The amazing journey by Butler & Smith BMW to build championship-winning superbikes out of BMW flat-twin touring bikes in the 1970s. First 750cc, then 900cc, we look at how BMW won the 1976 AMA Superbike Championship. Editor-in-Chief Mark Hoyer joins Technical Editor Kevin Cameron, who recalls his time with builders Udo Gietl and Todd Schuster to explain the amazing transformation of these motorcycles into the remarkable high-performance machines they became. Unbelievable detail here, folks.
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SportsTranscript
00:00Welcome back to the Cycleworld podcast.
00:02I'm Mark Hoyer, Editor-in-Chief,
00:03and I'm with Kevin Cameron, our Technical Editor.
00:07This week, we're gonna talk about BMW
00:12Superbikes, not Top Racks.
00:15Regga, his name, the guy, you know,
00:18out there crashing World Superbike on an Inline-4
00:21street bike with regular turn signals
00:23and telescopic fork and all that stuff
00:25that BMW changed to make a spectacular Inline-4 Superbike.
00:29But we're going back in time to the,
00:31what do we call it, a 180-degree V-twin?
00:34Yes, that's it.
00:37The Butler and Smith era, Udo Giedl,
00:40and, you know, the kind of glory days
00:44and birth of Superbike racing.
00:46They started with a 750 and then later went on to the 900
00:49and had some real success with those bikes.
00:54This is germane to the timings of, let's see,
01:00my fall date at Barber Vintage Motorsports Park,
01:07sorry, Barber Motorsports Park for the vintage festival,
01:11October 11th to 13th.
01:14The Executive Director of ARMA,
01:17through probably some severe arm-twisting
01:19from BMW North America,
01:22has graciously agreed to provide me with a 750 flat-twin,
01:28an R75 slash five,
01:32built in the spirit of the early Butler and Smith bikes.
01:36They're gonna let me race that down at Barber this fall.
01:39Like I said, that's ARMA,
01:41American Historic Racing Motorcycle Association,
01:44and Dan May is the Executive Director
01:46and he's, you know, he's gonna cut me loose on his bike.
01:50So we're gonna cross our fingers and, you know,
01:51talk to Alpine Stars about an airbag suit.
01:55Not gonna use it.
01:58Don't mind having it.
02:00But that's, you know, it was part of my interest
02:03in talking about the Geedle efforts and not,
02:06and actually, Kevin, it goes back to a story
02:09you did in Cycle, the magnum opus on the BMW effort
02:13from the time it was, as Cycle did in those days,
02:17it was a massively long story,
02:19just dense with words, just everywhere.
02:23And one of the-
02:24Well, they were fattening that pig for sale.
02:27Yeah.
02:32One of the lines I remember about it is that
02:34you were writing about the bike running on the dyno
02:38and they were, I think, losing power
02:40or they weren't making the power that they thought,
02:42you know, after beefing it up yet again,
02:44and we'll get into the technical details,
02:46but I think they strobed the motorcycle.
02:51Little strobe attack opens up like an old folding
02:59cell phone and inside is this little flasher
03:02and there's a big dial and you can turn up the speed
03:05and you can also synchronize it
03:07to an external timing setup.
03:09Yeah.
03:10And you can do wonderful things with the strobe attack.
03:14So, Guido strobe attacked his bike on the dyno
03:18and saw the engine cases breathing.
03:21They were actually, the engine cases were actually-
03:24The cylinders were, where do I belong here?
03:27Oh, I'm most comfortable over here.
03:29Wobbling around.
03:30So, they were really squeezing the daylights
03:32out of what was, you know,
03:33essentially a touring motorcycle,
03:36but that was really the impetus for this.
03:38So, maybe you can talk about the,
03:40kind of the origins of why someone would,
03:43I mean, you know, why, I mean,
03:46why would you road race a flat twin BMW?
03:49Why would you stick cylinders way out the sides?
03:51Okay, they're cool, that works great,
03:53but I don't think there's a lot of problems to solve
03:56and they did solve them.
03:57Well, at the time, far from today,
04:04BMWs were thought of as motorcycles for school teachers.
04:08They were conservative, they were reliable,
04:11they weren't always in the shop,
04:13you didn't have to lubricate a chain,
04:16and they were dignified enough
04:20not to compromise your chances
04:22of making department chairman.
04:26And you used to see them around all the colleges
04:31in that period, but Butler and Smith, the importer,
04:38the importer became BMW in 1980,
04:42but this is 1971, was bought by the Adams family
04:47and Peter Adams looked over the books.
04:50What have we bought here?
04:51Oh, I see, line 28.
04:54And what he saw was a falling sales curve.
04:58And he made a wonderful decision at that point.
05:05We've got to pep up our brand, let's go racing.
05:09And so he told their parts man, Udo Giedl,
05:15whose friend Todd Schuster was an experienced
05:20and skilled fabricator, let's get a dyno,
05:25get a flow bench, let's boogie.
05:29And that's what they did.
05:32And it's not a unique thing,
05:36but this story is a story of applying the techniques
05:43of building a race bike to something
05:47that looks unsuitable for that kind of attention
05:51and getting excellent results.
