Metalwork

The notes herein are taken from the working documentation that Barry Armstead sent me, they appear chronologically and unaltered. The notes were never written to form a story, however when read from start to finish, the most magnificent story emerges.

Thursday 26th of July 2007

Ron Ziemiecki handed me the telescope on Saturday the 14th of July 2007. I brought it home to my private workshop in Canberra. As more parts arrive, I am photographing all in the state received, taking special note of any embossed inscriptions.

The large upper section of the main telescope consists of two wooden rings set apart and held by a metal tube. The wood is in semi rotted, but dry condition with a lot of large cracks and splits visible. I have yet to identify the type of wood. Section outer casing appears to be roll-formed sheet metal with two parallel depressed grooves running the circumference and rolled at the ends. There is some rust showing at these ends. The outer casing is rolled and joined with a folded crimp. There are a few holes in the casing that appear to be mounting holes for something. Also protruding from the outside are _?_number? Hexagonal-head-with-flange fasteners. They are holding two out of three wooden plywood blocks inside the tube that position the spider vanes. Block three, if there was one, is missing.

All of this is blackened on the outside with paint and on the inside with as yet unidentified substance. (Possibly tar or pitch?) Also protruding from this top section is the brass focusing tube. It fits through a shaped hole in the main tube and is held in place by four fine threaded screws. Someone has attempted a previous fix or modification here in the fixing of the focus tube. A large, flat fibreglass ring has been fabricated, that fits on the inside of the main top section, over the shaped hole for the focus tube. The four screws screw in from the inside, through the fibreglass ring, and into the brass of the focus tube.

The focus tube itself is moderately corroded, but no pitting is apparent. At first glance, this unit seems to be one piece solid turned brass. Upon further inspection, there is a hole in the side with a straight rack of teeth inside. Around this hole are four equal-distant holes. This looks to be where the focusing knob attached. Upon grasping the top straight knurled grip rim of the tube and pulling upwards, the tube telescopes out. A further pull and the top section comes out, revealing two inner sleeves. The top one comes out with the grip ring. It is a very thin brass tube, with cut-outs in the side, which give it a spring-fit. The next sleeve has to be pulled out from the bottom end of the main focus unit. This inner sleeve is also quite thin, but has the straight rack of teeth molded onto it lengthwise. These teeth are in ok condition except for five of them located about one third of the length of the rack.

The Secondary mirror and spider vane unit is in bad condition. The angled mirror is in dire need of re-aluminising. The mirror is held angled inside a metal cylinder, open at the bottom end and a right angle hole in the side to allow the light path. The top end of the apparatus has a plate with screws and a shaft in the centre that supports the vanes. This appears to be held in place inside the cylinder with small grub screws. One of these screws on the side is badly rusted, and sits amidst a very large and forked stress fracture, which runs almost halfway down the body. There is an adjustment screw (collimating) also fitted into the top plate. The two vanes are badly rusted with the ends almost completely missing. One end that remains slightly intact shows two small holes used to fix the spider to the inside plywood blocks of the main telescope’s top section. The whole unit is painted matt black.

There is a large metal band that I am uncertain as yet where it goes. It is smaller in diameter than the top section of the OTA. It has a rolled end and a straight end. It also has a few drilled holes and a slot cut in the flat end. It appears to be made of brass and is also painted black.

The finder scope is interesting. Made of brass, the eyepiece end is threaded on the outside. The objective end is threaded on the inside. A threaded ring is screwed into this. The ring has three pairs of tiny slotted brass screws positioned in an equilateral triangle fashion. These anchor the wire crosshairs that are suspended across the central objective hole. Where the wires cross they form a triangle in the centre. The wires are old and bent. This top ring is painted black. Along the outside body of the finderscope are two brass mounting bands, one at each end. The objective end band has two fine groves at either end of the band, and a deep groove in its centre. The eyepiece end band just has the two fine grooves. Both bands show evidence of the previous owners mounting screw marks and locations. Some of these are quite deep.

Also near the eyepiece end band, toward the centre of the main tube and on opposing sides, are two long sunken grooves, running parallel with the tube.

What I am assuming could only be the base and mounting plate for the primary mirror is quite heavy. It consists of a round plate of wood with a cast iron plate mounted on one side. The iron plate is quite smooth and painted black. It has a central sunken circle. The other side of the wooden base plate shows a number of fasteners and holes. There are ten spaces occupied around the circumference, alternating between bolts with hex nuts and some sort of metal hollow inserts. There are three flat drive button heads in an equilateral triangle around the centre and one bolt with hex nut right in the middle of them and the plate. The wood on the opposite side to the metal plate is painted black and is showing signs of age with cracks, chipped paint and splits in the wood.

There is a brass oval shaped and curved plate that mounts to the side of the OTA somewhere. It is a brass cast plate with John Browning London embossed on it and a raised rim. Either side of the centre are two counter-bored holes for mounting screws.

Restoration. Cleaning and polishing.

