Weekend Update on Fabrication

 The team was busy all last week machining many of the components for the telescope. In particular, the secondary mount structures were mostly completed. Below is a selection of images of the parts machined by the team.
This upcoming week we will focus on the primary mount, and hope to complete the frame, backing plates, adjustment screws, and mirror strap holders. By the end of the week, with any luck, both the primary and secondary mirrors will be able to be positioned within the telescope.

The completed base of the secondary mirror mount. Radial symmetry is essential.

The secondary brace ring. Note two of the three needed plates complete on the central structure.

The connection points for the mirror trusses and spider veins. Slight modifications were made to the designs to ensure a more secure connection. This was an interesting example of engineering principles and machining practicality coming into conflict.

The completed secondary ring, with carbon fiber 1" diameter leftover tubes added for scale.

Material is removed from a scrap part to make the connection piece between the spider veins and secondary mount. The pictured beam is approximately 2" thick.

The central secondary structure, with no attachment points for spider veins. Because it screws into the secondary mount, the inter-mirror spacing will be slightly adjustable.

Adalberto machining the secondary structures.

Note the thin grooves in which spider plates can be fitted. This part was completely modified from the original design, as the plans were aesthetically appealing but not possible to machine with the available tooling. The new design uses L-beam sections in place of curved pipe segments.

The view from above. Note the extremely narrow yet uniform spacing of the L-beams, requiring precise alignment.

New Team Member

The telescope team is pleased to announce the adition of Adalberto Perez to the telescope team. Adalberto is a member of the class of 2015, and comes from a small farming town in Arizona called Aguila. Adalberto's experience in high school taking pre-engineering classes paved the way towards his goal of becoming a mechanical engineer, and also have given him expertise with CAD and machine tools that fills a valuable skill vacancy in the telescope team lineup.
Adalberto has already made invaluable contributions to the mechanical design and fabrication of the telescope. His work has been an integral step towards building the CAD model into a workable design, and his vision and dedication to the project has been outstanding.

Mechanical Fabrication

Over the past two weeks many of the telescope's mechanical components have been undergoing fabrication and finishing. In particular, the secondary mirror alignment and support structures have been a major priority due to the large number of component involved and the complexity of the apparatus. Most of the adjustment mechanisms have now been constructed, and the team is evaluating fabrication options for the spider mount sheet metal work.

Adalberto milling a secondary support bracket.

Another major project has been telescope metering. We have now cut the carbon fiber tubes to their appropriate length, and constructed mounting platforms for the primary mirror box and upper outer secondary ring. All that remains for this part of the telescope is to mount the ball and socket joints to the platforms. Once this is done, the telescope will start to look more like the finished project.

Attachment point for the truss ball-and-socket joints

The schedule for components now has most of the mechanical fabrication done by the end of June for the components already put into CAD. The only essential portions of the telescope still left to be designed and fabricated are the tertiary mirror mount and focuser holder.

Primary mirror box with attachment points.

Primary Mirror Repairs

On Wednesday April 27th, we received our repaired lightweighted primary mirror blank from ITT Geospatial Systems who generously donated time and money to the repair of the part. We received the part in September with cracks around the outer part of the mirror as shown below:

ITT sandblasted out the cracks such that the mirror now looks as follows in the areas where the cracks existed:

With the cracks removed the mirror is now less susceptible to damage in the grinding and polishing process as well as to damage due to random loads in everyday use. With the repairs completed the mirror is now moving to Optimax who generously agreed to grind and polish both our primary and secondary mirrors to the best fit sphere (the primary and secondary mirror are both hyperbolas, so before directly polishing to the hyperbolic shape, we usually polish to the best fit sphere). After Optimax finishes the work on the part, it will then pass to QED who graciously agreed to aspherize (figure to the hyperbolic shape) both our primary and secondary mirrors. Finally, at the conclusion of that process, Accucoat has agreed to donate their services to put a reflective coating on our mirrors.

Primary Mirror Mount Design

The team has completed a preliminary design for the primary mirror mount.  The design utilizes a floating 9 point mount composed of three brackets with "V" grooves underneath.   The brackets interface with the existing holes on the open back of the light-weighted primary and exactly constrain the primary mirror.  The PM mount will have 3 differential screws allowing for tip / tilt and piston adjustments.

The optical tube assembly with the PM mount attached to the hexagonal PM casing.

An isometric view of the top of the PM mount.  The three cylinders protruding from the sides are meant to interface with three V grooves on the bottom of the hexagonal casing. This kinematic constraint allows for repeatable mounting and demounting of the primary mirror. 

The PM mount as viewed from underneath.

-Joni

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Mechanical Design Update

The overall mechanical design has been updated to match vendor parts as they keep coming in. Below is a rendering of the most up to date CAD model.

Procurement/Construction

Currently we are procuring parts in anticipation of mechanical design completion in the next few weeks. We appreciate all the support of our sponsors, faculty, friends, and family and cannot wait to unveil our completed scope.

-Alex