05:54So what Dr. Adams did was to provide close to 200 grand,
06:00which in 1971 would buy you more than a cup of coffee.
06:05And they started learning stuff.
06:10And they built engine after engine
06:14and they went racing and they broke a lot of parts.
06:20And as I'm fond of saying,
06:23the standouts in the engine building and tuning business
06:29are head and shoulders above the rest
06:31because of the height of the pile of broken parts
06:34on which they are standing.
06:37So-
06:38My favorite line, Kevin.
06:41No one should imagine that there are tuning gurus
06:45who enter the dyno room and hold their hands out
06:50in a Christ-like manner.
06:53And immediately the needle swings to the right.
06:58You have to earn every foot pound of torque.
07:02Now you were saying earlier
07:04that observing the engine running on the dyno
07:07with a strobe attack was a frightening proposition
07:09because everything was kind of huffing and puffing.
07:14Well, Udo discovered that, okay, we want some squish area
07:22so that when the piston comes up to top dead center
07:25and the spark occurs at 30 something degrees before
07:29and the piston gets really close
07:32in the thing called a squish ring
07:34which is around the outside of the piston.
07:37If they made the clearance between the piston crown
07:40and the squish ring less than 70 thousandths,
07:46they would get contact.
07:4970,000 a lot for squish.
07:50I mean, I think the real fancy Subaru guys
07:54maybe squeeze that down to, I think you said once 28,000.
07:58Yeah.
07:59And as a moderately successful street engine builder,
08:06I would go to 40,000 and be proud that they worked fine.
08:10So 70 is a lot, there's a lot.
08:12So what's going on?
08:14And what's going on is that the crankshaft is not rigid.
08:25The cases are not rigid.
08:29The connecting rods are extensible.
08:32Yeah, well, that expression hard as steel.
08:37It's comparative.
08:39Well, it's nonsense because I've seen pressure vessels,
08:43long cylindrical pressure vessels get over pressurized
08:47and they just try to turn into a ball.
08:48They're made out of steel.
08:50It's really, yeah, it's quite malleable and bendable
08:54and aluminum has some stiffness going on,
08:56but it also will change shape quite a bit.
09:01The unique properties of metals.
09:03Anyway, as it has been with the king of the baggers class,
09:10one of the first considerations
09:13with cylinder sticking out to the side is corner clearance.
09:18So one of the things that Udo did
09:20was to shorten the rods by 10 millimeters.
09:25I think they use Carrillo steel rods
09:29at least part of the time.
09:31And they moved the wrist pin up 12 millimeters
09:36in the special vinola pistons
09:40that Udo drew to be manufactured,
09:45made from Alcoa forgings.
09:48And then he alluded, he said,
09:55there are the cylinders sticking out
09:57at 180 degrees to each other.
09:59He said, does it have to be 180 degrees?
10:02Perfect.
10:03You change it just a little bit,
10:05implying that by angle milling the cylinder bases,
10:10you might get another-
10:11175 maybe, you know, 175, very wide angle V-twin.
10:15Gets you another half inch.
10:18And there are many photographs available
10:20of the Butler and Smith bikes in corners.
10:23And you can see that they're using every bit of clearance
10:28that Udo was able to create for them in those ways.
10:31Well, the HP2, the sport bike, HP2 sport
10:34that the BMW did some years ago,
10:38it had sliders on the cylinders.
10:40And at the, what is it, Race Resort Ascari in Spain
10:43for the press launch, there was a left turn
10:47at the end of the straight, as I recall.
10:48And you, as I was getting up to pace,
10:51I put it on the cylinder and it just kind of went straight
10:54until it slowed down and it went around the corner.
10:56So all credit to them for making a spectacular chassis
11:00on that bike.
11:02But yeah, so there they are, the cylinders in the way.
11:05So the engine, of course,
11:09received the normal hot rod treatment,
11:11some attention to the ports,
11:14making special Delorto carburetors.
11:17There was a set of smooth bores.
11:22But this project was distinguished
11:26by Udo's really close attention
11:30to what a lot of hot rod builders don't cotton to,
11:35which is if the piston rings are not able to seal,
11:39you're not able to make power.
11:42And what he noticed during all this dyno testing
11:45was that the strong engines blackened their oil more slowly
11:51and the weaker engines blackened their oil faster.
11:55And he thought about that.
11:58Well, I think Blow-By.
12:01I had discovered this with my Velocette.
12:04Yes.
12:05I went through, I don't know how many pistons
12:08I've been through, but pistons and cylinders.
12:10And I was doing iron bores and I was, you know,
12:13cross hatch and blah, blah, blah.
12:15And I was using a reasonably fancy piston,
12:18not super fancy, but a nice piston.
12:20And I would run that and the oil would get black
12:23and I wasn't making that much power.
12:25And I finally just said,
12:26you forget this reverse restoration BS.
12:29And I took it all down and I had a great guy,
12:33Dave Smith in Illinois do the crank and a Corilla rod
12:38and a custom piston and a Nicosil plated bore.
12:41And some aircraft mechanic who listens to the podcast,
12:45you know, said, oh, Nicosil on air cooled cylinders.
12:48No, don't, you know, whatever.
12:50It's worked so much better than anything else.
12:52And he used a bore plate.
12:53And so the bore was round.
