Drive shaft seal?

[Louis_Cha]

Hello all,

For the ROV I'm building, I will make my own thrusters (due to cost) by having a motor in the end of a piece of plumbing pipe, the end of which is covered and sealed. The drive shaft will go through the end cap to the propellor.

I need to seal the prop drive shaft, how would I do this? U rings? labyrinth seal?

Thanks, Louis

[rossrov]

Radial shaft seal. The lip side (opposite to the flat side) faces the pressure. With a non- compensated, or air filled housing, this would be the water side. For compensated oil-filled housing, it is the inside.

[Louis_Cha]

Thanks for replying. I have a non-compensated housing, and I'm looking to diving to a maximum of 30m, would a radial seal shaft resist that pressure? I think I should have two at different points along the shaft, to make it more secure, or is this unnecessary?

[rossrov]

I would suggest using just one seal. Keep shaft diameter as small as possible to minimise circumferential speed and hence friction and wear of the seal /shaft. Small as possible means using a shaft the same size as the smallest seal you can find, assuming that this will be around 4mm. 3mm seals are available but the only ones I know of are dearer. 1/8" I think are also available from the same mob in the UK as the 4mm.
Depth I cannot advise on except to say that more pressure on the lip side = more friction and hence more wear. Maybe once you have all the other ROV bits working you can make just one thruster (vertical?) and do a real-life depth test. Monitor tether pull or even motor current. If successful (meaning friction not affecting motor too much and seal/shaft not worn and leaking after whatever lifetime you decide on for them) make the others the same.

[Ian MacKenzie]

Speaking of seals, what do you guys think of these for a manipulator. Low speed, 20 to 30 rpm.


http://www.mcmaster.com/#ring-seals/=vdbzi1