MOTO GP VTwin
MOTO GP VTwin
(OP)
To help keep a cap on power and, hence, speed, the MSMA has decided to propose a reduction in engine capacity from 990cc to 900cc. "The intention is not to reduce performance but to prevent a continuous improvement in speed and lap times," according to the press release.
2004 2007 weight changes
2 Cylinders 135 Kg 133Kg - -2Kg
3 Cylinders 135Kg 140.5 Kg +5.5Kg
4 cylinders 145 Kg 148Kg + 3Kg
5 cylinders 145Kg 155.5 Kg +10.5 Kg
6 cylinders 155Kg 163 Kg +8Kg
The proposed changes to the rules also affect the minimum weight standards, adding more weight to engines with more than two cylinders from 2007.
The proposed changes above may indicate the technical direction that some manufacturers are pursuing for the future. As Honda is the most powerful voice among the companies, it is interesting that the proposed minimum weight for five-cylinder machines, such as the Honda RC211V (and Proton KRV5), has been increased the greatest amount. This may indicate that Big Red is already working on new engine configurations and is looking to abandon the V-5.
And, as two-cylinder bikes are the only ones to get a minimum weight decrease, might we see the introduction of a 900cc MotoGP V-Twin? If so, it wouldn't be as powerful, no doubt, but it would enjoy nearly a 50-pound weight advantage over a V-5-powered machine. And, as a Twin would have a 66-pound advantage over a six-cylinder-powered bike, it looks like the rumors of a Honda V-6 will not be fulfilled.
The MSMA is also looking at perhaps reducing the 2005 rule for a 22-liter fuel tank capacity (down 2 liters from current rules) for the 2007 season.
The introduction of 4-stroke machines to MotoGP has resulted in a huge amount of newfound interest in the class. Now, with revised regulations again on the table, the series might get even more interesting.
The Testastretta engine fitted to the Ducati 998R 2002 version, the bore is 104 mm.
Unfortunately, such a large bore currently causes combustion problems with dramatically decreased efficiency.
This stems fundamentally from the need to augment the injection advance and from the worsening of the "shape factor" of the combustion chamber which, with the reduction of the bore/stroke ratio, becomes ever broader and flatter. The "shape factor" is a critical synthetic value to check a combustion chamber's good operation, and a good indicator of its compactness and "thermal efficiency".
It should be borne in mind that aspirated racing engines require rather extreme valve lift and overlap angles, therefore, cavities are made in the piston crowns to prevent contact with the half-open valves. The combustion chamber is therefore practically contained in the piston cavities, such cavities becoming bigger as the stroke/bore ratio decreases, which makes it hard to obtain the high compression ratios required by high specific power engines.
The Beare sixstroke does not have these limitations because the main lower piston does not have valve cutouts and the combustion chamber is a compact design with squish contribution from both upper and lower pistons. The shape is much more like a fist than a flat hand hence thermal efficiency is high .
Combustion chamber diameter oprox 75mm
The main piston is lighter and stronger than the 4-stroke, because the lack of cutouts allow a thinner slightly domed top
Malcolm does believe that the sixstroke 15kg weight advantage will be a major benefit for the Beare Sixstroke, much more so than the 30kg handicap enjoyed by Twins in 500cc twostroke racing. "Working on the assumption that all these four-strokes are going to make enough horsepower, 15 kilos is a lot," he says. It’s straightforward enough, the Twins will have a 10 percent weight advantage and force equals mass times acceleration, so it is a big difference.
Sixstroke Beare 900cc Vtwin MOTO GP
Bore 116.25 mm stroke 42.5 upper bore 82mm upper stroke 34mm
compression ratio 12.25 to 1
power 337HP @ 15000 RPM
torque 74.6Ft/Lbs x80% x2 = 118Ft /Lbs
piston speed at 18000 is 5019 Ft/min or 25.4965 Mtre / sec
XL engine file
Torque 101.2 NM or 74.6 Ft /Lbs discount by 20% and multiply by 2 for twin cylinder is 118 FT/ Lbs
6 port design with 3 exhaust ports leading to a rotary disk, 3 intake ports,One intake rotary disk and 2 reed valves with air assisted injectors. 2 or 4 10mm plugs per cylinder.
