Forces on anti-roll bar link-rod ball joints

[zedrider]

Can anybody tell me what sort of magnitude of forces are experienced by the ball joints at either end of an anti-roll bar link rod, as used on a typical European saloon car or small MPV?
Also, are any of these ball joints metal-to-metal or do they all have a plastic bearing cup?

Many thanks,
Zedrider

 

[GregLocock]

Last thing first, I think they'll have a plastic interlayer.

the force will be about 1000-5000 N max

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[zedrider]

Thanks Greg

I had expected the plastic cup to be standard, all the examples I've seen so far are like this.

I assume that link rods are only intended to take force aligned with the actual rod itself. (I suppose this would mean vertical forces only in most installations.)

What would you advise regarding application of force at right angle to both the longitudinal axis of the rod and to the longitudinal axis of either fixing pin?
I am currently persuaded this is a 'bad idea'(!), on the grounds that the connection of the rod to the retaining ring is a fairly weak weld.

I am looking for a suitable high angularity ball joint, with very low friction, for use in a hub-centre-steering motorcycle front hub. It will be subjected to braking and steering forces, but will not hve to take suspension loads, although it probably should be able to take jarring from road surface irregularities. The joint must also be very compact.
I thought I would ask the Auto suspension list since the MC engineering list still seems set on using telescopic front forks.

Thanks again,
Zedrider

 

[CoryPad]

Zedrider,

You have been advised wisely that most ball joints have low force resistance in the axial, with respect to the fastened joint, direction.

I have been interested in a device similar to you, and I have seen one produced by the Dynalink division of Maclean Vehicle Systems. I believe it was for a European automobile. You can learn more about this company at:

http://www.mfmvs.com/

Regards,

Cory

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[mloew]

More information on the Dynalink^™ can be found on this link

Best regards,

Matthew Ian Loew


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[GregLocock]

You can also get links with the thread axial rather than at 90 degrees to the main line of the link, which I think may be what Z is on about. It's not preferred but they are durable.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[zedrider]

I was trying to describe almost exactly what Matthew has posted, but only using one end of course.
Since this type of ball joint is not really suitable for my purposes, can anyone recommend a source of high articularity, metal-to-metal ball joints that can take radial and axial forces and have compact dimensions?

Thanks,
ZR

 

[GregLocock]

Can you be a bit more specific with the numbers, and what is specifically wrong with the Dynalink approach?


Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[zedrider]

The mass of the vehicle is likely to be about 300kg gross (including rider). I reckon 1.5g is about the greatest decelleration the front end can ever see under heaviest braking conditions. With a factor of safety of 2, I make that approximately 9kN through the ball joint in the front hub.

I don't want to use a joint with a plastic cup because the joint needs to have no preload (otherwise it will interfere with steering input and feedback) and a plastic cup cannot safely be modified to remove preload. (An established UK design of hub-centre-steering used the lower ball joint from an Austin Mini. The preload is removed by compressing the joint axially in a bench vice.)

For the first prototype I want to avoid machining a new hub and hope to use an existing drum-brake type motorcycle hub with the brakes shoes removed. The ball joint would be fitted in the anular space vacated by the brake shoes, somewhere below the axle line, in whichever orientation is most suitable for the application.

I hope this makes the situation a bit clearer.

Regards,
ZR