The Horse Latitudes

Between 30 and 35 degrees North of the the equator and between 30 and 35 degrees South of the equator, are what's known as "The Horse Latitudes". I was taught that they were called this because ships were often becalmed there, and any livestock on board would perish and be thrown overboard.

Apart from throwing dead horses around, this period between Christmas and the New Year always feels like that to me and I can seldom muster much enthusiasm for anything other than the traditional seasonal excesses. In the course of the week leading up to Christmas, I did manage to make a new r4ear brake actuating rob for the BMW, but that was the sum total of my productivity I'm afraid. Making a brake rod doesn't sound like much and in all honesty it isn't, but I did manage to make rather more of a meal of it than you might imagine to be the case. The initial intention was to re-use the original item once I'd managed to persuade it to detach itself from what used to be the brake pedal, but is now the idler for the rear sets. That didn't exactly go swimmingly well, and I ended up breaking the retaining clip on the clevis pin, though I did manage to free the stop screw and nut off with out any further displays of ham fistedness. 

A scout around the workshop produced a selection of left hand threaded Rose (or Heim if you prefer) joints with an M6 x 1.0 MM thread. I'm fairly sure that these were originally some thing to do with a gearchange linkage and came to be lurking around when two of the linkages were modified, using a new rod and the right hand threaded joints. As I bought a left hand thread M6 x 1.0MM die to make the linkages for the rear sets, threading the end of some 6MM bar to accept the joint and a lock nut  was simply a matter of remembering where I put the die. Once the new rod was fitted with a pivot and cut to length, I threaded the other end to accept a nut to act as a stop for the spring, and the original brass wing nut adjuster. It's fairly obvious that tapping that much thread along the rod was a fairly time consuming job. What's possibly less obvious is that the spring was quite a time consuming job as well, as I wound it myself. It's actually one of a batch of 10 or so that I made a while ago using the screw cutting facility on my lathe and a couple of simple tools. 

That, in all likelihood concludes the progress for this year, and frankly, I've forgotten what I was planning to do next, so that will have to come as a surprise to us all.

A Christmas get together.

Having had a bit of a rest, I got on and welded up the rest of the frame. I'm not wildly enthusiastic about the result, but it's not going to fall apart. Bits of it are definitely better looking than other bits, which is partly because I don't have the balance I used to, and partly because, I was rushing it and lacking in patience. Still, nothing that a grinder and a more measured approach wouldn't sort out, should I decide that it needs sorting out.

With the welding done, the next major task is going to be sorting the engine out, and with that in mind, I've started looking at the ignition. I'm flirting with the idea of crank fired ignition, simply because it means I can lose the bean can that houses the points. That's little more than a research project at this stage, and the immediate  concern is really an ignition coil mounting bracket, for which I need some idea of the coil I have to mount.

What the motorcycle needs at this point is a penultimate re-assembly to check that everything goes together and works as advertised to avoid unpleasant surprises once everything is painted, powder coated or plated. With that in mind, I drilled some more speed holes in the footrest hangers and cleaned up the last traces of any bracketry that I'd lopped off of the frame and sub-frame. Finding homes, or more accurately, making homes, for the ignition coil, regulator, rectifier, a horn, and the mythical fuse box, before the frame is powder coated or painted, makes a lot of sense to me.

Because of the episodic nature of my motorcycle building antics, combined with the unreliable nature of my memory, I have a tendency to leave minor things undone, and then forget about them. For instance the seat hump needs drilling for some screws to attach the rear light, a task which remains undone as I haven't determined whether too use small screws and nuts, of which I have none, or self tapping screws and speed clips, of which, I am equally devoid. Things like that tend to suffer from the need for them becoming apparent at 5:30PM on a Saturday evening, and my not resurfacing at the workshop until something after mid-day on Tuesday, which is plenty of time to forget what I need, for whatever it is I need it for.

Bad weather, Christmas, and the New Year mean that progress over the next fortnight or so is unlikely, but stranger things have happened.

Raiders of the Lost Parts

Despite the auguries to the contrary, I did actually manage to make some tangible progress on the BMW this week. It started badly with my trying to get some one on the phone who knew about Acewell digital speedos, as I'm a bit unclear about which would best serve my needs, and failing miserably at that.

Havng arrived at Friday slightly tired, dazed, and not entirely sure why I was in the workshop, I turned around and got back in my car, and instead of doing the sensible thing and heading for home, I went to B&Q and bought a length of 12mm threaded bar, and some suitable nuts and washers.

 The reason for buying it was that I couldn't find the original fine thread nuts that went on the two original engine mounting studs, which meant that I couldn't tighten the engine mounts, which in turm meant that I couldn't make sure that the frame splices were correctly aligned. While threaded bar isn't suitable for use as an engine mount, it can certainly substitute for one right up to the point where the engine is fired up. Certainly in the past, I've noticed that people assume that because I've used it while constructing a frame, it's going to fine as an engine mount. The truth is that I use threaded bar for these applications because its' more convenient, the coarser thread saves time winding nuts on and off, and if I damage the thread then I haven't wrecked a stud which will have require more investment of time, energy, and often money to replace. Once I'd cut a couple of lengths of threaded bar, I cleaned up the cut ends of the frame rails and bevelled them and the splices ready for welding.

