Friday, 27 July 2012

Making Cart Wheels

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 36o 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 45o (because it is easier to measure with what I had at hand. I will put the rest of the clamps at 36o).

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.

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