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How many RPMs will babbit bearings take?


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  #1  
Old 03-14-2005, 08:55:20 AM
Chris Curtis
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Default How many RPMs will babbit bearings take?

I am setting up a miniture line shaft system to power with my engines. The shaft I want to use is 1 1/2" dia. and supported on each end with a heavy cast iron carrier and babbitt bearings that are about 8" long each and have grease cups on them. With the pulleys I want to use this will turn about 1500 RPM. Will the babbitt handle that speed or am I looking at a meltdown situation? The loads will be pretty light- more of a moving parts display than anything else, but it will run for long periods of time.
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Old 03-14-2005, 09:16:04 AM
Harvey Teal Harvey Teal is offline
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Default Re: How many RPMs will babbit bearings take?

What pulleys, sprockets etc will you be running on the shaft, and how much radial belt loading?
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Old 03-14-2005, 09:20:41 AM
Pat Barrett Pat Barrett is offline
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Default Re: How many RPMs will babbit bearings take?

While I am not an expert in this field, I say "YES". The proper thing to do is use No. 1, or by another name, High Speed Bearing Babbitt. It may be also known by other names. Maybe someone else can give you the percentages of the contents in it. In Nascar they use babbitt lined bearings in the engines and turn them 9,000 rpm's sometimes. Another good idea would be to replace the grease cups with drip oilers and lubricate the bearing with oil. At high speed it will lubricate better and help cool. Hope this helps. Maybe you can get some others opinion on the subject. (Most car engines use babbitt lined bearings)
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Old 03-14-2005, 09:29:21 AM
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Keith Smigle Keith Smigle is offline
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Default Re: How many RPMs will babbit bearings take?

I don't know a lot about line shaft engineering, but I want to clarify some details. You will have 8 linear inches of shaft support on both ends? What is the distance between the supports? I believe early autos used poured babbit main bearings so I suspect 1500 RPM bill be no problem. If you want to lower the RPM some, you could always use slightly larger pullies.
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Old 03-14-2005, 10:04:19 AM
Andrew Mackey Andrew Mackey is offline
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Default Re: How many RPMs will babbit bearings take?

My 1950 IHC L 120 was rated at 3600 RPM, with poured bearings, you should have no problems.
Andrew
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Old 03-14-2005, 11:24:26 AM
Chris Curtis
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Default Re: How many RPMs will babbit bearings take?

Each bearing is 8" wide or 8" of babbit surface against the shaft on each end. They about 42" apart with a 4" flat belt pulley in the middle, a 10" on one end and a 3" on the other end. I am using the pulleys I have and need that RPM to spin my equipment fast enough. I may try and switch to oilers if that will be better. Thanks for the help.
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Old 03-14-2005, 01:49:58 PM
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Forrest A Forrest A is offline
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Default Re: How many RPMs will babbit bearings take?

Quote:"In NASCAR they use babbitt lined bearings in the engines and turn them 9,000 rpm's sometimes."

This isn't true. The rod journals are of the insert type not babit and the RPM range is much higher now, almost 11,000 RPM maximum now! I worked a little once with an race engine builder and there isn't any turn of the 19th century bearing materials in there.

Forrest
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Old 03-14-2005, 06:33:28 PM
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Default Re: How many RPMs will babbit bearings take?

I think 1500 RPM's is way too much on a unbalanced shaft with babbit bearings/ poured bearings. Look at a John Deere E turning 500 rpms and you can't see the spokes its turning so fast or your car engine idling at 2000 rpms. Give it a try, I would think it wouldn't sound very good at that high RPM without a pillow block sealed roller bearing. Am I correct that you want your line shaft turning 1500 RPM and your equipment your running 2 or 3 times that rpm? Just my opinion.
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Old 03-14-2005, 07:13:34 PM
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Craig A Craig A is offline
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Default Re: How many RPMs will babbit bearings take?

Every old wood planer ever built ran in babbitt bearings before the advent of ball bearings. They lasted thousands of hours running at rpms in the thousands and under some of the heaviest loads imaginable. Some used grease for lubrication and some used oil wells with oil rings for constant lubrication. Don't sweat a line shaft running in babbitt bearings.
Oh, your car engine? It's running on steel backed babbitt bearings......
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Old 03-14-2005, 08:02:06 PM
Jim Tremble Jim Tremble is offline
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Default Re: How many RPMs will babbit bearings take?

Quote:
Originally Posted by Craig Anderson
Every old wood planer ever built ran in babbitt bearings before the advent of ball bearings. They lasted thousands of hours running at rpms in the thousands and under some of the heaviest loads imaginable.
Craig

I have one of those planers and it turns 5000 RPM. Still has the original babbitt bearings. A little loose but they still work. Early 1920s.

Jim
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Old 03-14-2005, 08:26:07 PM
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Craig A Craig A is offline
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Thumbs up Re: How many RPMs will babbit bearings take?

Quote:
Originally Posted by Jim Tremble
Craig

I have one of those planers and it turns 5000 RPM. Still has the original babbitt bearings. A little loose but they still work. Early 1920s.

Jim
Hey Jim!!! Take out some shims and PLANE AWAY!!!
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Old 03-15-2005, 07:28:11 AM
Harvey Teal Harvey Teal is offline
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Default Re: How many RPMs will babbit bearings take?

Chris, if you can keep the pulleys close to the bearings you can do it. The 42 inches between bearings is about the max distance I would run at that speed.
Run the bigger pullies outboard of the bearings, and move that small pulley away from center and near one of the bearings. Use oil in the bearings instead of grease, and build oil slingers to catch the oil which WILL be flung from the shaft. keep the pulleys clean and free from any chunks of belt dressing etc that might unbalance them. Make sure the pulleys are rated for that speed. How about some pics?
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Old 03-15-2005, 12:01:36 PM
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Rob Skinner Rob Skinner is offline
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Default Re: How many RPMs will babbit bearings take?

Quote:
Originally Posted by Chris Curtis
carrier and babbitt bearings that are about 8" long each and have grease cups on them. With the pulleys I want to use this will turn about 1500 RPM. Will the babbitt handle that speed or am I looking at a meltdown situation? The loads will be pretty light-
Hi Chris,
Speed in itself is not the issue. The real concern
(pressure in psi) x (velocity)
Exceed the acceptable limits and the lubricant will fail to carry away the heat as fast as it is generated, and you'll end up with failure.

Your two bearings are each 1.5" diameter x 8" long, which is a LOT of surface area. Your load will be light. Therefore your pressure will will be very light.

Consider stationary engine cranshaft bearings that are
1.5" diameter. From memory of engines we've seen, we might expect the bearings to be about 2" long and the engine to run about 375 rpm.

The flywheels on such an engine are very heavy, there is a huge impulse every time the engine fires, and there is the tension of the belt added onto the load that those bearings must withstand.

Your proposed project will run four times as fast, but the load of just a couple pulleys, lesser impulses, and less belt tension will be far less than that imposed upon any engine bearings. BUT, your bearings are going to be four times longer!

There are many more considerations to bearing design, but I think if you keep 'em lubricated, your bearings will work out fine.

Rob
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