The port area is oprox 20% to 30% more than a 4 valve head
Results of XL file sixstroke touque calculator
Based on Dual Cycle
Total Torque
Fourstroke 62.00
Main Top
66.05 35.15 101.20
Increase in torque 63.23%
www.jack-brabham-engines.com/
Malbeare
2004 2007 weight changes
2 Cylinders 135 Kg 133Kg - -2Kg
3 Cylinders 135Kg 140.5 Kg +5.5Kg
4 cylinders 145 Kg 148Kg + 3Kg
5 cylinders 145Kg 155.5 Kg +10.5 Kg
6 cylinders 155Kg 163 Kg +8Kg
The proposed changes to the rules also affect the minimum weight standards, adding more weight to engines with more than two cylinders from 2007.
The proposed changes above may indicate the technical direction that some manufacturers are pursuing for the future. As Honda is the most powerful voice among the companies, it is interesting that the proposed minimum weight for five-cylinder machines, such as the Honda RC211V (and Proton KRV5), has been increased the greatest amount. This may indicate that Big Red is already working on new engine configurations and is looking to abandon the V-5.
And, as two-cylinder bikes are the only ones to get a minimum weight decrease, might we see the introduction of a 900cc MotoGP V-Twin? If so, it wouldn't be as powerful, no doubt, but it would enjoy nearly a 50-pound weight advantage over a V-5-powered machine. And, as a Twin would have a 66-pound advantage over a six-cylinder-powered bike, it looks like the rumors of a Honda V-6 will not be fulfilled.
The MSMA is also looking at perhaps reducing the 2005 rule for a 22-liter fuel tank capacity (down 2 liters from current rules) for the 2007 season.
The introduction of 4-stroke machines to MotoGP has resulted in a huge amount of newfound interest in the class. Now, with revised regulations again on the table, the series might get even more interesting.
The Testastretta engine fitted to the Ducati 998R 2002 version, the bore is 104 mm.
Unfortunately, such a large bore currently causes combustion problems with dramatically decreased efficiency.
This stems fundamentally from the need to augment the injection advance and from the worsening of the "shape factor" of the combustion chamber which, with the reduction of the bore/stroke ratio, becomes ever broader and flatter. The "shape factor" is a critical synthetic value to check a combustion chamber's good operation, and a good indicator of its compactness and "thermal efficiency".
It should be borne in mind that aspirated racing engines require rather extreme valve lift and overlap angles, therefore, cavities are made in the piston crowns to prevent contact with the half-open valves. The combustion chamber is therefore practically contained in the piston cavities, such cavities becoming bigger as the stroke/bore ratio decreases, which makes it hard to obtain the high compression ratios required by high specific power engines.
The Beare sixstroke does not have these limitations because the main lower piston does not have valve cutouts and the combustion chamber is a compact design with squish contribution from both upper and lower pistons. The shape is much more like a fist than a flat hand hence thermal efficiency is high .
Combustion chamber diameter oprox 75mm
The main piston is lighter and stronger than the 4-stroke, because the lack of cutouts allow a thinner slightly domed top
Malcolm does believe that the sixstroke 15kg weight advantage will be a major benefit for the Beare Sixstroke, much more so than the 30kg handicap enjoyed by Twins in 500cc twostroke racing. "Working on the assumption that all these four-strokes are going to make enough horsepower, 15 kilos is a lot," he says. It’s straightforward enough, the Twins will have a 10 percent weight advantage and force equals mass times acceleration, so it is a big difference.
Sixstroke Beare 900cc Vtwin MOTO GP
Bore 116.25 mm stroke 42.5 upper bore 82mm upper stroke 34mm
compression ratio 12.25 to 1
power 337HP @ 15000 RPM
torque 74.6Ft/Lbs x80% x2 = 118Ft /Lbs
piston speed at 18000 is 5019 Ft/min or 25.4965 Mtre / sec
XL engine file
Torque 101.2 NM or 74.6 Ft /Lbs discount by 20% and multiply by 2 for twin cylinder is 118 FT/ Lbs
6 port design with 3 exhaust ports leading to a rotary disk, 3 intake ports,One intake rotary disk and 2 reed valves with air assisted injectors. 2 or 4 10mm plugs per cylinder.