Aside from the nuts for the engine mounting studs, I'd also managed to lose the steel template I'd made for the gusset to go between the existng factory headstock bracing. At one point on Friday, there were three of us searching for it in what was in increasingly unlikely places. I eventually found the thing in plain view of everyone. I'd left it on the bench with the gussets that I'd already made, and some how it had got knocked off of the bench, whereupon the force of gravity had taken over. I'd suspected this as a possibility and had assidously searched the floor area around the bench in my quest to find the thing. What I should have remembered is that gravity is a very weak force, because on it's way from the bench top to the floor, the template had passed the magnet that lives on the side of that particular bench, and magnetism being a stronger force than gravity, it had snatched the template for its own. Which goes to show, even particle physics can come in handy from time to time.Having found the template, I went on to make version 2 of the gusset, and add it to the collection.

Saturday dawned a much warmer day than had been the case for most of the week. I know that because after I woke up in the middle of the morning, I was told so by Samm, who knew it because she'd looked it up on the Internet. Rolling into the workshop at around half past one, I started plodding my way through the welding, and sorted out the detachable frame rail.

With that done I double checked the headstock gusset gusset, which I suppose ought to be called a boxing plate. as that's more or less what it's doing. With that finessed and tacked in place, I tacked the rest of the reinforcements  in position, then preheated them with my propane torch and welded them.

I mentioned last time that the top tube to down tube gussets were going to hidden by the tank, but that the determined obeserver should be able to spot them, and as you can see in the last photograph, that is the case.

Because I was getting tired and my welding seems to suffer for it, I opted to wrap it up as soon as I started fumbling things rather than press on and do the few remaining bits of welding. I'm hoping I can get that done in the week and then start reassembling the motorcycle to make and finish off any odds and ends of fabrication, before I make a start on the engine as I'm hoping to get the paint and so on done while I'm overhaulng the drive train.

Templates, temper, tempus fugit.

Last week I mentioned that there was something odd about about what I mistakenly called the "headstock/top tube gussets", when in fact I meant there was something odd about the top tube/down tube gussets. I blame the fallibility of the human condition, and the better part of a bottle of wine for the error in nomenclature.

Which brings me to the question, had you noticed the odd thing about the case in point? Admittedly it's not glaringly obvious, but the keen student will have noticed that the lovingly crafted and shaped gussets are going to be concealed by the petrol tank once it's fitted to the motorcycle. The immediate reaction is that must have been a mistake, or that at best, it's a bit pointless adding the decorative speed holes, only to conceal them under the tank.

In fact, it's neither an error, or pointless. To digress a little, back when I was making some effort to produce bespoke frames on a commercial basis, I used to cut out a cap for the open end of the centre post where it protruded through the cross brace, and sand and shape the weld to give a smooth appearance. Anonymous Don once asked me why I went to this trouble, and I told him that it was because the better a motorcycle looked, the closer people would look at it, and that in the fullness of time, someone was going to get on their hands and knees and look at the bottom of the cross brace. This statement, was met with scorn and disbelief.

A week or so later, Anonymous Don and I were attending a custom motorcycle bash, when Don was smitten with a revelation-ette on seeing a supplicant get on their hands and knees to inspect the underside of a motorcycle which was in the car park. Quod erat demonstrandum baby....

Carrying that idea further, in the BMW I'm trying to build a motorcycle that does nothing for the instant gratification seeking, Discovery channel watching, custom motorcycle enthusiast of recent vintage, while at the same time attempting to build one that rewards the patient observer. The more you look, the more there is to see.

Whether I have the ability to bring that off with any aplomb remains to be seen. Although, one would suppose that the advantage of being what is quite arguably insufferably pretentious in a subtle way, is that if you fail to bring it off, no one is necessarily going to notice. Unless you post that intent on the Internet of course...

So, while the speed holes in the top tube/down tube gussets will be obscured from casual view, I want the determined inspector of nooks and crannies to be able to spot them.  With this in mind, I've decided that I'll have the tunnel of the fuel tank satin black, allowing the silver painted (or powder coated in all probablity) gussets to contrast with their back ground, and that the gusseting on the headstock gussets needs to be, to paraphrase somebody famous on the subject of aircraft, a collection of holes held togehter by small pieces of metal.

As you can see, the steel gusset I made from the card template, had a fairly high ratio of hole to metal. sadly it didn't actually fit that well. More accurately, it didn't fit. at all. For some unaccountable reason, possibly not entirely unrelated to a somewhat unmerited glib attitude as a result of having done this several thousand times before, I neglected to offer the steel blank up to the frame to check that it was the required shape.

This was a bit of a shame, as it emerged that after I'd spent most of a day working out the hole spacing, checking that I had the requisite drill bits to drill the sequence of holes I'd arrived at, marking the hole centres, pilot drilling them, and then drilling them to their final sizes, the gusset, didn't fit. I suspect that what happened was that in the process of manipulating the card I used to make the template into position, I managed to pull the lower edge of it off of the line that ran between the edges of the factory fitted gussets I was planning ion boxing in.  The second picture, fuzzy as it is, shows me holding the second template I made for the gusset in situ. Despite the fuzziness of the illustration, it ought to be clear that the template isn't made of card, it's made of steel.

