Zhumell Z100 100mm f/4 Newtonian

[Alan64]

Utilising mostly craft-foam and a bit of flocking, the flange of the focusser is now complete...

Craft-foam is made of EVA(ethylene-vinyl acetate), as are the mid-soles of athletic, running shoes, so that should be quite durable.  With those materials added, I will need to go to my local hardware and get three slightly-longer M4 screws to compensate.

I suppose I can tend to the last two aspects until then: the finder-base and the dust-cap.

[Alan64]

I don't really know how I ended up with a fourth nut, painted satin-black at the factory.  It may have come from another kit, but it was in the bag where I dumped the screws and what-not for this telescope.  In any event, I have a spare in case I lose one.

The nuts and lock-washers for securing the focusser to the tube have been sanded and washed...

...and next to be matte-blackened.  It's cold outside, and I don't want to spray paint indoors...

[Alan64]

It's a bit warmer today, with the cold-snap over the last week having finally subsided.  The nuts and lock-washers are now blackened, hence the focusser is ready to install...

It's difficult doing this sort of work during the winter.

[Alan64]

The telescope is beginning to look like its old self again, and with its focusser installed...

To ensure that the tips of the new screws would not jut into the light path, I combined #6 stainless-steel flat-washers with the screws on the outside, for a bit of lift.  They also allow for a greater area of plastic to be spanned so as to reduce cracking or splitting in future...

On the inside, indeed, the tips of the screws barely extend past the nuts...

Afterwards, the tips were matte-blackened...

The focusser is completed.  The materials used for the focusser's flange improve the seating of same onto the tube, and with less flexing and tension, of and on the plastic.  The materials also serve as a shield against dust when the telescope is stored...

Now to move on to the finder-base...

[Alan64]

I have the new finder-base positioned here... 

Isn't it lovely?  If you don't think that it is, but dead-common instead, please reply to that effect.

Those screws are too long.  I'll need to saw them down a bit.  

I don't know the mil, the thickness of the tube's wall, but I suspect that it's the same as that of many of my other larger and smaller entry-level telescopes.  Given that, I don't see the need in adding a reinforcement plate on the inside for the base.  The tube is not that flexible, at that diameter, just shy of 115mm.  I think that in this instance a flat-washer and a lock-washer before each nut will be adequate.

Yes, indeed, this type of base is going to be a bit over-kill, but I will be looking to swapping between a 5x24 optical or a red-dot, so it will serve for at least that versatility.  I can't see attaching a 6x30, let alone an 8x50.

[Alan64]

I felt the need to reduce the thickness of the M4 nuts by half, transforming them into jack-nuts.  This will ensure that the combined thickness of the two washers and nut, each, will not jut into the light-path...

Next will be to determine the final length of the screws, and then to roughen and matte-blacken the components.

[Dr_Ju_ju]

instead of the bolt\screw body coming down into the tube, have you considered reversing the bolt so that it goes outwards into the guider mount, which could then be suitably tapped for the bolt ??

[Alan64]

4 hours ago, Dr_Ju_ju said:

instead of the bolt\screw body coming down into the tube, have you considered reversing the bolt so that it goes outwards into the guider mount, which could then be suitably tapped for the bolt ??

The base has long, open slots in line with the holes of the tube...

There is that.  It is what it is.

I suppose one could tap holes perpendicular to the slots, but then they'd have to drill two more holes into the tube, and precisely, in two directions.  

The only area I'd really want to tap is the side opposite of where that thumbscrew is, and then to place the thumbscrew there, away from the focusser; the stuff of dreams.

But then, I don't have a tap-and-die set, either metric or standard.  I've seen them at the hardware, and aluminum is not that difficult to do.

By the by, very early this morning I had the second screw cut, but it was a hair too long, so I clamped the head of the screw into my vise-grips and began filing the tip down.  All of the sudden, the grips snapped open and the screw flew off into oblivion.  I spent almost an hour searching for it, but to no avail.  So, today I'm going out to my local hardware and get a couple more...

...or should I get three?

Edited November 18, 2019 by Alan64

[Dr_Ju_ju]

You could use a square nut, which just drops into the slot.... That's if they are available ??

[Alan64]

12 hours ago, Dr_Ju_ju said:

You could use a square nut, which just drops into the slot.... That's if they are available ??

I could probably get those locally in zinc-plated steel, but not in stainless.  Then, the undersides of the heads of these screws do conform to the shape of the slots' wells, although not perfectly as though the two were one.

I did go out the next afternoon; glamour shot...

Ever so lovely they are.  Would that I had had them right after that one had flown into space.  I'd be done with it already.

