Sunday, 28 November 2010

Eleven (26/11/10 - 28/11/10)

With the deadline less than a week away time is quickly running out. At the end of last week I had glued one side of cladding to the front and rear compartments as well as thread the elastic material through it, as this can't be done once the other side is cladded. The other side would've been cladded if it wasn't for the lack of super glue, so it has been put off till tomorrow, none the less progress has been made:

This is what the front and rear compartments look right now, with the elastic interweaving it's copper rod ribcage where it couldn't go through the acrlyic splines. This problem was thought of when I was digitally building the splines so pre-cautions were taken; that the splines had a 1x25mm slot cut out so the elastic could slide through. But not all of these slots came out perfect, most warped meaning I had to thread the elastic underneath the splines. On the other hand, when it did work, it worked a treat:

The elastic ends were hand sown together to stop them coming out completely. Thankfully all of that will be hidden once the top cladding goes on, for the underside it looks like this (the gap in the styrene is where the elastic is threaded through):

And it working:

One problem I've noticed with the cladding is that the actual edges aren't as straight as I'd like, it's hard to describe without a photo, but I'll get one tomorrow. One way of fixing this is to use one of the laminates or heat bent acrlyic and cut off a slither from them and attach it to the top of the front and rear compartments. This would also help when screwing in the drawbolt locks.

Thursday, 25 November 2010

Ten (24/11/10 - 25/11/10)

Finally, giant strides. Even though weeks behind schedule I've actually got the main body of the bag in a somewhat assembled state, hopefully people will now start looking at it in a different light.

The big development since earlier in the week is the completion of the middle compartment. It took far longer than expected, mainly due to the epoxy resin being too weak for the job, which was the 5mm edge of the acylric to a milled off flat surface on the two segments of the laminated plywood (which had the slight curve), this photo should help if that was too confusing:

As you can see the plywood is also unsupported so they were incredibly fragile by themselves, for this reason I had to make two makeshift jigs so that they could be sanded and drilled. The jigs consisted of a simple 2x4 cut to the correct length so that the plywood didn't bend back on itself and double-sided to a larger MDF piece.

The reason they are in 3 segments is that 2 lasercut splines with the acrylic tube profile is put between them to make the middle tube in the hinge secure. If that once again sounded too confusing, this photo should clear it up:

Either side of the outer segments is a lasercut profile of the side components. Once again this is to keep everything level, but more importantly to stregthen the indivdual segments. Each segment has about 10 holes dripped in its edge where copper rod is slotted in, which then goes through the lasercut splines into the adjacent segment. These copper rods also act to keep the plywood up so that it meets the side component outline, as seen in this photo:

For example, this segment is sandwiched between a lasercut spline and the side component outline, so that the copper rod will thread through the segment and outline into the actual side component (which will be attached to the outline). This should hopefully make these segments stronger and less prone to sagging, which they do a lot. Also this way of attaching the side components to these outline allows me to spray the front, rear and middle components separately as the metal rod between them can not be threaded until the side components are attached.

On the front and rear side of things, both have had their internal structure done and are now in the process of cladding, which is proving to be a bit tricky, especially as I don't have a former. Anyways here is the bag assembled in skeleton form:

Tuesday, 23 November 2010

Neun (22/11/10) - 23/11/10)

Just for a quick update, the front and rear components which are now made of an acrylic 'ribcage' is coming along nicely, but by just putting it together I've noticed how fragile it really is. Enough to hold it's own weight and that, but I'm more worried about the folding preparation table inside which is quite heavy. One possibility I thought of is making it again with a blue foam interior and 0.5/1mm styrene cladding, this would make it ten fold times lighter, but it's all time permitting. On the plus side if I did do it this way I could add a spline (similar to that in the bottom photo of this post) which would connect to the acrylic tubing, giving it once again a larger surface area for gluing.

