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Was there ever a modern 4-8-4

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Was there ever a modern 4-8-4
Posted by Anonymous on Tuesday, July 15, 2008 5:08 PM

I am looking for the article in Trains magazine by that name and need to know what issue it was in.  If you can help me out, thanks.

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Posted by scottychaos on Tuesday, July 15, 2008 10:15 PM

are you sure thats the right title? because it doesnt make any sense..

All 4-8-4's were modern..very modern...as modern as it gets..

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Was there ever a super 4-8-4?
Posted by nanaimo73 on Wednesday, July 16, 2008 2:04 AM
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Posted by scottychaos on Wednesday, July 16, 2008 6:23 AM

ah! thanks Dale..thats different! :) there is a big difference between "Was there ever a super 4-8-4?" and "Was there ever a modern 4-8-4?".."modern" and "super" have very specific meanings when it comes to late steam..

I havent read the article, but werent quite a few 4-8-4's considered "Super Power"?

especially engines like the DL&W Poconos and the N&W J-class..and plenty more..

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Posted by wjstix on Wednesday, July 16, 2008 9:23 AM

Generally "super power" referred to any engine that had a large firebox requiring a four-wheel trailing truck to haul it, usually along other modern things like roller bearings, larger drive wheels for higher speed service etc. So really it would be hard to come up with a 4-8-4, 2-8-4, 2-10-4 etc. that wouldn't be considered "super power".

So I wonder what the article is actually referring to by "super 4-8-4"??

Confused [%-)]

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Posted by scottychaos on Wednesday, July 16, 2008 9:36 AM

the beginning of "Super Power" is generally attributed to Lima and their Berkshires of the 1920's.

Although the first "super power" locos were Lima 2-8-2's..then Lima took the concept a step further with the larger firebox, requiring the 4-wheel trailing truck, and inventing the Super Power Berkshire.

but yeah, im confused by this Trains magazine story too..because it seems virtually all 4-8-4's would have fallen under the "super power" umbrella..and there certaintly cant be any question around "Was there ever a super 4-8-4?"..the answer is very obviously "yes"..

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Posted by nanaimo73 on Wednesday, July 16, 2008 9:57 AM

It is a 6 page article by Robert Le Massena comparing the 1119 4-8-4s and 53 4-4-4-4 locomotives, to see if there was a "super 4-8-4" that was better than the others. The criterion used included grate area, combustion chamber, boiler diameter, steam pressure, firebox type (radial, Belpaire, watertube), feedwater heater, poppet valves, booster and roller bearings.

The concluding two paragraphs-

  One can only guess what No. 5500 might have done if it had been given the same qualities of fuel as had been burned in No. 6023's firebox. A 15 percent increase in maximum drawbar horsepower (to 5750) is perhaps optimistic, but 5500 DBHP - what the designers had intended - was within reason.
  There seems to be little room for doubt that the 5500 came closer to being a super 4-8-4 than any other steam locomotive of its wheel arrangement. What it could have done, had it been equiped with a Belpaire firebox and a double Kylala-Kylchap exhaust, is a matter for fascinating conjecture.

There is a rebuttal to the article, a letter from John Ingles (David's dad?), at the back of the June 1975 issue.

I would be interested in feltonhill's and Tim Z's thoughts on the article.

Scotty, do you know which railroad the 5500 and 6023 were on?

PHOTO

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Posted by Anonymous on Wednesday, July 16, 2008 11:05 AM
Sorry about the name. I had just heard something about it somewhere and was interested to see the drawing and read the article.
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Posted by SSW9389 on Wednesday, July 16, 2008 2:35 PM
The article is talking about New York Cental's Niagaras built by ALCO 1945-1946. Richard Steinbrenner wrote about these locomotives in ALCO: A Centennial Remembrance pp. 234-237. 
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Posted by scottychaos on Wednesday, July 16, 2008 4:07 PM

interesting! I wish I had seen that article..

yes, the New York Central Niagaras were about as Super as they come!

The Niagaras along with the Norfolk & Western J-class and A-class are often considered the ultimate pinnacle of steam locomotive technology..they were as good as it ever got.

The 4-4-4-4's refered to in the article would have to be the PRR T1's then..

The NYC Niagaras were the height of NYC steam, and the T1's were the ultimate on the PRR.

PRR T1: http://www.northeast.railfan.net/images/tr_prr5541.jpg

Sadly, there are no surviving New York Central Niagaras or PRR T1's.. :(

There is however one surviving N&W J, the famous 611, and one N&W A-class. 

