Wednesday, 23 October 2013

The Halloween Machine ...

Recently we've been showing the kids how things work, and how things are made and I was trying to explain to the kids what cams are, and how they are used in engines and in other types of machinery, I wasn't convinced I was explaining in a way that they would understand.

I've worked with machinery/engines of various sorts since I was 15 and because of that I sometimes forget that I might need to simplify things a little, so we built The Halloween Machine, which uses cams to animate a Halloween type scene.

It's made of wood, and although it's not very precise I have taken some care with it, other wise it wouldn't work properly, there's a video of it in action at the end of this, it shows it working in the dark and in the light so you can see how the cams work.

Here's what it looks like in the dark and back lit -


It has to be said I got a little carried away with it, but it turned out well, and it's a good demonstration of how cams can be used to turn rotary motion into liner motion, this is basically how the valves in a car engine work, they are operated by cams, these open and close the exhaust and air inlet valves.

The first thing I did was to make a cam template, to do this I marked out the centre of a piece of wood and then using a hole saw I marked out a slight circle on the wood, next I marked lines either side of the circle and then marked lines from each edge of the circle, then I cut out the shape on my scroll saw.

Here's a few pictures to show you what I did -

Centre line marked out.

Circle and hole made with hole saw.

Lines marked either side of circle.

Basic cam shape sorted.

Once the template was done all I needed to do to make the other cams was to drill a hole big enough for the dowel I used as a cam shaft (I used 9mm dowel) and with the template on the dowel I just pushed it into the hole and drew round it.

Here's how - 

Off cuts come in handy.

Just need to draw round it.

I originally wanted 3 cams, but ended up with 6 small cams for the bats and a larger one for the witch (see what I mean about getting carried away?) so once I'd got enough cams for the bats I needed to make them all the same size, so I put all 6 cams on a piece of dowel and then sanded them until they were all the same.

Like so - 

Cams ready for sanding.

Seems I wasn't very careful when I cut them out.

All sanded and virtually identical.

Next I drilled a small hole in each cam, the reason for this is because once I had the cams where I wanted them on the shaft I didn't want the moving about, so once they were right I used the holes I'd already drilled as a guide and drilled into the shaft, then used a small peg to lock them in place.

Locking holes drilled - 

Cams done.

On to the box to hold the cam shaft, this is basically 4 bits of wood with a hole drilled in each end for the cam shaft to fit through.

Making the box - 

The 4 parts ready cut.

Centre of each end marked.

Fixing holes and cam shaft holes drilled.

Box finished.

The box that holds the cam shaft and the bat and witch figures is really simple to make, once I had it fixed together I marked out and drilled 7 holes along one of the longer sides, these holes are where the posts that hold the witch and bats will sit, I made the holes 10mm and the posts that hold the bats and the witch are made from 9mm dowel.

Post holes marked and drilled - 

post holes marked out.

Post holes drilled.

Next I cut out the bat shapes, these I printed out and stuck to the wood I used, I did the same for the witch, but forgot to take pictures of that.

Bat shapes ready to be cut out -

Simple bat shapes.

The kids painted the bats using a water based black enamel paint, and the witch and the scene were also painted in the same paint, the graveyard and village scene are cut out from a thin piece of pine.

Painting - 

They did an excellent job.

And here's the finished article - 

Ready for action.

Here's a close up of the cams - 

The cam on the left is the one that drives the witch.

You can see that I've added a little wooden plate to the end of each post, this stops the whole thing jamming up, and you can also just about make out that the cam on the left has 2 metal parts either side of it, I had to add these to stop the post the witch sits on from turning round, she had a tendency to face the wrong way, the cam that drives the witch is also a different shape as we wanted her to have a different movement from the bats, which it has to be said are slightly erratic in their movements.

Here's a close up of those metal pegs, which are just bits of wire - 

A simple solution.

I also made a handle so that the cam shaft can be easily turned, I made this from a circle of wood I cut out with a large hole saw, then I drilled another hole in it and added a piece of dowel, and then I made a collar for the dowel.

The handle - 

Circle of wood.

Finished handle.

I haven't included all of the steps involved in building this, but I plan to make another one, all be it a little less complicated to show how to make one, I think the kids get the concept of cams and how they work, and if not, well it's a fun thing to mess about with.