12:55It had total seal rings on a custom piston.
12:59And the oil looks like honey after even 2000 miles.
13:03Lovely.
13:04And wasn't it rewarding to see?
13:06Well, and it just, gosh,
13:07it just has the snap and it runs and it's so consistent.
13:10And yeah, it is.
13:12It's made me a combustion chamber snob.
13:15You know, you really,
13:16you want to keep it all inside of there.
13:18And.
13:19Well, Udo also realized that,
13:24well, eventually it got 82 horsepower from this thing.
13:28And that's basically double the claimed stock power.
13:33And each time the great aircraft radial engines
13:37were powered up,
13:39the cylinder and head were redesigned
13:41with increased fin area.
13:44So, but that wasn't possible to do in this case.
13:47So Udo thought to himself,
13:51the front of the cylinders being cooled well
13:53by the direct airstream,
13:56but the back of the cylinders are in the wind shadow
14:00and they're going to get hot.
14:03That means the cylinders aren't round
14:06and the combustion is at the top of the cylinder.
14:09So that's going to be expanding more than the base.
14:14So I'm trying to seal cylinders that are bulged and tapered.
14:19How can I do it?
14:22Well, in World War I,
14:24those rotary aircraft engines,
14:28they had radial cylinders,
14:30but the whole crankcase with the cylinder assembly
14:33whirled around.
14:34So the leading sides of the cylinders were cool
14:37and the trailing sides were very hot.
14:40And the French came up with a thing
14:42that was like the leather washer in a bicycle pump.
14:47The pressure gets behind the flanged up part of the washer
14:51and pushes it out against the cylinder wall.
14:55And the leather is flexible enough to allow that,
14:57but they made it out of brass
14:59and they called it an obturator.
15:03And the obturator was good for 10 to 25 hours.
15:09And Udo's equivalent was an L-section stainless top ring.
15:16And having so much material removed from it,
15:21it became able to flex a bit
15:24and did a much better job of conforming to a cylinder
15:27that was bulged and tapered.
15:30So it was cupped toward combustion pressure, essentially,
15:34and it's thin around the edge
15:37so that the combustion pressure can hold it
15:40against the mildly changing contours of the cylinder,
15:44of the not cylinder.
15:46When you look at the cylinder,
15:47if you could look at the cylinder while it's operating,
15:49it would look just fine.
15:51But if you poked a dial gauge in there,
15:55you would definitely see it.
15:57So it's a good thing we have instruments
16:01because instinct is not always a good guide.
16:05It's almost never a good guide.
16:10Then he thought about the second ring.
16:13Well, the G50s have only two rings,
16:16gas ring and an oil scraper ring.
16:19Why don't we try that?
16:20Because who needs extra drag from a whole row of rings?
16:25And he found that when he deleted the second ring,
16:29he needed a lot more clearance
16:32to prevent the engine from seizing.
16:35Well, now, there's a data point.
16:38Heat path.
16:39So, yes, sir.
16:41So they put the second ring back in,
16:43a rectangular steel ring,
16:47and they were able to run smaller clearance.
16:52Another thing is that the pistons
16:54were not the present ashtray type,
16:57which are that way in order to make them
17:00as light as possible.
17:03Instead, they were rather full skirted.
17:06And he wanted to run very close clearance,
17:11ended up running one and a half thousandths.
17:14Amazing, on an air-cooled engine.
17:17I mean, you know, again,
17:19reference for the street stuff that I build,
17:22that's vintage British, usually.
17:24You're at least three and a half thou,
17:25if you're very careful,
17:27and you're more than that, four and a half.
17:29If you're building an engine for a customer,
17:31as my friend at Thoroughbred Classics,
17:33John, you say, he's like, oh, four and a half.
17:36Yep, because I can't count on the guy to be kind.
17:40Yes.
17:41So he decided that there was more to heat transfer
17:47than just that all-important second ring,
17:54that he should have a long skirt
17:56and good contact with the cylinder wall.
17:59Because ideally, a piston cools itself
18:03in the absence of cooling oil jets
18:06by expanding enough to better contact the cylinder wall,
18:11whereupon it loses heat to the cylinder wall
18:15and doesn't expand anymore.
18:17But as your data, as this data points out,
18:20the rings are a primary heat path, are they not?
18:24Primary heat path, yes.
18:26Through the rings, surprising.
18:29Some years ago, some hotshot young engineers
18:33were eager to try out modern piston ring concepts
18:36on giant marine diesels, which typically have seven rings.
18:42And they were going to show lower friction
18:46and greater fuel economy and so forth.
18:48Above and below the pin, by the way, typically.
18:51Above and below, yes.
18:53So what they got was really hot pistons.
18:56And so they learned something that day.
18:58Those are not sealing rings, just the top one.
19:02The rest of them are there to get the heat out of the piston.
19:06So Udo wanted,
19:11the piston to be running at a close clearance
19:14so that the piston didn't tilt.
19:18Because try spinning an engine
19:22with offset wrist pins backwards, such a clatter.
19:26One night I took an engine all to pieces
19:28because what is this noise?
19:31I learned something that evening and I didn't have dinner.
19:35But what he did was he made the piston skirts springier
19:41by making them thinner.
