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Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

May 03, 2017 08:40PM avatar
From Jeff Frost, Backyard Railroading group

Has anyone else heard the claim that a 4-8-8-4 could pull a train more than 5 miles long?

As far as I can tell, this is based off of theory. On a straight level grade, there is only 4 lbs/ton resistance so a Big Boy with 135,375 lbs of tractive effort, they could haul a 33,843 ton train on straight level track. Engine and tender weigh 625 tons leaving the trailing tonnage at 33,218 tons. That would be 738x 45 ton cars. If a 45 ton car is 38' long, the cars would be 28,050 feet long, which is 5.3 miles.

Now if the train heads up a very shallow 0.2% grade around a 2 degree curve, the total weight to be pulled on this track would be 16,590 tons, giving a trailing weight of 15965 tons. This would be 354x 45 ton cars at 38' long would be 2.55 miles long.

If the train were to head up a 1% grade with a 4 degree curve, the total weight that can be pulled is 4,977 tons which gives a trailing weight of 4,352 tons. That would be 96x 45 ton cars at 38' long would be 0.69 miles long.
thanks
****************************************************************************
To figure out max tonnage it is tractive effort / resistance.
Resistance:
4 lbs/ton resistance for straight level track

plus 20 lbs/ton per % grade resistance

plus 0.8 lbs/ton per degree of curvature to figure out maximum tonnage.

To figure out how long the train is I used an estimate/average weight of a car being 45 tons and 38' long (they were 40-50 tons, 36-40' long in the days of steam).

**************************************************************************
The rating on straight level track is just a statistical number and means nothing in real live. A straight 0.2% upgrade (2.4" rise over 100') cuts the train down to 50% of its tonnage on straight level track.

A straight 1% grade cuts a train down to 16.6% of the weight on straight level track.

A 1.2% grade on a 5 degree curve cuts the train down to 12.5% of what it can pull on straight level track.

A 2% grade on a 5 degree curve cuts the train down to 8.3% of what it can pull on straight level track.


The calculations for how much a steam locomotive can pull and the estimates for resistance apply to the live steam hobby too. By using the tractive effort of a steamer, 4 lbs/ton resistance for straight level track, 20 lbs/ton resistance per % grade and 0.8 lbs/ton resistance per degree of curvature, the calculated maximum train weight can be determined.

The degree of curvature is how many degrees the track turns across a 100' chord.

To figure out the degree of curvature, the formula is 2sin(50/radius). A 50' radius is a 180 degree curve. A radius smaller than 50' is not able to be computed as a degree of curvature.

So Russ adds:
A SVRy 2-6-6-2 has 42,100 pounds TE = 425- 25 ton 30' flat cars on the level= 2.4 mile long narrow gauge train!

On the 1.5% grade and 16 degree curves between Baker and Sumpter it could (theoretically) pull 34 cars but up the 4% grade and 16 degree curves to Larch it would be down to 17 cars.

Really something how grades and curves effect load...

Here is one working in Guatemala.
25857030160_2279284dff_o.jpg

Russell Courtenay
Idaho, USA
Subject Author Posted

Can a Big Boy pull a 5 mile long train? (Some Sumpter content) Attachments

UnknownIdaho May 03, 2017 08:40PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

dougvv May 03, 2017 09:44PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

Kelly Anderson May 05, 2017 05:27AM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content) Attachments

bcp May 03, 2017 09:55PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

UnknownIdaho May 03, 2017 11:37PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

Chris Walker May 04, 2017 01:03AM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

Tomstp May 04, 2017 06:45AM

Re: "I Think I Can . . . "

Russo Loco May 04, 2017 03:16PM

Re: "I Think I Can . . . "

Tomstp May 05, 2017 02:22PM

A booster question

CharlieMcCandless May 05, 2017 04:23PM

Re: A booster question

Bruce R. Pier May 05, 2017 06:35PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

jim pallow May 04, 2017 11:37AM

Take the 4014 to Alamosa

CharlieMcCandless May 04, 2017 02:34PM

Re: Take the 4014 to Alamosa

Earl May 05, 2017 05:44AM

Re: Take the 4014 to Alamosa

Tomstp May 05, 2017 02:23PM

Re: Take the 4014 to Alamosa

Earl May 05, 2017 05:52PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

bcp May 05, 2017 05:57PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

et&wnc May 05, 2017 03:43PM

Re: Can a Big Boy pull a 5 mile long train? (Some math content)

Russo Loco May 06, 2017 11:39AM

Re: Can a Big Boy pull a 5 mile long train? (Some math content)

dougvv May 06, 2017 05:02PM

Re: Can a Big Boy pull a 5 mile long train? (Some math content)

John Cole May 08, 2017 08:01AM

Re: Can a Big Boy pull a 5 mile long train? (Some math content)

Kelly Anderson May 08, 2017 08:09AM

Re: Can a Big Boy pull a 5 mile long train? (Some math content)

John Cole May 08, 2017 08:32AM

Re: Can a Big Boy pull a 5 mile long train? (Some math content)

dougvv May 08, 2017 08:57AM

Re: Can a Big Boy pull a 5 mile long train? (Some math content)

kcsivils May 08, 2017 10:52AM

Re: NNG(Some math content)

Chris Walker May 08, 2017 01:26PM

Re: NNG(Some math content)

CharlieMcCandless May 09, 2017 06:36AM

Re: NNG(Some math content)

John Cole May 09, 2017 03:56PM

Re: NNG(Some math content)

CharlieMcCandless May 09, 2017 06:35PM

Re: NNG(Some math content)

CharlieMcCandless May 09, 2017 06:37PM

Re: NNG(Some math content)

dougvv May 10, 2017 03:01AM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

Tomstp May 06, 2017 08:40AM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

Bruce R. Pier May 06, 2017 10:55AM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content) Attachments

Tomstp May 12, 2017 06:41PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

Tom Moungovan May 13, 2017 09:58PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

Tomstp May 15, 2017 03:13PM

Re: Can a Big Boy pull a 5 mile long train? (Some Sumpter content)

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