Parallel Engineering

Triumph T150 after rolling chassis alignment. Note the sub-frame is not symmetrical to the frame centre line. Anyone know why? I'm assuming it's because the frame originally housed a twin engine and needed modification for the 750 triple.

As promised, news of the first oil change since ditching the one-way reed valve engine breather and re-installing the Norton Mk3 breather; after 3,000 miles no detectable emulsified oil out of the crankcase or oil tank! (I was thinking of including a photo of the used oil but probably should have done a video... perhaps). At any rate I wont be fitting a check valve to any engines breather system in the future. I'm aware a few Commando owners have fitted the very expensive (approx. £300) CNW reed valve, one reason because their oil pumps let-by resulting in a crankcase full of oil. They'd be better off sorting out the cause than treating the symptoms.

Torque is a rotating/twisting force. A Norton Commando's rear wheel spindle is recommended to be tightened to a torque of 80lbft. You can achieve this by using a spanner 1ft in length and applying an 80lb weight at the end of the spanner. Using a spanner 2ft in length and applying a 40lb weight applies the same torque.
A motorcycle is kept upright and stable at speed by the gyroscopic forces generated by the front and rear wheels. When the rider causes the bike to lean into a corner this generates a torque along the line F-R (see diagram below) because (on a Norton Commando) F-R represents the connection between the front and rear isolastics via the cradle, which also connects to the rear wheel swing-arm and also connects to the engine.
As the bike is leaned a force is generated at the engine head steady connection T to the frame. A perpendicular line from the pivot F-R to T has a length approx. 16" and is the same in principle as when a spanner is applied to tighten or loosen the rear wheel.
Several Norton Commando owners advocate fitting an additional isolastic mount at the point marked 'New' on the diagram. A perpendicular line from the pivot F-R to 'New' has a length of approx. 8". If the torque generated along the pivot F-R has a value of e.g 200lbft, then at point T the force would be approx. 150lb (T to F-R is approx. 16"). The Force at point 'New' would be approx. 300lb as length 'New' to F-R is approx. 8".
Therefore I conclude there's no advantage whatsoever fitting an additional under gearbox iso mount. There are a bunch of idiots on AccessNorton suggesting to remove the head steady altogether which will probably lead to cracked frame tubes. The designers got it right with the original positioning of the iso's and the fact Peter Williams never incorporated an additional iso on his record breaking, TT winning Norton Monocoque racer is proof of the original concept.

Parallel Engineering Precision frame alignment service correcting manufacturing mis-alignment of classic
motorcycle frames and rolling chassis. Norton Commando specialist.

Norton Commando frame going through the first stages of the rolling chassis alignment process. Click on photos for more info. www.parallelengineering.co.uk