19:43He took 50 or 60 grams out of each piston manually
19:49and until he had the thicknesses that he wanted.
19:53And he then found that such pistons
19:55would do several nationals.
19:58He would replace them when the clearance
20:00became two and a half thousands.
20:04That sounds like a pretty successful deal to me.
20:07That's having it under control.
20:09And this is the aim of all this nitpicky work
20:13is so that you don't have to say,
20:16yeah, we're going great.
20:17We're third and it's tied up.
20:20You know, engines do that.
20:22No, not if they're correctly built.
20:28Even so Udo said,
20:32you have to understand that these were 50 mile engines.
20:36And the reason for that is
20:38that when you take a production engine
20:41that's intended for a nice one day ride to Romania
20:48at speeds that don't get the secret police in your wake,
20:55you aren't putting a lot of stress on anything.
20:59But if you're revving to 8,200
21:03and you insist as Udo did,
21:06that it be safe to 10,000.
21:10This is push rods and rockers safe to 10,000.
21:16He insisted that the degree figures that he got
21:22when he degreed the cams agreed with the timing card
21:26that came with the cam.
21:28And he ended up with crane
21:32because he said the numbers always matched
21:36what he found with the dial gauge and degree wheel.
21:40But, oh, and another thing about those push rods.
21:43If you think about a classic British twin,
21:48there's the crankshaft and the cams
21:51are above the center of the crankshaft.
21:54So the push rods aren't all that long,
21:57but on the BMW, the Slash 5,
22:00Wander Marvins put the camshaft underneath the crankshaft.
22:04And so the push rods had to extend all the way
22:09to the center line of the engine.
22:12Oh, boy.
22:13And the vertical center line through a vertical plane
22:17through the crankshaft axis.
22:19So that made them extra heavy,
22:22a hundred pounds on the seat, 280 open.
22:2614 millimeters lift.
22:29And-
22:30More cams.
22:33So you can bet that he didn't want to bore the audience
22:37with an entire litany of how he got the thing
22:41to be safe mechanically to 10,000.
22:45But you certainly have to believe him.
22:47Okay, now back to the 50 mile engines.
22:50Why would you build an engine
22:52that lasted longer than the race?
22:56If you were swinging the three bats of starting
23:00with a production engine that's of half the horsepower.
23:03So you're dumping all this extra heat.
23:05You're applying much greater stress to all the parts.
23:09Some of them will fail.
23:11So all you want is they don't fail while we're racing.
23:16Yes.
23:17While we're drinking the champagne,
23:18it can just fall into pieces.
23:20That's fine.
23:21I was thinking about the back cutting
23:25and lifting the cylinders up,
23:27getting that slight V so that the heads will be up.
23:30And I was thinking about that
23:32from the street engine builders perspective,
23:36such as only cutting the crankshaft as much as you need,
23:41not cutting it.
23:43Say you can get away with 10,000 undercut
23:47on the crank journals.
23:50Great.
23:51That's what you do
23:52because you want to have some in the bank for next time.
23:54But if you're building a race motor,
23:55what you actually want to do is cut it 40 under
23:57and make a big radii.
23:59So you want a big radius in the edges
24:01so that it resists cracking.
24:03And I was thinking about, well, what would Udo do?
24:07You know, if I were doing that,
24:08would I cut the deck of the block
24:13or would I cut the cylinders?
24:14Because I'm like, well, I wouldn't cut the block
24:17because that lasts forever, but it doesn't.
24:21It's a 50 mile engine, cut whatever you want.
24:24But he did cut the cylinders.
24:26So another element in engine longevity
24:31is a lubrication system.
24:34And BMWs before the Slash 5 had a two gear oil pump.
24:39I think it was down in the sump
24:41and driven by a quill in automotive style.
24:45And Udo discovered that when the engine got to 9,500 RPM,
24:51there was oil starvation.
24:52And the manifestation was the big end bearings
24:59doing the tighten up.
25:02That was a song by Archie Bell and the Drills,
25:05doing the tighten up.
25:07So he studied this.
25:10At one point, he placed a transparent line
25:14between the oil sump and the oil pump.
25:20The Eaton trochoid oil pump.
25:24And he noticed that at the crucial speed,
25:29it developed cavitation on the inlet side.
25:32What's cavitation?
25:34Cavitation is pulling apart of a fluid by a low pressure.
25:41And for example, if you've filled a syringe
25:47with which you plan to measure
25:48the combustion chamber volume of an engine,
25:51and you're playing with it with your finger over the end,
25:54you could pull the plunger back and it goes back
25:58and the oil is solid again.
26:00But you have cavitated it by pulling the plunger back.
26:04Reduce the pressure enough that the fluid pulls apart.
26:08Well, feeding fluid is what the bearings need.
26:14They need a steady flow of fluid.
26:17Both for lubrication and for cooling.
26:21But when it starts to get bubbles coming through,
26:27then you're in trouble
26:28because they don't carry a lot of load.
26:34So there were bearing failures.
26:36So then he decided, I'm going to measure the horsepower
26:40that this pump is requiring.
26:43Well, it's a known fact that a single oil pump ratio
26:50to the crankshaft is a terrible compromise.
