Down under steam railroading

[richg]

Beyer Garratt 6029 trial

http://www.youtube.com/watch?v=-wNI2XHHudQ

Waiting to see the Big Boy doing this.
Took my girlfriend back in June to Steamtown. She was impressed by the size of the loco.

Rich

[Hamish K]

I saw 6209 about  10 days ago. I live in Canberra, Australia and was walking to the Fyshwick markets when I heard a steam engine whistle. There running on a track visible from the road was 6029, obviously undergoing a further trial. (The Canberra station and railway museum are just across from the markets.) She's a wonderful locomotive. It's always great to see a loco come back to life. Looking forward to riding behind her when she goes into excursion service.

Hamish

[Desertdweller]

I wish these things had caught on in the US.

Can you imagine a UP or N&W version?

Les

[ebtnut]

IIRC, the D&RGW apparently explored a narrow gauge Garrett but decided against for some reason. 

[rogertra]

IIRC, the D&RGW apparently explored a narrow gauge Garrett but decided against for some reason. 

Probably the common, "We didn't design it over here, so we won't use it."

Applies to both sides of the Pond but particularly this side.

Cheers

Roger T.

[ebtnut]

The knock I've heard on Garretts is that they lose some tractive effort as the coal and water are depleted, since that weight is part of the overall loco weight. 

[Hamish K]

I've always understood that it was horses for courses. The Garratt;s advantages are the ability to go round tight curves (tighter than a Mallet)  and the ability to have a larger diameter boiler for a given loading gauge as well as having a light axle load for its power. Its disadvantages were length (too long for many turntables, many NSWGR 60 class locos,including 6029 were converted to dual control so they didn't have to be turned), and that the coal and water are over the drivers thus lessening the tractive ability as these are consumed.  In places with light trackwork, tight curves and small loading gauges they are unequalled. However if loading gauges are generous and curves not so tight other  designs, such as Mallets, will be preferable. Few places in the USA would have justified Garratts. Perhaps some narrow gauge lines, but probably few of these needed the power that Garratts would have provided.

Hamish





Hamish

[Skarloey Railway]

I'm not entirely clear why the loss of tractive effort as coal and water are consumed should be such a drawback in the garratt design when in tender engines coal and water are never over the driving wheels. Seems like garratts are being criticised for not always having something that other designs never have.

I suspect the main reason garratts never happened in the US was the technology to produce flexible high pressure steam pipes was slow to develop; thus, by the time garratts really proved themselves the mallet was very well established in the US and any subsequent improvement in locomotive design came through early dieselisation.

[Doneldon]

Skarloey-

I think you likely have a point that one of the reasons that Garretts weren't used in the US is that the Mallet, and even simple compound engines were well understood and familiar here so there wasn't much need for Garretts. However, I also think you missed the point of the decreasing tractive effort in Garretts as they consumed their water and fuel.

The problem wasn't that Garretts lost tractive effort per se, but the fact that their tractive effort changed as consumables were used up. Thus, a loco could start out with plenty of power to pull its train but later in the day be unable to do so. This would make it very difficult to assign engines to a trick and it would also lead to a lot of waste. Locos would have to be assigned to a trip based on their "light" tractive effort. They would thus be very large, expensive machines for the job they were doing and they would be comparatively inefficient for most of a given work cycle because they would be hauling their own great weight around all of the time including much of the time when a much smaller locomotive could have done the job.
                                                                                                                                    -- D

[jward]

regarding the narrow guage garrett.....

the Uintah railway used tank mallets around 66 degree curves. curves that sharp are normally only found in streetcar trackage in cities, but they hauled freight around those curves.



if a mallet could do this why would we need a garrett?

https://www.youtube.com/watch?v=x7IkujWEpm8

[aspoz]

For the AD 60s the tractive effort was 63490 in the final form.  This compares with the D57 class 4-8-2 (the otherwise most capable on the NSW system) of 64000 lbf.  But, and this is a big but, the relative axle loads were 16 1/2 tons for the Garratt vs 24 tons for the 4-8-2; and that was of enormous imporatance on the NSWGR.  The alteration in the tractive effort as water and coal was consumed was neglible; the majority of the weight on the wheels came from the boiler assembly etc.