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Introduction

You should have a good understanding of how acrylic cement works at this point. We are now going to introduce the use of epoxy. The epoxy acts as a barrier to the water and allows wires to "pass through" the endcaps.

  1. There are 8 acrylic parts needed to make the battery tube endcaps. Start by removing the paper backing.
    • There are 8 acrylic parts needed to make the battery tube endcaps.

    • Start by removing the paper backing.

  2. To keep the parts aligned we are going to use the threaded rod on the motors. Take one of them out and remove the hardware (nuts and washers) from the threaded rod. Set these aside for later. Place the first piece onto the threaded rod as shown.
    • To keep the parts aligned we are going to use the threaded rod on the motors. Take one of them out and remove the hardware (nuts and washers) from the threaded rod. Set these aside for later.

    • Place the first piece onto the threaded rod as shown.

  3. When working with acrylic cement it is recommended that you wear gloves, safety glasses, and work in a ventilated area. Place the second piece, one of the thinner disks, onto the first as shown. Apply acrylic cement.
    • When working with acrylic cement it is recommended that you wear gloves, safety glasses, and work in a ventilated area.

    • Place the second piece, one of the thinner disks, onto the first as shown.

    • Apply acrylic cement.

    • Place the third piece, the small thick disc, and cement it in place as shown.

    • Place the fourth piece, another thin disk, and cement it in place as shown.

  4. Use a second motor to repeat the process while the first endcap is curing.
    • Use a second motor to repeat the process while the first endcap is curing.

    • After the acrylic cement has cured (about 10 minutes) you can remove them from the motors.

    • Place the endcaps and the motors aside, as we won't need them again for a while.

  5. Next we will modify the two syringes. This process is identical for both syringes. Remove the plungers from both syringes -- we're going to cut the syringe tubes in two locations.
    • Next we will modify the two syringes. This process is identical for both syringes.

    • Remove the plungers from both syringes -- we're going to cut the syringe tubes in two locations.

    • Make sure to set aside the plungers in a safe place as they're needed to seal the electronics tube.

  6. Cut the syringe tubes with a thin hacksaw blade above the plunger stopping point, as shown. Be careful not to cut this too short. The plunger should stop where it usually does when inserted. Then cut at the 0.16 mL mark, as shown.
    • Cut the syringe tubes with a thin hacksaw blade above the plunger stopping point, as shown.

    • Be careful not to cut this too short. The plunger should stop where it usually does when inserted.

    • Then cut at the 0.16 mL mark, as shown.

  7. Use medium grit sandpaper to smooth the edges and square them up.
    • Use medium grit sandpaper to smooth the edges and square them up.

  8. Using a razor, carefully debur the inside edge of the syringe section, but be careful not to make any large gashes along the inside surface! Make sure to be careful with the razor as it is sharp. Remove any grit or dust left inside.
    • Using a razor, carefully debur the inside edge of the syringe section, but be careful not to make any large gashes along the inside surface!

    • Make sure to be careful with the razor as it is sharp.

    • Remove any grit or dust left inside.

    • You can use compressed air or a Q-tip wetted with water or alcohol to clean the inside of the syringe section.

    • You should now have two syringe sections.

  9. We're going to assemble the endcaps for the main tube in the next steps. There are two endcaps (port and starboard) and they are not identical.
    • We're going to assemble the endcaps for the main tube in the next steps. There are two endcaps (port and starboard) and they are not identical.

    • The main tube endcaps are the most important part of the OpenROV as they keep your electronics dry.

    • Pay close attention to the instructions. There are 4, 1.5mm flanges, 2 are clear and 2 are white - make sure you know which one you need.

  10. Keep the parts in the following steps clean. Remove the backing right before cementing them together.
    • Keep the parts in the following steps clean. Remove the backing right before cementing them together.

    • If they are dirty or dusty clean them with a soft cloth.

  11. For these directions we have outlined each part with a white ring. We're going to begin with the 3mm thick disc. This one is slightly larger in diameter than the similar-shaped 6mm thick disc.
    • For these directions we have outlined each part with a white ring.

    • We're going to begin with the 3mm thick disc. This one is slightly larger in diameter than the similar-shaped 6mm thick disc.

  12. Next insert the cut syringe face down into the center hole as shown.
    • Next insert the cut syringe face down into the center hole as shown.

  13. Next, stack the 6mm thick disc on top. Make sure to line up the holes as shown.
    • Next, stack the 6mm thick disc on top. Make sure to line up the holes as shown.