Brass components: Disassembled, cleaned and polished using a soft cotton buffing wheel on a bench grinder. Purpose brass buffing compound. Finished off by hand with polish and soft cloth. To see images of this section click here.

Saturday 28th of July 2007

I found out that the large brass rolled band actually fits over the cast base plate for the primary mirror. The fit is perfectly snug and aligns over a locating lug on the base plate via a slot cut in the brass ring.

The spider and secondary mirror assembly is a complicated little unit and has many components. There are two fine-slotted brass set-screws in the top plate directly below the spider vanes and a long, double-knobbed screw with straight-ribbed grip edges on each. Upon further inspection of this long screw, it was revealed that it is actually a two-part screw, with a central threaded shaft that slides in and out of the outer shaft. Once the three were undone, the top plate and spider vanes came away from the mirror housing to reveal another plate underneath where a spider had made its egg sac.

The spider vanes are held to the top plate via a smooth but solid turned bar that goes through the central brass cylinder in the middle of the spider vanes. This bar is stepped inside to a smaller diameter and then has a tapped hole in the end of it. The top plate has a short tapped thread brazed in its centre that the bar screws onto. It appears the very rusty steel vanes are held onto the brass cylinder with some sort of cordage thronging, which has been coated in a clear resin. This cementing looks too modern to be authentic and looks to be a temporary fix for a missing vane.

In the centre of the next plate on top of the secondary mirror assembly, there is a brass slotted and countersunk head set screw. Around the top edges of the unit are three very tiny screws that secure the plate into the top of the (very badly cracked) outer casing. Once all these screws were removed, the top plate came out, revealing a snug fitting wooden cylindrical block inside. The wooden block slides out and has one end flat with the opposite end steeply sloped. This is the main supporting block for the angled secondary mirror, which slid out after it. The glass mirror is intact, with very badly corroded silver coating on one side to the point where you can see through the forty percent of the glass. On the back side is a black and silver sticker that looks out of it’s time. The black numbers on the silver sticker are 5594.

On the inside of the brass outer casing, is a raised angled seating ring to set the secondary mirror against. With everything removed from the brass outer casing, the extent of the corrosion and cracking is apparent. It will need to be filled with braze and then re-worked to bring it back up to speed.

All of these brass components polished up beautifully with the exception of the secondary casing. The tube is too cracked, thin and delicate to attempt with a bench buffer. Even once the cracking is repaired this will have to be polished by hand to avoid any further damage. To see images of this section click here.

Saturday 27th of October 2007

Today I took the steel sheet metal to Vincenc and Bridgeford’s workshop in Queanbeyan. Tony Vincenc there was very generous to offer his assistance, allowing me to use his workshop and the valuable time of one of his top fabricators, Paul Brough.

On arrival, Paul and I unloaded the steel and placed it in the workshop. Paul’s experience was invaluable as he very quickly worked out how much steel we needed to cut off, to make the finished product more accurate.

First, we cut the sheet to size on the guillotine and then carried the full length sheet over to a very large manual roller. From the look of it, it may have been very similar to the ones used back when the telescope was first manufactured in the late 1800’s.

Paul used a rubber mallet along the length of the sheet metal first to give the rollers a start. *The steel proved to be VERY soft! It was sourced by Dennis deGruchy at One Steel in Hume. We then flipped the sheet over and commenced fine adjustments of the rollers. Once the steel was feeding in evenly, Paul gave me directions as to how far to wind the adjusting rollers with each time through. Gradually, the sheet started to bend. A bit more on his end at first, but as I corrected my end, the curve became more even with each pass.

Eventually, the edges met and we gave it a couple more fine-tune rolls, to ensure an even radius. Paul made sure that he gave me enough overlap for adjusting size and allowing for castellation.

Now to take it home and let the fun begin! To see images of this section click here.

*The sheet steel was sourced by Dennis deGruchy at One Steel in Hume. Dennis was most helpful and proved to be quite resourceful when it came to finding a metal that would compare to what was available over one hundred years ago.

My special thanks go to Tony Vincenc and Paul Brough at Vincenc and Bridgeford in Queanbeyan.

Sunday 28th of October 2007

Having never attempted this before, I thought I would try it on an off-cut of the same material used for the OTA.

I cut 2 pieces of mild steel sheet metal about 10 inches long. (Figure 1). Using some manual nibblers, (Figure 2), I cut a series of matching slots about a ½ inch long, along the edges to be joined. (Figures 3, 4 & 5).

Using the edge of the bench, I lined up the slot cuts and used a ball peen hammer to bend every second castellation down. (Figure7) I then flipped the steel over and did the same for every other one.

Doing the opposite side to match up, I then slotted the two halves together. I quick tap or two on the edges made for a snug fit. (Figure 8)

Using a large piece of pipe in the vice as an anvil, I proceeded to use the ball peen on cold metal to hammer the castellation’s, (Figure 9), thereupon spreading the steel out to fill the gaps and tighten the joint. With a bit of work this turned out quite simple to do. With heat added this may be even easier. The metal in this case is pretty soft so it didn’t present a problem. (Figure 10)

I noticed that whilst I was hammering, the sheets naturally wanted to come apart. I will stop this from happening when I castellated the tube by tying wire around the tube to stop it from spreading apart. For the images for the trial castellation click here!

