22" F3.38 DIY Scope Build

[michael.h.f.wilkinson]

Wonderfull build!

[nightfisher]

Wow, this build is coming along very nicely and pretty darn quick, if i were to build a big dob, at least i can get the plywood at cost +10%, hany being a driver for a big plywood importer

[jabeoo1]

This looks like an absolute monster.  Its going to blitz the deep sky.  Great stuff 

[SimonfromSussex]

Thanks everyone.

I assembled the cell yesterday, just gotta let the glue dry and then I'll put up some more pics.

Bit more ordering today on little bits & bobs: plastic for the secondary cage (thanks 4 the help Steve), heat shrink for the truss tubes and some skate board bearings which we are going to try and work into the base bearing.

Hopefully we can start final assembly very soon.

[JRM]

Simon,

I have a set of 8 skate board bearings here I was going to use on my 20" as well, will be watching to see 

how you incorporate them into the mount, have yet to make plans on construction here but that day will

come,still looking for ideas...

following with interest, keep em coming.

Rick M

[SimonfromSussex]

Another really good day today and we got to an optics test by the end of the day which was brilliant!

Still lots of little bits to finish but we are not far off now.......

Started today with some work on the cell, firstly fitting the frame into the mirror box:

Then loctite onto the screws to hold together the metal flotation bits:

Putting all the cell bits together (there is a circle to fit to these to hold the triangles in the right place but we wont put that on untill after painting):

Alan has put together some amazing clamps to hold the lower truss poles, they fit inside the box and were really rigid when we tried them today:

The cell and clamps in place:

[swamp thing]

That sling looks kinda neat Simon. Very tidy mate. Hmmm! I can see an upgrade coming to mine.

[Daniel-K]

Comon si DFII aint far away!

[estwing]

makes mine look tiny!

[SimonfromSussex]

We decided to fit the bearings with m8 stud and thumb screws so they can be removed for transport (hopefully saving some weight when lifting)

First the holes were drilled:

Then we screwed in some threaded inserts:

The bearings in place:

We added formica to these and they ran really well.

When assembled today, the scope is bottom heavy (as the maths predicted) but even though it was, these side bearings worked a treat, lovely and smooth with no judder or jolt. 

Once the secondary cage is complete we can add weight if need be to balance it.

Then we made the bottom bearing, we have only done this roughly for the time being to test the scope.

Teflon pads from astrosystems and then Alan had some formica.

The plan is to add skateboard bearings but we wanted to test the friction first.

As it turned out the bottom bearing was quite stiff so we will have to have a play with this:

 

Finally the top cage brackets were fitted (from astrosystems).

Wooden dowel is hammered into the top of the poles, then they are screwed up.

[SimonfromSussex]

Optics in and we were ready for a quick mirror test and to set up the pole lengths for my eyepieces.

I have to say the trees in the distance looked really sharp!!!

Alan made the light baffle last thing today and I heat shrunk the poles black, need to trim up tomorrow.

Lots of tinkering still to do and obviously need to paint it (somehow) but very close to a proper first light now.

I'm one very happy boy tonight!!!!         

[SimonfromSussex]

That sling looks kinda neat Simon. Very tidy mate. Hmmm! I can see an upgrade coming to mine.

Cheers Steve, the only thing is, being wood, it does add more weight!!

[SimonfromSussex]

Comon si DFII aint far away!

Should make it Dan, oh please let the skies be clear!!!!!

[Moonshane]

amazing build. I must invest in a biscuit jointer

[estwing]

Should make it Dan, oh please let the skies be clear!!!!!

well if its not we've got a bunch of beautiful scopes to look at!

[swamp thing]

very  nice Simon.

Thats one fat scope, lovely 

[astronymonkey]

Really good thread, but im not sure how the sling works etc any chance of an explanation ?..

Cheers

[faulksy]

that is brilliant simon so so happy for you mate, and top work by alan, as calv says i think there will be a few pms going either alan and your way or to steve, cant wait to see it in the flesh. not long now.

[SimonfromSussex]

well if its not we've got a bunch of beautiful scopes to look at!

There is going to be some glass there Calv, that's for sure!!

[SimonfromSussex]

Thanks Steve/Mike

Yes, mainly Alan's handy work / direction, I'm sure he is more than willing to take more orders......................?

[SimonfromSussex]

Really good thread, but im not sure how the sling works etc any chance of an explanation ?..

Cheers

So it's a wooden base (rather than a metal one which is usual).

It's screwed into the mirror box using pivot metal blocks one side and then triangular fixings the other, this allows the tailgate to be dropped to service and or take out the mirror easily.

There are then three collimation screws from the bottom that firstly screw through a normal nut that is loctited on:

then there is a square nut on top of that:

The x6 floatation pads are screwed onto the x3 bars using an oval washer that lets them rock slightly:

Then these bars sit on the square nut and are screwed tight to it.

As you turn the collimation screws at the bottom the square nut raises up and down the shaft allowing adjustment.

The mirror "floats" on the 18 pads that are attached to the six triangles.

It is held in place by the sling (thin black wire) the mirror sits on this, more so when looking horizontal, less so when vertical.

The idea is it floats so there is no distortion to the mirror.

Hope that helps Astromonkey? 

[astronymonkey]

Cheers simon,

I understand the floating cell bit but what puzzles me is the wire sling bit, does this just loop around the edge of the mirror to act as a wire hammock for the mirror when horizontal ? If so I wondered how you managed to stop any movement in the mirror when moved from vertical to horizontal whatn theres nothing actually holding the mirror as such ?

Cheers

[mapstar]

Very solid looking and progressing rapidly Simon

The truss attachments are a good idea and something I've seen before think on the Sumerian scope's?

Just a couple of question's.

Did you mount the alt bearing attaching knobs on the inside for a specific reason? Aesthetics?

What finish are you going for? I've gone for varnished wood with black on the cut outs like the Sumerian style scope's.

Had the full assembly built up last night on the patio with the 33kg primary in.Bearings work well with just teflon and formica. Few more tweaks and it will be there ready for some pictures.

As others say first light nearly there

Damian

[Glasspusher]

Excellent stuff, following with great interest and looking forward to your first light report.

John

[Chris]

It's unreal how quickly you've built this monster dob! Looks fantastic too!