Alternative to using straps for Battery Tubes


#1

I was having trouble keeping the battery caps seated since I couldn't get the straps tight enough so I made this mod that works a lot better for me. I used a 3D printer to create the clamps

I've attached the STL files and a few images to illustrate.

Along with printing the parts from the STL files you'll need;

  • (4) All thread rods measuring 10.75" long. 10-24 SAE or 5mm .8 to stay consistent with whats on the ROV.
  • (8) Matching nuts.
  • (4) Washers.
  • (4) Wing nuts matching all-thread rod.
  • (8-12) M5-.8 nuts (8 nuts are required but depending on thickness you may need up to 12
  • (16) pieces of aquarium tubing or heat shrink to fit over threaded rod. each piece approx .25" long.

I suggest installing the clamps to the front of the tubes first. Once positioned, glue the clamps to the battery tubes with CA. It's possible to make a one piece clamp that would not require glue but which may distort the tube when tightened. I felt using glue was a safer choice.

batery_tube_clamps.stl

end_caps.stl

I've attached a few images. The clamps u see are repeated at the rear of the tubes.

20150120_174241.jpg

20150120_174157.jpg

20150121_165229.jpg

The Rear end plates may need to be cut down .25" along their lengths to clear the rear fin.


Battery EndCape issue
#2

Jerry,

Very cool! Yeah- the buckles we ended up with don't seem to have quite the cinching power that we'd like to have ideally. Your modification looks pretty solid, and major points for posting all the info so others can replicate what you did. Thanks for that!

Another idea I've been working with is a sort of latch mechanism which would allow very tight cinching through mechanical advantage and would also confine any extra strap material. I've attached a diagram below (drawn in my favorite, MSPaint, of course!) which depicts how it works.


Basically, the mechanism is constructed out of a flat, rigid, rectangular part that has a hook on one end (A), a permanent attachment point for one end of the strap in the center (B) and a cinching attachment point (C) on the other end of the strap. When the mechanism is in "loose" mode, the two ends of the strap are able to pull so that the part between points (B) and (C) would be in tension if the strap were loaded. The length between (B) and (C) is what gives the strap its slack in this mode. When the mechanism is to be put in "tight" mode, end (A) is folded over the rest of the mechanism and the hook there is latched around the strap going in to end (C) to keep the mechanism in that position. The excess strap coming out of point (C) will now be confined between itself and the mechanism. With the strap adjusted properly (at attachment point (C)), the lever action of (A) folding over will cause the points between (B) and (C) to be in compression equal to the loading on the strap.

I've asked a local machine and die cutting shop how much the tooling would cost to make a bunch of these out of aluminium or stainless steel, and their quote was close to $10,000. (eeps!) It would be cool if the parts could just be laser cut, but I fear that acrylic would be too brittle and polypropylene would be too flexible.

I'd love to hear other ideas for holding endcaps closed as well. I love figuring this stuff out!

~e


#3

I too had some problems with the straps. I broke one clip trying to tighten before my first dive!

Looking back, I was probably trying to get it too tight. I guess as long as the oring is sealed, there isn’t a need to have the battery tubes as tight as possible? There a fair amount of play.

But I picked up a fairly small stainless turnbuckle and tied a piece of cord around the side to test. I can tighten the turnbuckle by hand enough to get a better tension than the shipped straps. Adds some weight but I needed a little anyways. I wouldn’t suspect the turnbuckle will loosen on its own, or am I just being wishful? I’d upload a photo but the forum says new users can’t?

I was also contemplating some small shims/wedges to wedge between the end cap and the strap or cord.

Eric


#4

The turnbuckle sounds like a winner.
to be honest I didn’t like the play in batteries, and I kept trying to get the straps extra tight.
My newest addition is a stainless sled for bottom dives. The ROV was just plowing in the muddy bottom and I couldn’t see anything. To compensate for the weight of the sled I created a fiberglass chamber along the top to act as a BC. Right now the sled is neutrally buoyant. Hopefully I’ll get to test this weekend.
In the image attached I still need to cut the threaded rod down to size. I used the holes along the shell so that I can remove it for open water.


#5

The sled looks slick.

Here’s a photo of the turnbuckle I tried. 1/4" x 7 1/2" stainless loop and hook and aluminum housing.


#6

I also found it difficult to get the straps tight with the buckle mechanism.

What about a simple Velcro strap?

I couldn’t upload an image (new user), but here is a link to one…

http://www.aerostich.com/hook-and-loop-cinch-straps.html


#7

The only concern I have is sediment and salt eventually lessening the holding power. I know the velcro on my surfboard leash is a mess. easy enough to replace though if that happens.


#8

Hmm. Good point.

