Hephaestus -- a mini-furnace

I really should be posting on the garden, which is my main preoccupation at this time. But I'll do that later. Meanwhile, I would like to tell you about my mini-furnace. I did not invent this thing; I got it straight out of the internet. (Google on "soup can furnace".)

One of the problems with doing mini-blacksmithing as I do is that it takes quite a long time to heat up the work. Maybe five minutes to red-hot. After that it goes faster. Still, it is time and gas wasted. You are heating the atmosphere as well as your work. So I built Hephaestus, the tin can furnace.

 It could not be simpler. A tin can. In my case a roast beef hash can. Drill three holes. Mount it on some L-brackets. Fill the tin can with equal parts of sand and plaster of paris. Use a former (I used a broomstick and neglected to spray it with Pam) for the hole in the middle. But do oil your former. Any oil will do. The filler sets up in five minutes. I had to drill it out and then burn off the remaining broomstick remnants.Silly me.

You note the propane torch at the left. This fits in a hole you drill in the can. A spreader tip works better than a pencil tip. Fire up the torch and stick it in. It is amazing. It goes from zero to orange in under a minute! That is, you stick your steel piece into the furnace and light off. One minute later start forging. Amazing! Do use vise-grips on your piece -- it gets very hot indeed.

This thing really will save time and propane. But now it's time to garden, and I have no spare time. Next post I'll get into that.

Spring Fling with the Trebuchet

In the middle ages, in spite of all the nonsense in the romantic novels, most warfare revolved around sieges. Offense and defense evolved in parallel. The castles got thicker walls; and to knock them down the trebuchet was invented. There is a lot of material on the net about trebuchets.

So I got tired of  working on my picture frames and built a model of a trebuchet out of scrap wood.

As you can see, it is a lever pivoted on a stand. A heavy weight is attached to the short end. A sling is attached to the long arm. In the picture the weight is propped up by a stick. A projectile, in my case a vaguely ball-shaped piece of modeling clay, is put in the sling.  When the stick is knocked out, the weight falls, of course, this impels the projectile. So far I can sling the ball a couple meters, but I have been reading up on this and I think I can improve it.

Lots of variables here. Quite a complicated simple-looking device. Medieval trebuchets could throw 100 Kg a distance of 100 meters -- at least, the modern reproductions can do this. One monster I saw on YouTube (made out of steel) can actually fling a  compact car!

Spring is here and I have the garden to do; I think trebuchet tuning will have to wait.

Napoleon, again

Napoleon returned shortly after I did the post on him. He decided that the spot right beside my bedroom was the ideal spot for his moosely nap. He parked himself right next to my bedroom window.

Fortunately I walked in time to get a picture. He was literally a meter away. Quite unperturbed by the pesky humans. Unfortunately the camera recorded the screen on the window, hence the weird effect.

Moose are nocturnal animals. During the day they nap. I'm glad Napoleon did not feel threatened at Chalupy.

Framed!

Asy ou know I have been struggling with the picture frame. The carving was the easy part. The hard part is doing the miters. My shooting jig is now very accurate. But it has a real problem. The plane follows the miter. If this is not exactly 45 deg then the plane tends to follow the (erroneous) angle. And one degree is far too much error. I tried a commercial miter box and it had far too much slop. Well, desperate situations demand desperate measures. I resorted to Cecil B. de Mille.

 I packed up the frame pieces on home-made parallels. This is so that you don't try to mill your priceless mill table along with the wood. I stuck my faithful 3 mm carbide end mill in the chuck. I then set the wood at 45 deg with the X-axis of the mill; that goes right to left in the picture. I tried the Y axis (90 deg from interfere X) but I did not have enough travel. Setting this thing up was a bear.  The clamps interfere with measurement. And my protractors keep slipping their settings.  In fact the clamps can slip too.  I finally overcame these difficulties. A whole day's work to do all the pieces. They were badly off; a degree is far too much.  Only problem is that the end mill is ever so slightly too short. Had to make several passes, varying the depth of cut (Z-axis). The part nearest to the left-side clamp is a bit too thick for the end mill. In this business a tenth mm a gross error.

