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Reinforced Lapides Teegul Mount
Every so often on the Astromart Forums someone will ask, just how much telescope can I mount on a Takahashi Teegul? The Teegul, as modified by Richard Lapides, is a superb light weight alt-az mount. Very smooth and precise slow motion controls set the Teegul apart from other tripod based alt-az mounting solutions. Once you use the slow motion controls it is tough to do without them. The slow motion controls are operative even when both panning axes are locked, so it is very easy to change accessories on a Teegul mounted scope without having to re-acquire your object. High powers with smooth slow motion are an alt-az dream.
By Jim Brown - 5/11/2005
I own a Teegul which I purchased from Anacortes for use with an 80 mm refractor. The Teegul really performed well with this load. Could it handle more weight? Certainly; in my opinion. But could my Teegul support a substantially bigger telescope, a TEC APO 140 for instance? No sir, not a chance. Not effectively anyway…it sure would be nice set-up for quick trips to the mountains though.
The altitude bearing assembly of the Lapides Modified Teegul is connected to the azimuth bearing assembly by the aluminum block pointed out in Figure 1.
This connecting block is not solid metal, but is pierced by the shaft of the altitude bearing slow motion mechanism. This connection is a point of vulnerability that limits the amount of weight the mount can effectively carry. A similar block, complete with tapped mounting holes extends from the azimuth bearing assembly. The unused block on the azimuth assembly presents an opportunity for reinforcement.
My reinforced design includes a supplemental reinforcing member spanning the two bearing blocks creating a very sturdy rectangular support structure. The new reinforcing member is bolted to the altitude bearing with a new counterweight shaft and attached to the previously unused mounting holes tapped into the azimuth assembly. In addition, I added a reinforced tripod connection. The basic elements of the reinforced design are shown in Figures 2 and 3
The reinforcements do not affect the bearing motion in any way. The seams where rotation occurs are pointed out in Figure 4.
Construction of the Baltic birch plywood parts is pretty straightforward if you have access to a drill press and a router table. I made the tripod connection specifically to fit a Losmandy G-11 tripod which was freed up when I mounted my G-11 on a permanent pier, (which is why I need a second portable mount incidentally.) The Teegul is bolted into a deep socket hole-sawed into the tripod connection.
The Teegul bearing assemblies are hollow. The Lapides modification uses the cavity within the azimuth bearing to receive a custom cylindrical plug which anchors the altitude assembly. A similar arrangement can be added to mount the new counterweight shaft through the altitude bearing and through the new reinforcing member. The brass cylindrical nut, 1” finely threaded counterweight shaft and 43mm washers pointed out in Figure 2 together fit snuggly into the hollow altitude shaft. These parts are available online from McMaster Carr. The remaining non-wooden parts are available at any hardware store. The counterweights are commonly available dumbbell weights.
Figures 5 and 6 show the reinforced mount in action. It works quite well. The damping time is about one second after a reasonable bump to the telescope. The view is steady during focusing, of course the exquisite Feather Touch focuser has a lot to do with that! The slow motion controls are as smooth and precise as before I added the reinforcement. The unlocked axes pan as smoothly as ever.
In summary, the reinforced Teegul mount behaves and operates as one would expect a Takahashi Teegul to perform. It sure is capable of handling a lot more weight though! I have more pictures if any Teegul owning do-it-yourself types are interested. I don't have any CAD drawings though! Clear skys, Jim Brown