Tuesday, 31 March 2009

Mind the gap.

When we had the swingarm mocked up, the margin between the tire and the upper part of the swingarm [where the shock attaches] was only about 15 mm, which is cutting it a bit close since the tire expands a little from the rotational forces. I wanted at least 10 mm extra, but I didn't want to move the shock anchoring point under the top tube further forward – purely for esthetical reasons – and I certainly didn't want to elongate the swingarm.

What to do? Well, you could always take a hacksaw to your brand new Öhlins damper:-) Fortunately, the lower mounting fork on the damper was some 14 mm longer than necessary (see red arrow). We'll shorten the mounting fork by about 13 mm and get the tire clearance we need. More pics shortly.

Sunday, 29 March 2009

Swingarm, part 3.

The swingarm is coming along nicely now. The mounting tab for the kick stand on the left side of the frame had to bent a little to clear the swingarm, otherwise it's plain sailing at the moment. Next up is fabricating the "cage" on top of the swingarm, onto which the shock will be attached, and then the shock anchor point under the top tube. And yes: the two less shiny sections of tube is only there to keep everything in check during fabrication:-)

Saturday, 28 March 2009


American Penske shocks seem to be "de rigeur" in flat track racing circles. And they are undoubtedly great shocks. But I felt I was letting the side down a bit if I didn't choose a Swedish shock for my project, seeing that we have what is probably the highest profile brand in racing shocks right here in the land of tall blondes and free sex for all. I've been working in the advertising world all my life and I have to admit that I am unhealthily hung up on brands. I buy my computers from Apple, my running shoes from Ascics, my TV's from Sony... the list goes on and on, exposing my inner insecurity and inability to see beyond branding and smart marketing. But I digress.

I spoke to a very helpful guy at Öhlins and he sent me a list of shocks that would suit the frame I'm building. And as it happened, the shock I finally bought was on "sale", and I ended up paying about 475 Euros for it. Not cheap by any means, but still some 35% off the original list price. The model number is KA202 and it's 343 mm long and has a stroke of 74,5 mm, which is in "the ball park" for flat trackers. Penske flat track dampers are normally a little shorter at about 320 mm, but since we are making our frame from scratch, those extra 20-25 mm aren't an issue.

I chose a shock without a remote reservoir for a cleaner look, but with a remote spring preload adjuster that will be mounted within easy reach under the saddle. The guy from Öhlins recommended a spring rated at about 90 Nm, but the spring on my shock is rated 110 Nm, leaving me with three alternatives: (a) lift heavier weights at the gym, (b) eat more pies or (c) change the spring if it ends up being too stiff at the end. I don't like the yellow colour of the spring, so I'll have it powder coated black together with the frame.

Tuesday, 17 March 2009

Swingarm, part 2.

We [that would be Indiana – the fabricator on this project] have been busy since my last post. And to say that I'm stoked with the results would be an understatement. I did a little "napkin sketch" of approximately what I wanted, and he started twirling the knobs on his CNC grinder. Out came these little tributes to modernism.

The three pieces to the right in the picture is from stainless steel and won't be painted, and will look nice when contrasted with the black paint on the swingarm itself (center left in the picture). The "lid" in the bottom left in the picture is not quite finished yet and will be trimmed along the red lines for a more square look. Next up: bending and mitering the swingarm tubes.

Sunday, 15 March 2009

Gettin' jiggy wit' it.

A big part of building a framer like the one we're doing, is making sure everything is straight. And that means a lot of measuring. And then some more measuring. If you're contemplating a little DIY-project of your own, be advised that you will need some sort of makeshift fixture/jig to keep everything in check while you weld.

I once had a discussion over the phone with a guy called Pegoretti, who is an Italian frame-maker, famous for TIG-welding the frames that a certain Miguel Indurain took to five victories in the Tour de France – even though the frames were painted in the team sponsor Pinarello's colours. During my twenties I literally lived for cycling, and I really wanted a "Pegoretti" frame. I called him and he told me a little about the construction process. He claimed that he didn't use a fixture of any kind. And that he didn't want to clamp the tubes in place but rather keep everything nice and loose, in order to [cue heavy Italian accent] "let the metal live". How cool is that:-)

In the picture above you are viewing the frame from behind, and the square metal plate in the forground represents the spread of the swingarm (in this case 194 mm). The swingarm tubes will be bolted onto the sides of this metal plate before the welds will be layed. More pics soon.

Friday, 13 March 2009

Swingarm, part 1.

OK, we've started manufacturing the swingarm. Yeah, I know we could save a whole lot of work by adapting a standard swingarm from a breakers yard, but I really, really want a round-section swingarm like the ones on NCR's retro Ducatis.

The problem with a round swingarm is that you don't get a nice flat area on the inside of the swingarm where the wheel spacers/brake hanger/axle can sit (see red arrow). Hence the turned pieces that will slot into the swingarm from behind. But before we weld them in place they will be drilled both sideways – to accept the axle and provide a reasonable amount of backwards and forward adjustability – and hollowed out from behind to accept the sliding piece that will hold the axle in place. And of course squared off on the inward facing side. As I said: a lot of work. But hopefully, it will be worth it when we´re done.

Monday, 9 March 2009

Learning by doing [wrong].

A few weeks ago, I wrote the following: "I know the slope of the top tube looks weird, but in order to get the tank to sit correctly it has to look like that." Well, that turned out to be wrong. I don't really know why, but when we had tacked the top tube and the vertical tubes emanating from behind the engine in place, the tank refused to sit anything like what I had planned. It sloped horribly backwards and looked more chopper than tracker. Bollocks.

Now, I strongly feel that in order to look right, the whole profile of the bike has to lean a little bit forwards. Not exaggerated like a German streetfighter, but subtly, to suggest movement. This of course meant we had to detach almost all of the tubing, since raising the top tube had knock-on effects on the the whole frame. Oh, well, now it's back together and the tank sits EXACTLY like I want it to with the bottom of the tank sloping ever so slightly FORWARDS. About 50 mm of top tube (the bit protruding out behind the tank) will be cut once we have attached the sub frame. Which I don't want to do before the swingarm is done and the bike stands on its own two wheels – in order to get the slope of the seat exactly right. I'll be damned if I'm going to make the same mistake twice.

Tuesday, 3 March 2009

Tasty nuts.

Yup, that's their web address: www.tastynuts.com. The company is called Pro-Bolts and I have to admit that I lost myself completely in their catalogue. I must be some kind of perv, but the sight of expertly turned titanium hardware makes me go all weak at the knees. Pro-Bolts sells fasteners made from all kinds of materials and in all kinds of colours. Now, it would be very easy to go totally overboard and colour-code all the fasteners on my bike with the [soon to be] red paint scheme. But I must avoid the dreaded "tarts handbag syndrome", which so often can be seen on the "specials" featured in "Super Bike", "PB" and a lot of other mags (not "Sideburn" of course). Red aluminium engine casing bolts with matching sprocket and disc bolts? No, I don't think so. I think I'll settle for some nice stainless bits and bobs. Oh, and maybe a pair of black anodised pre-load adjusters to match my black Gixxer forks:-)