  14. Pick up the pair and turn it over. Notice that the syringe is flush with the surface of the 3mm circle. Try to maintain this throughout the next few steps.
    • Pick up the pair and turn it over.

    • Notice that the syringe is flush with the surface of the 3mm circle. Try to maintain this throughout the next few steps.

  15. The best method of cementing the endcap parts together is as follows: While holding one side, place the needle of the applicator between the two surfaces to be cemented. Add a liberal amount of cement. The goal is to have cement completely filling the gap between the surfaces. Any excess or spills will evaporate quickly or can be wiped away.
    • The best method of cementing the endcap parts together is as follows:

    • While holding one side, place the needle of the applicator between the two surfaces to be cemented.

    • Add a liberal amount of cement. The goal is to have cement completely filling the gap between the surfaces. Any excess or spills will evaporate quickly or can be wiped away.

    • Apply slight pressure with both hands while the cement cures.

  16. Add acrylic cement around the entire edge of the newly cemented parts to ensure that they are completely joined.
    • Add acrylic cement around the entire edge of the newly cemented parts to ensure that they are completely joined.

    • Clean any excess off with a paper towel or cloth.

  17. Make sure that the syringe is still flush with the surface of the 3mm disc.
    • Make sure that the syringe is still flush with the surface of the 3mm disc.

  18. Add some acrylic cement to the gap between the discs and the syringe.
    • Add some acrylic cement to the gap between the discs and the syringe.

  19. Add the thin 1.5mm flange with the three circles to the top of the 6mm thick disc. Make sure to orient it exactly as shown. Keep the two circles concentric as indicated. Cement this new part to the other discs using the same procedure as before.
    • Add the thin 1.5mm flange with the three circles to the top of the 6mm thick disc. Make sure to orient it exactly as shown.

    • Keep the two circles concentric as indicated.

    • Cement this new part to the other discs using the same procedure as before.

  20. Next, add the 6mm flange to the top of the piece you just added. Keep them lined up as shown. Again cement these together using the same technique as before.
    • Next, add the 6mm flange to the top of the piece you just added.

    • Keep them lined up as shown.

    • Again cement these together using the same technique as before.

  21. Now add the 1.5mm WHITE flange to the top as shown.  There is only the center hole. Make sure that they remain concentric. Cement them completely using the same technique as before.
    • Now add the 1.5mm WHITE flange to the top as shown. There is only the center hole.

    • Make sure that they remain concentric.

    • Cement them completely using the same technique as before.

    • Set this completed endcap aside to cure.

  22. Next start the second endcap with the 3mm disc as before.
    • Next start the second endcap with the 3mm disc as before.

  23. Add the syringe as shown.
    • Add the syringe as shown.

  24. Add the 6mm disc to the top as before.
    • Add the 6mm disc to the top as before.

    • Keep the holes lined up just as before.

  25. Cement these parts just as before. Keep in mind to have complete coverage with the cement.
    • Cement these parts just as before.

    • Keep in mind to have complete coverage with the cement.

    • Keep the syringe flush with the surface of the 3mm disc.

  26. Add the thin 1.5mm flange with the three circles exactly as shown. The orientation is very important. Cement them together using the same technique as before.
    • Add the thin 1.5mm flange with the three circles exactly as shown. The orientation is very important.

    • Cement them together using the same technique as before.

    • Be careful to keep the circles concentric and lined up while cementing.

  27. Add the 6mm flange to the top. Line up the holes as shown.
    • Add the 6mm flange to the top.

    • Line up the holes as shown.

    • Cement using the same technique as before.

    • Stop here. Do not add the white flange.

  28. At this point you should have two completed endcaps.
    • At this point you should have two completed endcaps.

    • Make sure yours look just as the ones in the picture.

  29. Next place the syringe plunger into the endcap. Cut between the cut end of the syringe but below the plane of the endcap as shown. Remove the plunger and set aside in a clean place for later.
    • Next place the syringe plunger into the endcap.

    • Cut between the cut end of the syringe but below the plane of the endcap as shown.

    • Remove the plunger and set aside in a clean place for later.

    • Keep both parts of the syringe plunger.

    • Do this for both syringe/plunger combos.

  30. Now we'll make sure the endcap fits correctly in the Main Tube. Bevel the inner edges of the main tube using a medium grit sandpaper so that the o-ring will fit in the tube without getting damaged by the sharpness of the tube's inner edge.
    • Now we'll make sure the endcap fits correctly in the Main Tube.

    • Bevel the inner edges of the main tube using a medium grit sandpaper so that the o-ring will fit in the tube without getting damaged by the sharpness of the tube's inner edge.

    • Wipe off all the dust left over from the sanding process when done.

