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Honda F1 V12 1966


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#1 blueprint2002

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Posted 03 August 2020 - 14:55

Honda’s second F1 engine was the RA273 V12 of 1966-68, the opening years of the new 3-litre formula. It was remarkable in several ways, though it never received the attention it merited. Even today, only a few basic facts are known, and to my knowledge, no drawings have been made public, nor any technical description.

To start with, the angle between the banks of cylinders was 90 degrees, not the usual 60 degrees that remains the first choice even today (for very sound technical reasons). Another unusual feature was the output drive, taken from the middle of the crankshaft (between the third and fourth cylinders of either bank) rather than from its rear end.

At that time, only three recent racing engines had featured the exhaust ports between the cylinder banks, inside the V, and inlet ports outside (Repco, BRM and Ford Indy, each possibly for rather different reasons). The Honda RA273 was also arranged that way, for reasons that are not readily apparent.

According to the “History of the Grand Prix Car 1966-85”, the wide angle was chosen because the output shaft, running below the crankshaft, caused the entire engine to be raised up. The wide angle brought the cylinder heads lower down again, lowering the CoG in consequence, so as to compensate for the rise, at least in part.

But why take the drive from there, rather than from the usual place? For a transverse engine (Honda RA272, Bugatti T251, various motorcycles), it makes architectural sense, quite apart from any engineering reasons that might also apply. For a longitudinal engine, there must be pressing engineering demands that override the architectural disadvantages.

Perhaps the best precedent for this was the Mercedes Benz M196 Grand Prix engine of 1954-55. A straight-8, it too had the output, along with all auxiliary drives, taken from between the fourth and fifth cylinders. Although I have not seen an explanation for this, it is likely that it was to overcome torsional vibration, which tends to afflict long crankshafts. Two short (4-crank), shafts are around twice as good as one long, (8-crank) shaft, in this context. Even so, the M196 crankshaft has a torsional damper at each end; logically therefore, the full-length shaft was otherwise beyond help.

On the other hand, recent and contemporary racing and high performance V12s, from other makers, showed little or no evidence of such difficulties (Ferrari, Maserati, Eagle etc). But Honda had considerable experience of crankshafts driven, at very high RPM, by multiple small capacity cylinders, and had successfully overcome all the associated problems, torsional included. Is it likely, then, that the RA273 engine incorporated that experience, possibly as a precaution, rather than as the solution to an observed problem?  

The 90-degree angle between the cylinder banks rather complicates the situation. Assume, in the absence of any data, that the crankshaft was arranged in the usual manner of the 60-degree V12, with six cranks, spaced at 120 degrees, each carrying one big end from each bank. With a “conventional” V12, this would give equal firing intervals of 60 degrees for all cylinders, resulting in the very smooth torque, even at low RPM, that V12s normally produce. But with that 90-degree angle, even firing is no longer possible, in fact it will occur at intervals of 30, 90, 30, 90….  degrees, which is a major deviation from 60, 60, 60…. degrees.

The engine torque output over one cycle (2 revolutions) will now exhibit six lofty and lumpy peaks, separated by six bumpy hollows. Even this might possibly be noticeable to the driver only at rather low RPM, but its effect on torsional vibration could be a very different matter. Impossible to tell without detailed analysis, but there is scope for trouble, as the magnitude of each harmonic of the cycle frequency will be radically different, and its effect on the crankshaft as a whole will change accordingly. (Of course, it could change for the better, not necessarily for the worse).

So the question is: did the 90-degree angle come first, and the centre drive later, or was the centre drive the cause of the 90-degree angle?

The exhaust ports within the V are not easy to account for, because they raise the CoG, already a problem as described above. Could it be that it was done so as to give enough space on either side of the engine for substantial “wheelbarrow arms” on the monocoque, (as also favoured by BRM for the P261), space that the exhaust system would otherwise intrude upon? Or to tuck the exhaust headers behind the drivers head, hopefully to minimise aerodynamic drag?

