Troubleshooting Tips (Some Apply to ROVs with the Hand-Wired Control Box)

Troubleshooting Tips (Some Apply to ROVs with the Hand-Wired Control Box)
Posted by Rich at 2010-07-31 03:46:48

Troubleshooting Your SeaPerch ROV

(Some Tips Apply Only to the Traditional, Hand-Wired Control Box)

Things to Try Before Re-Wiring or Changing Parts

Solving Directional Control Problems:

Sometimes SeaPerch controls are found to be reversed, such as the port switch controlling the starboard thruster.  Often one or more thrusters operate in the reverse direction from that intended.  Before resorting to re-wiring anything, consider the following simple solutions.

n  Port and Starboard Switches Operate the Wrong Horizontal Thrutsers.  Simply swap the horizontal thrusters by loosening their mounts and trading them (port for starboard) or swap the switch positions in the control box. 

n  A Horizontal Thruster Runs in Opposite the Direction Intended.  Loosen that thruster’s switch, rotate it 180 degrees, and re-tighten it.  

n  The Vertical Thruster Runs in Opposite the Direction Intended.  Swap the mounting hole positions of the two pushbutton switches (or, if a toggle switch is used instead, rotate it 180 degrees in its mounting hole), or re-mount the thruster upside down in the thruster mount (but be careful that it will not interfere with any payload being handled by the ROV). 

n  The ROV Always Seems to Turn More Easily to the Left or Right.  Check to see that the tether cable is mounted on the ROV in the center of the pipe on the rear of the vehicle, and that the crossed tie wraps are in place to keep the vehicle-end of the tether cable pointing straight back from the ROV.  Also, check to see that the horizontal thrusters are both running at about the same speed.  If a thruster is not working or is running slow, it can easily be replaced with a spare by cutting the thruster’s wire pair about 4” from the thruster and splicing on a good spare thruster.

n  The ROV is Very Slow in Diving.  First check to see if any air is trapped within the pipes.  Then check the ballast to confirm that none of it has fallen off.  Re-ballast for neutral buoyancy if necessary. 

n  The ROV is Very Slow in Surfacing.  Check to see if the payload being handled by the ROV is too heavy.  Also, make sure that the floats have not taken on water.  Note that a significant problem can occur when using foam-type floats.  If such an ROV works fine in shallow water but does not surface easily from deep water, the problem is likely caused by the foam floats compressing due to increased water pressure at the deep depth.  This results in less water displacement by the floats, thus less buoyancy. Using less ballast can help.

Solving Thruster Operational Problems:

n  Initial Operational Problems.  Sometimes SeaPerch thrusters do not work properly due to problems in the waterproofing process.  Frequently, a thruster seems to be frozen when first energized after the potting process, and then it works fine after simply being spun a few revolutions by hand (or using pliers if the shaft won’t turn by hand), possibly freeing up the shaft from being stuck on the wax seal or due to foreign material in the seal area.  Always try hand-spinning the thruster before replacing it.

n  Wax Intrusion Problems.  If wax leaks into a motor, it usually does not work at all, but sometimes such motors work intermittently, possibly with some wax on brushes or other internal parts.  Turning the thruster shaft back and forth while repeatedly energizing the thruster for about one second at a time can sometimes get a thruster working.

n  Failed Thrusters.  If a thruster simply won’t run, or runs slowly, it should be replaced with a spare thruster.  Always have a few spare thrusters (and plenty of fuses) available to support in-water ROV operations.

n  Thrusters that Don’t Run After Post-Operation Storage.  If the thrusters are not rinsed and protected properly after in-water use, they may not operate when tried some time later.  This might be due to rust or corrosion in the shaft seal area or water leaks into the motor.  Later cleaning and lubrication of the thrusters might bring them back to service, but the best way to avoid this problem is to always follow the cleaning recommendations after in-water ROV use (a fresh water rinse and application of a WD-40 type lubrication and water displacement product to the thruster shafts before storage).

 

Note:  If you modify the ROV's wiring or the placement or orientation of switches within the control box to achieve proper operation, you should put a note inside the control box to leave a record of the change or non-standard configuration, to minimize confusion should you or others need to repair or modify the ROV in the future.