When I clamped it up (in the homemade jig) there were some errors. I went back and "shot" the corners. See previous posts. It now fits quite well. Not absolute perfection. But not bad for a first frame.

Now I am putting some bamboo skewers (at bottom left) through the corners. Commercial framers use corrugated knock-in steel pieces; but I don't have any and am not sure I'd use them if I did. A miter joint is a very weak joint (if indeed it is a joint) and it needs reinforcement. I made a drill jig to make sure the holes went where I wanted them. I couldn't do this on the drill press; the frame is too big for my little drill press. Must use a hand drill, a very imprecise tool. The drill jig is at lower right corner in the picture above.

When I finish this operation I will plane off the pegs and give it to John. He has far more paintings than frames! I have learned a lot from this experience. Unlike other woodwork things, a miter jont is unforgiving. Get it wrong, never get it straight again. Next time I will do the joints before carving anything at all.

I must make a miter box. But to do so I must find some aluminum channel. Easy, you say. Go to Home Depot/Lowes.  Not so in Alaska. Well, eventually something will turn up.

Napoleon invades Russia! Er, Chalupy.

Yesterday I went skiing, as I do every day the snow is decent. It has been a very bad winter for skiing and I take every opportunity I can to do so. I start out with my "warmup track" around the house. When I started on my second lap around the track, I heard this noise. It sounded something like "snap, crackle, pop" and it was coming from the tractor, or so I thought. A close examination of said machine revealed nothing. What's this? I skied a few more meters and behold! A large moose hiding behind the tractor, chowing down on alder or birch. Well, he wasn't bothering me, so I didn't bother him either. You are well advised not to intefere with moose. They may be (and are) placid creatures, but if they are feeling threatened they can trample you to death.

So later John and Fluffy returned from a Safari to Wasilla, and reported that the moose was napping behind the tractor. Nap? Nap? Napoleon, said I. That's his name. I think it's a he; if it were a lady it would probably have offspring. OK, put moose out of mind.

But this morning when I went out to do something or other there was something not quite right. There was something lurking around Brutus, the Ford Explorer that J&F drive.

 What is this? Looks like a moose to me. Awfully close to the house, too. After some effort we got closer and found a moose chewing its cud. Moose, in case you did not know, are ruminants.

At this point Napoleon started making distressed noises. Far be it from me to distress Napoleon. I backed off.

Furthermore the beast had been licking  Brutus. John accuses Napoleon. He says  he is having an illicit affair with Brutus. I think, however, that it is a salt infatuation. Moose love salt. Maybe I should put out a salt block. Can't put out hay. Moose cannot digest hay.

Anyway, I went to the bathroom window and got the following priceless shot:

When I went skiing today, Napoleon  was ensconced behind Lysander, my tractor. When I went by, he was sort of ruffled so I went elsewhere. When inspected at 6PM tonight, by John, he was at the extreme end of the driveway eating up the twigs. Amazing creatures. And Brutus definitely needs a bath. Not every Ford Exporer can boast that it has been licked by a moose.

The jig is up

My picture frame did not fit really nicely. It had its gaps. Now, I am used to furniture. If furniture does not fit well I tweak it a little. With picture frames it is another thing completely. As I said, when I laid this thing out I had very primitive tools.  But when I was a lowly Officer Candidate in the U.S. Air Force there were three possible answers to any question: yes sir, no sir, no excuse sir!  In this case the correct answer is the third -- no excuse, sir. The frame did not fit.

Fortunately it came to me that I was neglecting a VIT (very important tool), namely the miter gauge (Britons read mitre gauge) that came with the bandsaw. This is just a very large protractor.

