This blog is mainly about Telescope making, and some things about my politics. At last we finally have a President that can say "Fool me once; shame on you. Fool me twice; shame on me." instead of mixing up with an old Who song.

Saturday, July 26, 2008

Whet the hell

I made the new tool. and little did I know that I would run out of #80 grit. But not before I got the tiles on the new tool all in contact. Here are some pictures of the tool after I started grinding with it. They progress from "a lot in contact" to "almost all in contact". I the former, you can still see where some of the grit has attached itself to the wax leftovers. As it progresses, you can see how all the tile glazing begins to go away, such that in the second to last picture, its only in the center of the tool, and in the last picture its virtually gone.

After conferring with the gents on the ATMLIST, They all agreed that I should jump ship and go with the #120. So what the hell. I cleaned up the shop thursday night, I did it. And it's working the charm. Currently I am fighting to get rid of one really nasty pit , and to get the focal length about an inch or less longer than it is right now. The way I figure, if I keep the tool on top, and go through about 3 or 4 more whets, the big pit should be gone, and the FL should be just about right. I'll bet that I get onto the #220 tomorrow evening.
So I went up to the disposable tool store today (Harbor Freight) and got a few things. A new dusting brush for my workbench - last the last one, and the one that I was using is really for scrubbing floors... (wrong tool). And I got an old fashioned red liquid thermometer to hang up out there (it hit 86 degrees today). I got a 10x magnifier and an LED flashlight and a new apron and some new blades for the box cutter. And some other stuff I forget right now.
$24 even for cheap crap. Lotsa cheap crap. And the way I use it, it will never wear out. I love that place. Sure its made with cheap Chinese slave labor, but what isn't anymore? I am so bad sometimes. But I gotta do something to feed my leftist guilt, eh?

Sunday, July 20, 2008

Mirror Mantra

Sailors on tall ships had them while trimming sails. Old Irish women had them while weaving cloth. Field hands had them while picking crops. Chain gangs had them while tarring roads. Bakers had them while kneading bread. Hikers had them while on the trail. When I mow the lawn, I have several. There is even a modern one for computer programmers. "Working 40 hours on the Xerox line" by Stan Rogers.


And thus, today, when I dosed my new tile tool with a charge of #80 grit and some water and started the old back and forth, these rhythmic songs started creeping into my brain like a slow distant freight train.

It was hot out there. About as hot as I would attempt it. Over 90 degrees in the shed by the time that I called it quits at 3pm. My hands were wet with water, and that helped, but boy, I really need to wait until after August for this thing. Or at least wait for a cloudy day.

But to keep going and to keep even pressure and even strokes, it was the meaningless mantra going through my head that eased all the work.

I don't like music when I work. I find that I get into listening to music way to much. I ponder it when I do. Maybe it's that I don't like things to interrupt the music. But when I do work in my shed, on the telescope or whatever, or when I am programming, I like things very quiet so that I can concentrate. And then the voices start in my head. I talk to myself in meaningless ways - giving myself encouragement, and admonishing myself on mistakes made. Or I count how many strokes it takes to make one round (between 60 and 73). There is the rhyme and rhythm of counting that all blurs into simple meaninglessness after you miss-count but continue making the noises in your head anyway, just for the hell of it, and because you aren't done yet.

Porter was wrong. The mirror isn't the thing. Its the cadence... now that, the cadence is the thing.

More pictures next time. They are out in my shed in the camera on the workbench, and I am too hot and too lazy to go out and get it right now. Not too exciting. Same old tool. I have it wrapped in clear packing tape now, and I'm not so sure I like that idea too much. The slightest wrinkle causes little tunnels where grit can reside. So when I finally get to the #120 and later ones, I am going to have to strip all that off, clean the tool and start over from the wax stage each time. I keep telling myself that I did manage to save a lot by not using dental $tone. I'm cheap - its worth it.

Where I left off with the mirror was hogging it with a 2" pipe cap. I thought it would take forever to get this new tool to the point where every tile is fully touching, but after today, it looks like most of them are there, and even some of the ones I thought would simply never make contact are half way there. I'm pretty impressed with tile tools, let me tell you.

All of the worry about having the tool stick - like when you have two peices of glass - is completely gone. You spend your time grinding instead of worrying. You start thinking of how you can press down on it more, rather than thinking how much can this this sucker drag. I am truly amazed.

After a while, I noticed that the glazing was being removed in a ring around the center of the tool. It was a stark reminder of how grinding of the mirror really works.