Here's the video of it in action, the first video is a little dark, we had some back lighting issues (mainly the lack of it) hopefully this should give you an idea of how it works.

The Halloween Machine - 

Thanks for reading.

Homemade Thursday

Saturday, 12 October 2013

Kinetic ghosts ... ...

Another Halloween themed toy, this one however incorporates a bit of physics, it's basically a Halloween take on the old woodpecker toy, the one that slides down a pole when you move it.

Here's a picture of the ones I made -

Look familiar ?

These toys have been around for many years, and more traditionally they were wood peckers, but seeing as it's coming up to Halloween I thought I'd see if ghosts would work seeing as the principle is the same.

All you need to make these are some bits of wood and a spring, one from a pen would do, but you can buy packs of springs from hardware and diy shops, and it's always handy to have a variety of springs lying about.

Ingredients - 

Few bits of wood and a spring.

Basically you need a piece of wood for the base, a small piece of wood for the ghost, or you could make some other shape (a pac man shape for example) a piece of thin dowel for the pole (I use 6mm dowel) and another piece of dowel to make the collar (I used 15mm dowel)
Dowel in a variety of lengths can be picked up for around 99p for a short length from most diy shops, and lastly a spring, like the ones you get in pens, but again springs can be bought in packs.

Okay, in the piece of wood you use as a base you want to find the centre, if you have a square / rectangle piece of wood draw lines from each corner diagonally and this will give you the centre of the wood, then measure up from this point about 2 or 3cm and drill a hole just big enough for the dowel, so if you use 6mm dowel use a 6mm drill bit, you may need to sand the end of the dowel a little to get it in the hole, and use a spot of wood glue (pva) to make sure it doesn't come out.

Finding the centre -

Ignore the other marks, it was scrap bit of wood.

You can just make out where I made the mark for the dowel, just above the centre mark.

Hole drilled and wood sanded to get rid of the pencil marks - 

Next the dowel and a drop of glue.

Okay so once you've drilled the hole go ahead and stick the dowel into it, the length of the dowel can be what ever you want, I made mine 22cm in length, this allows for the bit that is stuck into the base.

So you should have something that looks like this - 

That was easy, what's next ?

Now the next part is making the collar, this will be the part that the spring attaches to, I used a bit of dowel and I drilled a small hole in the side first for the spring to fit in, then I drilled a 6mm hole in it for where it will sit on the pole.

It's best to use something to hold the wood still while drilling, and if you can get hold of one use a post drill, or a vice of some sort to hold the wood while you drill it, one it's safer and two your holes will be more accurate.

Holes drilled, one at a right angle to the other - 

Reading for fine tuning.

Before you glue the spring into the hole you made for it you'll want to check to see how the collar fits on the upright piece of dowel, I used a 6mm drill bit which meant I had to sand the inside of the collar a little to get it onto the dowel, stop sanding once the collar will go onto the dowel easily and will slide all the way down if you let it go, if it's too loose it will just fall straight down when you try to use it with the spring and ghost attached, if it's too tight it won't move at all.

This is the collar, you can see where the holes need to go - 

Bit blurry but you get the idea.

Next the ghost, this was the easiest part, I took a roughly cut small block of wood and using a couple of triangular needle files I made grooves in one end of it.

Like so - 

Needles files are cheap and handy for wood working.

Then the next thing to do is drill a hole in one side of the ghost shape, again use the same sized drill bit as you used for the hole in the collar where the spring will go, I used a 5mm drill bit as my spring was roughly 5mm.

Ghost finished, just needs a paint job - 

Kind of pac-man esque.

You can see the hole where the spring will go, the next step is to fix the spring to the collar and the ghost shape, I'd recommend a glue gun, or some kind of quick drying glue, and when you do glue it make sure to keep everything as in line as possible.

Assembly complete - 

Ready for some decoration.

As I'm going for a Halloween theme I painted them white, and gave one googly eyes, and the other I just coloured in with a black marker pen, I've used the same water based white enamel paint on these as I used on the jumping jacks.

All done, I could have painted the base and pole, but decided not to - 

Very spooky, well maybe not.

I've included a short video of them in action at the end of this post, but first a little bit on how these work, see it's all to do with friction and gravity and the momentum of the spring.

