17 replies to this topic

[lustigson]

I just read the following on Pascal's Den Pascals' Den:
"In 1986, Gordon Murray tried another revolutionary idea with the Brabham BT55. The engine was tilted sideways to give a lower centre of gravity..."

What does that mean, "the engine was tilted sideways"? Anybody have a clue?

The picture that belongs to the text:

[scarbs]

The engine was a straight four cylinder layout, which would normally place the bore of the cylinders almost vertically (i.e. like this..I...), the revised version placed the engine at an angle from the vertical, hence the whole engine was lower (i.e. like this../...), placing the inlet plenum above the engine, rather than poking out the side of the car (like an F3 car). The engine had serious problems related to oil surge as I remember.

There was a recent piece in Racecar engineering about the cars design and devleopment

Theres little benefit, in terms of relevance to todays F1 cars, as they are a V format and cannot be rotated for any CofG benefit. However, I suppose you could say widening the V angle is akin to tilting the engine in two ways at once.

[lustigson]

I understand... almost. Were the cylinders, so to speak, bent sideways or backward compared to the lenght of the car? :

[Hellenic tifosi]

I think that tilting the engine is standard practice at rally cars...

[Doods]

I remember reading the Season Preview from Road and Track and writer describing the BT-55 as "ultra low, mean-looking." Well, we all know it had plenty of reliability problems and was, at best, a mid-field runner. Though, like many Brabhams, it was a very pretty car.

[desmo]

Originally posted by lustigson
I understand... almost. Were the cylinders, so to speak, bent sideways or backward compared to the lenght of the car? :

The engine was an inline 4 with the crankshaft parallel to the car's centerline. The engine was layed over on its side to lower the C of G and likely for aero reasons as well. Do a google search on "Brabham BT55" to see how low the engine installation was and for more information.

[Scoots]

The Merc 300SLRs had their I6s layed over too. There's nothing new under the sun

[Bladrian]

Modern F1 cars still use this trick - they lay five cylinders over to one side, and the other five over to the other side.

[jgm]

I recall that one of the main issues that had to be sorted out with this car was the gearbox since tilting the engine 72 degrees placed the crankshaft way off the centre line. A bespoke Weisman transmission was commissioned and I don't think this ever worked out quite as hoped for.

[desmo]

http://www.weismann.net/brabham.html

This web page on Weismann's site has a most interesting bit on the BT55 including a photo of the engine/transmission installation sans bodywork. I highly recommend it.

[Bladrian]

Terrific page, desmo, and very interesting. Thanks.

I found the following bit significant -

"The axles are positioned higher relative to the crank center, so under downforce loading, the axles would run pretty much straight improving cv joint life considerably."

Just what I've been telling the GPL effing arcade racers all along - you CANNOT run those cars 2.5" off the ground with the axles cocked up like that ....

[ray b]

BMW straight inline motor's are canted in the street cars
about 30* or so. the F-1 motor as were first used in turbo 1.5 form
the brabhams were over much more all most on their side ie 90* or flat
anyway none were straight up and down like a F-ford or the old 2.5 CC were used

[scarbs]

Rayb I think you might be getting confused, the early BMW Brabhams from the BT49 conversion to the flat bottom BT52 and on had essentially vertical engines i.e. the cyl head was at the top of the engine installation, with exhausts running horizontally from the left and the inlet from the right (looking forwards along the car) as in a FFord or F3 car

[Yelnats]

Good shots Irvine99. Incidently in spite of the comment leading this thread, there is mothing revolutionary or even innovative about laying an engine down for lower G/G. This was common practice for Offenhauser 4 cylinder engines in postwar Indy cars for almost twenty years.

[crono33]

pity for the alfa-romero typo

gm

Originally posted by desmo
http://www.weismann.net/brabham.html

This web page on Weismann's site has a most interesting bit on the BT55 including a photo of the engine/transmission installation sans bodywork. I highly recommend it.

[Chickenman]

I have an excellant book called " The 1000bhp Grand Prix Cars ". It go's into a lot detail about the Pro's and Con's of the lay over BMW engine.

