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O2 bottle and Pitch Servo interference

unitink72

Well Known Member
I'm currently planning a mount for the Mountain High CFFC-048 oxygen bottle in my RV-10 tailcone. Trying to think of things that could interfere with my mounting location, and the worst offender I've seen is the pitch servo. Can anyone with a Dynon setup tell me how far the servo overhangs the bellcrank ribs?

Here is the area I'm talking about, and some relevant documentation. It looks to be around 3.5", but I can't tell how far up off the bottom that is. Could really use some pictures, my searches were in vain.

EZa0eCI.jpg


Relevant figures:
pPi9B9m.png


Rw8Ux4i.png
 
I'd suggest you re-think this. Most -10's can exceed the aft cg limit if you're not careful. Put the oxygen in the baggage area. If the baggage area is full, then the tank in the tailcone will most likely put you aft of cg limits. Some builders find a way to put the tank on top of the tunnel, between the front seats, just to keep the cg from going too far aft.
 
I would be more concerned about battery clearance and the ability to get back in the tailcone.

But I also agree with Bob. Personally, I would want the weight more forward. The CG is already problematic with four adults, this would just exaggerate the issue.

I have a portable unit that hangs off the back of the front seats. I'm about ready to mount it on the tunnel between the rear seats.
 
Another vote for not putting it in the tailcone for CG reasons. I have a portable bottle (Mountain High CFFC-022 with O2D2 units) and I put it between the rear seats on top of the tunnel. This allows me to easily remove the bottle when not required.
 
FP12072014A00043.jpg


Not to worry, the battery cables are secured well away from the tank. That was just an early wiring test. I weighed the idea of putting it in the baggage compartment but didn't want to compromise that area. Besides, the tank is extremely light compared to the AC unit and autopilot servos. Since I knew my panel is going to be relatively heavy with the G900X, not to mention AC compressor on the engine and metal constant speed prop, I'm not anticipating unusual CG problems (just the usual ones). Notice that I built a custom battery box for a 28V battery and even so, the relays are well away from the system. The servo on the other side was much closer, though it would have worked. It was the AC unit that was the conflict.

Design entry. Assembly entry. Filler and ground power installation under baggage floor.
 
Are there mounting restrictions in the way you can mount the bottles?

Would think there is plenty of room mounting vertical behind the rear seats.
 
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Another vote for not putting it in the tailcone for CG reasons.

Not sure why everybody is so against this. How many people have 2 PC680s in the tailcone? I plan on two batteries back there, but switching just one of them to EarthX is enough to offset the weight of the bottle. Almost two of these bottles in fact, ignoring mounting hardware, valves,tubing.

EXT680 4.1lbs
PC680 15.4lbs
CFFC-048 tank 6.4lbs (does not include mounting hardware)
 
Not sure why everybody is so against this. How many people have 2 PC680s in the tailcone? I plan on two batteries back there, but switching just one of them to EarthX is enough to offset the weight of the bottle. Almost two of these bottles in fact, ignoring mounting hardware, valves,tubing.

EXT680 4.1lbs
PC680 15.4lbs
CFFC-048 tank 6.4lbs (does not include mounting hardware)

You might want to rethink the battery scenario - EarthX specifically warns against running their LiFePO4 battery in combination with a lead-acid battery.
 
Not sure why everybody is so against this. How many people have 2 PC680s in the tailcone? I plan on two batteries back there, but switching just one of them to EarthX is enough to offset the weight of the bottle. Almost two of these bottles in fact, ignoring mounting hardware, valves,tubing.

EXT680 4.1lbs
PC680 15.4lbs
CFFC-048 tank 6.4lbs (does not include mounting hardware)

"So against" is pretty strong. I think what people, including myself, are saying, is that sooner or later you are likely to have a loading situation where the weight is within limits, but the cg is too far aft. Every pound you move forward now will lessen that problem. But the choice is yours. And, of course, if you have more weight forward than average (heavy prop, compressor, heavy pilot?) then you may have no cg problem at all. But that's not typical.
 
Simpler approach

The Mountain High bottle (AL682) comes with a nice carry pouch and tie down straps. I cut the straps such that I had two crisscross straps (using the four strap that came with it) that hold down the bottle in the pouch on top of the tunnel between the front and rear seats. The four strap ends go under existing tunnel screws.

Simple, easy to reach behind and turn on from the pilot's seat, easy to get in and out for refill and provides an arm rest for the rear passengers. I used just half of this bottle for an extended trip out west over the mountains.

Side note - five of us at the airpark went in on a O2 refill set up. Five bottles in a daisy chain so the lowest bottle is used first. The last four refills cost me a total of $40 (the price to exchange an empty for a full bottle at the local supplier).

Carl
 
SNII
How many people have 2 PC680s in the tailcone? I plan on two batteries back there... SNIP

Sorry for the drift off the subject, but you will find two PC-625 batteries fit better than two PC-680, provide more CCA and Amp-hrs, and weigh a little less.

Carl
 
You might want to rethink the battery scenario - EarthX specifically warns against running their LiFePO4 battery in combination with a lead-acid battery.

Good to know. In my case if I do use a mix of battery types, they will be on seperate electrical systems anyway. The manual crosstie will connect them only in the event of a failure.
 
"So against" is pretty strong. I think what people, including myself, are saying, is that sooner or later you are likely to have a loading situation where the weight is within limits, but the cg is too far aft. Every pound you move forward now will lessen that problem.

Poor choice of words, my apologies.
The CG issue is not lost on me. What I'd really like to have is my o2 tank and one earthX battery in the tailcone, then another battery in the cabin close to the firewall. I don't like the idea of having it forward of the firewall, or having a lithium battery in the passenger compartment. However I've done zero research to see if this is possible.
 
Are there mounting restrictions in the way you can mount the bottles?

Would think there is plenty of room mounting vertical behind the rear seats.

It's been a while since I looked at the supplied mounting hardware but the accompanying sheet recommended the horizontal, fore-aft orientation. The supplied mounts are not designed to cushion against loads in other orientations and might rupture the bottle in an impact. I think for normal operations, even including a hard landing, it won't be a problem but in a crash I'd like to reduce the likelihood of a ruptured bottle. Note also, that mine is a composite bottle. In my -6A I have a portable aluminum bottle sometimes, strapped to the rear of the flap motor housing.
 
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