2018 Brno MotoGP Friday Round Up: Heat, Tires, Strategy, The Root Of Yamaha's Problems, And Yet More Aero

It is hot at Brno. It was hot at Assen, it was hot at the Sachsenring, and it is positively scorching at Brno. Air temperatures are at a relatively bearable 34°C, but the asphalt tentatively broke the 50°C during FP2. That is officially what is known colloquially as a scorcher, testing riders, teams, and above all, tires on the first day of practice at Brno. Where last year, the riders concentrated on the soft and the medium Michelins, on Friday, the MotoGP riders spent their time assessing the medium and the hard. The downside of forcing Michelin to choose tires for the entire season back in February is that sometimes, their crystal ball fails them, and the weather deviates wildly from what might reasonably be expected. The heatwave which has Europe in a vice-like grip is just such a case.

There are upsides to the heat, though they are perhaps unexpected. There were just four fallers at Brno on Friday across all three classes, less than half the number from last year, a third of the number in 2016, and a massive five and a half times fewer than the 22 crashers in 2015. It's hot and dry, so the tires will definitely grip.

Sometimes a little too much, as Jorge Martin found to his dismay in Moto3 FP1. The Spaniard managed to highside his Del Conca Gresini Honda Moto3 bike and break the radius bone in his left wrist, ruling him out of action for Sunday's race, and making him doubtful for next week's Austrian round at the Red Bull Ring. Martin had steadily built up a lead over Marco Bezzecchi in the Moto3 championship in the last two races, only to throw it away with a huge mistake at Brno. There may only have been four crashes on Friday, but one of them was very costly indeed.

In the MotoGP class, the timesheets tell a rather deceptive tale. Dani Pedrosa finished the day faster, and digging into the timesheets, he looks quick on old tires and in race trim. Danilo Petrucci was second quickest overall, and also showed solid pace. But the Pramac Ducati rider was convinced that the riders with real race pace were behind him, Andrea Dovizioso in fifth, and Marc Márquez in tenth. Not where you might necessarily expect to find the fastest riders on the day.

The luxury of strategy

"For sure they are hidden, but I think that's a working method, a little bit different," Petrucci explained. "Because I think they are a little bit faster than everyone, and they can take this risk to work more on the bike when the tire is used, because tomorrow morning, they know that with one lap they are in front. So fortunately for them, they can work on the bike for one or two runs more than our situation. Because tomorrow is a qualifying, more or less. Today you spend the last run on the new tire, so they can see, they can collect data, they can ride the bike with used tires, so they will have more experience."

Marc Márquez acknowledged that this was exactly what he was doing, though it went against his natural instinct. "Of course I’d like to go to sleep tonight with the fastest lap time or try to be on the top, but I have understood this," the Repsol Honda rider told us. "Especially last year, as it was the strategy for Dovizioso last year. Prepare for the race, and tomorrow we will try to be in the top 10."

That strategy does not come without risk. "You have one chance," Márquez said. "For this reason sometimes it is more risky like it happened to me in Mugello that I went into Q1, or Montmelo. But it is the way to understand how to work otherwise it is impossible to understand what you need."

Chicken and egg

Andrea Dovizioso agreed with Márquez, as you might expect given that Márquez had taken the strategy from Dovizioso. "The problem is that you are only able to do that when you are fast," the factory Ducati rider explained. "Because if you are not fast enough and you are out of the top ten, you never know if you are ready for the next practice. So everybody puts the soft tire at the end of practice, because everybody wants to be in the top ten. If you are able to be fast when you try the pace, you can do that. That's the reason why most of the riders don't do that."

Dovizioso was confident he had the speed, however. "It was really good, even better than what we expected," he said. "Our speed is really good, and that is the best you can have on the first day, because it gives you the chance to make more laps on the tires, and you are able to work a lot for the race. We didn't put the soft tire at the end, like Marc, and we are in the top ten, which is very important and positive. We showed really good speed, with used tires, with a new tire, so really happy. That doesn't mean this will be enough, because the consumption of the tire is the biggest point, so we are working a lot on that. It's not easy, but I'm really happy about the first day."

Where's the beef?

