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80mm long focal length refractor

savarin

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#1
I came into possession of a matched pair of Jaeger 83mm dia lens of f15 focal length.
Although a focal length this long is somewhat against current practice I thought it might make a good project.
As this project is a long one I thought rather than just put the odd bit in the “what did you do in your shop today” I would do a complete build blog in case it might be of interest to others.

I started by making a 3d model with the full light cone to give me all the dimensions and hopefully how I could fit it all together.
scope2.jpg
Most amateur telescope makers start with the scope then go on to the mount.
I wanted to check out a few things so opted to start with the mount first.
So a quick render of how I wanted the feet.
feet.jpg
And the following welded structure came about times 3
foot1.jpg
Todays job was drilling and tapping the end for the eye bolt.
The screw and knurled knob is to angle the leg downwards to adjust the central pier to sit perfectly vertical.

scope2.jpg feet.jpg foot1.jpg
 

savarin

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#2
As conventional tripods have to be massive and heavy to stop flex and twist I went down a different route with a tall central pier with wide feet and using guy wires to tension the feet. I felt this would produce a solid base and such seems to be the case so far
base.jpg
The base is 3 angles from 25x10mm steel welded onto a 12mm thick steel disk turned to fit inside the central pier.
I cast and turned a chunk of aluminium to fit inside the pier as well. This is bolted to the base with a 14mm long bolt to provide a solid unit. plug.jpg
The three feet pivot in these.
and these pads pivot on the ends of the feet.
foot pad1.jpg

feet2.jpg
After I built the ball turner I made the brass ones for the adjusters, hollowed the bolt heads and rounded the other heads off.
feet.jpg

base.jpg plug.jpg foot pad1.jpg feet2.jpg feet.jpg
 

savarin

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#3
The contoured aluminium spacers I made the same way as these brass ones.
flycutter.jpg
The bit is set at the radius of the outer tube dia. Drilled, flycut then parted off, repeat again.

flycutter.jpg
 

12bolts

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#4
Nice work Charles,
Looks good. Does tensioning the guy wires happen after you have levelled the column/feet?
Will the guy wires run to the eye bolts on the ends of the feet?

cheers Phil
 

savarin

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#5
Nice work Charles,
Looks good. Does tensioning the guy wires happen after you have levelled the column/feet?
Will the guy wires run to the eye bolts on the ends of the feet?

cheers Phil
Thanks Phil,
as to tensioning order I am not sure what will be best, probably level then tension. They only need just over finger tight to work. I feel a knurled ring about 25mm dia fitted over the middle of the bottle screw will aid in this. (and maybe look cool)
I only finished installing the wires and eye bolts yesterday.
I would like to take this opportunity to thank Rob Herd from http://www.steel-fittings.com/miami_stainless/index.htm for all the help and patience in making up the wires and tensioners. Nothing was too much trouble. No affiliation to the company just a very satisfied customer.

I used hooks at both ends for ease at night with no tiny clips or parts to lose in the dark.

At the bottom

bottom guys.jpg

and at the top

top guys.jpg

Those little brass washers are the ones I was contouring above.
The black paint is only a quick spray to stop rust. All the black parts will eventually be powder coated.
The azimuth bearing at the top is a casting turned to fit a set of taper trailer bearings

az-bearing-bits.jpg

az-on-the-post.jpg

A flat plate will be bolted to this with the altitude bearings on it.
I will replace the nuts with nylocs once Ive finished playing around.
The eagle eyed amongst you will notice the porosity in the castings.
I will be making this unit again with some "wheelium" and degassing tablets in the hope of getting a solid cast that can be polished.
I also screwed up the alignment of the three fixing bolts. All three are out just a tad so they dont lay flat on the contoured aluminium washer. (no photo)
Still, there is room to re-drill and tap them again.

bottom guys.jpg top guys.jpg az-bearing-bits.jpg az-on-the-post.jpg
 

12bolts

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#7
Charles,
Do you think the tension on the guy wires will upset the levelling?

Aside, on my recent handle castings I melted a fair amount of ally, and because it was a larger amount in the pot I doubled the amount of dry chlorine degas i usually use. It has given me a much better finished product. I did notice the "out of the mold surface" was a lot grayer and more textured than I have got in the past but I am thinking now I have just not been using enough to degas properly.
But if I melt half the qty of ally and use half the qty of CL then it doesnt degas properly? So maybe I need a specific volume of CL to get the required reaction?

Cheers Phil
 

savarin

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#8
Charles,
Do you think the tension on the guy wires will upset the levelling?
Probably but the adjusting knobs on the feet have plenty of leverage to add more tension.

Aside, on my recent handle castings I melted a fair amount of ally, and because it was a larger amount in the pot I doubled the amount of dry chlorine degas i usually use. It has given me a much better finished product. I did notice the "out of the mold surface" was a lot grayer and more textured than I have got in the past but I am thinking now I have just not been using enough to degas properly.
But if I melt half the qty of ally and use half the qty of CL then it doesnt degas properly? So maybe I need a specific volume of CL to get the required reaction?

