Chriske

these textured formicas have fewer contact points, resulting in a very smooth 'ride'. The 'rougher' the formica, the smoother it will go.
Think of ball bearings. Ball bearings have just point-contacts, That's the reason why they work so smooth.
+ of course, formica is a very 'slippery' material.

Two possible alternatives.

If you own a printer, print a bearing in PLA and use it with Teflon pads. Works even better then formica, done it a few times already the last few years. Most printers do have a 200mm print-platform, that should be enough.

Second , a small shim of shine metal screwed onto a wooden disk. In the rocker a sheet of felt instead of the usual Formica, works surprisingly well also. After a few months you need to replace that strip of felt.  And if you do own a printer, here again you could use that printed bearing instead of that wooden disk/metal strip.

Using one or the other, there is no backlash at all.
I've used all my life formica/teflon. My last telescope(bino) I made a few months back, I did use the combination PLA/felt. That is the best bearing I've ever used on my dobs.

Thanks Gina,

Our HST is about two meters high now, with the front cover(open) it'll be about 2.4m.
Approx. weight of our HST is about 29kg

Sorry guys to chime into this thread, but bevelling a mirror should take no more then about 15 minutes or so.
A few days ago I did a 12", it took me about 20 minutes. Be not afraid to push on that stone.
But : always work with plenty of water and ALWAYS  grind from the inner to the outer side of the mirror. Starting a new stroke, do not hit the mirror hard with that stone.

Today all woodwork done, time now to apply the Mylar, the grips and the last parts around the hull.

Todays job...

Drilling and tapping holes in the grip's brackets...l-o-t-s of it....😳
The holes were printed of course but I need to widen them a little bit.
These grips are all over the place for the astronauts to hold on to.

Finished...

2 hours ago, Stub Mandrel said:

You have made me paranoid enough to do a more accurate calculation!

🤭

You could indeed add some weights in the base of the rocker to have it all perfectly balanced.
That's all there is to.

You'll need to lower the scopes COG to have that platform work properly.
The polar axis must run through the COG of the scope.
 

Did not read the thread, sorry, but I've read something about shims to adjust things.
Well, I'd go for a completely other approach. I would give each separate unit it's own adjustment 'unit'. Each unit needs two screws to control a direction.
If I'm not mistaken, you do have a printer, you can draw(very good imho), so what is the problem...?...😁

On 05/04/2020 at 10:54, Dr_Ju_ju said:

Looking good.... 

I think we need a new Sub-Section of "DIY Astronomer" called "3D files" of ALL types, for all the various bits we design, but don't publish, that others can comment on, refine and even generally use.... 

In the near future I was planning to start a site on the net to do just that.
Making a subsection here on SGL would be a good/better idea indeed.
To make the files more 'user-friendly' it would be interesting posting the source files together with the stl file. When someone want to change the part or project a little bit he needs a work-able file.
The most interesting file would be a STP or STEP file. Nearly all software can import/open  these files.

Sorry about the hijack Gina...😟

Neil,

Did you rebuilt that scope completely using other materials, or is it still the same tube and rocker as in the picture..?

A DarkStar. Good scopes..!!

What scope is it intended for..?

Before applying the Mylar screen to the perimeter of HST I need to drill all these small holes for the bolts to pass through and fasten all grips, attributes...
There are 'a few' holes to drill....😳

Cut a few holes.
The two oblong holes are pointers, (according to a colleague ATM).
The round hole, I need to look up about it's purpose.
And the square holes is a the location were part of the instrumentation can slide out for maintenance/repair. In one of the missions a astronaut takes it out to work on that unit.
planning to hang a few astronauts in the vicinity of that unit.

Great..!!

Today some paintwork

Mounted on it's pole, distance between these two antennas about 1.6m(in our model)

Today's job, laminating solar panels and gluing them onto the sheets of wood. Notice the difference after laminating.
Now waiting for the glue to dry.

Complete length of the 'solar panels' is 4.8m.   (I took the liberty to glue solar panels at both sides.)

I still was undecided what to use to cover up that telescope-part of HST.
While in search for a completely other item in my workshop I found this. it must be about 20years (or so) old. But still in good shape. A rescue-blanket.
The only thing I'd like to try and minimise is that square shaped pattern in that blanket.

On the other hand it 'has' something. I can't explain.
Maybe I'll go for this (mylar?) screen.

Woow... Got a picture...?

Maybe so, and there are far more things I'd like to know about HST.
I did sent mails to NASA and also to ESA. We wanted to know more about all these parts screwed onto and sticking out of HST's hull.
But no one bothered to answer our mails.

My point is, when that thing hangs in our local observatory and visitors start to ask questions about HST.... well... I think it's quit silly having made a copy of HST, not knowing what we printed, not able to explain the purpose of all these objects around HST.