In The Tank

While certainly speaking to my lack of posting over the last few months, what I'm talking about is a quick snapshot of the new ballast tank actuating mechanism I've worked on over the last few months. Really, not worked on is more like it; a few several day spurts of concentration followed by prolonged inactivity.

Below is the general layout of the new system. The Lexan tube is new, purchased from Small Parts, Inc. They carry short lengths of 3" OD. The stock D&E Propel tank was modified with a new barbed fitting for the gas hose and cleaned and painted. The ballast tank is elongated by 3/4" to add reserve bouyancy, which has always been marginal in my LA. The pass-through tube is of slightly larger diameter to allow more room for the wires. It is glued in place to eliminate leaks and o-rings. The servo is now mounted over the battery in the forward compartment and drives the linkage via a rotary seal.

The brass control shaft passes to a bearing in the back bulkhead for stability. The servo, with metal gears, turns the shaft which rotates the control arms to either vent the tank or hit the Propel blow valve. The vent valve for the tank is not shown but was machined down from a stock Schrader valve. It is screwed in upside down so the arm pushes the pin up and opens the vent -- just like letting the air out of a tire.

As you can probably tell, the mounting tab for the aft bulkhed interfered with the rotation of the arms. After much deliberation it was decided to remove the tab and go with three screws to hold the aft bulkhead. They are basically just to hold everything in place and it shouldn't cause any problems.

Installing the blow valve and arm are the last steps before final assembly. Then it's off to the pond to test things out. Once again, little of this would be possible if not for the kind assistance and expert advice of Gail Phillips. The basic design is modified from his original work.