Wednesday 14th of November 2007

Today, one of the workshop guys where I work, kindly gave me a couple of large blocks of solid brass that he had sitting in the bottom of his toolbox for quite some time. I sketched the rough shape (oversize of course) onto a block. Using a metal cutting blade on a bandsaw, I roughed cut the bulk of the brass in a basic spider shape. After that, I refined the measurements by consulting photographs, scaling from them and drawing a paper template with instruments. The spider's extremities are roughly the same size as the top of the secondary collimation plate. Over the next week, I will carve the block to its final shape and size, drill out the centre, then polish it.

Thursday 15th of November 2007

To finish the central brass block that suspends the secondary mirror assembly, I cut a 3 prong template out of paper and glued it to the face of the rough-cut, 24mm thick block. Using the bench linisher, I carved the block down to size, shape and a nice finish.

Next I centre punched the middle of the block and drilled a 4.5mm pilot hole, all the way through, which allows the centre threaded rod on the collimating plate to slide through. I then counter-bored a 9.3mm hole approximately half way through the block, so the main bolt could submerge deep enough to reach the collimating plate thread.

A 2.5mm hole at was drilled at the end of each prong and then slots cut from the ends to meet these. This will accommodate the folded over ends of the vanes to provide a slide-in, secure fit.

To test the mechanics of this, I cut a small strip of mild steel 1.6mm sheetmetal and folded over the very end with an engineers hammer. Again, I used the linisher to tidy this up a bit and test fit it in the slots. The same will be done at the other end of each vane where small nuts with similar slots in them will eventually poke through the OTA, pulling tight with brass knobs from the outside. To see images of this section click here.

Saturday 17th of November 2007

I cut 3 vanes, 24mm wide out of the same sheet metal used for the OTA. To start the fold on the end, I placed about 3mm into the vice and tightened it. A quick check with a square and I bent them all over with a hammer to 90 degrees. The fold was continued out of the vice on an anvil where the fold was bent all the way over and flattened to twice the thickness of the parent sheet. Shaping and finishing was done on a linishing belt.

I have deliberately made the vanes too long. When the OTA is finally castellated, I will then cut them to length and shape them the same way.

Using a tungsten carbide tipped set of dividers, I scribed a line along both edges at 1/2 inch. I then marked out 2 inch increments with pencil along the scribed line. Castellation slots were cut using a pair of manual nibblers. Care had to be taken that the ends of the tube were matched and clamped so that the slots would match all the way along.

Once all the slots were cut both sides, I had to make a purpose built tool to fold the castellations evenly without distorting the tube too much. I used two pieces of 1/4 x 2 inch mild steel flat bar and screwed them together with self drilling metal screws. A quick touch up on the grinder ensured an even face on both of them with no sharp edges.

The theory worked out well, as the tool fit perfectly over and under each castellating tab, to bend it up with little effort and nice and even.

The two edges fit nicely together. Next move is to take it to work, slide it over a big pipe as an anvil, strap the tube with steel strap to hold it's shape, then heat and beat the castellations. To see images of this section click here.

Monday 19th of November 2007

Today I took the rolled tube into work. My employers at Dorma Movable Walls were kind enough to permit me to use the workshop for this phase of restoration.

I used a large galvanised pipe as an anvil as it had a thick wall and could take quite a beating with no effect on it. Balancing each end of the pipe on two workbenches, allowed freedom of movement once the rolled tube was positioned over it.

I used a couple of pieces of 19mm steel strapping to pull the castellations together and keep them there for the process. Using an oxygen-acetylene blowtorch, I heated the castellations up to a nice straw colour and commenced hammering with the new planishing hammer purchased for the job. The metal was slightly softer with the heat, than when I practiced on the cold piece of scrap a few weeks ago.

Trying to keep the heat even, I worked about six to eight inches at a time, gradually moving along the length of the tube. Unfortunately, the tube still warped and I was unable to avoid the warping that seemed to occur full length of the castellations, that actually formed an even shallow concave channel. My thinking now is to take the castellated tube back to Tony Vincenc's workshop and just roll that bit out to make it even again.

Other than that, the castellated joint was a huge success. It was good to practice and learn this very old technique, that probably hasn't been used in quite a long time since the introduction of welding and other methods. To see images of this section click here.

Saturday 15th December 2007

Last week, I took the tube back to the roller again in an attempt to roll out the ridge distortion. I had a feeling the castellation’s were still too square and that they would let go in the roller. Sure enough they did.

So, it was back to the drawing board. Actually, it was back to the anvil. As the pipe I used as an anvil last time seemed to bounce marginally, I found a solid steel bar anvil in a local metal yard and used that this time.

With a much more solid anvil to work with, the hammer bounced less hence the metal was working better. The midday heat from the sun soaked into the steel and that seemed to make it softer too. The problem was, the castellation tool I used (nibblers) cut slots that ended up too wide. So then to work the steel enough to spread and fill that gap required a lot more effort. Each castellation required 100 to 200 hits with a two pound hammer to spread it enough. My elbows are killing me!

