View Full Version : Oil or Grease--Needle roller brg. lube

brian Rupnow
10-10-2014, 06:25 PM
On the fall engine project I am building, I wanted very badly to go to a grease filled needle roller bearing on the big end of the con rod, with no inner race but with a hardened rod journal, and grease seals on the bearing. This would have let me run a dry crankcase. Unfortunately, no one sells 3/8" needle roller bearings with seals now. This means I will probably have to run some lubrication in the crankcase. I'm rather torn about what exactly to do now. The engine will be a slow revving display engine, not run frequently and not run under load. It was designed primarily to see if I could design and build a side valve (flathead) engine from barstock with no castings. My gut instinct is to give the needle bearing a good coat of grease and run it that way. Of course the problem is that with a sealed crankcase there is no way to check and see IF the bearing required more grease at some point in the future. The other option is to put a filler tube on the crankcase and run a very small amount of lube in it for the big end bearing. The small end bearing is also a needle roller bearing, but it is pre greased and does have seals, so I'm not worried about it (It doesn't ever make a full revolution anyways, just rocks back and forth). The wrist pin is hardened. I run a small percentage of oil in my fuel to keep the Viton o-ring on the piston lubricated, so the only real issue is lubricating the big end bearing. I am thinking of running a small amount of really "clingy" oil in the crankcase, something like chainsaw chain oil. Again though, since the crankcase is essentially closed, and I will be running only a small amount of oil in it, it becomes very difficult to monitor the oil level. I am open for suggestions that do not include remaking any parts.---Brian

10-10-2014, 06:37 PM
Brian, you are overthinking this problem, (at least I think so.) Consider the needle bearing on the drive sprocket of a chain saw. How fast does it turn? There is no provision for lubrication that I can see except perhaps the odd splash of chain oil. How long do they last?
Give the bearing a lick of molycote or lithium grease and assemble it and forget it. It will be running when you are dead, particularly under the conditions that you describe!
I am waiting to see it run.

10-10-2014, 06:51 PM
Have you given any thought into installing your own seals at the the ends of the bearing?
There are a lot of different seals available. I can't recall just where, but I remember replacing some very narrow seals on something in my past.
Some of them were just made of neoprene with no hard shell. Those could have been wiper seals on small cylinders.
Just another thought to stir up the brain cells. I know mine need a little stir more often these days.
I am also looking forward to hearing how it runs.

brian Rupnow
10-10-2014, 08:08 PM
Duffy---I like your idea---It has the least amount of work involved. Cuttings--I have no room for seals. I may grease the bearing with some molycote AND put a bit of chainsaw oil into the crankcase before I seal it up. Can't see that it would hurt anything.

Wayne Sippola
10-10-2014, 08:10 PM
I think it will work fine without seals. There isn't any reason for the grease to move out of the bearing, and with the crankcase sealed, no contamination to move into the bearing.

Or you could drill the crank and put a grease nipple on the end. Seems you like a challenge...


brian Rupnow
10-10-2014, 08:20 PM
Wayne--I like a challenge, but the journal that the con rod rides on is hardened steel. Bit more challenge there than I can handle. Trenton eh--I worked in Trenton for 3 years in the 1970's at Central Bridge, a division of Toronto Ironworks. I was working there taking inventory in the steelyard when Henderson made the winning goal in the Canada Cup. Worked in Belleville for 15 years at Stephens Adamson. I lived in Frankford for a while, in Stirling, and in Belleville.--Still have relatives living in Brighton.---Brian