1620 VS 1720

Byjingodingo · Posted: Sun Nov 16, 2008 10:09 am

I had a good look at the recently refurbished 1620 while it was in Toowoomba. QR did a very nice job, right down to the vintage colour blue & white.

What I'd like to know is how these locos stacked up against the 1720. I think the 1620 looks a bit bigger, but I guess they're about the same in size, weight etc. Does anyone know how popular the were with crew compared with the Clyde version 60tonners? The 1720s have outlasted the 1620s by a long shot and seem destined to be with us a while yet. How come they survived and the 1620s didn't? How do they compare in performance?

Finally, I grew up near the Kingaroy and Monto branches and used to watch the locos there. I don't recall seeing any 1620s on those lines. Does anyone know if they ever made it up to Kingaroy or Gayndah / Monto? Were they too heavy?

LOOK OUT FOR TRAIN

Expedition Pass · Posted: Sun Nov 16, 2008 10:48 am

Until the mid-1980s there was no real basis for comparison between the two classes because the 1720s were confined to the Brisbane suburban area, the Southern and Southern & Western Divisions, while the 1620s were generally found only in the Central and Northern Divisions, so until then there weren't many drivers that had worked any serious length of time in both classes (although there obviously would have been some).

In the very broadest sense the 1720s were admired for their reliability, acceleration and vision when operating cab leading. Conversely, the 1620s were not quite as reliable, suffered the engine leaks that were common to all of QR's English Electrics, were reasonably slow off the mark (and slightly lower-powered than the 1720s) and with that high short hood didn't offer the same forward vision as their Clyde counterparts. One facet in which the 1620s did excel was their ride quality, thanks to the design of their bogies.

The 1620s were the last English Electric class operated by QR, and their elimination from the fleet, at a time when many branch lines were being upgraded to take 90 tonne locos or closed altogether, allowed a reduction in the spare parts inventory and the training workload for operational, mechanical and electrical staff. Consider that while the 1720 and the 2170 are very different designs the engines inside them are both Electro-Motive 645s (V-8 cf. V-16).

1620s did indeed operate on the Kingaroy and Gayndah-Monto branches at various times right up to the 1990s, although they were never very common. During the 1990s I can recall following a Kingaroy-Gympie goods with a 1620 and a 1720 first vehicle from Kingaroy to Murgon, and a 1620 run single unit from Biggenden to Marybrough on a magnetite special.

Big J · Posted: Sun Nov 16, 2008 2:04 pm

One reason that the 1720s were favoured over 1620s on the surburban network was that the 1720's were designed with "Quick Start" switch that modified excitation rates to the generator and gave faster acceleration. So this was useful with suburban runs.

Also I read that they had their traction motors hung differently to the 1700 and 1620 classes that also assisted in the acceleration of the locomotive. Unfortunately my memory can't recall if it is off the bogie or axle. Someone with more knowledge should be able to answer that description as I can't find that in my references must be in an article on the locos in Rail digest etc.

Cheers
Jas

Cheers,
Jas

qredge · Posted: Sun Nov 16, 2008 4:17 pm

Drivers that I met that had operated both seemed to prefer the one that they first drove-When 1720s came to Central and Northern Qld the drivers reckon they were rough to ride but when the 1620s came to the south the drivers said they were gutless wonders

The difference in power was about 100hp which is 10% so they would notice the difference especially if hauling a passenger like the Grandchester pass-they were slow off the mark as well as not having the quick acceleration feature

I liked the sound of the 1620- the bubbly sound compared to the roar of a 1720 accelerating a suburban

As was said when the branch lines were closed or upgraded the need for 60tonners diminished and it made sense to keep to clydes for parts etc thus the die was cast to get rid of them

Naz · Posted: Mon Nov 17, 2008 8:36 am

The 1620's were used on the Gladstone Monto line occassionally. The last one used i think was around the early 90's. I always prefered the 1620's compared to the 1720's.

Expedition Pass · Posted: Mon Nov 17, 2008 9:58 am

doug75 · Posted: Mon Nov 17, 2008 6:28 pm

''My father reports his own experiences with these locos.

He agrees with all that was said about the 1720's and would like to add another problem with the 1620's on suburban passenger work. The 1620's had the standard 3 electrical transitions - straight parallel,series/parallel, straight series. However, often when making the final change up to straight series on a hill climb, the system could not handle the load and automatically flicked back to series/parallel with consequent loss of speed. Then as speed increased again it would change up, then maybe back down again depending on the loading and length of the climb.

The analogy here is an automatic motor car climbing a range which can " hunt" between gears. And of course this caused time losses and lateness on suburban work.

So after a short period the 1720's were favoured on the heavier suburban loads ( 8 Evans or 7 SX's ) on the Northside, whereas the 1620's were mostly banished to the bush with a couple left working the lighter Southside loads ( 4 or 5 Evans, with one six pack [ the famous Set C, ex northside set 33 ]). Eventually the Southside too became exclusive 1720 territory, plus a few 90 tonners, and as electrification proceeded on the Northside, a few SX's drifted to the Southside as well - what luxury.....

See my FotoPic photos here - Updated 12/05/08

elsoxo · Posted: Sat Nov 22, 2008 11:45 pm

To describe the comparison very simply:

1620's were easier on the ears and had a better ride.

1720's could maintain the schedule with 8 car suburban loads but 6 cars was a practical limit for 1620's.

Rail enthusiast since 1957.

Controller · Posted: Sun Nov 23, 2008 9:10 pm

The thing 1620's were good for in the Brisbane Suburban area were on the suburban shunt trains.

I only had to use a 1620 class (1645) on a suburban passenger and that was due to a loco failure and 1645 was the only loco anywhere in the vicinity and it just slaughtered the other trains with it's poor power effort

All gave some, Some gave all