Custom Trigger wheel

alpine-jeff · Post by **alpine-jeff** » Sat Apr 04, 2009 9:56 pm

Hey all you mega dudes and dudettes,

I have an old British 4 cylinder sports car that I'm keen to try out an MJ with to see if it helps it run any better (cause it can't run a whole lot worse).

My challenge is that the crank pulley is made of aluminum so I can't weld a normal trigger wheel to it. It has very limited space so I can't bolt a t-wheel to the front or rear of it.

So I'm seriously considering ( having a machine shop ) drill 36 holes around the radius of the pulley, tapping and screwing in headless allen bolts into each hole, so that the bolt heads remain flush with the outer rim of the pulley ( or even recessed a tad ). My question, to this group of mega folks: will the 36 flush/recessed steel allen bolts, when placed into an aluminum pulley, trigger the hall effect sensor in the same way as a notched steel trigger wheel does?

Also, does anyone have any experience with nickel plated parts and their ability to correctly trigger?

Thanks for your time, help and insights!

Jeff

Post by **brentp** » Sat Apr 04, 2009 10:06 pm

Hi Jeff,

Something along those lines should work. What might be easiest to do is simulate it using a hand-drill or lathe off the engine, and then observe the VR signal using your 'scope.

With allen head bolts you will likely see the actual pattern of the hex socket in the scope trace, possibly confusing the EDIS module. What might work better that keeps with your theme is to drill/tap holes in the aluminum pulley, screw in bolts, then *cut* the bolts off flush with the pulley, so a smooth surface is presented to the sensor. Cutting the heads off and then machining the surface in a lathe might be the best way.

Let us know what you work out! It would be very interesting to see.

Gilesy998 · Post by **Gilesy998** » Sat Apr 04, 2009 10:48 pm

I'd suggest the same as Brent has mentioned.
My method would be this: drill the 35 holes about the same depth as their thread diameter and tap them full depth. Wind into these holes some mild-steel screws (even cheap cheese heads would be okay) with effin' strong Loctite on the threads, hacksaw the protruding screw and head off leaving around one thread on show, then have the remainder or the screws spun off on a lathe to the diameter of the original alloy pulley.

G

alpine-jeff · Post by **alpine-jeff** » Sat Apr 04, 2009 10:52 pm

Hey Brent,

I hadn't considered the hex indentation in each bolt used by the wrench. Great catch. Using a regular bolt, using a small cutter and grinder should work fine to remove and smooth.

Any thoughts on material differences, like nickel or zinc plated materials to avoid rust issues?

Also, is it acceptable to ask folks on the forum for quotes on such a job? I don't recall seeing any individual commerce exchange rules.

I will definately keep the board apprised of the project's progress, issues or otherwise.

Thanks Brent! Hope all is proceeding with your other projects.

Very best,

Jeff

Post by **brentp** » Sat Apr 04, 2009 11:00 pm

Hi Jeff,

Glad to help. Anti corrosion coatings should not be a problem.

On the other projects, I'll be posting an update very soon!

alpine-jeff · Post by **alpine-jeff** » Sat Apr 04, 2009 11:01 pm

Hi Giles,

Your post came in just between my reading and replying to Brent's -

Thanks for your sequence and suggestions. I hadn't mentioned the loctite in my original post, but I wouldn't consider it otherwise. I was initially concerned about the items, which ever I decided upon, coming loose and spinning out at 5k rpm. In addition to making the engine run poorly, it could go right through the bonnet, fender or a by-stander. I'm not sure my insurance covers bystander damage by trigger bolt. I'll have to check on that.

Have either of you heard of anyone making or using this type of trigger wheel? Successfully?

Thanks guys! I sincerely appreciate your time and help with this. I'm honestly tired of thinking about this project. I want to be out driving this car with the top down.

Very best,

Jeff

Gilesy998 · Post by **Gilesy998** » Sat Apr 04, 2009 11:16 pm

I recall someone was in the process of putting one together, but never heard or saw anything of the finished job. That mught just be oversight in my part though

There's no reason at all why it wouldn't work - so long as the pulley is DEFINATELY non-ferrous (like the aluminium alloy in your case) the sensor will see 35 teeth and an air gap, just like the stock Ford trigger on my car.