Driver Thrust Bearing

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daves1459
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Re: Driver Thrust Bearing

Post by daves1459 »

Thank you everyone for your suggestions and insights. Good information.

I have also wondered why so much wear occurred over one summer with just 26 miles of travel. All running was done at one track that is a folded dog bone layout with a minimum radius 60 feet. One lap around the layout has about an equal amount of right and left hand curves. So far I have attributed the wear to incompatible materials (I.E.: Both parts soft leaded steel) and lack of adequate and/or proper lubrication. There is no measurable wear on the drive steel tire tread or flanges. However, I am not the original builder, just the restorer. When setting everything up last winter I measured the rear left journal pedestal to be .012" further rearward than the right from the front axle. At the time I passed it off as insignificant due the long axle spread of an old time 4-4-0. I machined the side rod bores accordingly. In retrospect maybe I should modify the left rear journal to bring it back in parallel. Thoughts?

The original axle boxes were cast bronze, I don't know the alloy but by the shade of yellow color would guess silicon bronze, with half bearings on top and oil cellars on the bottom and wool felt waste wicking oil onto the axle as it rotated. So everything was well lubricated and there was no noticeable wear on the thrust surface. The reason I dropped the axles last winter was to respring the drivers as I had added nearly 70 pounds of lead in the cab and elsewhere causing the leaf springs to collapse and the journals were riding on the frame. When I was cleaning the journals I found significant wearing in the journal bearing area with scoring beginning. The axles were only 3/4" diameter, I concluded they were over loaded. I have used guided needle type roller bearing before in other locos with complete sucess, so decided to make retrofit.

I have dropped the front axle and there is similar wear, But not so much, more in the range of .003" to .004". Still a lot for one summer.

I like the idea of grease cavities inside of the axle ends and can make the modification. My only dilemma is how to get a 1/16" diameter hole through the Rockwell "C" 58 journal sleeve. I don't have access to EDM. Any suggestions?

I going to stay with the guided (not full compliment) needle roller bearings. I had used two 1/2" wide bearing per journal as I was once told that would prevent roller skewing. But, now I wonder if I would be better off with one 1" wide bearing. Thoughts?

Thanks again, Dave
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Greg_Lewis
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Re: Driver Thrust Bearing

Post by Greg_Lewis »

It might be worthwhile to have someone EDM the holes for you. There is the possibility of a carbide spade bit, but at 1/16, that would be scary. All you'd need would be to break the bit in the hole and have a big headache. I think that there are needle bearing races with pre-drilled holes, if you will be replacing those races.
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Bill Shields
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Re: Driver Thrust Bearing

Post by Bill Shields »

This is not a RRSC loco from the 1980's is it?

Your axle spacing problem sounds very familiar.

Major concern before you do anything is

Are the axles parallel front to back and are they square with the frame? If not...fix that before you do anything else. -> been there done that...fixed that problem

What is the side to side clearance of driver in frame?

Hole up the center is also going to require tapping to put in a plug to keep dirt out...plus ability to drill a cross hole through the axle for the lube. EDM drill can make the holes...but not threads.

+70# in the cab is a lot of extra weight. What is weight on driver's now?
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daves1459
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Re: Driver Thrust Bearing

Post by daves1459 »

The loco is Disney 4-4-0 design and castings dating from 1953.

I do not know if the axles are square to frame. But, now that is a concern will find out. The axles are out of parallel by the .012" I mentioned.

The front axle with valve eccentrics has about .025 side clearance, .0125" per side. The rear axle has about .050" side clearance.

Machine work on end of the axles is no problem. I will make a sort of hub cap that looks like the axle end with a hole to insert lube then plugged with a set screw. My only issue is getting the cross hole in the hardened journal sleeve. I'll probably end up finding an EDM shop to put in the cross holes.

