braided grounding strap isolation

[dbaflyer]

I am working to put one of these from my engine to firewall FOT stud. Does the braided strap have to be isolated from touching anything between the two mounting points? My path from engine mount point to FOT is somewhat difficult from having a completely clear path. Is it OK to touch at least the engine mount?

[DRMA]

Shouldn't be a problem so long as the grounds are solid at each end. So long as there is no potential (voltage) between the points contacted (e.g. no resistance between them along the ground strap) there should be no issues. In fact, on the RV-10 Van's recommended ground strap connection points are between the engine and tabs provided on the engine mount for that purpose.

[RV7A Flyer]

Just be aware of the potential for the strap to abrade whatever it's touching. I'd rather see a clear path with plenty of room around it. The engine moves a lot on startup/shutdown, plus the vibrations during normal operations.

You don't want to set up a situation where it will damage something like the mount.

[Carl Froehlich]

There is no requirement to use a braided ground strap, and some reasons not to.

I use the same gauge welding cable (#2) to ground the engine that runs power to the starter motor. I ground the engine on the nice ground lug on the back of the starter - that is what needs the good ground in the first place.

Carl

[YvesCH]

I also used a #2 welding cable to the starter lug. And another one to the vacuum studs..

[rightrudder]

Originally Posted by Carl Froehlich

There is no requirement to use a braided ground strap, and some reasons not to.

I use the same gauge welding cable (#2) to ground the engine that runs power to the starter motor. I ground the engine on the nice ground lug on the back of the starter - that is what needs the good ground in the first place.

Carl

Mine is similar, from the vacuum pump pad to my grounding point on the firewall. I used a longish cable in a U-shape (plan view) to allow for engine twist.

[lr172]

There is a reason that ground straps exist. The connection from the frame to the engine is a high vibration connection and any cable connecting the two needs to have a large quantity of small gauge copper strands. This is what a grounding strap is. A welding cable is similar and good for this application. However, regular cables are not appropriate for this application and there is a decent possibility of the individual strands breaking and reducing the ampacity of the cable.

A ground strap does not need to be isolated from anything other than exposed positive connections and, as mentioned, anything that can cause fraying of the strap.

Larry

[GalinHdz]

Also, grounding straps are flat with their wires weaved in many different angles to minimize signals being induced into the ground path. But this "normally" is not an issue in metal airplanes.

[V111Pilot]

Best practice would be to take a piece of rubber tubing and slit it and then zip tie it around the engine mount where the ground strap touches to prevent any degradation of the ground strap...

[jimgreen]

Talking to a mechanic recently, he recommended two ground straps for redundancy. Is anyone else doing that?