1992 BMW 325i Crankcase Position/RPM sensor 2.0

The intention is to install the BMW harmonic damper, recovered from the M50 engine, onto the Warp 11 shaft.  The CPS (crankcase position sensor) will then be mounted in close proximity to the teeth of the damper.  During shaft rotation, the iron teeth of the damper will cause a change in the magnetic field within the Aluminum clad sensor and the wire coil within the CPS will generate an AC output signal.  With luck, the generated signal will directly drive the rpm gauge in the existing instrument cluster.  The additional benefit of this idea, is the availability of the integral pulley wheel that can be used to power accessories as needed. 

The machine shop fabricated a sleeve on the lathe that would serve as a spacer between the existing shaft (7/8” in the older style Warp 11 being used), and the 32 mm ID inner opening of the BMW harmonic damper hub.  The shop also produced a spacer (Picture DSC05315) that is about 0.0605” thick x 1.1330” ID x 1.2577” OD, and it can be used with the newer version Warp 11 motors produced after 7/1/2012.  The thicker sleeve was produced on a lathe and the key way was cut with a mill, while the thinner sleeve was rolled from galvanized steel plate.  I will have some extra adapters made and they will be available to other EVers upon request.

 

 

 

 

Picture IMG6595 of adapter sleeve used to connect the 0.875" shaft of the Warp 11 to the BMW damper hub whose ID was 32 mm.  Final dimensions of the sleeve were: 0.878 ID x 1.258" OD x 1.375 Long.

Picture DSC05315 showing the rolled adapter used to connect a 1.125" diameter Warp 11 shaft to the BMW damper hub whose ID was 32 mm. Final dimensions were about 1.1330 ID x 1.2577 OD x 1.3900 Long. This adapter has some flex during installation. 

  

 

 

 

Picture DSC05306 showing 7/8” drive shaft, machined sleeve (0.878” ID x 1.258” OD x 1.375" Long), and a 3/16” key, fully inserted and engaging both the 32 mm (1.260“) harmonic damper hub key way and the motor shaft key way.  The key way on this sleeve was over sized at 0.250" and future sleeves will have a key way slot of 0.1875" to better match the 0.1875" key.  The installed key dimensions were 0.400” x 0.1875” x 1.2502 and it was cut using a band saw from steel plate that was 3/16” x 1.25” x 6” (McMaster Carr).

 

Picture DSC05309 showing the 58 tooth damper bolted to the damper hub, and secured to the 0.875” Warp 11 commutator end shaft.

Picture DSC05310 showing oblique view of the installed harmonic damper.

 

The CPS will be mounted on an accessories end plate (currently under fabrication) and it will be in close proximity to the 58 teeth of the damper.  An Aluminum set screw shaft collar (picture DSC05317, McMaster Carr part 9946K22) was mounted on the shaft in direct contact with the motor bearing and the damper hub.  This collar fixes the dimension between the motor bearing and the damper hub. 

 

 

Picture DSC05311 showing a close up side view of the installed harmonic damper.  Note that there is sufficient room for a 0.625” (15.875 mm) Aluminum accessories end plate to be mounted on the end cap of the Warp 11.

 

 

 

Picture DSC05317  showing the set screw shaft collar prior to installation between the damper hub and the motor bearing.