Category Archives: The 250

A return to the bike build.

Posted on by Soulcraftcandyman
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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.


 

Support your local fender.

Posted on by Soulcraftcandyman
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Contrasting profiles.

Following my slight diversion to talk about that stunning Moto Guzzi, here we are back again to get started on the metalwork that’s going to hold my rear fender in place. Revisiting my brief again and looking at where I’d got to so far I could see that I was looking to make at least two pieces that would hold the fender on the one hand and then help to tidy up the back end on the other. So the first thing was to turn the piece I’d sketched in my notebook into 3D and see where I stood. I had the mounting plate I’d put onto the frame rails as one fixing point and I had the cross piece formed by the seat support as another, so I reckoned my next bit would join these two and reach back to support the fender behind the seat mount. You’ll see also from the picture above that I had a mis-match between the curvature of my rolled section and that of the inner plastic guard which sat in front of the rear tyre. I’d need something to deal with that too but for now I wanted to get on with the fender support.

Crisp thin card, lovely stuff.

It’s an age old adage, and you’ll here it from many a craftsman/maker, that it’s always best to measure twice and cut once. This simple advice has saved my bacon on many an occasion. In situations such as this where I’m working without any kind of formal technical drawing of a part I bring a second safety net into play and that is to make pieces in card first, change and modify things until I’m happy and then carefully replicate what I end up with in metal or whatever material I happen to be working in. Again you’ll hear it from all quarters that knocking things up in card is a great way to avoid time consuming, and sometimes expensive mistakes. I’ll say a bit more about card in the following post.

Holes added for visual lightness.

Happy that my card creation was what I wanted I marked out the resultant shape in flat form on my sheet of steel, making any final adjustments to dimensions  and hole positions. I did most of the metal cutting for this build with a jigsaw fitted with a fine toothed blade for metals. Working slowly and methodically it proved to be the best way to cut out flat parts that required the minimum of hand finishing by file. Cut out and finished, I bent the piece to shape in a large bench vice and positioned it to allow me to mark the hole centres for fixing it to my frame plate and the fender, which by this stage I’d shortened to close to the final length.

Tie bars in place.

I then riveted it in place on the plate and put a small bolt through the hole to secure it to the fender. This really went some way to eliminating the flexing I was worried about, particularly in the vertical plane but there was still quite a bit of movement in the horizontal. I decided that I needed to create some side supports and elected to put two thin tie bars between the seat support mounts and the sides of the fender part. I had some scraps of stainless tubing to hand and these worked perfectly after I’d flattened the ends of my lengths, drilled mounting holes, put a radius at each end and bolted them in place. Fixing things in this way, with nuts and bolts, meant that I would always be in a position to take it all apart should I ever need to mend, modify, replace or repaint anything in the future. At the same time I chose to make everything even more sturdy by drilling two more M6 bolt holes through the seat support cross member and the new fender support piece. At this point in the game everything was rock solid and I was more than happy.

Next up, finding a home for all the stuff that was going to be mounted on the fender itself.

Cutting metal at last.

Posted on by Soulcraftcandyman
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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.