What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RV7 Aft Battery Mount

decathlon737

Well Known Member
Benefactor
Search engine was not friendly to me, but I Can't be the only one to run across this. I opted for the aft battery mount because of YIO 390 engine and Hartzell prop Weight considerations. Garmin pitch servo interferes, what has the consensus done? Move battery even further aft or move servo aft and make a longer rod? TIA.
 
I don’t have the answer to your question, but would like to ask another question: Is there any way to maybe mount the battery in a different location or orientation that won’t interfere with the servo or elevator rod? I see that area to the left of the servo (where that piece of cardboard is) that may be a good spot to look at.
 
Last edited:
Yes possible, but that added rib on the other side was part of the Van's aft battery mount kit, so an added rib would be needed. I'm thinking moving the servo aft 4" would solve the situation and would only have to make another rod.
 
Reverse the servo orientation so the motor is on the other side?

Use a different battery(s) like the PC-625?

Modify the mount?

Carl
 
Personally, I would drill out the extra rib, turn the battery box sideways and remount the rib as needed. Might be able to get away leaving the rib where it is and just turning the top plate. The added rib would still support the battery but you would have some overhang. A small piece of aluminum from the overhang down to the j stringer and it would be plenty strong. You could probably make an adapter and fit a lithium battery on the tray as installed.
 
Last edited:
Same suggestion as Carl. Have the servo mounted on the other side of the bracket. The Rv-10 has it oriented that way around.

Regards Peter


D06BFA62-14FE-4D73-98C1-87FBD04AFC71.jpeg
 
Assuming you have run the W&B numbers, I would be cautious about moving E.W. C.G. too far aft. Passengers & bags ALL move C.G. aft.
 
Last edited:
Assuming you have run the W&B numbers, I would be cautious about moving E.W. C.G. too far aft. Passengers & bags ALL move C.G. aft.

With that big 390 motor and Hartzell prop (I’m assuming aluminum BA), he should have a pretty good fudge factor, especially if he uses something like an EarthX.
 
Search engine was not friendly to me, but I Can't be the only one to run across this. I opted for the aft battery mount because of YIO 390 engine and Hartzell prop Weight considerations. Garmin pitch servo interferes, what has the consensus done? Move battery even further aft or move servo aft and make a longer rod? TIA.

You don't mention that space firewall forward is an issue. In the case of an EarthX ETX680, which I mounted up front where my Odyssey PC680 used to reside, the W&B impact is negligible. Additionally, the battery can be accessed/disconnected by simply removing the top cowl (3 minutes, approximately), and electrical connections are short, entirely visible/accessible, and separated from critical flight components.
According to the manufacturer, thermal runaway would only happen if several problems happen, but the result would be "a lot of smoke for about 10 minutes". Personally, I'm more comfortable having the firewall between it and me.
Moving it "even further aft" would require crawling into the baggage compartment (not my 6'3" body's favorite exercise) in order to access it (installation, adjustment, disconnecting the ground cable for electrical maintenance), and add cost (even longer cables). And then there's connecting the Optimate charger/maintainer. Firewall forward, the pigtail is simply accessed through the oil door. In the rear, there would be additional complexity, in my view.
If space is not an issue up front, the mod you're discussing seems inadvisable.
 
Thanks for the replies. I decided to utilize the bracket that came with the Garmin install kit and just move it aft 4". I had to make a longer control rod but that just gave me an excuse to use my Smithy Lathe. :) The rod is 8" now instead of 4". Several Garmin generic install kits have 8" or longer control rods so I don't think the extra length will matter.


Reverse the servo orientation so the motor is on the other side?


I pondered doing this but required fabricating a 1 1/4" standoff bracket to move servo over. I chose the less labor way.:)


Personally, I would drill out the extra rib, turn the battery box sideways and remount the rib as needed.


I hated the thought of 21 unused (Holes) in the belly of my airplane.:eek:


Assuming you have run the W&B numbers, I would be cautious about moving E.W. C.G. too far aft. Passengers & bags ALL move C.G. aft.


Yes, I have run the numbers. Going to have to keep some weight aft with the YIO 390 Lycoming and a Hartzell BF prop. Included picture of finished mod.
 

Attachments

  • 20230115_140355.jpg
    20230115_140355.jpg
    388.9 KB · Views: 128
Whirlwind prop

I ditched the Hartzell for a 3 blade whirlwind saved 12 lbs on nose . I have 2 earthx mounted on fw
 
battery

I just got two F-729A webs to make a tray behind the baggage compartment for my battery. Right side.
I'll post photo when I get it in.
 
Last edited:
Thanks for the replies. I decided to utilize the bracket that came with the Garmin install kit and just move it aft 4". I had to make a longer control rod but that just gave me an excuse to use my Smithy Lathe. :) The rod is 8" now instead of 4". Several Garmin generic install kits have 8" or longer control rods so I don't think the extra length will matter.

Included picture of finished mod.

With the rod now 4" longer, consider if the rod failed at the servo end and dropped down to contact the skin. Can it continue to move with the elevator without snagging on ANYTINNG?... easy to test, just remove the threaded tube from the fitting and let it drop, and then move the elevator full motion and check for ANYTHING that would hinder it's safe travel.
rod.JPG
 
Many 7’s end up slightly tail heavy while empty limiting baggage capacity with low fuel. That’s with a standard 360 and a heavy CS prop. Even worse with a light prop.

I would keep the battery in the stock location and use an EarthX.

How much heavier is a 390?
 
I've been involved with several other 7 builds with light and heavy engine/ prop combinations before I came to this battery location for my application, for my application I have the choice of a heavy battery if needed, or a lighter version if required. Personally, I own and operate a high-end motorcycle shop. After seeing and repairing Lithium Battery run aways I choose to let the industry evolve a little more before I get trapped in an airplane with one on fire. I've seen $ 1000 and up batteries with management systems incorporated mal function and cause a mess. Admittedly most were customer wiring faults. YMMV

Many 7’s end up slightly tail heavy while empty limiting baggage capacity with low fuel. That’s with a standard 360 and a heavy CS prop. Even worse with a light prop.

I would keep the battery in the stock location and use an EarthX.


How much heavier is a 390?
 
That is a valid consideration, but also consider if rod end on your elevator linkage failed?? Where does a fella draw the line?

With the rod now 4" longer, consider if the rod failed at the servo end and dropped down to contact the skin. Can it continue to move with the elevator without snagging on ANYTINNG?... easy to test, just remove the threaded tube from the fitting and let it drop, and then move the elevator full motion and check for ANYTHING that would hinder it's safe travel.
View attachment 40750
 
Last edited:
Back
Top