Why risk dropping out of the top ten on Friday, and gamble on the weather being good enough on Saturday morning to take a shot at trying to get straight through to Q2 in FP3? Because by not worrying about qualifying on Friday, you effectively buy yourself another 30 minutes of practice to work on race setup.

Most riders spend the first half an hour of FP1 and FP2 working on the race, before switching to new tires and a more powerful engine setting to try to secure passage to Q2. That means you have to focus on one bike for your race setup, while the mechanics get the second bike ready for a pre-qualifying dash in the final fifteen minutes. Time spent on qualifying is time lost to race setup, a lack which only becomes apparent on Sunday afternoon.

Danilo Petrucci explains: "Here, we have to prepare one bike for the fast lap, for the qualifying, and one bike to make all of the race. The bikes are very different comparing between the race pace tire and the qualifying tire, so you have to deal with the electronics, with the setup, you have to understand a lot of things. For sure the bike changes a lot during lap by lap. And you have to care very, very much about the pace of the race with a used tire."

A quick look at race pace shows that Márquez is indeed quick, with Dovizioso not a million miles behind. Dani Pedrosa is running low 1'57s consistently, and Andrea Iannone is pretty consistent as well, despite having missed out on Q2 by ending the day in eleventh. Marc Márquez' assessment was broadly similar, though he played down his own strength. "At the moment I think the fastest guy on the track is Dovizioso," he said, "but then it is Dani, me and two or three more riders with a very similar pace."

Tire wear

The big issue for everyone is the consumption of the rear tire, especially in the heat at Brno. Tires coming back into the pits looked very well used, beyond what you might expect in cooler temperatures. That made it imperative to focus on race pace, and not worry too much about qualifying. But that was a luxury only Andrea Dovizioso and Marc Márquez could afford, while others struggled to keep pace. "For sure it was a difficult day," Valentino Rossi said on Friday afternoon. "The conditions are at the limit with more than 50 degrees on the asphalt. It’s difficult to manage. It’s also difficult to ride the bike at the maximum because it looks like the track have quite a lot of bumps, like a little worse compared to last year. So it’s not easy. I don’t have a fantastic feeling, especially in the front. We still have to work."

That wasn't his main concern, however. "For me the main issue, the biggest problem will be the rear tire degradation. Here the rear tire drop a lot. After three or four laps you lose a lot of grip and you have a lot of spin so it’s difficult to keep the right pace. So we have to work a lot on this point, in this area. It looks like the situation is not very clear still because a lot of top riders try different tire options front and rear. I don’t try the harder option but a lot of riders like it. Tomorrow I will try. Maybe tomorrow we can understand in a better way our level."

Tire degradation was not peculiar to Yamaha, however. "I think everybody suffers," Rossi said. "It depends who suffers less. When you put the new tire you have two laps where you are fast and it’s very easy to improve the lap time. But for 21 laps I think the key for arrive on the podium is to try and suffer as less as possible. The rear degradation is a lot, so you lose a lot of performance, you lose a lot of time. The track is also long so the gap become bigger."

A hardware problem, not a software problem

Yamaha still haven't brought a solution to their tire wear problem, something both Rossi and Viñales have been pushing very hard for throughout the season. The issue, Yamaha's MotoGP project leader Kouji Tsuya told a press conference of the technical leaders of the MotoGP manufacturers, was down to a fundamental design issue of the engine. "We have to concentrate to improve the acceleration," Tsuya-san said. "Also by electronics, and also by chassis, but unfortunately we cannot change the engine configuration."

Tsuya-san did not elaborate further, but a conversation with MotoGP technical guru Neil Spalding proved enlightening. Spalding believes that the issue is down to the crankshaft, which he labeled "probably the most important component after the tires." Like Suzuki last year, Yamaha got the mass of the crankshaft wrong, though they erred in making it too light, rather than too heavy. That is making it more difficult to control acceleration (and deceleration), which is making the rear tire spin, and causing it to degrade. Yamaha will have to wait for 2019 to be able to fix that, however, as the technical regulations mean that engine design is frozen for the season at Qatar.