While it's only made of 18 gauge steel, this newer template has sufficient stiffness that it is reluctant to bend in one direction under hand pressure, let alone two directions. A closer look at the third picture should give you an idea of how much wider the gusset was that the space it had to occupy. Normally that wouldn't cause a huge problem, but as I'd already drilled the speed holes in the gusset, trimming it's edges down would have destroyed all my careful worked out hole spacing. The moral of that could be assumed to be that occasionally, the harder way, is easier, but I feel that the truth of it is that the ability to spot when you should be making a little more effort sooner rather than later, is an ability worth cultivating.

Christmas is approaching, and aside from all the usual seasonal mayhem, that also means that magazines want their stuff somewhat earlier in the month than is usual, so the next few weeks don't bode well for progress on the BMW...

By all that's Holy....

It's all very well to blithely say things along the lines of "drill some speed holes in it.", but that ignores the time and effort that goes into working out the positioning of the holes, and then measuring and marking out whatever scheme of spacing you arrive at.

Drilling some holes in an existing part, or a part that has to fabricated, but has a size and shape that is going to be defined by the job that it does, such as the new rear upper engine mounting plate that I've concocted, imposes some limitations, and provides a place to start if nothing else. Since I'd decided that I wanted speed holes in the gussets that I was going to add to the frame, and the size of the gussets in two of the places where I felt a little stiffness could be added wasn't critical. That being the case it made as much sense to size the gusset to suit the speed holes, as to take any other approach.

Because the main loop of the BMW frame is more or less a rectangle, it will be prone to lozenging. Since the front down tubes are attached to the top if the headstock and the top tube to the bottom of the headstock, what will tend to happen is that under braking when the bottom of the headstock wants to move backwards, the only thing stopping the top tube moving relative to the down tubes are the gussets from the down tubes to the headstock. Much like the Norton Featherbed frame which is said to have inspired BMW's engineers in the design of the Airhead frame, racers tend to adjust the steering head angle by the simple expedient of crashing the motorcycle gently into a wall, which is enough to "tweak" the frame and reduce the headstock angle, and in turn quicken the steering. Good isn't it?

I feel it's obvious that adding a gusset between the top tube and the down tubes will stop most of that from happening, but to my mind it also makes sense to box in the bottom of the factory headstock gussets as well, since that would stop them from flexing, which is what they'd have to do to allow the sort of motion I've been talking about.

The other area where I feel the frame is lacking is the swing arm pivot area. The anecdotal evidence would suggest that a beefier sub frame that was welded to the main loop would improve the handling. For that to be so, then the problem must lie not with the sub frame, but with the rigidity of the swing arm pivot area of the main loop. The tubular bracing should address some of that, but adding some gusseting to the area should not only enhance the stiffness, but provide yet another place to drill some speed holes.

The gusset that will run from the brace bar to the lower rail presented a slightly different design problem. The rear most edge of it had to be the shape that it had to be, but the leading edge wasn't quite so constrained, with the overall extent of the thing being more severely defined than for the headstock gussets. In essence, I traced the shape of the rear of the gusset onto some card, fiddled around with some hole layouts, and allowed the sequence of holes to define the leading edge of the gusset.

In the last picture, you can see three pairs of gussets. To the left are the swing arm pivot gussets I just described, the pair in the centre are the down tube/top tube gussets, and the last pair are to tie the cross tube beneath the swing arm to the lower frame rails. The point of the last pair being that they should contribute to reducing any tendency towards fore and aft movement in the swing arm pivot points.Especially if one side is heading fore, and the other aft....

That of course leaves the boxing plate for the bottom of the standard headstock gussets, which I haven't made yet, and may lead you to enquire just what it is I've been doing all week? Well, just making the headstock/top tube gussets consumed a day of my time, and the other day of this week that I could devote to things BMW was consumed in making the swing arm pivot area gussets. 

Aside from the entire thing taking for ever and a day to carry out, I'm quite pleased with the look of the gussetry I've made, and at the risk of belabouring the point, you are likely to spend more time looking at a project once it's completed than the amount of time that you are going to spend working on it, so rushing through things makes very little sense.

Talking of looking at motorcycles, I wonder if you noticed the curious thing about the headstock/top tube gussets? More on that later perhaps....

Wisdom, the ultimate, and the infinite.

 If you've been on board this particular bus since the month of July, you may remember that I cut the original BMW brake pedal up and welded a chunk of steel to it so that it could act as an idler in the linkage between the brake pedal and the brake proper, serving to correct the pedal ratio and place the final operating rod in a position where it's arc of movement wouldn't conflict with the arc of movement of the brake and thus ensuring that the effect of suspension movement on the brake actuating mechanism was minimised to the point where it became negligible.

If you don't recollect the occasion, this picture should refresh your memory. While it all appears to work, with the wisdom conferred by hindsight I think it's fair to say that it's not the ultimate in infinite beauty. As you should be able to see in the picture to the right, taking at least one leaf out of Phil Irving's book (of which I own several, and so should you) I thought I'd add some lightness, though I settled for making it look a little more elegant rather than "simplicate" it, and in truth, I only added some lightness where it showed.