26:54It's just enough to supply the bearings at idle
26:58and the relief valve is open and lots of energy
27:02is going into forcing oil through that relief valve
27:06because the system won't accept it.
27:09It's the old V squared rule.
27:12It's awfully hard to push fluid where it doesn't want to go.
27:16And if you double the speed,
27:18it resists four times as much at least.
27:23So he got himself a smaller Eaton trochoid pump
27:30after finding that the great big pump
27:32was consuming five horsepower at racing speed.
27:37This reminds me of RC45
27:39where they turned off the oil pump at higher RPM.
27:45Formula One have two speed oil pumps.
27:48There are variable stroke oil pumps now in production cars.
27:53A lot of work has been done on this
27:56because it is so notorious
27:58that the pump is barely adequate at idle.
28:00And it's just, when at speed it's trying too hard
28:06and consuming power that you'd rather send
28:10to the drive wheel.
28:13So smaller pump, cavitation problem goes away.
28:21The thing idles at 2000 RPM.
28:23So who needs idle oil pressure anyway?
28:27Success, excellent.
28:31And of course he also noticed that hollow crank pins.
28:40Why don't I plug those up
28:42and we'll make sure that plenty of oil
28:44gets to the crank pins where it will accumulate
28:47and act as a reserve if there ever should be
28:51a suction side cavitation episode for any reason.
28:58So back to the piston for a minute.
29:01What he wanted was to make the skirts springy
29:04so that as they expanded
29:09that the contact area would increase.
29:12That is, it would gradually spread out
29:14against the cylinder wall.
29:16Not at such a pressure that would break the oil film
29:20but would have the effect
29:22of increasing the piston's cooling ability.
29:25Split skirts in old time engines were not uncommon
29:29to get that effect going.
29:32Or the steel struts.
29:34Because if you put an aluminum piston in an iron block
29:40that's an invitation to an early marriage.
29:46So.
29:47The expansion rates are different.
29:48That's what he's talking about here.
29:50Is that the aluminum will expand more faster than iron.
29:55Yes, that's why the two-stroke people
29:57went through that ritual of very slow warmup
30:01when they got their first liquid-cooled bikes
30:04because you don't get on a liquid-cooled two-stroke
30:07and go blazing out into first practice.
30:11Talking to a Victory engineer
30:13when they did the second generation Victory V-Twin.
30:18He said, I was, you know, messing with engines,
30:22air-cooled engines.
30:23I said, well, what's your piston clearance?
30:25And he said, I think he said 25 microns.
30:27At the time I'd been kind of buried in all of that.
30:30And 25 microns, I looked up in the sky and I said,
30:33that's a thou and a half.
30:35Yeah.
30:36And he was excited that I could look in the sky
30:39and convert microns to thousands
30:42because I was working in thousands.
30:44And then I was shocked and I was like,
30:45well, how do you get that?
30:46How do you get a thou and a half
30:47on this gigantic long-stroke air-cooled, oil-cooled engine?
30:52And he said, we use the same material
30:55for the cylinders and the pistons.
30:56Yes.
30:57And I said, oh, well, that's good problem solving.
31:00Excellent.
31:01Yes.
31:02Yep.
31:03One time the instincts are right.
31:07So then they also needed to do things to the chassis.
31:11If you look at a Slash 5,
31:16you're struck by the short wheelbase, 54 and a half inches.
31:19That's because its designer,
31:22this fellow, Vonder Marwitz,
31:24who was hired to sort of freshen up the model range.
31:30His idea was, I'm going to combine the handling
31:35of a Manx Norton with the comfort of a Touring bike.
31:39So the front fork had eight inches of travel
31:45and the rear a fair amount.
31:48And soft springs, comfortable.
31:54But when you look at the tubes joining the steering head,
31:57it's sort of like, well, this looks like one guy's
32:02holding the top of the steering head
32:03and another guy's holding the bottom.
32:05And now we're going to try to react braking force
32:09or twisting force.
32:12Let's join those tubes together.
32:14Well, when they did that, of course,
32:18the rider said, vibrates quite a bit.
32:21I don't remember my BMWs vibrating like this.
32:26Oh, fuck.
32:27All right, give me that drawing.
32:30So Udo had to sheet in the steering head
32:36in order to obtain some stiffness.
32:38And famously, he ran those Gheatl struts,
32:44one on either side from as close to the swing arm pivot
32:48as was feasible, straight to the steering head.
32:52So that the swing arm wasn't going to do any sashaying
32:58from side to side, because when it does, it self-steers.
33:04And a motorcycle that competes with the rider's steering
33:08is not confidence inspiring.
33:10No.
33:12Well, that idea was ultimately expressed by Kobas.
33:16No, you know, getting great big struts,
33:20getting rid of all the other garbage and just putting,
33:22you know, Kobas is the, you know,
33:24the twin spar aluminum frame person, basically.
33:28And he attached the steering head and the swing arm pivot.
33:31There's a ton of Bermudas that look like that, you know,
33:33where you can just see the spar goes down
33:36and it has a hole in it for the swing arm pivot.
33:41So you want that relationship, you know,
33:43you want to basically a 90 degree between your,
33:47yeah, when you want it to be.