This also presented another problem. Too many hits on the steel result in metal fatigue and the steel started to crack. All I could do was try not to hit the same place too often. The metal did, however, start to spread as I developed a technique.

The constant hammering along the line also caused the tube to warp and distort, forming a concave channel full length of the tube again as it did last time. Rather than put it through the roller again and risk breaking the castellation, I used a hard plastic dead-blow hammer to strike along the length of both ridges. This slowly pulled out the channel and gave the tube back it's symmetry. I'm glad they don’t do it like this anymore! Three hours in the baking sun (I couldn’t move the anvil, too heavy.) and I only got one third of the tube done. It looks like another six hours to complete the castellation, then dressing off. To see images of this section click here.

Sunday 2nd March 2008

ALT swivel bracket.

Underneath the OTA is a brass joint that the altitude adjustment bar swivels from. This part is missing altogether so it needed to be built from scratch. This seemed to be something that I could build by hand, without the need for a mill.

I started with a raw brass block and marked out a rough pencil outline on one smooth face, based on ratios measured from the photos of similar telescopes.

Using first a cutting disk and then a linisher, I cut the rough shape out then ground it to size. To cut the slot down the centre, a series of cuts were made, then the waste was chiseled and filed to size and smoothed.

Finishing touches were done using a scraper on all the edges, then a combination of fine filing and wet and dry glass paper.

I drilled two small holes in the base and countersunk them slightly to remove the sharp edges.

Final finishing was done on a high speed buffer using brass buffing compound. I have deliberately left the holes on the sides for the swivel pin for later, once we have ascertained the size of the pin to be used. To see images of this section click here.

Tuesday 11th March 2008

Today I used a lathe to turn up some items using measurements from the old photographs.

The Bolt that goes through the ALT top bracket, with a flat thumb grip on one end was lathed down to size first, then filed flat on the end whilst still in the chuck. Later, the end of the shaft on this will be threaded to 3/8 of an inch.

The ALT head was turned to diameter and length, parted off,, then drilled with an 8mm drill bit to allow for tapping to 3/8 inch later. I then squared this up sideways in the chuck and used the lathe to mill off the sides flat. This was measured to 15mm, to fit inside the slot of the ALT bracket.

The pin with the flattened and drilled end, that goes in the end of the AZ adjustment slide tube, is made much the same way as the bolt that goes through the ALT bracket. Click here to see images.

Wednesday 12th March 2008

Today I used a milling machine to flatten the ends of the Azimuth slider tube brass end piece. The final thickness was 6mm.

A close friend of mine did me the favour of using his mill and lathe to complete and fine tune the Altitude top bracket assembly, using the parts I had roughed out by hand.

After much more ratio study on the old photographs, I came up with some measurements for the azimuth post and spacers. These were all lathed out of brass bar stock. For ease and availability of tooling, I have used a 5mm metric thread for the top retainer of the post, rather than trying to guess an imperial thread. Click here to see images.

Thursday 13th March 2008

Today was spent finishing off and polishing the Altitude and Azimuth bits and pieces. First, the top thumb screw for the azimuth post was threaded using a die size M5.

Next, the corresponding hole in the top of the post was tapped using an M5 tap.

Finally, the end piece for the azimuth slide tube was drilled to 10mm and given its finished shape on the linisher. I then fitted it into the end of the slide tube itself. Turned size was just right for a good tight fit. If there is any movement in this piece in time, I think a hole will need to be drilled through the lot, and a retaining pin installed.

All brass was polished on bench grinder fitted with a buffing wheel using brass polish compound. Click here to see images.

Tuesday 18th March 2008

I didn't have much time today due to other projects and the fact that I am waiting on other parts to continue the work. I did, however, manage to drill out and file to shape, the retaining spacer that fits on the square drive underneath the azimuth assembly.

This was done with a needle file, taking out a little bit at a time by eye, until it fit neatly over the square drive.

In the centre of the square drive, there was a threaded hole that seemed very clagged up with impurities. I ran a 15/16 tap through it to clean it up and it screws in nicely again. Click here to see images.

Saturday 17th May 2008

Time to start putting things together. To start, the OTA was measured out to six feet, cutting off the worst of the buckled ends from the castellation process. The ends were then filed straight and smooth, then finished with emery paper.

Next, the hole for the focus tube was measured out to 5' 62, 3/8", taking into account the inset for the primary mirror housing later. The measurement is from surface of primary to centre surface of secondary mirror. This measurement was ascertained from a previous exercise with the focal length testing rig.

The hole was marked out by tracing placing the focus tube over it's marked position and traced inside with a scribe. It was then a matter of using a series of drilled holes (stitch drilling) to cut the circle out and file smooth.

To mark the positions for the focus tube screw holes, a paper template was used to trace the positions from the overturned focus tube, then transferred to the OTA and drilled. Next the Focus tube was simply screwed on from the inside.

