Oddball engines and prototypes

[J.A.W.]

There is still a bit of support about for those big old 2-stroke terrors.. wanna 128hp H2 roadbike? www.ebos.se/eptune-triples.php

[malcy25]

Dogmatic.. is 'stick in the mud' M-25, - not "heretic", which indicates ( an unwelcome to dogma) readiness to consider change.

Anyhow, if the TZ inline 4 is ordinarily capable of hacking a double firing impulse - crank & trans-wise..
It surely, stands to reason - that dividing those by 1/2 - is going to even out/reduce those extant force-node peaks.. & this carries across the board to rideability.

Yamaha uses the 90`configuration in its current inline R1/M1 4s - as a way of emulating the natural V4 architecture - dynamic recip - process outcomes..

AFAIR, Harry Bartol's G.P. KTM - in its final 250cc iteration - was also doing this ( vertical twin emulating V-twin firing), so there had to be real value in it..

JAW: best you buy a new dictionary, as it appears your current one is broken. Oxford says: Heresy "opinion contrary to doctrine of christian church, or to accepted doctrine on any subject." Frits has expoused a different opinion to my perception of which is better - hence my heretic comment at my expense given his knowledge. Heretic works.

It seems you continue to miss the final point in the equation as far as I reckon: The concept of a 90 degree firing phasing on a twin vs a four 2 stroker is quite a different situation. A 90 degree twin like the KTM's did, delivers a 270 degree down period where the perceived wisdom is that this provides the rest period for the tyre. My view is that 90 degree phasing on a 4 cylinder 2 stroke (such as a TZ750) is moot, as it would fill the 270 degrees of down the twin has with the additional cylinder firing, as it would be 0/90/180/270....ie less downtime, and as Frits said about Honda in the link he provided, even Honda ditched this option.

If I had the money to throw at it (But as a poverty stricken road racer that is unlikely to happen), I would like to try a 90 degree crank in my twin. Others already have I believe, but little or no "this is the way ahead" feedback have I heard. But on a 4, nah.

An R1 4 stroke has different dynamic in that it has 720 degrees of crank rotation to fire and group 4 cylinders, so you can create big gaps and get the same effect as the KTM with 270 dgree gaps in places.It also has something that old strokers don't have. A balance shaft.....to correct all those random shakes.

While what you refer to with torque loading aspect on the gearbox etc is "nice", my belief (and happy to be proven wrong with logical proof) it is not so good on the rear tyre. The gear box is built for it, I'm more interested in what the rear is doing as that has a bigger impact on the skin on my arse and my cheque book. You refer a lot to the torque loading and fluctuation from an engineering sense, citing Manolis, but as I've alluded to previously, there is a wider need than purely engineering, the less tangible, but real impacts about feel, tyre and on track dynamics that don't show through pure engineering. I guess it's why GP teams test. Newer, or better design does not always make a better result.

I learned years ago that Suzuki engineers built an odd firing order or big bang RG500 gp bike (like in the early 80's). But as they didn't see any difference on the dyno, they didn't give it to anyone try....I think that fits under the "if only" heading! Imagine if they had. In the same manner, I run a specific jetting set up on one of my bikes that provides no better dyno curve than another set up. But I run the one I do because the "feel" is different and more to my liking. Pure engineering view would say "why bother"

Rgds

[J.A.W.]

JAW: best you buy a new dictionary, as it appears your current one is broken. Oxford says: Heresy "opinion contrary to doctrine of christian church, or to accepted doctrine on any subject."

Still being disingenuous I see, the 'heresy' was mine, according to your 'stick in the mud' dogma, in this actual instance..

& FYI, Mick Doohan reverted to 'screamer' firing order for his NSR 500, & which was duly retained by JB for V. Rossi et al, 'til the end of 500s..

[malcy25]

Still being disingenuous I see, the 'heresy' was mine, according to your 'stick in the mud' dogma, in this actual instance..

& FYI, Mick Doohan reverted to 'screamer' firing order for his NSR 500, which was retained by JB for V Rossi, 'til the end of 500s..

1) Heretic: I used it first. is what it is. Build a bridge.

2) Disingenuous, "not candid or sincere, typically by pretending that one knows less about something than one really does" . hmmm thanks for the flattery.

3) Doohan. Yes, I referred to that a while back, and why.

4) have you anything useful to add to the discussion yet?

[J.A.W.]

1) Heretic: I used it first. is what it is. Build a bridge.

2) Disingenuous, "not candid or sincere, typically by pretending that one knows less about something than one really does" . hmmm thanks for the flattery.

3) Doohan. Yes, I referred to that a while back, and why.