 

 



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#2 ray b

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Posted 07 August 2020 - 21:15

it was fad in the 60's to do the in between the V thing FOR THE PIPES

 

I think honda just copyed what the others did

 

never did see a real reason

 

the 66 Honda car thru mid 67 was a dog  lots of power and WEIGHT

 

then they won with a lola car they shoehorned their v-12 motor in to a lola INDY CAR that john demanded to get the weight down

I think that is the last win monza 67 for a non-built to be a f-1 car on the record not counting jack's f-2 cars he up-graded



#3 ray b

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Posted 07 August 2020 - 21:36

60's honda f-1 cars were different

but maybe the 65  1.5 cars sideways motor was the root of the 3.0 motor using the center power takeoff  ?



#4 Greg Locock

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Posted 07 August 2020 - 23:37

You use centre power take off with high revving engines with long cranks. This allows you to split the crank into two, getting rid of many of your torsional vibration problems. I worked on one V12 where this was proposed, the program manager got all excited about it and thought we were going to start patenting innovations. Mercedes used it pre war. It's actually very hard to do anything mechanically automotive that Lanchester or Merc hadn't done already!



#5 PJGD

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Posted 08 August 2020 - 00:55

Here is an example from Lotus: 

 

PJGD



#6 Greg Locock

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Posted 08 August 2020 - 06:33

You've been stood up!



#7 PJGD

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Posted 09 August 2020 - 01:02

I goofed; this link got left off: 

https://patents.goog...en?oq=WO9116530

 

PJGD



#8 Greg Locock

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Posted 09 August 2020 - 02:22

Oh, He went ahead and patented it! How odd, the crank isn't split in that version. 



#9 Charlieman

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Posted 09 August 2020 - 10:36

For monocoques, there are four main ways to mount a rear engine:

* Tubular sub-structure behind the driver/fuel tank bulkhead. Common for F5000 cars with V8 engines and inconvenient side exhaust systems. Pity the poor mechanics.

* 'Horn' projecting from the driver/fuel tank bulkhead on which a V or flat engine was suspended. Requires side exhausts, of course.

* 'Wheelbarrow Arm' swooping to pick up a V or straight engine. Elegant solution used for 1.5 litre F1 V8 engines etc. Some designs used the arm as a fuel tank. Requires exhausts inside the V (exceptions?).

* 'Direct attachment' to the driver/fuel tank bulkhead. Cosworth/Lotus get most of the credit for this but Ferrari had used it previously in F1. There's a variant for production engines in junior formula cars -- rigid plate plus blocks or offset brackets (attributed to John Barnard, Lola SuperVee).

 

Honda used Horn and Wheelbarrow Arm chassis designs, depending on engine layout, if my memory still works. It seems that there were a lot of ideas in the pot at Honda and a lot of energy to try them out, little continuity in concepts and poor rewards for such an innovative bunch. English and European language histories of Honda may not have captured the mindset of the time.

 

High exhaust CoG could be offset by using lighter materials. Titanium was becoming fashionable, with reported figures being 30lb plus saving for a big engine.



#10 PJGD

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Posted 10 August 2020 - 00:06

Oh, He went ahead and patented it! How odd, the crank isn't split in that version. 

 

Figure 3 shows a split crank with intermediate bolt-together center main bearing and gear cluster. . .



#11 gruntguru

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Posted 10 August 2020 - 00:44

So Lotus enhances an age-old design by using two gears, helical teeth and is awarded a patent?



#12 Greg Locock

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Posted 10 August 2020 - 01:54

You must be aware how lousy the patent process is. It is very rare for an automotive patent to actually work as designed, the ones that did was Toyota's and Ford's cross licensed patents on HEV powertrains, which forced GM to develop the Volt in a fit of NIH rather than pay royalties.



#13 Alan Baker

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Posted 10 August 2020 - 09:14

 

* 'Wheelbarrow Arm' swooping to pick up a V or straight engine. Elegant solution used for 1.5 litre F1 V8 engines etc. Some designs used the arm as a fuel tank. Requires exhausts inside the V (exceptions?).

 

Exceptions? Well, every Lotus 25/33, whether with Climax or BRM V-8s. The 1964 BRM P261s had to have slots in the horns to take the side exhaust engine after delays with the centre exhaust version.