The spring and the weight (in this case a ghost) cause the collar to sit at an angle on the pole, this causes friction and stops it from falling, which is why you don't want to make the hole in the collar too big, if you did it would just drop, due to very low friction.

So how does it move down the pole ? well when you set it off, by making the ghost go up and down on the spring this causes the collar to move as well, and there's a point where the collar is in line with the pole, then gravity makes it fall a short way. 

So the collar rocks back and fourth in such a way that it will align with the pole and gravity makes it fall, the weight (ghost) causes the spring to rock one way and then the other, and in turn this causes the collar to rock one way and then the other and the inertia of the weight (ghost) keeps the spring moving.

In theory if you could some how keep the pole on a loop this would run forever once you started it off, it's because it has a base that it stops, if you made the pole say 100 metres high this would in theory run until it hit the bottom.

Here's a very rough gif animation of what's going on - 

The red stars show where friction occurs.

You can see in the animation where the collar lines up with the pole, and gravity then makes it fall a short way, you can always search online for 'Kinetic woodpecker toy' which will yield much better descriptions of how this works than mine.

And if you feel like making something similar to this (it works on the same principles) then have a look here - Oscillating Woodpecker (opens in new window)

And here's the video of these working -

Thanks for reading.

Homemade Thursday

Thursday, 10 October 2013

Wooden jumping jacks ... ...

It's nearly Halloween, and as usual we are trying to make things for the house, and this year I've decided to make two lots of Halloween themed things, the first of which are wooden jumping jacks, I made a skeleton and a more simple ghost version, both work on exactly the same principal.

Now these are toys that can be traced back thousands of years, and they were a favourite in the 1700's of the French nobility who called them 'pantins' and have been known with the rather colourful name of 'quockerwodger' they are usually made of card, but as we intend to keep these for next year I've made them from thin plywood, but this does require the use of various tools.

Here's the skeleton -

Very creepy.

Basically it's a type of puppet, you operate it by pulling the string to make it's arms and legs move up wards, there's a video at the end of this which shows them in action.

I basically printed out a skeleton template, there are loads to choose from online and once I'd cut it out I stuck it to a scrap piece of plywood with a glue stick.

Template all cut out -

Before I stuck it down I cut out the black parts.

Template stuck down -

On to the cutting.

I cut out the various parts in my scroll saw, which gave a me a chance to use my new spiral blades, they are very good, if you have a scroll saw get some spiral blades.

Once I had it all cut out I then set about adding some detail to the bones, I basically used a carving bit in my multi tool to carve out where I'd remove the black parts of the template.

Carving bit -

These are great for wood working.

Skeleton cut out and carved - 

I could have just left it, but it adds a bit more depth to the skeleton.

One I'd finished cutting and carving it was time for a coat of paint, I used a white water based enamel paint, which you can buy from diy type shops, it's good stuff easy to use, dries quickly and you can use water to clean brushes, I've used it before on the miniature furniture I made for my daughters dolls house, and for the black details I used a black permanent marker.

Painting and details done - 

Next up wiring it all together.

Now fixing it was easy, on the template I used there where points already marked out where the joints are, so I just drilled a hole at each point and then using some thin wire I wired it all together.

Wire and pliers - 

I used thin garden wire, but string would have also worked.

To make the arms and legs move I drilled holes in each shoulder and on each side of the pelvis, then I used small tack to join the arms and legs to the body, I bent the ends of the tacks over to make sure the arms and legs don't fall off, then it was on to the rigging, the bit that makes it all move.

All wired up - 

Could do with a good meal if you ask me.

Now this is the bit that makes it all move, and it's really simple, and that's what makes it so great, the fact that it's so easy to do, it's just string.

The rigging - 

Simple but effective.

As you can see the string joins the arms and legs together, then a piece of string is connected to the middle of each bit, the idea being that when you pull down on the central piece of string it pulls the string down and this makes the arms and legs go up, making it look like the puppet is jumping, it doesn't really get much easier than that.

Then all I did was to make a bead to go on the end of the string to make it easier to pull, and that was it, the ghost you see at the end of video is made in exactly the same way, it just has less moving parts.

The finished skeleton - 

Reading for jumping.

Here's a short video of them both in action - 

Although I've made ours from wood you can make these from card, you could use paper fasteners to join it all together and for the rigging you can use string or cotton, it's a great project for kids to try.

Thanks for reading.

Homemade Thursday