Scot 

 

 

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Posted by BigJim on Thursday, July 17, 2008 4:01 AM
Not to change the subject, but, also in that same issue was another good article on the FEC:
Where did the railroad go that once went to sea?

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Posted by feltonhill on Thursday, July 17, 2008 8:17 AM

Dale - Thanks for the mention!  I have the article and its reply.  I tend to agree with John Ingles' criticisms regarding lack of technical support information.  The comparisons seem a bit simplistic and miss the interaction between steam production (boiler) and energy conversion (steam circuit and running gear). 

My schedule is kind of crazy today and part of tomorrow, but I'd like to comment a bit on this article later.  I hope timz also gets into the discussion.

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Posted by timz on Saturday, July 19, 2008 5:27 PM

When somebody on the Web refers to an article or book, we who are curious about the subject tend to imagine the answers we're after would all be in the article, if only we could get a look at it. In this case, don't any sleep over the deprivation; the article is harmless enough, but it probably wouldn't tell you much you don't know already. Ingles' letter just reminded us that Le Massena wasn't any big expert.

Actually, tho, he throttled back on the pontification in this article, compared to some of his others. He proposed to arbitrarily define a "super 4-8-4" as an engine that could evaporate 100000 lb/hr, produce a (cylinder?) horsepower from 13 lb of steam, produce 6000 dbhp, haul 12 heavyweight sleepers up 1 1/2 percent at 60 mph, or 5000 tons at 60 mph on the level. Then he tried to guess whether such an engine could or did exist. (The 12 sleepers at 60 mph on 1.5% was a miscalculation.)

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Posted by dmoore74 on Sunday, July 20, 2008 7:28 PM
 santafe347 wrote:

I am looking for the article in Trains magazine by that name and need to know what issue it was in.  If you can help me out, thanks.

There was an article in Steam Glory published as ClassicTrains Special Edition No. 2 in 2004 on Union Pacific's  800 series 4-8-4's.  The final part of the article deals with A.H. Fetters, UP's chief locomotive designer, instructing Otto Jabelmann of the Research and Mechanical Standards Department to come up with a design for a Super 800 for post WWII use.  A drawing and proposed specifications are included.

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Posted by JT22CW on Sunday, July 20, 2008 7:38 PM
Couldn't let this thread go by without mentioning C&O's Greenbrier class (eg. 614), these actually built by Lima, the purveyors of "super power".
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Posted by GP40-2 on Monday, July 21, 2008 5:56 PM
 JT22CW wrote:
Couldn't let this thread go by without mentioning C&O's Greenbrier class (eg. 614), these actually built by Lima, the purveyors of "super power".


There have been a number of new videos of the 614 showing up on YouTube lately.

Here's two showing the 614 with a 22 car train at close to 80 MPH:

youtube.com/watch?v=AhGoR1cpdrM&feature=related

youtube.com/watch?v=r0R9PkVB244&feature=related

This one shows the 614 with 25 cars at speed from the Chessie Steam Special days on the high speed B&O main in Maryland:
http://www.youtube.com/watch?v=lAQwPc4JmS4&feature=related
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Posted by sr4501 on Monday, July 21, 2008 9:20 PM
what's up with 614, is Ross really trying to convert to bio fuelDead [xx(]
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Posted by feltonhill on Tuesday, July 22, 2008 5:53 AM

The article, Was There Ever a Super 4-8-4?, is an opinion piece and as such, the author can come to any conclusion he wants. There's no right or wrong. However, there can be differences of opinion!

I have the following observations after reading the article again, and doing a bit of research to support my objections. That's what took so long.

100,000 lbs of steam/hr out of a 4-8-4 is asking a lot over the road. The only 8-drivered passenger locos I know of that ever accomplished that in documented test results are the N&W J (104,946 lbs/hr total evaporation) and PRR T1 (105,475 lbs/hr total evaporation). The Niagaras and the ATSF 2900's may have also managed it but I've not found any test report that confirms such a figure. BTW, total evaporation consists of tank water plus condensate from the FWH; it is not the same as equivalent evaporation. Be careful to watch for the adjective, or lack of it.

