1200mm Project: Custom Bellows

Bellows Installed 

As can be sees from the pictures, the 1200mm project has the custom bellows installed.

I'm glad that I waited.  I'd received the bellows in mid-August.  I was not fully ready to install as I had not received the material for the front standard and installing the rear standard early would be too limiting.  So I was patient and considered the process I would take.

On Saturday, I was thinking about the measurements required to use the compass attachment on the dremel tool.  Was walking to get some burrito for supper and it was a good opportunity to think about the dimensions and what would be required to make the hole.  The box of the attachment was a bit misleading - it suggested that the device could only carve a circle up to 7 inches in diameter.  I mis-read this and it is actually 7 inch radius.  Still, the thoughts helped me prepare for the task.

No pictures of the actual cutting process.  My work area is the floor of the shed - no table, no vise, no clamp - just what I can handhold and manipulate.  Cutting the delrin was interesting.  The routing bit was able to push through the plastic and there were times when it was going smoothly.  Then other times when I had to back off.  For whatever reason, I did not clamp down the radius as tightly as it should have been and the circle got a little bit too large.  You can see where the ends did not meet up:

The edges were furry and ragged.  I went over the whole thing with a sandpaper block to round them to prevent sharp bits from biting me in the dark.  The brushed look is very attractive.

Putting the bellows on this frame was pretty easy.  I just cut down the end of the bellows - the maker ETone had left extra fabric for me to use.  (I have quite a bit of fabric now for patching.)  Glued this large end to the delrin frame with some strong silicon glue.  Let it cure overnight with a weight providing pressure on it.

Putting the Toyo frame on the small end was muc
h easier than in the past.  I've learned a lot about how to handle this task over the last few projects.  I've learned to trim extra fabric away from the corners and clear the screw holes.  A tiny bit of superglue works well to stick the bellows onto the metal frame before screwing it down.  Super easy and it was done in less than an hour total.

The bellows looked great - the 9 inch square delrin frame is ideal size.

The front standard fit snugly over the back of the lens.  I put a strip of flocking material around the lens so that there was no light leakage.  In thinking, I may need to put a bit more flocking on one more surface just to make sure that there are no additional leaks.  Given the use of this at night I doubt there will be any issues - the path of light around these areas requires a single right angle reflection, so I'm not sure how much could get in.  Direct light shining on the scope body at the flange would be enough - will have to check with a bright light.

Stretchy bellows.

The front standard is glued to the bottom half of the rings.  The top surface has no adhesive and this is the spot that might need some felting.  When I put the scope horizontal again I will check.

Next steps:

Make the dew shield from the aluminum plate.  Not sure if I am going to pop rivet it together or use adhesive.  The pop rivet seems fast and secure - however it will put the ugly bit of the rivet on the outside of the shield - the smooth part of the rivet must be on the inside so that it does not protrude into the light path.  This is where an adhesive would be preferable - no protrusion into the light path to cause diffraction spikes.