Basically Gordon Murray and BMW were convinced by Weismann of the advantages to laying the Standard BMW M12M13 over by 72 deg. Advantages were numerous. Lower CG of course, smaller frontal area and a much cleaner airflow to the rear wing. Early tests between the BT54 design and the BT55 design revealed a 30% gain in rear wing downforce. No small feat!!

Unfortunately the project was beset with problems from the start. Delayed delivery of the gearbox, weak gearboxes, miscalculations on cooling design and inlet design led to very poor results on the track. The team at this time was suffering from internal strife and developement lagged.

One of the main issues was poor acceleration from low speeds. the BT54 pulled from 2.0 to 5.0 bar in approx 2.5 seconds. Early in the season the BT55 took three times as long. Quote: With longer intake trumpets and a revised exhaust system, that was improved, but Murray insists: " The engine never picked up properly out of corners ". Unquote.

Murray reckons the lay down engine didn't scavenge oil properly on right hand corners, the oil level in the crankcase rising to such a level that the crankshaft was thrashing about in the oil, to the detriment of power output. Quote: " The car generated 30 to 50% higher oil temperature than the BT54 all year - we never could explain that. It needed a huge amount of oil cooling. " Unquote.

If you can still find this book in print I would highly recommend it. Covers in depth developement of the " Turbo Years".

"The 1000bhp Grand Prix Cars" by Ian Bamsey ISBN 0-85429-617-4 "

Engines covered;

Alfa Romeo 890T 90 deg V8

BMW M12M13 & M12M131 Inline 4

Cosworth Ford TEC Turbo 120 deg V6

Ferrari 126 120 deg V6 and F1-87 90 deg V6

Hart 415T Inline 4

Honada RA163-E and 166-E 80 deg V6

Motor Moderni 6VTC 90 deg V6

PorscheTAG TTE PO1 80 deg V6

Renault EF4 and EF15 90 deg V6

Zakspeed Inline 4



Also recommended:

" Grand Prix Car Design & Technology in the 1980's " by Alan Henry ISBN 0-905138-53-8"

[Doug Nye]

Mention is made in this thread of the Mercedes 300SLR 'slant# engine which is referred to as a 16. It was a straight-8, and the engine was indeed canted. In Formula 1 and Formula 2 terms Colin Chapman made great play of lowering the bonnet line of his front-engined Type 16s by canting the Climax 4-cylinder FPF engine in similar style to Gordon's much latter BMW 4-cyl.

In the case of the Lotus, Colin initially canted the FPF engine over at 62-degrees to the right, while the unit was also angled with a 5.5deg offset from the chassis centreline to run the prop-shaft back from the clutch to the driver's left, alongside his seat, into an offset input of the latest-iteration Lotus 'queerbox'. The engine laydown was tried early in the 1958 season in a sports Type 15 chassis and they immediately found themselves in lubrication difficulties and power loss. Colin figured that if Offenhauser's big 4-cyl could work adequately in the 'lay-down' roadsters at Indy and Mercedes had dominated with a slant engine why shouldn't his succeed? However, for Le Mans the works Lotus 15 sports were re-worked with the FPF engines canted more modestly at 17degs to the left, which permitted straight induction pipes betwen carburettor and inlet ports. Results were now very good.

For the single-seater Lotus Type 16s' debut at the Reims weekend - which included both Formula 2 and Formula 1 races - one 16 was equipped with a 1500cc F2 unit remounted at 17degs to the left, angled across the frame right-front to left-rear at 6.5degs offset, while the F1 car ran unaltered with the 62-deg 'lay down' engine. By the time of the following British GP one Type 16 had its FPF engine mounted 'upright' and by the time of the German GP the team's F2 Type 16 had its FPF canted at 17degs to the left with a 10.5deg rake across the centreline, and a kinked propeller shaft with central UJ to move the gearbox into proper alignment with the driveshafts - whereas previously the gearbox had been mounted at 4degs to the transverse.

Just a different angle on the subject, you understand...

DCN

[desmo]

Thanks Doug, interesting stuff! Seldom anything new under the sun is there?