The port area is oprox 20% to 30% more than a 4 valve head
Results of XL file sixstroke touque calculator
Based on Dual Cycle
Total Torque
Fourstroke 62.00
Main Top
66.05 35.15 101.20
Increase in torque 63.23%
www.jack-brabham-engines.com/
Malbeare
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare





RE: MOTO GP VTwin
It looks as though you did not add the displacement of the upper pistons. They are not just valves but also change the cylinder volume. I get 1261cc which is over the current or proposed limit. 1261/900 * 337 = 240 HP which is in the relm of current MotoGP engines.
The Brabham site did not say what the other two strokes were. Just gave the common four. The PV diagram looked to be more Diesel than Otto cycle.
With a 116.25mm bore you would probably have to go with four plugs to keep the flame travel short enough.
RE: MOTO GP VTwin
Things are a little more complicated than you would expect
During the intake stroke the main piston is increasing the cylinder vollume while the upper piston is decreasing the volume ( half of its stroke) so the net change in vollume is +722cc . During the comptression stroke the upper piston is still reducing vollume ( half its stroke) while the main piston is also reducing vollume, net change -1082cc.
During the expansion stroke the upper piston is increasing the vollume ( half of its stroke) while the main piston is increasing vollume, also net change +1082cc.
During the exhaust stroke the upper piston is increasing vollume ( half of its stroke ) while the main piston is decreasing vollume, net change -722cc
if you add all the strokes together and average them you get 900cc
The story changes again when you phase the coordination of upper and main pistons but the average remains constant.
The combustion chamber is only aprox 75 mm in diameter maybe 2 plugs will be OK.
http://www.jack-brabham-engines.com/
malbeare
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
I saw the upper piston runs at half engine speed but it was not clear from the model how the porting and disc valves worked. Presumably the intake disc allows the intake piston port to open first, then the exhaust. After the exhaust phase the intake disc opens and exhaust disc closes to start the intake phase.
Possibly the main advantage is moving the peak pressure further away from TDC (17-20 degrees ATDC in a SI engine) to get more torque at the crank from the same expansion.
Unless the spark can be moved a lot closer than the typical 38 degrees BTDC at full advance, you are still sparking in a 116.25mm diameter chamber. Unless the lower piston reaches TDC and ignition occurs in the smaller upper chamber?
RE: MOTO GP VTwin
The exhaust disk closes and intake continues.
the upper piston closes all the ports at aprox 60ATDC and compression begins. I have found it to be most advantageous to retard the upper piston in its relationship with the main piston by between 10 and 20 degrees to have peak cylinder pressure at the upper pistons TDC or aprox 15degs ATDC ignition timing advance seems to be best at aprox 25 degs advance.
The cycle has some similarities to the Miller and Atkinscycle in that the intake volume is less than the expansion volume.
It would be wise to get a ruling before we build .
Malbeare
http://www.jack-brabham-engines.com/
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
RE: MOTO GP VTwin
Grab my trusty old 9-inch angle grinder and dismantle the garden gate to build a 1-inch square tube trellis.
Seriously
The front end will be a Hossack, BMW, Brittin style with a few quirks of my own to make it rapidly adjustable aircraft style swing arm out of folded alloy with under slung pull shock or monoshock. A styled carbon fiber canopy after looking at all current GP bikes all mounted from strategically placed lugs on the engine. Small front coolers augmented by side and under seat coolers radiators. The engine having such a short stroke will be a very compact package smaller than currently available 1-liter V twins. Not much frame at all
Malbeare
http://www.jack-brabham-engines.com/
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
RE: MOTO GP VTwin
I am open to any suggestions or you can send me a private message at malbeare@ozemail.com.au
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
Get up all the cash you can and steal Valentino away from Yamaha.
RE: MOTO GP VTwin
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
RE: MOTO GP VTwin
Incredible the way the Yamaha is set up now , He raised the engine 20mm to raise the CoG and reversed its rotation to counter the gyro effect effectivly making the bike neutral by having the engine rotation cancel the wheels, thus making it very easy to flick through the corners.
It did not matter that the engine reversal robbed 5% power because of the extra gearshaft required.
