So what else has been going on here. Among other projects I have completed the Chevy II clutch installation for umteenth time in preparation for the Pure Stock Muscle Car Drag Race Sept 13-14th in Stanton, MI. It turns out the previous clutch was defective which lead to it's premature failure. See page 346, post #6909 if you wish to relive that, um...mis-fortune.
Moving forward, before a new clutch is installed, it's standard practice to have the flywheel face cleaned up.
This is the machine, a flywheel grinder, which is used to clean and true up flywheels.
The flywheel is placed...
...and then secured on this mounting surface.
On the bottom of the grinder is a grinder wheel covered with industrial diamonds which does the all the work.
Here, in the foreground, you can see coolant is flowing on the flywheel before the grinding operation begins. The coolant also helps flush ground material off the flywheel during the grinding operation. Note the grinder has been lowered into position just above the flywheel at the top.
The flywheel is revolving on the mounting plate and the grinder wheel is also revolving as it's lowered onto the flywheel. Light cuts are taken to prevent removing too much material off the flywheel at one time. That minimizes heat build up. If the flywheel and grinder are always in motion it helps prevent flat spotting.
When finished, the flywheel looks like this, coolant is still on it. We're looking for a flat surface and with a certain smoothness. Engineers or machinists refer to the roughness or smoothness of a surface as expressed in
RMS,
Root-
Mean -
Square.
RMA(RA) Root- Mean- Square(Roughness Average), it is a term used to measure the roughness of a surface,RMS 63 is a smooth surface finish, RMS 125 is an average manufacturing surface, RMS 25 is a very clean smooth surface finish.
Surface roughness of texture is the measure if the finer surface irregularities in the surface texture and is composed of three components: roughness, waviness and form. These are the result of the manufacturing process employed to create the surface.
Surface roughness average (Ra), also know as arithmetic average (AA) is rated as the arithmetic average deviation of the surface valleys and peaks expressed in micro inches or micro meters. ISO standards use the term CLA (Center Line Average). Both are interpreted identical.
Where Ra is the arithmetic average value or departure from profile front eh center line, the equation for four as-measured values:
Ra = CLA = AA
M1+M2+M3+M4/4
Where:
Mx = measure value
Root Mean Square (RMS / Rq / Rs) can be calculated by:
RMS = square root of- M1 squared + M2 squared + M3 squared + M4 squared/4
The ability of a manufacturing operation to produce a specific surface roughness depends on many factors. For example, in end mill cutting, the final surface depends on the rotational speed of the end mill cutter, the velocity of the traverse, the rate of feed, the amount and type of lubrication at the point of cutting, and the mechanical properties of the piece being machined. A small change in any of the above factors can have a significant effect on the surface produced........but I digress, I'm just a simple pilot.
I had the flywheel ground to approximately
RMS 30 finish. Too smooth and the clutch disc will slip on the flywheel, too rough and it will tear up the clutch disc.
RMS 30 I'm told is a good average finish for a flywheel.
So with the flywheel completed the rest of the installation was done....again and now I've driving the car every chance I can to break the clutch in before we go
drag racing.
Stand by..................
Thomas