Sunday, 11 July 2010

What I really need to do is to buy myself one of those big wall planners, and mark in the deadlines for the stuff I write. That way I'd probably spend less of my time in a low grade panic. I needed to do something for an article, so I started making a random petrol tank, and there's only so much metal bashing I can comfortably put up with in one week, and I'm not massively attracted to the idea of doing a job more than once. So, as you might imagine, the prospect of bashing out the third version of the front mudguard for the R65 didn't fill me with enthusiasm.

So, I went shopping instead. I needed some bits and bobs to finish off the rear sets, and chased most of them down on the Internet. I was a little dubious about the left hand thread M6 x 1.0mm stainless steel nuts I bought off of E-Bay arriving in time as it did say "seller usually posts within 5 days", so I stopped off at my local supplier and bought some from them. The Rose joints, two right hand, two left hand thread, were ordered on the Thursday night, and arrived on Saturday, and the left hand M6 x 1.0mm die and die holder were ordered Friday afternoon and showed up on Saturday too. Sadly the other thing that showed up on Saturday, was a hangover.

In some sort of an attempt to rationalise what I was up to, I also decided to do a little more shopping on Saturday, and hunt out a 1930's-40's petrol can, so I could use the neck and brass cap as a filler cap on the random fuel tank I'd started making. The idea being that if I stick with it and finish the tank, then my "To Do" list will have one less thing on it. I did manage to buy two petrol cans, and the forward planning paid off, as I hadn't realised the necks on the can were brass, and I'm going to need to solder them on to the petrol tank.
The upshot of all that was that by about mid afternoon on Saturday, I'd made it to the workshop, clutching two petrol cans, assorted parts for the R65's rear sets, and my head. The logical thing seemed to be to connect the rear sets I'd made to the things that they needed to operate, using the recently arrived bits and bobs and some of the 6mm stainless rod leaning up against the wall by the drill press. Naturally, once I picked up the 6mm stainless steel rod, it turned out to be 6mm mild steel rod.

Luckily Rob has been quite busy lately and was working on the Saturday too. Luckily because one of the things he makes are grilles to protect stained glass church windows from assorted air born hazards, and he makes them out of stainless steel mesh welded to a 6mm stainless steel rod framework. A short walk across the yard, and I had a couple of feet of material to do the job with.

The gear change side of things was relatively straight forward, I cut a thread on one end of the rod, measured it, screwed on a lock nut and the rose joint, and measured from the end of the thread to the centre of the ball on the Rose joint. That told me that with 7/8" of thread, the centre of the Rose joint was 1 1/2" from the end of the thread once the joint was bottomed out. That meant that the centre of the linkage was 5/8" from the end of the rod, and that the overall length of the rod (without the Rose joints needed to be 1 1/4" less than the required centre to centre measurement. Now do you see why the hangover was significant?

I've seen rear sets on Beemers where the controls are positioned not unlike mine, but the brake rod departs from the pedal and travels off to the rear brake. Don't like that, because the rod is so much shorter than the swing arm, not parallel with it, and pivots about a completely different centre, it's all going to be a little prone to conflicting arc issues. Then the ratio of the pedal is all wrong, the standard BMW pedal (or at least the one I have) has a 5:1 ratio, dinky little concentrically pivoted rear set levers make it hard to achieve better than 4:1.

While that lot won't prevent the rear brake from working, it will mean it doesn't work very well. For a little more effort, it ought to be possible to have a rear brake that performs very much like the factory one. My rear set levers have a ratio of 3:1, so I cut the original brake pedal up and welded a piece of 1"x 1/4" strap to it to turn it into a 1.66:1 idler for the brake mechanism. 3 times 1.66 comes to 4.98, and that's pretty close to the original 5.

As well as sorting out the pedal ratio, this also puts the brake rod in the original position where it's pivot is much closer to the swinging arms and the whole geometry of the set up is a lot happier and the rear brake set up now uses the original pedal stop. I might add that while the maths was getting more complicated, the hangover wasn't getting any better...

As you can imagine then it came as something of a relief to go back to making the link rod from the rear sets to the idler. Somewhere in the week, I did find the time to make the ends for the pedals, but apparently I didn't find time to swap the zinc plated Phillips screw holding the two sections of the pedal together for a stainless, button headed Allen bolt. I think it's fair to say that the finished thing looks quite a lot like a real one, though for the reasons I explained, they're going to work better than some of the off the shelf "real" ones you see.

Clearly, the original "bolt-on" concept I had for this project is long dead, but I'd like to think that the reasons for that aren't entirely due to my reluctance to part with money. If I feel I can make something that works and/or looks better, then I'd rather make it myself than buy it. That's not because of some misguided idea that you have to make it all yourself, it's simply because I know what I want, and I'm not compromising that by buying something that's only nearly what I want. The other part of the equation, which may come as surprise to people who watch a lot of Discovery Channel, is that it's better to hit some notional target of right, than it is to have it done in some notional period of time.

Since I briefly touched on the "DIY Nazis" in the last paragraph, I'd like to share a closing thought with you. If it doesn't work well, it doesn't matter who made it, it's still crap.

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