Monday, 31 May 2010

Normally, I arrive at Saturday, and if I haven't managed to do anything to the BMW, I'll do something to it.

I did make a start on the exhaust system in the course of the week, and at least have a clear idea of how to achieve what I want now. The other thing that became apparent was that the workshop badly needed tidying.

Having abandoned exhaust building to sort out the exhaust building environment, meant that Saturday arrived with no real progress made. As I had to fix Mrs.Bridges' car, and had made arrangements for Mr.Lawless and I to go and talk to a man about his turbo charged Harley Davidson, Saturday came and went with no tangible progress made either.

On the intangible front, I had the vague idea that I wanted the exhaust to look similar to the exhaust on the Team Incomplete Boxer, but have built enough exhausts in my time to realise that since I have down tubes on my frame and don't have a deep sump on my engine, similar didn't mean identical.

I got as far as bending up a tube to check that the radius of the former I have for 1 1/2" tube would work and to remind myself of what is and isn't possible with that particular former. If you're not familiar with BMW engines, the right side cylinder is set further forward than the left side one.

I should be able to bend the pipes so that they come out of the head and bend around to the front of the frame where the drop down to form a shallow "V". Where they meet, I'll bend them so that they'll point out of the right side of the bike again, with those bends concentric, and the left side pipe behind the right side one, but pointing up in the air slightly. That should let me bend them through 90 degrees so that they both point back along the motorcycle, with the left side pipe running directly above the right side one.

After the pipes turn to run along the frame they ought to be close to equal length, so I might as well look up the relevant information in the manual and use the calculator here to position the collector. After that, I'll use some 1 3/4" for the tail pipe and and bend that to turn across the back of the engine and exit on the right pointing up in the air for the silencer.

I'd like to do each side's pipe in one piece of tube, but that may not be possible. I'll find out in the week with a little luck.

Sunday, 23 May 2010

Having transited the transitional period, I find to my amazement that I have actually achieved rather more than I thought I would on the BMW front.

Disappointingly, the R80 tank hasn't materialised.

While I was out and about, I did manage to buy a couple of lengths of bar which meant that I had some material to maching the crush tubes for the new rear engine mounts out of. I also bought some 1 1/2" "exhaust" tube.

Some careful calculations showed that by making the exhaust for the BMW from 1 1/2" OD 1/16" wall tube, I would have a former to bend it, and the gas would travel from one end of it, to the other end of it over a period of time. Quite what it's going to do in terms of performance, is a bit of a mystery, but it will almost certainly rob the midrange of something. Given that the later bikes needed bigger valves to make more power, I suspect that a fatter bore exhaust isn't going to tap any unsuspected reserve of horsepower either.

The question is do I care? Well in some larger sense, clearly I do because it's not unknown for me to spend some time measuring valve timings, poking numbers into calculators, and modelling exhaust systems with equal length branches in Google SketchUp. On the other hand, this is a Café Racer, and to my mind the defining feature of a cafe racer is that it looks like a race bike, but goes no better than a bone stock bike.

So, as long as it looks the part, that'll be marvellous.

You may recall that I managed the snap off the threaded collar on one of the exhaust ports? Frankly, I can't be arsed to even attempt to weld it back on, so what I think I'm going to try is cutting the other collar off and drilling the fins for exhaust retaining springs. If nothing else, it'll look more like a race bike...

I took some of the 20mm bar I'd bought and turned it down to 19mm, mostly because I couldn't buy any 19mm bar between the house and the workshop. I also drilled the bar with a 12.5mm hole to accept the lower engine mounting stud. I used a roofing square and a spirit level to chock the frame up something like level on the floor when I drilled some 3/4" (or 19,05mm if you prefer) holes through the frame rails. I drilled the holes 4 5/8" in front of the existing footrest mounts.

Slightly annoyingly, I looked on the shelf for some tube to make a spacer that I was going to cut to the same dimensions as the bottom motor mount, I discovered some 3/4" OD, 1/8" wall tube that I could have just cut the crush tubes out of.

Once I had the crush tubes clamped onto the lower engine mount stud and checked that it was square and level to the rest of the frame, I welded them in place. Next thing was to bolt the engine to the rear mounts and bolt the engine mount forgings that I'd cleaned up so that the engine acted as a jig for the mounts. and I could tack the mounts into place.

