2" shaft mouting pt5. Everyman's, large equatorial mounting.

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What I was ideally aiming for when I started this 2" shaft, mounting project was something which could be copied by those without a shed full of tools, welding facilities or any particular manual skills. A sort of "Ikea-style," heavy duty, equatorial mounting which could be scaled up and down to taste and need. All it should require is the ability to assemble the sum of the parts into something useful and practical. A sort of "large equatorial mounting for the common man" if that does not sound too pompous.  

It might become the basis for a universal mounting which could easily handle large and long refractors. I see my project as a generalized response to the almost complete absence of suitable and affordable equatorial mountings. This lack is blocking easy access to "classical" refractors. Or even long focus [so called- planetary] Newtonians. 

Without spending a great deal of money [many thousands of euros, pounds or dollars] there really wasn't much available beyond a Dobsonian altazimuth mounting for this category of instruments. This absence of suitable mountings is forcing very short focus telescopes onto manufacturers product lists. Which directly hampers their optical quality in an achromat and makes an APO the only [but very expensive] get-out clause. Larger APOs themselves are very heavy too. Which makes the choice of mountings even more stratospheric in cost for the complete instrument. This pushes them firmly into a niche product instead of enjoying all the benefits of [cheaper] mass production.

I have been pondering ways to properly stiffen the flange and stud assemblies. The entire length between the flanges really ought to be completely filled with an incompressible material. Leaving a central space for the shafts to turn freely of course. The large studs [threaded rods] would compress the packing material between the sturdy flanges. Producing a virtually solid housing at very low cost in materials with only very limited skill or tooling required. 

No heavy supporting plates are required as is vitally necessary with a successful pillar block mounting. The finished mounting will be no lightweight but should [ideally] be able to tolerate being left outside under a simple cover without rapidly losing its cosmetic appearance.

Despite the squareness of the flanges the housings need not be square externally. It would require a 200mm [8"] round pipe to enclose my 143mm square, bearing flanges over their corners. Though a smaller pipe could protect the packing material while leaving the flanges exposed. Perhaps not the most attractive option aesthetically and providing much less protection for the packaging and bearings. Though 8" disks behind each flange might look more the part this could require a lathe for a really neat job. Depending on the materials involved. I am trying [hard] to avoid the use of machine tools in my design despite owning a lathe and many other tools. 

My "prime directive" [if you like] is to build something from materials readily available anywhere in the civilized world. By this means the builder can bring their own skills, materials and inspiration to the table. Hopefully leading to a steady improvement over time with each new iteration. As has occurred repeatedly to the [originally] very crude Dobsonian "sidewalk" telescope. Scrounged or free materials being the only requisite at first but which eventually led to the exquisitely made, modern, lightweight, truss Dobsonian. Slavish copying rarely occurred with the Dobsonian because the basic design was so "right." The "hive mind" went to work in cooperation and competition to improve the Dobsonian from the basic cardboard tube and dumpster scrounged, rocker box DNA.

Those who demanded a higher standard and were willing to pay for it has resulted in a whole new industry of amateur telescope makers and commercial manufacturers. The same has never occurred with equatorial mountings. Superb mountings are available commercially but at a price well beyond many pockets. The best mountings are immensely strong, reasonably lightweight and have all the bells and whistles of Goto and accurate tracking to match the modern imager's demands Unfortunately these multiple demands have further escalated the prices of most equatorial mountings. 

The amateur cannot easily copy the opposed bearing, hollow shaft precision of an AP1200. Not without castings and a decent lathe and the finely honed skills to use it. So we must use mass and stiffness to our own advantage. The result will not be lightweight but it will stand up to the requirements of stability in a breeze. While simultaneously carrying an 8' long telescope with the really heavy lumps stuck on each end. The huge moment arm must be controlled and damped without introducing any friction. Otherwise the thing can't be driven or pointed with a high degree of accuracy. 

Reading back through the old ATM books, in 3 volumes, "lightweight" is hardly ever mentioned. Solid brass tubes for refractors are certainly mentioned as highly desirable. That was in an era when making the mounting was also the norm. Heavy steel telescope tubes, water pipe fittings, massive wooden beams and concrete castings were what was used back then. That was before light pollution forced many city based amateurs to carry their instrument off to darker sites. Thus began the demand for light weight in everything except up-market focusers. Where [very strangely] a five pound, oversized lump of CNC'd metal is considered perfectly acceptable and even greatly admired.

I quite like the idea of 200mm [8"] PVC pipe to offer long term protection for [say] solid birch plywood packing. Simple PVC caps could conceal the flanges and bearings leaving only the stainless steel shafts exposed. PVC pipe and fittings are readily available almost everywhere. 

Round 8" PVC pipe would certainly match the sheer scale of the mounting and refractor. In fact it would perfectly match the diameter of the steel main tube. Above all, the finished project should look sleek and "professional" without requiring hundred of hours of "titivating." Hopefully the finished result would achieve a neat, weatherproof finish of which one can be reasonably proud without needing a professional spray job. Just because something is affordable and requires low skill levels does not mean it should be tatty or look like a pile of junk. Or worse, like a modern art sculpture thrown together by a welding 'amateur' reinventing the wheel. 

Square PVC pipe is much harder to find despite its apparent desirability to appear in keeping with modern trends in high-end equatorial mountings. Non-availability makes it a non-starter. Though roof flashing aluminum could be bent around a square plywood form if that is the desired format of the builder.

The would-be builder should note the wide availability of dirt cheap, high quality flange bearings in many different bore sizes.[Metric and Imperial] Thick wall pipe could be adapted to the axis shafts if that is what is available to you. Though thin wall tube might be too risky. Better to fill thin but smart, stainless steel tube with cheap "iron" water pipe to increase the stiffness if in any doubt at all. 

Finding suitable shafts might be the best option before choosing your flange bearings. I was incredibly lucky and found a local engineering firm willing to sell me stainless steel shaft at cost. Nor is stainless steel absolutely necessary except for its superb longevity under the usual damp conditions where amateur astronomy is concerned. I fought with rusty steel shafts for years before finding stainless steel shafting in my own neighborhood. It is readily available on eBay too. Albeit at a very high asking price plus freight.

Rusty, ordinary steel shafts not only stick fast in your precious bearings but will make counterweights and locking bushes very difficult indeed to remove or adjust.  Gather your courage and ask your local engineering companies and metal stockists to see is they will help with stainless steel shafting [or thick pipe] for your telescope mounting project. You have nothing to lose by turning up at their door and asking politely.  Check your local small ads websites for oddments of SS shaft or even the bearings. Though these tend to be far more expensive than buying new! Businesses do go bust and could provide your shaft materials if you ask at just the right time. 

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