How about reusable zip ties? I am not sure how long reusable zip ties
would last and if there is a long enough version available.


#9

This is a shot of the OpenROV team having the same discussion :smile:


#10

I found these straps at the outdoor outfitting store and they worked very well:



Amazon:
http://www.amazon.com/Sea-Summit-Accessory-Strap-Release/dp/B004WBAESQ/ref=sr_1_1?ie=UTF8&qid=1424645849&sr=8-1&keywords=sea+to+summit+hook+release


#11

That appears to be the perfect replacement.


#12

I love the bottom skids… I’ve been toying with the idea to add skids to mine. I also like the battery tube clamp system. Please keep us updated on how these mods are working for you…


#13

The clamps are working great. Still having some issues with the skids digging into soft bottom. Next step is to add ski type attachments. I’ll send updated pics when they’re done

Sent via the Samsung Galaxy S® 5 ACTIVE™, an AT&T 4G LTE smartphone


#14

Hi again Jerry. Looking at the skids (I like the concept) but I do notice a “possible” issue with them. In the front, where the skids curl up, they are truncated. This creates a possible “snag” issue and would certainly allow the skid to dig in to the substrate. If you notice this happening, one possible solution might be to continue the curved front of the skid up and back to the front of the battery tubes as to create a nearly closed loop. As to the ski type attachments, perhaps a thin, flat sliver of thin HDPE sheet might help if attached to the bottom of the skid.


#15

Hi Ronald.
Good point on the potential snag issue. I’ll keep an eye out for that. I’m creating the ski out of 1/4" poplar which I’ll encase in West Systems. I’ll mount them so they can rotate along the axis of the skid. This should allow them to pivot over mounds or rocks.

Sent via the Samsung Galaxy S® 5 ACTIVE™, an AT&T 4G LTE smartphone


#16

Hi Jerry. I’m currently making a variation to your battery tube clamp system. I do not have access to 3D printer or laser cutter so I’m going to attempt to build something with basic hand and bench tools . I’m using HDPE and 6 - 32 all-thread. It’s going will so far. I’ll post pictures when it is finished. I’ll be using it as a mod on my v2.6


#17

Hi Ronald,
if things don’t work out, let me know and I can print a set of the clamps for you.


#18

Here’s an update I made to the skid.
The skis are poplar which I covered in West Systems Epoxy. I used the extra-slow curing hardener to give the epoxy the most time to absorb into the wood. Using the zip-ties to mount the skis allows them to pivot along the axis of the metal runner. I’m hoping this acts as a type of suspension to go over small bumps.
The red center portion is a piece of closed-cell foam covered in thin fiberglass. It acts as a buoyancy compensator. The whole thing is slightly positively buoyant in saltwater.


#19

Hi Jerry. I managed to fabricate a clamp system with HDPE and some basic hand/bench tools. It appears to be working well. I’ll be posting pictures of the system in a few days. Thanks


#20

Battery Tube Brackets:

I’m running a v2.6 OpenROV and I’m using the Battery Space Li-FePO4 batteries with spacers. During initial bathtub testing I noticed a problem with the battery tube and battery configuration. When the ROV bumped in to anything, it shut down.

As a result of some careful troubleshooting and experimentation I was able to determine that when the ROV bumped in to anything, the batteries shifted (within the tubes) and caused a momentary discontinuity, which caused the controller to shut down.

As a temporary remedy I used electrical tape and taped the three batteries (on each side) in to a stack. This temporary fix appeared to work fairly well, but I really wanted to come up with a better, more permanent solution to the problem. Enter that never ending and always evolving resource for all information “OpenROV” - the OpenROV Forum…

After searching the forum pages I was able to find a post by Jerry Baccari titled “ Alternative to using straps for Battery Tubes Alternative to using straps for Battery Tubes .

My idea for resolution of the loose battery problem was to increase the spring tension on the batteries, inside the battery tube by increasing the thickness of the “spacer.” Unfortunately, doing this would also increase the tension on the battery tube end caps, thus pushing the end caps out and exposing the batteries to the water (No bueno).

Enter the application of Jerry’s battery tube clamp system. With this system, I can clamp the end caps securely on to the battery tube and hold them in place despite the increased spring tension on the batteries and end cap.

I decided that I really like Jerry’s design but he used a 3D printer for fabrication of the plastic parts and I do not have access to such technology. So how to fabricate my own clamp system using the basic hand & bench tools that I have available?

I was able to fabricate a functional clamp system using sheet HDPE, all thread and some nuts and washers (all available at the local hardware store). Tools: Circular saw, hand saw, wire cutters, grinder, bench sander.
I have attached a photo of the finished product.