The way to fix this, of course, is to get the engine right in testing, something which both Suzuki and Honda have done this year. Testing is the next big focus for Yamaha, the Japanese factory finally buckling and deciding to set up a European-based test team, much to the delight of Valentino Rossi and Maverick Viñales.

"I push a lot for the [European test] team," Valentino Rossi said. "I think it's a great idea, because to work with the test team in Japan is a bit difficult because, first of all, the tracks in Japan are very different compared to Europe. So I think it will be very important for Yamaha. And also the rider is very important, because to understand something you need a rider that is fast like me and Maverick or maybe just a little bit less. I think we have some different names on the list. [Bradley] Smith is one, [Jonas] Folger is another, that already knows the bike. It's important to a have a rider that is not too old and can go quite fast."

Loopholes exploited

At Ducati, Danilo Petrucci was playing the role of test mule, debuting the latest update of their aerodynamic fairing. The fairing (shown in a tweet from the Alma Pramac Racing Team below) has two components, an upper mini-moustache-like loop similar to the parts used by Yamaha and Honda on the upper part of the fairing, and a reduced box duct on the lower side of the fairing, similar to the current fairing:

What Ducati appear to have attempted is to recreate the most successful iteration of their winged fairing, before the ban on unprotected winglets came into force. There is an upper winglet to provide anti-wheelie, and a side wing to add some stability, as pictured below in a shot from Scott Jones.

Whatever they have done, it appears to have worked. Petrucci was certainly delighted with the new fairing, setting his fastest time with the new fairing and not finding any negatives with it. "The biggest point is that the new fairing has no negative points," Petrucci said. "So I mean there is not the difference between day and night. We don't gain 10 km/h in the straight, I don't know if we gain anything, because it's like 1, 2, 3 km/h, but I'm not sure. The positive point is that the handling is better, it's not so heavy to change direction. And when you try something new and it has no negative points, it's OK, because you can compare. And especially we did a comparison, one bike with the old fairing, one bike with the new fairing, with identical bikes. And this is good, because it means the work done is better."

Petrucci's test work was welcomed in the factory Ducati team, where both Andrea Dovizioso and Jorge Lorenzo were encouraged by the results. They will likely use the fairing on Saturday, with an eye to using it in the race. If the fairing is as good as Petrucci suggests, and improves the anti-wheelie function without making the bike more difficult to turn through the corners, they will have made a major step forward. Saturday will be the proof of the pudding.

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Total votes: 98
Total votes: 45

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Thank you David, thanks Neil Spalding, now it makes much more sense to me. It's the crankshaft, Apical!

Not enough flywheel. Too much flywheel effect slows the motorcycle's acceleration, not enough flywheel effect & the rear wheel spins like a dervish full of strong coffee. Dear Doctor Hook-up, can we have some more rear grip please?

Will the new aero give Dovi his mojo back? I hope so. I guess if A.D.04 was gunna use it in the race he would try it in practice.

Total votes: 29

... "I told you so" (because I didn't), but I had started to suspect Yamaha's acceleration issue extended well past the electronics, and was perhaps an engine design problem. Sure enough it appears that is the case. The deafening silence from the factory over the past several months makes a lot of sense in that context: There may be little they can do about the issue, with the possible exception of traction control bandaid, however it's doubtful that will get them where they need to be in 2018.

Total votes: 30

The more we consider the recent struggle of spinny Yamaha, the 2015 - 2016 gravel gobbling Honda, the pre-Gigi turns in like a turnip truck unless twenty-sevened Bologna turd, and Aprilia/KTM projects in general...the more appreciation and awe arrives for ant-sized Suzuki's current machine. Motor and electronics in particular, and mating to a rideable bike that he is as flickable and predictable as they come. Great job over there! Really. How much has been done with how little is bloody miraculous. (Now get a satellite squad and major sponsor eh? P.S. thanks for the GSXR 750 while middleweights vanish and liter bikes are bitter angry brutes with F1 babysitting gadgets).

Heat waves and tires earmarked in March brings a rather odd dynamic. Along of course with championship electronics deteriorating tires a bit. We have had wet weather specialists in the past (2017 had lots of wet sessions), and still have a few (hence Pescau for our Malaysian friend). Could they become greasy heat specialists?

