Lightbridge 12 new base project
Posted 12 November 2012 - 01:39 PM
I'm using 1" hardwood plywood throughout.
I added leveling feet to make leveling easier when using setting circles where a level base is critical for its accuracy. This sure beats getting down on my hands and knees to use shims to level the base.
The ground board is only 18" in diameter, plus a couple of inches for the ears for the leveling feet. This is much smaller than the stock ground board diameter of over 22". Actually, the new azimuth bearing contact diameter will be larger than stock.
The altitude bearings are 24" in diameter, roughly 1.7x the OTA diameter. Hopefully, I won't be needing counterweights when switching from light to heavy eye pieces. I also moved the scope's horizontal center point of gravity slightly higher up the OTA for better balance.
The base will be painted white to match the scope.
I'll be posting more photos as I near completion.
Thanks for looking.
Posted 14 November 2012 - 11:54 AM
Although I trimmed bits and pieces from the stock base to make it quite a bit smaller and lighter the new plywood base is by far much lighter and more compact.
A cutout will be made at the front of the base for the azimuth setting circle.
Posted 14 November 2012 - 01:17 PM
Posted 14 November 2012 - 01:39 PM
I think, in general, the problem with manufacturers using pressboard is that bases need to be kept overly large in order for them to be strong and long lasting. Anything compact and or skeletal can be made as rigid out of pressboard but might not last that long with prolonged use.
Posted 14 November 2012 - 02:30 PM
Not sure how well it is going to balance... I built a new base for my LB16 and can now use it without any counterweights (from naked BGO to 31T5 with Paracorr) but the center of radius of my trunnions seems to be several inches higher than yours. Then again, yours is a 12 and mine is 16. It does look great though...
EDIT: I went back an read how you said the center is a few inches up -- that should work. I think I moved mine up 2" or 2.5". (I weighed everything, calculated the moment arms to determine where the trunnions needed to be, and it all worked out great.)
Posted 14 November 2012 - 02:42 PM
Not sure how well it is going to balance... I built a new base for my LB16 and can now use it without any counterweights (from naked BGO to 31T5 with Paracorr) but the center of radius of my trunnions seems to be several inches higher than yours.
Thanks! Actually, my trunnions are less than a half circle (less than 180°) so that puts the center of diameter and pivot point about an inch higher than the middle of where the old alloy trunnions used to be. I'm pretty certain it will balance well, at least better than before with the stock alloy trunnions.
Posted 14 November 2012 - 04:06 PM
Posted 14 November 2012 - 04:47 PM
I originally wanted to move the pivot point just a tad over 2" above the factory pivot point but at the same time wanted the base to be as low profile as I can get. I compromised and decided to go only an inch higher instead. This most likely means having to use the FarPoint counterweights which I don't mind as I already have a set of them, besides, they look elegant.
Posted 15 November 2012 - 11:58 AM
Posted 17 November 2012 - 03:37 PM
Amazing craftsmanship !
This will be an interesting thread!
Posted 29 November 2012 - 12:03 PM
The next step is finish mounting up the humongous alt bearings to the Lightbridge LTA.
Posted 29 November 2012 - 01:26 PM
Posted 29 November 2012 - 04:17 PM
Posted 29 November 2012 - 04:22 PM
Posted 02 December 2012 - 12:09 PM
I'm also having second thoughts about the black color of the altitude bearings looking too obtrusive due to their large size. Perhaps they should be white as well so they can blend in with the OTA.
Another mod I will be making is to add a circular strip of aluminum around near the bottom of the trusses, riveting each truss pole to the strip, thus enabling the upper tube assembly and the trusses to be installed and removed as a single, large component, similar to a split-tube dob. Portability is not important for me.
Posted 02 December 2012 - 12:31 PM
Posted 02 December 2012 - 04:34 PM
Posted 02 December 2012 - 05:32 PM
That's a first-class job. Well done. I reckon leave them black - white might get scuffed up too easily.
Posted 02 December 2012 - 05:44 PM
Posted 02 December 2012 - 05:52 PM