Needle bearings, on axles.

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tetramachine
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Needle bearings, on axles.

Post by tetramachine »

My LE. Pacific has ,needle bearings on the drive axles, and friction bearings on the lead and trail axles. The trail bearings are a loose bronze bearing on the top, and nothing on the bottom, not even felt for lubing. The lead wheels have 2 bronze halfs, bolted together.

Would it make sense to replace the trail axlewith ,needle bearings, or just put felt and oil into the journal box.

Tom
My wheels don't slow me down
hoppercar
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Re: Needle bearings, on axles.

Post by hoppercar »

Id stick.with the felt and oil....if your going to.swap them out for needle bearings, you.will have to.make new axles and have them hardened for the needles to.run on, or at the very least, loctite an inner bearing sleeve on your existing axles
Mike Walsh
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Re: Needle bearings, on axles.

Post by Mike Walsh »

I agree with hoppercar. These engines have run for years using the existing design.

I would add felt pads for your journal box cellars - if nothing else, helps retain much more oil, and can possibly keep the axle in place (when the trailing truck is lifted, but the wheel isn't). Have fun!
Asteamhead
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Re: Needle bearings, on axles.

Post by Asteamhead »

Hello Tom,
I would not recommend needle bearings for use in leading or trailing axles due to axial forces to the wheels :( ! Thus additional axial brasses will be necessary anyway.
Instead, a pair :idea: of standard ball bearings in each (outside) axle box will do fine without any trouble. Works for years at cars, tenders and both boogies or trailers. Sorry for dimensions are mm :( - just an example.
Needle bearings for use with driving axles will do yet due to very low axial forces to these wheels.
Just my two cents

Asteamhead
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rudd
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Re: Needle bearings, on axles.

Post by rudd »

On the bearing races, rather than sleeves on the axle, how about boring the end of the axle and pressing in purchased hardened dowel pins? (axle is shorter of course)
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Re: Needle bearings, on axles.

Post by Pontiacguy1 »

You absolutely can use needle bearings in lead and trailing trucks. I have done it several times. To echo what some have said above: If you are going to run the needle bearings directly on the axles, they must be hardened and either ground or polished to size. They need to be pretty hard, too. The normal recommendation is 58 to 62 Rockwell C hardness for a drawn cup needle bearing inner race surface, although for our application (speed and load) they will last a long time with a softer running surface (around 45-50). If you don't use hardened surfaces, they will eat up and be ruined in fairly short order. If you use a hardened inner race pressed or loctited onto your axle, that will work great. The ones that I made, I turned the axles oversize, case hardened them, and then ground them to size. They have run a long time and still look like new. As steamhead said above, needle bearings will absorb no thrust, so you have to have another mechanism to absorb your side thrust. My axle box faces still do this, and they do need to be lubed occasionally.

Why did I use the needle bearings? Only because the axle boxes were so small I really couldn't get a ball bearing in there. If I could have used a ball bearing, and not have to have done all that, then I would. Sometimes they just don't fit where you want them to.

If you already have the bronze bearings made and installed, then I probably wouldn't go to the trouble of changing it up. A few drops of oil, once a day, should lube it adequately.
John Hasler
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Re: Needle bearings, on axles.

Post by John Hasler »

rudd wrote: Wed Jun 17, 2020 7:58 pm On the bearing races, rather than sleeves on the axle, how about boring the end of the axle and pressing in purchased hardened dowel pins? (axle is shorter of course)
That would create a stress concentration at the step where the pin goes into the axle. The pin diameter would need to be large enough to handle that stress. Since it has to be significantly smaller than the axle that might not be possible. You would want to do the calculations before committing to that solution.
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Steggy
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Re: Needle bearings, on axles.

Post by Steggy »

John Hasler wrote: Thu Jun 18, 2020 8:07 am
rudd wrote: Wed Jun 17, 2020 7:58 pmOn the bearing races, rather than sleeves on the axle, how about boring the end of the axle and pressing in purchased hardened dowel pins? (axle is shorter of course)
That would create a stress concentration at the step where the pin goes into the axle. The pin diameter would need to be large enough to handle that stress. Since it has to be significantly smaller than the axle that might not be possible. You would want to do the calculations before committing to that solution.
Something else to be considered is dowel pins are very slightly oversized relative to the nominal dimension. Depending on the needle bearing being used, the fit may be too tight to permit assembly.
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Pontiacguy1
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Re: Needle bearings, on axles.

