How To Attach The Tube (Cont.)

Here's a diagram of a simple to build tensioner for nylon webbing, stainless steel strap, or even belts.

The fixed side attachment doesn't move; I tap this side of the C-channel for a 1/4"-20 bolt.  Depending on the strapping material, I may need a large washer to distribute load across more surface area.  For nylon webbing, I would triple the layers for this attachment point.

The adjustment side attachment consists of a 1/4"-20 tapped hole and a bolt (probably a thumbscrew) with two nuts locked in position at the end of the bolt.  The way that I have found works most easily for this is to drill through a hex head nut into the bolt, tap the hole for 6-32 threads, and use a 6-32 set screw to lock bolt and nut together.  The strap goes through the slot in the side of the C-channel, and is held by two washers inside the captive nuts.  The strap can rotate between the washers, so it isn't a tight fit there.  You have to the get the length of the strapping pretty precisely correct for a snug fit, and then you turn the thumbscrew to clamp everything down.  This also gives some room for strap stretch over time.  If you reach the limits of the bolt, you can redrill the holes on the fixed side attachment, but I am considering this a short-term solution to the problem.

Limiting yourself to a thumbscrew not only simplifies tool-free adjustment, but also reduces the change of putting so much force on the tube that it damages it.

UPDATE: Good news: I asked my pastor this morning where I would steel strapping material on a weekend.  He just happened to have a 50 foot roll of .030" thick, 1 inch wide steel strapping material.  I started work on the device above to use some of this.  I discovered that the vertical mill definitely works better with the longer screw holding everything together; I also discovered that once again, the single most important factor in milling is getting the workpiece really well clamped in position.  Anything that lets it jostle in the vise is a problem.  I also discovered that the 1/4"-20 thumbscrews I had...were something metric, not 1/4"-20.  I guess I will buy two of those tomorrow.

Telescope Project Marches On

There was some pooling of paint at the bottom of the tube when I painted the first coat with the tube on end, so for the second coat, I went back to the suspension approach that I used when applying the fiberglass resin.

The method of holding the tube in the air at that stage wasn't very good, because sometimes the tube started rocking, and then the aluminum tube holding it would go flying off the chairs.  So I came up with a way to prevent the aluminum tube from getting too far afield:

Unlike the first coat, which did not stick spectacularly well to the fiberglassed Sonotube, the second coat stuck quite well.  It still wasn't very even, so I sanded it after the second coat as well, which again evened out the surfaces a bit (although taking off a bit of paint in the process).  There were still some pretty big depressions caused by air pockets in the area where I had used fiberglass cloth, so I mixed a bit more resin, and tried to fill in the holes.

I still won't call the result, after the third coat, "beautiful," but I think it will do, at least until I can talk myself into believing that the big money for a carbon fiber composite tube that weighs 13 pounds less makes sense:

I mentioned a few days back that I was going to epoxy some steel rod on either side of the center line of the tube where it attaches to the dovetail plate to prevent rocking, which would eventually damage the tube.  Then, yesterday, I mentioned that it would be better to have tube rings that lock onto the outside of the tube and screw directly to the dovetail plate.

I am still waiting on a price quote on those rings, and I started thinking.  I noticed that at the edges of the dovetail plate there are a bunch of 1/4" holes.  Hmmm.  Could I mount supports in those holes to prevent rocking?  My first thought was to machine some 1/4" (or perhaps slightly longer) plugs that would provide the support?  I could even just use 1/4" hex head bolts; the heads would provide just the right elevation to prevent rocking (although at the risk of marring the surface of the tube).

But the more I thought about it (and was glad that enamel dries so slowly), it occurred to me there was an even better solution that gives me the flexibility to rotate the tube, not drill permanent mounting holes, solve the rocking problem, and involves minimal use of materials.

1. I take the C-channel which was used to mount the old scope to the dovetail plate, and cut off two 2" sections (preferably the ones that have 1/4" through holes already).

2. Shorten the legs of the C-channel down to 1/16" inch (since I no longer need long legs for stiffness of the section).  Now I have a round tube to flat base adapter.

3. Drill and tap 1/4"-20 holes in each side of the two sections.

4. Buy four leather belts at the thrift store.  (I need about 60 inches total length, and preferably 1 3/4" wide belts.)

5. Use a 1/4"-20 bolt and a washer to hold one end of each belt to each side of the C-channel.

6. Use the belt buckles to secure the tube to the C-channel sections.  (This means that I will need to get roughly similar belt buckles when picking out belts.)

7. Perhaps drill some holes in these belts to get them in a position where I can tighten down the tube without crushing it marring the surface much.

Now I have the 60 pound or so telescope load held by two belts, which is, I think, sufficient to prevent anything from moving or working loose.

An alternative would be to look for some flexible 2" wide stainless steel straps, and apply felt to the inside to protect the tube.  But then I have to figure out a way to secure the steel straps so that they can be loosened without having falling completely off.  The Cave Optical mount that I had long ago used this approach, with a screw brazed into one end of the strap, so that you could loosen the straps at one end, rotate the tube, then retighten.  If I could find something like this (with roughly 60" long straps) that had some way to tighten and loosen tension, this would be preferable.  But the belts might be a quick way to get the telescope operational, and then worry about rings at a later time.