4) have you anything useful to add to the discussion yet?

Too funny, & inaccurate as usual..

So here are some facts, to straighten out your curly ones..


1, I used it before you.. re-check post #3528 in the 9/11 thread which refers to this very topic.. ( & dont claim you aint already bloody seen it)..

2, Cap fits, wear it..

3, You dismissed the Doohan 'screamer' re-uptake, & ( slyly, or ignorantly) failed to include the material fact - of the configuration being retained from then on..

4, I was the person who, ah, yeah.. actually started the topic for discussion.. see post #435, this thread..
( & have you canvassed your good buddy Wobbly's consideration of the topic - yet?)

[Frits Overmars]

A 90 degree twin like the KTM's did, delivers a 270 degree down period where the perceived wisdom is that this provides the rest period for the tyre.... 90 degree phasing on a 4 cylinder 2 stroke (such as a TZ750) is moot, as it would fill the 270 degrees of down the twin has with the additional cylinder firing, as it would be 0/90/180/270....ie less downtime.

I'm sorry to contradict you Malcy, but the 'rest period for the tire' is persistent incomprehension rather than perceived wisdom. The tire is there to work, not to rest, as I already tried to explain in http://www.pit-lane.biz/t1461p32-tec...moteurs-motogp. You really should take a look there.

[J.A.W.]

Somehow, I doubt this one has a 180`crank phasing set-up.. http://www.4x4tuff.com/ctsme8.html

[husaberg]

I'm sorry to contradict you Malcy, but the 'rest period for the tire' is persistent incomprehension rather than perceived wisdom. The tire is there to work, not to rest, as I already tried to explain in http://www.pit-lane.biz/t1461p32-tec...moteurs-motogp. You really should take a look there.

Hello Frits I read your pitlane post with great interest i too am struggling to see the possible improvement. in the case of the TZ750

Doohan didn't like the initial big bang either, Lawson said exactly the same but set the first pole on the Cagiva as soon as the Cagiva was converted to fire alll the cylinders within 0-80 degreess
but both became a convert when he realised the lap times were the same and tire wear was less allowing him to use stickier tyres.
Both also said it was easier to ride.
This one thing in your pitlane post stands out as being counter productive.

Honda even built a 'big bang-screamer': every 90° 1 cylinder firing. That sounded great! But Mick Doohan did not like the bike, so it disappeared....

Is this not exactly what is being proposed here?
My understanding is the dominant 1990's big bang Honda NSR500 which debuted in 92 fired all of its four cylinders within 0-70 degrees.
This was a redesigned engine with a center power take off they also put in a Counter balancer which i also understand helped get rid of the gyro.(the other twin crank V4's never had as soon as Yamaha counter rotated them in the early 80's)
According to everyone at the time. The Honda (as were all the other bikes that were hastily converted to similar firing orders )were actually dramatically easier on tires than it was previously.

They felt slower and were more vibely they suffered reliabilty wise from the hasty conversion (ESP Yamaha and Suzuki).
As they were not designed for it unlike the Honda engine that was, but the lap times went down.
The bikes were easier to ride.
All the other manufacturers then followed suit. Reporting the same thing.
In the same season with Doohan injured Cagiva's were initally more succesfull than the others,even setting their first pole first time out with the big bang, lap times for them fell instantly these were all on the same tyres as previously.

All Honda V4's up to 1989 were 90 degree firing orders in 1990 they went to 180 same as the others. ie two up two down same as a TZ750 this was an improvement

V4 2-Stroke NSR500 up until 1989
000----090----180----270----360
-1-------3--------2-------4-------1-

Screamer - V4 2-Stroke (180 degree motor) NSR500 90-91 and then 1997- onwards
000----090----180----270----360
1&3------------2&4------------1&3

Big Bang - V4 2-Stroke NSR500 1992-1997
000----090----180----270----360
-1-3-2-4---------------------1-3-2-4

Doohan's crew chief Jerry Burgess believes the 1990 NSR was the best ever - a huge leap forward. HRC dumped the 90-degree firing order, copying the more forgiving Yamaha's double-strike 180-degree configuration to tame wheelspin.
The 180-degree motor was good but not good enough and still prone to chucking riders over the highside, so excess caution was necessary on corner exits. Doohan

With the engine untouched since crossing the finish line in Brazil, track time on the Rossi bike was cut to the bare minimum. HRC boss Ikenoya revealed that the crankshaft's service life is now 3000km, but the piston rings need changing more often than that, and Jerry Burgess and Co were probably too busy celebrating and preparing to test the V5 four-stroke to do this in the three weeks before our test. But even with just a handful of laps in the hot seat, I immediately appreciated the smoother power delivery from low down, with a less abrupt transition into the strong power zone just above 10,000rpm, but an even stronger hit of top-end power than before. It's a lot easier for 500cc dilettantes to master, and even more of a thrill to twist that throttle grip and force your body weight over the front wheel while accelerating down pit lane towards your appointment with destiny and the moment to think about stopping for turn one. Phew!

