Can you provide more details on your plastic bearings (e.g., spec sheet, vendor contact, etc.)? I assume that these can be replaced when necessary by the user? Will you stock spares or provide a link for direct purchase? Does your supplier have any data on wear properties (e.g., hours of operation at given speeds), particularly when used “wet”? I also wonder about their performance when there is suspended sediment or particulates in the water? Your pressure tests will also be telling. Thanks!
I've moved your post the the "Blue Robotics Product Support" forum since that seems like the right place.
The bearings are made by Igus and use the H370 material, which is specifically designed for underwater applications. If you visit their website, they have a bearing lifetime calculator that can give a rough estimate of the bearing life.
The bearings are somewhat difficult to replace. In one of our prototypes, the bearing became jammed with the shaft (due to a tiny piece of plastic in the water) and the bearing came loose. We're now gluing them in instead of press-fitting them. They can be removed by drilling out with a 5.5mm drill bit. We'd be happy to send you some if yours become worn, however the expected lifetime is very long.
Sediment and sand does increase wear on the bearings but we've done some extended testing with tons of sand running through the thruster and no visible damage. Pressure tests are coming soon as well and will be interesting.
Thanks, Rusty -
So these are actually bushings? The H370 material sounds ideal. What metal did you choose for the shaft anticipating use in salt water?
Yes, they are bushings. The shaft is stainless steel 316, which seems to work pretty well in saltwater.
The choice of 316SS was a really good choice. On the electronegative scale, that variant of steel is ideal for saltwater. A lot of connectors that I build stuff with are made from either Monel 400 or 316SS and have lasted for 15+ years in saltwater. We typically shoot for 7 with 14 years as an ideal life with that material and others we use.