Cheers Phil
what type of chlorine do you use for degassing?
 

12bolts

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#9
Just dry chlorinator granules for pool use

Cheers Phil
 

savarin

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#10
Good day today.
Picked up the aluminium plate and the aluminium tube for the scope body.
Also re-drilled and tapped the three holes in the azimuth casting that I had buggered up before.
Now they are on the diameter and bolt up flat.
How? with a highly precise mark one eyecrometer.
 

savarin

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#12
First job with the 10mm aluminium plate.
2 large flanges to make the clamps that hold the scope.
I opted to document all this for the thread on cutting aluminium plate and as I didnt want the hassle of cleaning up all the fine swarf from the table saw I elected to use the jig saw. Not as clean cuts but still pretty quick.
I've kept the dates and times on the photos so you can see how quick the cuts are.
Rough marked out on the 1500x160x10mm plate
flange1.jpg
first cut with the jig saw approx half way through
flange2.jpg
finished, 2mins
flange3.jpg
long side and 4 corners off, 14 mins including a blade change for the saw.
flange4.jpg
Using a hole saw on my p#$% weak drill
flange5.jpg
at last we're through. This is probably the longest part to do. I seems to take forever particularly when the drill stalls easily at it slowest speed but highest torque. Also incredibly messy.
flange6.jpg
Into the lathe and turn round, 2 flanges. Now I have to mount them to the face plate and bore them out to just over 80mm for the tube and some foam padding.
flange7.jpg

flange1.jpg flange2.jpg flange3.jpg flange4.jpg flange6.jpg flange5.jpg flange7.jpg
 
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savarin

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#13
The two flanges bolted together with four 8mm stainless rods.
Now I have to bore the holes for the tension screws, mill the sides for the 8x40mm strips (cut on the table saw) that will bolt on and hold the bearing trunnions and then split them in half.
Thinking again about all this I have a feeling I should have drilled the plates for the clamp bolts then split them whilst they were still square, then turned and bored them.
If it doesnt work I will revisit and do it again that way.

scope clamp.jpg

scope clamp.jpg
 

savarin

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#14
Took a break from the stand etc and made a sun finder.
A quick dive into the scrap bin came up with 3 off cuts of 12mm thick aluminium and a bit of thin tube.
I wanted the sun end to fit into the tube with a 1.5mm dia hole but how to hold the off cut.
Centre popped the middle and held it tightly against the chuck jaws with the rotating centre and some double sided tape.
double sided tape turned.jpg
Drilled with a 1.5mm dia for the sun to peep down and made it an interference fit into the tube.
sun end polished.jpg
The sun spot has to hit an opaque screen at the other end of the tube so the screen holder needed a threaded insert to hold it in place.
ext int thread.jpg
Made a small internal threading tool and cut a 0.7mm thread inside and on the outer clamp ring.
internal threading.jpg
The screen is cut for a plastic milk bottle, scratched with dividers and inked.
screen end.jpg
Then I polished the lot.
finished.jpg
It works a treat. now back to the stand.
sun spots.jpg

double sided tape turned.jpg internal threading.jpg ext int thread.jpg screen end.jpg sun end polished.jpg finished.jpg sun spots.jpg
 

12bolts

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#15
Nice work Charles,
Did you use the double sided tape and centre because of the lack of a 4 jaw? And then hold the round to cut the centre out?
Thats a pretty high polish inside the "cup" Im impressed with the finish!

Cheers Phil
 

savarin

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#16
Nice work Charles,
Did you use the double sided tape and centre because of the lack of a 4 jaw? And then hold the round to cut the centre out?
The off cuts were too small for the 4 jaw (original piece of crap) so I used the tape and centre. Then mounted the now round piece in the 3 jaw and used the bearing pusher to get it aligned flat, turned down the push fit part for the tube, reversed it to drill the small hole and bore out the taper.
The other two pieces for the screwed end were drilled first, both mounted together on a long bolt trapped in the 3 jaw, turned to size then individually bored and the threads cut.
Thats a pretty high polish inside the "cup" Im impressed with the finish!
Thanks, 600 wet and dry with wd40, then 1800 jewelers abrasive paper and wd40 then solvol autosol.
There are still some marks left so when I set the polishing wheels back up and use tripoli followed by rouge then all the marks and micro scratches should disappear.
 

savarin

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#17
Back to the stand and bits.
Milled the side slots out of the rings using a small end mill I had been given years ago and my vertical slide.
milling slots.jpg
then drilled the chord for the clamp bolts once the rings are split.
drilling the chord.jpg
Straight all the way through with no wander.
drilled through.jpg
milled out the corners and enlarged the hole to 5mm
5mm drill.jpg
The finished rings before polishing with one 40mm wide side plate resting in the slot and a 5mm rod in the bolt hole.
finished rings.jpg
Now I have to cut the rings in half.