In my time I've seen seen quite a lot of motorcycle parts that have had lightness added through the ever popular medium of holes which have also had unsuspected quantities of weakness added that led in turn to them acquiring substantial degrees of brokeness. Drilling "speed holes" is largely a waste of time, in most cases you can easily engineer something of equal strength to, and far lighter than, the original, but it has to be said that drilling unnecessary holes in motorcycle parts practically screams "racing motorcycle".

Lest you think that all this is the lead up to another pathetic excuse for not progressing the work on the frame, I give you another picture that ought to dispel any such notion. Careful study of the afore said will show that it wasn't just the rear brake mechanism that caught a dose of lightness, as the crankcase is looking positively anorexic too. The other item in the illustration which is adorned with holes, is the new engine mount I've added. The thinking behind it is not entirely uninteresting I feel. It's fairly obvious that the frame has had some attempt at triangulating it in addition to the main tubes I bent up for it, but it's equally clear that the brace tubes aren't perfectly triangulated and therefore don't appear to offer the ultimate in stiffness.  Oddly, they probably do offer the ultimate in stiffness, what they don't offer is infinite stiffness.

Possibly you feel an explanation is in order? Then I'll attempt one. Considering the frame as a separate entity, it's subjected to assorted forces which are transmitted to it via the forks and the swing arm. If for a moment we simply assume the forks and the swing arm to be infinitely stiff, then the limit of the forces that can be applied to the frame is the limit of the forces that can be applied to the forks, and the swing arm. And those forces are applied by the tyres.

Which ought to make it obvious that the unrelenting pursuit of stiffness to resist forces much greater than those which the tyres can handle, is not only a waste of time, but adds weight. So the considered wisdom should be that the ultimate in stiffness is sufficient stiffness to resist all the forces likely to be applied this side of the ditch, while saving the weight that infinite stiffness would require...

With that in mind, I happily compromised the geometric purity of my additions to allow the fuel tank to fit over them without requiring modification.

I'm reasonably sure that the solution I've arrived at will require more force to deflect it from the true and righteous path than the skinny tyres are capable of generating. Sadly, BMW saw fit to mount the engine off of the lower rails, and my reinforcement of the existing structure does nothing for them, but at the same time makes it impossible to remove the engine. That whole pot of woes is further stirred by the engine being repositioned so that it is impossible to change the oil filter without removing the engine from the vicinity of the right hand lower frame rail.

Using the same logic as most other BMW modifiers, I'd elected to make the lower rail on that side removable which would not only facilitate removing the engine, but allow for removing the oil filter without taking the engine out of the frame as well. Sadly, it doesn't take Werner Von Braun, or any other rocket scientist, to realise that as the engine is held in the frame by mounting it to the lower rails, removing one of them is going to make for a fairly floppy engine. Not only that, but the engine experiences a torque reaction around the drive shaft, which causes the top of the engine to want to move to the right of the frame under hard acceleration.

Hence my top engine mount, which I freely admit to having copied in principle from somewhere German, although I forget where. As well as feeding the torque reaction into the additional bracing , the upper engine mount serves the purpose of supporting the engine while the right hand rail is removed for routine oil filter changes. Not to mention providing somewhere else to drill speed holes.

With everything as welded as it could get with the engine in the frame, I set about removing the engine from the frame. Somewhat unusually, I had to cut the rail off the frame to allow the engine to be removed. With the offending (lower right hand) chunk of frame rail removed, I was slightly alarmed to discover that it was what we in the trade like to refer to as "stupidly thick" in the wall department. So much so, that the Suzuki Bandit frame splices I hoped to employ wouldn't fit into the bore of the BMW frame tubes. After a quick visit to the lathe, the Suzuki splices slipped into the bore of the BMW tubing with only the lightest of hammer blows. As a job, perfectly doable with a file, should you wish to adopt a similar strategy at any point. Since the frame splices were something on the order of 65mm long when installed, I took the trouble to mark the frame with two lines around 65mm apart, before hacking the rail out of the frame, ensuring that the cut I made was between the marks that denoted the extent of the frame splice. Accordingly, once the chunk of rail was cut out, I trimmed the cut ends back to those marks, and reassembled everything with the inclusion of the frame splices.

Since I rambled on about artificial, self imposed dead lines in my last diatribe, it was at that point I decided to call it a day and head off to the wonderland that is Tesco in the run up to Christmas and lay in some provisions for the weekend, leaving the final fettling of the frame rail and the last of the welding for next week.

I

Rush hour.

I'm writing this on Sunday evening and the smell of roasting crown of duck is wafting in from the kitchen. The reason that the smell of roasting duck is wafting around is that I didn't make any progress on the BMW. In TV land, when motorcycles are being built, there is always a deadline, and somehow that idea, along with "themes", seems to have attached itself to the subconcious of the viewing public like some variety of psychological leech.

I'm a little suspicious of self imposed dead lines for leisure activities. I'm working on the BMW because I quite enjoy the process of working on the BMW, so why should I be in a hurry to finish working on it? I can understand that some people may build motorcycles because they want other people to admire their handiwork, and that they're building motorcycles because they like showing off. Some people even seem to confuse having their handiwork admired with being admired themselves, I've noticed. In that case I suppose the need to have the motorcycle finished for this, that, or the other show, gathering or event where people congregate in large enough numbers to admire the finished product makes a certain sort of sense, and the inevitable, "we nearly didn't make the dead line..." anecdote is all part of that too.