If the tool is grinding away at an annulus ring, then the mirror on top, must be grinding a hole in the center to match it. Sure enough, when I took my first spherometer measurements, it was .038 in the center and .036 at the edge. .038 is a little too deep for me, and I wanted to remove that hump of glazing on the tool, so I tried it about 10 rounds with the tool on top. I was worried that the packing tape would be slippery when wet, but it was actually just fine to hold on to, dry hands or no. After 10 rounds, I checked it again. .0365 in the center, and .0345 at the edge. And I got rid of that glazing.

One thing I noticed was that using a big tool like this makes the surface a lot more even than you can control with a 2" pipe cap or 3" flange. As my data proves, the numbers were all over the board. But with just a gut feel even after such a short time "lapping in " my new tool, its obvious that these kinds of anomolies will subside. I checked all over the mirror, and its really very even from the center all the way out to the 10.5" ring. None of the measurements I took inside that ring varied from .0365 at all. At the 11" ring, none of them varied from .0350, and at the edge, none of them varied from .0345".

So, the next plan...
1. Wait for a cooler day.
2. Grind with tool on top for a while to get the the measurement between .0320 and .0325 all over if I can.
3. Switch up to #120 :)


Saturday, July 19, 2008

Waxen it down

I might be movin' to Montana soon
Just to raise me up a crop of Dental Floss
Raisin' it up
Waxen it down
In a little white box
I can sell uptown

-Frank Zappa, Montana

So I have the tool now, and I sealed it with some deck sealer I had around and let it dry. It says its for concrete, and it says you can clean it up with soap and water.


I tried soap and water. The brush felt like I put rubber cement on it. Then I tried MEK. It just stank. Then I tried alcohol - worthless. Finally the old standby, paint thinner - it did the job. oy. But the tool is sealed at least

Then I levelled the tool and put a packing tape dam around the edge. Levelling is very important, since I would be pouring liquid wax on it in a bit.

After melting two bricks of the "Gulf Wax" used for canning preserves and such, I poured the wax over the tiles and let it congeal. It was about 1/16 to 1/8 inch thick. And while it was still soft, I scrapped it off with a little wooden scrap wedge that was handy.

One thing I noticed, was little bubbles in the wax, and I was disappointed in them. This kind of wax has a lot of that anyway, but here it seems like a place for disaster to hide. So after I scapped off the wax, I took out my low wattage (10 watts) fine point soldering iron and remelted all the channels to let all the little bubbles pop to the surface.

Bubble free, and with wooden wedge in hand, I scrapped 1/32" of wax out of the channels. It just came right up. I noticed that some of the wax was coming loose around the edges, so I packed it tight and took the propane torch to it and light (ever so lightly ) wafted the flame and sealed them.

Alas, I let it drip down the side of the tool once or twice. And while I could peel it back off, there is always some wax left. Paint (red acrylic - leftover from my front door) doens't like to stick to wax much, and so, this morning, when I went out to paint it, I scrapped off as much as I could and painted it anyway. I hope it work, but I have a feeling that it will peel before too long. I will put another couple of coats on and then wrap the whole thing in several layers of packing tape as David suggested.

Here is a video of me scraping wax. Its pretty easy when its warm.

Here are some other pics.

I put a couple of bricks under an old kitchen pan. That and the wax and the torch and some tape is what I used.

Here is what the wax looks like when you scrap it off. I did it diagonally with a little wooden wedge I had laying around. If I had done it normal/parallel to the channels it would have caught in them in an uncontrolled way.

Here it is after removing the wax and the dam.

Closeups of the wax after scraping 1/32" from the channels.

Sunday, July 13, 2008

No animals were harmed in the making of this mirror

I rewarded myself for having handily passed my first certification test by working out in my shed on my grinding tool today. Plenty more pictures. It rained like crazy today. Very odd for July in Georgia. On loud thunderbolt made the lights flicker and we lost a small branch out of one of our sweet gum trees. I normally collect rain water around here for garden irrigation (because of the 5 year drought) and I used some of it to fill my tub of water.

Anyway, David Harbours method of creating the grinding tool is a charmer. I slid it off the mirror friday evening after I got home without a hitch. Today I pulled out all of the match sticks, and the aluminum foil and wirebrushed any loose cement and picked at it with an awl. I finally bevelled the sharpest edges around the outside edge with the sharpening stone.