To fit the spider, three holes were marked , centre punched and pilot drilled in the OTA, then bored out with a larger drill. Last, the round holes were squared out with a small square file to fit the brass vane fittings.

Last thing for today was to fit the altitude adjustment bracket to the bottom of the tube (the castellated side) This was a simple matter of drilling two holes through the bracket and into the tube, then placing through a socket head cap screw with spring washer and nut on the inside of the OTA.

For now all I had available was socket head cap screws. I will replace these with brass cheese head screws as they become available, as per the original telescope. Click here to see images.

Thursday 22nd May 2008

I was given some thick steel plate today, so I got really excited about making the altitude adjustment hand wheel. I even got as far as drawing and planning it all up nice with scaled measurements from old photographs.

Upon arriving at the lathe with all the associated parts, I realised (with help) that there was a better way to do it and so decided to move onto a simpler, but no less important part that I could do immediately.

This part is the brass centering and locating sleeve that fits inside the altitude adjustment tube. Once this part is made, the hand wheel fits on the end of the sleeve, allowing it to spin within the tube and screw the brass threaded rod up and down for fine altitude adjustment.

I used an offcut from brass bar stock and turned it down to 16.7mm to fit inside the tube. I left a 6mm flange at the top, 31.8mm wide. This will match the raised edge under the hand wheel.

The length of the sleeve is not important as it is not seen, but I made it about 50mm long.

In order for the 3/8 inch brass threaded rod to slide through evenly, a through hole was first centre drilled and then bored out to 9.6mm.

The Rod was then fitted through the sleeve, and the sleeve and rod fitted into the end of the tube. The sleeve should provide a snug fit, that still rotates smoothly when attached to the hand wheel. The effect of brass on steel is commonly used for bushes like this as the two metals slip over each other well with little wear. Click here to see images.

Friday 23rd May 2008

Today I went back to more brass, shaping the parts for the handles on the OTA and the two Keepers that lock down the telescope's pivot points. I also polished up the spider support that I made a few months ago.

I used the measurements ratioed from photographs of the pivot points and marked out the pieces on the surface of the raw brass. I then cut away all the bulk excess brass, close to the marked lines.

To Shape, I used a linishing belt on a bench grinder, followed by some hand filing and sanding with wet and dry emery paper.

Finally a good hour spent on the buffing wheel cleaned up the surfaces ready for hand polishing at a later date. Click here to see images.

Saturday 24th May 2008

A big day on the scope today. Dawn to well after dark.

First, a visit to the metal suppliers for some brass and special screws. Then a visit to my uncle's to use his lathe and turn down the handles. I used half inch brass rod and simply turned down the ends to fit into the brackets to be built later on today.

The hand wheel was completed by my uncle early, so it was a nice surprise to get that back today. Wow! He's done a beautiful job of it too.

Once I got home to my own workshop, I continued to work on the handle brackets and keepers for the OTA pivots.

I used the linisher to shape the brackets, then drilled and counterbored them to fit their mounting screws. As the cheese head screws are hard to come by, I bought some hex head bolts, ground the corners off them to make them round, then hacksawed a slot in the tops of them.

The brackets were counterbored to fit the ends of the 1/2 inch rod turned down earlier, then press fitted on tight. Once aligned, the handle complete was placed on the OTA in the appropriate position, the holes marked and drilled, then the cheese head bolts fitted. Inside the OTA, the protruding bolts were secured with a spring washer and nut.

The plaque was fitted to the OTA in much the same way, except countersunk brass screws were used.

To top the evening off, I decided that the access hatch in the green scope photographs we have been using as reference from time to time, was a good idea on this particularly large telescope. The hatch allows access to the primary mirror for cleaning, maintainence and retrieval of any objects dropped inside without disturbing collimation of the primary cell.

On the OTA, I marked a 12 inch centre line, starting a couple of inches up from the bottom. I used a four inch radius and dividers to mark the curve at each end, forming an 8 inch wide oblong. This was then cut roughly with a cut-off disk on a small angle grinder, then tidied up with a grinding disk, hand file and emery paper.

To make the cover plate, I used the kept offcut from the end of the OTA a week or so ago. To cover the hole, I simply added an inch all round then cut and shaped it in the same fashion as the hole. Click here to see images.

Tuesday 27th May 2008

I found a couple of 20mm thick mild steel plates and thought these would be great for the two mounts for the finderscope.

Using the outside diameter of the finderscope mount flanges, I marked a circle that allows about 1/4 inch clearance all around the finder. I allowed for a nice thick ring around the finder and marked it all out using the end cap of the finder as a template for the tight curves.

The shape was roughed out with a 1mm cut-off disk on an angle grinder, shaped with a grinding disk and then smoothed with the bench linisher. Boy this stuff gets hot. It took about 3 hours to get this shaped after cutting.

The curve on the bottom was radiused at 5, 1/2 inches as per the OTA. Click here to see images.

