Saturday, 4 December 2010

Twelve (29/11/10 - 4/12/10)

So this is going to be a large update, first off it was the deadline yesterday and sadly the bag was not complete. Secondly, I had to alter the acrylic ribcage design, this was to fix the problem I mentioned in my before post (about the styrene edges drooping) but in the end I had to re-build them completely. Anyways, I'll start in chronological order from how the model was at the start of the week and finish with what state it was in yesterday, Monday:

The old ribcage and how it was further supported by 1mm aluminium panels bent into shape and then glued onto the structure. This actually worked surprisingly well and made the overall piece a lot more sturdy, but even before I did this it was still quite sturdy.

Along with that I had also attached one side component to the middle component:

The inners were cladded due to the acrylic part of the middle component being covered in scratches from where I had filled it to give the appearance of a solid structure. The cladding provides a flawless finish, but even then I could still fell the "lumps" of where the acrylic splines stick up between the laminate pieces, so I ripped it off for further sanding.

Back to the ribcage and why I needed to re-do them completely. While the aluminium panels seemed liked a good idea at the time, when it came to cutting the edges off the components (so I could attach a slither of the laminate to either edge) I had to use the metal cutting bandsaw which pretty much destroyed the cladding:

In all honesty I jumped into this idea without putting enough thought behind it, maybe it was due to the impending deadline that I wasn't thinking straight, because even though I could sand and fill the styrene back to its flawless finish I hadn't probably thought of how to attach the laminate to these newly cut edges. Just gluing it wouldn't be enough as there is a lot of pressure going on the entirety of the structure especially the edge where acrylic tubing is. The only feasible way would be to drill into the acrylic splines from the top and slide a 1.5mm copper rod down it which would then slide up into a corresponding hole in the laminate.

The risk of it breaking due to this weak area was one too great seeing as this is meant to be a working product model so it should be able to withstand constant opening and closing of these parts. With this in mind and time running out I needed to come to a decision on which path to take: go with the original ribcage and hope the joint doesn't break or re-do the splines so that they're one piece which runs through the laminate as well. This may sound confusing, but thankfully I have photos of what I mean, using the same idea as I did on the middle component the new splines would be attached to the laminates with a 1.5mm copper rod running through both:

The laminate which would sit on top would have pre-drilled holes so that it could just slide right on. Going with this re-design at the last second really put me back a day or two as not only did I have to get back on the laser, but I had to re-build them, well actually one due to time constraints. With the deadline pretty much the next day and due to the snow not being able to stay late, I had to prioritise what needed to be done but in a realistic manner, I choose to get one at least the rear component assembled.

I didn't spend the last week solely focused on these parts though, most of the time I was sanding the main body (which consists of the rear and middle components assembled). If you can remember from one of my earlier updates I said I'd only attach one side component until all parts were finished and once the front and rear components were threaded into the main body attach the other side component. Well this went out of the window too as I went ahead and attached the other side component so I could sand and fill that when it was attached to the rest. But to allow me to still thread the alumuinum rod down its length I drilled a hole which went straight through the side component, so instead of attaching, sanding and filling the entire component at the end, all I have to do is fill in the drill hill.

Anyways, this is how the bag looked yesterday at the deadline:

The newly designed rear component which still consists of an acrylic ribcage but also implements the laminates to give a constant solid edge: 

This way still allows me to attach the elastic straps as I did previously, after which the back would be cladded. But before I permanently attach these straps I plan on filling and finishing the front to a good finish without worrying about accidentally spraying the straps in the process.

As you can also see I attached the draw-bolt locks as well as the handle. This proved me to be somewhat difficult (and I didn't get it done completely yesterday) as the screws would go though the laminate (which is only 5mm thick) and poke out the other side. The smaller screws on the locks don't protrude as much but for the larger ones (6mm) used on the handle I had to saw off the excess, if I had the time I would've done the same for the smaller ones. The cladding on the internal side (once glued in) will cover these holes, same goes for the holes caused by the feet.

Realistically I need two weeks more to get it properly finished, what's left to do:

 - Finish the main body along with spraying
 - Finish off the rear component, this includes attaching the straps as well as sanding, finishing and spraying
 - Cut out the front component and do the same
 - Assemble the newly design preparation table (this has already been cut out)
 - Lathe the feet and shoulder strap holders
 - Vacuum form the internal boxes

Sounds like a lot, but the most time consuming part is the finishing which leads me onto a point few others share with me. As this model is actually going to a client who will be using it as a demonstration model during meetings and that it has to be up to a perfect standard, this includes the finish and how it works. If I rushed it towards the end to meet the deadline I'd only have cut corners which I'd have to go back to to correct before handing it over to my client. I'd rather not do this but instead take the extra time to get it right the first time. It's not like my past models in which flaws could be hidden by camera angles and post touching up in photoshop.

Either way it will be left in this state until I can work on it again which will hopefully be the start of next term.