I agree with timz that 13 lbs of steam per unspecified type of HP-hr is likely based on indicated HP. The PRR T1 managed the lowest documented ratio, 13.6 lbs steam per IHP-hr (Test 1428, 76 mph). The lowest for the Niagara is 13.72 lbs per IHP-hr (Test 129, 11 cars, 65.2 mph). Very close, but not 13.

60 mph with 12 heavyweight cars (est 1,100 tons) on 1.5% requires about 6,300 DBHP. I doubt any 4-8-4 could manage this, super or not.

The Belpaire firebox has always been a mystery to me. I've heard this 20-25% assertion before from other sources, but I've never understood how it could generate more steam just because of its square-topped design. Heat transfer takes place from the firebox through the firebox wrapper to the surrounding water. This is not dependent of the firebox type. Steam is collected above the surface of the water over the crown sheet. However, the Belpaire does provide a larger volume of steam above the crown sheet. That's apparent in any cross section. Maybe this is what the proponents have in mind. One of the other advantages is that the staybolts holding the firebox to the boiler shell are stressed more conventionally in a Belpaire. The top and crown sheets are virtually parallel, so there's no odd angle between the staybolt heads and the top of the boiler. This likely reduced maintenance costs.

The author mentions GN's comparative tests between its two classes of 4-8-4's as a source for his 20-25% figures. IMO, any comparison based on the S-1 and S-2 would be very suspect. The S-1 had a larger firebox and boiler than the S-2, so one would expect that it would generate more steam more economically with respect to coal consumption that the smaller loco. It's not an equitable basis for comparison.

I believe the Kylala-Kylchap exhaust term is inaccurate. Kylala was a Finnish engineer; Chapelon was a French engineer. The Kylchap exhaust incorporated features from both designers. The hyphenated term is redundant, AFAIK.

So which 4-8-4 came closest? Using LeMassena's standards without change (this doesn't indicate I agree with them), both the N&W J (#602) and PRR T1 (#6111) met seven criteria, a tie for first place. NYC S2 5500 met six criteria, second place. ATSF 2900s and NYC Niagaras met five criteria, a tie for third place. If the booster criterion is excluded, the N&W J, PRR T1 and NYC S2 meet six criteria, a three-way tie for first place. The ATSF 2900s and NYC Niagaras still meet five criteria, a tie for second place.

As far as comparing DBHP figures between these locomotives, it's not really possible, in spite of the fact that many do it all the time. For some reason, the ATSF 2900's did not test very high at least in the limited info I have. Maybe the steam circuit pressure loss that affected the 3776 class wasn't resolved.

Between the N&W J, NYC Niagaras and PRR T1, comparisons are very difficult. It's easiest to compare the T1 with the Niagara. Detailed test data survive for each of these, and they were rigorously examined and pushed to their limits both on the road (NYC, PRR) and on the Altoona test plant (T1 only). An exceptional comparison of these two locomotives has been written by Philip Atkins in his book, Dropping the Fire. I believe its still available.

Now comes the fun part. The figures often quoted figures for the N&W J (usually 5,028 DBHP at 41 mph) were made during constant speed tests to determine the economies of raising the BP to 300 psi. During the 300 psi runs, the J was deliberately "hooked up" in order to match the 40-mph limit imposed on the tests by the curves on Christiansburg hill. The 5,028 figure is not a maximum, and N&W so stated in its test report. Further, the curve used for DBHP above 40 mph is a theoretical curve, not actual. N&W also stated this in the test report. As a result, we don't know what the maximum DBHP figure would have been for a J if it had been tested the same way as the Niagara and T1.

IMO, it doesn't seem reasonable to compare two locomotives giving it everything they've got (Niagara, T1) with a locomotive that's being operated at a shorter cutoff and constant speed for economy tests (J).

It was an interesting article, but the criticisms raised by John Ingles regarding lack of support for many of the conclusions is justified. The author needed to make his comparisons more carefully and document his opinions more thoroughly.

Afraid this is way too long and much too late, but here ‘tis for those who are still interested.

 (corrected 8/2/08)

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Posted by feltonhill on Tuesday, July 22, 2008 6:07 AM

GP40-2 - Have some videos of 614 on NJT and it's always good to revisit the high speed running with a substantial train! 

As a matter of interest, several modifications to 614 were proposed by David Wardale in 1983,  before the ACE tests in 1985.  They're listed in his book, The Red Devil and Other Tales From the Age of Steam (pg386), and include, among other things, triple Lempor exhaust, FWH, larger valves, and revised valve timing.

