Selasa, 04 Juni 2013
Colorado State Senate President Recall Vote Is A Go
Shall Not Be Questioned reports that the Colorado state senator president who voted for the magazine ban will now have to face a recall election. This is a good thing; even if he survives the recall election, the cost of doing so is substantial, and to keep him in office will require the billionaires who fund gun control efforts to divert funds to protecting these fools.
Senin, 03 Juni 2013
Bending 1/4" Thick Aluminum
One of my readers suggested an interesting way of solving the problem of needing to bend 1/4" aluminum into a hexagon: notch the aluminum where you need to bend it. I could use my vertical mill and an 1/8" diameter end mill to put a 1/16" deep, 1/8" wide notch in 1/4" aluminum plate, then bend the aluminum on the metal brake.
I would only be bending 3/16" aluminum (which the brake should be able to do) at the notch, and because I could place the notch quite precisely, I would get much more exact results than simply marking the line in 1/8" inch aluminum. I wouldn't be able to use the 1/8" aluminum sheet that I have, but I suspect that it would be stiffer than the layered approach I discussed recently, and perhaps no more labor, since I would not have to drill and tap the individual layers.
UPDATE: This did not work as I expected. I had some 1/4" aluminum to experiment with, and the results were disappointing. I used my new 1/8" end mill (which notched the aluminum beautifully) to cut a .125" wide, .125" deep slot, then tried to bend it to a 60o angle. Even though it was only a 1/8" thick layer that I was actually bending, it produced a slight break, rather than a smooth bend. I thought that perhaps the problem was that I needed a wider slot relative to the depth, so I next cut a ..19" wide, .100" deep slot -- and that did not want to bend at all. I think I will go for the two layers of 1/8" aluminum instead. I can drill and tap the layers for 8-32, 1/4" long screws right next to each vertex, and have something impressively strong. (The shear strength of a single 8-32 steel screw is > 2700 pounds.)
UPDATE 2: I am beginning to think that what make have happened is that aluminum work hardens, and cutting the notch with the end mill may have work hardened the aluminum underneath the notch enough to make it too brittle.
I would only be bending 3/16" aluminum (which the brake should be able to do) at the notch, and because I could place the notch quite precisely, I would get much more exact results than simply marking the line in 1/8" inch aluminum. I wouldn't be able to use the 1/8" aluminum sheet that I have, but I suspect that it would be stiffer than the layered approach I discussed recently, and perhaps no more labor, since I would not have to drill and tap the individual layers.
UPDATE: This did not work as I expected. I had some 1/4" aluminum to experiment with, and the results were disappointing. I used my new 1/8" end mill (which notched the aluminum beautifully) to cut a .125" wide, .125" deep slot, then tried to bend it to a 60o angle. Even though it was only a 1/8" thick layer that I was actually bending, it produced a slight break, rather than a smooth bend. I thought that perhaps the problem was that I needed a wider slot relative to the depth, so I next cut a ..19" wide, .100" deep slot -- and that did not want to bend at all. I think I will go for the two layers of 1/8" aluminum instead. I can drill and tap the layers for 8-32, 1/4" long screws right next to each vertex, and have something impressively strong. (The shear strength of a single 8-32 steel screw is > 2700 pounds.)
UPDATE 2: I am beginning to think that what make have happened is that aluminum work hardens, and cutting the notch with the end mill may have work hardened the aluminum underneath the notch enough to make it too brittle.
More Little Discoveries
I actually did roll Big Bertha out last night....but discovered that I could not actually look through the finderscope to get the telescope aimed at Saturn. Why? Because before, the finderscope was mounted low enough on the upper cage that I could look through it because my cheek was actually inside the tube. Now, that's not possible. One solution was to machine something that lifted the finderscope away from the tube.
The other alternative is to use a right-angle finderscope (and I have one of those lying around). The downsides are:
1. I have to move one of the mounting rings on the current finderscope bracket down an inch, because the right-angle finderscope is a bit shorter.
2. The right-angle finderscope is a very nice University Optics 8x50mm, but the eyepiece lacks not only illuminated crosshairs -- it lacks crosshairs. I think I will be able to move the illuminated crosshair eyepiece from the current finderscope to the new one -- perhaps with a little bit of making some sort of adapter on the lathe.
I confess that having switched to a straight through finderscope some years ago, I find the idea of switching back to the right-angle finderscope increasingly attractive. While it is an unnatural feeling to use one of these on a telescope, having the finderscope sitting 5" away from the scope tube isn't wonderful, either.
On the plus side, hunting for the right-angle finderscope this morning in the telescope garage also brought to light some of the self-adhesive black flocking material and another Losmandy counterweight. Right now, I have corrected the additional weight of the solid tube with a bucket that holds one of those citronella candles -- it's a bit silly looking.