Thursday 29th May 2008

Today I got a little bit of work done during my lunch break and attempted to cut out the inner circles of the finderscope mounts with a 57mm holesaw. By the time I had found everything I needed and start cutting, I had run out of time. Never mind, I know where everything is now so tomorrow lunch I should get a lot more done.

Tonight, when I got home, I thought I could get some of the hard work done, knowing that to cut the square holes it was going to take a lot of sweat and elbow grease.

I scratched the shape of the hole to be cut onto the metal with a tungsten scriber, then proceeded to cut away the bulk of the metal by stitch drilling with a 10mm drill bit. Three holes took out the bulk and I finished where I could with a 4mm drill bit. This gave me enough gap to pass a hacksaw blade through and then attach the hacksaw to start cutting. Once the rough hole was sawed through big enough to get a file through, I roughed it out even more with a flat bastard-cut file.

When the bulk of the metal was nearly down to my scratch marks, I used a combination of triangular, bastard and half round files to finish shaping the hole. To smooth off I used a fine second-cut file using a draw-file technique. I will sand, linish and polish once the shaping and drilling is completely finished. Click here to see images.

Friday 30 May 2008

Using the 57mm holesaw, I finished cutting out the centre of the finderscope rings. I spent the next 3 hours filing, grinding, linishing and polishing into shape.

Next step is to drill and tap the three holes for the finderscope adjustment screws and the two countersunk holes to fasten the mounts to the OTA. Click here to see images.

Saturday 31st May 2008

A big day on the scope today. I finished a few final shaping touch ups on the finderscope rings with a number of hand files. Next I marked three holes on the outside, 120 degrees apart for the full 360 circle. Once drilled and tapped (M6) These will hold the three brass adjustment screws for the finderscope. Two holes were also drilled and countersunk at the base of the two mounts and into the OTA in their respective locations adjacent the focus tube.

Today I also got back the completed secondary housing assembly. The original peices were so badly made and worn, that a complete rebuild was the only way. At least there will be spare parts huh? Along with it, the holders for the spider vanes that poke through the top of the OTA were returned, tapered at the points to reduce light obstruction.

It was also the big day for painting. In preparation the entire tube was hand sanded inside and out to remove any light rust and scale. As this is low carbon mild steel, the slightest bit of moisture, even a palm print, will rust. There were two large dents in the OTA that needed to be addressed. Using a specially designed "Knockometer", (engineers hammer wrapped in rag) The dents were first raised from the inside, then the high points planished until the dents popped out.

I wiped the whole tube down with a rag to remove dust then placed a heater in the end of the tube to heat up the metal, ready for painting. Here in Canberra, the temperatures do not always favor painting. I taped up my sleeves to stop them from dragging inside the tube and painted the inside with a paintbrush, using Killrust matt black paint. Once done, I painted the outside with Killrust gloss black. I also painted the finderscope mounts, as they are bare steel and will eventually rust. Click here to see images.

Sunday 01st June 2008

After letting the first coat dry for a minimum of 16 hours, I gave the OTA a rub down with 180 grit, wet and dry emery paper. Following that, it was just a matter of giving it a carefully brushed second coat. A time consuming job, but pretty simple really. I did have quite a job on my hands prepping the area to keep the dust down while the paint was still wet. Click here to see images.

Wednesday 4th June 2008

For starters tonight, I linished the stepped milling marks out of the bottom curves under the main scope pivots. To ensure that the two pivots could be positioned exactly opposite each other on the OTA, I employed a little trick handed down to me by my uncle. Using a long strip of paper, I wrapped it around the OTA. Pulling it tight and even all the way around, I marked and cut the strip where the two ends met. Next, I removed the strip of paper then folded it carefully exactly in half, then in half again. I then wrapped the paper strip back around the OTA, and used the fold lines to mark the positions for the holes to be drilled. Easy! I kept this strip of paper to obtain the exact circumference down to the millimetre for planning purposes later.

Next, I centre punched and pilot drilled the two holes, then proceeded to drill them out with bigger drill bits. As my 1/2 inch drill bit does not have a reduced shank small enough to fit in my hand power drill, I had my sone help me carefully hold the whole OTA under the drill press instead. Job done.

Then it was a simple matter of pushing the bolt and washers through from the inside. (thank God for the idea to put in an access hatch or I would never have reached.) I positioned the brass pivots over the holes on the outside and screwed through the bolts, tightening with a socket and ratchet.

Once this was done, I had a bit more of a look at some of the old ink drawings of browning telescopes. A lot of the ones with access hatches seem to have some sort of hinges on the top side. From some unclear drawings, I came up with a simple offset pin hinge design. I hacksaw cut four pieces of brass plate and two steel 1/4 inch cotter pins. Using the bench linisher, I ground them all smoothe and equal size. This gave me a reference edge to measure, mark and drill the 6mm bores for the pins. I set and locked the bench drill so that the bit would be limited to a certain depth. I didn't want to accidentally drill all the way through. I drilled a hole in each piece of brass, on one end so that when matched, the holes would line up with each other.

Lastly, I clamped the brass together in pairs, and shaped them on the linisher. Tomorrow I will finish shaping the clearance recesses on the bottoms and fit the access hatch cover plate. Click here to see images.

