Saturday 8 September 2012

Marshmallow Forks

Tonight we will be having our Bonfire. This is a thing that we do on our property every now and then. The occasion is simply Spring, plus my smallest daughter has decided that we are going to have a bonfire.

Every year we get loads of branches from fallen trees, branches that were fed to the goats and are now stripped of bark as well as various other bits of woody detritus. So this will be the fuel for our bonfire.

Last time we had a bonfire, I made some long forks for roasting marshmallows and cocktail frankfurts. This year, I need more because my daughter has invited a few of her little friends over.

The marshmallow fork is a simple affair. Two strands of fencing wire woven together and then spread out at the end to form the tines. The other end is shoved into a wooden handle so that it doesn’t conduct heat down to delicate little hands.

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So I start with some fencing wire. This stuff is about 3mm thick. I take out two strands and then fix them into the bench vice.

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There is about 6” of wire in the jaws of the vice, this will be the tines of the fork. At the other end of the wire, I even the ends up and fit it into the chuck of an electric drill.

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The drill is then turned on slowly to twist the wire. When the twist is even along it’s length, the job is done.

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Next, the handles are done by cutting a 5” lengths from a broomstick. A hole is drilled in one end to take the twisted wire.

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I’ve wedged the twisted wire into the handle with a couple of extra bits of wire offcut. Later, I’ll pull the wire out and epoxy the wire into the handle properly.

At the other end of the wire the tines are simply bent into shape.

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The whole fork is about 1.25m in length, this gives enough distance from the fire to allow the child to roast a marshmallow or cocktail frank without incinerating.

Monday 3 September 2012

Cart Wheels continue

Yesterday I went back out to the workshop to check on the progress of the cart wheels from the Making Cart Wheels post. I wasn’t going to do much in the workshop yesterday, as it was Fathers Day, and my family had other plans for my time.

I removed the lathes from the jig and took a look at what I ended up with.

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It would appear that the jig and the glue have done their job pretty well. The glue has held the form nicely and the jig was able to clamp the lathes while the glue was curing.

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There is a straightening in the formed lathe toward the ends, but that is to be expected. The overall curve is good both in the arc of the wheel an in the straightness of the lathe from inside to outside. So overall, I would say that this application of the jig is successful.

There isn’t a lot that I can do with this piece in a practical way, so I am going to cut it up and use it on the jig. If I cut the “hoop” into pieces that are around 27cm, then I can use them to span two clamps. This will give me a piece that will help to clamp down the ends of the lathes when gluing a full 360o piece, by applying pressure at the join: between two clamps.

Next I’ll be buying some timber that is long enough to make lathes that will wrap all the way around the jig and then glue them with the ends offset (staggered), so that I don’t have all of the joins in the same place. Probably by doing two pieces with opposing joins and then the next piece at 60o from the first … something like that, so that no join will be in the same place as any other join. The idea is to improve the overall strength of the finished felloe. Of course, I have to cut the felloe up when it is glued, so this may be a little pointless … we’ll see.

Saturday 1 September 2012

Another play with the forge

After playing with the cart wheels, I had to wait for ages for the glue to cure, so I thought that I’d have a play with the forge.

I didn’t want to do anything dramatic, just get the forge up to a good heat and straighten some bent steel reinforcing rods that I have. The longer plan with the rods is to make them into forge tongs. To do that, they have to start out as straight stock.

I had loads of sawdust at hand, so I thought that I would also try out starting the forge using sawdust to see how that works. Apparently, this is a good way to start a forge fire. The particles of fuel simply disappear up the flu when they are ash and they take almost nothing to start.

Well, that’s partially true. When the sawdust burns, the charcoal particles form a crust over the fresh sawdust underneath and so only the top layer burns properly. When I turned the vacuum on to give it some air, that changed everything. The fire got started very well and was soon quite hot.

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I put the reo into the fire and started heating it. After about 15 minutes the fire was hot enough and I got to about 650 degrees centigrade for a 5 minute bake. As I was only bringing the fire up to bend the steel, this was hot enough for me. Also I didn’t want to use up too much fuel.