I find enough stress in the course of a day to keep me well supplied in that department, so I'm not going to start applying it to my main leisure activity, which is building the BMW. As I've mentioned before, much of what I want to do is indistinguishable from what I have to do to an outside observer, but the main difference is that it's doing what I have to do that keeps a roof over what I want to do.

So, my point is, that at six thirty on Saturday evening, having done most of what I had to do, I decided that the BMW can wait until next week before I get on with the frame, and as a consequence of that decision, I made it to the supermarket in time to snag the last crown of duck they had on the shelf.

Quite what the moral of that is, I'm not sure, but I'll give it a little thought as I enjoy my duck, with roast new potatoes and garlic, washed down with what promises to be a half reasonable claret.

...and just coming into the frame....

I've made a start on the frame at last. Having mentally sorted through various options, I've decided on welded in bracing with a drop out lower rail for the purposes of engine removal, and more importantly, oil filter replacement. The problem with that is that the engine is only attached to the frame with two studs, and those would have to be loosened to remove the frame rail, which would leave the engine hanging on two studs through the left hand rail. I rather suspect that wouldn't do the studs much good. To remedy that I thought I'd utilise an idea I saw somewhere else and add a mounting plate from the top two gearbox mounting studs to the frame bracing rails.

As I've mentioned before, I want the motorcycle to look like a BMW that's off to the races, and not like a racing motorcycle that happens to have a BMW engine in it. With that in mind, I bent up a couple of tubes that would run under the fuel tank and then drop down to meet up with the swinging arm pivot once they were clear of the carburettors and their air filters. Bending the tube didn't present much of a problem as my principle tube bender is a serious industrial piece of kit intended for series production work

I used one and a quarter inch 14 gauge CFS 3 tube for the braces because the front down tubes are that diameter. However, the brace tubes also meet up with the tubes that run from the swinging arm pivot up to the frame's top tube, and those tubes are one and an eighth of an inch in diameter. Not only that, but they're ovalised where they meet the swinging arm bosses, narrowing their width even further. This was all going to make the joint with the brace tube quite interesting, even without the three quarters of an inch tube that runs just above the swinging arm bosses getting in on the act.

Which is why, although I have a serious tube bender, I don't have a tube notcher. It took me about half an hour to cut the mitres by hand using a hacksaw and a selection of files. My theory is that if you cut tube joints by hand you tend to develop a "feel" for the job and even oddball examples like this one become much less trouble, and cutting simple ninety degree mitres takes so little time that setting up a tube notcher would probably take longer.

With the brace tubes shaped, I cut and mitred a cross brace that will eventually support the top mountings for the torque plate from some more one and a quarter inch tube, and after rummaging around a little I found some offcuts of one and an eighth inch tube to tie the tops of the brace tubes to the rear of the engine cradle.

The idea is that there'll be another inch and a quarter cross tube between the brace tubes at (or close to) the points where they're tied to the rear of the engine cradle. From either end of that cross tube another pair of tube will run up to meet the top tube, at (or very near) the point where the brace tube from the front of the frame meets it.

Aside from that, I want a pair of gussets tying each of the down tubes to the top tube where they cross, a cross tube under the frame where the original footrests mounted, box in the front of the factory headstock gussets, and a gusset arranged so that there's something other than the swinging arm boss tying the top and bottom of the frame together.

While I haven't perhaps cut as much tube as I would have liked, I have gone from a vague idea of what I was after to a fairly concrete plan, albeit one that exists only in my head. It should all be fine, as long as I can remember it all....

Not the end, but a place from where you can see the end.

I'd like to announce that the whole on-going seat catch scenario has reached a resolution. Rather amazingly, the resolution it has reached is one of completion as opposed to one of the far more sensible file under "B" for "binned" variety. As you may know, the actual catch part of the equation was made some time ago and seemed to function admirably, and the metal base for the seat has been knocking around for a while too. What was lacking was a means of operating the catch to effect the release of the seat base.

The major part of that problem, at least as far as I was concerned, was the bracket. A few  moments thought should make it clear why. Essentially, the bracket has to attach the number plate to the seat hump, which in itself is a simple enough thing to achieve. The Construction and Use regulations (and the M.O.T) also require that the number plate be illuminated by a white light, and that that light shall not be visible from the rear of the vehicle. So, the bracket has to carry the number plate, and the number plate light, right? Well, yes, but....

The idea, as you may recall was to have a concealed seat release mechanism, with the operating lever concealed behind the number plate. That tends to imply that the bracket would also have to support the operating lever.

It doesn't end there though, as not only does the bracket have to support the lever, it has to provide a cable stop so that the lever has something to operate against, and while it's at it, it has to provide for routing the cable in a fashion that's discrete and doesn't force the cable through any overly tight bends which would impair its operation. On top of which, it would be nice if this masterpiece of design was as near to completely innocuous as possible. Oh, and it has to position all of the a fore mentioned items in a region of space that the rear wheel isn't going to occupy at any point in the proceedings.

