Author Topic: Oil or Grease--needle roller brg. lube  (Read 1690 times)

Offline Brian Rupnow

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Oil or Grease--needle roller brg. lube
« on: October 10, 2014, 11:26:28 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

Offline AOG

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Re: Oil or Grease--needle roller brg. lube
« Reply #1 on: October 11, 2014, 12:20:43 AM »
Since it's a display engine with no real loading why not try regular sealed ball bearings. There are plenty in that size range.

Tony

Offline Alan Haisley

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Re: Oil or Grease--needle roller brg. lube
« Reply #2 on: October 11, 2014, 12:39:35 AM »
If the crankcase filler is on the side up high enough that its bottom edge is above the splash point, will that serve? Kind of like old differentials. pull the plug and stick a finger in. If you can touch oil there is enough. Of course with a model the fill hole is probably too small for a finger but a piece of wire would serve.

Alan

Offline ogaryd

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Re: Oil or Grease--needle roller brg. lube
« Reply #3 on: October 11, 2014, 01:42:07 AM »
Brian, I believe a dab of grease or better yet oil in the crankcase is your best choice for connecting rod big end lube.  :ThumbsDown: "clingy" lube will end up clinging to the  cylinder walls and causing so much friction that I doubt the engine would start. Just my 2cents worth.                                                               Gary
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