We Have Lift Off!

Finally I can begin my favourite part of product and furniture design, the physical making of my piece. I will try and document every step of the making process with photographs and annotations -

First I got a huge sheet of 12mm thick MDF wood and got one of the technicians to cut it into 300mm wide lengths

Next using a large compass I draw out 5 x 200mm diameter circles along each length

Using the bandsaw I carefully cut out the five circles, from some quick maths I found

I would need 20 of these 200mm diameter circles

I then draw and cut out the smaller 140mm

diameter circles for the indents of the central

column

Next I wanted to attach the discs together to start the layering up of the central column, so first I covered the top face of the bottom disc with PVA glue

I then got another disc with the same diameter

and carefully placed it directly on top of the first disc

I then repeated this process with PVA for a third layer

Then using an air pressure nail gun I nailed the three layers together with 30mm nails

Now with the three layers glued and nailed together I can make them completely identical and also smooth. To do this I used the belt sander and simply rotated the discs as I pushed it into the sand paper

This is the piece one sanded to the same size, I am very pleased with the overall look of the layers sandwiched together and sanded smooth

A whole day later I had managed to to glue, nail and sand all the varying layers of the central column, this is it with all the segments in place but not yet attached together. It is actually thinner than I had originally pictured it but the maths all made sense. Despite this I do really like the overall shape of it (in terms of the aesthetics)

For the best look and so the mechanism works smoothly all the discs must line up perfectly like in the previous photo. So on the bottom face of the top thickest disc I drew on a circle with a 140mm diameter central to the larger 200mm disc

Then like before I smeared the bottom of the thinner three layered disc next down on the column

Once the thinner disc had been placed in the circle I draw out and left long enough for the PVA to dry. I hammered in two flathead 50mm long nail, joining the two segments together strongly

While the glue was still drying and to avoid a gap between the two segments I clamped the them together with two G-clamps just incase. Although time consuming this will ensure a nice clean cut finish to the layers on the column

I then repeated this process of gluing the underside of the next segment in the column and then once dried nailed them together, as you can see I had to make sure that the two larger discs lined up perfectly before nailing them

Then I added another identical small disc to the growing central column, this one is harder because I its hard to judge when is directly above the identical disc two segments down. So like with the other small segment I drew out the right sized circle on the face below it so make it central

Continuing with the layering of the segments, I added another large disc. Below is a quick video of the column up to this point spinning, giving a better idea of the piece in 3D - enjoy!

All that is left to do once I had glued and nailed the large segment in place and waited for it dry is turn it the right way up. Comparing this photograph to the first one where I just stacked them up to get an impression, I can't see any variation and I'm happy with the positionally of each segment

Using two Sash Clamps, I was able to easily clamp the whole column, tightening it up to close any gaps that may have formed between the segments

Whilst my column is clamped tight, I started on the seat top. I had already layered up four 9mm thick layers of MDF squares 400mm in width and hight. Mainly for aesthetics reasons I want curve of the corners of the seat top with a nice curve so using a ruler and compass I draw on the curves

This is the newly cut seat top, I think it looks a lot better and more in keeping with the pod like form of the trap

Now it is time to join the column and seat top together to form the seat that the victim will sit on. So again, I smeared the top of the column with PVA glue

Once I had marked out the centre of the underside of the seat top and draw a circle using a compass with a diameter of 200mm (same as the width of the column). I carefully placed the column in place and left the glue to dry. Due to the thickness of the seat top and so not to running the look of the seat top surface I didn't worry with nails

This is the finished seat component of my chair trap

I have finished the first part of the making of my chair trap and am very happy with the progress. The next part will really test my making skills and the trap design

The first component of the trapping mechanism is measuring the cutting the circular base, into which the cog mechanisms will be rooted. So using a varies thicknesses of MDF I layered the base up to 23mm (a sufficient depth for a strong joint) and a diameter of 500mm

Next I had the important task of drawing out the shape of the cog/arm combination piece, that will make or break this design. Fortunately the my preliminary work really helped. I had a very good idea of what the arms and cogs would look like from my experiment with the 2D model (the video in the Helping 3D With 2D post), so that the cogs will rotate perfectly within the cuts in the central column and the arms come up the right height to trap the victim round the neck. The reason the photo may look a bit odd is that it is actually 3 photos that I merged together in Photoshop because my camera couldn't get the whole drawing in one image (with enough definition)

