A return to the bike build.

 

 

Minimal fuel tank!

In the last installment of the bike build, which was let’s face it, too long ago and must be wrapped up soon, the exhaust was coming together. In order for me to be able to hear the results as the pipe came together a small tupperware container got a makeshift outlet fitted into its base and was then mounted to the main frame spar with a cable tie. With a bit of fuel onboard the engine could be started and run without the fuel tank in place and the exhaust listened to. The tank meanwhile was being prepped for painting.

The “silencer” that had been ordered came with an internal baffle already, if that’s what you could call it. You see these pipes everywhere on custom modified bikes so it will come as no surprise to anyone who’s ever had one that internally they are rudimentary to say the least. There was a piece of glass fibre packing inside the pipe but this was as good as useless. It would have disintegrated if you’d held it behind you and broken wind, frankly. So, first job was to get some proper packing material and firmly wrap the baffle so at least some of the noise could be absorbed. It was still too loud.

After a quick discussion about exhausts with the guys who’s workshop I was borrowing it was decided that the best thing to do was make a smaller secondary baffle that would fit into the end of the main pipe. Reckoning that the area of the holes in the internal cylinder should match that of the outlet it was time to have a go with the MIG welder. Not having used one much before, a quick session on the net provided some basic guidance to supplement the rather sketchy instructions contained in the user manual.

So a few hours later we had a finished baffle piece that fitted into the end of the main one that could be secured with three self tapping screws. Easy to remove and modify if need be and pretty much hidden behind the reverse cone end cap of the silencer. A couple of coats of aerosol heat resistant paint and the job was a good ‘un. This made a real difference to the sound and would be easy to remove if greater fruitiness from the pipe was wanted.This was the last fabrication job to do before the final build. What was up next was the biggest job of all, painting the bodywork.

 

Before moving on to that episode here are a couple of thoughts about MIG welding. Never having done any before, the thought of using the welder was a little daunting. Welding in all its forms has always come across as a bit of a black art, a deeply skillful craft practiced by wizards of metalwork with years and years of experience. This is all true but, it is also not as scary as it would seem. They say that every journey starts with the first step and so it is with MIG welding. Taking the plunge and having a go can lead you, with patience and concentration, to a thoroughly satisfying learning experience and hopefully a new found skill, and a finished part that you can be proud of.

 

My own introduction to this skill took me from making a simple baffle on the first day to knocking up a small paddock stand for the bike, to use during routine maintenance as I’d seen fit to remove the centre stand as part of the weight loss program. All within a week.

 

As mentioned before the manual that came with the welder was a little thin and searching the internet for tips and tricks threw up some really useful information and some tips which I never would have considered in my inexperience. Here are a couple of links to the two most useful websites found. The first one was the best: Firstly Tips and tricks and the second one here. Sadly the need for welding anything in my everyday work is rare but it hasn’t stopped me from wanting to buy a welder and start making something.

 

Although my skills remain relatively basic I’m no longer reluctant to consider using a welder for smaller jobs. Welding bike frames is something best left to experts for now but, with a new skill in the back pocket, the options available when making more complex ancillary parts has now grown and that can only be a good thing for when the next project comes along.

 

The welder used was a small portable unit with up to 150W of power, switchable. It had a variable speed wire feed, a small remote gas bottle (Carbon Dioxide/Argon mix worked best) and nice hefty earthing clamp.


 

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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.

The chain run.

Does it make sense?

I knew that having made the clock mount and its accompanying surround I should really have got on with some kind of front screen, but I didn’t. I decided to make a chain guard instead. In a funny kind of way I found myself in the situation where I’d tried to plan everything out as much as possible, in a loosely efficient project management kind of way, and then found myself deliberately jumping from one part of the plan to another rather randomly. I’d call it something like organic execution. Having planned everything out systematically, I was free to approach the list of tasks depending on how I felt on the day. That day I was much more in the mood to make a chain guard than to start to get to grips with the next big thing which was the rear mudguard or fender.

