Wilmslow Astro
Astronomy from a Cheshire suburb
LX200 Pier and Mounting Plates
Please excuse the mixture of units, I've used both metric and imperial. This is in part forced by having to work with equipment made in the USA which still lives in the middle of the 20th century when it comes to international standards :)
[Click on the images below for a larger versions]
| I designed the pier to use my Milburn wedge. You can produce a design that does not require a wedge, but as I had one anyway for use on the tripod I may as well use it. | |
 | The pier itself is a steel tube 155mm in diameter, it has a wall thickness of 10mm. The tube was originally the outer case of a hydraulic ram. I've had a couple of bolts welded to the tube to provide some keying into the concrete when it is sunk in the ground. |
 | The wedge will be mounted onto an aluminium top plate, which in turn will be bolted to a steel bottom plate to provide levelling adjustments. The steel bottom plate is welded to the top of the pier. |
 | Bottom Plate The bottom plate is the simplest, it is a sheet of 15mm thick steel plate 12" x 10". It has four 13mm holes bored 1" in at each corner. This plate was then welded directly to the pier tube. |
 | Top Plate The top plate is a 25mm thick sheet of aluminium alloy 12" x 10". I've drilled and tapped M12 (use 3/4" for imperial) threads 1" in from each corner for the levelling adjusters. The three bolts to hold the wedge would normally be 5/16" but I've used M8 cap head bolts as imperial fasteners are hard to source. I've stuck with a 1/2" UNC machine screw for the central wedge bolt as the wedge comes with a nice knob to fit this thread - but what a job finding that size bolt in stainless steel. Finally a 5/16" slot was milled in the plate to accept the wedge latitude adjustment pin. |
 | Side view This is the complete assembly from the side. I used some M12 studding cut to length (90mm or 3.5") for the levelling adjusters, these are screwed into the top plate (with Loctite) and locked up with half height nuts. The levellers must not protrude above the top surface of the top plate or they will interfere with the wedge. The 1/2" UNC screw is threaded up through the bottom of the top plate (with Loctite) so it stays in place when the wedge is removed. |