Its hard to see from the image but I have slightly altered the outside arc of the curve. I realised that when the trap is open and the arms and open and resting on the floor, they will be touching at a single point and won't look aesthetically right. So at 90° to the pivoting point at the centre of the rotating cogs to the right side of the arch, I drew a vertical line. So basically the outside arc will have a vertical cut in it but the inside arc of the curve will remain the same, all will be made clear in the next image of the piece cut out

See the flat face on the outside arc of the curve, that should in theory sit nicely on the surface of the ground

Holding the piece up against the column reassures me as it looks just like the scale drawing a did (also shown in theHelping 3D With 2D post)

Using the cutout as a template I set about drawing out and cutting the 5 real arms and cogs out of much thicker 18mm thick MDF

The next step is to drill a 5mm hole in centre of each of the cogs, the reason for 5mm is that thats the thickest copper plated steel rod that the workshop stock and also its big enough hold a chunky rod but not too large to compromise the strength of the cog

For my real chair, I decided not to use the copper plated steel rods for the uprights of the Croquet as I did for my two models because this proved too weak and wobbly, so instead went for 18mm thick wooden dowel for the uprights. Bearing in mind that they are going to be rooted in the 23mm thick base I cut them to 200mm

With the same 5mm drill bit I drilled a hole at exactly 180mm from the base of the dowel, this will mean the hole will be 160mm up the side of the central column that sits on top of the base (this is shown in my drawing) - it is very important that this hole is central to the dowel and goes through the dowel straight and not at an angle

Now it is a matter of assembling, on a length of 5mm thick copper plated steel rod, first put on one of the dowel uprights, then a few washers (to aid the movement of the cog), then the actual cog/arm piece, then a few more washers and finally the second dowel upright. And you have your strong croquet hoop

Once I had made all 5 arms with their croquet hoop supports I needed to work out where I want them to be positioned on my base in relation to the central column and the person in the chair. In turns of ergonomics there will have to be a sufficient width between the two front arms for the width of the persons legs, this resulted in the two arms being 100° from the centre point of the base. So all I have to do is divide the rest of the circle (260°) into four equal parts

260/4 = 65°

Here is a drawing to show the divide better. The additional advantage to having 5 arms is that I have one directly at the back of the victim sitting in the chair (a possible weak point to the trap)

Because all the cogs are the same size and interact with the same edge of the central column, they will need to be the same distance from the column. So the legs of all the croquet hoop will be on the circumference of a larger circle with the same centre point as the central column. Knowing this I can measure the distance from the side of the column to the centre of the dowel legs when the legs are perfectly vertical and the cogs fit perfectly into the relevant indent of the column. In this photograph you can faintly see the column circle above the legs larger circle, onto which I placed and drew round the dowel legs of the finished croquet hoops

The next job was to drill the holes into the base with a 18mm drill bit

Here are the 10 holes drilled into the base

Here you can see one of the cog/arms rooted firmly into the base due to the 18mm thick dowel hammered into 18mm diameter holes in the base

This is the base with all five arms and cogs in position, all facing towards the centre and with enough place in the middle for the column

I hadn't predicted the trap being this large when open!

This is trap chair shut with the central column in the in the downward position, meaning the arms are forces into the closed upward position, and it WORKS!! I am also very happy with the aesthetics of the chair with all the curves

Despite in the above photograph showing the arms in a stable upright position, as I moved it round the workshop and took it apart then reassembled it repeatedly, one of the cogs at the base of the arms would often rotate out of its allocated column indent

So, the fault in the design was often with the curved teeth on the cogs as shown in this photograph. So if the croquet hoops were to lean outwards for some reason the tooth would just slip out of its inlet

I found the most effective solution would to cut little steps in the part of the tooth the touches the column that has to dig in to hold the column up as the trap is set

So by pushing the cog into the column I could mark the point at which they touch and then draw the cut out

