Really Interested in a Pony - What size? How to mount? Other questions!

[raftingtigger]

MrChen,

Just remember this is an Oh, @$@%... reserve. If you use it for anything other than;
1. Training -- and remember to do this occasionally
2. True equipment failure
3. Assisting another diver with their problem,

then you need to take the rest of the diving day off and rethink your procedures, skills, situational awareness, or if #3 your choice of buddy..

 

[uncfnp]

And remember to turn the sensitivity down on your octo (old primary) or get it detuned so it will be less likely to have a free flow when not use.

 

[MrChen]

Thanks guys. I've been chatting with TC by email and the one thing I took from our conversation was that my pony is another emergency device and should be treated as such. It doesn't give me the pass to change my diving habits or become less safety conscience. I'll post a pic once I have it setup.

 

[raftingtigger]

Thanks guys. I've been chatting with TC by email and the one thing I took from our conversation was that my pony is another emergency device and should be treated as such. It doesn't give me the pass to change my diving habits or become less safety conscience. I'll post a pic once I have it setup.

Double like!

 

[drbill]

I dive solo 95% of the time. If I'm planning a dive deeper than about 40 fsw, I usually carry my 19 cu ft pony. It is mounted like the 13 cu ft pony in the images below. I prefer my pony mounted on my back out of the way so it doesn't accidentally stir up sediment since I am a videographer. I put a small amount of weight on the opposite side of my belt to counter-balance the pony.

If you go this route make sure the pony valve is higher than the bottom of the main tank and be careful when exiting the water that you don't knock the valve. I prefer my pony upside down because it is easier for me to reach the valve.

 

[MrChen]

You brought up another point that I wanted to ask a question about. Once I start diving with the pony, I imagine I'm going to have to drop some weight. But then what happens if I lose all my air from my main tank, it's now going to become positively buoyant. Then I start breathing from the pony and it starts to become buoyant, but because I dropped weight to compensate for the pony, won't I now be too buoyant as the pony gets lower on air?

How much weight, if any, should I drop?

Also, with the pony on a sling, do I need to compensate by adding more weight on the other side?

 

[raftingtigger]

You brought up another point that I wanted to ask a question about. Once I start diving with the pony, I imagine I'm going to have to drop some weight. But then what happens if I lose all my air from my main tank, it's now going to become positively buoyant. Then I start breathing from the pony and it starts to become buoyant, but because I dropped weight to compensate for the pony, won't I now be too buoyant as the pony gets lower on air?

How much weight, if any, should I drop?

Also, with the pony on a sling, do I need to compensate by adding more weight on the other side?

Several ways to go about this.

1. Keep your weight the same. The pony when full is barely negative. When empty who cares - you should be surfacing anyway. The slight positive (if any) of an emply and RIGGED pony should not cause a rockship to the surface. The slightly extra negative on one side is hardly noticeable - at least I have never noticed it at all. I will also dive a AL80 left sidemount with a regular BM tank (independent doubles) and have not found it necessary to adjust my weighting.

2. Treat the full and rigged pony as a weight and remove the equivalent lead from that side. This works really well 99.99% of the time (since you aren't breathing from the pony), but if you forget to replace the lead when you don't use the pony (of forget to carry it) you are now 2.5-3# light on that side. Personally I would prefer a hair heavy to light. Not an issue with most of the dive, but the SS gets more challenging.

I would not ADD weight to the non-pony side as that just overweights you. The pony when full and rigged is negatively buoyant, so adding weight to the opposite side is the wrong approach.

 

[MrChen]

I'm excited. I picked up my 19cu pony yesterday. The LDS owner installed a DIY sling for $12. I purchased a 6 inch hose with hog SPG. I purchased a Hog 2nd stage and set it as my primary reg. Moved my previous primary reg to my necklace. I moved my octo reg to my pony. I got a Hog BP2 first stage for $85 from DRIS. I'm still waiting on the first stage to arrive, it's estimated delivery with USPS is today.

I'll post some pictures once I get it assembled.

 

[djtimmy77]

Too bad I didn't check this thread earlier. I would have let you borrow my slung 19 to try out and see if you like it. That being said, you should like your rig just fine!

 

[Rand]

You brought up another point that I wanted to ask a question about. Once I start diving with the pony, I imagine I'm going to have to drop some weight. But then what happens if I lose all my air from my main tank, it's now going to become positively buoyant. Then I start breathing from the pony and it starts to become buoyant, but because I dropped weight to compensate for the pony, won't I now be too buoyant as the pony gets lower on air?

How much weight, if any, should I drop?

Also, with the pony on a sling, do I need to compensate by adding more weight on the other side?

You should be weighted properly to account for the likely positive buoyancy your back gas cylinder will gain as the tank empties. That doesn't change because of the pony. I would not make any weighting changes if you are slinging a bottle.

Check out this cylinder specification chart. You will see for most cylinders, especially for the AL19 that you have, the buoyancy swing from full to empty is pretty much negligible, at least with aluminum tanks, which is what you want for stage/deco/pony bottles. Also, consider that these figures are the buoyancy of the tank with valve. It doesn't take into account the weight of the reg and any of the hardware used to mount the bottle. So, in the end, those pieces of gear may offset the positive buoyancy of any empty pony anyway.

For such a small tank as an AL19, you won't need to shift any weight. I've had AL40s slung, and I don't change my weighting for that tank either. The main thing you need to do is get it set up and adjusted, and then get in the water and practice with it. Make sure you didn't trap the pony reg hose when you slung it and it can be deployed easily (this should be part of your pre-dive check every time anyways). Practice re-stowing the pony hose. Know which way to turn the valve to get it on in a hurry. Practice taking the bottle off and clipping it back on in case you did choose to pass it or had to remove it because it got hung up on something. Get used to doing a flow check on the bottle (pressurizing it and turning it off), and periodically check the gauge on it. If you see the HP gauge hose is slack or the gauge is reading zero, flow check it again. Sometimes your 2nd stage on a slung bottle will bump something and purge the gas. You want to keep it pressurized.

This video shows how the bottle should look when slung and how the hose is stowed and deployed. It is assuming this is a deco bottle, so some of the steps don't really apply in your use of it. This video shows bottle passing and a bunch of other stuff. Keep in mind this bottle pass is a planned event, not indicative of what it might look like if you were giving a bottle to someone who just had a catastrophic gas failure. Again, not all the stuff in these two videos will apply to you, but some more resources to watch and learn if you think it might help.