On the other parts of the bag, I've got my handle along with tuck-tiles (which I need to pick up) and the middle compartment is being put together, so hopefully that will be done along with the front and rear tomorrow afternoon. I also managed to flatten my chemiwood side components as it had wrapped when on the mill, this was done by putting it in the oven and then clamping it down to a piece of MDF, this means I can finally sand them down which has been long overdue.

Enough words, here's the ribcage as it stands this evening:

Sunday, 21 November 2010

Eight (18/11/10 - 21/11/10)

Well a lot has happened since the last update:
  1. Laminating the front and rear components has been abandoned
  2. The original former for the jig has been destroyed
  3. Moved onto the emergency back up design 
Why did I abandon the lamintating? Well for one, the edges after the curve would jut out as seen in the photo:

Even though these parts are excess and would be cut off, they had an effect on the curve which is the vital part, this effect is that they have stretched it out of the radius I need, turning it into a more eclipse segment than a circle. I can't think of a reason for this as the jig disallowed any movement for the plywood and I had enough clamps (both horizontally and vertically) to hold the formers firmly in place:

The middle photo is where I had to rip one of the side parts off to get the laminate out once it dried, this leads on to why the former was destroyed. As there is immense pressure put onto the plywood, some of the glue on it drips out of the side, thus gluing the laminate to the jig, in hindsight I should've removed the side bits completely when doing this, but having learned from heat bending acrylic, it does have a tendency to veer off to one side. For a simple fix I made these side bits removable so that I could just unscrew them and slide the laminate out, but alas this didn't prevent it breaking; having left the plywood dry over night I began removing the clamps and formers, only to find the smaller, original one stuck to the laminate. I pulled it off only to have the plywood, which was glued and nailed, peel off:

For what it's worth the newer former was fine, even though that was to be the last time I laminated.

Before I put the jig behind me, I noticed I didn't have a photo of it and the two formers:

As you can see the plywood was slotted into the trough thus leaving no room to jut out after the curve, so it perplexed me why it did. Although I didn't want all of this hard work and plywood going to waste I used a laminate to create the middle component which has a slight curve either side, although it's so slight it's hard to tell from the photo:

Moving on swiftly to the backup plan. This idea of splines running between segments of the front and rear components came to me once I started laminating. The hinge is my Achilles heel as it was always going to be the most fragile part even though it'd be the part which is most used. Having used Tensol on my earlier tests with acrlyic, finding a strong enough substitute to attach the acrylic tube to the plywood was always going to be a tricky one, in the end I was going to rely on epoxy resin. After little thought I knew that wasn't going to be enough so I thought of having splines between segments of the laminate which had the outline of the rod attached, these would not only be glued to the laminate but also threaded with 1.5 copper rods going into the laminate sgements either side:

The acryic tube would then have its ends glued to the splines and attached to the laminate down its length. Once the laminating didn't work out I had to resort to the idea of just using the splines, with 0.5mm styrene cladding to give the appearance of it being solid, when in fact it's hollow:

This does have two advantages over it being a solid; it's that much lighter and its profile is more accurate. On the downside though; it's that much more fragile and being hollow attaching the tuck-tite locks is going to be a problem.  However as the middle component is solid and segmented by the splines it doesn't suffer from these issues, which is a good thing too as the handle (when it arrives) will be attached via screws.

Wednesday, 17 November 2010

Seven (15/11/10 - 17/11/10)

First things first here's the trough fix for the jig I talked about in my earlier post:

Now onto the big news, I've given up on heat bending and moving on with laminating. This dramatic change comes as a result of too many failed attempts with acrylic; mainly that the corners warp giving an uneven profile which would be too much of a hassle to fix, in other aspects it's really hit or miss. In hindsight I should've made the jig that much longer so that I could heat bend the piece and then cut off the warped corners, but I don't have time to do that now.

