George RoffeKingwood, TX
"The White Zone is for loading or unloading of passengers only. No Astrophotography." Cosmic Acres! Greatest restoration challenge: Tulley and Sons 3" achromat on Altazimuth mount, circa ~late 1820s
Refractors Reflectors Two Cats A few eyepieces
Nexstar 8se (Garfield)
NPL 30, Elux 25, X-CEL 18, 12.5, & 8
AstroZap Dew Shield
Zhumell red LED keychain flashlight
Celestron Moon Filter
Really bad sense of humor
"Gravity" another word for "incarceration"!!!!!!!
Quote:backlash free lead screws can be pretty expensive.. but they are available off the shelf..
Quote:Why not use a leadscrew?
Quote:It took me a while to find pics of the dovetail R&P focuser on the Zanteson 6" f/5 Jaegers:
Quote: One of my linear bearing units used a micrometer head for focusing.
"A telescope is either good or cheap, not both" - but sometimes you get lucky!
Quote:I wish I could remember the thread from a couple years ago, where some CN member showed a drawing of exactly what you describe, Ed. Only using threaded rod to serve as the rack/worm.-Tim.
Quote:I like the idea of a lead screw driven focuser. How 'bout a sled focuser with a lead screw, including half-nuts like on a lathe's cross slide? You'd have to put the screw on one side of the slide, of course, so you could get the eyepiece in there.
Quote:Nice idea about half nuts,you can disengage and push the slide up or down for rapid transit, re engage and fine up the focus.The arrangement can work without poking your eye out on the focusing knob. Dovetail slides are great of course but you have to be an expert machinist to make one to slide evenly, also the pro slides have adjustment slips built in, and the whole shebang is smeared with goop to make it move smoothly. The R&P CF moves unusually freely for an R&P focuser, there is no goop just mechnical freedom as everything runs on ball races.
Quote:Is it your intention to make an R&P with the tensioning of a Crayford???????? If that is the case, Corect me if I am wrong but I believe it is considered a design flaw to preload an R&P this way. Tooth mesh is not supposed to bottom out and by squeezing it you make it wear incorrectly and it will eventually seize.
Ed Jones ........... The best data is an interferogram, the best analysis is from an honest optician.
Quote:If the intent is to prevent slippage with heavy loads couldn't you just sand blast the shaft and tube areas that are in contact to increase friction or possibly knurl both in one direction to act like fine helical gears?