View Single Post
Old 02-03-2019, 07:34 PM
Registered User

Wavytone is offline
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 4,147
Hi Les,

It was a frankenmount. In that pic the scope scope with a square OTA is the original 6" f/18 Loveday folded newtonian, with a 6" f/8 for comparison, as it was published in S&T. Normally though it carried 8" f/7 and one of the 6" scopes onboard.

The mount started as a AstroOptical "Goliath" with 1.5" solid shafts running in bronze bushes, but:

- the original steel central pier and legs were pretty flimsy IMHO. I made the rigid tripod using Karri floorboards glued and screwed, it was vast improvement - only thing better may have been a solid concrete block.
- the 8" diameter worm wheel and clutch was smelted, cast and machined by a friend with a machine shop. The raw material was duralumin, from several engine blocks I found on a tip, and smashed into small pieces with a 16lb sledgehammer one afternoon (I had worked as a surveyors chainman for years, and boy could I swing a sledge. A well-aimed good whack would punch a neat 3" hole in an engine block). I had a backyard BBQ made from concrete blocks which we adapted as the furnace using a vacuum cleaner in reverse to provide a forced-draft, and made a crucible made from casting clay. Loaded with coking coal the crucible was white-hot and easily hot enough to melt aluminium alloys. The alloy was cast in sand moulds as described in one of the SciAm ATM books.

Very dangerous stuff to attempt in a backyard, though we cast enough alloy blanks to keep him happy for a long time. Duralumin was apparently nice stuff to cut on a lathe, yet hard and strong - and with a significantly lower melting point than aluminium.

- parts of the mount were reinforced with welded gussets as I identified where it flexed the most.

- while living in Canberra I had the mount on the lawn trolley to move it around, as the house had an extensive garden-cum-orchard.

Always regretted swapping the 8" and mount for a C8. The 8" was far better but too heavy to manage at a time when - as a uni student - I moved to Sydney to live in shared accommodation, whereas a C8 was manageable despite comparatively poorer optics.

Last edited by Wavytone; 02-03-2019 at 07:58 PM.
Reply With Quote