#14 Charlieman

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Posted 11 August 2020 - 13:02

Exceptions? Well, every Lotus 25/33, whether with Climax or BRM V-8s. The 1964 BRM P261s had to have slots in the horns to take the side exhaust engine after delays with the centre exhaust version.

Thanks, Alan. I was juggling memories in my head, mostly about the inadvisability of placing a fuel tank in the arm.



#15 Tenmantaylor

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Posted 02 September 2020 - 05:49

I remember the engine being great down the straights but the car was a dog in transient load due to engine weight in Grand Prix Legends. Sounded almost as good as the Ferrari too.

#16 blueprint2002

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Posted 03 September 2020 - 06:34

Honda’s second F1 engine was the RA273 V12 of 1966-68, the opening years of the new 3-litre formula. It was remarkable in several ways, though it never received the attention it merited. Even today, only a few basic facts are known, and to my knowledge, no drawings have been made public, nor any technical description.

To start with, the angle between the banks of cylinders was 90 degrees, not the usual 60 degrees that remains the first choice even today (for very sound technical reasons). Another unusual feature was the output drive, taken from the middle of the crankshaft (between the third and fourth cylinders of either bank) rather than from its rear end.

At that time, only three recent racing engines had featured the exhaust ports between the cylinder banks, inside the V, and inlet ports outside (Repco, BRM and Ford Indy, each possibly for rather different reasons). The Honda RA273 was also arranged that way, for reasons that are not readily apparent.

According to the “History of the Grand Prix Car 1966-85”, the wide angle was chosen because the output shaft, running below the crankshaft, caused the entire engine to be raised up. The wide angle brought the cylinder heads lower down again, lowering the CoG in consequence, so as to compensate for the rise, at least in part.

 

By a happy coincidence, a cutaway drawing of the Honda RA273 has been posted, on 1st September, in the Cutaway thread, by CVA. This is the first I have seen of it, and it answers one or two of the questions I asked in the original post.

Most important is the engine layout: the power take-off shaft runs above the crankshaft, not below it, more-or-less in the position occupied by the camshaft in the typical pushrod US V8 engine. This must be the reason for the 90-degree angle between the cylinder banks, as there would not be enough space there, with the usual 60-degree angle of most V12s.

It also appears, from what little is visible, that the crankshaft follows the usual V12 arrangement, with six cranks at 120-degree intervals. Logical, because it makes each bank effectively an in-line 6, with the excellent balance that is typical of that layout. On the other hand, the torque will be relatively uneven, given the unequal firing intervals.

Still a mystery is the reason for taking the drive from the centre of the crankshaft, rather than the end: given that other contemporary F1 V12s did not find it necessary to do the same.



#17 10kDA

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Posted 03 September 2020 - 11:15


1. But Honda had considerable experience of crankshafts driven, at very high RPM, by multiple small capacity cylinders, and had successfully overcome all the associated problems, torsional included. Is it likely, then, that the RA273 engine incorporated that experience, possibly as a precaution, rather than as the solution to an observed problem?  

 


2. So the question is: did the 90-degree angle come first, and the centre drive later, or was the centre drive the cause of the 90-degree angle?

The exhaust ports within the V are not easy to account for, because they raise the CoG, already a problem as described above. Could it be that it was done so as to give enough space on either side of the engine for substantial “wheelbarrow arms” on the monocoque, (as also favoured by BRM for the P261), space that the exhaust system would otherwise intrude upon? Or to tuck the exhaust headers behind the drivers head, hopefully to minimise aerodynamic drag?

 

1. Honda may have looked at the central power takeoff as the solution to the problem rather than a precaution. If the power takeoff is in the middle of the crank, large bearings and webs can be placed there to support the crank and stiffen the case. I wonder if it resulted in a lighter crank, allowing it to spin up faster? Or would it be a wash, driving the output shaft? In any event, Honda was all about max revs. Porsche used a central takeoff on the 917 BTW, probably due to the length of the crank, due to bore spacing required by air cooled cylinders etc.