We also have some riders that don't need a bike adhering with edge grip. Marquez of course comes to mind, skating his Honda around wildly but strangely within sufficient control. And smooth light riders that don't stress tires much, like Pedrosa. Then the sensitive right hand riders that can manage a tire a bit like the proprietary electronics used to...Zarco for instance.

Then there are the strategic. Not just riders, garages, with plans for various scenarios. A few come to mind, you get the idea. Point being, the era of jumping on a bike and wringing its neck like a wild beast are behind us. But so is tidy 250 front end rail riding Q lines by myself precision. The front pack is an amazing breed now. Very wisely methodical. Inordinately bold/brave bar bashers. Sensitive adaptors. Team oriented with set up and development. Greats don't you think? Cooool.

P.S. careful with either/or conclusions re Yamaha engine design vs electronics. Electronics management and maximization, and engine performance/character - separate exclusive entities? Not how I see it. Issue of both for Yamaha. Not disagreeing with the "YOU ARE AMAZING, THANKS!" Spalding tech articulation. It is true. But is this crankshaft character within parameters that the Yamaha proprietary electronics could manage? Perhaps.

Yet again Yamaha, the issue casts light on underfuctioning of the Japan based Superbike rider testing, lack of breadth and volume of data via two factory bikes (one of which ridden by a teething rider), lack of Magnetti Marelli specialist, and may as well add lack of lower class pipeline program. Your current PR effort doesn't change minds as much as upcoming actions.

Go Dani!

Total votes: 33

Great article, David! (and great comments, Motoshrink and others). As with the rest I am very glad some clarity has been brought forward for a technical explanation of the Iwata-United Track Polishing Squad, AKA Team Movistar Yamaha.

Rotational inertia can indeed be the Devil's own limb when it comes to track performance. Too little and you have throttle response that would shame a light switch. Too much and it feels like the throttle butterflies are rotating through molasses. In the winter. In Greenland.

But rotational mass also impacts quite a few other things besides throttle response. As pretty much everyone now has a backwards rotating crankshaft (except KTM, but I expect it may be on the grid next week...at the cryptically re-named Rückwärts Motorrad Grand Prix von Österreich) we can conclude that pretty much everyone knows and accepts this. To start with, the three largest rotational masses (Fr & R wheel assemblies and the crankshaft) all comprise individual quasi-gyroscopes, and when the bike leans they are individually subject to Precession, which in simple terms means the axis of rotation would much prefer to follow a conical orientation than one described by a straight line, but are constrained from true independence by the chassis sturcture connecting then all. The precession deviation is caused by the Euler Nutation, which is the extent and rate of the bike's lean angle (in this case roughly normal to the axis of the 3X flywheel rotations, but offset due to the lean angle being along a mass centroid axis, which is again resolved by the connecting chassis bits). Seriously, if you are ever at a party and someone starts spouting off about Euler Nutation, toss a drink in their face and walk quickly away. No one will blame you in the least.  

So here is the short version: A rückwärts rotierend crankshaft mass should be optimized to minimize any negative effect of the spinning wheel assemblies when the bike is being leaned over.

But there is a lot more going on than just this. One of the other significant effects of the backwards whirling crankshaft is to counteract excessive weight transfer under acceleration (and it also works, to a exponentially lessor degree decelerating, when the weight wants to shift the other way). However, this effect, while joined at the hip to the direction of crankshaft rotation, is not directly caused by it. The reason engines "twist" about their crankshaft axes is due to piston side thrust...period. It is the side thrust on the piston, which will always exist in a reciprocating engine due to connecting rod angularity (at least when all the connecting rods are angled the same way on the downstroke, which they will always be with a single crankshaft), which presses the piston onto on one side of the cylinder wall, that causes this rotation. I have seen far too many explanations that start and end with: "For every action there is an equal and opposite reaction" (i.e., Newton's 3rd Law of Motion). But leaving it at just that gives us an understanding equivalent to that of common a grey squirrel (OK, a sharpish grey squirrel), and if Sir Isaac saw us stop at that he would throw apples at our heads. The mere fact that an engine is spinning does not mean the engine block wants to spin countrawise. The only mechanism between a bare crankshaft and an engine block is bearing friction, be it rolling element or hydrodynamic, and that effect is always in the same direction of the crankshaft. To have a counter-rotating effect, you need a connecting rod (or a large propeller*). This rod angularity happens four times over two crankshaft revolutions, but with four very different effects, and the only one that really matters to us is the power stroke, as during that phase the forces on the piston are exponentially larger than at any portion of the other three events. But while the power stroke may be the main contributor, we also accept that it is not constant as the piston descends in the bore. You have to derive the combined effect of cylinder pressure, resistance, and rod angularity to map the forces involved. E.g., the highest cylinder pressure for any given RPM does not occur where you have the greatest side thrust geometry, and the cylinder pressure, in both magnitude and duration, varies with RPM. 