The other alternative is to use a right-angle finderscope (and I have one of those lying around). The downsides are:
1. I have to move one of the mounting rings on the current finderscope bracket down an inch, because the right-angle finderscope is a bit shorter.
2. The right-angle finderscope is a very nice University Optics 8x50mm, but the eyepiece lacks not only illuminated crosshairs -- it lacks crosshairs. I think I will be able to move the illuminated crosshair eyepiece from the current finderscope to the new one -- perhaps with a little bit of making some sort of adapter on the lathe.
I confess that having switched to a straight through finderscope some years ago, I find the idea of switching back to the right-angle finderscope increasingly attractive. While it is an unnatural feeling to use one of these on a telescope, having the finderscope sitting 5" away from the scope tube isn't wonderful, either.
On the plus side, hunting for the right-angle finderscope this morning in the telescope garage also brought to light some of the self-adhesive black flocking material and another Losmandy counterweight. Right now, I have corrected the additional weight of the solid tube with a bucket that holds one of those citronella candles -- it's a bit silly looking.
Minggu, 02 Juni 2013
Big Bertha In Daylight
Big Bertha in previous incarnations has never worked out terribly well in daylight because of the open tube structure; stray light is always going to be a problem. I was therefore at first unsurprised when I used it to look at the television towers on top of Big Basin (which is a number of miles away) this afternoon. But even at 222x, I was quite pleased with the optical quality. Now, if only it gets dark to see something before I have to go to bed!
During church this morning, I suddenly realized a solution to a problem that has been bothering me about making hexagonal telescope rings to hold Big Bertha to the mount. It would be impossible to use this metal brake that I have to bend 1/4" aluminum -- but 1/8" thick aluminum is probably too flexible. But what I bent 1/8" aluminum into the inner part of the lower half of the hexagon, and another 1/8" thick piece to be effectively the outer layer of the hexagon? Then bolt them together at the vertices of the hexagon, so that I get most of the stiffness of a 1/4" thick ring, with the ease of construction of the thinner pieces? Even better, I have a large sheet of 1/8" thick aluminum that I could use for this purpose.
I have therefore been experimenting with making a small set of hexagonal telescope rings (like about 2" across) just to get some practice at making them on a small scale first. And yes, 1/8" thick rings feel stiff enough, but because of the square/cube law, they almost certainly would not be stiff enough for the size that I need for Big Bertha.
I feel the need for a metal shear, but by the time I see the cost and size, I will probably just go to my friendly metal store and pay them to use their shear instead. The bandsaw that I have just doesn't do that good a job on metal (it is really a woodworking tool), and cutting small slices with the chopsaw is impractical.
During church this morning, I suddenly realized a solution to a problem that has been bothering me about making hexagonal telescope rings to hold Big Bertha to the mount. It would be impossible to use this metal brake that I have to bend 1/4" aluminum -- but 1/8" thick aluminum is probably too flexible. But what I bent 1/8" aluminum into the inner part of the lower half of the hexagon, and another 1/8" thick piece to be effectively the outer layer of the hexagon? Then bolt them together at the vertices of the hexagon, so that I get most of the stiffness of a 1/4" thick ring, with the ease of construction of the thinner pieces? Even better, I have a large sheet of 1/8" thick aluminum that I could use for this purpose.
I have therefore been experimenting with making a small set of hexagonal telescope rings (like about 2" across) just to get some practice at making them on a small scale first. And yes, 1/8" thick rings feel stiff enough, but because of the square/cube law, they almost certainly would not be stiff enough for the size that I need for Big Bertha.
I feel the need for a metal shear, but by the time I see the cost and size, I will probably just go to my friendly metal store and pay them to use their shear instead. The bandsaw that I have just doesn't do that good a job on metal (it is really a woodworking tool), and cutting small slices with the chopsaw is impractical.
Drill Doctor
If you have ever wondered why a drill bit was taking forever to cut through steel or aluminum -- it is usually because the drill bit has been dulled by turning it at too high a speed or without sufficient lubrication.
I bought the Drill Doctor to solve this problem yesterday -- the more expensive model, because that is all Home Depot carries -- and I am glad that I did. If you are wondering what a Drill Doctor is -- no, it isn't a guy with a German accent asking a drill bit on the couch, "Zo, how long have you felt like you are going around in circles?" It is a gadget for sharpening drill bits.
It isn't quite as simple as I had hoped or expected, but it is simple enough. You put the dull drill bit into a chuck, press a button, put the chuck into an alignment guide, then put the assembly into another part where a diamond wheel sharpens it as you turn the chuck. It is a very clever design, although it isn't foolproof. If you don't do it exactly right, you don't get a sharp bit. Most of the bits that I had that needed sharpening improved dramatically, sometimes on the second try. It seems to work better on the larger bits -- but those are the ones that for me typically get dull, because I am usually drilling large holes in metal with them.