[ From the SeaPerch ROV Construction Manual, Ver. 2010-01, July 2010 ]

Re: parts
Posted by Joel Gambill at 2012-05-13 13:41:43

Rich wrote on 2010-07-31 03:46:48:

Troubleshooting Your SeaPerch ROV

(Some Tips Apply Only to the Traditional, Hand-Wired Control Box)

Things to Try Before Re-Wiring or Changing Parts

Solving Directional Control Problems:

Sometimes SeaPerch controls are found to be reversed, such as the port switch controlling the starboard thruster.  Often one or more thrusters operate in the reverse direction from that intended.  Before resorting to re-wiring anything, consider the following simple solutions.

n  Port and Starboard Switches Operate the Wrong Horizontal Thrutsers.  Simply swap the horizontal thrusters by loosening their mounts and trading them (port for starboard) or swap the switch positions in the control box. 

n  A Horizontal Thruster Runs in Opposite the Direction Intended.  Loosen that thruster’s switch, rotate it 180 degrees, and re-tighten it.  

n  The Vertical Thruster Runs in Opposite the Direction Intended.  Swap the mounting hole positions of the two pushbutton switches (or, if a toggle switch is used instead, rotate it 180 degrees in its mounting hole), or re-mount the thruster upside down in the thruster mount (but be careful that it will not interfere with any payload being handled by the ROV). 

n  The ROV Always Seems to Turn More Easily to the Left or Right.  Check to see that the tether cable is mounted on the ROV in the center of the pipe on the rear of the vehicle, and that the crossed tie wraps are in place to keep the vehicle-end of the tether cable pointing straight back from the ROV.  Also, check to see that the horizontal thrusters are both running at about the same speed.  If a thruster is not working or is running slow, it can easily be replaced with a spare by cutting the thruster’s wire pair about 4” from the thruster and splicing on a good spare thruster.

n  The ROV is Very Slow in Diving.  First check to see if any air is trapped within the pipes.  Then check the ballast to confirm that none of it has fallen off.  Re-ballast for neutral buoyancy if necessary. 

n  The ROV is Very Slow in Surfacing.  Check to see if the payload being handled by the ROV is too heavy.  Also, make sure that the floats have not taken on water.  Note that a significant problem can occur when using foam-type floats.  If such an ROV works fine in shallow water but does not surface easily from deep water, the problem is likely caused by the foam floats compressing due to increased water pressure at the deep depth.  This results in less water displacement by the floats, thus less buoyancy. Using less ballast can help.

Solving Thruster Operational Problems:

n  Initial Operational Problems.  Sometimes SeaPerch thrusters do not work properly due to problems in the waterproofing process.  Frequently, a thruster seems to be frozen when first energized after the potting process, and then it works fine after simply being spun a few revolutions by hand (or using pliers if the shaft won’t turn by hand), possibly freeing up the shaft from being stuck on the wax seal or due to foreign material in the seal area.  Always try hand-spinning the thruster before replacing it.

n  Wax Intrusion Problems.  If wax leaks into a motor, it usually does not work at all, but sometimes such motors work intermittently, possibly with some wax on brushes or other internal parts.  Turning the thruster shaft back and forth while repeatedly energizing the thruster for about one second at a time can sometimes get a thruster working.

n  Failed Thrusters.  If a thruster simply won’t run, or runs slowly, it should be replaced with a spare thruster.  Always have a few spare thrusters (and plenty of fuses) available to support in-water ROV operations.

n  Thrusters that Don’t Run After Post-Operation Storage.  If the thrusters are not rinsed and protected properly after in-water use, they may not operate when tried some time later.  This might be due to rust or corrosion in the shaft seal area or water leaks into the motor.  Later cleaning and lubrication of the thrusters might bring them back to service, but the best way to avoid this problem is to always follow the cleaning recommendations after in-water ROV use (a fresh water rinse and application of a WD-40 type lubrication and water displacement product to the thruster shafts before storage).

 

Note:  If you modify the ROV's wiring or the placement or orientation of switches within the control box to achieve proper operation, you should put a note inside the control box to leave a record of the change or non-standard configuration, to minimize confusion should you or others need to repair or modify the ROV in the future.

[ From the SeaPerch ROV Construction Manual, Ver. 2010-01, July 2010 ]



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