Post by Pontiacguy1 »

Bill Conner did exactly that: used a pressed in long dowel pin with a needle bearing running directly on the pin. He did that on all of his trucks that he made, and I know of many of them that are over 40 years old and still going strong. He used a long pin so it would go way down into the axle very deep, not sure how long, though, or whether it was pressed or loctited. It was maybe 1/2" diameter. Used a drawn cup roller bearing pressed into the journal box. His were an arch bar style of truck but was all welded together. It didn't have that prototype look, but they were durable and were known to last a long time. Like I said, he had built many, many sets of them and as far back as the mid 1970s.

Wish I had a picture to show you. Some drawings would be really nice. I don't know the exact sizes or the assembly details of his trucks, but I know that using a long dowel pin was exactly what he did and they were known to be tough and super-reliable.
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Harold_V
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Re: Needle bearings, on axles.

Post by Harold_V »

BigDumbDinosaur wrote: Thu Jun 18, 2020 12:13 pm Something else to be considered is dowel pins are very slightly oversized relative to the nominal dimension. Depending on the needle bearing being used, the fit may be too tight to permit assembly.
Correct! Typically by .0002". That miniscule amount could be easily polished to be removed. Polishing (done properly) would offer a finer surface finish in the bargain.

H
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Greg_Lewis
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Re: Needle bearings, on axles.

Post by Greg_Lewis »

Just thinking.... has anyone used cam followers for this? It's the dowel pin solution with the bearing included. https://www.mcmaster.com/am-follower
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RET
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Re: Needle bearings, on axles.

Post by RET »

Hi,

To answer the original question, unless there is something wrong with the original setup, there isn't any real advantage to going with needle bearings in that application. You say the trailing truck has "caps" on the top of the axles and nothing on the bottom. What would be a good thing to do is to add a "cellar" underneath the axle that would hold a felt wick to bear on the underside of the axle with some means of adding oil to the felt in the cellar. This is similar to axle boxes in full size practice.

Where needle bearings are concerned, for our models a hardened axle isn't really necessary. I used needle bearings in "DART," a 7 1/4" gauge 0-4-2 tank locomotive designed by Martin Evans. The bearings I used are Torrington #B-1612 which is 1" bore x 3/4" wide x 1 1/4" O.D. I am running them on a mild steel axle.

The reason I am doing things this way is because the dynamic load for ONE bearing is 3,700 pounds and the static load is 11,400 pounds and a working load is given as 6,110 pounds (a little over 3 tons!). Remember, this is for ONE bearing!

The finished locomotive will weigh somewhere between 250 and 300 pounds which is spread over four of these bearings plus the trailing axle which is supported by plain bronze bearings. The above information comes from the Torrington service catalog.

For our models, rolling element bearings can be very helpful if they are used right. Loads will be very small compared to the capacity of the bearing (remember the square-cube law!). What is important however, is that dirt is kept out of the bearing. A plain bearing can handle dirt and grit much better than a rolling element bearing. While the idea is a little bit unconventional, the best way to lubricate a needle bearing is to drill a hole in the end of the axle, tap the hole and then drill a cross hole in the axle where the bearing will be on assembly.

Finally, fabricate an adapter that has a grease fitting at one end and the other end threaded to match the thread in the axle. When you hook up a grease gun to the end of the adapter, the grease will go directly into the center of the bearing and it will push any old grease and dirt out of the bearing, thus both lubricating the bearing and keeping it clean. Set up in this way, the bearings should last almost forever.

Greg,
Possible, but I think in most applications, it would take up too much room (more room than a needle bearing). The cam follower would be a press fit in the axlebox, right? The big advantage a needle bearing has is that it carries a large load in a small space.

Richard Trounce.
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