After a quick trip to the bandsaw the cog now sits much better with the column, providing a better surface area to grip and rotate from. I then went on to do this for the other 4 cogs

If you look back to my models and drawings, the only component left to add to the chair are the 4 layers of cross braces. It is crucial to get this right as it is the cross braces that make the arms into a pod round the victim, so have to meet the other arm in the pod seamlessly

This brought me to a crossroads in the making of the trap. I could either spread PVA glue onto the bottom of the dowel uprights on the hoops and push them back into the base and then move onto the cross braces but this would mean when it came to the painting and applying a finish I wont be able to take the trap apart. And more importantly if I glued down the hoops, there would be now give in the gaps between the arms

But what I think will work better would be to tie string round the arms pulling them in to the pod shape position and using the technical scale drawing I did before to see the diameter of each ring that is then cut into five segments but from above will look a complete ring

Here is a reminder of the drawing I posted before with the measurements of each ring that is then cut up into the right sized cross braces - it was a really good thing I did this because I cannot see a straightforward way to work out the rings just working with my chair with the arms up

This is actually ring '2' (the second ring down) because I didn't photograph the drawing and cutting of the top ring. So first I drew a circle with a diameter of 510mm with a giant compass onto 18mm MDF. Then keeping the spike on the compass in the centre of the circle I decreased the radius of the circle by 80mm (the width of the arm at that height up the pod) so the diameter of the inner circle is 530mm

Then using a protractor I marked out the angles by which the arms of the pod will meet the edge of the ring, same as the angles I used when working out the positioning of the croquet hoops

for the mechanism. Then with the angles marked, I just simply continue the line out to the outer circle dividing the 80mm thick ring into five segments of one circle

I nearly forgot to reduce the thickness of the arms (18mm) from each segment as the arms will intersect the ring

Once I had cut the ring into the segments I was then faced with a new problem. I couldn't hold all five segments in position to see if they all work and fit together with the 5 arms and it would be inconvenient to ask people from my class who where in the workshop to hold them in place because they had their own project to be getting on with. So, one of the technicians subjected I use a glue gun to attach each segment as I work around the ring. The glue from the glue gun dries in seconds and is quite strong but with force can be broken

It then made sense to glue both sides to the segment to the arms, this way I can judge whether the segments fit and also will put the arms in into a perfect symmetrical pod

This is the chair trap from above with the first ring made up 5 segments of the same ring. This will be the only layer with a full ring because this is the round the victims neck and the rest of the front of the person can be left open, as seen in my design

This is the trap with the second layer in place (the layer I showed being drawn). I like the form the pod is starting to take!

From this angle you can really see the layer of different sized rings

I carried on this process of marking out the rings and segments from my drawings and amazing more often than not when it came to putting them onto the trap, they fitted! However some did need slight alterations through trial and error to make them fit. Here if the pod with all four layers of cross braces

Heres a brief video showing 360° panorama of my chair at this stage, if it doesn't work like on this link to see it in better quality on YouTube - enjoy!

Now comes the time where I glue the dowel uprights into the base. By gently pulling the cogs out of their inlet I could lift the pod part of the trap that is separate to the central column out of the holes and place them to one side on top of the base. I then went round with PVA glue lining the holes

Then I simply slid the dowel uprights back to the holes and forced them back in, some needed a hammer. To force the cogs into the inlets I wrapped some string round the dowel uprights and pulled them tight

This the trap with the cross braces, with the cog mechanism planted securely in its base

The final step in the making of my chair proved much more fiddly than I had hoped, thus I forgot about taking any photos of the process. I knocked off each cross brace in turn, this wasn't too hard as I they were only attached using a glue gun. Then I smeared PVA on one end of the

18mm thick cross brace and replaced it to the pod. To reinforce this cross brace as it is now only supported from one side I used the air pressure nail gun in the workshop with 25mm long nails to nail the horizontal cross brace to the vertical arm

Here you can see the trap open and activated, with the cross braces still attached to the arms. I thought it would look better if I attached the cross braces from the side on alternating rings, giving this interesting root like effect when open

Now that I have finished the manufacturing of my trap, I must now look at the finish I want to achieve