Telescopic damper mounting angle

[littleblackflash]

But they probably don't replace their damping fluid with engine oil to stop them bottoming out on bumpy country roads.
Also, F1 is a strictly 'beard' and 'ale' free environment afaik, so it's not entirely allied with the average Minor owner.

I believe a lot of 'modern' French cars still use torsion bars.

humm, I worked in F1 about 8years ago designing dampers and I have a moggy but no beard. I don't think there is a connection.

Anyway, F1 cars only use dampers about 5% of each lap. As soon as the car is moving fairly fast, the downforce closes the dampers and then it's down to just the tyres. I think my moggy only works 5% of the time.

Bmceccose actually wrote a lot of sence (unlike some forums). Which is so nice to see.

[glaughton]

I've read many times that mounting telescopic shocks at an angle reduces the overall dampening effect because the shock's mechanisms travel less of a distance than the suspension system. Or as bmecosse puts it: "If mounted at an angle - the damper internals doesn't move as much as the suspension moves, and so it really can't work as well as it would if mounted so that it moved full travel with the suspension."

Indeed this seems to be the conventional wisdom. But geometry/trigonometry surely dictates that an angle-mounted shock's internals will actually travel further than a vertically-mounted shock and therefore probably give a firmer ride. If you draw a right-angled triangle to compare a shock absorber mounted at a 45 degree angle and one mounted vertically - for every 3 inches of suspension movement the vertically-mounted shock internals travels exactly 3 inches. The 45 degree angled shock's internals travel further - just under 4.25 inches in fact.

This is not to say that angled is the way to go but given a correctly-engineered shock it could explain why several cars - Citroen etc - have them.

[IslipMinor]

I don't think the damper geometry behaves in the way the post above describes? It is as Roy described, and the table below shows how a typical telescopic damper that starts off around 12" long at 45° to the horizontal, shortens progressively less and less as the axle moves upwards. At 2" upward axle travel the damper has shortened by 1.32" (66%) and is now at 37°, and at 4" axle travel the damper has shortened by just 2.40" (60%) and is at 28°.
[frame][/frame]
During the refurishment I had a complete Koni kit that I had bought earlier, so wanted to fit that. At the rear I had little option but to fit them at an angle (not as much as the kit is originally designed though), as there is not enough room between the inner edge of the rear tyres and the wheel arch, and I did not want to intrude into the boot space or spare wheel space that a turretted option at the time would have meant (great vertical location though!).

So they are at an angle, up to a fabricated cross-member; I agree not ideal, but set on full soft and in conjunction with slightly softer 7-leaf springs, do the 'damping' job very well.

At the front I moved the lower mounting point as far outboard as possible to get the maximum damper movement relative to suspension, and also had Koni uprate the 2 front dampers' bump valve setting by 30%. Set on full hard, they control the front end extremely well, never harsh, but very very firm.

If anyone is in the Oxford area, please drop in to see/feel for yourself!!

[bmcecosse]

Excellent explanation there Richard. Back to skool Mr glaughton for another round of O level geometry...

[glaughton]

You are right Islipminor - thank you for the info - in future I will just read the tables rather than try and work it out myself!

Are your Koni dampers mounted on the bottom axle plate? I currently have the rear Spax kit mounted on that plate but they are at about 45 degrees. I also have 5-leaf springs - you say your 7-leaf suspension is 'slightly softer'?? I find the Spax adjustment useless and the ride is pretty harsh even on softest setting. However, when the car is fully loaded with luggage (and with a full tank of petrol!), it feels less harsh and more stable.

At the front I've still got decades-old Charlie Ware Series 3 telescopic shocks - going to upgrade them but unfortunately don't think I can simply install different shocks on the existing mounts.

[IslipMinor]

At the rear I have turned the bottom leaf of the 7-leaf spring upside down and put on the top of the remaining 6 leaves, so that it works against them and softens/lowers all at the same time. Did it 40+ years ago when we got the 5.5"x13" wide steel wheels!

Interestingly I have fitted Spax adjustable a couple of times in the past to 'moderns' and both times found the result harsh, even on full soft.

Yes, the rear Koni's are mounted on to the bottom spring plate, but I have not measured the angle of them - I would think it is around the 45° mark as well.

[bmcecosse]

Just drain and refill the front dampers with sae 40 or 50 oil. You will be amazed at the difference.... And no wonder the rear feels 'harsh' - dampers at 45 degrees will be forcing the axle sideways on bump.... madness!!

[IslipMinor]

dampers at 45 degrees will be forcing the axle sideways on bump

Oh come on Roy that is complete nonsense. How on earth can the damper angle 'force the axle sideways'? It is not a spring or a suspension link - at most it can offer a very brief transient resistance to movement. In any case there are two of them at the equal and opposing angles, so any 'sideways forces' will cancel each other out!

[bmcecosse]

IF it's doing any worthwhile 'damping' then in one wheel bump at 45 degrees it WILL be pushing the axle sideways - and very possibly jamming it in the shackles/bushes. The other damper may not move significantly - so cannot hope to cancel the force anyway as it will be in 'droop' mode rather than 'bump'. If both wheels are in 'bump' - then the two will wedge against each other....

[glaughton]

With the Spax kit the shocks go from the axle plate upwards at an angle directly towards the rear of the car so there is no sideways / lateral pressure on the axle at all regardless of whether one wheel is in bump mode and the other in droop ...

[bmcecosse]

Shocks??? At least these dampers won't push the axle sideways - but still not efficient to run tele dampers at any significant angle away from vertical.

[IslipMinor]

Can we some common sense into this please? Telescopic dampers at an angle are not 'as efficient' as vertical, but they still work!

The problem is that as the angle changes with suspension movement, the efficiency changes as well. Very significant on a pure race car or F1, but on a Minor, even a well sorted one, is it a 'real' problem? I don't think so.

[bmcecosse]

It isn't -at a slight angle. But 45 degrees???? Come on !!!

[IslipMinor]

45° = 70% from the previous table - they work.

[glaughton]

I may well buy some vertical turreted dampers if and when I can afford it - no doubt they are more efficient. In the meantime I'm going to make do with the mountings in their current positions and having just looked under the car, they are angled at less than 45 degrees - see attached image. They do work![frame][/frame]

[bmcecosse]

I'm sure they work - just not as well as they could. But that angle doesn't look too bad - and not sideways !

[IslipMinor]

But that angle doesn't look too bad - and not sideways

Ah, but the angle they are set at will introduce uncontrollable bump steer by 'forcing the axle' backward and forwards if the previous 'logic' is followed (no I do not subscribe to it!!).

[lambrettalad]

I believe it's the angle of the dangle that counts

[brucek]

Take a chill pill guys it's just a damper I don't think Adrian Newey will be too worried either

[bmcecosse]

Fortunately -it's angled to the rear - so any stray forces will be forward into the fixed shackle mount. Can't say it is ideal - but not as bad as 'sideways' where the Minor axle is very poorly located. A Panhard rod would be useful!