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MONTAC Enterprises
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Azle, TX 76020



Crank Position Sensor Trigger Wheel


Click for larger version..."Out with the old...

Here is a picture of the 60-2 trigger wheel that came with my Esslinger power pulley modified for use with the Electromotive ignition.  This wheel is intended for use with a magnetic sensor to create a crank angle or crank position signal.

However, I have since changed plans a bit regarding computers.  Originally, I was going to use an Electromotive TEC-3, but for reasons I won't go into here, I wouldn't recommend Electromotive products to anyone.

Then I decided to go with a Haltech E-11 and an MSD DIS-4 HO Ignition...  A GREAT computer system, but I've decided the MSD system is not reliable enough for my tastes (road racing vs. drag racing), and I wanted to go with a single vendor solution.

Enter Autronic...  I am currently awaiting delivery of an Autronic SM2, Model B Exhaust Gas Analyzer w/ NTK UEGO sensor, R500 Ignition and 2 Hall Effect Devices.

It's the last component that necessitated getting a new crank trigger wheel.  While I COULD have chosen to use a magnetic sensor and a reluctor adapter, I decided that changing the wheel made more sense.  It eliminates an electrical component from the system, Hall Effect sensors are digital, and properly installed, a Hall Effect sensor delivers a better signal.


"...and, in with the new!"Click for larger image...


So, I cranked up the AutoCad, grabbed a set of calipers, and went to town...

The SM2 chipset version I chose only requires a 2-tooth trigger, but the teeth need to be 5/16" wide, thick, and tall above the base wheel.

So, I drew up a wheel that has the same inside diameter as the power pulley hub, and the same outside diameter as the 60-2 wheel.  Hopefully, I can modify the Esslinger magnetic sensor bracket to hold the new Hall Effect device.

I did however make a modification to the overall design approach...

Click for larger version...Esslinger makes their wheel from 1/8" mild steel.  Then they add an aluminum spacer behind it that  is slightly oversized in thickness.  Tightening down the power pulley bolt will clamp the trigger wheel in place.

Making the wheel thicker meant that the spacer would have had to be thinner.  Rather than try to make a thin spacer, and in consultation with my machinist, I decided to make the trigger with an integrated "spacer".  Thus the reason for the small 1.5" diameter "step" you see on the engine side of the wheel.

I had the machinist cut the wheel over-sized in thickness/tooth diameter, and undersized in hub diameter, so that I could custom fit it.

I hand lapped the step until the overall thickness matched the Esslinger components exactly.  Then, I hand lapped the center hole until it just fit  on the power pulley hub.  It actually came out as a better fit than the original wheel.

Once mounted on the crank, I will use a dial indicator to verify that the teeth are exactly the same height above the crank centerline. If not, I will machine the longer one down to match the shorter one.


Click for larger image...Here is the trigger wheel mounted on the power pulley.  A perfect fit.  And you have the ability to set the wheel anywhere in relation to the pulley/crank that you need to.  This is important since I am not quite sure where the Hall Effect sensor will be mounted in relation to the pulley/wheel.

Once the sensor is mounted, you simply set the wheel such that a tooth's leading edge is 1mm past the sensor centerline when the crank is at 60 degrees BTDC.

Then tighten down the power pulley bolt and confirm the setting.


Trigger is finished except for electroplating it to prevent corrosion.



Copyright (C)2003 MONTAC Enterprises.  All Rights Reserved©
Revised: March 03, 2006 .