    • DO NOT SAND THE INNER SURFACE OF THE TUBE WHERE THE O-RING WILL BE. This part must be kept completely smooth; only chamfer the edge.

    • Make sure to do this for both ends.

  31. Place a #340 o-ring (the large size) in the grooves ("o-ring glands") of both endcaps. Since the o-ring will make a pretty tight fit with the main tube, it is recommended that a lubricant be used. We like to use a common lubricant called "MagicLube" which is available at many hardware stores.
    • Place a #340 o-ring (the large size) in the grooves ("o-ring glands") of both endcaps.

    • Since the o-ring will make a pretty tight fit with the main tube, it is recommended that a lubricant be used.

    • We like to use a common lubricant called "MagicLube" which is available at many hardware stores.

    • To apply the lubrication to the o-ring, squeeze a small amount of lubrication onto your finger and then move the o-ring through your fingers.

    • When using lubrication it is recommended that you wear gloves.

  32. Place the endcap into the main tube and inspect to make sure that at least a 1mm-thick band of the o-ring is pressed against the inside of the main tube. Rotate the tube to make sure the o-rig engages along the entire interior perimeter of the tube. VERY IMPORTANT: Because the tolerances of the pieces may vary slightly, it's possible that your endcap may not engage tightly enough with the main tube. (You can see an example of what this looks like in the second image).
    • Place the endcap into the main tube and inspect to make sure that at least a 1mm-thick band of the o-ring is pressed against the inside of the main tube. Rotate the tube to make sure the o-rig engages along the entire interior perimeter of the tube.

    • VERY IMPORTANT: Because the tolerances of the pieces may vary slightly, it's possible that your endcap may not engage tightly enough with the main tube. (You can see an example of what this looks like in the second image).

    • If the endcap doesn't fit well, the band of engaged o-ring will be very thin or may even disappear in spots. If this is the case or if you have any other issues please contact us.

    • If the endcap tends to pop off on its own, it means you need to chamfer the inner edge of the tube a little more.

  33. Remove the o-rings and put them in a safe, clean place until ready for use. A good way to remove the o-rings is to squeeze the o-ring so there's a gap and stick the discarded end of the plunger from the previous steps. [Thanks to Petter for this suggestion!]. Be careful not to damage the o-ring.
    • Remove the o-rings and put them in a safe, clean place until ready for use.

    • A good way to remove the o-rings is to squeeze the o-ring so there's a gap and stick the discarded end of the plunger from the previous steps. [Thanks to Petter for this suggestion!].

    • Be careful not to damage the o-ring.

  34. Pick up this endcap. This is the port endcap and the endcap through which the wire harness is potted.
    • Pick up this endcap. This is the port endcap and the endcap through which the wire harness is potted.

  35. Begin by separating the wires on pins 14-19 on the DB-25. Pins 14-17 are the IMU wires: power positive (red stripe), data SCL (green stripe), data SCA (white stripe), power negative (black stripe). Pins 18-19 are the tether wires (solid yellow).
    • Begin by separating the wires on pins 14-19 on the DB-25.

    • Pins 14-17 are the IMU wires: power positive (red stripe), data SCL (green stripe), data SCA (white stripe), power negative (black stripe).

    • Pins 18-19 are the tether wires (solid yellow).

    • Using your hands begin twisting the two tether wires at the base of the DB-25. Continue twisting to the end of the wires.

    • Be careful not to twist with too much force or by pulling the wires too hard. The wires may break from the connector if care is not taken.

    • Use the same technique for the IMU wires. Be sure to pair:

    • Power positive (red stripe) and data SCL (green stripe).

    • Power negative (black stripe) and data SCA (white stripe).

  36. The finished DB-25 connector should look like the photos to the left. For the rest of this guide the wires in the photos will not be twisted. Your wires should be twisted. For the rest of this guide the wires in the photos will not be twisted. Your wires should be twisted.
    • The finished DB-25 connector should look like the photos to the left.

    • For the rest of this guide the wires in the photos will not be twisted. Your wires should be twisted.

  37. You're now ready to add wiring to the port endcap. Thread the DB25 cable through the endcap as shown. Careful pulling wires through the hole. The edges of the acrylic can slowly strip off the insulation of the wires if scraped against it.
    • You're now ready to add wiring to the port endcap. Thread the DB25 cable through the endcap as shown.

    • Careful pulling wires through the hole. The edges of the acrylic can slowly strip off the insulation of the wires if scraped against it.