5mm drill.jpg drilled through.jpg drilling the chord.jpg finished rings.jpg milling slots.jpg
 

savarin

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#18
I thought I had it nailed.

I need 8 stainless knurled nuts for the clamp rings.
The first was ok, the second and third were very nice.
clamp nuts.jpg
The knurls are even and regular.
That's when I assumed I had solved all the variables. Bad assumption.
The fourth one started fine, the thread cut smoothly and all was going well until it came time to use the knurler.
It kept walking itself out of contact.
It just wouldn't stay at 90 degrees to the work piece and the tension on the central tightening bolt of the QCTP was as tight as I could get it.
Its a double or maybe a triple start, hardly any knurling in the centre.
The fifth one (still in the lathe ready to be parted off and thrown away) is what could only be politely called an abortion.
bad knurl.jpg
Its making me believe that a purpose built fixture that cannot swivel at all would be the way to go.
Anyone foresee a reason not to?

clamp nuts.jpg bad knurl.jpg
 

savarin

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#19
Split he scope clamp rings today.
I only had a hacksaw so to keep the blade straight I clamped two lengths of angle iron to them and sawed through the gap.
splitring1.jpg

This kept the cut pretty clean for a by hand saw cut.
splitring2.jpg

A quick rub on some wet and dry and a load of WD40 for approx 8 mins
splitring3.jpg

And the ends are nice and smooth and clean.
splitring4.jpg

splitring1.jpg splitring2.jpg splitring3.jpg splitring4.jpg
 

savarin

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#21
At last I can get back to scope work.
Now I have the 4 jaw chuck I can bore out the bearing shell.
There was just enough clearance between the end of the bracket and the lathe bed.
It was a hell of a job getting it centered, the slightest pressure on one jaw sent it way out of alignment


boring the brackets.jpg

Both brackets bored and the bearings turned up in delrin.
The 3x8 mm holes are for the cross pieces that the clamp bolts will fit once the slots for them are milled out.
Then they have to be split in half. I think I will use the two angle iron guides again for that.

brackets.jpg
These were shaped with a file and small flap disk.
I cant make up my mind whether to bore a large hole in each side plate or not. No function just for looks.
 

savarin

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#22
No holes at this time as I think I may need the sides of the supports for some future additions.
Milled out the slots for the clamp bolts.
milling slots2.jpg
The large round disk is the top clamp holding the bearing support onto the vertical milling attachment.
And then 4 holes drilled and tapped 5mm and split them with the trusty angle iron guides and hacksaw.
hacksaw guides.jpg
The clamp bolts are 5mm into 8mm stainless, the one with the double cross piece is so that when dismantled in the dark it wont drop and be lost.
bearing adjuster2.jpg
Like so. The nuts will be similar to the 8 knurled stainless ones that hold the rings together.
flipped clamps.jpg supports and cradle.jpg
and with the tube just for looks. You can just see where the bottom plate has a half circle cut out for the scope tube to recess into when pointing vertical.
supports cradle tube.jpg
I'm very pleasantly surprised at the smoothness of the bearings and how little pressure is required to change the friction/force required to move the scope. (so far)
I'm not looking forward to the huge amount of polishing to be done in the near future.
 

chips&more

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#23
Nicely done! And I especially like how you used the angle iron! That’s Yankee Ingenuity at its best!
 

rwm

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#25
That is looking sharp! What wall thickness is that tubing? I assume you are polishing that?
R
 

savarin

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#26
That is looking sharp! What wall thickness is that tubing? I assume you are polishing that?
R

Everything will be highly polished at the end, I'm not really looking forward to that job.
I also want to use some profile cutters on all the edges I can so it will look better than dead square sections.
The tube is only 3 mm thick.
 

Tony Wells

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#27
Going to do a reflector when you finish this project? I want to see how that's done. :)
 

savarin

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#28
Going to do a reflector when you finish this project? I want to see how that's done. :)
Hmmm Tony, then I guess you want to see how this one is going eh?
truss4.jpg
The truss tubes are 12mm square steel tube. They are made but I still have to weld the diagonals in.
I have the two lazy susan bearings for the top cages.
I have the glass for the two mirrors plus the grinding and polishing machine ready.
They will be two f6 12" mirrors where the back face will be ground to the same radius of curvature as the fronts.
They will be polished to a sphere then flexed to the parabolic shape required. I have made one 8" f3.7 spherical mirror flexed to a perfect mirror to check the process.
When I finish the refractor I will be starting on these again and will start a project blog.
 

rwm

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#29
Reflector binoculars?! Will you have the image inverted?
R
 

savarin

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#30
Reflector binoculars?! Will you have the image inverted?
R
Yes but they are for astronomy so it doesnt matter although it helps if the finder scope produces the image the right way up and the correct left to right orientation but its not essential.
 
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