If you stop and take stock of all that, it's actually quite a complex design brief, but for a moment let's just consider the operating lever. Clearly it has to operate the seat catch, and it's going to have to do it through the medium of a Bowden cable as do many other things on a motorcycle, what's not stated in the "design brief" is that it's really quite important that the lever doesn't rattle. At the same time, it would be nice if the effort required to operate the lever was such that you knew you were operating a lever without it being a struggle to operate.

  

This is where the elusive concept of "build quality" slips in. It needs to be pointed out that build quality is not a conspicuous feature of many thoroughly enjoyable, exotic, and (it has to said) Italian cars. So, by the same token, it ought to be perfectly possible to build a motorcycle which was complete rubbish, but, at the same time, fun. Since, almost by definition, that wouldn't involve spending four weeks of your life making a seat release mechanism, it certainly has a lot to recommend it. On the other hand, there is something to be said for the satisfaction of a job well done, or even a ludicrous target set and met. The target I set myself for this particular motorcycle was that it ought to have an air of "factory" about it, more suggestive of low volume production than of a one off built in a shed.

Literally on the other hand though, the more observant will have noticed that the release mechanism is "left handed". This is because, I am.

When I've been prototyping things in the past, I've made left handed prototypes so that I could assess how easy they were to use, and then mirror imaged them for the production version. Strictly speaking, I suppose that means that there never was an actual pre-production prototype, but it seems to have worked out quite well on the whole.

While it's easy enough to sit here and pontificate on the merits of design philosophy and assert that one's seat release mechanism was a success, I suppose we live in an age which is a little more "show me" than that. So in keeping with the spirit of the times, here's a rather gloomy video of it all in action...

Hopefully that should mean that some far more interesting frame related things are next on the agenda.

Last time, I mentioned that some sort of workshop tidy up was in order. The agenda also turned out to contain some "crashy" FJ1200 forks and another heavy cold. Marvellous.

However, driven by a deep seated guilt at having failed to do anything of note last week, I did batter away at it and make quite a lot of progress on Friday and Saturday. I say quite a lot of progress, but to the casual, or even interested, observer, with it parked in the workshop the motorcycle appears not to have changed very much. That sadly, is the nature of having a concealed seat release mechanism, very few, if any, observers are going to spot it if it's any good. People queueing up next to the motorcycle and exclaiming, "I say, take a look at this chap's cunningly contrived concealed seat release..." tends to indicate that the level of concealment, may leave something to be desired. 

Having cut a couple of pieces of 1" by 1/4" strap steel to make the hooks for the front of the seat base, I drilled a series of holes n the seat hump, which I suppose would be more accurately referred to as the seat base base, but I feel calling it the seat hump, is a little clearer. After I'd drilled the series of pilot holes out to something like six and a half millimetres, I filed the resulting gash it it more nearly resembled a hole. The idea being the the pieces I'd cut that were going to form the hooks for the front of the seat base would be drilled and tapped with an M6 x 1.0mm thread, and the seat hump drilled to allow them to be bolted to the seat humps inner face. With the three holes drilled in each of the "hooks" (two for the fixing screws, on for the "hook") I transfer drilled the seat hump, and then opened everything out to the right size, and tapped the threads in the hooks. That let me assemble the whole thing, and with the seat base fitted to the hump, I could turn whole assembly upside down, and drill through the holes that were going to form the eyes of the hooks into the seat base and locate the holes for the pins that were going to attach to that and locate it on the hooks.

 That all worked out according to plan, except for the bit where I was meant to take some photographs of it all to illustrate this ramble with. I blame the head cold for that. As a consequence, this last picture is of a block of aluminium I drilled to make a mould for casting the nipples for the seat release cable, directly onto the cable. The round thing at the right of the picture is a ferrule I machined from stainless steel for the cable I was thinking of using. I've decided that the job requires something a little less heavy duty though, so I'm thinking of acquiring a bicycle brake cable to do the job.

Rather than just have the seat release cable dangling under the hump, I think it makes more sense to incorporate some sort of a handle into the number plate mounting bracket. Between my desire for the bracket to incorporate a handle, and the Construction and Use Regulations requiring the number plate itself to be illuminated by a white light that isn't visible from the rear of the vehicle, that's starting to look like quite a complicated bracket.

Once again, another week has slipped by without me getting anything done on the Beemer. Frankly this would be a disgrace if it weren't for the other projects I've got on the go. It has to be borne in mind that I'm also building a tricycle with an Alfa Romeo engine, a GS 550 chopper, and usually something else as well, of late, making a Mustang fuel tank from some sheet metal and a tree trunk.

Next week isn't looking too great either as I need to tidy up behind myself.

I'll endeavour to squeeze some Beemer Werken in between the tidying up.

Honest.

I could have made a simple tag from 1" x 1/8" and a knurled thumb wheel, and just used those to locate the seat base on the motorcycle, but I'd decided I wanted something a little more "factory". It's taken me a while to get around to it, and you might be wondering what the big deal is, after all, how hard can it be to mount a seat? Well, if you've decided you want a concealed, cable operated, spring loaded catch and can't find a suitable ready made one, then quite hard enough would seem to be the answer.

