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Alfa Romeo "Flat" 12 engines?


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#1 f1steveuk

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Posted 20 September 2014 - 13:29

It's argument settling time again! Someone put me out of my misery. I was discussing the Brabahm team, as it was around the time of Martini sponsorship, and the BT45 was mentioned, along with the words, " which had a flat 12 "boxer" engine".

 

Now I am sure I read something once that said that tecnically it wasn't a flat 12, but a V12 (obviously of a very obtuse angle!), or that it wasn't technically a 'boxer'.

 

Has somebody else seen, read or have knowledge of this, or is my mind playing tricks. Normally I'd run off to my library, but I am now where near home, so any help in stopping a melt down would be gratefully recieved!!



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#2 Michael Ferner

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Posted 20 September 2014 - 14:25

It was a flat 12, but not a boxer. Often confused, but a 180° V engine is only a boxer if opposed pistons run "against" each other, which they rarely do. Hence, most flat engines are not boxers, even if less technically inclined people call them such.

#3 RogerFrench

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Posted 20 September 2014 - 14:53

Hence, most flat engines are not boxers, even if less technically inclined people call them such.


Like Ferrari, for example!

#4 jcbc3

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Posted 20 September 2014 - 19:38

It was a flat 12, but not a boxer. Often confused, but a 180° V engine is only a boxer if opposed pistons run "against" each other, which they rarely do. Hence, most flat engines are not boxers, even if less technically inclined people call them such.


I lit this fire in the TNF here: http://forums.autosp...ngine-concepts/

#5 Rudernst

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Posted 20 September 2014 - 20:45

"flat" 12s never are true boxers

they are usually 180 dregree Vs

 

reasons are quite simple

 

 - in a true boxer you have twice as many crankpins and webs and a much much longer crank whith all the ugly problems that stem from that

 - in a true boxer You have more pumping losses than in a 180 deg V

aaaaand

 - You dont need to go to the trouble of going true boxer as each 6 cylinder bank is fully balanced in 1st and 2nd order anyway

 

you dont gain anything in a 12 cyl boxer over a 180 deg V apart from problems

 

Rudolf  



#6 Roger Clark

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Posted 20 September 2014 - 22:58

Was the H16 BRM, in its later development with 8-throw crankshafts, a double boxer?



#7 Rudernst

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Posted 21 September 2014 - 09:50

good question

 

buut

if there are 8 throws for 16 rods, then it cant be a boxer

then the H16 consists of two 180 degree V8s on top of each other.

my guess, without having looked it it up for the reasons given below is

that the cranks were 180 degree flat cranks similar to a 4 cylinder

and two rods per crankpin

 

aaaand

again, it does not need to be a boxer

because of the 2 crank construction, each pair 2 cylinders LYING ON TOP OF EACH OTHER can be fully balanced in the first order by the crank webs because the verticals in the 2 webs cancel each other out.

 

In therory You can have ALL 16 PISTONS moving together in the same direction at the same time and still have a fully balaced engine in the first order.

As surprising as this sounds.

but in practice for reasons connected with firing order and forces of the second order, it must have been 180 degree cranks

 

The Brough Superior Golden and the Word Championship winning Kawasaki 2-stroke 2 cylinder bikes exploited this concept of paired cranks balancing primary forces.

in the Brough all 4 pistons moved in the same direction at the same time

 

R.E.



#8 f1steveuk

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Posted 21 September 2014 - 12:35

Thank you all, I fell slightly vindicated !!