Aluminum Adapter Casting Process

It is clear to me that one of the reasons that EV conversions are not more popular is the difficulty of getting the adapter plate and hub adapter. 

 I have an order in for a machined set of transmission and hub adapters, but after 5 weeks, no news.  And not even any news about the news.

On the bright side, David Fischer has been busy this last week in Boston working on Plan B, and he has prepared the mold template that we will use to have a foundry cast our Aluminum adapter concept.  I will share some thoughts about the process and some  photos.  This process can be done for any transmission.

Disclaimer:  I am not an expert, but I will try and explain what I think that I have learned about each of these processes.

Point:  There is trade off between expensive precision machine shop time and careful EV‘er  fabrication time.  Regardless of which method is used, all have in common the requirement to know the precise orientation of the alignment dowel pins relative to the center of the spline of the transmission.   Additionally, the overall distance between the face of the engine block and the face of the drive shaft flange (“the critical dimension”) must be measured so that the final hub adapter will correctly embrace the spline of the transmission. 

In theory, if time and money were of no concern, one could buy a thick and expensive slab of Aluminum, and after the machine shop CNC is programmed, after many hours, the Aluminum would be carved away to create a three dimensional adapter made from a single piece of Aluminum.  Lastly, the required precision dowel, Warp 11, and mounting holes would all be bored.

In an alternative second way, one can take three separate slabs of Aluminum.  The first slab is cut to the required dimension to allow the entire face of the transmission to be covered.  The second piece would be faced so that the Warp 11 can be bolted to it.  The third piece, essentially a gigantic Aluminum washer, would separate the Warp 11 mounting plate from the transmission mounting plate.  The overall thickness of the three plates must match the dimension required to properly locate the future hub (or key way) shaft adapter relative to the spline of the transmission.  As an aside, one would need to drill and insert roll pins to lock all three pieces together before the machine shop does its magic and bores out all the required mounting, dowel, and the 4 inch center hole for the Warp 11.  This second approach might be expected to be less expensive, since less Aluminum would be sent to scrap, and less CNC machine time would be required.

Both of these methods have in common that each adapter is custom made, one unit at a time, with very significant machine shop billing.  The precision dimensions that were required and measured for the first build, represent the only part of the fabrication that would transfer to a future build.

A third way is to prepare a wooden form that can be used over and over by a foundry to make multiple copies of the same adapter upon demand.  After the crude Aluminum casting is heat treated, it would then be sent to a machine shop, and if properly designed, less overall machine shop effort would be required to refine the rough casting into its final precision form.  We will have several castings made in the first run and we will machine 2+ of them for testing.  After we have installed and fully tested the prototype, we hope to be able to offer these adapters to other EVers. 

If the mold form is properly constructed, the machine shop would take the Aluminum casting and face only the limited area that contacts the transmission face, the landing area of the Warp 11, and the small landing areas of each of the bolt heads that are used to attach the adapter to the transmission.  Finally, the precision bore holes for the dowel pins and the remaining mounting holes would be referenced to the exact center of the 4 inch opening required by the Warp 11.

The mold form that David is making is being fabricated from poplar wood board stock from his local lumber yard.  The piece was not wide enough, so he cut and glued the required pieces to create boards of the required width.

                          

Picture 0774 showing the glue assembly of poplar boards to create sufficient width for the adapter plate construction.

The largest piece of the adapter will be mounted against the face of the transmission.  It must allow for all of the mounting holes and it will have precision bored holes for the dowel pins.  The wooden form must also be larger than the final casting by a calculated amount so as to compensate for dimensional changes as the casting cools back to room temperature.

Picture 5641 showing the forming of the transmission mounting outline.  A digital image was first printed on paper and then glued to the surface as a guide for the cut.

Picture 0778 showing one of two required round spacers prior to being glued together.

Picture 5634 showing the two glued spacers after lathe work that created an inner ledge.  The ledge in the final Aluminum casting will be machined so that the heads of the Warp 11 mounting bolts all rest in the same plane.

                         

Picture 0789 showing the view from aspect of the Warp 11.  Note the glued disks that are positioned for the dowels pins and the mounting bolts.  These small areas will require less machine shop time to face off as compared to facing the entire surface.  The center of the wooden circular area will next be drilled out to about a 3.75” diameter.  The final 4” center Warp 11 hole will be precision formed at the time that the dowel pins are bored  by the machine shop  These are critical dimensions.  The remaining mounting holes are much less critical.


                         

Picture 0792 showing the view from the aspect of the transmission.  The outer (top most)  face, when cast in Aluminum, will bolt against the transmission housing.  This outer top face and the opposite face shown in picture 0789 must both be machined flat and parallel to each other to force the transmission face to be parallel to the Warp 11 motor face. 

After drilling the 3.75” center hole in the wood pattern shown in picture 0792, our next step will be to obtain good dimensions of the relative positions of all of the bolt holes relative to the dowel pins and the center of the spline shaft.  These dimensions will allow the machine shop to complete the fabrication after the casting faces have been prepared.  The thickness of the casting, and therefore the separation distance between the face of the Warp 11 and the transmission, will be finalized when the transmission face is machined flat.  This last machine shop work will allow for any variations in the casting thickness to be corrected.

Stay tuned.