Bob's they ain't, still pleased with these knobs

[michael.h.f.wilkinson]

After having used my home-brew alt-az mount intensively for solar sessions during lunch, I have found one slightly annoying weak point: The lock-nuts used to adjust tension on the friction bearings can only be adjusted with a spanner of some kind. As the wood expands and contracts with changes in humidity and temperature, the tension on the friction bearings changes, and I do not like to carry spanners in my telescope bag. I decided to make a kind of "Mike's Knobs" along the lines of the knurled knob I had fashioned to attach the mounts (p-mount and the alt-az single-armed fork we are talking about) to the tripod, as seen below.

This knob consists of two pieces of plywood each cut with a hole-cutter from a left-over bit of wood. I used a similar procedure to make the new knob (on the left). I started out by marking out a hexagon on 18mm birch plywood, with the same diameter as the hole-cutter (68mm in this case), and marking the centre. I then drilled 6 18mm holes in the wood, centred on the corners of the hexagon.

By cutting the hole centred on the hexagon, you get the rough knurled shape, as shown above.

Filing and sanding gets the final shape, and a smaller disk cut from 9mm birch plywood was cut with a smaller hole-cutter. These were then attached to each other temporarily with an M10 bolt and nut.

This allowed me to mark out the shape of an M10 nut on each of the components, and cut the shape out to a sufficient depth in both parts. I needed to recess the lock nut into the smaller part sufficiently deep to have the plastic locking ring reach the thread of the M10 bolts used as axles. The older (larger) one shown above with the M10 bolt for attachment of mount to tripod only needed one hexagon cut out, to hold the head of the bolt.

Drilling countersunk holes in the smaller part, attaching them together with three screws, and applying oil to protect the wood is all that remained

This shows the knobs in place (one not oiled yet) when I had a brief solar session earlier today.

The final touch was repeatedly oiling the last knob (and writing this report )

I am very pleased with the result. I can adjust the tension very easily without resorting to any tools

[faulksy]

very, nice work Michael, very talented

[swamp thing]

Nicely done Michael

[michael.h.f.wilkinson]

Cheers, guys. It was a bit of fun work for a rainy Sunday

[JAS]

Nice job Michael.

I have used the same technique to make knobs from aluminium.

Jason.

[martindale]

They look good, nice to see a bit of wood here and there.

Paul.

[rowan46]

thats an awful lot like a wooden version of my techno sky elle

[crashtestdummy]

beautiful craftmanship.i love seeing the labours of someone who would rather make their own solution rather than pay for it.wish i had the abilities

[michael.h.f.wilkinson]

Thanks again, guys. The nice thing about this is that you can make this design with fairly simple tools. An electric drill on a decent but inexpensive stand (the stand cost me less than 20 euros way back when I bought it) was the only power tool required. An electric screwdriver helps, but is luxury. I cut the hexagonal holes for the nuts with my Swiss army knife. I don't think it would have been able to handle aluminium .

I have found a few niggles in the design, and I do wonder if birch plywood isn't too springy for this work. I might build a redesigned one for home and travel, and use this one purely for solar sessions at work.