UPDATE: Or Velcro?  This claims that the closure shear strength is 11.0 pounds per square inch.  I can buy a 15 foot by 2" wide piece of Velcro at Home Depot for $28.97, what they call industrial strength Velcro.  If I had ten inches of overlap of hook and loop (and if I understand what they are claiming for the closure shear strength), that would be 220 pounds per strap.  That seems more than enough.  It would not be as elegant as aluminum rings, but it would be light, I could pick up the Velcro tomorrow, and put the telescope together tomorrow afternoon.

UPDATE 2: Or perhaps use nylon webbing with buckles.  The webbing has a tensile strength of 5500 pounds (probably more than the buckles that come with it or where I would attach it).

UPDATE 3: The more I think about it, nylon webbing and Velcro are likely to stretch under load, and that sounds a bit dangerous.  If I can find some steel straps at Home Depot, I could put a bolt through the adjustment end, and use a wing nut to tension it.

Roll Your Own (Rings, That Is)

The quick but inflexible solution for attaching a telescope to the dovetail plate is to drill holes in the tube and turn bolts through the tube into the threaded holes on the dovetail plate.  The more elegant solution (because it lets you rotate the tube into more useful viewing positions, with a little bit of effort) is to use rings like these.  I have bought Ken Dauzat's rings before for another telescope, and I was very pleased with them.  I have asked for a quote for the monster tube, and I am shuddering a little at the likely price.

But I saw this device for rolling your own rings from either tubing or flat.  It's $169, but that doesn't seem like  a particularly high price if it comes out the same price as buying one pair of rings.  Does anyone have experience using such a tool?

New PJMedia Article

At The Brink: Dr. John Lott Defines America’s Calamity

To Parody The Dojo Owner in Napoleon Dynamite

"I developed this while spending two hours in the hexagon!"

It actually came out rather well.  I started with the 20.125" diameter aluminum ring, used a protractor to measure 60^o angles, drew lines, then cut them using both the table saw and the bandsaw.  The first try with the bandsaw was disappointing -- it produced a very ragged edge, until the blade broke.  Then I switched to the table saw, which produced a straighter but very rough edge -- and then I went back to the bandsaw, using a wider blade, which produced a much straighter line.  Then I used the belt sander to even out the roughness and get straighter edges.  The points were still out at the old diameter, but I trimmed those to the right diameter with the bandsaw and sanded them smooth and straight.

The holes where the brackets attached were in the wrong place, so I just moved the brackets from positions 1, 3, and 5 to 2, 4, 6 (for those who immediately see benzene molecules when you see a hexagon).  I also used my stamping dies to mark 1 on the corresponding bracket and hexagon locations.

I rolled the interior with flat black paint Wednesday night, and the exterior with the first coat of white gloss paint this evening.

It doesn't look good yet.  After it dries tomorrow, I will sand it with some 400# paper, and apply a second coat.  Depending on how it comes out, I may sand again and apply a third coat, but at that point, if it isn't beautiful, it doesn't matter.  It will be dark most of the time.

All the holes (except for mounting) are drilled; once the final coat dries, it is ready for assembly.  Once assembled, I will determine the balance point, drill four holes for attaching it to the dovetail plate, epoxy in place two pieces of steel rod to prevent rocking on the saddle, and be ready to put it on the mount.

I may even be able to reuse the black flocked material from the existing upper cage for this.  I have gone out of my way to buy as many black oxide bolts and screws where something will be exposed on the inside of the tube.  Even then, I flat black them; the black oxide just means that if paint does scrape off, it is still pretty much black.

Terrorism Charges Filed in Boise

From May 16, 2013 Boise channel 6:

Fazliddin Kurbanov, 30, was arrested Thursday morning in Boise after a federal terrorism investigation.

Charges were filed Thursday afternoon in Boise and Salt Lake City against Kurbanov who was a United States citizen living in Boise currently.

The charges filed came after a federal grand jury in Boise returned a three-count indictment charging Kurbanov with one count of conspiracy to provide material support to a designated foreign terrorist organization. In addition, one count of conspiracy to provide material support to terrorists and one count of possessing a destructive device.

And in case you notice the byline on the report--yup, that's my son.

There Are Descriptions For Which No Comment Is Printable

I know not to trust everything that appears in Wikipedia, but a reader brought this to my attention, and it is rather like a contest to identify the number of despicable, wrong, horrible, evil things that can be done to a person, describing Brenda Spencer, who was one of the first mass murderers at a school in the modern era:

Spencer excelled in photography, winning first prize in a Humane Society competition.^[6] After her parents had separated, she lived with her father in virtual poverty; they slept on a single mattress on the living room floor. Police later found half empty alcohol bottles throughout the house. In 2001 she accused her father, Wallace Spencer, of having drunkenly subjected her to beatings and sexual abuse.^[7] He said the allegations were not true.^[8] Spencer is said to have self-identified herself as "having been gay from birth."^[9]

In early 1978, staff at a facility for problem pupils which Spencer had been referred to due to truancy, informed her parents that she was suicidal. In the summer Spencer was arrested for shooting out the windows of the Cleveland Elementary with a BB gun, and burglary. In December a psychiatric evaluation arranged by her probation officer recommended Spencer be admitted to a mental hospital due to her depressed state, but her father refused to give permission. For Christmas 1978 he gave her a Ruger 10/22 semi-automatic .22 caliber rifle with a telescopic sight and 500 rounds of ammunition.^[8][10] Spencer later said: "I asked for a radio and he bought me a gun." To the question as to why he might have done that, she answered: "I felt like he wanted me to kill myself."