Now that I’ve redesigned the frame it’s time to start adding bolts to the drawing to find out whether I can actually hold everything together. It might seem a little superfluous to add every single bolt but there’s a couple of good reasons to do it.
The most important reason to add all the bolts is to find out if you’ll have any clashes between bolt heads or or bodies which could cause a awkward redesign part way through the build. In fact I hit exactly that issue which you can see in the image below.
At this point I was using 50×5 equal angle for the brackets. The layout lines are 10mm from each edge and, as you can see, the bolt heads clash. I could probably solve this, just about, by moving the inner most layout lines to 12.5mm but to be this was feeling pretty cramped anyway.
The solution was to switch to a 70×6 equal angle which has enough space for a sensible bolt layout. As you can see in the next couple of images there is a little (about 2mm) clearance between the bolt heads on both axes so either bolt can be added and removed independently of the other one. The other benefit of this additional size in the angle bracket is that I can copy an idea from this build and and use taper pins to ensure perfect alignment if I ever take it apart and put it back together.Alternatively I could have using M6 rather than M8 socket screws (aka cap screws) but I’d like to try and stick to the same bolt everywhere and that little bit of extra chunkiness in the M8 is reassuring.
I’m really in two minds regarding the taper pins and epoxy though. I can see why it’s been done but it makes every bracket a custom fit for the particular joint it’s supporting and it adds an enormous amount of additional work. My current thinking is to get everything set up and aligned as best I can using the brackets and bolts and then spot weld all the joints on the sides except for those that hold top rail.
I won’t weld the top rail on because I want the option to switch this rail out in the future for one that has been machined flat so that I can upgrade to profiled rails for example. Having the top rail bolt on also means that I can add shims easily if the rails aren’t quite level.