Vintage Minor Register

I am considering to fit new Hartford shock absorbers under my Minor SV roadster 1933. The 502 series with one blade into two blades is recommended for light cars like this. But what about the length of the blades? The front springs are much shorter and stiffer than the rear springs therefore it seems wrong to fit the same damper in front as in the rear. I would guess that the front dampers require shorter arms than the rear dampers do. But how long is that? Is there expertise or experience in this forum to advise me in this problem?

Jeroen,

Mhe M Type MG with the same chassis was fitted with the same 502M's front and rear as standard. And the M had flattened front springs fitted as standard. But you raise an interesting point - it would seem to make sense to have slightly longer arms on the rear units.

Either way, you'll find Hartfords far better than the original Morris single-acting shock absorbers and you'll have a suspension that actually works!

Not so sure Jeroen is right on this one. I read recently that modern dampers are designed to work more on the rebound than when the spring is being deflected, in a similar way to the Minor single acting type - although I don't think the Minor ones are completely single acting as there appears to be some friction both ways. ( I would like to try some just to find out if the ride is better, if anyone has a pair they don't need.)
For both road holding and comfort I found the pear shaped hydraulic ones were the best. Much better than Hartfords anyway.

Ian

Recently I inquired in this forum which arm length I should choose when ordering Hartford shockabsorbers for my Morris Minor SV. I received no definite answer so I posed the same question to the dealer: "Holden, Vintage and Classic Motoring website" from whom I received no answer at all. I then figured it out for myself but I would highly appreciate this forums criticism on my arguments before I actually order the parts.
I start from the following observations on the geometry of the Morris suspension:
1) The distance between the upper- and lower mounting holes for the shock absorbers of my Morris is approximately eight inch for the front dampers.
2) The rubber stops on the front axle of my Morris allow three inches of upward deviation of the axle.
Assuming the allowable downward deviation to be of the same order as the upward deviation, the front Hartford must be able to span all distances between 8 - 3 = 5" and 8 + 3 = 11". When the upper- and lower arm have the same length this length must amount to at least (8 + 3)/2 = 5 1/2 inch .
To prevent the damper from folding in the wrong direction on its return stroke I do not want to stretch the Hartford to an extreme 180 degrees, therefore I choose an arm length one size larger than 51/2 inch and that is 6".
Why not choose arms more than one size larger, for instance seven inch or eight"? Certainly not! Because that would result in an undesirable and needless decrease of efficiency in the damping. In the Hartford, the arms translate a vertical linear displacement of the roadwheel to a rotational displacement of the friction discs. And a longer arm results in a smaller rotation angle for the same displacement of the wheel.
Conclusion: I shall order one pair of Hartfords 502 S with equal six inch arms for the front axle and, on similar arguments, another pair of the same with seven inch arms for the rear.

Jeroen,

Your argument makes perfect sense to me! I will measure the original Hartfords on my McEvoy Minor this evening and report back in the morning.

Ian

Jeroen,

The Hartfords on the front of my McEvoy have 7" arms. The rears are missing, but I'm pretty sure they would have been the same - even though they span a greater depth than the fronts between chassis and spring. Hope this helps.

Ian

Evening Jeroen/Ian - have just measured my 1933 SV Dampers {the ones with wooden (Pear?) friction discs} - Front = 6.5" arms and Rear = 6.75".

John

Hello Ian,
Your reply helped me to make the decision: Yes, I'll order the Hartfords now. I needed just that little push in my back. After all it is an investment of about 400GBP. Thank you for the interest you showed.
Jeroen

Hello John,
I'm quite happy with your observations. They support my ideas. I restricted the precision of my calculations to 1/2 inch because the present Hartfords are not available in 1/4 inch sizes as far as I know. Thank you for your help.
Jeroen
PS. Pear wood is used for making flutes because it is very agreeable in the lathe. For the same reason it could be used for friction discs.

Now I have learned something. Pear wood! Our property was originally built by a family pioneers who settled in the Cascades and established a pear farm. We still have some of the original and ancient pear trees around the paddocks. So now I know where I'm going to get my friction disks for my Hartfords!

I have checked the Hartfords on my Jensen and they are 6.5" front and 8.5" rear centre of mounting pivot to centre of adjusting nut measured quickly with a tape measure on the car - not that easy.

Did Jensens fit Hartfords as original? They must have lengthened the steering column and I think they fitted a Brooklands steering wheel. And they would have moved the battery box forward. And of course, your car MAY be a McEvoy!

Anyway, I'm missing the shock absorbers on the rear of mine, so I need a pear if anyone has a couple spare!