I’m installing dual Lightspeed ignition systems with a B&C standby alternator on my IO-550N. As some of you may know, a magneto must be installed to keep the magneto drive gear in position. The drive gear is needed to run the standby alternator.

 

Lightspeed recommends installing a dummy mag to act as an idler and hold the drive gear in place. They offer a magneto hole cover, but it’s just a flat plate. I have designed a combination idler/cover to solve this problem.

 

Some engineering thoughts: The accessory side of the drive gear has the bearing that takes all the loads. My idler/cover’s center post is smaller than inner diameter of the drive gear, so there is no contact. The drive gear and spline are straight-cut, so there should no force against the tip of the idler shaft. The length of the idler/cover’s center post is set to allow some fore-and-aft float in the drive gear. There should only be some incidental contact between the drive gear and the idler shaft. The idler/cover is anodized aluminum, which provides a fairly good wear surface, and it will be receiving splash lubrication.

 

I will be finalizing the design and sending this out to the machine shop in the next few days. As with any machining project, the price per unit comes down as quantity increases. Is anyone else interested in having these made up? The price will be around $48 each in quantity of 5, and $33 each if we make 10 of them.

 

Adam Molny

Legacy #151

85%, doing engine final assembly