 

2. I recall reading about more than one engine with exhausts in the center of the V - Ford for sure and I think the other was Repco - that it made engine removal easier and kept the pipes from interfering with the trailing radius rods. IIRC BRM P61/261, the model that changed from outside the V to inside the V, did not have upper radius rods so that was not a factor for them I suppose. As far as the weight, you wouldn't believe how light race pipes can be, even steel and even twelve of them plus collectors. weight of the pipes was probably about even with FI components and any other stuff engineers are tempted to stick in the space of the V for packaging reasons. 



#18 desmo

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Posted 03 September 2020 - 13:52

Center power takeoff probably was normal and better understood for the engineers who designed the engine, presuming they were also involved in the Honda multicylinder GP bikes.



#19 gruntguru

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Posted 03 September 2020 - 22:02

It also appears, from what little is visible, that the crankshaft follows the usual V12 arrangement, with six cranks at 120-degree intervals. Logical, because it makes each bank effectively an in-line 6, with the excellent balance that is typical of that layout. On the other hand, the torque will be relatively uneven, given the unequal firing intervals.

Still a mystery is the reason for taking the drive from the centre of the crankshaft, rather than the end: given that other contemporary F1 V12s did not find it necessary to do the same.

The firing intervals of 30 and 90 degrees could hardly be a problem - still far smoother torque delivery than an inline 6.

 

Taking drive from the centre of the crankshaft offers significant improvement in torsional vibration performance. Choose your mix from the following benefits - longer crankshaft life. higher rpm, lighter weight crankshaft etc. For example, although Ferrari did not find it necessary to engineer a mid crank take-off on the 312B - they did find it necessary to replace the crankshaft after every race (or was it every second race?).



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#20 Charlieman

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Posted 04 September 2020 - 10:13

According to Niki Lauda, engines for the 312T/312T2 were almost always changed between practice and race owing to bhp loss. That suggests a highly stressed engine, not necessarily crankshaft related problems. Ferrari raced the engine for many seasons so there were some 'silly' failures -- fuel metering, rev limiter -- but few public blowups.



#21 blueprint2002

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Posted 05 September 2020 - 01:42

The firing intervals of 30 and 90 degrees could hardly be a problem - still far smoother torque delivery than an inline 6.

 

Taking drive from the centre of the crankshaft offers significant improvement in torsional vibration performance. Choose your mix from the following benefits - longer crankshaft life. higher rpm, lighter weight crankshaft etc. For example, although Ferrari did not find it necessary to engineer a mid crank take-off on the 312B - they did find it necessary to replace the crankshaft after every race (or was it every second race?).

 

 

According to Niki Lauda, engines for the 312T/312T2 were almost always changed between practice and race owing to bhp loss. That suggests a highly stressed engine, not necessarily crankshaft related problems. Ferrari raced the engine for many seasons so there were some 'silly' failures -- fuel metering, rev limiter -- but few public blowups.

The Ferrari 312B/312T series of engines were flat-12s, not V12s, but in this context they differ little from V12s, in principle.

In practice, however, they differed radically from most racing engines, in that they used only four main bearings, instead of the seven that one would expect to see. In other words, there was a main bearing only after every two cranks, not after every crank. Thus, there was one at either end, one more between cranks 2 & 3, and another between cranks 4 & 5. As a result, there was a “flying” web between crankpins 1 & 2, another between 3 & 4, as well as between 5 & 6. And of course, the two crankpins on either side of each flying web were separated by 120 degrees. (Sorry for the rather long-winded description: I am unable to post a picture, so there’s no other way).

Eliminating three crank webs and three main journals resulted in a significantly shorter crankshaft, even though those that remained probably had to be somewhat longer than usual. And shorter means torsionally stiffer, given that the diameters would remain much the same. So, it is unlikely, though not impossible, that torsional vibration limited the life of those crankshafts.

Much more likely is the nature of the stresses caused by inertia and gas pressure forces on the crankshaft: the offset of the crankpins on either side of the flying web would place that part in a diabolical combination of torsion and bending, both fluctuating violently and at high frequency (~12000 RPM?), so that fatigue life might be a limitation which Ferrari learnt about early in the ten-year history of this engine.

Other limitations of the engine might also exist, but this was probably of the most fundamental significance.