Thursday 12th June 2008

Yesterday I received the new brass adjustment screws for the finderscope back from a good friend and machinist. I had them made with a 10mm x 10mm head, straight knurled for grip, with an M6 thread to 20mm long. They probably would have used 1/4 inch at the time but I have metric taps so I went with the closest I could in metric.

Tonight's work was all about getting the hinges fitted together properly with steel dowel pins and linishing them to shape a bit more so they swing freely without friction on the OTA. Once this was acheived, I drilled each hinge in the centre to 4.8mm, then tapped them to M6 thread. As the inside of the hatch cover sits flush against the OTA, I used M6 blind screws on the cover itself. A blind screw has a very flat head, with a series of grips just under the head. The theory is that as you do up the thread (usually with a nut to pull it tight) the grips pull into the steel around the hole and hold tight. As I couldnt use a nut on the outside of the hinge I grasped the long protrusion of the thread with a pair of vice grips, knowingly destroying the end of the screw and proceeded to tighten it from the top. Once tight with the hinges in position, I carefully cut and linished the protruding screws short.

The other half of the hinges were easier as I could afford to have cheeseheads protruding from the inside so I used them instead. I also used a spring washer under these to ensure they don't rattle loose in future. Once tight, again I cut and linished them flush.

Lastly, I drilled a hole straight through the hatch and OTA on the opposing side of the hatch cover plate. The hatch hole I then widened enough to slip a threaded brass knob freely through. The matching hole on the OTA was threaded to match this knob. Click here to see images.

Tuesday 30 Sept 2008

Hadofens rollforming in Queanbeyan rolled two pieces of 50x10mm flat bar for me, in a 293mm diameter. It has to be done in two halves again, to leave metal for the machine to grip.

Once I got them back to the workshop, I test fitted them to the ring flange at the bottom of the OTA. From there I proceeded to cut the rolled steel into two halves, fit and clamp them to the flange ring and weld them together. Once welded, I used a crinder and linisher to clean up the welds.

I also picked up a 350 x 350 x 12mm thick steel plate, to form the back of this new ring and make the whole thing into the primary (mirror) housing cell.

Check out the photographs on the image pages.

Wednesday 01 October 2008

Using an oxy-acetylene cutter, I cut the 12mm steel plate into a circle. I used a specialised compass from a centre punched hole in the centre of the plate to guide the cutter. Temperatures of around 800 degrees are required to cut this so much safety precaution was taken.

To finish off, I tack-welded the OTA ring onto the plate to act as a guide for grinding the edge smooth to shape and size. Once there, the OTA ring was belted off again, breaking the tack-welds.

Check out the photographs on the image pages.

Thursday 02 October 2008

Today was the day where the newly made roll-formed ring would be made one with the base plate, to form the primary housing cell. Placing the ring together with the OTA flanged ring onto the base plate, I centered them on the plate then clamped them all to the bench. A few spot welds on the inside and outside locked it in position.

I then performed a few stitch welds at intermittent and opposite sides of the ring to avoid any buckling due to heat. Then I finished fillet-welding the inside, followed by the outside.

Whe whole assembly then was hand finished freehand on a linishing belt, with a quick flap-disk run over the whole lot to remove any welding slag and pilling.

A test-fit of the OTA flange showed a nice snug fit, without being so tight you have to force it off. After a bit more of a sand and paint it should come up a real treat

Check out the photographs on the image pages.

Friday 03 October 2008

Using a protractor, I marked three points around the outside of the primary housing cell and centre-punched them for drilling. Using a 5mm drill bit, followed by a 1/4 inch BSW tap, I drilled and tapped all the way through the housing and the OTA ring. (Clamped inside in position.)

The holes were cleaned up by countersinking them slightly, then the outside holes on the housing cell were drilled out oversize to allow the brass screws to slide through unrestricted. The OTA ring was left tapped.

To make a locator lug for ease of replacing the cell during maintennance, I cut out a slot from the rim of the housing cell. With the OTA ring clamped in position again, I centre punched in the middle of this new slot and drilled and tapped using a 8.5mm drill bit followed by an M10 x 1.5mm tap. To make the lug itself, I used an M10 bolt and chopped off the head and most of the thread, leaving enough thread to screw a few turns into the OTA ring.

On the inside, I deliberately left it so that it would not protrude, so I could fix it in permanent position by filling it with weld.

Check out the photographs on the image pages.

Sunday 05 October 2008

Today I had a bit of a trial look at how the primary mirror and collimation plate would fit and look inside the PHC with the brass retaining ring fitted. It looks beautiful.

I cleaned up the holes in the end of the OTS, cut the thumb screws a little shorter for the PHC to OTA ring and trial fitted it all. Now all it needs are the collimating bolts and a slap of paint then it is ready to accept the mirror assembly. Click here to see images.

Sunday 19 October 2008

After much careful studdy of the 1866 article with the cutaway drawing of the primary cell, along with the photographs of the existing one overseas, I came up with a design that works. The Drawing in the afore mentioned article just didn't make sense.

