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 Post subject: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 10:55 am 

Joined: Tue Sep 14, 2004 7:52 am
Posts: 1464
Location: Strasburg, PA
Saw this video and had to pass it along. It seems to show a lack of understanding that static friction between the drivers gripping the rail is always more that kinetic friction of drivers spinning on the rail. Holy crap, I’m glad that’s not my locomotive (or my track)! You can actually see dynamic augment in action at around 1:19.

Thanks to kwilcomb on the Narrow Gauge Discussion Forum for originally posting this.

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 Post subject: Re: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 11:30 am 

Joined: Sun Aug 22, 2004 3:37 pm
Posts: 1103
Location: Pacific, MO
Don't they have sand on British locos? What is all the steam coming out around the drivers? I don't understand everything I see here. Other than very excessive slipping.
Maybe they should put aluminum oxide tires on her and do some rail grinding while they're out.


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 Post subject: Re: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 11:36 am 

Joined: Tue Sep 14, 2004 7:52 am
Posts: 1464
Location: Strasburg, PA
I understand the British sanders run on steam, rather than air. I was thinking that the spot where she first let go was where she ran out of sand, but I don't know.

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 Post subject: Re: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 12:13 pm 

Joined: Thu Aug 26, 2004 2:50 pm
Posts: 2341
Location: Northern Illinois
Is that engine superheated, with a dome throttle? It looks like he lost it with the units full of steam; finally decides at 1:25 to open the cylinder cocks and arrests the slip.

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 Post subject: Re: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 1:22 pm 

Joined: Fri Mar 26, 2010 11:43 am
Posts: 558
They were doing a burnout to get the tires hot for better grip. Just like at the drag strip.

Steam to deliver the sand seems like a bad idea. Always have a wet rail to keep things lubed up. Even worse if you run out of sand.


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 Post subject: Re: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 1:29 pm 

Joined: Thu Nov 22, 2007 5:46 am
Posts: 2528
Location: S.F. Bay Area
The British invented wheelslip, and remain the masters of the craft, clearly.
Didn't they recently destroy an engine by overspeed during a wheelslip event?


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 Post subject: Re: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 1:52 pm 

Joined: Fri Mar 26, 2010 11:43 am
Posts: 558
http://en.wikipedia.org/wiki/LNER_Peppercorn_Class_A2_60532_Blue_Peter
http://www.youtube.com/watch?v=YjsNbzg1UaI

That was nearly 20 years agao now, is that recent? That's 1/10th of the way or so back into the total history of the steam locomotive.

I think this latest video, they were just tired of continuously welded rail, and they are just putting the authentic clickety-clack back in the track.


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 Post subject: Re: Static Friction vs. Kinetic Friction
PostPosted: Tue May 14, 2013 4:54 pm 

Joined: Sun Aug 22, 2004 7:19 am
Posts: 5537
Location: southeastern USA
The more bits and pieces I pick up about tribology, the less I learn I know about it.....not always intuitively obvious.

British practice is a lot of oil lubing everything and steam wet-sanding......I'd imagine they would develop an early and extreme familiarity with wheel slip and how to control it.

dave

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