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Posted by scottychaos on Tuesday, July 22, 2008 6:47 AM

It sounds like the author of that (Trains magazine) article completely re-defined, on a whim, the defination of "Super Power", creating his own defination for the purposes of the article..rather irresponsible IMO...because we all know that Super Power 4-8-4's existed..in fact, probably EVERY 4-8-4 ever built fit the defination..so the whole point of the article is rather pointless IMO..

Its like writing a magazine article to solve the big unknown mysteries of: "Did the New York Central ever use 4-6-4 Hudsons?, we investigate!" or "Did the PRR ever use Pacifics in passenger service? mystery now solved!" ;)

While there might not be one "all encompasing" accepted defination of "super power"..I think we can all agree that the concept was developed by Lima and is best known from their Berkshires of the 1920's...ALL of the modern 4-8-4's are direct evolutionary decendants of those Berkshires, and are even MORE advanced than those Berkshires, incorporating all the features of those Berkshires, which makes them automatically "super power" by birth..and even MORE "super" than the first "Super Power" engines..

http://en.wikipedia.org/wiki/Lima_Locomotive_Works

Perhaps he should have been looking for "SUPER Super Power" or "ULTRA Super Power"..at least then we would all know what he was going for...Calling the article "Was there ever a Super 4-8-4?" doesnt quite work..How about "Searching for the Ultimate 4-8-4!" as a title..that would have worked..

Scot

 

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The most powerful 4-8-4?
Posted by nanaimo73 on Tuesday, July 22, 2008 9:34 AM

feltonhill, thanks for the post. Interesting stuff!

 feltonhill wrote:

As a matter of interest, several modifications to 614 were proposed by David Wardale in 1983,  before the ACE tests in 1985.  They're listed in his book, The Red Devil and Other Tales From the Age of Steam (pg386), and include, among other things, triple Lempor exhaust, FWH, larger valves, and revised valve timing.

Do you have any idea of what the DBHP would have worked out to?

Dale
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Posted by timz on Tuesday, July 22, 2008 1:06 PM

 feltonhill wrote:
60 mph with 12 heavyweight cars (est 1,100 tons) on 1.5% requires about 6,300 DBHP.

Strictly speaking that may be true, but it needs clarification. To produce 6300 dbhp at 60 mph on a 1.5% upgrade the engine would have to be capable of producing well over 8000 dbhp at 60 mph on the level-- which was what Le Massena forgot.

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Posted by timz on Tuesday, July 22, 2008 1:16 PM

 scottychaos wrote:
It sounds like the author of that (Trains magazine) article completely re-defined, on a whim, the defination of "Super Power", creating his own defination for the purposes of the article..rather irresponsible IMO...because we all know that Super Power 4-8-4's existed..in fact, probably EVERY 4-8-4 ever built fit the defination...

... 

ALL of the modern 4-8-4's are direct evolutionary decendants of those Berkshires, and are even MORE advanced than those Berkshires, incorporating all the features of those Berkshires, which makes them automatically "super power" by birth

I'm guessing it never occurred to him that any confusion would arise. Lima coined the term "Super Power" to use in their advertising, but after 1930 did any railroaders care which engines were or weren't "Super Power"? I'd say the term appeared in railfan historical publications but was irrelevant to the railroads, which didn't bother with it.

Some would say limited cutoff was a "Super Power" feature, which many? most? 4-8-4s lacked. Ditto tandem main rods.

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Posted by BDT in Minnesota on Thursday, July 31, 2008 11:38 PM
 feltonhill wrote:

The article, Was There Ever a Super 4-8-4?, is an opinion piece and as such, the author can come to any conclusion he wants. There's no right or wrong. However, there can be differences of opinion!

I have the following observations after reading the article again, and doing a bit of research to support my objections. That's what took so long.

100,000 lbs of steam/hr out of a 4-8-4 is asking a lot over the road. The only 8-drivered passenger locos I know of that ever accomplished that in documented test results are the N&W J (104,946 lbs/hr total evaporation) and PRR T1 (105,475 lbs/hr total evaporation). The Niagaras and the ATSF 2900's may have also managed it but I've not found any test report that confirms such a figure. BTW, total evaporation consists of tank water plus condensate from the FWH; it is not the same as equivalent evaporation. Be careful to watch for the adjective, or lack of it.