In the end, my anonymous machining contact, "K" tok my drawings and turnde out three bolts from brass. The larger bolt that goes through the primary housing cell, is 1/2 inch UNC and about 3/4 inches long to allow some movement for collimating through the 1/2 inch steel plate. The inner bolt is 1/4 inch NC and slides freely through the centre of the 1/2 inch bolt and serves as a lock.

To mark out the holes exactly, I used a piece of paper on the back of the collimation plate (CP), held firmly in place and "Roughed" the centre position where the vanes are and the positions of the holes. Punching a small hole through the middle point, I then placed it centrally in the pre-punched mark on the inside of the primary housing cell (PHC). It was then a simple matter of punching through the paper to mark all the corresponding holes for drilling and tapping later.

All the holes around the CP that looked like the had studs snapped off, cleaned out nicely and turned out to be dirt and corrosion. I acquired some brass cheeze head set screws to fit and secured the brass mirror retaining band onto the CP. Click here to see images.

Sunday 19 October 2008

Well, the mount molds turned out to be to costly for now. (Almost $2000 to get them cast) so I picked them back up from the founder and decided to assemble the mount and base with the wodden molds painted up to look the real McCoy.

This means the OTA cannot be placed on top of this mold, but it will be for all intents and purposes, a fully working replica.

Much drilling, sawing, sanding and screwing was done to fit all the peices together, but as I am not very good at working with wood, it was a hard task. I drilled holes in all the appropriate places to fit all the brass bits fabricated thus far. It seems such a shame to have made all this, only to not complete it with the cast mount.

However, it all fit together well and LOOKS beautiful. I sprayed the molds black to match the OTA and approximate the real thing, then gave the base a good coat of lacquer.Click here to see images.

Tuesday the 21st of October 2008

Today I painted the PHC and the ring it sits on. Matt black killrust on the inside, gloss black killrust on the outside. I also sanded a couple of the rough spots off the first paint job on the OTA and re-applied fresh paint.

I also drilled and tapped (M6) the bottom of the azimuth adjustment post and bolted it through the MDF replica mount mold. Click here to see images.

Thursday 23rd of October 2008

Today the mirror cell was completed. The collimation bolts were test fitted, then removed and peg holes drilled in each part of the bolt for tightening ease. The mirror cell was then re-fitted and the optics proved on a distant hill. At 7 kilometers I could plainly see individual grass stalks and flowers on the hill. Click here to see images.

Woodwork

Sunday 9 March 2008

Today I stripped a pallet down for the base of the telescope. Using an electric planer, I dressed all four sides of each timber, then with a drop saw, dressed off the ends.

Working from photographs, I estimated the height of the base to be just over knee height, so this was used as a scale. Once I cut all the timbers to length, they were laid out to estimate angles.

For the butt joint on the rear leg, the angle on the end of the bottom cross bar worked out to be about 25 degrees.

Using a chisel and mallet, I cut out a butt joint in the rear leg, then chiseled off the end of the bottom crossbar to fit inside the leg. Take a look at these images to see what I mean.

Tuesday 25th March 2008

Today I decided that it was time to set up a rig to test and gain the exact focal lengths of the optics, before I start cutting holes in the tube.

Using my old Celestron Tripod as a base, I cut and screwed together some pine and MDF boards to make a swivelling yoke and bolted a length of timber between them like a rotating see-saw.

I mounted the base plate for the primary mirror on one end. I welded together some random scrap lengths of steel tube with threaded holes and thumb screws for adjustment. This was screwed on top of the see saw at about 5' 2 inches. This will hold the focusing tube with eyepiece at the top, and the secondary mirror unit halfway down.

Once I get the secondary housing back from repairs, I will mount all the mirrors, point the rig at the moon or something bright at night and adjust until all the focus and distances are perfect. Once focused, I will lock everything into place and carefully measure all the relevant distances. Then I can start cutting the corresponding holes in the tube, and cut the tube to length. Click here to see images.

Optics Thursday 27th March 2008

Finally the mirrors are all in place. I used double sided tape to temporarily hold the secondary onto the angle block for this test. The housing is still under repairs at present.

Upon receiving the mirrors, I have photo-documented damage and inclusions in the surfaces and edges. There is some scratching of the glass surfaces and chips from the edges and corners.

With the primary fixed to the rig, the balance favored that end. I used a very high-tech counterweight to fix this. (Plastic bucket with a litre tin of paint in it.)

To gain first focus, I pointed the rig in the general direction of a distant hill about 7 kilometres away. Using the afocal method, I hend-held my DSLR over the eyepiece and took a couple of snap shots, first of a bunch of leaves in a tree accross the road, then at the distant slope. Individual grass fronds were clearly visible.

I measured the relevant focal distances with a tape measure and wrote them down for later tube-cutting.

Next, I waited until dark and a rising waning gibbous moon. I must say, that even though the optics are showing signs of age damage and wear, the image was clear, sharp and spectacularly beautiful! Click here to see images.