So where does the crankshaft rotational inertia come into this? Simple: There is more to push than just the mass of the race bike parallel to the track, the rotational assemblies must be pushed to a higher RPM as well, and, having mass, they are resisting via inertial forces (or will find themselves in the docket charged with violating Sir Isaac’s third law). So with a higher crankshaft rotational inertia, the greater the piston side thrust (or, more accurately, an equivalent force applied for a longer duration, which works out as near as doesn't matter), and the greater resistance to having all the weight rotate onto the back wheel. Horn Mono's are cool, but they don't win races.

So here is the short version #2: A rückwärts rotierend crankshaft mass should be optimized to minimize any negative effect of rearward weight transfer when the bike is being accelerated.

So, could we also change the rod ratios (before we seal our six engines) to optimize the engine rotation? Sure, but not much. Rod length has an effect on piston side thrust, but not as great as many prescribe. But there are other very important things that are impacted by rod ratios, such as peak tension and compression loads on the rods (and their poor underappreciated bearings), cylinder filling, and my favorite, expansion ratios near TDC (which are very much magnified on high CR engines. The effects of various rod lengths may not be all that spectacular with a meek 9:1 CR, but plug a 14:1 (or higher) CR into your expansion ratio calculations near TDC and you start to see some very noticeable Delta's). The last is critical as it has a major impact on when (during the combustion down stroke) you obtain peak efficiencies, which, as we can all now surmise, are a combination of cylinder pressure and the rod angle to the crankshaft centerline. Changing one variable (say, rod length, or having an offset wrist pin) to solve a single issue (say, anti-wheelie effect), may solve the problem in a very unpleasant way (say, since your expansion ratios are now screwed up the modified engine couldn’t pull the skin off a rice pudding. But hey, no more wheelies, mates!).

So how does Yamaha attack this?

First, please note the very lawyerly (OK, cowardly, if you insist) use of the phrase "optimized to minimize any negative effect". But this is actually neither lawyerly nor cowardly, but rather the nut of it. Not all effects are bad, what is often bad is too much of a good thing. Think of it like medicine, where two aspirin tablets can make your headache better, but 200 means a trip to the ER. So Yamaha may have a few dodgy things happening with regards to crankshaft inertia and rear tire traction, but even if they could slip a new crankshaft mass past the DORNA goalie, would Vale and Maverick like it? Maybe, but maybe they would then complain that the "fixed" bike is harder to turn. I did notice something interesting this year; Vale now seems to go with the smaller 320mm front brake rotors (vs. the 340mm)  far more frequently this season than last. Vinales didn't seem to follow Vale's new practice until very recently.  If the counter-force to wheel precession is a marginally too-light crankshaft, then re-balancing the bike with smaller front rotors would seem the logical way to go. No confirmation on this, but I will be watching to see if this is a real change or just a perception. The V-4's seem to also like the smaller front rotors, but I suspect the rotational inertia of a V-4 is "naturally" lighter than an I-4, and they can add mass as needed during development (and both the Ducks and the Hondas seem to have a more rearward weight distribution that would naturally use more rear brake and less front in any event). You can find similar cases all over the vehicle dynamics of a MotoGP bike: They are systems, not a collection of isolated components. Change things (in isolation) at your peril. (As a side note, Bonneville racers run some of the heaviest cranks/flywheels of all. They are not concerned with turning or anti-wheelie effects, and the greater mass of the rotating assembly has a significant damping effect on all of the dynamic variation generated by the valve train. I also suspect that Ducati may be the only one out there with a truly balanced valve train, thanks to the Desmodromic actuation. I also do not think the "system quietness" of the Ducati valve train is insignificant to their power production).

