Telescope Mount Adapter

The University of Iowa donated the Rigel robotic telescope to the Cedar Amateur Astronomers. Plans are to install this telescope in one of the domes at the observatory. To mount the scope an adapter is needed to connect the scope to the concrete pier in the dome and to raise it to the proper height.

Dr. Scott Bounds designed an adaptor and worked with the University of Iowa Physics Department Machine shop to get it fabricated. The adaptor is made of donated aluminum plate. The bottom plate is 1.75″ thick and the rest of the parts are 5/8″ plate.

Dr. Bounds has been busy with his work at the University and Fred Young and myself wondered if we could help out getting the adapter completed. When we inquired about it we were told that it was complete except for the welding. So I offered to help with the welding. My son Paul does aluminum welding and our recently acquired welded is capable of aluminum welding. The machine shop foreman delivered the adapter parts to my shop. It was then that I learned that they had tried to weld the adapter but were unable to get good welds. This made me a bit nervous. We were thinking that they just did not have the time to do the welding.  They were trying to use a TIG welder. TIG welding is excellent for precision welding but is not really suited for the heavy duty welding needed for this thick material. We have a MIG (wire welder) which is more suited for this type of welding. Our welder is set up for .035″ wire.

Above is the mount as I received it.

To clean up the poor welds I used an angle grinder to remove the welds and disassemble the pieces. I ground off all the old weld so we could start over with clean parts. Essential for good aluminum welds is clean metal. After the parts were ground clean they were wiped down with acetone to remove any potential grease or oil.

We did not know what alloy the parts were made of so I just picked one of the two common welding wire types (4043) and turned the welder up to a fairly high power level.

Due to the thickness of the part we thought the preheating would be necessary. So I arranged to preheat the parts with a fish fry burner.

After making a few welds we noticed that the welds all had a crack running the length of the weld. Clearly something was wrong. The dull look of the welds also indicates gas porosity in the weld.  We finally decided that we were welding too hot. The welds were all ground out to get ready for the next attempt. Along with turning down the power we switched to the other common welding wire (5356) and skipped the preheat.

The changed did the trick and we had a nice shiny weld with no cracks.

Above is the adapter with the bottom welding complete and the top plate clamped on to tack weld in place before flipping the adapter over to weld on the top plate. The welding used 4 pounds of welding wire and about 100 cubic feet of argon.

Above is Paul welding on the adapter.

After the welding was complete I sandblasted the adapter to remove the weld smut and splatter. After a coat of paint it will be ready to return to the University shop for final machining.

References:

Cedar Amateur Astronomers https://www.cedar-astronomers.org/

A short video of Paul welding on the mount. https://youtu.be/0kKoOcM15zw

 

This entry was posted in Amateur Science, Astronomy, Machine Shop, Metal Working, welding and tagged , , , . Bookmark the permalink.

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