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What ever happened to this


Well Known and Active Forum Website User
VOC Member

Found this in an old Mag, It jogged my memory, I had seen this before.
Its an HRD fitted with a cross rotary valve head a good attempt to leave the popppet valve behind (Even Joe Craig tried something like it on a Manx) but does anyone know more about what happened to this particular machine?

ray vinmad

VOC Drawings Manager
VOC Member
Have a look on the Cross Manufacturing website.
It has been at VOC rallies in the past & I think it still owned by the company.


roy the mechanic

Well Known and Active Forum Website User
VOC Member
A bit like the sleeve valve "silent knight" it did not live up to the expectations (hype)! If a few more miles were acheveible between decokes it just may have had a happier foot note in history.


Well Known and Active Forum Website User
Non-VOC Member

Nulli Secundus

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Yes that sums it up I think. However, I have never seen HRD Pythons with forward mag engines. The front down tube of the frame is not straight like it is on other Diamond frame Vincents. So the question is :- Did Cross modify the frame, or did Vincent do it to accommodate a forward mag Rudge Python engine? The bend appears to be necessary because with out it the tube would be pointing at the magneto.

Jim Richardson

Well Known and Active Forum Website User
VOC Member
I am pretty sure that the bike survives at Cross, Jacqueline Bickerstaff wrote several articals about this and other rotary valve engines, in Realclasssic magazine a couple of years back.
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