Once they were tacked, I took the engine out, and clamped them all up on an engine mouunting stud using the same tube spacer and original engine mount spacers to keep them all aligned, and preheated it all prior to weklding them in place.

By this time, the engine's timing cover was starting to irritate me as it was making hauling the engine in and out of the frame a little bit difficult. According to the manual, it may require some heat to remove the timing cover. In my case a rubber hammer seemed to work admirably. With the diode board (fancy German name for a rectifier) removed, along with the alternator, and ignition "bean can" I got the hacksaw out and cut the top of the timing cover off.
Initially I'd just had it in mind to saw the top of the cover off to make the repetitious process of installing and removing the engine easier. I got a little carried away and after about an hour, I'd shaved off more or less all of the stuff that needed shaving off.

I've been looking askance at the sticky up bits either side of the starter motor that are basically there for the now redundant starter motor cover to bolt up against as well. It doesn't require second sight to see a cutting disc in their imminent future...

I need the fuel tank to turn up now, so I can sort out the frame bracing, and I'm giving some thought to binning the subframe and making a new one in fatter tube.

Having neither the tube or the fuel tank to hand, then I'll probably be making the rear sets and the exhaust over the coming week.

But don't hold your breath...

Sunday, 16 May 2010

As I'm currently going through what is referred to as a "transitional period" I've been struggling to do the stuff I need to do, and that's not left a lot of time for the stuff I want to do. The only saving grace in all that has been that I'm in the midst of all this struggle because I'm rearranging things a little to make my life a little easier.

Since the stuff I have to is indistinguishable from the stuff I want to do to an outside observer, there is a tendency for something to fall by the wayside, and since the best way to make progress, is to make progress, occasionally I have to satisfied with a small victory.

This week's small victories include extracting a solemn promise to deliver a R80 tank to me in the upcoming week, finding the bloody engine mount casting I lost, and trimming one of the engine mount castings (the one I didn't lose) down to usable proportions.

The two lumps of metal in the picture are the rear engine mounts that I cut off of the frame. Originally they were mirror images of each other and were affixed to the bottom of the frame rails. I've cleaned one of them up so it can be attached to the top of the frame rail to act as the front engine mount. Some time in the week, I'll get at the other one and hacksaw, file and sand that to match.
These mounts originally carried the centre stand, and the left hand one of the original front mounts, carried the side stand. Short of leaning the thing against the wall every time I park it, it looks like I'll have to provide for a new stand mount.

The frame itself is going to need drilling for the new, higher, rear engine mounts, and I probably ought to address the lack of stiffness in the frame. While the headstock area is famed for it's lack of rigidity, the swinging arm pivot area leaves a lot to be desired too. I have some sort of a scheme emerging in my brain which involves disposing of the sub-frame and welding on a structure to serve the functions of mounting the seat, attaching the top of the shocks, and stiffening the swing arm pivot area while saving some weight at the same time.

The lack of symmetry in the upper shock mountings is probably the biggest fly in that particular ointment, but if needs must then I expect I can deal with it by making some press tooling to shape the upper shock mounting points. That's something that sounds a lot more exotic than it actually is.

While all of that might sound like I know what I'm going to do, I have to arrange all of it to clear the fuel tank that I don't actually have in my possession yet, but yes, I do have some ideas.

I seem to have run out of 3/4" bar, so I'll have to get some to make the crush tubes for the rear engine mounts, and once I've done those I can use the engine as a jig to affix the cleaned up factory castings as front mounts.

I'd hope to get at least that much done in the course of the next week.

Monday, 10 May 2010

Not much happened to the BMW this week. Well, strictly speaking, that's a lie I suppose, as "Not much" implies that something happened, and in fact, nothing happened. It wasn't a lack of enthusiasm, so much as a return to our scheduled programming that left the BMW unmolested, and this week is going to be more of the same I think...

In the absence of any progress to report, I'll have to settle for mentioning that my workshop is in Bristol, England, and not very far from the site of the old Douglas Motorcycle factory. It struck me that there was a certain amount of irony in that, as I've read that in the aftermath of the First World War, BMW had to find some other product to make as the terms of the Treaty of Versailles forbade the manufacture of implements of war, and it was generally felt that aero engines fell into that category. Which is where the idea of making a motorcycle crops up.

I've read that BMW copied the Douglas motorcycle f the time, and why not, certainly they were used by dispatch riders in the War. Which would make lend a certain irony (or at least a vaguely metallic flavour) to my reworking a BMW adjacent to the site of the Douglas factory.

