Two Rod and Valve Gear Questions

[NW Mailing List]

Good morning,

 

Absolutely right  re the adhesion issue. The long steam passages could of course be insulated to prevent heat loss. I think one large Garrett was built for use in Russia as a one off. I have no idea as to what became of it or how successful or otherwise it was. There was also a gigantic 4-14-4 which must have put pressure on track curves. 

 

UK applications were limited to some rather indifferent 2-6-0+0-6-2 types and a one off that was used to push loaded coal trains (unbraked two axle wagons!!) up a steep gradient. I t was converted to oil firing and used as a pusher on the Lickey Incline for a short period before being withdrawn from service. The recent small invasion of ex SA narrow gauge locos has raised a lot of interest

 

The notion of going for some enormous Triples concept was probably pushing the boundaries of technical feasibility. The implied maintenance costs must have been horrific.

 

Regards

 

Phil Mortimer 

 

From: NW-Mailing-List [mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of NW Mailing List
Sent: Wednesday, August 8, 2018 3:54 PM
To: NW Mailing List
Subject: Re: Two Rod and Valve Gear Questions

 

The great advantage of the Garratt was that it spread its weight over a longer distance than was possible with a Mallet.  Surely this advantage made it popular in some areas.  

 

It’s main disadvantage was that as fuel and water were consumed, weight for adhesion also diminished; this would have been compensated for somewhat by adjusting the designed cutoff of both engines.  Also, the long steam passages necessary to get steam from the throttle to the cylinders might have been a problem.  It is noted that Garratts were not used in areas where cold temperatures prevailed; condensation could be a problem.

 

Because the Mallet pulled a tender for fuel and water, its adhesion was not affected by consumption.  I believe the Triplexes (Triplexii?) had the cutoff of the tender engine adjusted to compensate for this.  

 

Could a Triplex have worked with a more potent boiler?  Possibly; the two designs that were actually built had boilers less potent than the USRA 2-8-8-2.  Interestingly, a Baldwin designer sketched Quadruplex (2-8-8-8-8-2) and Quintuplex (2-8-8-8-8-8-2) concepts, both with articulated tenders, and both with Triplex-sized boilers.  How he expected the engines to perform with those boilers is a mystery.  

 

The Virginian never bought its 2-8-8-8-4.  After its monumental failure it was sent back to Baldwin and came back to the VGN as a 2-8-8-0 and a 2-8-2, both of which were satisfactory.  Its 2-10-10-2 was successful and remains the steam locomotive that could actually produce the highest starting tractive effort ever.  The Triplexes were rated for higher drawbar pull, but couldn’t sustain it for more than a couple of carlengths.  The 2-10-10-2 could.  

 

EdKing

 

From: NW Mailing List 

Sent: Wednesday, August 08, 2018 9:07 AM

To: NW Mailing List 

Subject: Re: Two Rod and Valve Gear Questions

 

On 8/7/2018 5:13 PM, NW Mailing List via NW-Mailing-List wrote:



They were certainly interesting to watch running. So odd seeing ll that firebox just hanging out in the breeze. Not being an expert in anything I would say the engine with thee water bunker would have to lose a lot of traction as the tank was emptied. The tender with the fuel bunker would suffer the same fate. Those could be  rather bad features. Conventional articulateds wouldn't summer that problem except the Triplex and VGN engine which were not very efficient for other reasons.

 

 

(snip)

Since the boiler weight is suspended between the two engines, would it not still have just about as much traction as a standard articulated?   Also the tender shell weight is also still on the engines rather than being drug behind. Granted full tanks and bunkers would give the best results and, since they are usually full when starting a train, I can see where that would be an advantage.    

Wonder if any American loco builders or individual roads did any research or comparisons between Garretts and our standard articulated locos ??

While not exactly pure N&W stuff, it is an interesting discussion. 

Take care
Bill 




-- 
==  Scale Model Railroad Products  == 
== Manufacturer - Retailer - Importer ==
  
Bill & Diane Wade       
  
B.T.S.                    
1782 Trinity Rd
Belington, WV  26250-7621    
  
Phone: 304-823-3729
FAX: 304-823-2901   
http://www.btsrr.com
  
We wish you Fair Winds and Following Seas.
  _____  


________________________________________
NW-Mailing-List at nwhs.org
To change your subscription go to
http://list.nwhs.org/mailman/options/nw-mailing-list
Browse the NW-Mailing-List archives at
http://list.nwhs.org/pipermail/nw-mailing-list/

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://pairlist6.pair.net/pipermail/nw-mailing-list/attachments/20180809/fd35336d/attachment-0001.html>