26 replies to this topic

[Playtime]

Actually all the front engined F1 cars up to the mid-late fifties. Some often look almost comical with all that camber on the front wheels

Anyone know?

I mean that's got to be adding a heap of understeer to a car that only has a front anti-roll bar anyway!
Can the rear-ends have really been THAT twitchy, or is it to offset the effect of all that rear mounted fuel?

PlaYtimE

[Bladrian]

I've often wondered about the same thing myself. The Tipo 35 Bugattis look almost comical with that much positive camber on the fronts ..... what could the reasoning have been?

[Playtime]

Yeah, i mean it's such an obvious thing...yet i can't figure it.

PlaYtimE

[Mark Beckman]

"I mean that's got to be adding a heap of understeer"

Your assumptions are based on modern radial tyres I presume ?

I dont know, but first guess is the shoulder "digging in" afforded more grip.

[dustee rubba]

perhaps the cars were designed to corner in hight slip angles??

[mat1]

I am not sure those cars also had pos. camber at the outside wheel during cornering. If the king pin inclination is sfficient, the wheel will get negative camber during cornering (i.e., the outside front wheel).
A reason for pos. static camber during cornering can be ease of steering: the contact patch is in line with the king pin.
If you use negative camber, either you need power steering or you get a very awkward geometry.

Does this make sense?

mat1

[Playtime]

Hi Mat1,

Umm kinda:)

In layman's terms are you saying that there was a lot of vertical movement of the wheel during cornering and that that (depending on susp. design) allowed the wheel to 'swing up' and straighten, thereby presenting a greater contact patch during cornering?

PlaYtimE

[Bladrian]

Originally posted by Playtime
Hi Mat1,

Umm kinda:)

In layman's terms are you saying that there was a lot of vertical movement of the wheel during cornering and that that (depending on susp. design) allowed the wheel to 'swing up' and straighten, thereby presenting a greater contact patch during cornering?

PlaYtimE

Nope - the keyword here is kingpin inclination - or castor, for the more modern cars. I think what Mat1 is trying to say is that the old cars had a lot of positive castor, which would straighten the wheel up as it turned into a corner. Makes sense, kinda - but that would make the steering very heavy again. Which would explain the big steering wheels, and the close-up driving positions, I guess.
Still seems simpler to have started out with less positive camber.

[David Beard]

Originally posted by Bladrian


Nope - the keyword here is kingpin inclination - or castor, for the more modern cars.

I always understood that, strictly speaking, kingpin inclination is not the same thing as castor. Castor is what you see in side elevation, kingpin inclination is what you see in front elevation. Then you get into talk about steering offset : the difference between the point where the king pin axis and wheel centre line touch the ground. This can be positive or negative. This offset leads to a jacking effect as steering lock is applied.

[Bladrian]

Could be, David - but the last time I saw a kingpin was when I was reaming the kingpin bushes on a sixties Beetle .... it's been all balljoints and castor for me since.

[VAR1016]

Originally posted by David Beard



I always understood that, strictly speaking, kingpin inclination is not the same thing as castor. Castor is what you see in side elevation, kingpin inclination is what you see in front elevation. Then you get into talk about steering offset : the difference between the point where the king pin axis and wheel centre line touch the ground. This can be positive or negative. This offset leads to a jacking effect as steering lock is applied.

Yes KPI and castor are as you describe.

My understanding is that positive camber was in some way connnected with the cross-ply tyres used at the time - in fact there was a thread about this a while back:

http://www.atlasf1.c...&threadid=44927

PdeRL

[oldtimer]

The positive camber on the 1938/39 Mercedes W154 cars was even more pronounced than on the 50s cars. And an interesting contrast to the Auto-Union cars with their zero camber.

It would be interesting to know why

[marion5drsn]

Caster and Camber definitions.
I'm going to take a shot at this. But firstly lets get this Castor and Camber thing out of the way.
# 1, Castor (Caster) is the way the kingpin or ball join vertical axis leans backwards from the true vertical axis. It is one of the things makes a car run straight down the road. Generally a car has positive Caster for this purpose.
# 2 Camber is the way the tire/wheel leans outward at the top to help the tire wear straight. Remember these tires were not radials and they were many times just cotton ply and natural rubber. Not any steel except in the bead. If a car is to have centerpoint steering the old books are in debate about its effectiveness. With the old kingpins they had to lean the wheel outwards and the king pin inwards toward the center of the car at the top to achieve this condition.
Another thing that was not very well understood was how necessary it was to have centerpoint steering on frontwheel drive cars. If you study into the old Cord automobile and the Citroen you might find some information on this.
Mostly I believe that they just did not understand the problems to really solve the difficulties in this total problem.
One must also remember that ball joints did not become popular until around 1952 when the Lincoln adopted them for all the cars made by this division of FoMoCo. This one thing, which I believe started in Britain, had a great deal to do with modern wheel suspension. Just look a t some of the Bugattis(sp) and their camber to think that the problem was just not even partly understood. Yours, M. L. Anderson

