DIY Goto Gem with 50mm SS shafts.

[Rusted]

I'm not sure I've posted any close-up images of my massive, home made mounting:

Mostly built from scrap aluminum plate in 10 & 20mm.

50mm polished SS shafts in self aligning flange bearings.

Multiple studs [all threads] compress the housings in all planes for massive rigidity.

AWR-ASCOM Goto via 11" & 8" wormwheels and large stepper motors with belt drives.

On screen click and Goto via serial cable or AWR IH2 handset.

Mounted on a 4"x4" x nearly 13' tall, timber, pyramidal pier resting on height-adjustable, buried concrete anchors.

The images show my old 6" f/8 which has recently been converted to Solar H-alpha.

Still waiting for warmer weather for gluing the 3m, 10' trapezium dome together.

[michael8554]

Beautiful !

Will it go to the zenith through the fork - looks tight ?

Michael

[Rusted]

5 hours ago, michael8554 said:

Beautiful !

Will it go to the zenith through the fork - looks tight ?

Michael

Thanks, Michael.

The base fork is merely a sturdy support for the polar axis of a normal GEM. [German Equatorial. The whole lot pivots on the 16mm stud [with large, domed, brass nuts.] A turnbuckle inside the fork provides fine adjustment of polar altitude when the brass nuts are slacked off.

My Fullerscopes MkIV uses short pivot bolts simply because they cannot pass through the Polar Axis shaft. Eventually the threads wear and the altitude locking screws wear away in the thin and very soft, alloy castings. Its very own and rather serious Achilles heel. So I deliberately designed my own mounting to allow an offset, polar altitude pivot to safely miss the polar shaft. The nuts on the altitude pivot stud could be fastened really tightly. To press the sides of the fork immovably against the sides of the box-shaped, polar housing.

The whole mounting is designed to reinforce itself in all planes, through the alloy bearing boxes using multiple studs. [Threaded rods.] The whole lot can be easily dismantled down to its constituent plates and components in case I made a mistake in the design or construction. I used flanged, industrial, Tollok clamping bushes [Image 2] to join the ends of the heavy, stainless steel shafts to the cradle and to join the two axes. A 7" diameter plate bearing further reinforces the joint between the polar and declination housings. 

The first image shows the longitudinal, 16mm studs which hold the massive bearing flanges rigidly together against the ends of the 10mm thick, bearing housing boxes. Then multiple 8mm studs criss-cross the 10mm thick alloy bearing boxes to hold it all tightly together. Many more were used than shown here. All the studs were carefully placed to press tightly against each other to avoid any risk of lateral flexure. All the flat, low profile heads you see on the outside are nuts to tension these, galvanized cross studs. I ended up with a sort of steel-reinforced, alloy casting without needing any castings. Weight was unimportant but is probably up around 250bs from memory. The weight of the individual components was always a difficulty. Needing a chain hoist to lift them or take them apart!

I made no drawings. Simply designed it as I went along. The design developed entirely around the very limited availability of any scrap aluminium I could lay my hands on locally. It was all sawed up from long strips using a hand held, electric jigsaw or by hand with a hacksaw. Only later using a DeWalt, bench miter saw fitted with a special [metal cutting] blade. I wish I had started with the DeWalt. Effortless and speedy cutting with guaranteed square ends, but very noisy!