Monday, June 28, 2010

Still alive - ingot trays

Sorry this posting has been late in coming... I've several previous projects to document, so the fact I haven't been in the shed is no excuse for not writing.
I'm currently putting the finishing touches on the design for the backgearing of my Taig lathe. I built and installed a leadscrew (with halfnuts) about 18 months ago, and the intent was always to add change-wheels and a spindle gear to drive it. I stopped working on that (temporarily) while I figured out how to drive the leadscrew, and get the speed ranges I was seeking - the backgearing evolved from that, and now it's practically completed in it's design (Got more parts for it today), I'll start construction of it this weekend.

It's kind of ironic when I think of it... I bought the lathe so I could build a hybrid rocket motor. I didn't start that because I wanted to bring the lathe up to spec with what I wanted. That meant I had to build other tools (furnace, etc), which created more needs, and on and on it goes. Now here I am, 10 years later, and the rocket motor still isn't built, and even if it was, I can't use it in this area.
Not that I regret the journey, but it is a long road which could have been considerably shorter (time wise) if I had the money to begin with. I guess it's part of the ME (model engineering - not narcissism) sickness that every project means more tools, jigs, projects, etc

Let me introduce you to one of the projects spawned out of another project, which was built to build another project...... The ingot trays from my furnace.

The furnace (another set of pages yet to come) can hold crucibles of up to A30 - in other words 30lbs (~14Kg) of molten aluminium at a time. In "smelting mode" it can melt as fast as it can be fed (I've gone as fast as 100lbs per 10 mins) limited only by how fast the molten aluminium can be captured.
To handle excess molten metal (from smelting or casting) I built up 2 ingot trays - one small, one large. Both are made from salvaged 3"x3"x1/4" angle iron.
The small tray has lengths of 12" making the finished ingots a triangle shape with sides of around 2.75" x 2.75" on the sides (4" across the long edge) and 12" long
The long tray is made of the same angle iron, but the lengths come out at 22" - this is too long for my crucibles, so I put a removable "breaker bar" in the tray to mold in a weakened break point in the longer ingots.

The photo above shows the removable bar in place in the large ingot tray - the bar is held in place by 2 1/2" pins which rest in the short lengths of pipe welded to the sides of the tray. (pipe visible at middle of front edge of tray)

The photo below shows how the bar has "wedges" welded to it which do not come to the bottom of the angle V, but leave a 1/2" gap at the bottom for the flow of molten aluminium. The sides come to within 1/16" of the side walls. Once cold, the resulting ingot can be snapped in half by a sharp rap on the concrete floor.

The photo above also shows the angled end on the LHS - the RHS is cut square, but the LHS has about a 15 degree slope to it to aid in the removal of the cooled ingots. The RUST is left in place to act as a "mold release" to prevent the aluminium from sticking to the tray.

The photo above shows the gaps mentioned at the bottom of the angle, and the slight gaps on the sides.  All the welding is done on the outside, so there is minor narrow gaps here and there in which aluminium will freeze, but these don't seem to cause issues, and the minor loss is negligible.

Moving the trays whilst hot proved to be harder than originally thought. Originally I used hooks and wire loops, but found the trays would catch on irregularities in the concrete floor, plus I worried about the heat from the trays causing issues with the concrete floor. My sand traps didn't make the movement of the trays any easier (to put it politely) so I looked at making wheels for the trays. What I came up with is shown below...

The photo above shows the "wheels" I fitted to the ingot trays. These are simply short bolts with their heads welded to the inside of the tray with the shanks pointing towards the middle of the tray. The bolt then had a number of wide washers slipped on the shaft, and then a nut wound on and captured with a wire threaded through a cross hole to stop the nut coming off too easily. Four of these were welded on each tray so the wheels worked along the long axis of the trays. The existing wire loops (handles) were retained, and the trays moved quite well over concrete, and sand traps.

As you can see, these trays don't need to be "babied"... they sit out in the weather, and are ready for use whenever they're needed since the rust helps release the ingots.
The height of the rays is so slight, they fit under the furnace drain hole to catch any crucible failures, (or smelting mode), and the wire loops are long enough to permit one tray to be lead in under the furnace without disturbing the other tray - making swapping from one tray to the other seamless, without spills.

All welding was done with my CIG stick welder, and the original cutting of the 3x3 angle iron was done at work on one of the bandsaws.

What would I do different if I built more? I'd probably make the trays only take 3 ingots at a time, instead of 4 to reduce weight. I'd make the ingots all the same size, instead of maximising use of salvaged metal. I'd learn how to do internal fillets so the trays didn't have small internal seams.

I've a few other projects already completed to document, so I'll try and get them done, even if the current projects aren't getting the progress I want them to have.

Monday, June 7, 2010

not forgotten, just flat out

I haven't written lately due to other demands on my time and energy.
Generally I'll try and publish based on the current projects, or projects I've already completed, and have documentation for.

Because of the various demands on my time and energy lately, I haven't done anything in the shed except some minor cleanup and salvage - hardly worth reporting yet, although what was salvaged will hopefully prove quite useful.

What's taken my time? - work, church, responding to emergency calls, some training, helping people with various problems, listening to people's problems, etc.
What's taken my energy? - pretty much as above - I actually find the emergency responding quite fulfilling - gives me a sense of making a difference. Listening to people's issues, and trying to help them overcome the same issues which have been in place for years and years can be quite draining.

So sorry about the rant - this post is more just a simple "I'm still alive, and I will post something of value soon" message... we all have problems - we all know people with problems.. some are there to be fixed, some to learn from, some to endure...

What's on the radar?
repair of the magnetic base indicator stand.
repair of a broken mitoyo vernier height guage
design, construction, and use of a taper turning attachment for a taig lathe
adaptation of taper turning attachment to profile copying attachment

I think that's about it - more plans than hours in the day - situation normal.