The first problem was finding a spring, but since this is a perennial problem (in the past, I've ended up winding my own...) I bought a box of assorted compression springs from Screw-Fix for a shade under £9. These ones in fact. While rummaging around would undoubtedly turn up a suitable spring in the workshop, one piece of revealed wisdom that I am privy too is that in the course of this sort of exercise, the spring will inevitably go flying off. The question is whether you manage to find it exactly the same number of times it does this,  or one less. Since most of the other components will tend to be sized to suit the spring, losing it, is a bit of a disaster. Unless you have a box full of them.

This is what I made. It's basically a couple of pieces of bent sheet steel and some 8mm square section steel. It all looks simple enough, until you start thinking about how to bend the steel to make the section in which the "bolt" runs back and forth and the spring is housed. The simpler piece was easy enough to bend as I have a box and pan folder, a crush folder, and a vice and a largish hammer, any or all of which would suffice to manufacture the easy bit. Making the other part by bending it, when there are four bends that are 8mm apart, would have been something of a challenge. Luckily, while I may get a little carried away in the design complexity department on a fairly regular basis, I'm not overly fond of making hard work for myself, so instead of jury rigging some sort of arrangement to bend the required section, I cut a couple of squares of 1/4" plate and welded on a length of the square section steel to one side of one of those, and a short length of 25mm bar to the other side of it, and a further two pieces of the 8mm square section, spaced apart by 8mm plus two thicknesses of the sheet steel I was using to make the catch body. As well as the folders, I have a fly press, and pressing the section out was going to be a lot easier.

In the first picture you may notice that the "tongue" of the catch has a rather pleasing chamfer to it. Sadly, I managed to snap a drill off in that one, so the tongue in this picture is another one that I decided to drill for the cable nipple and thread for the stop before I got Trevor to file another pleasing chamfer. The components are (from the top left, going clockwise) the easy bit of the catch body, the bit of the catch body I made the press tool for after it had been drilled for the BA bolts that hold the catch together and the slot for the travel limiting slot filed out, the spring, the new tongue drilled for a cable nipple and the M4 stop screw, the stop screw itself with the silly little spacer that keeps it from tightening up onto the catch body, and the four BA screws and nuts that hold the whole thing together. The spacer under the stop screw was cut from a piece of 6mm OD 1mm wall aluminium tube that I bought from B&Q (think Home Depot if you're American) to make some grilles for the side panels on my GS550 chopper, which look a lot better than they sound. Cutting 2mm off of the end of a piece of flimsy aluminium tube was quite an interesting experience...

With all of the fiddly bits made and working properly, I marked and drilled the seat hump to accept the catch. I used pop rivets to locate it because I didn't want the fasteners to protrude any further from the mounting face than they absolutely had too, and frankly, I was getting a bit pissed off with all the fiddling around and wasn't really in the mood to make some dies to press countersink dimples into everything. Once I'd filed a square hole in the seat hump and the catch was riveted in place and working correctly, I marked the seat base and drilled some 1/8" holes in that which were definitely in the vicinity of the tongue of the catch. Once I had a hole and could see where the tongue of the catch was than it was simple a matter of finessing the hole in the right direction until it was both square and aligned with the tongue of the catch.

That still leaves me needing to make a cable, a handle to operate the cable, some sort of locating arrangement for the front of the seat base, and file (or get Trevor to file) a chamfer on the tongue of the catch, but since it all works after as fashion already, I don't see that as a huge problem.

Though, I may need an extension spring for the release handle.....

Well, Wales was nice, my Dad seemed quite pleased with his present, and I borrowed a few books off of my Mum relating to my house building aspirations. Didn't actually do any BMW though.

I did poke a few pieces of steel in a desultory fashion, and wander around looking for the springs that I'm sure I've seen in the last couple of weeks, and even got as far as sawing off a length of 10mm square bar with the idea of making the tongue for the seat catch, only to discover that the compression spring I had was 12mm in diameter. It wasn't an insoluble problem, but it would have meant a lot more work for a less efficient finished product. The idea of expending extra effort to make something that works less well because I haven't tracked down either a spring to match the metal, or some metal to match the spring, seems fundamentally stupid to me. As I had some other things that needed working on to meet a real world deadline (as opposed to a self impoosed, blog related one) I didn't manage to find the time to run around, source and acquire what I needed. I suppose I could have made a start on the frame braces, but I find that having a motorcycle project with too many unfinished jobs on it is depressing. You reach a point where you feel there's not much left to do, and remember that there are in fact lots of little things left to do, so not only is it a long list but it's all the jobs that you couldn't muster the enthusiasm to do at the time.

On the other hand, if you stick to getting the irritating, fiddly little jobs done instead of rushing ahead and doing something you're looking forward to doing, then you (or at least I) are more highly motivated to get the job at hand finished.

With that in mind, I'll leave you there and hope to have the seat base sorted out in time for next week.

