Adjustable pressure clamps for Hadley telescope altitude bearings

These are spring loaded clamps for the “standard” plastic frames and tubes base included in the official Hadley telescope model and its metric remix version. 

The clamps are based on M4 hardware left over from my metric build, but will work with either version (if interested in doing an imperial remix or any other variant, I added here the Fusion360 file too).

With a wooden mount for these telescopes you can add one or two springs to the bearings. These clamps achieve a similar effect on the standard base, applying a constant (And adjustable!) pressure, making the movement a bit stiffer and reducing shake and drift. 

In my experience, one clamp already works if all you want is a more comfortable operation, but should you wish more holding power, I included a mirrored version of the lower jaw, so you can have one on each side (the inner edge of the frame starts curving past the center point, so it must be mirrored). 

Print with a high infill (I did mine at 40%) and use PETG for higher layer adhesion if you can. I tried my best to manage the forces these clamps are subject to by making the clamps befier and adding some design features (see the photo of the small pile of earlier versions), but they will still have to bear some load along layer lines unless you print them on the side using supports.

As a side note on this, the little lip on the lower side of the upper jaw (see picture) serves to counter the deformation of the clamp as the tightening increases. The tips of the jaws would tend to spread apart on the open side, and that little lip makes contact first and balances the deformation, helping to keep the jaws straight and in full contact also when tightened. Different plastics may behave differently so you can file it a bit or add a tiny piece of tape under it if you feel like it needs adjusting.   

To put the clamps together, aside from the printed files, I used an M4x50 bolt and M4 nut, 2x M4 washers and a spring (3d printer bed leveling spring off amazon, same as I used for the telescope mirrors).

The washers are optional, but help preventing the spring from biting in the plastic.

Another thing you may want to consider is using a nylock nut instead of a regular nut, since you may have some of those lying around too. The well on the upper jaw is a bit deeper for that purpose, but it is not mandatory.

Once the clamp is assembled, you can leave it with the spring loose and it should snap in place happily, tghen you tighten it to your liking.

I think you may also do without a spring at all (maybe with a shorter bolt so it doesn't stick out like a sore thumb), but then any adjustment in the holding strenght will be provided bu the elasticity of the plastic itslef. It may be a bit hit and miss, and also shorten the life span of the clamps or break them altogehter if you overtighten. 

Finally, the plastic on plastic contact can only go so far with attrition. If you need to increase the grip and lock the thing in place more securely (for example to counter a heavy camera), you can try adding a piece of electrician tape or something even more grippy on the inside of the curved upper jaw.

It was not needed in my tests, with both clamps on, and tightened just partially it managed to hold my Olympus OM-D M5 II just fine up to a little below 45 degrees, beyond that additional tightening was required, but with the springs fully compressed it managed zero degrees without hitting the frame, depending on what you need to attach your mileage may vary of course.