But getting back to Yamaha, not a lot of good options, but plenty of bad ones:

1). A unified electronic solution? Very difficult, as to damp the effects of a too-light crankshaft excessively spinning up the rear tire may require more CPU speed (or mechanical refinement) than Iwata's tuning of the Magneti-Marelli box allows. Do they try and find that speed by...um...optimizing the attached IMU (as their competitors are suspected of doing)? But how many yen do we toss down that rat-hole with a new "spec" IMU coming on board next year. (so we should save our yen to tweak the new "untweakable" IMU for 2019 (being that there is probably no such thing as "untweakable" when that IMU has to communicate with multiple other systems), or even use the computing power built into the rider's airbag suit technology for a boost. (Don't laugh, Kevin Cameron wrote another brilliant piece about this a short while back). As to the mechanical limitations, those with far more knowledge than I have about the various control systems have shared that the previous in-house Yamaha controls allowed all four inlets to function independently for traction control, but the MM package requires that the controls work on pairs of cylinders only.

2). A bifurcated electronic solution? In this case, you would have to program a "virtual flywheel" into the MM allowables. It is pretty straight forward to calculate the maximum acceleration of a slightly heavier crankshaft, and the apply those parameters as absolute limits imposed by the ECU. In other words the engine would behave like it had a higher crankshaft rotational inertia (at least from a traction/wheelie control standpoint). The second stage is to program the anti-spin/anti-wheelie controls on top of those baselines (i.e., not parallel and equal in precedence). The two would not be allowed to interact with each other in a way that would allow the command precedence to shift from the virtual flywheel to the anti-spin/anti-wheelie controller. Except that maybe you could also assign different virtual flywheel effects by RPM and Gearbox ratio (if allowed...or at least undetected) and then have the anti-spin/anti-wheelie controller left to clean up any remaining mayhem (and I believe a small dash of mayhem is always required to reach the highest performance levels. Full control is, well...slow). So why bifurcated over the unified solution? Only to work around the limits of the native MM controller. With a "clean sheet" in-house design, the unified solution would be the goal. But if the MM package does not allow for this, then the bifurcated solution would be worth exploring. It would not surprise me if some of the bikes on the grid already do (something like) this.

3). A dumb mechanical solution? Adding rotational weight to other components of the drivetrain is a non-starter. It would probably screw up the handling six-ways from Sunday, and I do not think the Yamaha slick-shift gearbox would like dealing with new mass properties downstream. At all.

4). A quasi-mechanical solution? This would entail having lower RPM restrictions placed on the cooling or lubrication system flows to mimic a higher flywheel mass. The restrictions would have to be placed outside of the "sealed" assembly to be legal. You would probably wreck a lot of otherwise useful engines trying this, and the internal impellors and passages might not like it. In fact, if the internals were up to this, I would be very upset at my engineering staff (I once witnessed a "bend to failure" test of a large commercial aircraft wing where the failure was at 117% of the targeted load. The Chief Engineer wanted to fire everyone involved on the spot for having built him "this goddamned boat anchor". +3%/- 1% is what you want, lads.). Place this in the "another shockingly bad idea" file...and then burn it.

5). Teach the pair of 'em to use the bloody thumb brake better on acceleration. Buy Stoner a pint and ask him how its done.

So what can be expected? Not a lot except very long nights and a shit-ton of hard work in Iwata. They will continue to fine tune the chassis and weight distribution, They will continue to refine the electronic controls and increase their knowledge of the MM bits. They may be playing with some form of bifurcated electronic controls as mentioned above. They will be hoping for a good bit of luck in the weather. And, well, screw it...they have already started working on next year's bike anyways. Putting a fast test-rider onboard in Europe will go a long way to making sure they don't find themselves lost in the Devil's own forest of limited options going forward. Cheers.

PS - Of course, they could look at an I-4 with counter-rotating crankshafts (of not necessarily the same mass). There are more benefits to this than commonly thought...but right now I have several shirts to launder.

