I say:
Vibration at a specific speed that goes away below or above that speed IS WHEEL BALANCE, plain and simple. Shimmy damper vibration can be induced at a range of speeds and does not go away with increased speed.
".....some mention must be made of that alarming phenomenon the dreaded Morgan wheel wobble ....The trouble is associate with the sliding pillar supension system"
This partial quote is from Colin Musgrove's book "Moggie".
"I once drove a Morgan where the Bronze plate had come adrift. At around 35mph there began a shake like the hinges of Hell had come loose. this is called the St Malverns dance, a bit more speed can eliminate the shake..."
This quote is from the legendary Cuthbert J Twillie.
Wheel balance may well be the issue. Or may be a contributing factor. But to say that it is "WHEEL BALANCE plain and simple" is a bit pedantic in the concept of the Morgan front end.
If the OP has indeed eliminated out of balance wheels, then investigation into different areas is required.
Brian
