Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Plus4 GDI and Spax dampers?

Thanks again for all the nice comments re the bump thingies and thanks René for your message.

Unfortunately, these aren’t the magic fix for all the nasty bangs and crashes that can happen at the rear of a trad. If the springs are in good condition, they can help prevent some of the infamous Morgan bottoming and add a bit of progressive stiffness to the suspension at the same time. However, they can do nothing for a car where the suspension is topping out under extension and producing that occasional disconcerting jolt or bang that some cars may have.

The tricky bit however is differentiating between the two types of events, bottoming and topping. In the heat of the moment when the car hits a bad spot on the road, the suspension reacts so quickly that you can’t easily tell if the issues is at the top or the bottom of the suspension travel, or even both. Fortunately topping out is easy to identify and deal with as it mostly because one or both dampers are too short. To establish this just whip out the top damper bolts, jack the car on the rear cross member to let the axle sit on the rubber drop stops and then try and re insert the top fixing bolts. If the damper’s top fixings won’t reach up to the mounting eye’s and you can’t easily insert the bolts, then most probably the dampers are too short and have been limiting the suspension. Unfortunately, this is not uncommon. Not only can it spoil your ride but will have been stressing all sorts of stuff that shouldn’t have been stressed

So, if you have some bad behaviour at the rear with no obvious reason, dare I suggest that this is the first check and particularly when fitting new dampers. Just because the dampers are a nice make and have come from a reputable dealer is not a guarantee that they will fit your particular car without checking.


A damper that’s too short.

Whilst I’m spouting and for anybody optimising those spacers or washer stacks on the damper’s top fixing bolts mentioned back in the thread, this is one technique that I have used in the past in an attempt to minimize those damper killer bending stresses that cars with damper hoops have. It just for interest and not a recommendation

Establishing and setting the spacer length whilst the suspension is at static ride height might not be the best approach. Depending on where the suspension is on its travel that length would vary. If you were to attach the damper at the bottom only and not constrain the top by just loosely fitting the top bolt with no spacer or nut and then bounce the rear, you would see that the gap actually opens and closes as the body goes up and down. I’ve found the gap varies by around 8 to 10mm. Most probably because the body moves at an angle of around 6 degs off the vertical with respect to the bottom fixing. The rear spring shackles are higher than the front so the springs aren’t operating in the horizontal.

With a regular trad (2 seater springs and no lowering blocks) the suspension’s static position is around 1/3 of the suspension’s full travel. Whoever originally conceived the trad appears to have aimed for the golden ratio, 1/3 droop and 2/3’s bump at static height, some might say . So to minimize the stresses imposed on the dampers the spacer ideally needs to be optimized for mid travel and that’s the tricky bit. In the past I’ve tried to eyeball a reference measurement at the extreme end of the movement whilst bouncing the car, say when the axle hits the drop stops and adjust by 4 or 5mm to optimize the spacer or washer stack length, each side. All a bit fiddly but perhaps worth the effort.

Sorry for the ramble

In the moment there‘s a lot to do, so no time for the MOG.

But I‘ve got the bumbstops and I‘m happy about their look. Now, the MOG is sleeping until February and so there is a lot of time for some work.

Thank you Roger for you help and fast service!

Greets René

Only for information: after Brexit it‘s clear some extra money to pay. At first I was surprised about 53,-EUR, but than with a look at the regulations I don‘t know how they do the bill. The official Tax/Custom information showed me more than 70,-EUR. So, happy with the bargain. And: for the good looking parts no problems with the money paid.

I think it's helpful to take a step back for a moment and accept what we're dealing with here is no more complicated than a telescopic damper conversion, back in the mid eighties replacing lever arm dampers with telescopic dampers was extremely commonplace, many different kits were offered for a host of classics running a beam axle, leaf springs and Armstrong lever arm dampers.