The Honda's 112-degree V4 engine has a "Screamer" format that employs 180-degree crank throws and evenly spaced "two-up" firing strokes, thanks to a crankshaft layout that sees the two right-side pistons sparking together, followed 180 degrees later by the two left-side ones. The 5% power loss inflicted by unleaded fuel has taken the razor edge off the Screamer's power delivery. Coupled with better electronic engine-management systems developed in the past decade, this has helped HRC engineers tame the engine's character, while reaping the benefits of its smoother power delivery and more direct throttle response. The Rossi Honda certainly has the usual NSR500 shopping-trolley power delivery low down, pulling cleanly from about 7000rpm out of a tight hairpin before coming on strong about 10,000rpm, when the shrill-sounding note of the slimmer exhausts hardens.

A strong surge of midrange power catapults you down the next straight, especially if you short-shift about 12,000rpm in lower gears, lifting the front wheel in second, third, and, yes, fourth gear down the pit straight as you gas it wide open out of the last turn. It's fearsomely fast, but fun ... until you come to ride it at the pace of the last 5% needed to win world titles. Then it becomes very, very serious and very, very hard.

Peak power is delivered at 12,500rpm, and you should change gear soon after to put yourself right back in the midrange zone and ride the V4 engine's meaty torque curve, as you hit the higher gear. But what's this? A powershifter on an NSR500? First time I've ever used one on a 500 Honda.

While i totally agree that a even firing order of every 90 degrees will allow for a smoother engine with higher power potential and lighter parts.
To make the most of this advantage would entail redesigning the engine from scratch to make the most of this advantage.

Conversly the TZ750 which has a wide crankshaft due to its layout as a inline 4 dictating cylinder spacings and a wide crankshaft joined in the middle
It fires the cylinders in pairs inner together then outer together, my understanding is this was not down out of expediancy of using 180 cranks (ie similar as the twins or easier ignition) but necsessity of reducing the rocking couple.

Retired Yamaha engineer Takashi Matsui recalls the start of the development project: “We were intending to eventually participate in the GP500 class so we started work on a 500cc model, but at the same time we had our eyes on Daytona. So we started developing a 700cc models simultaneously, calling the 700cc the “YZ648″ and the 500cc the “YZ648A.” By October of 1971 we had completed three prototypes to the point where they were running fairly well. Then we spent all of 1972 developing the finer details of the machines, which were now being referred to by their development code names “OW19″ (700cc) and “OW20″ (500cc).”

A number of innovative features were developed during that year. “In order to get a much slimmer engine design, we grouped the four cylinders into units of two each and then introduced an “idle shaft” between the right and left crank shafts as the drive force shaft. The enabled an engine width about the same as a V-4. And to make the overall design even more compact, we fitted the ignition system in the space on the non-drive end of the idle shaft axis,” adds Mr. Matsui.
“From our experience developing the RD05 (the 1964 250cc GP machine) we learned that the ignition order has a big effect on the idle gear, and so we decided to use a well-balanced firing order in which the two inside cylinders and the two outside cylinders fired at the same time.

http://www.kiwibiker.co.nz/forums/at...0&d=1438073578

Yamaha it seems reconised this with the R1 flat plane by giving it a balance shaft especially designed to assuage the rocking couple vibration. (well thats what they say other than assuage thats why little improvement)

That said Honda went back to the 180 layout later again same as a TZ750 People refer to this as a screamer I call it long bang but electronic engine management had got vastly better, fuels had changed to LL (making them the power curve less abrupt)and tyres had vastly improved.

For '97 Doohan decided he wanted to run a 180-degree motor. HRC didn't like the idea but he was mighty fast during first tests
knew he could regain an advantage with the engine, for engine management technology made it more rideable than the old 180-degree V4s and tire technology had caught up too. Plus the screamer sounded so much better.
"The 180 got back a direct relationship between the throttle and the rear wheel," he says. "When the tire spun I could roll off without losing drive." 98 brought into effect unleaded and made this engine managable again

But by all reports this bike was not as forgiving to ride for most others not used to it.
I can't see how a TZ750 on its skinny rims and old style tyres could be faster arround a track with a less than demigod rider in place
I am aware disagreeing with you on technical maters is fraught, as you are a fair bit smarter than I am, so what am i missing?

re the tyre rest theory i think the originator of that theory was actually Kiwi ex KR man Mike Sinclair

http://www.superbikeplanet.com/NSR500.htm
https://ultimatemotorcycling.com/201...acing_history/
http://www.motorcycletrader.co.nz/re...sr500-nz-2002/
http://www.mcnews.com.au/thirty-year...-racer-part-1/
http://www.kiwibiker.co.nz/forums/al...id=4837&page=7
http://www.kiwibiker.co.nz/forums/al...id=4837&page=6

[J.A.W.]

