I May Have Messed Up My End Caps


Following the 2.3/2.4 assembly videos, since they seem more detailed, even though I have the 2.5. I figured that if the older instructions didn't make sense, I would then refer to the newer (2.5) instructions for clarifications. That worked fine (so far as I can tell) for the internal structure, but building the end caps I ran into three problems:

1) The older method of syringe cutting was just one cut at 1.2, which is what I did. The newer instructions call for two cuts, one higher up (so too late for that), and the other to cut the tip off -- not sure why. So, I am hoping that the old way is OK.

2) The old instructions call for a blue circular piece with a cross cut in the middle to be installed as a potting dam. From what I can tell, the new instructions don't require that, and the part is not included in my 2.5 kit (right?). So, I can't do install the dam. Hopefully, I can get by without it, but am concerned that the old syringe method (which I used) necessitates that dam (which I can't put on since I don't have the part. Do I need the dam and can I buy it separately?

3) This is the worst part -- there are air pockets between each surface of my 4 plates on each end cap. I would say that there is a good 1/2" of good seal all the way around, but is that enough? I am thinking that I should pressure test (by making some plugs and dropping the whole thing down to 300 feet, then pull it back up and inspect. If I do this, I think I should do it before I pot. On the other hand, maybe I should just start over with the end caps. Is it possible to buy those parts (ie, 8 acrylic circles and 2 syringes) separately?

Thanks for any and all suggestions.



Hey Rick,

Sorry about the confusion. You may actually be okay with the endcaps you have, but if you're not in a terrible hurry, building another set may be best.

1) The reason we cut the end of the syringe off is because the 2.5 endcaps are shorter, and we need enough room for the plunger to fit all the way into the syringe. If the end of the syringe were left on, the depth of the hole the plunger goes in would be too shallow for it to fit in all the way. If it turns out that there is enough room for the rubber plunger to fit all the way in the syringe even with the way you put it together (it is pretty close that way), you're in good shape. If not, you can still test to see if the seal is good enough with the rubber plunger coming out of the syringe a bit. You can even just sacrifice being able to equalize pressure and just fill the syringe hole with epoxy.

2) The blue circular piece is not included with the 2.5 kit, but you shouldn't need it. The purpose of the piece was originally to brace the control horn from a servo, but what it ended up being used for was to hold epoxy surrounding the syringe to keep water from leaking in between the syringe and the endcap hole. For the 2.5 kit, we just put that epoxy around the perimeter of the syringe on the other side of the endcap (see step 28 of the dozuki instructions).

3) The air pockets are sometimes hard to avoid. In general, I think your endcaps should still work without the disks being fully bonded to eachother, but you likely won't have quite the same strength as you would otherwise. Most of the dives I've gone on are 20m or less, and if that will be the same case for you, you're probably alright. If you really do plan to go to 100m depth, then you may want to try a rebuild.

Okay, I hope that helps you through this.

I could probably give you a lot better advice if you sent some photos of your endcaps (and include the syringe plunger pushed inside so I can see how far in it goes).

We'll get you up and running!



Eric -- thanks for the quick reply.

Here are some pics to show how far seated the plunger is. The top of the plunger is completely below the top of the syringe housing, but just barely (maybe 3/100's of an inch). To depict that, I drew a reference line on the plunger. By noticing the change in the position of that line relative to the syringe, comparing the "punger at the top" to the "plunger all the way in" gives a sense of how deeply seated the plunger is. First (what I call) Side A:

1031-Atthetop.SideA.JPG (497 KB) 1032-Allthewayin.SideA.JPG (540 KB)


Here is Side B:

1029-Atthetop.SideB.JPG (521 KB) 1030-Allthewayin.SideB.JPG (583 KB)


I tried to take pictures showing the air pockets, but none are very useful. However, I can see that some of the pockets are within 3/16" of an edge. However, since that is a larger seal than the 1mm that the O-ring is supposed to create, maybe it is perfectly adequate?

Or maybe I should start over (just the end caps)? I cannot find any contact information on the store page, or any indication of how to purchase individual parts (I need the 8 end-cap pieces plus two syringes), or even whether that is available. Please point me in the right direction.

One last question -- you suggested that I consider filling the syringes with epoxy, with the caveat that I couldn't equalize pressure. Maybe I should fill one side, since it should be able to equalize with just one port, or am I missing something?

Thanks for all your help.

1028-AirPocketsSideA.JPG (532 KB)



I see that I forgot to answer your question about how deep I expect to use the ROV. I have a variety of uses in mind for use on my boat, which is a long-range fishing boat, and therefore takes me to areas that are far offshore, and maybe not well explored. During those journeys, we keep the searchlight sonar always on (like a conventional up-down fishfinder, but with the ability to look in any direction, as if controlling a searchlight; that way, I can track objects even when they are not directly under the boat). Sometimes, especially offshore at night, we see big fish, or LOTS of fish as deep as 600 feet. I really want to be able to send the ROV down to take a look.

My other uses (looking for surface fish, exploring shallow-water terrain when anchored, checking on my anchor, etc.) can be accommodated in 20 meters.

Thanks again for your help. I can't wait to complete my kit and use the ROV. -Rick