Home Designed Pier & Wedge
Steel Wedge & Pier Design
The first wedge I owned was a Mead 10” deluxe wedge with a compass and latitude adjuster. Many people moan about this wedge as opposed to the super wedge but on the whole I found that it could be accurately drift aligned. Although it is not the most stable of accessories it is adequate for short exposure astrophotography. There are a number of personal websites, which show how to modify the standard wedge, which I searched through where I also discovered sites that showed how to modify the Superwedge. This came as a bit of a shock as the superwedge is over £450 in the UK and still required modification!
Whilst debating on the purchase of a superwedge there was a thread on MAPUG that discussed the merits of other wedges namely the Mettler and the Milburn although these wedges seemed far superior to the Mead Superwedge they were still expensive and had long delivery times.
The Mettler wedge appeared to have resolved the azimuth backlash issue and the Milburn appeared to be a superb piece of engineering, which was backed up by a vast number of users. About this time BC & F in London launched their own 15mm steel wedge for pier mounting. This was another well-engineered piece of equipment but at £450 still a bit out of reach especially as I also had to build a pier.
So I sat down at my computer with a few pages of measurements and set about designing my own wedge and pier set-up. After a number of redesigns and much discussion on MAPUG, as well as with my good friend Darren Carlisle who was also designing his own wedge I settled on a steel pier with an adjustable top plate for levelling. The wedge is similar in size to the Milburn wedge and made from 15mm steel. The azimuth adjustment for my wedge has almost zero backlash. It is a hybrid of the mead adjustment on their standard wedge and the Mettler adjustment system. I believe that although the Superwedge and the Milburn system of adjustment are easier to use the Mettler and Mead standard wedge do not suffer the same level of backlash, and on a permanent installation once it is set-up regular adjustment will be minimal.
The pier is bolted into a 900mm cube of concrete and roughly levelled via the bolts the base is then backfilled with cement. The pier top has a plate that covers a hole. (Not shown on the drawings) this allows the pier to be filled with kiln-dried sand to give it mass. The pier was manufactured from 15mm steel plate and welded with 6mm fillets. The adjustable top plate is made from a solid 65mm thick disk of steel welded to a 15mm thick 300mm disk of steel, with a steel upstand for the azimuth adjustment. This is fixed to the pier via 3 18mm bolts that are used for levelling.
The wedge was made from 15mm steel plate welded with 6mm fillets. It is fixed to the pier adjusting plate by 4 bolts much the same as the standard mead attachment system. During manufacture a large aluminium wheel was found and attached to the latitude adjusting system this has made for far more accurate adjustment when setting up.
The azimuth adjustment is achieved buy two 10mm stainless steel bolts that pass through either side at the rear of the wedge and press against the steel upstand on the on the adjustable levelling plate, letting off one and adjusting the other moves the wedge in either direction.
Now that the pier and wedge are installed and drift aligned I have found its performance to be excellent. It has passed what I term the jump test, which involves a 15 stone man who jumps on the ground one yard from the pier whilst I look through the EP, the image settled in less than I second.
The design for the wedge shown here will work for latitudes between 35 to 60 degrees. The drawings will require some adjustment for latitudes outside of these.
Any one who wants to use the plans can happily do so the total installation cost around £515 although, the steelwork was completed by people I know, at cost. The plans shown on this site are in word format. Anyone who would like the plans in AutoCAD can have them if they e-mail me.
Tony Floyde March 2002