[dbw]

ok...re the positive CAMBER seen on gp bugattis...it was widely believed in the olden days that if you followed the imaginary centerline of the kingpin down to where the tire sits on the road,the line should intersect the center of the contact patch ["centerpoint steering"]...mostly for ease of lowspeed steering....now bugatti chose to machine the kingpin holes in the axle 90 degrees to the ground....so the spindle forging was machined some 3.5 degrees positive....so the famous "tilt"of the front wheels appears from the front.it was not adjustable in any way.
now as a comparison, while the early fords [model T's]had a similar system to the bugs [without the elegant hollow axle tube-ford used an "i" section forging].. the later fords[model "A" and V-8's] kept the 90 degree angle between the stub axle and the kingpin on the spindle and angled the holes in the axle itself....thus while the wheels appeared "straight" the centerpoint steering remained in effect.[adjustment was made by bending the axle beam- "cold"!!!
now as far as CASTER is concerned,the bugs used wedges to tilt the axle in respect to the leaf springs...the more caster applied[up to 6+ degrees positive] the more stable the car is at speed..but a bitch to turn in fast corners ...thus less caster angle was used[as low as 3 degrees]to allow nimble steering [but the car tended to "hunt" or wander on long straights....]
ok..time to name drop...at monterey this year i had a long coversation with "alain de xxxxxxx" about the amount of caster on lord so and so'd type 51...and how the good mechanics changed the wedges to suit different tracks ..[by the way,4 degrees works well at laguna seca]

perhaps later we can discuss akermann steering[or the lack of it]on gp bugs
and i have a lot to rant about castor[or lack of it] on front drive miller-fords....

[Ade Maritz]

Great info, dbw. Thank you, and don't be shy. More is required .... erm, requested.

[MPea3]

Why positive front camber on older race cars? I can only think of 3 reasons, those being

1) taking into account for caster would mean positive camber in order to get the camber to zero during a corner (in other words, the outside tire would move toward upright as the steering turns the wheels into the corner)

2) an efort to control oversteer, especially when opposite lock was applied

3) something to do with the narrow tires of the time

Or am I missing something? I'd love to know.

[Roger Clark]

Here is another tread on the same subject. Also largely inconclusive, unfortunately.

http://forums.autosp...&threadid=47164

[dbw]

well i reread my post and stand by my explaination for cars with beam axles at least up to 1931ish....beyond that [ifs] i really can't speak with any authority...how about qualified conclusions??

[David Beard]

When the first motor cars appeared, I don't think there was any thought given to positive camber....they just did what they had seen before...

[Catalina Park]

Originally posted by David Beard

Looking at this photo.... The benefits are
1) You can carry a wider load.
2) You are adding side thrust to the wheel bearings which would help to stop the wheels falling off.

[David Beard]

Originally posted by Catalina Park

Looking at this photo.... The benefits are
1) You can carry a wider load.
2) You are adding side thrust to the wheel bearings which would help to stop the wheels falling off.

Very astute

[David Birchall]

As dbw points out (and he has far more experience with pre-war cars than I do) the purpose of the positive camber was to improve steering. The most important point to remember is the narrowness of the tires and the rounded tread surface-just like a bicycle really. If you lean bicycle tire to the left it will tend to go left-this of course is balanced by the opposite tire on a car but would be offset by toe-in. Modern tires having a flat tread do not like to be tilted in relation to the road since this decreases the contact patch and hence grip. On the 'beaded edge' tires used on cars in the teens and twenties, they had a pronounced roundness to the tread and could tolerate considerable positive camber which in combination with positive castor angle helped the steering.
David B

[Charles Helps]

On a wooden wheel, I imagine that the lower spokes are taking the load in compression. If you look at David's photo of the cart you will see that the lowest spoke is nearly vertical and this will minimise the bending load on the spoke. On a wire wheel I understand that the upper spokes are in tension and the wheel is hung from these upper spokes in tension rather than supported by the lower spokes in compression.

I wonder whether Ettore Bugatti's aluminium wheels (on a T35 for instance) are designed in a similar way. The lower outer spokes are taking the load in compression. In this way the combination of the positive camber (or hollow or dip in wheelwighting parlance) and the dishing of the wheel (which increases the stiffness) makes the load bearing spokes vertical.

There is an interesting article on wheelwrighting in John Seymour's The Forgotten Arts, published by the National Trust in 1984. He also records that "A dished wheel of the first century BC was dug up in Anglesey in 1947" so good tried and trusted technology.

[dbw]

i tend to think that the extreme camber/wheel dish on the horse drawn wagon shown does not have much to steering as the wagon has a fifth wheel or center pivot at the axle center...the camber on a wagon has to do with weight bearing abilities of the spokes in compression and the hub design that was most often a long tapered axle with a matching female taper in the hub...with no outer thrust surface the camber forces the hub to seat inward..with lavish use of tallow applied to the interface, a long working life was assured.

as to the bugatti wheels...the issue was not so much weight bearing in a static vertical vector as on the wagon[lets face it; the wagons top speed is vertually static] as the side load created by spindle steering and a horozontal load at the contact patch of the tire at high speed.....the early bug blade wheels had just cast flat spokes only and tended to not like "kerb bouncing"...later wheels had reinforcing flanges cast in and provided proper bracing against side loads.

the actual conceptual design of the bugatti wheel is a cloudy area with a mix of proper engineering and le patron's unique imagination.nevertheless they did/do work just fine ...

[David Beard]

Originally posted by dbw
..with lavish use of tallow applied to the interface, a long working life was assured.

I wonder how the smell of hot tallow from the wheel bearings (or at least the axle to wheel interface) compared with that of Castrol R?

[Doug Nye]

From personal experience of one to four-horsepower waggons as pictured by David may I assure you that any pong from hot wheel bearing tallow is undetectable compared to the 'exhaust' whiff from the 'engine(s)'.

DCN

[dbw]

come to think of it.. the "intake in the front and exhaust to the rear" is a rather solid paradigm in transportation...;)