I still have loads of reo left to straighten, so I’ll be doing some more of that.

Making Cart Wheels

In the Wheel Jig post, I made a jig for making the wheel felloe (the outer part of the wheel). Now, after a hiatus of a couple of weeks where I had to attend to other responsibilities, I have come back to making cart wheels this weekend, Yay!

I managed to finagle some time to work out in the workshop.

The wheel jig has an outer diameter of 2.5 meters, so I needed some timber that was about 2.5 + the height of the felloe, as each lathe will increase the outer diameter of the wheel. I didn’t have anything that long, so I took a different approach … I can use the jig to make parts of the wheel, rather than the whole wheel all in one. When the felloe is made, it has to be cut up into 5 pieces so that the spokes can be fitted, so it isn’t as crazy an approach as it may first sound. The reason that I need to make 5 pieces is that the wheel will have 10 spokes, so one felloe attaches to two spokes … thus, 5 felloe pieces are needed. Anyway, enough of the theory and speculation … i want to play!

First, I took an old piece of pine that is 1.8m long and took it to the table saw to cut it up into 5mm thick lathes.

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I figured that lathes this thin would bend easily and not need to be steamed first. When the lathes are glued and bent, the glue will hold the timber in the shape of the jig.

The timber was cut on the thin side, so that the 5mm thin piece wouldn’t jam in between the slide and the blade. However, this meant that I was on the cut side of the wood. So extra care and attention has to be taken.

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When the lathe comes away from the stock, it is light and can easily ride the blade back and fly off the table at you … so be careful!

Next, I put a couple of lathes around the jig to make sure that they were going to bend OK and I would be able to bend and glue without steam.

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As predicted, the lathes were thin enough to be able to curve on this diameter without breaking. You can see that it is a fairly soft curve.

Actually, steam bending is not that hard. I made myself a steam chamber a while back and used it when I was making bentwood stuff. I will definitely be revisiting steam-bending on the goat cart project, so you can look forward to seeing the steam chamber in action at a later date.

Now that I was sure that the lathes were thin enough to bend without breaking, it was time to get the epoxy resin out and glue up. The glue that I am using is a 2 part epoxy that I bought for it’s cured flexibility. This is the glue that I was using to make laminated longbows with. When I put the longbows to breaking strain, it was always the timber that broke, not the glue. So this stuff is pretty good. Also, this epoxy is used in marine applications, so it is also waterproof.

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Mix the glue 1:1 in a disposable container. I bought a heap of plastic spoons, plastic cups and wooden stirrers for this purpose, I can make my epoxy mix and then just throw the fixings away without having to worry about contaminating the 2 part components.

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With the wooden stirrer, I spread a thin layer of the epoxy gel onto both lathes. The thinner the layer that you can apply the less squeeze out you will get. Also, applying the glue to both pieces makes for a much more reliable bond.

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Flipping the back piece forward over the front piece was the easiest way to match the two lathes. Don’t worry too much about how they match at this stage, the jig will apply the pressure needed to make the lathes work together.

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The two glued (but not cured) pieces were put around the jig … making it most of the way around. As I was putting the lathes into the jig I found that leaving the top bolt out was the only way to do this. Also, without the top bolt in place, the bar was able to be swung out of the way while bending the lathes around the jig. I went from the middle out to the edges so that the two lathes wouldn’t tend to spring apart when pressure was applied. When the lathes were in the jig and the bolts were tightened to finger tight, I then went to one end of the lathe and started to tighten and straighten the jig. There were some bends in the lathes and some points on my timber jig that were a bit uneven, so I had to put a shim between the jig and the lathe to tighten it up. It is also important to make sure that the bar is at a right angle to the wheel so that you don’t end up with twists in the felloe.

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All glued and tightened up, I just need to wait for the glue to cure. This takes about 24 hours, so tomorrow I will take the felloe off the jug and see if this experiment has worked the way I want it to. I need to add another 3 lathes to the felloe and then cut it up into pieces that will match into the spokes, but that is for later.

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