At least with this next part I followed very closely one of my guiding principles of the build which was to lose weight. The standard part, as any GN owner will tell you, is a substantial piece of kit. Whilst I understand fully the need to prevent ingress of foreign objects into the chain run, I can’t for the life of me see why said part has to be the depth of a piece of industrial guttering and sturdy enough to shake off an attack of rocket propelled grenades. Whatever, it weighs a ton and made its way swiftly into the ever growing pile of discarded ironwork growing in the corner.

A bit blurry I'm afraid

It would have been much easier I know, to have followed the weight saving creed to its maximum and not fitted anything at all but I wanted something there to stop things like loose rucksack straps getting too close and prevent the back of the bike and ultimately me, getting a good spattering of flung off chain lube.

A quick trip to the DIY store and I’d got myself a very handy length of aluminium ‘L’ section, the angle to give it some rigidity, and a length of flat bar as well for making a couple of brackets. By trimming off part of the angle, to create a flat section, it was easy enough to bend the strip around a quick wooden former to get a radius that would sit nicely above the rear sprocket. I could then trim the length of the whole thing at the end that goes over the front sprocket. Duly done it was just a question of working out how high off the upper chain run I wanted it to sit. As the chain can flap whilst your traveling, too low and each journey would be a rattling affair. To tell the truth I did get it a bit low to start with and modified it very quickly soon after the first test ride. For the rear of the guard I made the bracket at an angle to match the rake of the rear shocks, to kind of blend in, and secured it to a conveniently located hole above the chain adjuster on that side. The front bracket was a simple piece with a single 90 degree bend in it, and I cut it to a length which would allow me to raise or lower the guard at that point should I need to, which I did as you’ve already read. I attached the brackets to the guard using some ‘Pop’ rivets, another godsend to the home builder, and it was complete and ready for a coat of trusty old black paint. Job done. Now I knew I couldn’t put off the rear fender any longer.

Too much too soon – Part 3

 

 

 

 

 

 

 

 

 

Without much of an idea about how I wanted to start this post I sat staring at the screen for a while before staring out of the window. “It might still be January but, what a beautiful days it is” I thought as the sun streamed into the room.

In fact I’d just charged up the battery for the Triumph yesterday so what better thing to do than to take the ol’ fella out for a quick spin. and have a think about my post over a cup of hot tea at The Ace Cafe.

Having removed the bike cover and installed the newly charged battery I couldn’t help noticing how brightly the sky was reflecting in the polished alloy of the exhaust silencer. It looked just like how we were taught to render chrome, all blue sky up top and a  brownish ground line with a bit of black in there for effect. A bit cartoonish really. I realised I didn’t need to contemplate my post over a cuppa at the Ace, but I went for a ride anyway, it was the right thing to do.

And that’s the thing about colouring metal, particularly tubes, pipes and so forth. You can really ham it up in a cartoonish way and it still ends up looking kind of real. Obviously to the purist there’s a lot more to it than that but it’s surprising what you can achieve with very little effort. A dark line or area denotes a reflection of the ground and another in blue gives you that reflection of the sky and the whole lot looks kind of shiny. No matter how many reference pictures you look at, you will always see that shiny metal is the same colour(s) as everything around it. This is my very simplistic view but it works for me and prevents me from becoming utterly confused when I start to wonder about what is reflected in what.

There’s a similarly simple approach to the flat alloy surfaces which make up engine cases etc. Parts are generally a tone of grey and the junctions between the surfaces pick up the highlights. From this simple premise you can then go into as much detail as you want but for me it’s always a safe place to start. Build it up slowly and stop when you’re happy to.

I’m not exactly sure why I decided to apply colour to the metal bits first on this drawing, it was some kind of subconscious decision to do with methodical working or something like that. It kind of worked but left two areas of indecision in my mind. First, I couldn’t decide what the main exhaust should be, chrome or a kind of brownish stainless steel. Second, I didn’t know at this point what colour the bodywork would be so I couldn’t reflect that in anything. I thought I’d make my mind up about those two things at the next stage.