Can anyone explain why pre-war cars had so much positive camber on their front wheels?
It seems to me it must've seriously compromised their handling with the front, outside tyre being on its edge on corners.
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>> Can anyone explain why pre-war cars had so much positive camber on their front wheels?
How much did they have?
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At a guess, it acted along with the castor angle to give it some straight line stability. It was probably the only way they knew at the time to provide self-centring.
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Here are some examples of pre-war Austins. tinyurl.com/97dcem8
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>> Here are some examples of pre-war Austins. tinyurl.com/97dcem8
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It's not clear from the diagrams whether the camber angle is the angle from vertical or the angle from the swivel pin.
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>> >> Here are some examples of pre-war Austins. tinyurl.com/97dcem8
>> >>
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>> It's not clear from the diagrams whether the camber angle is the angle from vertical
>> or the angle from the swivel pin.
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tinyurl.com/9damd8a
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>> > angle from
>> vertical
>> >> or the angle from the swivel pin.
>> >>
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>> tinyurl.com/9damd8a
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Thanks L'Es - vertical it is.
So with the king-pin normally angled outwards at the bottom, ie so that the swivel axis points towards the centre of the tyre's contact with the ground, there would be no tension on the track rod. If the king-pin was vertical obviously the wheel would try to steer outwards, like a mechano model or pedal car if the track rod comes off.
In the centre position the steering would be basically neutral, leaving just the caster angle to give the self-centring effect.
But what happens when the steering turns? There must be a complicated interplay between camber angle and king-pin inclination? Sliding Pillar or Number Cruncher ?
I know this is certainly the case with my Ferguson tractor. Up to a point the steering self-centres, but at a certain tightness of turn it suddenly switches to oversteer, and viciously swings over to full lock.
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Yes is the short answer!
King pin inclination of itself is a major contributor to self aligning torque. Whenever you steer the wheel away from the staight ahead position, the king pin inclination means that the front of the car is lifted up slightly.
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Too scientific a subject for me!
But, a stub axle assembly does not have the holes for the king pin quite at 90 degrees to the axle line. So as it turns, the angle of the wheel to the road changes. Generally speaking, the inside wheel adopts a greater positive camber, and the outer wheel nearer to zero or even negative camber.
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One reason is lighter steering. However a smaller degree of positive camber was common at least until the 70's, may be on more recent cars too (I don't look so hard at modern cars - not really interested!).
Would not be surprised if there was also a measure of duff information as front wheel brakes were thought to be dangerous in the early days of motoring and most cars only had rear wheel brakes - sometimes supplanted by a transmission brake. Front wheel brakes only came in in the 1920's, standard I think from 1926 for Morgans.
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>> Would not be surprised if there was also a measure of duff information as front
>> wheel brakes were thought to be dangerous in the early days of motoring
They certainly were on the aforementioned Austin 7.
The brakes are cable operated. A cross shaft runs through the A-frame chassis in bushes with the brake pedal welded to it. The wire cables are attached to this at one end and the brakes at the other. Pushing the pedal rotates the cross shaft, winding in the wires and applying the brakes.
The slight snag is that the front axle is mounted on the "nose" of the A-frame and held in position by two trailing tie rods going back to further down the side chassis rails. The mounts at all three points are via rubber bushes to provide isolation.
The net effect of all this is that if the brakes are applied with any vigour, the axle moves rearwards on its rubber mounts, reducing the tension in the cables and releasing the brakes. For added fun, if there is any wear at all in the mounting "cups" for the front axle, the axle can twist on its mountings, biasing the braking effect to one side or the other.
There was an aftermarket modification kit for the 7 that converted the front brakes to bowden cable operation to address these problems. There's a rusty set of these awaiting restoration to go onto my father's Type 65 at the moment.
Just to add insult to injury, the rears aren't that wonderful either. As the pedal is mounted on the right hand side of the cross shaft, while the force at the pedal is transmitted pretty much directly to the cable of the right-hand rear, the force applied to the left-hand one at the other end is subject to the vagaries of twisting in the cross shaft.
The whole arrangement combines to provide some very "interesting" handling effects under braking, as you're never quite sure which wheel will lock first.
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>>It seems to me it must've seriously compromised their handling
Not really - stupid wide tyres weren't in popular use then, so, the maximum side force the tyre produced wasn't as sensitive to camber as a modern tyre.
Bringing the centre of the contact patch inboard a bit reduced the bending moment on the stub axle, reduced the loads on the outer wheel bearing, allowing it to be made smaller, and reduced the scrub radius, which, at the time was thought to be a good thing to do to reduce steering torque.
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Front end positive camber on early cars - L'escargot
