OpenBeam Telescope and Fork Mount by dsguice

Last crawled date: 3 years ago

This is a work in progress, most of the optical tube assembly and mount designs are finished. I am currently in the middle of printing and testing these parts. The next steps will be to develop the absolute encoder, the direct drive axial flux motor, and the electronic controls. The idea for the 3D printed direct drive motor came from an axial flux generator which can be found here: https://www.thingiverse.com/thing:687743
The telescope is designed for a 9.75" f/3 parabolic mirror that I've had in storage for a few years now. I'm sure the design could be adapted for a smaller or larger mirror, or even a different optical design like a Schmidt–Cassegrain.
The optical tube assembly (OTA) is made up of 6 OpenBeam aluminum extrusions that should be about 2 feet long depending on the focal length of the mirror. These pieces will be held together by two 3D printed rings; each ring is made up of 6 parts held together by M4 x 20mm socket head cap screws and bolts. The OTA is attached to a fork mount which is also made up of OpenBeam and held together by 3D printed brackets. The mount will be a two-axis alt-azimuth configuration powered by two direct drive axial flux motors. The motors will be controlled by an Arduino Due and use absolute encoders for positioning feedback.
The base or azimuth of the mount is still being designed; due to its larger size and the fact that the motor and encoder must fit compactly together. I hope to have this finished and posted in the next month or two. In the mean time I will be testing different encoder configurations using the Texas Instruments LDC1614.
You can follow along with my testing progress at: www.danielguice.blogspot.com
Parts list:

Amazon:
about 3 spools of 1kg filament (I used mostly Hatchbox 1.75mm PLA transparent orange)
12 x 30mm long OpenBeam
12 x 108mm long OpenBeam
(8 x 300mm long OpenBeam????)
(4 x 400mm long OpenBeam????)
(6 x 609mm long OpenBeam????)
McMaster-Carr:
M4 x 20mm (100 pack)
M4 x 10mm (100 pack)
M3 x 6mm (200 pack from OpenBeam)
M4 nuts (200 pack)
M3 nuts (200 pack from OpenBeam)
47mm OD, 20mm ID steel ball bearing (x2 http://www.mcmaster.com/#5972k45/=zygd14)
Other:
9.75" f/3 parabolic mirror
AstroSystems secondary mirror holder
secondary mirror (2.5"???)
2" Focuser (The focuser board is designed for the Starlight Instruments SIPS focuser)
EDIT 1 (11/24/2015) : Added encoder side bearing plate and encoder OTA plate. These plates are designed to attach a PCB encoder to each. The PCB on the OTA will be the target and the PCB attached to the mount will have the coils and LDC1614.
Also, both the encoder side and rotor/stator side plates are designed to be used with a 47mm OD, 20mm ID steel ball bearing. These can be found on Mcmaster-Carr.
EDIT 2 (1/26/2016): 95% of the OTA has been designed and printed. I have added pictures of this build. Note, the holes for the OpenBeam were test fit with an earlier version and I purchased 12 OpenBeam 2.1 beams for the OTA and mount after printing all of these parts. I found that OpenBeam 2.1 did not slip fit in and that I needed to file/sand these holes before I could put together the OTA. Be sure to test fit a few prints and make changes to the design before printing all of your parts. Also, the OTA pictured here is with the full 1 meter OpenBeam before cutting to size; the OTA final length should be about 10-15 inches shorter.
Most of the parts have been printed with ~45% hex fill for extra strength.
If you have any questions please feel free to ask.