Most liked posts in thread: Made One Of These Today

I Spy With My Little Eye....

TIRES!

 

So ya going with some 28" DUBs.....

 

Sorry to spoil your surprise. Make some moon wheel covers & then pull them off to everyone's amazement.

 

WOW ^^^

Must not show my wife. :frown2:

 

MM is sweet. What's something like that run? Ball park figure

 

92 inches in diameter and 22 feet long... It's big. And the compressor has a 20" suction line.

 

No, the bearing alignment is good... The housing is line-bored to 0.0005" true position (regardless of feature size). It's the bearing to shaft clearance that I need to modify. Normally I design for a diametral clearance of 0.0012 inch/inch of shaft diameter. The shafting is ~5" in diameter. But my tests are indicating high shearing loss and reduced oil flow. So I am opening up the clearance by 0.004". ..(0.0016 inch/inch of diameter). The increased clearance will reduce the shear and also increase the mass flow of oil. So the bearings will generate less heat and the increased flow will help to carry the heat out of the bearings too..

The lubricant is a mixture of refrigerant and polyolester oil (POE). The refrigerant tends to flash out of solution at low pressure zones in the bearings...(bad). And due to the 2-phase flow characteristics, it is very difficult to computer model. So this week I'll try to dial in the performance by experiment. This is going to be a long week.

 

What are you pumping, ammonia?

Aren't they roller bearings?

 

R134a (the same as in your car)..... not ammonia. And the journal bearings are fluid film type with tilting pad thrusts ... Each bearing in my compressor sees 9,000 pounds of radial load. Rolling element bearings cannot handle the load and speed ...plus they are life limited.

 

Way past my pay grade.....

 

If I don't get this working by the end of the week ... It may be above mine too....

 

You said it!

 

These particular vapor compressors will run for at least one solid year of continuous duty at a stretch and also have a required 80,000 hours minimum service life between overhauls. The bearing parameters are...110mm shaft size / 12,000 RPM / 41,000 newton (9000 Lb) dynamic load. There isn't a rolling element bearing out there that comes anywhere close...not even ceramic bearings. The shaft size required to support the gear load results in rolling element bearings that are simply too large to tolerate the speed. Rolling element bearings also have a noise signature that is unacceptable too. (We really don't like to be heard on sonar) Ball bearings are not well suited for MIL-S-901C Shock testing either. Hydrodynamic fluid film bearings handle the load and speed without noise or L10 life issues common to rolling element bearings.



- Paul

 

Well.... No, but they are a customer. And so is Jack Daniels, Coors, Anheuser Busch,... (My favorite food groups.). We do process cooling as well as comfort cooling for a wide variety of applications...

135 year old company......South Central PA.

 

Whadja hafta do to get it in spec?

 

I opened up the journal bearing clearance by .004" on the diameter for the pinion and gear bearings. Shortened one pinion bearing to achieve L/D of 0.8. Added a hydrodynamic pocket to the unloaded section of each of the two low speed journal bearings ... Added a second drain port to the low speed forward thrust bearing. And increased the size of the primary scavenge ports of both the high speed and low speed thrust bearings...

It took a bit work ... and I'm glad it is behind me now. Whew!