The telescope and astronomy bug was set way back in college. As one of my senior projects, I was assigned to work on the university’s telescope which was in process of being motor driven. The mount (at the time) was a WWII gun mount, complete with alt/az chairs and hand cranks.
After saving for, and not really enjoying my $200 Tasco 4.5 Newtonian equatorial telescope, I updated the focuser (Orion basic rack and pinion 1.25) and bought new eyepieces. The supplied .965 eyepieces had small exit pupils and really hard to use. Also, I changed out the secondary mirror support using PVC fittings and a curved support to eliminate any diffraction spikes. The upgrade allowed viewing comet Shoemaker-Levy 9 ‘black-eyes’ on Jupiter from a apartment parking lot in Houston.
The Tasco was fine to use and got regular usage (backyard, camp outs) but the aperture bug hit. It was time to go bigger. Researching telescope building and buying books (yes, there were books available in the dark ages), the design settled on a Dobsonian mount for a 8″ Newtonian.
Using optics from Discovery Telescopes (8″ soda-lime, f/8 if I recall correctly), and more hardware from Orion, with concrete form tubes and plywood for the base. (It’s amazing to see the quality of wood that you could get from the box stores, comparing to today’s offerings – even plys, few voids, no warping). The secondary uses the same PVC arrangement but could not get the curved spider-vanes to support a larger mirror, so want with 3 vanes. Thinking, ‘3 is better than 4’ at the time, turned out to be a not-so-great moment. 4 vanes gets you 4 spikes – 3 vanes = 6 diffraction spikes.
The TelRad was a real step-up in being able to really star-hop around, compared to the wimpy finder on the Tasco. The 9×50 RA finder hardly gets uncapped anymore.
This was a fun easy project that the kids enjoy.
Using a 20-gal storage bucket (big box store), some scrap lumber/MDF, and some hardware:
The membrane is Tyvek house wrap and massive amounts of duck tape. A piece of all-tread was used to provide the pivot and helps keep the shape better. The ‘pull’ is a wood 2-in ball threaded and attached to the bolt holding the bungee cord.
A fog machine from Party City provides the visual smoke ring.
This was a hit at the Halloween carnivals where ghosts (made from foam core board) were violently knocked over from 15 feet away!
The sailing bug was hatched after graduating. My roommate was invited to go sailing on Lake Livingston so I was able to tag along. Not sure what type boat it was (maybe a Flying Scot as I recall the captain lounging on the aft decking, telling us what lines to pull while practicing a man-overboard drill).
The first hole in the water was a Holder 14′ purchased from a dealer who had many to choose from. Taking a couple friends to sail in Clear Lake on a breezy day without showing any knowledge of what you are doing causes said friends to head down to the Turtle Club instead. After flipping the rudder/tiller into the drink (the bridle was hooked under the tiller, and no clip in the pintle) a committee boat was kind of enough to tow me ashore. After getting back on shore and adrenaline faded, they found the rudder floating and returned it.
The Holder was eventually sold and several boat-free (trouble free?) year passed. I’m not entirely sure what inspired the ‘build your own boat’ thoughts, but reading Duckworks http://www.duckworksmagazine.com/ might have been the cause. I was inspired by the PDR stories during the Texas 200, so several plans were looked into (and the dream of doing the 200). A set of plans for a B&B Core Sound 17′ was purchased.
As with all plans, the direction took a detour when a daysailer appeared on Craigslist for $300. It was in rough shape on top, but appeared to be in good shape otherwise. It was a Helsen Streaker that had at once been modified to have a cabin. Said cabin was now just a hole, and the current owner said too much work and wife wants a cabin. $200 later, it was in the driveway ready to be cleaned out. (Hey, the galvanized trailer had to be at least that much!)
The great rebuild was underway!
The CNC router was a multi-year project. Built out of 3/4″ MDF for ease of working with wood tools, here are some major pieces:
- HobbyCNC Pro (4 axis) driver
- AnTek toroidal power supply
- 3 NEMA 23 steppers
- 1/2-10 acme lead screws
- 3/8″ steel guides, pillow blocks
- approx 16x22x4 envelop
- LinuxCNC controller
- Rotozip router
The overall design was laid out using SketchUp (free version).
The final version looks pretty similar!
There’s a few things wrong with the setup as seen above: the Y axis has a large amount of flex running on the 3/8″ guides, and the router is not too secure with only the bottom clamped down. An attempt was made to keep the y-axis from rotating due to the flex, but didn’t address the unintended z motion. So, the y-axis was redone using homemade (of course!) v groove bearings (sandwiched skate bearings). The x-axis uses the same 3/8 guide bearing setup but since a ‘brace’ passes under the table, bushings are used to prevent up/down flexing. The router bit is centered on the ‘brace’.
An additional clamp was also fashioned to better hold the router.
As for design software, I have been using F-engrave to make signs and convert bitmaps to g-code. CamBam has also been used to make some basic designs for patterns to use with the foundry/greensand casting, but for a later post!
To be done:
- Add solid state relay for spindle switching. Currently using Harbor Freight router speed controller (set to 100%) as on/off manual switch. I have not used the speed control (yet!), and would like to have the router turn off after finishing job.
- Fix the x-axis – there’s something binding at full extents of travel causing some skipped steps.
- Better dust control. Using the hood from the portable dust collector, but still getting dust blown out by the router exhaust.
- Shield lead screws from dust.
- Use this to make the next one!
Here’s a den totem (Just alphabetical happenstance – not that I was subconsciously thinking of adult beverage!) that used the CNC and newly tried welder:
Old cedar fence boards used, and after carving, painted and sanded to reveal the letters.
It is about time that I document some of the random projects that have captured (consumed!) my free time, much to the confusion of some non-engineer neighbors/family (Why don’t you just go buy one already made…). I’ll blame my genes – Teacher + Mechanic.
It’s satisfying to be able to say “I made that” – not in a braggart way, but more as a test to myself to see if I can learn something new, and as an excuse to get a new ‘precious’ (tools)! And not that I will be ever considered an expert at any skill – just that I tried and can relate to the difficulty in becoming an expert in a skill or trade. I found through the years that I did not miss the calling to be a pipe fitter, a master carpenter, a non-starving artist, an astrophysicist….
Stepping into the Way Back Machine…