ROV Thruster Testing

So another ROV update, I did some tests of bilge pump motors as thrusters and got some interesting results

 

Results

Model	Direction	Voltage (V)	Current (I)	Power	Thrust (lb)	W/lb
1000gph w/ propeller	Forward	12.5	7A	87.5	1.25-1.5	58-70
	Reverse	12.5	7.5	93.75	1-1.25	75-93.75
500gph w/ propeller	Forward	13.0	5.0	65.0	0.5	130
	Reverse	13.0	4.5	58.5	0.75	78

These are some strange results that I need to reconcile before carrying forward, particularly the odd thrust value of the 500gph motor in forward.

Future plans involve testing nozzle shapes such as straight nozzles, nozzles with collimating fins (to reduce turbulent flow or increase laminar flow), and Kort rings. Anyone with expertise in this area feel free to chime in with comments.

A slightly less yellow submarine

So, because of the sheer expense of 6″ sch80 pipe and pipe fittings (read:  several hundred dollars for a few feet of pipe and 6 fittings!), there has been a redesign!

A yellow submarine

So besides the obvious song reference, I’m starting on a new long term project (as if I don’t have enough going on?). I’m going to be building a remotely operated vehicle (ROV) with a friend for fun and potential science. This has been on my list of things to do for ages, though prohibited mostly by cost. Being gainfully employed has its benefits (ie: money).

Stay tuned for more details, as the goal is to complete construction in time for summer 2011.

Key specs:

Rated depth: 100m
Rated pressure: 1.081 MPa or 156psi

Construction:
sch80 PVC pipe for electronics pods, 1″ CPVC pipe for frame, and aluminum for cross-bars

Power source:
Internal sealed lead acid batteries

Propulsion:
Modified bilge pumps

Instrumentation:
Pressure, temperature, compass, internal monitors (temperature, voltage, current consumption, [humidity/water sensor]). Video over IP camera

Control system:
Surface control computer
Onboard microcontroller with ethernet connectivity, control via tether.

Review of the GT Power A8 Battery Charger

In the realm of intelligent battery chargers, there are far too many choices. Prices range from about $50USD to some in the $300 range and come with a whole variety of features. The problem is that the new emerging market is for cheap products that don’t perform, or don’t have the durability and quality expected for a complex device.

Most new intelligent battery chargers can charge, discharge, and cycle Pb, NiCd, NiMH, Li-ion, LiPo, and more recently LiFePO4. These chargers feature control over charging/discharging current. Contrast this to your ‘dumb’ chargers that are essentially trickle charge wall warts that push in around 0.5C that can overcharge NiCd/NiMH, or slow LiPo balance trickle chargers that come with RC helis sometimes.

The GT Power A8 charger sells for about $80USD + S&H, I got mine from HobbyCity.com.

Alternator Motor Update

So my last post about an alternator to brushless motor conversion seemed to draw some interest, but people were asking some details so I drew up a quick diagram in inkscape last night.