33:48Because otherwise, as you say, it's a terrible feeling
33:53when it's not.
33:53Howard Davies in 1924, I guess,
33:57saw that the lower stays to the rear axle
34:01stopped at the seat post, which meant.
34:06So he continued them forward as two tubes
34:12and joined them to the down tube up front.
34:15When some designs he had, he had two down tubes,
34:18but that's what he was trying to do.
34:20He was saying, I'm going to put an end
34:22to this hind end waggling.
34:26And he did.
34:28So one doesn't often hear of Howard R Davies,
34:34but his initials HRD shall live forever
34:39on the tanks of many a Vincent motorcycle.
34:42Yes.
34:44Well, you know, here's another antique reference
34:48related to Velocettes,
34:49because that's what I've played with so much,
34:51but I had a rigid Velocette, a 37 KSS.
34:53So it's a 350 CC bevel driven overhead cam,
34:58girder fork, and as I said, rigid,
35:00and it was a delightful bike to ride on a smooth road.
35:03It steered beautifully,
35:05and it was very confident in starring.
35:07And I have a 54 Velocette MSS,
35:09which is a first year swinging arm, 500.
35:13And it actually handles not bad, especially for the era.
35:18It was quite good, but man, the difference between
35:21the confidence and sweetness of a rigid rear end
35:25and having a very strong connection
35:26between the axle and the steering head.
35:28And on a Velocette, you know, it's basically,
35:30it's like two, the swing arm pivot is like two posts,
35:35and then the swing arm arms clamp on with bolts.
35:39Yeah.
35:39I mean, it's, you know,
35:41when you're riding that bike hard on a winding road,
35:44which I've done many, many times,
35:46you're riding that bike hard, you use the rear brake,
35:50yes, to slow the bike down, but also to keep it packing up,
35:53keep it from packing up on the fork
35:55and having the fork bend too much
35:56and having the chassis kind of squeeze up
35:59on everything else.
36:00It like, it makes it steer better
36:02to keep both brakes working
36:04and to kind of keep the back end
36:06from smashing up on the front end, so.
36:08Well, the old timers used to say,
36:11you might try the back brake first, it steadies you up.
36:14It does.
36:16Talking about the BMW and all of these changes,
36:21thinking about how thorough you have to be
36:25and how many changes, we haven't talked about ignition.
36:29Like how, what do you do for ignition on a bike
36:32that does not spin to 10,000,
36:34that you're suddenly spinning to 10,000.
36:38Oil pump, we've talked about, what about oil capacity?
36:41Chassis, fork, shocks.
36:45It's a shaft drive.
36:47We're not just changing the saw blade on the back.
36:51We're changing ring gears and pinions.
36:53Yes, all those terrible things.
36:56Well, first thing, the ignition,
37:00he saw that there was some,
37:06so there were negative indications
37:08as to the stability of the valve seat inserts in the head
37:12when he ran single ignition.
37:15And when he added a second spark plug
37:18on the other side of the valves,
37:21those forces somehow evened out
37:25and the valve seat problem disappeared.
37:31So twin ignition from a CDI driven by a battery.
37:40Oscar Liebman, father of Kurt Liebman,
37:45who raced BMWs forever and a day
37:49in the AAMRR, also known as the Redundant Vowel
37:54and Consonant Society.
37:57Oscar put a Kroeber on his homemade Rennsport.
38:06Super machinist at AML Precision made this engine.
38:11So I'm sure there were a lot of Kroebers lying around
38:14as a sort of, well, you might try this
38:17or you could, good to have stuff in the shop.
38:21It is.
38:23So that was the ignition deal.
38:26And with the two ignition plugs,
38:31two degrees less timing were required.
38:34Performance was good.
38:37And what were the other items on your list?
38:41Oh, well, where do you stop?
38:42Where do you start?
38:43I mean, you were talking about connecting
38:45the Giedel struts, you know, connecting the steering head
38:48to the swing arm pivot.
38:50And then what do you use for suspension?
38:52All the chassis, initially they were given
38:56for in quotes racing chassis by BMW.
39:00And I think they built bikes around a couple of them
39:02and didn't necessarily like them all that much.
39:06And at one point they, Rob North built them a frame
39:10in his own style.
39:12And he moved the engine forward 15 millimeters
39:17and raised it in the chassis.
39:20So that was one of the iterations.
39:25And I think on the 1000cc thing,
39:31they ended up with a WM4 rim on the front
39:35and a WM5 on the rear.
39:38But all of that was in flux during this period.
39:41If you look at the Superbike book
39:45that John Owens roped me in on,
39:50and you'll see that little skinnier tires at the beginning,
39:54like 1977, as the years went by, the tires got fatter
40:01and thus it shall ever be.
40:05They put Ceriani forks on some of the race bikes
40:11that they built in the earlier seventies.
40:15They limited the, I think Todd Schuster built
40:20stroke limiting hardware for the slash five fork.
40:27And because all this time, the worst problem
40:30was corner entry, trail braking to the apex.
40:35You could dig in the cylinder head
40:36and that would be the end of your day.
40:39So if they limited the travel,
40:44if they stiffened up the front end,
40:46they lost in other areas.
40:48Mechanical grip would go down.
40:51So they built a mechanical anti-dive system.
