A Jig for holding large radios
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I've just about reached the end of a long exercise
putting together an R1475 receiver that arrived here completely
dismantled.
The final task is to realign the four wavebands and
to redo the calibration line on the perspex dial. There are three
sides needing to be accessed as the RF trimmers and coil cores
are on the top and rear whilst the dial is obviously on the front.
Up to now I've had the receiver on its end on the bench to carry
out RF adjustments but now, adding in the dial recalibration
really needs the receiver to be worked on in its normal horizontal
position. In the past, when this sort of thing was necessary,
usually because it wasn't safe to balance a receiver upside down,
I've made a wooden framework but this isn't so easy with the
R1475 which is particularly heavy for its size, so I decided
to make a jig which will be useful for many receivers not just
the R1475. |
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One thing that gave me the idea was that I'm
scrapping an A0 HP printer which uses lots of heavy metalwork
and the fact I recently purchased an angle grinder for dismantling
an old trailer. Too much effort using a hacksaw!
I looked on You-Tube and sure enough I'm not the first
to make such a jig. Mine though will be entirely functional and
not very pretty. In amateur tradition I'll use whatever materials
(ie. junk box) or workshop facilities are to hand.
It'll make a good New Year resolution for 2024 as
I've needed something like this for donkeys years. |
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Above a view of one end of the R1475. In order to
use my planned jig I may need to drill a hole or two in the ends
of the chassis, but not necessarily as I'm already contemplating
a modification to the design of the jig whose construction is
underway. |
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Here's the pair of rotatable end plates (screwed
together to minimise and align drilling), My pillar drill hasn't
got the clearance for the centre holes which will be drilled
later when all will be drilled out for M6 bolts. The plates were
made from heavy steel sheet and are a little under 12 inches
square. |
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Right are the two legs and feet. The latter are the
HP printer feet cut down (now 14 inches long) so they'll fit
on my work bench. Across the rear of the feet you can see a length
of steel rod salvaged from the printer which will be cut to around
24 inches and threaded at M8 to fit between the feet to aid stability.
The legs will be drilled to accommodate M6 bolts which
pass through the centre of the end plates, as well as holes for
pegs to anchor the end plates at one of eight positions. The
height of the legs need to allow the end plates to be held at
a 45 degree angle with one inch clearance. The hole for the M6
bolt for the R1475 is therefore 9.5 inches above the feet. The
legs extend to 13.75 inches above the feet allowing for extra
holes to be added to give additional clearance for a future larger
chassis if required. |
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I'll be adding a short length of perforated
angle (a lightweight dexion equivalent) to each end plate via
pairs of holes in the diagonals. This will help support the R1475
chassis and maybe avoid the need to drill the receiver. The dexion
will also help to hold the receiver in position before fixing
securely.
I temporarily assembled the parts and noticed something
I'd overlooked. In the position on the right you can see I'm
asking for trouble. I suppose it's a"health & safety"
consideration, otherwise "common sense". I need to
round off those corners. I could also add a bar across the top
so fitting the receiver will be a lot easier. This need only
be a temporary thing as once the receiver is secured in position
the bar can be removed. To improve stability and to add turning
friction I'm going to use a wide diameter washer or packing at
the balance points. |
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This is the revised design which will not only
save a nasty accidental gash but also allows the receiver to
be lowered by over an inch or so. Cutting the 2mm steel sheet
wasn't easy, but by the eighth corner I was getting quite good
at manoevering the angle grinder.
The M8 threaded rod was also not easy and maybe not
such a good idea to make it long enough to accommodate an extra
long chassis.
I found a pair of surplus plastic IKEA parts to space
the end plates from the legs so the chassis can be moved around
without fouling the various bolts and to apply some friction.
Below, a trial fit of the R1475 in the jig.
I just need to fit a spacing rod across the top to
avoid the sides splaying outwards.
I'm using the top centre holes to keep the set in
position. The R1475 weighs about 40 pounds. |
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The finished jig showing various views. I added
a couple of spacing bars secured by M5 nuts to prevent the side
panels from splaying outwards and fastened the chassis in place
by drilling and tapping holes in the side plates through to the
chassis rails.
By tightening the nut on one side the friction can
be altered so the chassis can be rotated without it slipping
back.
I can now operate the receiver and complete the alignment
without having to stand it on end. In particular I can now add
a new tuning line across the perspex dial.
By altering the lower threaded rod the jig can be
extended to accommodate a smaller or larger chassis. |
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