Chuey wrote:So that was a car shock, right? Is there any specific information on why riders liked the twin shock bike better? Was the twin shock based on the same frame?
Chuey
My research indicates that the shock was originally an automobile item,
and also that the shock's performance characteristics were not as well suited to the bike
as the twin-shock arrangement.
Gietl was a proponent of the new mono-shock technology
and implementation would have involved significant trial and error ...
Error seems to best define this stage of development.
The same Rob North BMW-frame design,
which was closely modeled after his successful Triumph "low-boy" frame,
was used on all 3 original North-BMW F-750s.
Udo Gietl introduced and experimented with the mono-shock arrangement
and I would suspect that any or all of the frames were subject to his experiments.
Stretching the rules to the breaking point, a mono was also used on Gietl's R90S Superbike.
Shock relocation had been legalized to oblige Kawasaki,
and legend has it that Gietl responded that the BMW's shock had been relocated –
to a shelf in the garage.
Of the 3 North F-750 BMWs, Gary Fischer's twin-shock was converted to a mono in 1975.
(now in the Barber Museum),
Reg Pridmore wanted nothing to do with the mono and his remained a twin-shock
(in the collection of Even Bell, Irv Seaver Motorcycles) ...
and then there is the Lufty once-owned bike.
The e-bay ad copy that makes the claim "the only North-BMW mono" – misinformation, IMO.
Tim Shepherd wrote:If it is a car shock, I can't imagine it working to its full potential in a horizontal position. I would assume the damping would be less than optimal, unless the shock was specifically designed to work in that position.
Theoretically, the position of a shock will be of no consequence to the ability of the shock to work,
and although it's progressive characteristics will depend upon specific geometry,
more likely the downfall of the F-750 mono was a fault of spring rate, damping, or rebound choices.
Bear in mind that shocks of this period were not readily tunable / adjustable -
ME109 wrote:So what is with this airhead setup? Is it standard?
For a very short period of time, Luftmeister sold a "mono-shock conversion kit".
Short lived and very rare –
Perhaps because Lufty was not able to sort out a suitable shock as well.
Back in the day, Lufty marketed "boot-leg kits"
that
emulated, at least "visually", virtually every technology that worked on the track.
