- #36
Aquasky
- 15
- 0
thanks for your advice fredGarvin
triden said:What about a seal they use on engine crankshafts? Just off the top of my head...they have to handle very high PSI and RPM's faster than what you need. Would something like this work?
Danger said:This is not my area at all, but I think that what you're asking is impossible to answer as is. To start with, any amount of thrust will move the thing.
The part about fighting a 6 knot current is so out of bounds that it can't even be considered. What shape is your fusilage? Do you know the Reynolds numbers and such-like? What is the size and pitch of your propellors? Are they ducted, or open? And etc...
Aquasky said:Hi Guys,
I'm having some problems on my ROV designs. How do you seal the motor casing with the cables? Do you use underwater cable connectors? Is there other alternatives? I uses cable gland with the cables inserted through a metal pipe that can give the cable gland a good seal.
Next, I'm using 4 x 24VDC reversible motors, can a high speed motor (without gearbox) run well rather than to use a high torque motor?
Aquasky said:Hi Joe,
Thanks for replying. I'm quite confused from the ways the sealing of the cables you describe.
So far, I been experimenting two glues, 1) RT Resin and 2) Aquaseal. I tried to seal the cables with these two types of glues and place the cable in a moulding, both form a nice cylindrical shape. However, the RT Resin dry up too fast, before I can seal the internal gaps of the cable properly, it dry up. The aquaseal was a better choice, and since it cannot stick with metal, my mould was made from a brass rod. Cut into half and drill the desire diameter I needed for the cable gland holding thickness. The aquaseal pass the water-proofing, but I had yet put it for a pressure chamber test.
I tested my reversible motors, found that the brushless reversible motor keep stalling in water, even when the torque haven't reach its peak. Still trying to find out the problem.
Ruddles said:try to get hold of a marine sealant called Sikaflex 291, buy the small toothpaste sized tube, you don't need a lot. apply this to the cables, remove the outer cover if multi core - insert this into the gland housing, fill with 291, let it cure for 24 hours - important as otherwise it will shrink ! - then apply the locking or compression nut to the gland - when the sika cures it makes a superb flexible gasket.. ways of sealing individual cables are by using smalll amounts of cyano acrylate (super glue) down the sheath, or a product called captain trolleys creeping crack cure.. or something similar lol, both the sikaflex and the crack cure are used on boats. for a more solid fitting use 3m 5200, but that will not be removed easilly !.
re the problems with the motors (BLDC) some of these units expect to run at an appreciable rpm, maybe a gearbox is in order, what motor are you using ? and what kind of speed controller ?
Joe
Aquasky said:Hi Joe,
Can the glue be able to hold at 100m depth?
The motors that I used were BLDC motors & Stepper motors from Oriental Motor, the BLDC motor model is BLHM5100K-A. I bought it without gearbox, it came with its controller.
Aquasky said:Hi Joe,
Can the glue be able to hold at 100m depth?
The motors that I used were BLDC motors & Stepper motors from Oriental Motor, the BLDC motor model is BLHM5100K-A. I bought it without gearbox, it came with its controller.
Ruddles said:By the way Aquasky . What are you intending to use the rov for ?. Perhaps it may help you if I pass on a list of favourites from internet explorer for parts suitable for rovs. ?
You can emal me at captainslarty AT yahoo.co.uk
Perhaps it may save us both reinventing the wheel as we are doing independent research here.
to give you an idea, hows this for a cheap prop unit...
http://www.mtroniks.net/details1.asp/ProductID/261/lockit/true/ductfan68.5.htm
Joe
Joe.
Aquasky said:Hi Joe,
The links you shown above, seems like RC models parts. I'm not making a ROV for personal or entertainment use. The ROV I'm making now, may require for use in offshore pipeline inspection etc.
Ruddles said:Hi Aquasky, no reason NOT to use available parts. The videoray unit uses simple brushed dc motors and is still agreat comercial product. Mone is also not really intended for personal use. I want a design I can sell to yachtsmen etc.
Joe
Aquasky said:Hi Joe,
I had emailed you and attached some of the details. We can share our knowledge.
Aquasky said:Hi joe,
Nice to know you. Currently, my ROV housings were designed through solidworks and machined by CNC system (CAD/CAM).
maybe we can even joint-venture later.