made some progress on my belt drive last night, got most of the prototype gears made. tested the grip and meshing with a length of gt2 belt I have spare. fits way better than I thought it would.! this printer is amazing.
ordered a pair of 130mm belts from Brisbane, paid handsomely for shipping so I can get em before the weekend.
will then be a case of sorting out an idler wheel to tension the whole setup.
Ordered my belts on Tuesday afternoon and they arrived this morning.
Australia post would normally take a week from Brisbane so it was nice to have the express bag option albeit pricey.
They appear to seat in the gears really nice.
Tomorrow I’ll be off to the bearing shop to buy some tiny bearings to make an idler wheel to get the belt onto as many of the small primary gear teeth as possible.
So I’ve hit a roadblock. I can make a 9 tooth gear but it just isn’t strong enough. Just keeps snapping. So I’ve ordered a pair of 9tooth gears from Rowan engineering in uk. About 18 pounds a piece. I’m on holidays as of Thursday so hopefully they get here before I go back to work in a month.
In light of this setback, I’ve constructed an Arduino based electric focuser. About 90 percent done. Just a bit of mounting and should be sweet.
Only realised after ordering the 9 tooth pulleys that they are a t2.5 not a gt2 like I was going to use.
Got onto Minature bearings Australia again and they just happened to have 2 of what I needed in stock.
They turned up today and they fit the 2 new 44 tooth pulleys I made nicely.
Hopefully the 9 tooth gears will be here soon.
Rowan pulleys turned up today. Time to reassemble and test.
Going to have to sort out a couple of tensioners though. I have a bunch of small bearings and some idlers I printed out before.
Aaaand it’s finally back together on the ra axis. Printing final gear for the dec axis now. Covers don’t quite fit back on but it’s a matter of millimeters. Some refinement of gear thickness and maybe a wee shave with the die grinder to take a bit of meat out of the mount.
Helluva lot quieter now. Be interesting when I get it in action to see how it goes. Been constantly Smokey here for weeks now. Can’t see any stars at night.
I printed a t2.5 version of the 9 tooth gear. Seems fairly strong compared to the gt2 gears I’d previously printed. Can’t snap it off with my fingers like the first version. Maybe I didn’t need the Rowan gears after all. Oh well.
I have a couple of t2.5 gears for one axis if anyone would like to give em a try. Have to supply ya own t2.5 belt though.
Christmas night we had the smoke blow away for the most part so I was able to test the belt drive out.
first thing is the noise. you really don't realise how loud the stock metal spur gears are..
the goto is 100% unaffected. if anything its even more accurate after a single 2 star alignment..
obviously the backlash has been seriously reduced. still some there but its a lot better. I notice when centering a star it is more spritely changing directions in dec.
all in all cost about 100 aussie bucks.
tonight is looking superb. the smoke has blown off to the southwest and looking at a nice clear night for the first time in a while
had a bit of strife with the grub screws on my printed gears cracking around the radius of the gear when tightened. using a different material to print with will probably be the way to go (carbon fibre or something), instead I just bit the bullet and ordered a pair of aluminium gears.
they are all now installed and working fantastic. just printing the second half of my new covers now and it will all be finished.
Hopefully we will have a clear night tonight.
Not sure if I've read this thread before, interesting reading your journey in astro. Not sure why you didn't go for Aluminium sprockets in the first place, easily obtainable from many sources as you have probably found out.
3D printers are an interesting invention and can do amazing design work but I find it hard to trust printed plastic for mechanical work where there is some load placed on the printed gears, or whatever. Metals are much more durable for most engineering applications, but I'm old school too ! I have machined many items from industrial plastics and they do their intended job but not for things like gears.
