Wyvern – Frame Building – Day 21

I’ve not managed to get much done over the last few days as work has been getting in the way, I suppose I need to do something to pay for all this CNC equipment though. I’ve got all of the brackets for one side drilled and fitted now but I’m starting to wonder whether I’d actually be better off if I just welded the sides up.

I decided to put the brackets on the legs first and then fine tune the supports to match. This seemed like a much easier way to work than trying to fit the legs second. To be honest though now that I’ve done it I don’t think either route is easy.

In theory this process should work really well. In practice it worked fine for the first support post but the second post just wouldn’t go square even when given more forceful persuasion. The post moved while I was transfering the holes on the second support so I’ve ended up with a little bit of misalignment, the amount of correction in the bracket is just enough to solve the problem but I’m a little concerned I’ve introduced stresses into the frame.I mounted the legs and roughly squared them up to the top rail then mounted the support post putting a bracket on one side. A clamp held the bracket to the top rail and I tapped it back and forwards with a hammer until it was exactly perpendicular. The screws holding it to the bed bar were then tightened down hard and it was checked for alignment again. As it was spot on I carefully fitted the other bracket and transferred the holes.

I tried taking the bracket off and squaring up the leg but as I put the bracket back on everything gets knocked out of place. I also tried measuring the outside of the corner but that is unreliable as it’s not clear if I’m measuring the cut face of the guild rail or the leg. It turns out as well that the brackets don’t really offer any flexibility on alignment. Each individual joint has some scope for repositioning but because there are something like a dozen brackets per side you end up in the position where the natural errors eat all the flexibility you’d expect.The support posts wen’t well enough that I decided to try straightening up the frame to see how accurate I could make it and this is where I’ve hit some problems. The two images above show me squaring the leg (vertical) to the bed rail. I initially used a roofing square then remembered I had a fancy digital angle gauge. In both cases though I’ve had to clamp a block of wood to the leg to get a surface to measure against. Really what I wanted to do was check the leg against the guide rail but this is basically impossible because there is a bracket in the way.

I also checked that the bed and guide rails were co-planner using a digital angle measure (the sort of thing used for setting saw blades etc). It reckoned that they were out of parallel by 0.1°.  That doesn’t sound like much but over the 1800mm of my bed it works out as 3mm. The problem there is that the measuring tool is only accurate to 0.1° so for all I know it’s perfect. My gut feel is that it’s less than 1mm out and I had the angle gauge in a slightly different place on each rail. There is a visible dip in the middle of the face of box section steel which could easily throw the measurement off.

So, after much drilling and tapping of holes I’ve back looking at welding equipment which I’ve got no where to store. I may just have to put this project on hold until the workshop gets built.