40:55The brake calipers were pivoted
40:59on the front axle center line on little bearings
41:03and struts from them went up
41:06to the underside of the steering head
41:08so that any desired percentage of brake torque
41:14could be used to prevent the front end
41:17from diving quite as much.
41:21And Udo said, and I remember this quite clearly,
41:25said on smooth pavement, it was very good,
41:28but if there were bumps, it might not be that good.
41:34Because of course what happens
41:35is it starts to hop and stutter
41:38and you're just in a bad territory when that happens.
41:46So, and you'll notice that there are no mechanical
41:49anti-dive systems in use today.
41:52People have found that some aspects
41:57of the motorcycle compromise aren't amenable
42:01to just being fixed.
42:05You have to, you can get them close.
42:08And, but like Rob Muzzy said in that 1983 interview
42:14about his 82 bike, he said,
42:17I don't work on any one area more than 80%
42:23of what I think is possible as an improvement
42:26because at that point, there are other things
42:29that need my attention a lot more.
42:32So it's not a place for perfectionists.
42:35It's a place for empiricists.
42:40I'm sorry that our snowmobile powered motorcycle builder
42:49friend doesn't like empirical work.
42:53He would like to calculate everything.
42:56But the great thing about the Udo Giedl, Todd Schuster,
43:01Butler and Smith BMWs was that they were an evolving,
43:09attentive set of solutions that was being subject
43:14to constant update.
43:16And that's really what engineering is.
43:18Engineering doesn't just say, okay, here it is.
43:22Here are the drawings.
43:24Pardon me.
43:25Here are the drawings on my little thumb drive.
43:31And then the results are wonderful because they aren't.
43:35The results are never wonderful.
43:37If you could, even with all the modeling that happens now,
43:40it's just, it's a litany of broken parts.
43:43It's just, the original, the original was no plan
43:49survives contact with the enemy.
43:52And in this case, the enemy is the reality
43:55of physical operation in the real world.
44:00So, and of course we'll get to that in a future episode
44:06when we discuss alternative front ends.
44:08Yeah, well, alternative front ends,
44:12all of this conversation reminds me of one of,
44:15another one of Kevin Cameron's great lines.
44:18100% doesn't make the grid.
44:22You gotta, you gotta get there.
44:23I like, I like Muzzy's 80%.
44:25It's very true.
44:26You know, when you're working on a project,
44:29say you're doing a restoration,
44:30the first 80, 90% takes up, you know, 40% of the time.
44:37Yeah.
44:38And then that, if you really want to do that last,
44:40you want it to be perfect as,
44:43man, that last 10% takes forever.
44:47Yep.
44:48It's really true.
44:49Because the thing you don't like to see is paint flaking
44:53and extruding out from under a washer
44:56as you tighten the nut.
44:59Where was my razor blade?
45:01What was I thinking?
45:02Well, where do you find washers
45:04that actually fit beautifully?
45:07That's the thing.
45:08Why did-
45:09That's a troublesome.
45:10It is.
45:11Eight millimeters and five sixteenths are close.
45:13Yeah.
45:14But six millimeters isn't close to anything.
45:18But man, any more, you know,
45:20yeah, you're trying to wander into a,
45:23there are some good hardware stores around,
45:26but they're few and far between.
45:27It's such a, it's just a different time.
45:29And when you go to the auto parts store,
45:31they have a reasonable selection.
45:33Like you can go to your big chain auto parts store
45:35and they have, you know,
45:36but they're all in little plastic packs.
45:37And if you want a flange bolt,
45:40a five sixteenths, 18 flange bolt, four inches, let's say,
45:44or let's call four and a quarter.
45:46You need four and a quarter.
45:47You're not going to find four and a quarter.
45:49It's going to be four and a half, or it's going to be four,
45:51or you're just not going to have a flange bolt at all.
45:53And then you have to buy the washer,
45:54which they don't sell.
45:57They don't sell.
45:59They sell five sixteenths and eight millimeter washers
46:01in one pack, you see,
46:02because they just make one washer.
46:04And then the flange of the washer sticks out really far
46:07behind, outside the head of the bolt.
46:10And it's just, it's not aesthetically, it's too much.
46:15Some BMW owners may be offended by this litany of truth
46:23rising to the top of a bubbling cauldron of failure.
46:29What I have to say is that the product testing
46:33is aimed at the intended user.
46:37And if the intended user is happy at 8,200 RPM
46:43with a life of 50 miles, you're going to test differently
46:47from the way product testing is done at BMW,
46:52particularly in the 1970s,
46:54because they made a gentlemanly motorcycle
46:59that was highly reliable under the intended use.
47:05And that's how anything is.
47:09When they brought that V10 automobile to put down,
47:15what was it?
47:16A Yamaha R1?
47:17The R1 was driven away and the V10 had to be loaded
47:22onto a trailer because its brakes were no longer present
47:27after a back-to-back at Willow Springs.
47:30Oh, that was the car versus bike, the Viper.
47:32We had a Dodge Viper back in the day.
47:35Yeah, that reminds me of a great conversation
47:39I had with a fellow at Ariel,
47:40the current Ariel company who does the Ariel Atom.
47:43The Ariel Atom is a tube frame.