Sadly, the more I think about it, the less inclined I am to believe it's true. The Douglas of the First World War was a fore and aft boxer twin, and while the later Dragonfly does look very much like a BMW, that's several decades later.

I'm more inclined to believe that if there was any copying, it was the ABC that was being copied. Made by the Sopwith aeroplane company, and not dissimilar to the R23 BMW, except for the BMW having wearing is valves sideways.

I'm sure anyone who is interested enough will know how to Google for more information on the subject, but it was all a long time ago. I'm not going to do it, because I've been too busy celebrating the anniversary of my birth, another thing that happened a long time ago...

Saturday, 1 May 2010

As a general piece of advice on the subject of building motorcycles, have a plan and stick to it, is pretty uncontroversial.

My original "plan" had been to get the R65 running, bolt some Ace bars onto it, make a bum stop seat, and call it a café racer. It fairly rapidly became obvious that the Ace bars weren't going to make for a happy riding position and they've been deleted from the scheme of things. However, the scheme of things now includes rather more than it did to start with, and one of the things it includes is me abandoning my resolution not to mess around with the frame.

For one reason or another, I seem to have mislaid the photo I took of the inside of the R65's fuel tan, which is a shame as it was a bit of a trial getting everything lined up, lit up, and in focus, and I was quite proud of the result. The point being that the tank has to go since it's rusted to the point where it's going to start leaking before long. So rusty in fact that the fuel cap had seized in the threads and required corrective surgery with a large hammer and a cheap screwdriver to remove it. Hopefully I'll have an R80 tank to go on there next week, but in the mean time, I've been looking at a Suzuki GS1000 tank as an alternative.

It is sort of growing on me, but I really would prefer the BMW tank. I think...

If you study the picture you can see that I've shortened the rear subframe, and bolted on some temporary foot pegs to establish the riding position. During the course of the week, I read somewhere that the lack of Ace bars or clip-ons means that my BMW won't be a "cafe racer", because it'll have the wrong bars.

Which is true enough, as it's a café racer, with an accent over the "e". I can see that having ape hangers on your motorcycle and asserting that it is a café racer (with or without an accent) is going to make you look a little foolish. But on the other hand taking a box stock motorcycle and bolting a set of Ace bars to it, doesn't make it a café racer and asserting that it does, makes you look equally foolish.

The point of a cafe racer is that it looks like a refugee from a road race track, and to delude yourself that bolting on a set of Ace bars achieves that must require some very determined squinting.

With all this interest in café bikes, I hear very little mention of Unity Equipe, which is a little odd I think. Check their site out, download the 50 page PDF catalogue and see if you don't think it a little odd too. They even have Ace bars...

As making it look like a race bike is the essence of building a cafe racer, I've been studying pictures of BMW race bikes as well as café bikes, and I've noticed something. That thing where you move the engine forward 1 1/2" and up about an 1" at the back? That really makes a difference to the way the motorcycle looks.

It didn't look like it would be a massive amount of work, and it really makes a difference to the stance of the motorcycle, so I decided to abandon my earlier resolve to leave the frame unmolested and to move the engine mounts to reposition the engine.

I'm curious as to what other people have done with the drive shaft though. I'm leaning towards machining a spacer to fit between the gearbox flange and the drive shaft flange as that will keep the UJ in the original position in relation to the swing arm pivot, but given that there can't be an awful amount of angular movement in the swing arm, and the drive shaft seems to have some sort of a plunge mechanism that might not be overly critical and lengthening the shaft may be an option.

Clearly, as the essential thing about cafe racers is that they look like a racing motorcycle, it isn't necessary for them to go like a racing motorcycle. On the other hand, the earlier R65s like mine made a heady 45HP, and the later ones a dizzying 50HP mostly through having larger valves in the head as far as I can ascertain.

So, now that I've snapped the threaded section that retains the exhaust nut off of the left hand head, I have a reasonable excuse to replace both heads with the later ones and gain 5 more HP...

For the time being, I'll be cutting the old engine mounts off of the frame and repositioning those, as well as looking at stiffening things up a little in general and tidying up the exhaust hangers to do duty as rear set mounts.

If you're wondering, I did fix the brakes, and I did ride it around the yard.

That's why it isn't having Ace bars.