VR Sensor Mounted Perpendicular to Trigger Wheel (Updated)

[kradicke]

Due to space considerations, I have to mount the trigger wheel in front of the crankshaft damper/pulley. This gives me a considerable gap of ~3" to anything I can bolt a VR sensor mount to. I have decided that to keep the installation looking clean and also to improve the rigidity of any sensor mount, that mounting the VR sensor perpendicular to the trigger wheel is the best approach. Which brings up two questions:

1) Are they any considerations that I need to address as far as trigger wheel design with the VR sensor mounted perpendicular to the rotating plane of the trigger wheel? As in, do the teeth need to be cut with diifferent side angles than when the VR sensor is mounted inline with the trigger wheel? Am I OK using a 1/8" thick trigger wheel, as I'm no longer registering my VR signal from the circumfrence of the wheel, but rather from the face .

2) As the teeth need to stick up beyond the OD of the damper (6.5"), how much larger should the trigger wheel be in diameter? Am I safe if I make a trigger wheel 7.5" in OD, which give me a tooth protrusion beyond the damper of 1/2". Would I be OK with 3/8" protrusion? Or am I getting ahead of myself in the planning of this, and I really need to select my VR sensor first and then machine my VR mount to determine where my VR beam will be located exactly in relation to the protrusion of the teeth?


Thanks! Kai

[kradicke]

Update to original post above:

I'm about to send out my CAD file for the trigger wheel to the waterjet co, so I want to see if I can get any comments this time around.

I need to mount my VR sensor 90 degrees to the trigger wheel, just as Nitropixie illustrates in this photo:



Do the teeth have to be shaped in any special way for this type of mounted sensor? Does the thickness of the trigger wheel matter? My trigger wheel is planned to be 1/8" thick (3mm). Will my VR signal be degraded or inaccurate with this type of mounting (see notes about VR signal zero-crossing unpredictability, http://www.megamanual.com/ms2/36-1.htm)

It looks like with the variety of trigger "tooth" patterns I see here, from the correct right triangle with the blunt tops, to straight slots, to drilled holes, that the the Megajolt / EDIS system is fairly robust in dealing with various qualities of VR signals.

Any comments would be appreciated before I commit to my trigger wheel design. Thanks!

[NITROPIXIE]

Hi Kradicke and welcome to the forum.

To answer your questions in my opinion you should be able to use a 1/8 thickness triggerwheel so long as:

a) the diameter of the trigger wheel was larger than the pulley and it protuded past the triggerwheel if mated to the pulley

or

b) if there was a substantial gap between the trigger wheel and the pulley, say 5mm


For the shape of the teeth, it would be best to have them at 10 degree angles with the sides of the teeth all pointing to the centre of the triggerwheel. This will then look square as they pass the VR sensor in a circular rotation. In fact the EDIS is only rising or falling edge triggered (can't remember which), which means the EDIS only uses the front or back of the teeth to calculate an ignition event so only one side of your teeth need be totally accurate.

I made my teeth have a depth (to the centre of the wheel) of 10mm??? which i now know was too large really (I did this as it was the size of the VR sensor) and teeth can be made smaller to between 6 and 8mm so long as the centre of the teeth passes through the centre of the VR sensor.

I hope this info is usefuol to you and keep us updated.

Any questions just ask

[kradicke]

Hi Nitro,

Actually been a member of this forum for years, just getting around to starting on this project - thanks for the welcome though!

I've attached my trigger wheel design as a 3D PDF file.

The pulley outside diameter is 6.5" which is also the minor diameter that the tooth profile is based on. Total OD is 7.5", so my teeth are 1/2" proud of the pulley (once I get this working, I can trim down the excess length of the teeth on the lathe). All teeth sides are designed so they are inline with the radius of the wheel, as you've mentioned, I did this to keep the edge of each tooth perfectly square to the sensor. The centerline of each tooth is spaced 10 degree from the next tooth, actually I designed this with a 5 degree tooth width and then a 5 degree air gap width... but that all works out the same.

The trigger wheel was designed to fit a mounting hub that I have to machine as well. It gives me four different mounting locations with reference to the missing tooth, plus the slots I've added to the trigger wheel allow for 70 degrees of adjustment. This plus the degree fudge factor in the MegaJolt software should allow me to easily put my VR sensor in any of the three spots I've got in mind.

Thanks for the tips. Hopefully the effort I've put into the parts I've designed so far pays off down the road when it comes to bolt the bits on and get it working.