Edited November 19, 2019 by Alan64

[Dr_Ju_ju]

FYI, stainless steel square nuts are available, even in black https://www.ebay.co.uk/itm/BLACK-STAINLESS-STEEL-SQUARE-NUTS-A2-70-Stainless-Steel-M5-M6-M8-M10-M12-DIN-557/222399060187?var=521268372603

[Alan64]

4 hours ago, Dr_Ju_ju said:

FYI, stainless steel square nuts are available, even in black https://www.ebay.co.uk/itm/BLACK-STAINLESS-STEEL-SQUARE-NUTS-A2-70-Stainless-Steel-M5-M6-M8-M10-M12-DIN-557/222399060187?var=521268372603

Is that what you use?

[Dr_Ju_ju]

at times, yes, especially when I want a lower profile head in the light path....

[Alan64]

5 hours ago, Dr_Ju_ju said:

at times, yes, especially when I want a lower profile head in the light path....

In this instance, the spacing between the inner wall of the tube and the edge of the primary-mirror is at least 5mm, all round.  Not a great deal, but enough to conceal the hardware that I'm utilising, and at a total thickness of 4mm.

[Alan64]

Oh Julian; yoo hoo...

...and both assemblies at 4mm in thickness; therefore no intrusion into the light-path.  It turned out that the shorter-length screws that I had bypassed initially, there at the left, were the perfect length after all.  Oh well, all's well that ends well.

[Alan64]

The hardware has been filed and sanded, roughened, for the paint...

[Alan64]

[Alan64]

[Alan64]

Next up, the installation of the cowling with its secondary-stalk and -mirror...

[Alan64]

I had gone to all of this trouble...

...and for naught, as the combined jack-nuts and lock-washers are just a bit too thick, and would intrude into the incoming light-path towards the primary-mirror.

I then thought I might get by with the original screws...

...but two of the plastic, threaded holes of the cowling; one is totally stripped-out, and the other nigh to that, so there went that idea.  Good thing too, as I really didn't want to use them after all.

I went out earlier today to my local hardware, and got just the thing, or things rather...

The black-oiled screws, with their shallow heads, will be inserted from the inside of the tube, and with the stainless-steel hardware on the outside.  The lock-washers will be sandwiched in between the acorn-nuts and the flat-washers.

Oh Julian; yoo hoo!  You were prophetic, sir.  A prophet in your own right...

Even though I did not utilise your method for the finder-base, I am to employ it for securing the cowling.  Thank you for mentioning it, as it undoubtedly influenced the outcome.

[Robert72]

On 18/11/2019 at 17:52, Alan64 said:

The base has long, open slots in line with the holes of the tube...

There is that.  It is what it is.

I suppose one could tap holes perpendicular to the slots, but then they'd have to drill two more holes into the tube, and precisely, in two directions.  

The only area I'd really want to tap is the side opposite of where that thumbscrew is, and then to place the thumbscrew there, away from the focusser; the stuff of dreams.

But then, I don't have a tap-and-die set, either metric or standard.  I've seen them at the hardware, and aluminum is not that difficult to do.

By the by, very early this morning I had the second screw cut, but it was a hair too long, so I clamped the head of the screw into my vise-grips and began filing the tip down.  All of the sudden, the grips snapped open and the screw flew off into oblivion.  I spent almost an hour searching for it, but to no avail.  So, today I'm going out to my local hardware and get a couple more...

...or should I get three?

Please excuse the late reply, I have not been following too closely of late.  Could the finder base not be rotated by 180 deg. in order to facilitate the thumbscrew away from the focusser?

[Alan64]

1 hour ago, Robert72 said:

Please excuse the late reply, I have not been following too closely of late.  Could the finder base not be rotated by 180 deg. in order to facilitate the thumbscrew away from the focusser?

Yes, but then I'd have to notch out that side for the finders' alignment-tabs...

...which I can do, easily, but then the thumbscrew would be forward, and would not batten down at the stalks entry-point, if that matters really, I do not know.  In any event, for me, it's more of an aesthetic concern rather than one of practicality.  I have relatively small hands, so it's of no real consequence.

I do have this finder-base...

...but that one is for my Maksutov.  It's not notched, however I just may notch it out before its installation.

Edited November 23, 2019 by Alan64

[Dr_Ju_ju]

Prophetic, no, there are just loads of different ways of doing things stashed away in the grey cells, that I picked up over the years, especially in my early career, where doing things quickly\cheap\safe& secure\long lasting etc. ruled the day\project....

[Alan64]

6 hours ago, Dr_Ju_ju said:

Prophetic, no, there are just loads of different ways of doing things stashed away in the grey cells, that I picked up over the years, especially in my early career, where doing things quickly\cheap\safe& secure\long lasting etc. ruled the day\project....

Nonetheless you did forecast the solution for the cowling.  Had you not made merry mention of that, I probably would've gone ahead and used those jack-nuts and lock-washers on the inside.  Thank you again.

I now have to remove 4mm from the ends of each screw.  I may grind down the heads a bit, for an even lower profile, but only as long as I'm able to retain enough depth for a hex-key to grab still.

[Alan64]

One down, two to go...