Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Steering kickback

From this photo.........
http://www.flickr.com/photos/faasdant/6366344269/
You can see that the line through the steering axis (would be kingpin on a trad) hits the road inboard of the tyre contact patch. This creates a positive scrub radius, which was common in cars until ABS and split braking circuits became the norm. In fact I recall that Audi were the first to promote negative scrub, which is more stable in the event of partial brake failure or a tyre deflation. Positive scrub lets the tyre roil around the steering axis when steering so in theory is lighter than close to zero scrub, but kickback is also a feature. This is not the same thing as bump steer, which as already posted above in this post is about track rod inclination, and toe in/out on bump/rebound.
The other interesting feature is the reclining damper angle. Ideally dampers should be as close to vertical as possible. Where MGB's have been fitted with IRS using Sierra 4x4 rear diff,the rear dampers are steeply inclined and I know of at least one case where the damper rod snapped as a result of the geometry. Maybe it started out slightly out of true. I also read this week that where the spring is inclined, it gives a falling spring rate under bump, which usually means a higher rated spring than if the same installation was vertical. So as in any installation, there are compromises. To reduce kickback you really need a tyre contact point close to the steering axis - so more wheel inset if all else stays the same, but this will increase steering weight at low speed.

Just in case you hadn't found my thread, Dab of Oppo, thought I'd bring it back to the top for you to peruse.

As a matter of interest, I took my car back to the factory just before christmas, where they promised faithfully that they had sorted the bump steer by carefully setting up the front end - guess what, nothing has changed, except the steering wheel is now, annoyingly off centre. What a waste of day that was!

Hi Paul
Thanks for high lighting your previous thread, It is just the same as my experience.
On undulating country roads at the national speed limit it will wander all over the place and will not track in a straight line. At first I thought the rear wheel was out of line so deft use of a laser level and a couple of engineers squares soon put that to bed. Hence checking the bump steer.
If I get chance today I'm going to fashion something temporary to hold the track rod about 1.25-1.3 inches higher up than standard, i.e.. in mid air, and then re-measure the bump steer.
Personally I think the steering arm is set much too low on the front upright.
I understand Mustangs in the good old US of A have the same problem and there are many anti bump steer kits available off the shelf to rectify this.
Isn't google a wonderful thing.

There is no great problem with inclining tele dampers, they are typically fine down to around 10 degrees from horizontal or at any angle if gas charged with a separator piston.
True the MTW front suspension gives a falling spring rate geometry as designed by MMC. The original SUPLEX (they also supply the 4 wheeler springs) dampers had a component that looked like a long progressive bump stop on the damper rod to give a significant rising rate, they also had an internal rebound spring to increase roll stiffness - the current production uses SPAX that has no such rising rate and no internal rebound spring - hence the worse handling and more roll. Theres progress for you - PJB.

Hello Peter!
And welcome to TalkMorgan

"the steering arm is set much too low on the front upright"

Well, on the face of it, it is either that or the fact that the rack is too high, because of the necesity to clear the bellhousing, so, not much can really be done with the rack position. I seem to recall that the steering arm is around the same height as the centre line of the hub, which would seem to be the right place, but with the rack too high, this is obviously not perfect. I did wonder about spacing the track rod end up from the rack, but that is an unsafe solution, and without the means to re-engineer the front steering arm assembly, I have had to give up and put up with, in my opinion and on my local roads, awful steering feedback. I get the feeling that the factory are too busy basking in the success of the car to care much too, so only when orders start trailing off will they start looking a bit more seriously at this problem. Your fresh thought on the subject would be most welcome.

On a different topic, and also raised here some time ago, is the wholly unacceptable weight of the vehicle, how Charles Morgan can call it 'light weight' I do not know!

So frustrating that it is so very nearly great, but let down by these annoying things.

Congratulations on the Roadster Mike. I am sure you will enjoy it.

I agree on the issue of unresolved development problems, it really is a shame but I guess we have to accept that Morgan will always have limited development resources.

Personally I think it is a shame that when Morgan decided to develop the new M3W that they did not start with the tried and proven Triking. Even if they did not want a Guzzi engine I believe the Triking would have made a good starting point with the additional advantage of being a British design.

The style and the finish of the M3W is better than the Triking but so it should be for the extra £££s

As Graham has said, good to see you on TM Peter.

My M3W has just come back from the Works, and on the some 110 mile journey back home the steering seems to have been transformed. I believe it has had a new steering rack fitted and whereas before, I was getting quite violent kick-back after hitting a pothole or rough stretches of road now it is much smoother and whilst the issue has not completely gone away, it is much reduced both in intensity and duration.

Unfortunately I do not have the mechanical knowledge that some of the other posters here have on suspension systems, so do not know if this is also partly down to the revised stronger suspension that has also been fitted?

Whatever it is the handling of the car has been transformed and combined with a much quieter bevel box, I really enjoyed the drive back.

Cheers
Brian

Does anyone know what the new steering rack brings to the game that the original one lacked?

I think that what MMC have changed is the strength of the lower wishbone, this should not in itself change ride and handling. The loads going into the wishbone are of course related to what one drives over & how fast and how the spring/damper unit absorbs the shock......been there already.
MMC of course did not start from a clean sheet of paper with the three wheeler, they bought out Pete Larson of ACE in Seattle http://cycle-car.com/ - maybe if they had started from scratch then ....but then on second thoughts... maybe not.
Good to see some 'old' friends here too, it's nice to put my oar in the water, trying not to cause more than very gentle ripples now and again. Regards PJB.