47:46It's got rocker arm suspension.
47:48It looks like a big insect.
47:50I think they had Honda power, like VTEC, high horsepower,
47:55I mean, in the hundreds.
47:57And he was so proud because they did a motorcycle recently
48:02as well, but I was talking to him about the car
48:05and he was so proud because he would take his car,
48:09which was essentially a two-frame motorcycle
48:12with a high revving, reliable Japanese engine.
48:14And all these supercars would go home on a trailer
48:17and he'd just keep doing quarter mile times
48:19and laps all day because it just ran and ran.
48:23And that's almost, I think the weak point
48:26on almost any modern high-performance car
48:30outside of Porsches typically is the braking systems.
48:33They are two-lap wonders.
48:35You know what I mean?
48:36It's a 4,000 pound or 3,000 pound thing at best
48:40and the brakes just go away.
48:41So, yeah.
48:44So they used Harry Hunt coated aluminum brake discs
48:49on tracks that didn't require the maximum
48:53and Mionite iron rotors on other tracks.
48:57And I have seen personally what happens
48:59if you really lay into coated aluminum brake rotors.
49:06It's called the Oreo cookie effect.
49:08And what happens is that the high stiffness of the coating
49:16and the low melting point of the filling,
49:19that tasty white stuff, the aluminum in this case,
49:24softens and begins to squeeze out at the edges.
49:27And soon it has squeezed out enough to begin
49:30to transfer itself to the throat of the brake caliper,
49:34which now begins to look like, what did this thing do?
49:38Re-enter the atmosphere at 32,000 feet per second?
49:43Really is terrible looking.
49:46So those lightweight rotors are attractive
49:49because of their lightweight,
49:51but they have limited application.
49:55Put them on your show bike.
49:58Iron or stainless steel for the rest of the world.
50:08But I think the two things that struck me most
50:10about the Butler and Smith, Udo Giedl, Todd Schuster epic
50:17was first of all, that a business person went racing,
50:22looked at a sales curve, said, this won't do it all,
50:27looked around at what was happening in motorcycles.
50:30Oh, all these brands are racing these super bike things.
50:36Let's do it.
50:38I think that was a leap.
50:41And the other thing that strikes me here
50:44is the depth of these men's work
50:50and the detailed understanding
50:55that they were able to get from looking at the symptoms.
51:01For example, the obvious one being that the strong engines
51:05blackened their oil more slowly
51:07and the weak engines that were combustion gas
51:13streaming down the piston and boiling the oil
51:16and baking and cooking it black,
51:20blackened their oil more quickly.
51:22Udo didn't derive from that as solution.
51:27Udo did.
51:28This is an admirable program,
51:30especially since their competition was the new breed
51:36of thousand CC four-cylinder Japanese import bikes
51:40that made gobs more power.
51:44And yet, because their chassis were
51:48basically 1960s technology,
51:52they couldn't use the power in a straight line
51:55because of the weave threshold being
51:57where the bike could get its chin over.
52:00Oh, this is going to shake up your breakfast.
52:05And only gradually as the import bikes,
52:12the Japanese bike teams began to do the things
52:16that Udo had pioneered.
52:19They began to get similar results
52:21so that although a BMW won the Superbike Championship in 77,
52:27a BMW only finished third in the championship a year later
52:32because things were happening fast.
52:37So this is a valuable chapter
52:40in the development of Superbike.
52:42And it is also an observation
52:45that the tools of racing are effective
52:51even when applied to vehicles
52:53that appear at first glance to be unsuitable
52:59as we see today in the King of the Baggers class.
53:03Yeah.
53:04We'll see it again in some other class
53:06that we haven't dreamed of yet.
53:08No, it's spectacular.
53:10Racing, whatever, just get it, build it, break it,
53:14improve it, et cetera.
53:16It's beautiful.
53:16And the Ghetto thing, I don't know.
53:20It's just, it's a remarkable application, as you say,
53:23of intelligence and observation and we'll call it fortitude,
53:28just keeping after it.
53:30And these qualities are available to all of us
53:35if we have the time to invest.
53:38We have, we let our curiosity be our guide
53:42and we stay at it and learn as we go.
53:47It's, that's why I like to say
53:50we're all students in this game
53:53because the motorcycle has so many degrees of freedom.
53:57It can always elude our understanding in one of them.
54:02Yep.
54:04Well, thanks for listening, folks.
54:06Do join me at Barber in October.
54:09I have never been to the museum.
54:11I'm dying to see the museum
54:13because it has all the car stuff
54:16and all the motorcycle stuff.
54:18I'm struggling to think of a place in this world
54:23that could even come close to what I've seen
54:27of Barber published and the stories I've heard.
54:30So I'm excited.
54:30It is outstanding.
54:31No question.
54:32Yes, well, I'm excited to get down there.
54:34They have a bunch of BMW race bikes from the era,
54:39750s included.
54:41So we're hoping to see those outside the museum walls
54:46in October and hear them.
54:48So thanks for listening.
54:51We put it out every Wednesday, jump in those comments.
54:53We have more episodes to come that will be based
54:56on people asking for topics in the comments.
55:01And we really appreciate those.
55:03So join us again.
55:06Thanks.