Welding

Whether you can weld a trigger wheel to your pulley or not depends somewhat upon its construction. If it is a solid steel pulley then that's ideal, solid cast iron is OK but not ideal, anything with a rubber inset is not recommended for welding. If your pulley has a rubber insert as part of a harmonic damper system then it is recommended that you bolt your trigger wheel to your pulley instead of welding it. Pressed steel pulleys can be welded but care will be needed not to damage them in the process.

In addition to MIG/TIG or even ARC welding it is also possible to braze the trigger wheel to the pulley. However due to the large amount of metal that needs to be heated up this is not possible with DIY equipment.

The single most important thing to remember when welding to a solid steel or iron pulley is that it will try to absorb all the heat from your welder, without the weld penetrating properly. In order to get good penetration it is essential to pre-heat the pulley first; a few minutes with an ordinary blow torch is all that is required to warm it up enough to ensure a good weld.

The general process for welding the pulley in place is as follows. First ensure that you have a method of centering the wheel or ring gear and holding it in place. My preferred way of doing this is to machine a recess in the pulley on a lathe, alternatively you can just measure it up and then clamp it in place in a vice.

Recess machined for 5.75" ring-gear on a Cosworth 4WD pulley

 You can see another example of pulley that would be an ideal candidate for welding in the section on bolting onto a pulley where a Ford CVH pulley is used.