This should save me a bit of time on ScopeRoller manufacturing, as well as meaning that I won't have to run out and buy a new drill bit as often.
I bought the Drill Doctor to solve this problem yesterday -- the more expensive model, because that is all Home Depot carries -- and I am glad that I did. If you are wondering what a Drill Doctor is -- no, it isn't a guy with a German accent asking a drill bit on the couch, "Zo, how long have you felt like you are going around in circles?" It is a gadget for sharpening drill bits.
It isn't quite as simple as I had hoped or expected, but it is simple enough. You put the dull drill bit into a chuck, press a button, put the chuck into an alignment guide, then put the assembly into another part where a diamond wheel sharpens it as you turn the chuck. It is a very clever design, although it isn't foolproof. If you don't do it exactly right, you don't get a sharp bit. Most of the bits that I had that needed sharpening improved dramatically, sometimes on the second try. It seems to work better on the larger bits -- but those are the ones that for me typically get dull, because I am usually drilling large holes in metal with them.
This should save me a bit of time on ScopeRoller manufacturing, as well as meaning that I won't have to run out and buy a new drill bit as often.
Lessons in Precision
I explained to a ScopeRoller customer a couple of weeks back that the cost of precision is a sliding scale, and an asymptotically increasing scale at that. "Fifth of an inch precision is free; hundredth of an inch precision costs a bit, thousandth of an inch precision costs a lot." I had that lesson myself over the weekend -- but that cheaping out on precision has its own costs.
I mentioned that I was not happy with the ability of Big Bertha to hold collimation, and that I suspected that the spider holding the diagonal mirror was the problem. As the telescope went up in altitude, I could see the laser beam from the collimator moving as well. I decided to replace the .0325" thick aluminum legs, which were held in position by tension, with .040" thick steel legs. These should be at least four times as stiff as the aluminum legs because of material and extra thickness.
In addition, the cylinder that connected the legs to the diagonal mirror holder was made of acetal, and left about an inch of the 1/4"-20 screw that holds the diagonal mirror holder unsupported. My thought was to replace the acetal cylinder with a full length aluminum cylinder instead. Because aluminum is about 20 times as stiff as acetal, weight for weight, I could go to a somewhat smaller cylinder and have far better stiffness. I had hoped to find a piece of aluminum tubing 1/4" ID with about an 1/8" wall, but the local metal supply store had nothing like that, so I took a piece of scrap .811" aluminum rod, turned the ends, then bored a 1/4" hole through the middle with the lathe.
Here is the spider, waiting for the flat black paint to dry:
The trick here is that the legs needs to be 120o apart, so the attachment holes on the cylinder where the legs mount need to be 120 degrees apart. I decided that yes, I could use some of my precision gadgets to make them 120o +- 0.5o -- but why bother? I could just measure with a protractor, and that would be good enough. Right?
Wrong. It turned out that they were far enough off that the cylinder was not centered in the tube -- not even close. So I ended up doing the extra work to do it right -- and it wasn't really much more work than doing it sloppy and wrong. Here's a picture with another piece of aluminum in place, not the one that I drilled:
It sounds a bit like a Rube Goldberg contraption, but it isn't. The tilting table on the right is at 90o; mounted on the tilting table is a rotary table made by Sherline. It has a coarse measure that reads to the degree (and you can certainly interpolate quite a bit more finely) and a vernier measure (the red handwheel) that gives marks down to 0.1o. Mounted on the rotary table is a 3" three jaw chuck, which held the cylinder I was trying to mark. With this, I was able to determine that my old tapped holes were as much as 10o off of where they should be.
Use precision tools for precision work; use brute force tools for brute force work. I could have tried to drill and tap the holes with the vertical mill, but because the cylinder was 3" long, and the chuck really does not hold something that long terribly well under any real load, it was not likely to be a success. So I settled for marking where the holes should be with an end drill for angle and length down the cylinder, and then drilled and tapped the holes on the drill press. Once you have marked the hole's center with an end drill, the twist drill in the drill press does a pretty impressive job of following that hole, even if you aren't exactly on location with the twist drill.
Anyway, here it is installed:
Yes, there is a slight bend to the arms; better to have some compression rather than tension, and by bending the arms slightly, I was able to get the diagonal centered to better than 1/16" -- perhaps even as close as 1/32". (The curve may also smooth out diffraction spikes -- the four or six arms that you often see in observatory astrophotographs.) This is about as much as I can expect or even need for this part of the problem.
There is no longer the gross and obvious miscollimation of the diagonal as the telescope rises in altitude. The sky did not clear here last night until I was exhausted and ready for bed, but perhaps tonight I will roll it out and see how it goes.
