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 Post subject: Re: Question about Big Boy running gear
PostPosted: Wed May 08, 2019 10:18 pm 

Joined: Tue Sep 14, 2004 7:52 am
Posts: 1605
Location: Strasburg, PA
That's right. It's better to have rod bushings a little too loose, rather than a little too tight, or as the saying goes, "It's better to hear 'em than smell 'em."

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 Post subject: Re: Question about Big Boy running gear
PostPosted: Thu May 09, 2019 11:01 am 

Joined: Fri Feb 26, 2010 9:52 pm
Posts: 50
Yep...Steve Jackson always said it is good to have a little "grease slop"

MDR


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Thu May 09, 2019 11:57 am 

Joined: Fri Mar 05, 2010 3:41 am
Posts: 3516
Location: Inwood, W.Va.
Kelly Anderson wrote:
That's right. It's better to have rod bushings a little too loose, rather than a little too tight, or as the saying goes, "It's better to hear 'em than smell 'em."

I saw an older video on YouTube just the other day, in which Steve Lee was talking about operations with the 844. He commented that the UP had tried roller rods on two engines, and said they had been more trouble than they were worth, hence the choice to stay with solid bearings on later power.

A bit of speculation--I'm not positive, but I keep thinking the roller rods were on an older Pacific and a Mountain, a pair that had been streamlined in a very Art Deco style with one of the wildest, most colorful paint schemes you ever saw. I don't think it was likely those engines had cast frames. I also understand roller bearings don't like frames that flex too much.

I can't help but wonder if a cast bed would have made the difference.


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Thu May 09, 2019 1:30 pm 

Joined: Tue Sep 14, 2004 7:52 am
Posts: 1605
Location: Strasburg, PA
IIRC, the next, never built class of 4-8-4's were planned to have roller bearing rods, and four smoke stacks!

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Strasburg Rail Road Mechanical Department


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Thu May 09, 2019 9:19 pm 

Joined: Fri Aug 20, 2010 8:25 pm
Posts: 298
The problem with plain roller bearings on the rod ends is that the axis of each axle is not parallel at all times. As the engine goes over the track the axles twist relative to each other because of the spring equalization system that works to distribute the engines weight equally through all the axle bearings.

This causes the axis of each rod end to "diverge" from the axis of the pins on the wheels.

Plain roller bearings hate being diverged from the shaft (pin in this case) they are rotating about. It wears them out because the loads get extreme at one end of the pin and minimal at the other end of the pin.

Spherical roller bearings can accept the deviation between the axis of the pin and the axis of the bearing. Spherical roller bearings were expensive so they probably only used them where it was worth it (main rod ends). It was probably more cost effective to just use plain bushing on the other rod ends and replace them as they wore out.

I believe there were locomotives that had spherical roller bearing applied to the rod ends with very good success.

A plain bushing with some slop simply "wiggles" around the pin a bit to accept the two axes (pin and bearing) being out of alignment.

Also, that chain drive to the lubricator uses a "Roller Clutch". The expansion link rotates about plus minus 30 degrees, zero to plus 30 degrees then back to minus 30 degrees, back to plus 30 degrees, etc. But the lubricator input "gear" wants to rotate 360 degrees in the same direction all the time to power all the little oil delivery pistons.

The roller clutch moves the chain forward when the expansion link shaft rotates in one direction. And the roller clutch "releases" when the expansion link shaft rotates in the other direction.

If you watch the chain drive to the lubricator carefully you will see the chain go "forward' then pause while the expansion link rotates "back" for the next cycle. Then the chain goes "forward" again.

Just like the modern "ratchet wrench" except there are no "pawls" inside the roller clutch. The ID of the exterior housing of the roller clutch has a series of "ramps". When turning in the "right" direction little rollers jam up on those ramps and transmit rotation in one direction. When the input shaft rotates in the other direction the rollers "back off" the ramps and no power is transmitted.

The roller clutch is like an electrical diode (rectifier), mechanical force (electrons) only flow one way through the device.


