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I think I need a Hargreaves strut to stabilise the secondary cell to the
end of the Dec shaft. This will help to avoid spar flexure in windy conditions. It is only rarely quite still
where I live. I just need to find suitable clamps for the long length
of 10mm stainless steel tube I found amongst my stock.
The
answer to the Dec shaft clamp problem was hiding in my cycling junk. A
seat tube, quick-release clamp for holding the saddle pin tight in a
modern bike frame. BTW: These clamps have a small flange on one edge of
the machined bore. This is partially cosmetic but also to stop the clamp
sliding down the seat tube when loosened. This can confuse if the clamp
is applied to the shaft the wrong way around. I didn't notice the
flange while I was fiddling in the dark and had completely forgotten its
presence. I shall file the flange away or spin it in the lathe to allow
the Declination shaft clamp to be easily fitted in the dark.
A small tube clamp will be fitted under the large clamp's knurled
adjustment nut to hold the lower end of the Hargreaves strut firmly. The
large Q/R clamp will allow the strut to be fitted and clamped to the
end of the Declination shaft in an instant. The other end of the strut
will fit in a similar tube clamp and be fixed to the top end of the OTA.
A wing nut will speed the clamping of the top end of the strut into the
tube clamp. Adding the Hargreaves strut permanently to the OTA would
increase the weight to be carried out to the mounting. More images to
follow when I find suitably small tube clamps for the strut itself.
Bicycle "brake clamps" are very suitable if I can find the correct size
amongst my endless boxes of old cycle junk. An easier alternative is to use a rear, bike light clamp on the Declination shaft. A couple of packing washers help to trap the small clamp ears and tighten it perfectly just as the large clamp screw is fully tightened. I decided to add the clamp above the counterweights to avoid using a very long strut. A 45/45/90 triangle is all that is desired to triangulate the OTA to the Declination axis.
Click on any image for an enlargement.
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