Thursday, March 19, 2015

1/12 Scale Brass Telescope and Wood Tripod Mount

As a further addition to the Mission Style Den project I decided to see about creating a brass telescope and stand.

First was a source ot thin wall brass tubing.  I recalled the radio antennas are frequently chrome plated brass, and as I had a couple decided to try it.

Chucking a piece through the chuck on the lathe and spinning against 600 - 2000 grit paper took off the chrome plating and left a nice brass tube.

I turned a friction fit lens hood from brass stock.

I will add more photos showing the next step but the description follows.

I took apart a coule of cheap dead film cameras for lens material, and was pleased to discover that most are acrylic or clear plastic.  

Reversing the tubing in the chuck and filing 4 or 6 notches in the end made a core saw.  By mounting the donor lense in a small vise and centering the lens with the tubing end using the mill tower enabled me to core out a slip fit lens in the tubing.

A rather convincing telescope end!

 Tomorrow will see the other end plug turned and drilled for the eyepiece tubes which will hopefully be a couple more smaller pieces of the brass tubing with the smooth nesting lengthening and collapsing.

Stay tuned,

Thursday Mar 19 update..

Eyepiece end plug drilled and turned.

Nested smaller antenna pieces sanded and polished to brass.

Nested eyepiece tubes slip fit into end plug.  Note flared end of larger tube to stop at full extension.


Drilling for eyepiece.

Partng off eyepiece.

A dot of gel superglue as a rear lens.

Front lens.

Completed with eyepiece collapsed.

Complete with eyepiece eyepiece extended.

I have decided to do the tripod legs in ebony for contrast and strength, with brass hardware.

23 Mar update - 

Yesterday I had a gremlin steal one of the telescope base pieces  before i could take a pic.  I redid it.

First was the channel in a piece of what turned out to be bronze to fit the telescope tube.

Next the hole for the elevation pin drilled and large pieces of waste parted off to leave the tab.

The sides of the tab milled and tab profiled.

The base may still be a little too thick, but will work as is.

The next step I am going to not show the way I got there, only the poor result.  I tackled the upper part of the swivel base that the tab on the telescope mount goes into.  It came out off center and too thin on the tabs and broke..

I went back to the lathe, turned the blank down and drilled the center hole and larger recess for the swivel bolt head.  I mounted it onto the drill press and cut the center slot with a slitting saw.

Cheeks are milled flat and pin location verified, then the profile was turned and the upper part (minus the bolts which have yet to be made) is complete.

Next I took the task of the lower part of the base whih this upper part will swivel on, and which the leg pairs will attach to.  The task requires three equally spaced tabs for the leg mounts,  and a flat for the upper part to rotate on.

It was a test of the indexing jig Bill Robertson made for this lathe and it's milling tower attachment.  I first drilled the brass for the center pin, then turned a 1/4 inch diameter stub on the back side of the blank to fit into the indexing jig.  The jig has 24 equally spaced holes, so rotating it 8 holes between milling will give the required profile..

Once that was done I moved the milling tower with the milled blank still in place to the drill press and was pleasantly surprised to find that it would mount to the X/Y table!.  I milled the edges of the previous milling flat and parallel for the leg mounts, then drilled 1mm mounting holes through the tabs.

That done the blank moved  back to the lathe and parted off.  I turned the center pin for the swivel and slipped both upper and lower base parts on for fit.

I was a able to locate my miniature die thread plate, but the gremlins seem to have poofed the accompanying taps...

While I await a new set to arrive I will start on the leg pieces which will be ebony, with brass heads to mount on the base tabs.

Maybe tomorrow...

25 Mar update.

Cut the ebony which was sent to me by Mr. Wayne Henderson for the leg assemblies.

Cut leg pieces to length and profiled them.

Cut and fit the brass surrounds.

Turned the tops to fit the sockets in the brass mounting tips.

Fabricated the tips by boring sockets in brass rod, milling a cheek and drilling the mounting hole, then turning the end.  The middle series of pix did not get taken...   sorry.

Leg assembly temporarily mounted to the base for fit.

Except for whatever I decide to do for the feet, and either a through pin or thumbscrew at the brass sleeve, the leg assemblies are completed.

26 Mar update.

I cut and mounted some internal brackets which serve two purposes in a full size stand.  First they offer inner support to the lower leg top if it is retracted, and second offers a mounting place for the inner tray.  I think for ballast I will make the tray out of the same bronze I cut the upper swivel mount from, and mill a tray recess in it, adding some holes for eyepieces.

I went back and redid the leg brace bands.  I think it gives better definition, and would increase the stability.  I also wasted a chunk of bronze, and a chunk of ebony attempting to mill out the triangular tray support.  I am in the middle of the third iteration and will post when done.

28 Mar Update

The third tray attempt.  Ebony bottom with brass angle sides, a wire frame beneath ending in hooks over the upper brass pieces.

Still need - nuts and bolts, feet, and thumbscrews.   SOOOoooo   close!

29 Mar update.

Thumbscrews turned, filed, polished and in!

After a couple of days making nuts and bolts it was ready to reassemble in final form.  First however I wanted to replace the front lens  due to it having chips on the edges that were visible.  They came from burs on the core tool I made, so I cleaned the tool up, clamped another donor lens in the vise on the mill attachment and using cutting fluid cored a better lens.

And finally, using a couple of tiny screws from one of the cameras I mounted the telescope to the base and I deem the project complete!

Thanks for all the comments and complements.  I think this will be entered on it's own merit for the fair and not placed in the Mission Den as planned.

Onward to the next project!  I still have books to complete and some decorative stuff for the den.