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Thu May 09, 2019 9:48 pm 

Joined: Thu Apr 12, 2007 8:09 pm
Posts: 391
Who needs bearings anyway...

https://www.youtube.com/watch?v=bsHHzCP09xs


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Thu May 09, 2019 10:54 pm 

Joined: Mon Jan 17, 2005 9:06 pm
Posts: 2264
Location: Thomaston & White Plains
https://www.youtube.com/watch?v=bsHHzCP09xs

Sounds like Papa Boule arriving in Rive-Reine, with his 230..... "Four francs is four francs."

Howard P.

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 Post subject: Re: Question about Big Boy running gear
PostPosted: Fri May 10, 2019 1:59 am 

Joined: Sun Apr 02, 2017 3:13 am
Posts: 44
Ouch! What a horrible thing to do to a big end.

I'm going to Wolsztyn later this year. Looks like it will be the last year of regular operation; the drivers want to retire.

Some of the recent videos of 4014 have certainly got clunk-clunk-clunk rod noise.


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Fri May 10, 2019 9:54 am 

Joined: Thu Aug 26, 2004 2:50 pm
Posts: 2398
Location: Northern Illinois
Nova55 wrote:


Sounds like the last years at Northwestern Steel & Wire.

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 Post subject: Re: Question about Big Boy running gear
PostPosted: Fri May 10, 2019 3:01 pm 

Joined: Sun Jun 17, 2007 8:03 pm
Posts: 941
Location: Warszawa, Polska
Nova55 wrote:


O K***A!

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 Post subject: Re: Question about Big Boy running gear
PostPosted: Fri May 10, 2019 4:14 pm 

Joined: Tue Sep 14, 2004 7:52 am
Posts: 1605
Location: Strasburg, PA
NYCRRson wrote:
Also, that chain drive to the lubricator uses a "Roller Clutch".

Nathan lubricators use a pawl and ratchet arrangement, FWIW.

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Strasburg Rail Road Mechanical Department


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Sun May 12, 2019 5:55 pm 

Joined: Sun Oct 15, 2017 7:58 pm
Posts: 77
Came across this on the net while looking for something else. Not my photo. Apologies for not writing down the source.
Nicely illustrates the chain drive to the lubricator, and the rod ends.


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Mon May 13, 2019 12:28 pm 

Joined: Sat Feb 11, 2006 10:42 am
Posts: 243
Location: Lancaster, PA
Hello,

Another feature in the photo which is curious, is that a cross-counterbalance weight hiding behind the big end of the eccentric rod?(which has a roller bearing for which Kelly wonders why...)

Looking at other resources on the web, if the right side leads the left on the BB, this potential c-cw is facing forward as the piston is full forward on the LH side......

Confirming this c-cw counteracts the yawing forces from piston thrust at high speed? I have see other threads on RYPN describing this but wanted to confirm my understanding.

Very good photo, most folks don't understand the scale of machinery on the BB, with a person included it drives it home.

They certainly have her clean.

Sincerely,

Randy


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Mon May 13, 2019 11:46 pm 

Joined: Thu Dec 12, 2013 1:26 pm
Posts: 88
The cross counterbalance weight at the 3 o'clock position (for a right side lead engine) as understand it, is to counterbalance the counterweight on the other side of the engine. The need for this is because, the counterweights and the side rods are in different vertical planes. I remember when they started to spin balance car tires years ago. Sort of the same thing. UP and Santa Fe were the only ones that I know of that used a separate weight, instead of tilting the counterweight slightly to the right on the main driver. On the Pennsy, it would have been to the left.


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 Post subject: Re: Question about Big Boy running gear
PostPosted: Tue May 14, 2019 7:54 pm 

Joined: Sat Feb 25, 2006 10:19 am
Posts: 51
Appreciate the answers to the clanking rods question.

Next one: why so much steam blow by on the front cylinder piston rod packing? The rear cylinders seems to be fine. Also noted some on 844. Is it a metallic packing that needs to wear in??

As so many have said, this rebuild is a serious and impressive achievement, both by the management of UP and especially the steam shop crew. Thank you all for making it possible.

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