The Giant Binocular

[savarin]

I rounded the ends at 500rpm with the 12mm end mill. Thanks to Bob Korves for suggesting the speed.
Virtually a hot knife through butter.



all 6 done with the handle I used as an aid.



To weld them to the base I clamped a length of steel to the legs as guide to keep the angles correct according to the mark 1 eyecrometer.
then clamped the foot to the upright with a large worm drive clamp.



Checking the opposite side with the two strips to ensure they were centred they were tacked in place then the foot removed so they could be welded in place.



The main tube now slides onto the feet and will eventually be bolted to the verticals.



So far its a very stable base.
And here is a teaser.



Somewhere between the two ends of the second level is where it hopefully will pivot so approximately a quarter of that tube will be cut off.

 

[Bob Korves]

I rounded the ends at 500rpm with the 12mm end mill. Thanks to Bob Korves for suggesting the speed.

An easy way to do surface speeds in your head is to use the surface speed you want times 4, divided by the cutter diameter. 70-100 SFPM for mild steel, 1/2" cutter. I used 80 SFPM, times 4 equals 320, divided by 1/2 equals 640, rounded down to 500 to start with, or whatever the closest machine speed is. It is that easy, no calculator or even a pencil needed. This is not rocket science...

 

[savarin]

I will try to remember Bob, thanks.

 

[brino]

This is not rocket science...

Even though that base currently looks like some kinda launch pad.....or grenade/mortar canon.....
-brino

 

[savarin]

I've now screwed the pier tube to the welded base and I think I may have gone a teensie weensie bit over the top with 15 x 5mm screws holding it on.
Mind you, there aint no way no how its gunna come loose

Unfortunately that is instant rust. We've just had 80+ % humidity for the last 2 weeks.
(The rain was very very welcome though)

 

[Eddyde]

Wow, looks real solid, Nice build!

 

[savarin]

Almost finished welding in the diagonals for the first truss when just as I was going to start the last cross brace the wire ran out.
Typical for a sunday and I was on a roll it was going so well.


That left a fair bit of time before the day ended so I marked out 40 third circles in 3mm strip and drilled all 40x6mm holes.
These will be cut along the diagonal line to produce 40 segments that will end up as brackets welded into the corners of the hexagons to use as fixing/locating brackets. 40of these is nearly 1.5 meters long which is why the photo only shows 10.

I will bolt 6 (or more) together aligned as best as possible along one flat edge then drill a pilot hole roughly in the middle (already centre popped)
use the 6mm bolt to clamp in the chuck with a smaller bolt as a dog to prevent them spinning and turn the outside curve.
I then hope to be able to clamp them to my vertical slide and mill off each straight edge to to even them up opening the 6mm hole so it will clear the weld in the corner of the hexagons. At least thats the plan.
I have a sneaky suspicion that if I had really thought of mow many repiticious parts to make there would be I may have changed the design to solid tubes instead.

 

[savarin]

One side truss with all the diagonals welded in. Now has to have the welds sanded smooth then the third circle brackets welded into all the corners.


After I cut 12 of the patterns out for the third circle brackets I bolted them together set them up to turn smooth


It was a bit scary due to the off centre mass but worked well to my surprise.


then I set them up in the vertical slide to face the two straight edges


Rather pleased with the result as I was really not sure if it would work.
I love it when a plan comes together.


I've started welding the diagonals into the second set of trusses.
Slow but sure I hope.

 

[savarin]

All the diagonals are now welded in.
Got the third circles cut to size, all 36 of them.


6 taper pins made and welded in, the top part just drops in and aligns perfectly (yeah I know nothings perfect but its good enough for me)
Each tube has 3 of these for alignment

The other three corners have captive (so I dont loose them in the dark) screws to hold both tubes together.


The actual screw is held inside the housing with the spring so when the top tube is set on the ground nothing can damage the thread.
Just push down on the knurled part and screw up tight.

These will be screwed from underneath into the housing with 3mm screws but I havnt drilled and tapped the holes yet.
Only 5 more of these to make. This one is version 5, None of the other designs worked as I wanted them to.

 

[savarin]

The captive bolts in place.
Not as simple as it looked as some of the welds were too large and there was no room to fix the base to the bracket.


so I thought I was being clever by making a special cutter to remove some of the weld to make room.
a short length of 19mm rod with a 5mm hole drilled through it at a long diagonal. (the blue allan key is passing through the hole)The cutter is a sharpened chunk of broken 5mm tap held in place by the short screw.


The plain length of this screw is 5mm dia to fit in the hole in the bracket.
The long length is so it can be turned with an electric drill from the top of the truss.

I used a clamp on the top of the truss to hold the long shaft vertical


Pride cometh before a fall.
It didnt work, the bit just wore away without cutting anything from the weld.
I had to resort to a carbide burr to slowly wear the excess weld away. This worked.
I may try again with a solid carbide bit just to see if it would work.