Some of these conversion kits were better than others, looking at Morgan's own attempt to replace lever arm with telescopic dampers we see an example of a poorly concieved and fundimentally flawed effort. Excessive damper inclination and the poor travel available imposed by the 1930's fashion of placing the axle above the outer chassis rails asside, in my humble opinion the more fundimental issue was to ignore the natural movement of the axle, it seems quite clear to me that Morgan fitted the damper eylets 90 degrees in conflict with how the suspension actually moves.

As the suspension on our cars compresses the leaf springs flatten and therefore lengthen, the swing shackles compensate by swinging backwards as is their job but as the axle is pinned to the leaf springs it must also swing backwards too. By fitting the damper eylets (the damper pivots) 90 degrees out Morgan created a system with some really horible twisting loads, these twisting forces result in premeture bush wear, snapped top bolts and broken bottom mounts that Morgan just kept making stronger and stronger untill they stopped breaking, this as oposed to properly studying the issue which soon would have revealed the error of their ways.

In its simplist form a telescopic damper is just a piston moving in a cylinder, for the piston to freely move unhindered up and down the parralel walls of the cylinder and avoid the dreaded and well known situation known as 'sticktion' where the piston can momentarily litrally stick in the cylinder, it's absolutely essential the rod is not subject to any side loads, for smooth operation a telescopic damper must be free to move with the natural movement of the axle or for sure you'll suffer 'stiction', at best the damper will function very poorly indeed and at worst things will simply start breaking!

Ironically it seems there was an earlier telescopic damper conversion kit for Morgans that actually got all this right from day one, the Rutherford kit put the damper eylets in the correct plain to allow the suspention to swing with the axle rather than fighting it at every compression and rebound event.



Morgan for whatever reason chose to completely ignore the good work of Rutherford, and persisted with their school boy error geometry

Very soon I'll reveal the way I've chosen to fix the issue, it's really nothing complex, because nothing complex is required to fix such a simple mistake. All I've done is study all my component failures and used that evidence in combination with my simple study of how the suspention actually moves, the results being as blidingly clear as the solution.

In the mean time, here are some examples of the evididence I've gathered along the way:











Quite litrally IT'S A SHOCKER

Not sure if you are aware Dave but the image hosting site you are using for all above photo's, imgbb.com, is displaying a caption asking for registration to view content.

No Richard, I wasnt away of that and it seems odd, the images appear for me?

I'm not registered for the service as it's offered free and has always worked well previously? Oh well, the images are really just visuals to demonstrate the point I've highlighted in words, hopefully you can read them?

Let's not forget we are dealing with the very simplest and well understood automotive suspension system here! While I fully accept it'll never be the last word in refinement and ride quality, it truly beggers belief why this subject continues to persist.

I can't help feeling it's a poor reflection on British engineering today if collectively we can't make a simple leaf sprung beam axle suspention arrangement work acceptably, and looking at the Rutherford setup the simple design challenge of fitting telecopic dampers to a Morgan was properly overcome years ago anyway!

Thanks for heads up on imgbb Dave. I've registered and have my own account which works fine. Unfortunately still getting the captioned images from your post as below.



Ironically this screenshot is saved to imgbb as well. You must also have set up an account to save images, but having tried VPN, clicking on thumbnails etc. I still get the captions - maybe I'm the only one but somehow doubt it

No you’re not the only one Richard!

Sir P

Maybe my second attempt above will work this time?

I'm really just trying to give some visual evidence to support my earlier comments, evidence I hope serves as a witness to the unnatural twisting loads at play?

I'm showing both my own failures here and similar related examples of those shared by others on this forum, however, the point I'm trying to make is they all very much tell the exact same story.

By failing to understand and respect the natural movement of the axle, Morgan created a suspension system that was fighting itself. The solution is simply to turn the damper eylets by 90 degrees, in doing so they can now pivot as they should and all the horrible twisting loads and their associated failures are removed.

Dave.

Sorry Dave, still no pictures just blue squares.

Sir P