Beacuse it is so large, it is much more accurate than most store-bought protractors. I have a reasonably accurate shop protractor and I used that to lay out my shooting jig. But inexplicably the left side was off. By at least two degrees. When you are doing picture frames two degrees is suicide; it will never line up.  The right side was perfect; again inexplicably. There was nothing for it but to rebuild the jig. So I got a fresh piece of wood. Now I hate power tools, but I used the bandsaw (and its miter gauge) to get it right. No use introducing extra errors of hand wobble at this point.

Here is the new jig in action:

Ah, but there is more. All the lengths, inside and outside, must match. Elementary, my Dear Watson (which Sherlock Holmes never said. He said "elementary" any number of times; he said "my dear Watson" even more. Never did he put the two together). So we have a lot of fiddling (because it wasn't cut right in the first place)  to do and it is sometimes frustrating.  The shooting jig has no fine adjustment. I am enough  of a machinist to resent this! Version 2.0 will overcome all these faults. Darned if I know how yet.

But on to successes. The carving process left gouge marks all over the place. So I ground up a form tool out of a piece of old hacksaw blade. I collect old hacksaw blades for just such a purpose. I made  a paper template, ground the thing on a Dremel tool, and adjusted as I went along.

The left end of the tool rides on the straight edge of the molding. The tool shapes the molding. I use it by hand, although I could cobble up a scratch stock (q.g) to do it. By a remarkable piece of serendipity the other end of the tool, a conventional factory rounded edge, is just right to smooth out the middle. So we make progress. Very slowly, to be sure.

Shoot that frame!

Usually one thinks of "shooting" as pointing a gun and pulling the trigger. But this word has a meaning that probably goes back to the Romans. Maybe they made picture frames too, although I doubt that any are left. Most of our extant frames date back to the Renaissance. Those people really did shoot frames. So what do I mean by "shooting a frame?"

When you make a picture frame (think of the last frame you saw, or have hanging on your wall) with miterered corners,  there are three requirements. One of them is that the pieces should be cut at exactly 45 degrees. The second is that the  dimensions of the pieces should be exactly the same. Especially the inside dimensions. The third is that the mating surfaces should be as smooth as you can possibly make them. Otherwise it looks, well, amateur.The big boys -- the pros -- use a guillotine-like affair. This is beyond my means. A miter joint is a really weak joint, you would not like to use it for furniture. For picture frames it works all right. Just.

You could concievably cut miters (Britons read mitres) at any old angle. Say 30 deg. But then the mating part must be cut at 60 deg because the frame is rectangular. The jigs required to get this straight would be quite complex, unless you resort to CNC cut frames. So most of us stick to 45 deg, half the right angle.  I did too.

The crucial step is to build a shooting jig.  Here it is.

It is basically a scrap board clamped in my woodworking vise, which is attached permanently to my dining room table. I have a very small house; everything is multi-purpose, especially in winter. It is really a very simple jig, but it took me all morning to tune it. There is a triangular piece screwed on to the board.  There is a rabbet (Britons read "rebate" which is where our corruption comes from) and the angle between the rabbet and both sides of the triangle is 45 deg as accurately as I can measure it. It took quite a lot of planing (and a very accurate protractor) to get the angles right.  In the rabbet slides my trusty Veritas rabbet plane. Expensive. Worth every cent of it. My frame member is clamped (you can just see the clamp upper left) to the jig. When you plane across, left to right, you shave just a tad -- 0.1mm at most -- of the approximate saw-cut miter. This is called shooting the miter. Adjusting this thing is very difficult. Takes patience. But by George, your miters will be at 45 deg. This is a very old-school technique. Most people use CNC equipment for this nowadays, I suppose.But shooting makes a glass-smooth surface, especially with the Veritas plane which is a low-angle plane.

When I was all through with the shoot, I had a big gap in my frame. Surprise! My dimensions were way off. One piece was a full 6 mm off the other, which is suspiciously close to 1/4". When I laid this out at my daughter's place, I had very primitive layout tools so I suspect I made a mistake because I really cannot deal with RGU. So now I have to take 6mm off one side. I got down to 3mm and then decided to take a break and go back to machining my steady rest. Next post.