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....