With laminating I have that much more time to adjust the jig and clamps before the glue sets, one major problem I had with the acrylic. I tried my first full length piece yesterday and when I got it out this morning there was a nasty lip in it where it hadn't been flattened throughout:

To fix this problem, and one that I should've done from the start is make the jig double sided, so that both curves can be done at the same time. This is what I achieved today, making the former jig for the other half, along with milling out the side components to make them lighter:

The issue I had with laminating earlier is how to attach it to the acrylic tubing. This issue has been resolved with my idea of laser cutting outline splines which run down the curve, it's hard to describe it words but tomorrow I'll have the drawing done. These splines will be attached the plywood via copper rods which run down its length.

Sunday, 14 November 2010

Sixth (11/11/10 - 14/11/10)

Having thought my jig was complete I soon noticed one key aspect of the design was missing. When I tried a few tester pieces on it, getting the negative curve former (the part which slots on top) in all the way was a problem, as the acrylic would jut out from the one sided trough, it's hard to put it into words but sadly I forgot to take a picture of said situation. The fix to this was easy though, I cut a slice off the negative former and glued into into the jig creating the trough from which the material would sit and not jut out. With that done I got onto testing it out again with mixed results, in that the clamps which held the former under pressure had to be balanced on either side and already at the correct distance apart so they can be clamped in place quickly as time is of the upmost importance.

While trying out it with veneer and tightening the clamps I heard the former jig crack, thankfully no damage was done by obviously I needed to fill the gaps between the splines some more; this was done by simply slotting down correctly sized pieces of 12mm MDF (photos of this will appear in the next update).

On my first attempt at the final piece my calculations came up too long and the finished piece was 30mm longer than it should have been, but this is fine as I can use the curves for the middle compartment. I altered my methods in that once one side was heat bent, I'd turn it round so it met the other side of the jig, clamp it down and then heatbend the straight side down over the jig. This is instead of slotting it into the trough and hoping the heat bent curve on the other side matches the jig.

Enough talking here are photos of the heatbent pieces; the veneer and the too long acrylic:

A small slice of acrylic to test out the new method of heatbending to make sure it goes to the correct length:

The smaller slice under the CNC side:

Wednesday, 10 November 2010

Fifth haul (8/11/10-10/10/10)

Today marks the completion of the jig and a development in the material side of things. First off, the jig and its construction:

Having learned from my earlier jigs; trying to get a uniform curve is pretty hard when bending it with your hand, the best way consists of a two part jig which can be clamped together to hold the acrylic in place. On my previous one of this design the actual curve former was made of different MDF parts, sanded together to create the curve. However on this one, which has the width of 410mm trying, to maintain the exact curve along all those bits would be far too time consuming, this is why I went with using MDF splines and veneered 1.5mm plywood over them to create one smooth, uniform curve across the entire structure.

I've yet to try it out, but from my previous one of this design the curve it produces is far more accurate, and as this one is far more secure and flawless the overall finish should hopefully be near enough perfect. On the material side of things, I've got my elastic strip for both the rear and front components along with webbing for the carry handle (the shoulder strap will be brought tomorrow):

Along with those two I was told about a haberdashery website where I came across this bag fastners (MacCulloch and Wallis), which has exactly what I need. I'm going to try a few locksmiths tomorrow to see if I can find anything more precise, if not I'll be using this one.

Monday, 8 November 2010

Fourth haul (3/11/10 - 8/11/10)

I wish I could say I've come on leaps and bounds but upon relfecting about last week it strikes me as to how little was achieved. This is mostly thanks to the trouble with the internal compartments. What was suppose to be an easy task of vacuum forming turned out to be a nightmare in waiting. The internal compartment itself consists of a rectangular block, with a taper of 1.5 degrees on all sides, along with a 5mm fillet around the top and a 10mm fillet down the sides. Little known to me at the time, this slight taper would be the cause of all my grief. Once I had machined it, I immediately vacuum formed it, but trying to get it out proved a nightmare, resulting to literally cutting the shell in half to get it off the former:

Having talked about possible alternatives I went with the most obvious choice; sanding and spraying the former to a perfect finish, thus giving a better shell finish plus making it easier to slide out. This wasn't the case however as it still proved impossible to remove without damaging the shell. Going to the other possibility of drilling a hole through the former, which the air gun can fit so that I can hopefully blow the shell off, unluckily I didn't have time to try this out last week. Worst comes to the worst I'm going to have to fibreglass cast it, which is a lengthy process that I'd rather avoid.

