Homebuilt ROVs Forum

TigerShark wrote:Is that lost wax casting?

I have been making progress on my Rice Nozzle. I am getting 2lbs of thrust from 5.5A using a 55mm 3 blade prop.

That's Ole's thruster design. I printed it in pla, joined the two parts with wax then investment cast it as one piece in aluminum. It's called lost pla casting, very similar to lost wax.

Hi!

Back from holidays now and getting ready to finish my thruster testing this weekend. A few more blade designs and in a bigger tank so I can max them out without drawing in air.
I will try to make a short youtube clip of it while I'm at it.

In other news, I think I have my tether figured out.
100m (330ft) of 2 lead 24awg wire twisted in to 100m of 6mm floating line. This is normal 3 braided rope and is much easier to come by then the hollow, diamond braided type.
Tested 1m of this in my kitchen sink and it is slightly buoyant actually. Using a thicker wire or thinner rope would maybe be better, but 6mm rope was the smallest they had at the shop I visited. And I guess adding weight to it is easier than adding buoyancy
The rope with the wire is very flexible also. Still not optimal as a rope in water will create more drag than a "slick" cable.
I have an idea for a tool that I can print that will help med thread/braid the wire in to the rope. Will give this a try next week maybe.
Any ideas or comments on this thought?

I quickly modeled my idea for the "TetherThreading" tool.

The two spools of rope and wire would hang from each end of the arms.
The three parts of the rope would be split up and threaded through the three outer holes and the cable in the middle.
Then hopefully, by pulling the rope and wire through while twisting the tool (along with the spools hanging from it) the rope will open and threaded around the cable. The rope won't encapsulate the cable, but after the 1m test I did today I think it will be good. Even when I bend the rope, the cable is still protected by the rope. Also the rope is rated to 770kg, so should be enough I guess

Your tool looks a bit like the tools they used in the old days to make a rope.

Got to do a lot of testing with different blade types this weekend.
I had a few failures and some interesting numbers. More on that later.
And I'm not done yet. Now that we have a 250l test tank set up I am going back this week to do some more testing with different blade shapes and a few tweaks based on the data we got this weekend.

TURN DOWN YOUR VOLUME!

Wow 3Kg at 17A! That should be enough thrust!

Did something interesting today while printing new propellers.
Earlier in this thread I made a post about treating the ABS prints with acetone vapor. I found that test piece today and wanted to see how much stronger that piece was if at all.
While not the most accurate method, I used a kitchen scale and a pair of pliers to press them down to see what force it took before it broke. The untreated piece broke at about 350g (0,77lb). It pretty much broke right showing very little flexing before it broke. The acetone treated piece broke at 1200g (2,6lb) and flexed more towards the end. Thats quite a difference
Before the test I measured the thickness of these blades to be 1.6mm thick

I should also note that I broke 3 propellers this weekend. All broke when I maxed the speed. So this should eliminate that problem. Also, on the second print today I got a phone call just as I started the printer and didn't check to see if everything was ok until 40minutes later.
Seems my printer made some sort of deep sea creature

I was looking into the taulman bridge for printing parts like your propellers. It should be very strong. Waiting for delivery now.

Cool!
I have read a little about the stuff, but not tested it myself. Should be excellent for this type of stuff. Keep us updated how it goes.

Thrusters done!
See my post int the Thruster section for details viewtopic.php?f=3&t=1268&p=8676#p8676



Now on to figuring out my manipulator while the thrusters are being printed.