Back in 2008 I made a new kite winder. It was based off of a design posted to the KAP Forum by Eric Kieboom, a fellow KAPer from The Netherlands. Eric’s design is a lot lighter than what I built, but I designed mine to be able to wind under appreciable tension. It’s been a great winder so far, and it’s still the one I carry around in my bag.
But good designs are good designs. At times people need to wind more than just kite line.
Up until a couple of months ago CFHT only had one cassegrain instrument: Espadons. It’s a fiber-fed spectrograph that takes starlight, passes it through a polarimeter unit on the bottom of the telescope, and then feeds it into a fiber that guides the light two floors down in the building to the spectrograph itself. Since Espadons was the only instrument we ever installed on the bottom of the telescope, we never bothered to take it off. Our other two instruments operate at prime focus, so Espadons just stayed where it was.
That all changed when we received a new cassegrain instrument: Sitelle.
When Sitelle goes on the telescope, the Espadons polarimeter must first be removed from the telescope and the fiber must be stowed. We had a fiber storage box on the telescope, but the bend radius inside the box is tight, and we’ve never been entirely happy with it.
Added to this we’ve got a third cassegrain instrument in development: Spirou. Spirou is another a fiber fed spectrograph designed along similar lines to Espadons, but for use in a different wavelength range: infrared. Because Spirou operates in the infrared it uses fluorite fibers rather than glass fibers to guide the light from the polarimeter to the spectrograph. Fluorite fibers are much more fragile than glass fibers, so the small bend radius in our fiber storage box wasn’t just uncomfortable. It simply wouldn’t work. We had to come up with a new way to store our fibers.
I was stoked when I learned I’d get to design the fiber reels. The first thought that came to mind was Eric’s kite winder, and the winder I made for myself based off of his design. Why not make Eric-inspired fiber reels, too?
I had to scale up the size of the winder plates to give me the bend radius I needed for the fibers. The reels don’t need to hold the large volume a typical kite winder needs, so I moved the bolt circle outward. This also gives us better options for securing the fiber to the side plates with Velcro.
Machining side plates like this is possible using traditional lathes and mills, but there are better methods out there. In this case we had the plates made by the folks at Dix Metals, using their water jet machine. We ordered ten plates, of which three were slated for cassegrain fiber storage, at least three were slated for the caisson centrale fiber storage, and the others will stay in their box in case we want additional reels anywhere else on the telescope.
The rest of the reel was built out almost exactly the same way as my kite winder, using bolts and posts to space the plates the proper distance apart. In this case I made 2″ spacers, drilled one set clear, and tapped the other set to take 1/4″-20 bolts. Long bolts come from one end, and shorter bolts from the other. The whole thing is attached to the back of a 19″ electronics rack.
Sitelle goes back on the telescope at the end of December. The Espadons fiber will be stowed in one of the two slots on the reel. The other will have to wait until Spirou arrives. Meanwhile I’m building out the fiber storage for the caisson centrale.