Cutting metal at last.

Graphic ideas appearing.

Whilst I had been deliberately distracting myself I had been fiddling around with a number of other things as well. Stripes of white electricians tape had appeared on the tank to see how it would look, various graphic devices had arrived on the side panels and I’d been playing around with ideas for a front fly screen.

So now I want to tell you how I made the rear fender. What I also want to do is try and make it a bit more interesting than just a plain old description, blow by blow as it were, of cutting bits of metal and bolting them together. It’s something that’s started to creep into my thoughts as I try and create more posts for the blog. As you well know from very early posts, or you may have read my “About” page, I spend a great deal of my professional time making models and prototypes for people. That process invariably involves employing lots of techniques and quick fixes to achieve particular results. So I’m always thinking about how I could pass on any of these things to my readers in the way of useful tips etc. The fabrication of the rear fender seems a great place to try and communicate some of these things. So here goes, though having said that I may very well get to the end of this bit and not passed on anything at all. The following piece will certainly contain some.

Plenty to play with.

As you will have gathered, my start point for this next phase of the build is a bike frame with the two rear seat support stays cut off and a moulded plastic inner fender which I’m retaining to help keep all the road crud out of the back of the bike as I’ll be using it in all weathers. I’ve also got my hands on a large rolled section of aluminium mudguard, sold by those wonderful folk at Burton Bike Bits. I’ve chosen a rounded section with a rolled edge, for neatness. It arrived as almost a full circle of material. The plan was to first figure out how to mount it securely, I didn’t want it flapping about as I bounced down London’s crappy roads, and then to decide on a length that would offer good protection and cut the piece to size with the end shaped how I wanted.

Mounting plate attached to cross member.

The first task was to secure the plastic inner guard, which only loosely clips to the frame and relies on the original mudguard for support. Conveniently nearby is a cross brace on the frame under the seat so I made a plate with a protruding finger of material out of 16 swg mild steel sheet that I could secure to the cross brace and to the plastic guard. I couldn’t weld at this time, and only now can do rudimentary stuff with a MIG welder, so I had to screw the plate in place. I always find putting threaded holes directly into thin walled tube a bit of a fudge and on this occasion used what I know as Pull-serts or Grip-n-serts. These are threaded inserts specially designed for creating blind threaded holes in sheet materials. Very handy things, available in most thread sizes and they give a great result where you don’t have enough material to provide a decent thread length in a tube wall, sheet thickness and even extrusion wall. Three of these at M5 size into the cross member worked a treat and provided a very sturdy mount for my plate. A happy coincidence was that the plate also formed a neat compartment under the seat for the electrical connections to the rear lamp cluster.

Foam block and tape doing their jobs.

So now I had the plastic guard secured and with a single central hole drilled, a place to mount the rear guard metal section enough to allow me to start to think about its length, angle and subsequent mounting points. I’d cut the big piece of rolled section down a bit to make it more manageable and found a handy lump of scrap modelling foam that I could sit on top of the tyre to support the piece while I decided on angle and length, helped, as you can see in the photo by a piece of duck tape on top.

Anyone familiar with a retracting tape measure knows that curved sections of sheet material are only rigid in one plane and waggle about like no ones business when you least want them to. The same applied to the rear fender section so the next challenge was to come up with a way of preventing that action occurring at the back of the bike. Time to get the sketch book out.

I’m not sure if Pull-serts live up to being a top tip but it’s a start.

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