  38. Measure 17cm from the top surface of the endcap to the top of the DB-25 connector (it should be bent at 90 degrees) for this measurement. Double-check this measurement as will be made permanent in the next step. If it is too short you won't be able to plug it into the circuit board. If it's too long it could push on the other endcap. Keep it between 16.5cm and 17.5cm.
    • Measure 17cm from the top surface of the endcap to the top of the DB-25 connector (it should be bent at 90 degrees) for this measurement.

    • Double-check this measurement as will be made permanent in the next step. If it is too short you won't be able to plug it into the circuit board. If it's too long it could push on the other endcap. Keep it between 16.5cm and 17.5cm.

  39. The connector of the DB-25 should be facing away from the flat side of the endcap.
    • The connector of the DB-25 should be facing away from the flat side of the endcap.

  40. Put on some gloves and prepare the acrylic cement. Keep the wire harness from moving too much from the 17 cm measurement. Make sure the bundle lies flat on the outside surface of the endcap. Use your thumb to massage the wire in place.
    • Put on some gloves and prepare the acrylic cement.

    • Keep the wire harness from moving too much from the 17 cm measurement.

    • Make sure the bundle lies flat on the outside surface of the endcap. Use your thumb to massage the wire in place.

    • When working with acrylic cement it is recommended that you wear gloves, safety glasses, and work in a ventilated area.

  41. Take off backing for remaining white acrylic piece. Place the white endcap accent piece flat against the outside of the endcap. This should be held firm as the wire bundle can push up and create a gap.
    • Take off backing for remaining white acrylic piece.

    • Place the white endcap accent piece flat against the outside of the endcap.

    • This should be held firm as the wire bundle can push up and create a gap.

    • Apply acryilc cement around all edges and center circle and allow to cure.

  42. It's time to start the potting. Grab the 2-ton epoxy. Wear gloves when handling epoxy and have paper towels on hand to clean any surfaces that it happens to drip on.
    • It's time to start the potting. Grab the 2-ton epoxy.

    • Wear gloves when handling epoxy and have paper towels on hand to clean any surfaces that it happens to drip on.

    • Find the starboard endcap (the one without the wire bundle) and place a piece of tape over the bottom hole. Make sure it is sealed.

    • Remove the 2-ton epoxy from the packaging and affix the mixing tube to the end of the syringes.

    • From the top hole, begin filling it in with epoxy.

    • Tilt the end cap towards you and fill the hole starting from the bottom. This will push out any air trapped in the back out from the top.

    • After a few minutes (once the epoxy has settled), check and see if you need to add any more epoxy to fill the hole to the top.

  43. These steps cannot be undone so double check that there is exactly 17 cm from the inside of the port endcap to the top of the bent DB-25 connector. Get the white polypropylene shell and set it next to your endcap as shown. Tape the bundles so they stay in place and drape the wires over the frame to keep them held vertically.
    • These steps cannot be undone so double check that there is exactly 17 cm from the inside of the port endcap to the top of the bent DB-25 connector.

    • Get the white polypropylene shell and set it next to your endcap as shown. Tape the bundles so they stay in place and drape the wires over the frame to keep them held vertically.

  44. Firmly and evenly squeeze epoxy out into the taller of the holes. Since the epoxy will be acting as a barrier between the water and your electronics it is important that epoxy surround and fill all the air gaps. To ensure that this happens, move the wires gently around and spread them apart and back together. Fill the bottom of the two holes and repeat the movements.
    • Firmly and evenly squeeze epoxy out into the taller of the holes.

    • Since the epoxy will be acting as a barrier between the water and your electronics it is important that epoxy surround and fill all the air gaps. To ensure that this happens, move the wires gently around and spread them apart and back together.

    • Fill the bottom of the two holes and repeat the movements.

    • Refill the top hole again unless it is already all the way full.

  45. It's very important not to let any epoxy cure in the area shown in the picture. This is the o-ring gland and needs to make a good seal with both the o-ring and your electronics tube.
    • It's very important not to let any epoxy cure in the area shown in the picture. This is the o-ring gland and needs to make a good seal with both the o-ring and your electronics tube.

    • After a few minutes, see if you need to add any more epoxy. Use a paper towel to remove excess epoxy before it cures.

    • Let the epoxy cure for 4-6 hours.

  46. Once here, you can move on. We are done with the endcaps for now. Epoxy still needs to be added around the syringe, but this will be completed in guide 5.
    • Once here, you can move on. We are done with the endcaps for now. Epoxy still needs to be added around the syringe, but this will be completed in guide 5.

  47. Continue your build by progressing to Guide 3.
    • Continue your build by progressing to Guide 3.

Finish Line

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