I did not weigh all of the lead. I should have said 60 to 70 pounds. I do know that two 20 pounds bars were put in the cab. Then 10 pounds in the sand dome and 10+ pounds of 3/16" sheet lead wrapped around the boiler barrel. I don't know the weight per driver axle. Some of the boiler barrel and sand dome weight is on the lead truck. Obviously, the wait is for traction as without it the loco was very slippery. The loco tracks very well and does not nose or waddle. The original driver springs were made of spring temper phosphor bronze which is 60% as stiff as steel. I simply made replacement top leaves of steel to bring the journals back to design running position.

Dave
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cbrew
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Re: Driver Thrust Bearing

Post by cbrew »

Morning Dave, one thing you need to also look at, make sure the locomotive is sitting level on her springs. if one side is lower then the other, that will quickly eat up .025 with the journal misalignment. that is too tight imho.
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Bill Shields
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Re: Driver Thrust Bearing

Post by Bill Shields »

I would look at front axle travel side to side and track radius

From my experience I think your driver side to side is a bit on the tight side...and you may be binding on corners if you do not have enough lead truck side travel.

Question...before you added the extra weight ...we're you having trouble with derailing in turns?
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daves1459
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Re: Driver Thrust Bearing

Post by daves1459 »

Bill Shields wrote: Wed Jan 19, 2022 10:39 am I would look at front axle travel side to side and track radius

From my experience I think your driver side to side is a bit on the tight side...and you may be binding on corners if you do not have enough lead truck side travel.

Question...before you added the extra weight ...we're you having trouble with derailing in turns?
No it has always tracked well. It has a swing link lead truck that guides the loco very well.

Regarding side to side: Wouldn't it be desirerable to keep main axle side play on the small side to reduce side loads on the main rods and crossheads along with the valve gear eccentric rods?

Dave
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Bill Shields
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Re: Driver Thrust Bearing

Post by Bill Shields »

You have to allow enough side to side that things do not bind...which is why I asked about the lead truck and curve radius...and side to side rod play should be allowed for everywhere.

Remember...not building a watch and with a lot of steamers...just about worn out is about right

Problems may well go away with proper thrust bearings...just do not make any tighter than you have mentioned...since based on my experience you are borderline tight already.
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cbrew
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Re: Driver Thrust Bearing

Post by cbrew »

To add what Bill is saying, the running gear needs to be designed to run over very uneven track. the most successful locomotives have been built with very loose clearances but garage hacks playing on machine tools. while on the flip side, I have seen locomotives built by engineers that held to extreme tolerances roll about 25 feet off the steaming bay and slide to a stop.
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Bill Shields
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Re: Driver Thrust Bearing

Post by Bill Shields »

Or run just fine on compressed air and sieze up on steam.

There are times when being a blacksmith has its advantages.
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Berkman
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Re: Driver Thrust Bearing

Post by Berkman »

Most 7.5 scale locos and full size locomotives don't have thrust bearings, and just rely on the hub liners for lateral wear. Like Bill says, you could easily end up with a locomotive that is too tight laterally if you add a thrust bearing without making other adjustments etc.

I can't think of a single locomotive from RRSC, Little engines etc that have thrust bearings on the axles. happy to be corrected if wrong.
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Harold_V
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Re: Driver Thrust Bearing

Post by Harold_V »

I don't mean to belittle the comments in regards to tolerances, but what has been stated is not true. Readers need to learn the difference between tolerance and clearance. It imply that building an engine to tight tolerance do not operate well is wrong, and at some point in time must stop.
The harsh reality is an engine built to stringent (tight) tolerance is more likely to perform properly than one that is not. If proper clearance is provided, in company with tight tolerance, the required fits are guaranteed. If, on the other hand, clearance is provided, but tolerance is too loose, it may or may not function, depending on which side of the tolerance is used.

What is it going to take to get people to stop talking about tolerance when clearance is the point?

This is a good opportunity for folks to become better informed, so they sound like they know what they're talking about.

Tolerance is the amount one can deviate from a desired dimension. It does not mean proper clearance.

H
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