Unless you count insects, I didn't harm any animals. But man I hate wasps, and there are a couple of dead ones in my shed. And an ant that decided to crawl under my wirebrush. Oh well. Albert Schwitzer, I'm not.
In no particular order, some things I did or noticed with some comments. This is the edge after removing the dam. It has some puts that I will fill before coating with the water seal.

An edge-on view of how one row got a little skewed from the rest.

Edge on view of the smallest of the partial tiles. notice that they are a little slanted down to the left. Eventually they may come into contact maybe.

This is the right after removing the dam around the outside. you can see that I have removed some of the match sticks which were still wet. There were surprisingly few places where little "posts" of cement occurred at the intersection of match sticks. I guess its because I used square tiles instead of hex tiles like David did. Around the edge in the gaps are wadded up aluminum foil. If I were to do this again, I don't think I would use that, as the aluminum seems to have chemically reacted to the pOH of the concrete and got brittle, mushy, or flat out disintegrated. I had to scrap most of it out. I think I would try somthing non-porous, like silly putty or something.
Here is another shot of one of the chunks of foil.

Here it is with a third of the sticks removed.

And here I am using the awl to get the others. its really a matter of flicking them out of the way. Once that is done there were several places where cement extended down to the face of the tile. But there wasn't much of that, and a stiff wire brush got it all.

Like I said, it rained to beat the band. Here looking across my back yard. The camera was up under the brim of my hat.
I Thought I would rinse it off in the storm, but soon realized that all I was doing was getting grass on it. So I brought it back in and dipped a few gallons of water from my rain catching system into my wash tub. I stayed a little dryer that way too, heh!

This is how it looked right before rinsing it. I did the back of it too. It was a little mottled. the deepest indentation on the right is about 1/8 inch. Later I ground it over an old round concrete stepping stone. Smooth as err... concrete now :)

Here is one section of where I bevelled the edge.

Here is a little chip on one of the tiles. Hope it doesn't hurt much.

Thursday, July 03, 2008

No leftovers

At 16 years of wedded bliss, I can say that I don't mind leftovers anymore. Susan is a really good cook, and its par for the course I guess.
But when you take apart a lawn mower or a printer, or some other thing with screws, gaskets, washers, springs, levers and opto-interrupters (not that the lawnmower has that) and you start to put it back together again, I can't help but get two mutually exclusive yet sinking feelings in my stomach...

"There aren't enough parts here to put it back together..." and "I screwed something up, because there are two many parts here."
When I get both of those feelings at the same time, then I know I am doing it right and all will work out well.

So when I estimated how much dry mortar to dip out of the quikcrete bag to put into the wheel-barrow... and wondered if it was going to be enough... and got that feeling... I threw a few more scoops in for good luck. Funny thing about luck... if you get it, you are lucky. Well, I got lucky. There was just enough leftover to fill a crevase by the door of my shed that I keep meaning to fix. Oh happy Friday. (well Thursday, actually, but tomorrow is the 4th :)
After filling in a few of the places of missing tile with tin foil as suggested by David Harbour, I pulled out all of the interim stabalizing match sticks and made ready to pour.

Here is the bag of Quikcrete Mortar mix I used. I estimated that I would use about a quarter of it, and then upped that to on third. Yeah, go ahead, call me a wuss. I put it on a hand truck to get it from my pick-up down to the shed. Easier that way.

Here is the water jug. I used the amount of water that was between the black marks to mix with the mortar mix. The instructions say that you should be able to have 1/2 inch of the stuff on a trowel, and that you should be able to hold the trowel vertically. That seemed too thick to me, so I added a little more water. It was about twice as thick as a slushy down at the 7-11. (we don't have 7-11's down south anymore. But I remember :)

And here it is after I added the mortar. I ladelled it in there, starting from the center and working out, so that there would be no bubbles. It was about 1/2 inch thick as I worked to the edge. After that, I just piled it on, wondering with ever coop full if there was going to be enough. It was hot out there in the shed today, about 90 degrees. I was already sweating, but wondering if I had enough mortar made it worse. And there is nothing worse that having to make a second batch, because you never get it the same consistancy.

One thing I had to do was to level the mirror. If I had listened to Francis O'Rielly, I would have done that beforehand. But of course, I am stubborn and want to learn from my own mistakes rather than the wisdom of others. I'm such a toad.

Its about to storm here in a few minutes, and I left the tool just as you see it here, unwrapped. I'll go out later on for one last screeding and close it up with a damp towel inside and wait a week and see what I get.