The International Cessna^® 170 Association

I need part 0550100-7. This is an engine mount ground strap. Online pricing reveals jaw dropping prices for such a simple piece.

I would like to fabricate a replacement. Is there a specific metal type/alloy that would be preferred for this application? How about thickness? Or is it recommended to match original?


Thanks

Are you trying to match original for points or do you want something functional? Something functional is a braided ground strap with two ring terminals swaged on the end. Make the wire long enough to jump the rubber mount and be fastened under the bolt head and the nut at each end. Not much power has to be carried from the engine so a strap of about 1/2" would be sufficient IMO based on what I see daily on other aircraft. Put two of them on to double the the current to make you feel good but also to double the chances one of them actually is grounding the engine.

Actually quite a bit of power is required during engine start, the most ever demanded on the airplane. Almost any good automotive parts store or supply can be sourced for flat-braid ground straps. It’s about $1 per foot from Spruce: https://www.aircraftspruce.com/catalog/ ... ckkey=9021

GAHorn wrote:Actually quite a bit of power is required during engine start,

Woops, forgot about the starter.

And the generator.alternator.

Here is the bonding strap in question from an online search. Would this be aluminum? Stainless might hold up better, but it's not as good of a conductor. Braided strap sounds good. I just don't have the parts on hand. Rounding up some sheet metal sounds easier.

For what it’s worth F.A. Dodge sells bonding straps for larger Cessnas made from .025” 2024-T3. My preference is for the sheet metal style over a braided strap as the braided strap tends to wick oil. Miles described how he made his in this thread. Most suggest adding a jumper between the accessory case and the firewall.

There is a difference between a “grounding” strap and a “bonding” strap. The bonding straps provide continuous protection against electrolysis and provides static protection thru the dynofocal mount. A grounding strap provides an electrical pathway for current-return. In the OP the question is in regard to the aluminum strips which jump across the Lord engine mounts. You can make your own out of 2024 aluminum with sheet metal snips and a drill bit. (This is a classic example of how an “owner produced part” makes sense.)

The grounding strap which insures good electrical pathway for the engine connects the engine directly to the airframe via the firewall. This is the item for which I suggested the larger braid that must carry 600~Amps during engine start.

I never realized my engine wasn’t properly grounded until smoke came wafting up from the throttle cable or maybe it was the carb heat cable while I was starting the engine. The starter was always troublesome as it was having a hard time with only an incidental ground here and there. Everything works better with a real ground.