PPS - I do not get invited to a lot of cool parties, but when I do I bring an extra shirt. Freshly laundered.

PPPS - Can we now officially refer to the old (banned) Ducati Aero package as "le corna di tori"? I always hoped Vale would have waved a red cape in front of one. OTOH...from an aero standpoint, the new ones look brilliant (as did the banned one).

*The effect of a large propeller, especially on vintage WWII single prop aircraft, is a sight to behold. The resistance of trying to spin a massive prop through the air wants to drive one wing towards the sky and one into the ground (which has sadly caused more than a few accidents when under-trained pilots try and fly an old warbird for sport. These machines are not to be trifled with). In this case, almost all of the vehicle rotation is from the prop, as the forces involved sneer and make fun of any puny effect from piston side thrust (even when coming from 27 liters of engine fortified with two-stage, two-speed supercharging). A clever designer would still try to have the piston side thrust opposite the prop rotation, but would also understand that it is a very thin veneer of counter-effect. (Just as an example, an F4U Corsair had a prop diameter of 13'6", or 411.5 cm for those of you who have stopped using the length of a dead king's thumb for your engineering sums. This is also why it had "bent" wings, so they could fit the proper length of landing gear strut and still have some clearance under the prop . With straight wings the landing gear struts would need to be so long that they would reduce the number of machine guns (by rudely occupying the same space when retracted), as well as bouncing the aircraft from a carrier deck when landing. Straight wings and shorter landing gear struts would allow that biggish prop to dig in to the carrier deck (which is frowned on) when the trail hook grabbed a wire and the mass of that huge radial engine tried to pitch the whole aircraft forward (around the main wheels), so bent wings and (almost) normal strut lengths was the right call. It's always a system issue). The prop effect does not exist in a vacuum. Sadly, neither does winged flight.




Total votes: 66

When Suzuki came back to motogp, much was said about their clever mechanical variable valve timing.  I'm assuming they are still using this?  I haven't heard anything about it for a couple of years.  It strikes me thought that, having sprung weights on the cam would do funny things to rotational inertia.  Ordinarily, rotational inertia scales linearly with angular momentum, but, with the spung weight the moment of inertia becomes variable, and no longer scales linearly with angular momentum.

Thinking of this sort of setup on a flywheel, it should allow the engine to accelerate quicker at low speeds, but resist it as the rotational speed got higher.

Total votes: 31

If I recall correctly, the RC211V (or at least the early iterations) had a removable flywheel that alllowed them to easily tailor the amount of crank inertia by just removing a cover.  This was when engine use was open, so was not implied by the rules, it was just an easy way to fiddle with a major part of engine design while they were working out the new 4-stroke class. I'm not sure how much of the external components are allowed to be changed these days, but surely this is worth a revisit?

Surely clutches are allowed to be changed?  What stops Yamaha (or Suzuki last year) from making a tungsten flywheel for their outer clutch basket for example?  OK it is geared down from crank speed but is still part of the crankshaft rotating assembly?

Manufacturers are going to have to start giving thought to having the ability to tune this aspect of engine behaviour within the rules.  Entire racing years are being compromised.

Total votes: 28

despite the problems Yamaha are having, a certain Mr. Rossi and Mr Vinales are sitting in 2nd and 3rd respectively in the championship.  Maybe the problem is....wait for it...Marquez!  If it weren't for that pesky fellow on a Repsol Honda, Yamaha would be doing pretty well I'd say.  My tongue is firmly in my cheek of course.  Not much they can do about Marquez.  I don't think 14lbs. of lead in the arse of his leathers would slow him much.

Yamaha are going to have to make the best of this season and hope for some wins, and/or for the continued inconsistencies of the rest of the top 10.  They could be doing worse at this point in 2018.

Total votes: 28

Interesting to hear Maverick Vinales thoughts on a rider coach & a revealing admission regarding his crew chief.


“It would be difficult for them to teach me much but I’d like Julian Simon, I have a good relationship with him,” says Viñales.

“I’m keen on Esteban because in 2013 he made sure I got the best out of myself, and that’s what I need...."

Total votes: 23