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Norton NHT Rolling chassis
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TOPIC: NOTICE-Commando ISOLASTICS

NOTICE-Commando ISOLASTICS 26 May 2023 07:16 #1

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Commando isolastic's are more suspension related than power production, so iso's are going to reside here in the rolling chassis section.

PURPOSE
The commando isolastics did evolve as the 8 year production ran. Flexible compliance to minimize coupling to the rider is the main goal, yet minimizing the flexible flyer handling is an additional important goal.
The front, rear and top isolastic each add there own characteristics to the vibration mode and resonances and handling.

### NUTATE: oscillatory movement of the axis of a rotating body.
To be very specific, the nutation energy comes from rotation of the 22 lb. flywheel, oscillating connecting rod and vertical connecting rod and piston movements. The energy is transmitted to the whole rubber mounted power plant, engine-transmission and cradle through the crankshaft main bearings.

###DESCRIPTION
The iso's have two functional components.

#INNER column
The inner column is hard bolted solid to the frame tabs.
The inner mount is comprised of stacked component on the center bolt. All together they comprise the "stacked length" between the two 06-0422 front engine mounting collars These collars also restrict movement of the 06-3556 PTFE or urethane washers during drive train nutating motion.

The internal rubber components provide compliant connection and support between the inner and outer columns.

#OUTER column is held off the rigid frame via rubber ISO mounts.
The outer column floats on the rubber iso's installed in the 06-1410 front engine mounting. This body and two tube caps are shorter then the inner column. The "freeplay" between the inner and outer columns is adjustable using selected captive shims to reduce the gap to the desired amount. Typically 0.010" or less.
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commando ISO rates-front 26 May 2023 07:55 #2

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FRONT ISO RATES
One set of "discrete components"(upper left) and 2 each "rubber on a stick". One from many years ago(center) and one new soft style(right) untested and not measured yet...on far right are packs of end play shims, .005", .010", .020', .030" for setting "discrete component type isolastic" end play.


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commando ISO rates-REAR 26 May 2023 08:14 #3

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REAR ISO RATES
Dan Battle wanted to salvage a swing arm from his "donor" engine cradle. Well try as I might, oil soak, 20 ton press, oxyacetylene torch, I finally had to admit defeat. A thin abrasive wheel on my buck-eye grinder strategically cut the swing arm free from the cradle. I saw something new to me...an unfamiliar ISO rubber. As I typically have curiosity when I see something new on a Norton part, I had to dig in.
I will be starting on this series 1 Commando REAR ISO MOUNT which contains, to my surprise, a METALASTIK 13/1782 unit pressed into each end. The construction is a cured&molded rubber in between an outer 1-1/2" steel tube and inner 1/2" steel tube. There is also a steel tubing spacer to create the required full length dimension. According to the parts book, there should also contain secondary rubber buffers sitting on the inner tube.

I have done some new tooling to measure the longer REAR ISO rubber stick assemblies. To enable use in the fixture, I had to torch cut the ISO housing tube out of the engine cradle and lathe cut off the residue furnace braze and steel plate. A pix of the new ISO measurement rig, I first set up around 20+ years ago, to do my first graph of the front ISO deflection rates of various rubber size and hardness. The pix below is the testing of Dan's early series one rear ISO. Components seen below.

Mounting and compressing the later ISO components within the tube significantly contribute to the isolastics compliance rate.
You may note others trying to determine ISO compliance rate based on surface durometer.. laughing..
sorry that doesn't work.
Now to dismantle this early Commando rear ISO 06-0432 ? metalstic insert and it's additional spacer/buffer items. Note in the graph the kink in the line starting about .070", I'd bet a beer that is the clearance until the secondary internal buffers become restrained by the ISO housing tube. Though I can't see them (yet), I think this proves they are there.
Rear iso
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