Friday, February 18, 2011

Finishing the Generator Cover

I managed to stay late and squeeze in some more machining to finish up the generator cover.  After ending the last post with the first setup finished I then machined a simple fixture plate to locate on the interior features of the part.  it used the stator mounting bolts and a couple of mounting holes with dowel pins to keep the part accurately aligned with the previous operation.

Second operation fixture plate:


Loaded in the mill with a part installed:


After rough machining:

With it's brothers:



I gave one a light glass bead blasting to reduce the reflectivity of all the shiny machined surfaces.  The result looked great:


The round cap part has M50x1.25 metric threads that were made on a lathe with a normal threading cycle, like most externally threaded parts.  The cover part then needed an internal M50x1.25 thread which would need a special M50x1.25 tap, which would be very expensive, or I could make the thread using a thread mill, which is the option we used.  Thread milling uses a 60 degree V-shaped cutter that is moved in a helical path that corresponds to the thread profile.  If everything is done properly you end up with a very clean and accurate thread without the need for a tap.

Here's a video of the thread milling operation.  It is done 3-4 times with an incrementing depth of cut and a small finish path.
video

These parts are now finished and the next step is to make the gerotor pump and bearing shaft cover.  Look for a post sometime next week for more.

Until next time.

Thursday, February 17, 2011

Starting on the Generator Cover

Back to making chips!  This post is the first part of fabricating the generator side engine cover.  this is a 2 piece cover with a threaded inspection port to give access to the end of the crankshaft.

I'm doing the same process as used with many other parts: first machine the inside surfaces from a billet of aluminum, then in a following post I'll machine a fixture plate that locates to these features and then machine the external surfaces of the part.

The internal features and mounting holes are critical to the correct placement of the stationary stator with respect to the crankshaft mounted rotor.  By machining these in one setup I am assuring high accuracy between these features.

Skipping directly to the chase (I forgot to photo intermediate machining steps!)  Here's 3 sets of parts:  3 completed access ports and 3 1/2 machined side covers.

Threaded inspection port:

This was a 3 operation part: first turn the thread, counterbore and o-ring sealing groove, then turn around and turn the outer profile, then switch to the mill to make the 17mm hex for wrenching.

Generator side cover at the halfway mark:

This operation created the outer profile, mounting and locating holes, and mounting holes for the Electrx race stator.  This product from Electrex is a low profile race generator kit meant to replace the larger systems found on production Japanese motorcycles at about 1/5 the cost of a similar race kit item from any of the manufacturers.  Build quality was excellent and they are great source for low volume OEM sourcing of generator components.

Here's the stator bolted in place with the 3 phase wiring exiting though a slot in the gasket surface:





Next up is capping the ends of the valve covers and then final machining of the welded cylinder heads and valve covers.

Until next time.