17 replies to this topic

[Bob21]

I am trying to understand what type of setup a 1937 Mercedes Benz would have had in race trim and how that would have compared to the racecars of the 50's and 60's .We all know about the high horsepower and skinny tires but then how were these cars raced at Grands Prix ? Did they do interesting things with toe or camber and were the springs or torsion bars considered soft or hard ? Was there an anti-roll bar by any other name?

I've read that Herr Uhlenhaut had a profound effect on developing W 125 from the W 25. It was said at another site ( Die Siberpfeile--www.ddavid.com/formula/silver.htm) that the "suspension was completely redesigned with the idea of providing softer front suspension than at the rear while keeping the driving wheels upright and at right angles to the road". I'd like to know if it's possible to find greater detail . Thanks, Bob

[Leif Snellman]

Bob,

Send me your e-mail address and I'll send over some material.

[Vitesse2]

Bob (and Leif, come to that) I recently unearthed my copy of Denis Jenkinson's monograph on the W125: I can scan the relevant section if required.

[gmw]

By far the best description of Rudolf Uhlenhaut's changes to the 1936 W25 that then became the 1937 W125 is the Karl Ludvigsen's "Quicksilver Century". On page 156 is the only photograph I have ever seen of the 1936 De Dion rear suspension. At the time very few people outside of Daimler Benz wer4e aware that the W25C had a different rear susbension.

Jenkinson adds very little to previously published information on the W125 suspension, and may not have been aware the the 1936 W25 did have a De Dion rear suspension.

The best pictures of the W125 front and rear suspensions is in Cameron Earl's "Investigation into the Developmwnt of German Grand PRIX Racing Cars Between 1934 and 1939". Earl includes an assembly drawing of the W25 bA front suspension directly from the Daimler Benz Archives and front suspension assembly and de Dion layout for the W165, which is very similiar the the W125 abd W154.

GMW

[Hans Etzrodt]

Originally posted by gmw
... Earl includes an assembly drawing of the W25 bA front suspension directly from the Daimler Benz Archives and front suspension assembly and de Dion layout for the W165, which is very similiar the the W125 abd W154...

This sounds like someone here knows their stuff. But I am really lost.
I would like to know what a W25 bA is and who coined this chassis description. The same applies to a W125 abd W154, which I don't understand what kind of animal this could be. Please explain to someone who is hungry to learn. And what is the origin or source of these numbers?

[Jonas]

Originally posted by Hans Etzrodt
W125 abd W154, which I don't understand what kind of animal this could be.

W125 AND W154, perhaps

By the way, doesn't Pomeroy show some of these details in his book? I don't have mine at hand so I can't confirm..

[Vitesse2]

Originally posted by Jonas

W125 AND W154, perhaps

By the way, doesn't Pomeroy show some of these details in his book? I don't have mine at hand so I can't confirm..

There's a sketch of both suspensions on p225 - very finely detailed and difficult to scan, I'd think - and an exploded drawing of the de Dion tube on p227. Volume 1, of course.

[gmw]

W125 AND W154 is what I intended to say. Forgive the error.

W25 bA is the callout on the factory drawing. The W25A was the original 1934 car. I believe that the '35 car was W25B and the short wheelbase 1936 car was W25C, although I am not certain. It is a bit confusing because the M25A, M25B and M25C were the engines used from 1934 to '36, but these were not changes for each year, but there were changes during the year. The M125 engine was also a straight eight like the M25 series, but was a new engine for 1937.

Pomeroy's drawings are based on the factory drawings that Earl published. In the original 1946 single volume of Pomeroy they are on pages 216 and 218.

Going back to Bob21's original question that started this thread, the W125 was a direct parent of all grand prix cars before Colin Chapman. These cars mostly used wishbone front suspension with coil springs and a de Dion rear. Ferrari introduced the two parallel trailing arms on each side the took the tensional loads out of the de Dion tube that were in the Mercedes design with the single trailing arm on each side, ( The Mercedes de Dion tube was split in the center to let the two ends rotate slightly when car rolled.)