I agree with timz that 13 lbs of steam per unspecified type of HP-hr is likely based on indicated HP. The PRR T1 managed the lowest documented ratio, 13.6 lbs steam per IHP-hr (Test 1428, 76 mph). The lowest for the Niagara is 13.72 lbs per IHP-hr (Test 129, 11 cars, 65.2 mph). Very close, but not 13.

60 mph with 12 heavyweight cars (est 1,100 tons) on 1.5% requires about 6,300 DBHP. I doubt any 4-8-4 could manage this, super or not.

The Belpaire firebox has always been a mystery to me. I've heard this 20-25% assertion before from other sources, but I've never understood how it could generate more steam just because of its square-topped design. Heat transfer takes place from the firebox through the firebox wrapper to the surrounding water. This is not dependent of the firebox type. Steam is collected above the surface of the water over the crown sheet. However, the Belpaire does provide a larger volume of steam above the crown sheet. That's apparent in any cross section. Maybe this is what the proponents have in mind. One of the other advantages is that the staybolts holding the firebox to the boiler shell are stressed more conventionally in a Belpaire. The top and crown sheets are virtually parallel, so there's no odd angle between the staybolt heads and the top of the boiler. This likely reduced maintenance costs.

The author mentions GN's comparative tests between its two classes of 4-8-4's as a source for his 20-25% figures. IMO, any comparison based on the R-1 and R-2 would be very suspect. The R-1 had a larger firebox and boiler than the R-2, so one would expect that it would generate more steam more economically with respect to coal consumption that the smaller loco. It's not an equitable basis for comparison.

I believe the Kylala-Kylchap exhaust term is inaccurate. Kylala was a Finnish engineer; Chapelon was a French engineer. The Kylchap exhaust incorporated features from both designers. The hyphenated term is redundant, AFAIK.

So which 4-8-4 came closest? Using LeMassena's standards without change (this doesn't indicate I agree with them), both the N&W J (#602) and PRR T1 (#6111) met seven criteria, a tie for first place. NYC S2 5500 met six criteria, second place. ATSF 2900s and NYC Niagaras met five criteria, a tie for third place. If the booster criterion is excluded, the N&W J, PRR T1 and NYC S2 meet six criteria, a three-way tie for first place. The ATSF 2900s and NYC Niagaras still meet five criteria, a tie for second place.

As far as comparing DBHP figures between these locomotives, it's not really possible, in spite of the fact that many do it all the time. For some reason, the ATSF 2900's did not test very high at least in the limited info I have. Maybe the steam circuit pressure loss that affected the 3776 class wasn't resolved.

Between the N&W J, NYC Niagaras and PRR T1, comparisons are very difficult. It's easiest to compare the T1 with the Niagara. Detailed test data survive for each of these, and they were rigorously examined and pushed to their limits both on the road (NYC, PRR) and on the Altoona test plant (T1 only). An exceptional comparison of these two locomotives has been written by Philip Atkins in his book, Dropping the Fire. I believe its still available.

Now comes the fun part. The figures often quoted figures for the N&W J (usually 5,028 DBHP at 41 mph) were made during constant speed tests to determine the economies of raising the BP to 300 psi. During the 300 psi runs, the J was deliberately "hooked up" in order to match the 40-mph limit imposed on the tests by the curves on Christiansburg hill. The 5,028 figure is not a maximum, and N&W so stated in its test report. Further, the curve used for DBHP above 40 mph is a theoretical curve, not actual. N&W also stated this in the test report. As a result, we don't know what the maximum DBHP figure would have been for a J if it had been tested the same way as the Niagara and T1.

IMO, it doesn't seem reasonable to compare two locomotives giving it everything they've got (Niagara, T1) with a locomotive that's being operated at a shorter cutoff and constant speed for economy tests (J).

It was an interesting article, but the criticisms raised by John Ingles regarding lack of support for many of the conclusions is justified. The author needed to make his comparisons more carefully and document his opinions more thoroughly.

Afraid this is way too long and much too late, but here ‘tis for those who are still interested.

The class R1 and R2 Great Northern steam locomotives were 2-8-8-2 simple articulated locomotives....the S1 and S2 class locomotives were the 4-8-4 on the Great Northern...The class S1 consisted of six locomotives built by Baldwin in 1929.. They had a belpaire firebox and 73" drivers.. weight was 472,000 pounds and had a tractive effort of 68,500 pounds......The great Northern purchased the S1 locomotives for passenger service, but were reassigned to freight service...The 14 members of the S2 class also came from Baldwin, in 1930.. They differed from the S1 in that they had a radial-stay firebox, 80" drivers, weighed 50,000 pounds less, and had a tractive effort of 58,500 pounds...The S2 proved to be a fast passenger locomotive that suited the Great Northern's needs...