Hello Frits I read your pitlane post with great interest i too am struggling to see the possible improvement. in the case of the TZ750



While i totally agree that a even firing order of every 90 degrees will allow for a smoother engine with higher power potential and lighter parts.
To make the most of this advantage would entail redesigning the engine from scratch to make the most of this advantage.

Conversly the TZ750 which has a wide crankshaft due to its layout as a inline 4 dictating cylinder spacings and a wide crankshaft joined in the middle
It fires the cylinders in pairs inner together then outer together, my understanding is this was not down out of expediancy of using 180 cranks (ie similar as the twins or easier ignition) but necsessisty of reducing the rocking couple.
Yamaha it seems reconised this with the R1 flat plane by giving it a balance shaft especially designed to assuage the rocking couple vibration.

Husa, you are failing to grasp that the rocking couple is reduced by the 90` config'.. ( see the Manolis link) & the TZ would live longer with less needless internal stress..

[J.A.W.]

TZ 750 returned to the track feature.. http://www.cycleworld.com/2015/07/07...he-race-track/

[J.A.W.]

Yamaha big G.P. 2T race history feature.. http://www.big-diesel.blogspot.com.a...om-yamaha.html

[J.A.W.]

Paul Gast is still putting big HP H2s together too.. www.fastbygast.com/H-2%20parts.htm

[malcy25]

Too funny, & inaccurate as usual..

So here are some facts, to straighten out your curly ones..


1, I used it before you.. re-check post #3528 in the 9/11 thread which refers to this very topic.. ( & dont claim you aint already bloody seen it)..

2, Cap fits, wear it..

3, You dismissed the Doohan 'screamer' re-uptake, & ( slyly, or ignorantly) failed to include the material fact - of the configuration being retained from then on..

4, I was the person who, ah, yeah.. actually started the topic for discussion.. see post #435, this thread..
( & have you canvassed your good buddy Wobbly's consideration of the topic - yet?)

Oh the shame of it. See Husa's post from last night....

Screamer - V4 2-Stroke (180 degree motor) NSR500 90-91 and then 1997- onwards
000----090----180----270----360
1&3------------2&4------------1&3

Hmmm, seems like they were on to a good thing,


care to comment?

[ken seeber]

Dunno what has happened here, but a little while ago it all seemed so friendly. Bit of romanticising, some interesting things, the products of lots of individual and or company efforts and hard work, zany inventions, etc. When you look at each old bike or engine or whatever, successful or a total failure, it just reminds one of the passion and commitment that went into it. Going home every day, lying in bed, thinking about it and what you’d do the next day, waking up, enthused and going to work to do it. Getting it to work, a dud or a screaming success. Doesn’t matter really, you have put in the effort. One that we all seem to enjoy and look back at. Fuck, I just love passion and commitment
So, fellers, can you please respect this, not try to outdo the other as to who’s correct or more correct. You are clever and smart guys, clearly capable of drawing out the info, presenting lots of facts, some right, some wrong, some arguable, but we, or at least me, the audience, the accuracy it not the key just the abundance of interesting info and the learning of things that we missed all those years ago.
Cheers

[husaberg]

Dunno what has happened here, but a little while ago it all seemed so friendly. Bit of romanticising, some interesting things, the products of lots of individual and or company efforts and hard work, zany inventions, etc. When you look at each old bike or engine or whatever, successful or a total failure, it just reminds one of the passion and commitment that went into it. Going home every day, lying in bed, thinking about it and what you’d do the next day, waking up, enthused and going to work to do it. Getting it to work, a dud or a screaming success. Doesn’t matter really, you have put in the effort. One that we all seem to enjoy and look back at. Fuck, I just love passion and commitment
So, fellers, can you please respect this, not try to outdo the other as to who’s correct or more correct. You are clever and smart guys, clearly capable of drawing out the info, presenting lots of facts, some right, some wrong, some arguable, but we, or at least me, the audience, the accuracy it not the key just the abundance of interesting info and the learning of things that we missed all those years ago.
Cheers

My thoughts exactly