I mentioned that I was not happy with the ability of Big Bertha to hold collimation, and that I suspected that the spider holding the diagonal mirror was the problem. As the telescope went up in altitude, I could see the laser beam from the collimator moving as well. I decided to replace the .0325" thick aluminum legs, which were held in position by tension, with .040" thick steel legs. These should be at least four times as stiff as the aluminum legs because of material and extra thickness.
In addition, the cylinder that connected the legs to the diagonal mirror holder was made of acetal, and left about an inch of the 1/4"-20 screw that holds the diagonal mirror holder unsupported. My thought was to replace the acetal cylinder with a full length aluminum cylinder instead. Because aluminum is about 20 times as stiff as acetal, weight for weight, I could go to a somewhat smaller cylinder and have far better stiffness. I had hoped to find a piece of aluminum tubing 1/4" ID with about an 1/8" wall, but the local metal supply store had nothing like that, so I took a piece of scrap .811" aluminum rod, turned the ends, then bored a 1/4" hole through the middle with the lathe.
Here is the spider, waiting for the flat black paint to dry:
The trick here is that the legs needs to be 120o apart, so the attachment holes on the cylinder where the legs mount need to be 120 degrees apart. I decided that yes, I could use some of my precision gadgets to make them 120o +- 0.5o -- but why bother? I could just measure with a protractor, and that would be good enough. Right?
Wrong. It turned out that they were far enough off that the cylinder was not centered in the tube -- not even close. So I ended up doing the extra work to do it right -- and it wasn't really much more work than doing it sloppy and wrong. Here's a picture with another piece of aluminum in place, not the one that I drilled:
It sounds a bit like a Rube Goldberg contraption, but it isn't. The tilting table on the right is at 90o; mounted on the tilting table is a rotary table made by Sherline. It has a coarse measure that reads to the degree (and you can certainly interpolate quite a bit more finely) and a vernier measure (the red handwheel) that gives marks down to 0.1o. Mounted on the rotary table is a 3" three jaw chuck, which held the cylinder I was trying to mark. With this, I was able to determine that my old tapped holes were as much as 10o off of where they should be.
Use precision tools for precision work; use brute force tools for brute force work. I could have tried to drill and tap the holes with the vertical mill, but because the cylinder was 3" long, and the chuck really does not hold something that long terribly well under any real load, it was not likely to be a success. So I settled for marking where the holes should be with an end drill for angle and length down the cylinder, and then drilled and tapped the holes on the drill press. Once you have marked the hole's center with an end drill, the twist drill in the drill press does a pretty impressive job of following that hole, even if you aren't exactly on location with the twist drill.
Anyway, here it is installed:
Yes, there is a slight bend to the arms; better to have some compression rather than tension, and by bending the arms slightly, I was able to get the diagonal centered to better than 1/16" -- perhaps even as close as 1/32". (The curve may also smooth out diffraction spikes -- the four or six arms that you often see in observatory astrophotographs.) This is about as much as I can expect or even need for this part of the problem.
There is no longer the gross and obvious miscollimation of the diagonal as the telescope rises in altitude. The sky did not clear here last night until I was exhausted and ready for bed, but perhaps tonight I will roll it out and see how it goes.
Projection
Yet another person who wants to see the government executing people for disagreeing with him. From the May 30, 2013 Charleston (W.Va.) Gazette:
Oh yes: he's not terribly well-educated.
The NRA advocates armed rebellion against the duly elected government of the United States of America. That's treason, and it's worthy of the firing squad. The B.S. needs a serious gut check. We are not a tin pot banana republic where machine gun toting rebel groups storm the palace and depose the dictator.
We put the president in the White House. To support the new NRA president's agenda of arming the populace for confrontation with the government is bloody treason. And many invite it gladly as if the African-American president we voted for is somehow infringing on their Constitutional rights.He wants to see people who disagree with him killed by the U.S. military...but thinks that concern about this country turning into a "tin pot banana republic" is absurd. I think I see why Americans are arming.
Normally, I am a peaceable man, but in this case, I am willing to answer the call to defend the country. From them.
To turn the song lyric they so love to quote back on them, "We'll put a boot in your ---, it's the American way."
Except it won't be a boot. It'll be an M1A Abrams tank, supported by an F22 Raptor squadron with Hellfire missiles. Try treason on for size.
Oh yes: he's not terribly well-educated.
This foaming at the mouth, Obamar is coming for the guns, Nanny Bloomberg is a bad billionaire, and most despicable of all, those survivors and victims are pawns in the liberal agenda is knuckle-dragging Cretan talk.He doesn't know the difference between a cretin (and isn't that insulting to the mentally retarded?) and a resident of Crete. But he is a professor of journalism.
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