The sum total of this week's progress was that I finished making the seat base. That's not to say that I sorted the mounts for it out, just that I made the seat base. In fairness, it is a little more complicated than your average custom built seat base, and it is going to get a little more complicated yet. Since assorted electrical items (mainly the fuses and the battery) are located under the seat, then to my mind they need to be easily accessible. Given that the R65 doesn't have a kick start, and I have a dodgy leg that rather precludes a running bump start, in the event of a flat battery, it would be far less of a disaster if all that was required was a set of jump leads and a slave battery, rather than the use of a complete tool kit to remove sufficient parts of the motorcycle to gain access to the battery. Which is why I've got it in mind to make some sort of latch and catch arrangement to mount the seat. The front of the seat hump has been cut away to provide access to the battery, and the current theory is that the base proper will get some sort of hook arrangement at the front, arranged so that the font of the seat base hooks on, and then the rear is pressed down and a simple spring loaded catch locates that.

While that sounds over the top, I'm fairly sure that the ability to change the light fuse at three in the morning, in the rain, without using any tools, is something that can only truly be appreciated at three in the morning, when it's raining, the lights fuse has just decided to shuffle off this mortal coil and you don't have any tools. In other words, I feel it's not enough for a motorcycle to be nice to look at, it ought to be nice to use too.

As I may have mentioned before, you ought to spend more time riding a motorcycle than you did building it, so it makes sense to invest some more effort in building it if it's going to make using it free of irritations and niggles. Fundamentally the question is, who are you trying to gratify? Passers-by, or yourself?

The result of applying those parameters to designing the seat is that it's quite a complex fabrication, the design and manufacture of the seat hump was less straightforward than it could have been, and the whole thing has taken for ever. That said, it's not uncomfortable to sit on the bare base, which bodes well for the levels of comfort once it's upholstered, and I'm quite pleased with the way it looks so far. I've still got to make the latches and I'll probably have to make the catch too, along with some sort of cable release and a back up for that which is either going to take for ever, or not very long, partially depending on whether or not I can remember what I did with the pack of compression springs I remember having about the place.

I have a tendency to look at the Beemer all week, without doing anything to it, and then have a bit of a flurry on saturday so I have something to write about here. Next weekend though, I'm off to visit my parents so there won't be a saturday in the workshop. Which limits the chances of my actually achieving anything somewhat...

This week, was mostly about not succumbing to temptation. I took a day out and drove around a little, caught up with a few people and bought a brace of Suzuki Bandit lower frame rails, pictured to the left. These are bolt in to make engine removal either easier or possible, I'm not sure which as I've never taken the engine out of a Bandit. The point is the the half lap frame splices will fit together. OK, there's a round hole that won't quite accommodate the 17mm AF nut that us Europeans like to use for 10mm thread bolts, but that's nothing that a simple spacer wouldn't sort out, or possibly some Japanese style 14mm AF 10mm nuts. I'm leaning towards making some long nuts from hex bar and turning one end of them round on the lathe to fit in the recess in the splices.

The temptation I was avoiding was to start work on the frame braces. I have the tube on the shelf, and I'm happier messing around with frames than I am with anything else. As it was I managed to restrain myself to cutting some of the splices free from the Bandit frame rails and making a start on cleaning them up. The two that are bolted together are from the front and rear of the rail, and have a shorter "tail" than the other one which is from the tube that runs across the frame. Not having inspected any of this too closely before buying the parts, I had been expecting to get four half splices from the two rails, and not six, and I'd also imagined that the tails of the splices would be longer. Having acquired a half dozen half splices, it makes sense to think about using one pair on a cross brace in the same manner as the Bandit does. Of course, while the OD of the Bandit and BMW tubes are the same, as yet I have no way of telling what the wall thickness of the BMW frame is, though the R65 frame is purportedly lighter than the frame for it's larger brethren, so possibly has thinner wall tubing.

What I needed to be doing was finishing off the seat hump. Although I'd made the risers for the seat hump to attach to, and indeed drilled some mounting holes, I hadn't addressed the problem of attaching the front of the hump to the riser. Accessibility was the problem, with the nuts tucked up inside the "U" section of the seat riser, and the battery living right next to that. I don't like using captive or welded nuts on frames as it's always a problem if they strip or seize, so I made a pair of small aluminium blocks instead. These were sized to sit up in the "U" of the seat riser, and drilled and tapped to accept a M6 x 1mm bolt.

As well as that, they were drilled through the other face to accept a split cotter pin. The idea being that they were positioned under the seat riser, and the cotter pin passed through some holes drilled in the riser to retain them in place, allowing the seat hump to be placed and the front two mounting bolts fitted. While it's a fiddly thing to make, if the thread ever strips, or the bolt ever seizes and snaps off, removing the split pin will let the block drop out and it can either be repaired or replaced without any damage to the frame. It might sound like over thinking the job just a tiny wee bit, but I absolutely loathe having to sort this sort of thing out when it goes wrong in service be cause someone, somewhere, was too cheap, or too lazy to come up with an answer that had a less troublesome failure mode. Probably a bit of a hobby horse of mine really...

I also made some inroads into making the seat proper, and gave some thought to how that was going to be attached. I'm making it with 1/4" of the steel folded back on itself at the edges, the idea being that the vinyl can be glued and tucked back behind the folds, and then they can be tightened up with a rubber hammer trapping the vinyl in place. Well, if the seat's removable, it ought to look tidy underneath too. Hopefully, I'll get the seat base made and mounted in the course of the week, which will mean that the following week, I can give in to my baser desires, and start bending some tube.