I'd be interested to see what it looks like and how it works, although I may have been luckier than some of you guys as I've not had that many issues with bump steer. Makes the journey all the more interesting though.
So, I've done some more reading and I have a few considerations to post. The front geometry is bad for several reasons including:
1) The steering rack is too wide for the car, requiring short tie rods instead of longer ones. When the suspension goes up or down, the short length of the tie rod compared to the longer control arms causes the end of the tie rod to pull toward the chassis more quickly than the ends of the control arms. This in turn causes the steering arm on the upright to be pulled towards the chassis faster than the upright, which causes the upright to rotate about the kingpin axis. As this happens, the wheel's toe substantially changes.
The usual way to avoid this problem is to use tie rods that are about the same length as the control arms and to locate the steering rack so that the tie rod is parallel to a control arm.
2. The kingpin axis doesn't even come close to intersecting the tire contact patch. More precisely, the axis of the kingpin does not pass through the plane of the wheel at ground level. This means that there is essentially a lever arm giving the tire leverage over the steering. So when you hit a bump, the wheel is pushed backwards, this in turn creates torque around the kingpin which manifests in a sudden, violent jerk in the steering wheel. Basically the offset of the kingpin is dead wrong. This sort of error is quite literally a text book mistake,
"It is disastrous, as some of the pioneer designers discovered, simply to move the steering axis (the kingpin) smartly sideways [inwards]. That makes room for the hub and permits the swivels to be moved further apart, thus reducing the stresses on both. Sadly it also means that every road shock tries to twist the wheel about its steering axis - not exactly the kind of feel we were looking for. Far from each wheel being naturally self0centering, each will be trying to twist itself around its steering axis in a state of constant conflict with the other. Such permanent tensions are bad news in any kind of engineering, but especially in a system as safety-related as the steering."
I'll post more on this later. I've been very busy working 10-12 hour days at a new job, so my free time to post is sparse. I hope this helps explain whats going on with our beloved trikes. They are wonderfully fun, and I would enjoy mine even more if it didn't occasionally try to rip the wheel out of my hands and kill me when I hit bumps on the freeway (75mph+).
Good night everyone.
P.S. The exhaust heat shield mount tore out of the muffler last night, leading to quite a lot of noise and some improvisational welding. Enjoy -> http://www.youtube.com/watch?v=m5PbUq8lvww
Well...that video really puts the problem into perspective...
That seems like a substantial amount of steering deflection on suspension compression....
I realize that this is a design from the 1930's, but it's hard to believe that it can't be fixed with a modicum of clever engineering - I'm suprised MMC let this through...
Great video clip. So obvious first time I say the 3Wheeler raised and lowered on a lift. Sliding suspension and a flexible chassis was fun to drive on past Morgans but with the aid of computer programmed and CAD, Morgan should have done way better with a little thought!
I just had a close look at some Triking photos and I could see that the tie rods seem to be parallel to the lower control arm and that a line taken through the kingpin seems to fall to the inside the edge of the tyre contact patch. But then the Designer, Tony Divey, was an ex Lotus employee.
Good work!!Thanks for the detailed post. I had a JZR 20+ years ago - a morgan type replica. It had Ford front suspension and steering the steering was very low at the front of the car - it worked brilliantly, looked great and NO bump steer!!
I also built two JZR's about 20 and 15 years ago. The first was a Honda CX 500 based one that handled very well but needed a bit more "go". The next one was a Moto Guzzi based kit with plenty of "go", a SP1000 round barrel engine, twin spark heads, pumper carbs and big valves. Like my M3W, it looked great, left 50 yards of black line, lots of tyre smoke if you wanted.... and had bad bump steer. I spent many hours shimming the steering rack to reduce the bump steer to acceptable levels and sorted the prop shaft out so the transmission worked properly. It can be done Morgan! If I can do it in my garage with a few books for guidance I am sure Morgan can, if they want to?
I had a Grinnall Scorpion K1200RS after that, great handling, stunning performance but I feel I am lucky to be alive after 5 years of ownership. A wild machine.
I like the M3W as it is fun at 50 mph, rather than 100. As a serial 3 wheeler nut, I was attracted to the M3W, I just wish it handled as good as it looks. Any more info on these suspension kits then? Not holding out much hope of Morgan fixing the suspension soon and I don't fancy skipping around the road much longer. And I almost ordered a Triking.......well engineered, light and a nice Guzzi engine but not the looks of the Morgan.
My JZR was a 650 Honda - it went very well too! but the Guzzi was the best looking by far IMO the Pan was a beast but just looked awful:(( I too was attracted to a Triking - but I could never fall for the very pointing nose! They fetch high prices today for a good one. so now I have gone full circle back to the Morgan - and I love it - just hope the suspension issues get a "fix" - there was a post on here that Williams were working on something:))) must go - off to the Shelsley Walsh Bfast doo:)))
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