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Posted by feltonhill on Friday, August 1, 2008 8:45 AM

BDT - Thanks for the correction.  Have no idea what I was thinking about when I typed R-1 and R-2.  Absolutely, definitely meant S-1 and S-2.  The strange part is, I was looking right at the loco diagrams for both the 4-8-4's at the time.  I guess the R-2 diagram on the left page above the S-1 got mixed in.  Must have been one of those days....

Thanks again for the correction.  I hate to post misinformation like that.  Original post has been edited accordingly.

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Super 4-8-4
Posted by Anonymous on Sunday, August 3, 2008 3:45 PM
I am not sure now that you guys have said what this article is about if it is the one I am looking for.  I heard that there was a drawing in it of what a "Super 4-8-4" would have looked like.  If you know what article I am thinking of, please let me know.
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Posted by feltonhill on Sunday, August 3, 2008 8:09 PM
Feb 1975 Trains, top of pages 52-53.  There's a composite drawing of a super 4-8-4 which incorporates all of the author's recommended features.  This is the same article that was discussed earlier in this thread.
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Posted by Anonymous on Monday, August 4, 2008 4:07 PM

 feltonhill wrote:
Feb 1975 Trains, top of pages 52-53.  There's a composite drawing of a super 4-8-4 which incorporates all of the author's recommended features.  This is the same article that was discussed earlier in this thread.

Thanks.

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Posted by Paul Milenkovic on Tuesday, August 5, 2008 7:16 PM

I went to the Wisconsin State Historical Society to look at that article.

Yeah, yeah, the author gets tripped up on this Kylala-Klychap terminology for just plain Klychap for Andre Chapelon enhancing his exhaust system with a nozzle designed by Kylala of Finland.  Super Power encompassed a number of innovations, but advanced exhaust systems, discussed in other articles over the years in Trains, were not among them.

The interesting part that I didn't even see addressed in the article (maybe I need to read it again) was that the "dream Northern" had a siderod connected 4-axle tender booster.

Maybe we had this discussion before, but I guess the deal with boosters is the same thing as the deal with GM's FT 4-unit demonstrator: that platoon of Diesels may have had similar HP to a Northern, and yes, the FT had earlier model DC traction motors and electrical equipment with all manner of minimum continuous speed and short-term rating to worry about, but 16 axles were going to out pull 4 axles any day at low speeds, obviating the need for a helper.

Just what is the deal with boosters?  I understood that the usual arrangement was to drive a single trailing truck axle, but I have seen the rare picture of siderods indicating a multi-axle booster.  Did this thing have some kind of clutch to cut out beyond a certain speed?  Did it run at fixed cutoff or was there a Johnson bar for that thing?  In the rare case of a tender booster with siderods, if the booster cut out, didn't you still have those side rods going round and round at high rates for those small axles at road speeds? 

A booster sounds a whole lot like a steam traction motor -- what was to prevent one from designing a locomotive using booster engines to drive motored trucks and dispensing with the conventional steam locomotive drive?  With enough booster engines, couldn't steam match the pulling power of the 4-unit FT demonstrator. 

Or perhaps that is the direction steam would have gone if it had stuck around?  I kind of get the idea that the Franklin people or whoever made the booster wouldn't have minded if their gadget got adopted as the main form of propulsion.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?

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Posted by timz on Tuesday, August 5, 2008 9:24 PM
 Paul Milenkovic wrote:
I have seen the rare picture of siderods indicating a multi-axle booster.
On tender boosters, you mean? Side rods on the engine's trailing truck would indeed be rare. 
 Paul Milenkovic wrote:
Did this thing have some kind of clutch to cut out beyond a certain speed?
No clutch, but it was geared to the axle and disengaged at high speed.
 Paul Milenkovic wrote:
Did it run at fixed cutoff or was there a Johnson bar for that thing?
 Fixed, I'm pretty sure.
 Paul Milenkovic wrote:
In the rare case of a tender booster with siderods, if the booster cut out, didn't you still have those side rods going round and round at high rates for those small axles at road speeds?
Yes, but it's all rotating mass, so could be worse. But yeah, one suspects engines with tender boosters weren't usually expected to work up any speed.

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