Maybe the heads on the Beare could run in the reverse direction a lar Ducati to at least make the engine gyro nuetral using the disks as gyros.
Malbeare
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
When designing the geometry of the front end, do not forget to decrease trail with compression to keep the steering from getting too heavy while braking.
I believe the Yamaha already had the reverse rotation when they changed to the big bang firing order. They had to add a balance shaft which I believe is between the crank and clutch. Precession is right angles to the spin and applied force. Engine rotation direction effects the front/rear loading as the bike is transitioned in lean.
RE: MOTO GP VTwin
This is part of what we are considering for the front end.
Linkages may be difficult to place the shock next to the engine. Great input thank you
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
If you use the swingarm/slider or double wishbone suspension it is relatiely easy to link shocks mounted alongside the engine. Obviously does not work with USD forks.
I hope you are tying the trellis across the frame and adding a sheer web behind the headstock. The torsional stiffness will be fairly low without it.
RE: MOTO GP VTwin
http://www.ozebook.com/alchemy.htm
The Alchemy uses this sort of shock arangement for the swingarm. Any comments about using nitrogen filled air bag instead of a spring . There may be an issue with placement as we have exhausts exiting from the side of the head instead of foward or backwards.
Malbeare
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
Air shocks have not been in favor because of the rising rate with compression. You can fix that with a linkage but the damping will not match the spring at all deflections. That could also be fixed with an electronically variable damper.
Unless the link is forward on the swingarm in the torsionally stiff section you will induce twist with deflection. A problem with single sided arms also, trying to keep twist out of the swingarm deflection.
The exhausts can be bent to wherever necessary. Ceramic wrap or a heat shield can be used around sensitive parts.
RE: MOTO GP VTwin
If your main objective is to developer the engine then use a conventional chassis with Ohlins forks and metallic springs.
It is very easy to get caught up in re-inventing the wheel, but when you are starting with something new and untested you do not want to bite off more than you can chew.
Another benefit of using more conventional suspension would be the ability to get support from Ohlins. Using ABC suspension is just great, but what type of setup help are they going to provide?
Once you get the engine working to where you feel comfortable, then turn your attention to the chassis.
RE: MOTO GP VTwin
Good advice dont re-invent the wheel too much.
Twin shocks on the rear to allow a shorter swing arm and good accsess to the rear head.
http:
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front suspension with single shocker spring.
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
RE: MOTO GP VTwin
I think that is one of the things that really hurt Aprillia in their attempt in MotoGP. They just had to run all this high tech stuff such as pneumatic valves and throttle by wire for example and could not make it work as it needed to on the track.
Alot of people get wrapped up in one aspect of bike, and I am not saying that this is you, that they fail to see that the key to being successful is that all the parts need to be able to be integrated into the whole package.
They talk about dyno numbers and this number and that number. None of it is important, in racing the only numbers that are important are lap times. What good is having 10 more hp on the field if you are 2+ seconds off the pace?
RE: MOTO GP VTwin
Srad
RE: MOTO GP VTwin
The first test by my rider Phil Allen ( national Australian Bears Champion)he told me that the bike tended to tuck in to the corners. So I extended the front forks by 40mm and it handled superbly, notwithstanding my garden gate trellis frame and Suzuki gs rear wheel and Yamaha fzr front end and my own design swing arm box section RHS with twin Koni shocks. The swing arm pin pivoted in the frame as well as the normal ducati engine mount.During a photo shoot in France a race rider jurnalist took it for a few laps. I told him that it was only a prototype and to take it easy.The second lap he took one eigth of an inch of rubber off both tyres and broke the clutch and something else. so the handling inspired confidence.we got it running again in 24 Hrs.
The power tended to fall off after 7000RPM. I have since worked on that aspect and can report that we are producing about 40 % more power . The original 4 stroke engine would rev to about 7000 in top gear on my fan dyno. we are now getting 10000 with the sixstroke but not reliably as something goes bang every now and then.So we have to re-engineer a new motor for the concept.
SRAD,
it is not that it cant be done in an inline 4 it is just a little bit simpler in a V4 and I think a tighter package is more suitable to help meet the new pedestrian safety legislation with bonnett crumple zones.
But of course my passion is for motorcycle racing.
http://www.jack-brabham-engines.com/
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare