Journal Bearings

craigclavin · Post by **craigclavin** » Mon Jul 30, 2007 5:42 pm

I’m currently designing my axial GT and I’m seriously considering using Journal bearings. Does anybody have any experience in this field?

With working for Cummins Turbo Technologies I see journal bearings used in all our turbos, these often achieve way over 100,000 rpm and last over a million miles of service, that’s a whole lot of use!
I understand for use in model aircraft the addition of an oil pump/reservoir is not favored due to the weight, but surely the increase in safe rpm and minimal down time due to not having to change bearings is desirable? Or have I overlooked some design flaws?

For those unfamiliar with these types of bearings, please refer to the following wiki article!

http://en.wikipedia.org/wiki/Fluid_bearing

Ash Powers · Post by **Ash Powers** » Mon Jul 30, 2007 6:17 pm

Oil containment will likely be the biggest challenge - you'll need a "tube in a tube" design with a feed and a drain port, with both ends of the shaft sealed as well. It would be a more complicated design to pull off especially with an annular combustion chamber.. not impossible, but certainly more complicated. It is just a lot easier to use hybrid bearings and use either a fuel-oil mix or a dedicated oil reservoir fed by P2.

craigclavin · Post by **craigclavin** » Tue Jul 31, 2007 4:40 pm

Yeh, i understand what you are saying, i guess its a personal choice in the design/build stage. Once a decent engine has been achieved, i cant see why it wouldnt be at least equal in popularity for the amateur builder. Even if it is just confined to the test bench - at least there wont be many bearing changes! or potential for less anyway

As for the oil leak problems i think i will go for a rubber o-ring inbetween the shaft housing and front and for the rear maybe ill go for a stainless steel gasket. I know in turbos that the oil turns into a froth, maybe this will be my next problem...Oh well, somebodies go to explore!

Just a note, might be getting my hands on a solid machined impellor, doubt ill be able to get a machined titanium one