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.

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.

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 360^o 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Wheel Jig – Part 2

Cart Wheels Part I

Today I made some improvements to the wheel rim jig, I marked out the outer rim using a transom arm protractor. That is, a protractor that is made by fixing a batten to the centre of the circle and then rotating the batten through 360 degrees marking a line at the end of the arm. This gives you a circle. Then I cut along the line with a jigsaw to leave me with a circle. I still need to rasp down some high spots and fill some low spots, but it gives me the shape that I need.

I drew a line through the centre of the circle to give me the starting point. This line passes through the centre point in the circle, the line gives me 0^o and 180^o. From there, I marked off points at 36^o, 72^o, 108^o, 144^o and back to 180^o. As the circle is divided by an even number, I can simply draw a line from each of these five points to the opposite side of the circle to give me 10 equal divisions.

Next, I marked out a point on each of the division lines about 1 and a half inches back (2.5cm) from the perimeter and drilled holes through for the jig clamps. Turn the jig over and clean up the slight tear-out from the drill and, presto, a wheel rim jig is made.

You should be able to draw a straight line between each opposing pair of jigs and they should all meet in the centre of the circle.

I may need to fix another layer of fence palings to the jig to make it thick enough. Otherwise there will be a tendency for the laths to warp because one side or the other of the clamp will be off-set.

 

The threaded bar that is used in the clamp has been left quite long so that I can have enough clamp to make a rim up to about 15cm.

In the top photograph, I have put the topmost clamp all the way through and brought the next two clamps all the way forward so that I can use the clamp as a hanger to hang the clamp off the ground. I have also got a hole drilled through that was at 45^o from the first hole. This will be where I can hang the jig up in my workshop. Hanging the jig means that I can have bench-space cleared up while I wait for the epoxy to cure. The epoxy that I will be using is a two-part marine epoxy. This epoxy has a little bit more flexibility in it than other woodworking epoxies and the wheels will take a bit of bumping around when under load.

One of the reasons that I have made this jig with 10 jig clamps is that I intend to make my wheels with 10 spokes. The clamps also provide me with a guide for making the spokes.

Anyway, that’s it for today. I hope you enjoyed it.

Read Part I here

Making Cart Wheels

Cart Wheels Part II

I need to make some cart wheels for my planned goat cart. Some time ago, I had some jig clamps made (to my design) by a local engineering company, they are simply a pair of round bar of equal size and diameter. The bottom piece is tapped so that a bolt can be passed through it, while the top piece has a hole for the bolt to pass through. When the bolts (2) are tightened, the two pieces are brought together.

The idea is that you have a timber form and you drill a hole through the form and pass the tapped clamp piece through the hole. The work piece that needs to be clamped is then put on the form and the top piece of the clamp is added with the bolts (I have fixed nyloc nuts to the ends of the threaded rod to make my bolts). I have 10 of these clamps.

On another project that I was working on, I made some crude timber wheels (using fence palings).

The wheel was only being used in a “proof-of-concept” so I never actually used the wheel. The next part is to mark up the wheel and put in the holes for the jig clamps. There are 10 clamps, so 10 holes around 360o means that they will be at 36^o from each other … well I can work with that. First, drill one hole and put the clamp in.

Here you can see what I mean, one part of the clamp is fixed in the jig, while the other is able to move in and out by turning the bolts top and bottom. The only real drawback with this design is that it is easy for the piece to skew, so I have to be careful when tightening the bolts.

So, to prove the concept for you, here is a piece of Huon pine that I cut from a larger piece, this is called a lath. I cut many of these laths to make laminated longbows from (another story for another time).

I’ve placed another jig clamp at 45^o (because it is easier to measure with what I had at hand. I will put the rest of the clamps at 36^o).

You can see how the clamps are pulling the Huon pine in to the shape of the former.

For this to work properly, I will need to steam the lath (and the lath will need to be much longer). I will be cutting many more laths on my table saw from Tasmanian Oak since that’s a fairly easily obtained timber in the widths and lengths that I need. I also need to refine the timber wheel that I am using as a form. It is not a perfect circle. For that I need to set up my router on a swing arm from the centre of the wheel. I’ll use a straight cut router bit so that the wheel is cut cleanly from the centre.

The lath will be set on the forming jig while pliant from steaming and then taken off the former. When the lath has cured, I will then use epoxy to glue it to another lath until I have a wheel rim that is approximately as high as it is wide.

In between laminations, I will leave the progressing wheel rim on the jig as the next lath will need to be formed to the wheel rim as it goes.

The above lath is about 3mm thick and 30mm wide, so I’d need about 10 laths to make a wheel. Also, each lath needs to be about 3mm longer than the previous one to account for the increase in thickness.

So, there you go. Apart from a bit of tidying up in the workshop that was my playing around in the workshop.

Tomorrow I have a Goat Judging course to attend, so I won’t be doing any more work on this project until Sunday.