No matter how much I tried to convince myself otherwise I just wasn’t happy with the design of the frame. Having the legs on the inside of the frame just felt an accident waiting to happen so I bit the bullet and reworked the frame to give it a more conventional design.
Rather than having the main rails on the outside of the legs I’ve moved the X-axis rail on to the top of the legs and the bed supporting rail to the inside. This does present a slight issue with the additional supports for the X-axis rail but that’s fairly easily over come but bolting inside the support pieces.
The bracing I had in the previous design just didn’t look right to me so I’ve replaced it with a piece of box section. There is a drawback to this though – the brace will have to be welded at the top. Initially I’m going to try running without these braces to see how it goes. They are fairly easy to put in later if necessary.One benefit of having the bed rail on the inside is suddenly all my bed rails get 100mm shorter which saves a decent amount of weight. I also reassessed the spacing of the bed rails. They were about 200mm apart which seemed excessively close if I’m going to use 18mm ply at the bed. I ditched a rail to give a spacing of around 250mm and another weight saving.
The really big benefit of this design is that the X-rail will be easy to adjust in both the Z and Y axes. To alter the Z axis I just need to shim the tops of the brackets, to alter Y I can simply enlarge the holes in the bracket a little and add a washer.
I’m still not hugely keen on the stretchers but I think they have to stay. I’d rather they were 50x50x4 but the added weight is more than I am willing to accept. The total weight for this design is about 100kg which is roughly 10kg lighter than the previous design.
I’ve also had a chance to put in a few other components and some of the bolt holes.