Backrest details for do-it-myself-ers
(Page updated February 23, 2009 )

Parts bill of materials:

(1) Support bar: 3/4" tubing, 33 inches overall length. Ends flattened for about 2-1/4"
(2) "Clamps" 1/16" thick steel, 3" x 4 1/2" bent into a 1" diam. wide x 1-3/4" deep "U"
(4) "Receivers" 3/32" thick by 3" diameter circle, cut into 4 equal "ears" welded to top of "U" above.
(2) 3/16" thick steel plate x 1-3/8" radius
"ears" welded to flattened ends of support bar.

 

Overall view: note that the CB base clamp is used for a fiberglass mast for my US flag "conspicuity" and patriotism device.

The backrest pad is about 9" wide by 5" high and padded with about 3" of fairly dense foam. There are 4 studs mounted there for the pipe clamps seen at left. Depending on the clamps, those are about 1-3/4" apart, horizontally about 5" on centers.

You will see some chipped paint and rust in these photos -- it doesn't show when the rest is installed, but as soon as it gets warm enough to paint, I'll probably touch up the paint!




 

Flattened ends of support bar are about 3", with welded "ears" that go into the "receiver" which is welded to the top of the "clamp." That flat section is followed by a 5" radius 90 degree bend, then an 11 inch straight section, the second 90 degree 5" radius bend and 3" flattened straight end.

Measurements are all approximate; within +or- 1/8 inch.

 

 

These "ears" are 3/16" steel to match the thickness of the flattened ends of the support bar. The nice radius should match the radius of the "receiver" ears welded to the "clamp."

Do not drill holes until the parts are all completed and the clamps with their receivers are fixed to the handholds on the Helix. Then position the backrest support as close to the desired position as you can and drill two holes in each side of the assembly, to clear the pins you have selected.

The pins with this rest are 1.4" diam. x 1" long using hairpin clip retainers.

"Clamp" (toward left) and "Receiver" (to right.) Both "Receiver" ears could be cut from a single circular piece.

Like the "receiver" holes, the clamping holes at far left can be located and drilled after positioning. These seen here are close to minimum distance and require the clamping bolts to be "finger-threaded" past the Helix handholds.

I found that (4) sets of 3/16" x 1-1/4" hex-head machine bolts with acorn nuts and flat washers fit OK and provide a good appearance when the acorn nuts are on the outer faces.

 

Another view of the port-side clamp-&-receiver for clarity.

As noted elsewhere, I do not know who made these backrests but the quality of welding is excellent, and they obviously had jigs set up for their cuts and layout.

Note that the "receiver" part is NOT aligned parallel with the centerline of the clamp U-section. It has to compensate for the angle of the Helix hand grip at the point of installation.

Installing these clamps on my Helix's "rubberized" hand grips demands a considerable amount of force! I use of a rubber mallet for "fine adjustment." That is at least partially due to the rubber (innertube scrap) liner I have in each clamp to protect the hand grips.

Questions?? E-mail me: byewaybill (at) gmail (dot) com [if you can't figure out that address, click here]
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