Author Topic: Berkeley paradox  (Read 8755 times)

Big Al

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Re: Berkeley paradox
« Reply #15 on: May 20, 2016, 02:40:30 PM »
U/J is a universal joint, meaning a cruciform running in paired bearings, like a Hardy Spicer joint, as opposed to a C/V, or constant velocity, joint. The issue is that on a Berk these drive shaft are off offset lengths. The shorter the length, given the steering lock, the more the two bearings can wind up, especially if they are not mounted opposing each other on a shared shaft. The play is designed to be taken out of the system by a sliding spline on the drive shaft. All well and dandy when used in something deflecting like a drive shaft from engine to rear axle. The technology is over its limit on the Berk front suspension, really.
Many small cars had to deal with this problem on rear suspensions, and often a cushdrive coupling was included. Likewise on front wheel drive, which test the system further than most rear drives, the joint play take up is more important. Saab and such had rubber joints. Even the Mini had rubberised cruciform initially, before finally switching to CV joints after experiments with Hardy Spicer to take the excess power demands of the Cooper S.

Not content with that there is a tendency for the drive shaft nut to undo. This has ended in a wheel disappearing on private tour down the road on more than a few Berks over the years. All rather embarrassing. Its easy to see why Berks get modified, as the cheap production is great, in that it uses basic parts bin resources, but the package is not as good as the sports car image suggests. Hence a change of engine, front drive, disc brakes, or imp stuff, steering rack, move of fuel tank to rear with pump and a stiffen up of the body. A production car turned into a kit car, really. The ultimate, and normally no way back mod, was to dump a caste iron 4 pot Mini engine and subframe into the front, with some bonnet blimps, or extra chassis to raise the car. By this time much of the Berk is actually residing in the bin. But its part of Berk history whether you like them, or not.
« Last Edit: May 20, 2016, 02:44:20 PM by Big Al »
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steven mandell

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Re: Berkeley paradox
« Reply #16 on: May 24, 2016, 04:25:22 PM »
Thanks AL. but please further define "wind up".
Is it simply the effective length change to the car's front track imposed by the degree of road wheel deflection causing an increase of angle of the drive shafts away from being parallel with the road surface?
If so, I suppose that king pin axis inclination would also compound this length change by virtue of its effect of raising and lowering the front end of the car whilst turning the steering wheel from lock to opposing lock.
I am a bit confused by the implication of "winding up" here.  Does this refer to  a drive shaft wanting to flail increasingly out of parallel to the road surface when accelerating, or any other conditions?
Your reference to rubber driveline bits included for isolation of driveline vibration leaves me doubly confounded, as I am aware of the use of rubber doughnuts in the rear suspensions of Lotus Elans, and possibly Triumph Spitfires.   
These can tend to  to wind up and release sequentially in a pulsatile manner, giving a sort of bunny hop character to less precisely modulated balancing acts betwixt clutch and gas pedal during more aggressive attempts at acceleration.   So "winding up" may, or may not have an additional implication here.

in any case, does the Berkeley tend to loose its wheel more often on the shorter drive shaft side due to its greater functional length change o this  side of the car imposing greater strain on the front hub retaining nut?
Any other good fixes for all of this?   
« Last Edit: May 24, 2016, 04:30:39 PM by steven mandell »

AndyL

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Re: Berkeley paradox
« Reply #17 on: May 24, 2016, 06:18:02 PM »
U/J's or cardan joints as they are known are not constant velocity joint, in other words they accelerate and decelerate when run out of true.

This puts a lot of strain on the joint and surrounding components, and also creates vibration. CV's don't have the same problem, which is why they have been universally adopted by the automotive industry, but back in the '50's they were still a fairly fresh idea.
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