Having spent far too much time on it I've started this week on the different foot, working back with heat bending and jigs. I've got half of the jig completed so far, so hopefully tomorrow I'll have it finished by tomorrow along with the heat bent pieces.

Tuesday, 2 November 2010

Third haul 2/11/10

To continue on from yesterday, I've got my second side component CNCing:

Along with that, I've begun work on the folding preparation table, it's one of the simpler parts to the model but it involves a hinge, so I'm using it as a practice piece before I move onto the larger front and back components. Unlike them however I'm using 10mm acrylic tubing with a 6mm acrylic rod threaded down it. To prevent said thread from sliding out I've capped off the edge tube bits and sanded it down so it all sits flush. I used tensol on the hinge with mixed results, one side dried like a dream, the other part not so much, but it's overall strong enough for me to dangle, this is however not dangling:

As tensol takes a while to dry, I had to leave it for today and will re-tensol the hinge tomorrow. When it was drying I took a quick vacuum form of the side components, the outcome was favoured by most people than having it sanded down, but this then differentiates from the actual design:

Monday, 1 November 2010

The second haul (24/10/10 - 1/11/10)

First things first, having taken over 2 days to complete I've got one side component ready to be finished:

There was a bit of trouble behind the scenes; after having learned Solidworks with the hope of using the inbuilt CAM software I found out that it wont work with our machine due to some license problem. This meant I had to import it into Rhino and use that inbuilt CAM software to get it to work. Having been somewhat familiar with Excalibur the new steps in Rhino's CAM, which are meant to be easier to use, proved to be a bugger in trying to understand. Of course the photo above is enough proof that this hurdle was soon conquered, thankfully.

On the hinge side of things, having played around with 15 and 10mm acrylic tubing, I've found the 15mm is the best all round, being able to have a 10mm aluminium rod threaded down it, thus creating an overall stronger hinge.

The 10mm acrylic tubing with a 5mm rod threaded down it:

 The 15mm acrylic tube with a 10mm aluminium rod threaded down it:

The best discovery however was Tensol, a plastic adhesive which is basically liquid acrylic, perfect for permanently attaching the tubing to the front and back components. This was a problem that has crossed my mind since the beginning; a lot of pressure will be put onto this hinge and if it isn't tightly secured to the front or back components they'll just snap off. Thankfully Tensol dries like a rock with little to no mess, perfectly suited to this sort of design.

The use of Tensol does then exclude another method of creating the front and back components, that is laminating. After solely heatbending acrylic into shape with mixed/undesired results I tried laminating to get a uniform curve profile along it. This meant making a bigger and more secure jig, which included a female part to sit on top which could be clamped to the male, leaving no room for the material inside to move. I tried it out on acrylic first and straight away I got a much better curve, with it looking promising I tried laminating with 3x1.5mm plywood with a 0.5mm plastic sheet to make it have an overall 5mm thickness. The result was a strong curve, but not as defined as the acrylic:

Of course if there was a secure way to attach the tubing to the end of these components if they were laminated, I would choose this method but for now I'm sticking with acrylic, Tensol and a secure male and female jig:

To end on a downer, I played around with magnets during the week as this is how I plan on keeping the front and back components from flapping open; the results were nothing short of a disappointment. Having a material thickness of 5mm to work with I brought 3mm thick magnets which I inserted into a slot that I had milled out. This proved a problem too, as I tried both ways of doing this, before and after heatbending. After was the most promising as the one before wrapped creating awkward troughs that the magnets did not fit into. Anyways, the magnets I used were simply not strong enough so I plan on investiagiting into stronger magnets.