additional hardware to add weight at the reflector end of the boom to physically balance the beam. <\/p>\n\n\n\n

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New truss spar for XM240 was made by bolting two pieces of aluminum angle stock together.<\/figcaption><\/figure>\n<\/body>","protected":false},"excerpt":{"rendered":"

Many beams with long booms use a truss cable for added support. While some manufacturers will include a spar mounted on the boom for this, many save a few dollars by having the spar attach to the mast. The disadvantage to using the mast is that it requires more time on the tower for the […]<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-417","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/pages\/417","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/comments?post=417"}],"version-history":[{"count":1,"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/pages\/417\/revisions"}],"predecessor-version":[{"id":424,"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/pages\/417\/revisions\/424"}],"wp:attachment":[{"href":"http:\/\/www.n3ttt.com\/dad\/wp-json\/wp\/v2\/media?parent=417"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}