Hartford Dampers 502 2+3 arm

DavidThompson · Posted: Mon Oct 14, 2019 3:39 pm Post subject: Hartford Dampers 502 2+3 arm

Am I right in thinking that the damper arm should move freely around the pivot - where the damper is fixed to the chassis and axle - or should it be fixed at this point?

John Murch · Posted: Mon Oct 14, 2019 6:48 pm Post subject:

To the best of my understanding the arms must move at both chassis and axel, otherwise they cannot operate.
http://www.andrehartfordltd.co.uk/main.htm

DavidThompson · Posted: Tue Oct 15, 2019 8:00 am Post subject:

Yes, that's what I think too. Mine will flex on the rubber bush, but do not move freely.
I called the phone number shown on the Andre Hartford web site (they seem to no longer be Andre Hartford, and I was directed to another phone number) and the person to whom I spoke seemed to think that just flexing on the rubber was correct. I find this difficult to believe.
Thanks for your reply John.

Nicholas Simons · Posted: Tue Oct 15, 2019 8:16 am Post subject:

These are friction dampers and the damping is derived from friction at the 'knee' joint, so that joint must be exercised for the damper to work. The two end joints are simple pivots which must operate freely, but within the constraints of the rubber bush torsional stiffness. Any rubber bushing at the end joints is designed to absorb high frequency radial movement and torsional deflections.

Iain Warner · Posted: Tue Oct 15, 2019 8:18 am Post subject:

Yes, I always do mine up tight so that the flexing takes place in the rubber bush.
I lock them up tight when the axle is in normal (midway) position rather than with the chassis jacked up and axle hanging down. This way the bush can flex both ways equally as the car bounces up and down.
With hartfords I find the difficult thing is to get the friction load on the discs set up correctly. I seem to be adjusting them frequently.

Iain Warner · Posted: Tue Oct 15, 2019 8:37 am Post subject:

Having just seen the posting by Nicholas I questioned whether the method I was using was correct. I have been following the procedure set out in section 2.13 of the latest technical facts. There are the type of Hartfords where there is no silentblock bush in which case these arms must rotate on the peg. Paragraphs 2.13.8 and 2.13.9 refer.
Have I been reading it correctly>?

Nicholas Simons · Posted: Tue Oct 15, 2019 10:29 am Post subject:

Iain
I would suggest that one should have the Silentbloc bushes in their undeflected torsional state when the car is sitting on its suspension. There should then be adequate rotational allowance in the rubber to go between suspension extremes of deflection. This assumes that the modern Hartford dampers have been designed correctly with respect to their end bushes. Of course, this is all irrelevant if one has old dampers without Silentbloc bushes, but these may be prone to wear and knocking. So, Iain, I think you are correct.
Hartford may have something to say about correct installation, but the forgoing is just the thoughts of an engineer who spent much of his career designing suspension systems on trains.

Iain Warner · Posted: Tue Oct 15, 2019 6:39 pm Post subject:

Thanks Nicholas, I have only once had an incidence where a silentblock bush failed when the rubber became detached from the outer sleeve.
I am not sure if the rubber is bonded to the inner and outer tubes or held securely by compression and friction.

DavidThompson · Posted: Wed Oct 16, 2019 8:45 am Post subject:

Thanks for these replies.
I suspect my car is correctly set up, if indeed the pivot relies on the torsional effect of the Silentbloc rather than turning freely.

I will now experiment with the friction settings.

Robert Craven · Posted: Thu Oct 17, 2019 10:49 am Post subject: