5/16" bolt through 3/4" angle

I decided to install one of those piper-style sockets for ground power:



My first thought is to attach it to the bottom of my -7, near the firewall, so it's not too visible, but still a short wire run to the battery. I'd like to attach at least one of the bolts to something rigid for extra strength, but the best I can find are the 3/4" support angles in the footwell area. The bolt holes on this socket are 5/16" so that seems not do-able edge distance-wise. Any tips, or should I just forget the angle and put both holes through the skin with an appropriate doubler?

Just a thought here, but if you’re going to put it that far forward anyway, why couldn’t you mount it somewhere just fwd of the firewall and put a door in the cowl to access it like a second oil door?

Draker said:

I decided to install one of those piper-style sockets for ground power:

Click to expand...

Do you intend to crank the engine from an external GPU/Cart?

If not, there are many smaller alternatives that will carry ~30A needed to run all of the avionics while sitting in the hangar. EC3 type from the RC world will support 60A continuous.

Desert Rat said:

Just a thought here, but if you’re going to put it that far forward anyway, why couldn’t you mount it somewhere just fwd of the firewall and put a door in the cowl to access it like a second oil door?

Click to expand...

Definitely not married to the location inside the cabin.

I tried to come up with some sensible way to mount it forward of the firewall. The leading candidate was to attach it high so I could access it through the actual oil door. I'd need to run a separate ground wire to the battery in this case, which is probably not that big a deal. Maybe attach it to a big angle and then secure the angle to the engine mount with adel clamps?

I prefer not to mount it directly to the fiberglas cowl, even to the bottom of it. That would over-complicate removing the lower cowl.

bjdecker said:

Do you intend to crank the engine from an external GPU/Cart?

If not, there are many smaller alternatives that will carry ~30A needed to run all of the avionics while sitting in the hangar. EC3 type from the RC world will support 60A continuous.

Click to expand...

Supporting cranking is less important--it's a nice-to-have. I already went through all the trouble to 1. mount a third solenoid to switch ground power on/off and 2. modify the piper socket so I figured might as well finish the job off. The socket is a little heavy but not the end of the world.

EDIT: Also, there are tons of threads on jump-plug-yes-or-no, assume I’ve read them

I wouldn't want to mount it directly to the cowl either. It's an annoyance to have to unhook landing lights from a lower cowl, and thats just a simple connector. A GPU plug would be a next level annoyance.

What I was thinking was more like what you see on quite a few certified airplanes; The plug lives on a hard mount or bracket, and there is a door on the cowl to access it.

Having said that, I've thought about this quite a bit, and decided that I'm personally not going to be putting a plug anywhere in front of the wing for GPU starts. It's not a bad location on a Cessna because you're not pinned up against the wing, but on an RV you've got what, maybe 4'? I don't want to force some poor line guy to get in that tiny space between the wing and the whirling blades of death.

Wife has the same Piper plug bolted to the motor mount accessible through the oil check door on her RV-9A.

She uses it occasionally for panel work and starting when the battery is low.

Carr

I wouldn’t mount that ugly thing to the outside of the plane.. I understand the desire for an easy to find plug, so even away from home, chances are good to find someone with a Piper plug.. How about making a flush door, and make a Z bracket stand-off to hold that socket? This way it’s not visible and in the airstream?

On my RV-8, mine is mounted under the belly behind the rear seat - directly by the aft mounted battery. Probably not applicable to a -7....however, if you’re ever going to use it for a jump start, I’d put it far enough away from the “spinny thing” up front that an average mortal would be comfortable disconnecting the cable after the start. If you DON’T plan to ever use it for a jump, then you can use a much smaller plug.....

Oh - and I just used a nice doubler for the belly skin, and didn’t try to connect it to angles....been that way for 2,000 hours a and over fifteen years now.

Thanks—the insight to not put it too close to the spinny-thinggy is valuable and something I didn’t think of.

Just because it has a 5/16 hole doesn't mean you have to use a 5/16 bolt, a #10 would be more than adequate with a couple of washers, use a bushing if you want to get really fancy but not really nec..