These cars were built with essentially one setup. There was no changing of the set up to match the driver or the track, The driver adapted to the car as the designer drew it. Caster, camber and toe were adjustable like any cay, but were adjusted to the design specs and left there. Colin Chapman was the first to make the suspension adjustable and to adjust it to suit the track and driver. I think that Chapman may also have been the first to put an anti-roll bar on a GP car. The anti-roll bar was an integral part of the front suspension on the original Lotus F2 car, the Mark 12 and the series II Lotus X1.

As for how the drivers drove these cars on the narrow tires and high power, they drove them very carefully and with much skill.

[oldtimer]

The 1939 W154 had a driver controlled adjustment for the rear suspension, presumably to deal with the large weight change (about 600lb) as fuel was consumed.

[Jonas]

Originally posted by oldtimer
The 1939 W154 had a driver controlled adjustment for the rear suspension, presumably to deal with the large weight change (about 600lb) as fuel was consumed.

Were the rear springs adjustable in some way, or was it just the shock absorbers?
I know other cars had adjustable shock absorbers before the W125, for instance the AR 8C 2300..

[gmw]

The W154 did have adjuatable rear ahocks, to control "chatter". they were controled by a lever on the driver's left. The W154 was also the first racing Mercedes to have only hydralic shocks. The W125 had both friction and hydraulic shocks front and rear, but they were not driver adjustable.

GMW

[Jonas]

I remember that Neubauer told a story in his book "Männer, Frauen und Motoren" about the drivers being sceptical towards the new hydraulic shock absorbers and that they insisted on at least having these in parallel with the old friction things. The story goes on with Uhlenhaut greasing up the friction dampers so that in practise only the hydraulic dampers were used. When the drivers found this configuration not being any worse at all, they were less reluctant to convert to hydraulic dampers alone. This must have been a development tested on the W125 then?

[Bob21]

Thanks very much all of you. I know more than I did a few days ago (uh oh). Vitesse2, just this afternoon unearthed my copy of DSJ as well. Let's see what Leif says he wants. Leif also reminded me of the Karl Ludvigsen book on Mercedes. Lots of testing stuff in there as R. Uhlenhaut tries to turn the 1936 car into the winning W125. A reference also that the W125 had front springs of 175 Lbs and rears of 207 in race trim. Bob

[GIGLEUX]

Some drawings of the W125 suspensions. Above, front suspension.


Rear suspension.


View of the rear end of the car.


Here the factory drawings published in L.Pomeroy's book "The Grand Prix Car",page 225.

[oldtimer]

Doesn't the photograph show the rear of a W154? Isn't that an off-set, angled prop-shaft?

[GIGLEUX]

Think you are right. Sorry for this erroneous caption!

[Jonas]

Seeing the sketch of the front suspension layout reminds me of a thing I know I've been thinking of before but without finding an answer:

How come the upper and lower triangular arms are mounted in the chassis in a way that the whole assembly can be turned relative to the chassis around the point marked with "1" in the sketch below? And what is the point in fixing "2", apart from stopping the entire assembly to turn due to mounting "1"?

Actually it is easy to understand why you would need fixing "2" in this layout. Under braking there would be a considerable torque around fixing "1" that needs to be counterbalanced (couldn't think of a better word..). But I don't see the point in making the suspension layout in this way in the first place.

Was this configuration made to facilitate some kind of adjustments? And what could these adjustments then be?

Looking forward to hear a good explanation. Because I'm sure there IS one. The MB people wouldn't do this just for the fun of it..

[Leif Snellman]

Originally posted by Jonas
Under braking there would be a considerable torque around fixing "1" that needs to be counterbalanced (couldn't think of a better word..). [/IMG]

On the SSK the kickback from the wheels had been such that it once even had dislocated the shoulder of Christian Werner. The W25 suspension had been built from experience from rebuilding the SSK suspension, so that a bit of movement was allowed. (On the W25 the coil spring was horisontal positioned inside the tube approximately between 1 and 2 on the picture.) However, in 1936 Uhlenhaut found that "the toe-in caused by the steering-linkage geometry in relation to the suspension movement was so great that the influence of the various spring stiffness, the shock absorver settings and altered king-pin seems to be of only secondary significance."

So the W125 suspension was a developement of the W25 suspension where just a little bit of freedom of movement would still be retained.