Heavy trains at Cajon Pass

[truckman060473]

I've been looking at some Youtube clips of freight activity here and I really do find it staggering some of the lengths of un-banked trains climbing the 2.2/3% gradient. What sort of breaking strain do the couplings have? What about the physics of the first few wagons on a grade + curve where they will want to pull into a straight line, with only the wheel flange to fight against this massive force?

 

[eMeS]

You've raised many queries that I've wondered about over the years, ever since I visited Dallas and realised that their trains were different to ours! It does mean that every truck/wagon on the system (I assume?) has to be strong enough to withstand the maximum drawbar pull, and this must mean that a lot of weight is being transported around the US, and other large land masses, simply to haul these super long trains.

It's a very long way from fixed formation train-sets which whiz past my local station on the WCML!

 

[truckman060473]

There is a clip on youtube that is amazing too, featuring Tehachapi Loop. That clip gives an insight into just what these locomotives are capable of as you can almost see the entire train length due to the spiral. fascinating stuff.

 

[Pete2210]

Bear in mind that a lot of US freight trains have mid-train helpers and/or rear end helpers, these days a lot of roads are going in for DP, distributed power, where there is a unmanned diesel unit spliced into the train under radio control from the lead unit, this isn't completely new, UP and ATSF had SD40-2 units with radio control back in the 1980's, they were called SD40-2 Snoots on account of the longer short hood, but they were manned units.

Pete

 

[eMeS]

... featuring Tehachapi Loop....

Thanks for that, it's new to me - really fascinating stuff, and I wonder how long the wheels and track last.

 

[truckman060473]

Bear in mind that a lot of US freight trains have mid-train helpers and/or rear end helpers, these days a lot of roads are going in for DP, distributed power, where there is a unmanned diesel unit spliced into the train under radio control from the lead unit, this isn't completely new, UP and ATSF had SD40-2 units with radio control back in the 1980's, they were called SD40-2 Snoots on account of the longer short hood, but they were manned units.

Pete

The Tehachapi Loop clip featured at the top of the page on Youtube has no helper engines. Seven lead locomotives with 111 bogie hopper cars. When the locos appear in the foreground, just look at what is still in tow behind them on the awkward curves and the gradient. You'd think the wagons would all topple over inwards with the sheer weight behind them - I bet a model railway built on this would topple!!!

 

[Pete2210]

The Tehachapi Loop clip featured at the top of the page on Youtube has no helper engines. Seven lead locomotives with 111 bogie hopper cars. When the locos appear in the foreground, just look at what is still in tow behind them on the awkward curves and the gradient. You'd think the wagons would all topple over inwards with the sheer weight behind them - I bet a model railway built on this would topple!!!

They certainly did on my model of Tehachapi loop I built years ago. Over Tehachapi years ago the ATSF used to hang all their power on the front end and the SP used to have mid train and rear helpers, I haven't seen this Youtube clip so I don't know when it was filmed, but I think both BNSF and UP are using DP these days

Pete