mixing dynamic/non-dynamic brake equipped locos

[pedro]

This is starting to become a great lesson on train braking -- thanks to all the pro's for chiming in .. would you please explain "stretch braking" for this foamer?

I can’t imagine coming into restricted speed without hot brake shoes when it’s below zero, the rules change a bit as temps fall. Conditioning the brake shoes needs to be a priority when it’s cold and snowing . I use any opportunity to use the automatic to that end . Although I prefer dynamics I also want the comfort of having warm shoes on the train. I have no issue dragging a 10 lb set downhill in restricted speed.

For sure, agree fully. Conditioning the brakes in cold/snow is also still a thing for us as well. The company just emphasizes use of dynamics over the air in below zero conditions because of the possibility of having air problems at extreme low temps. Stuck triple valves, leaking gaskets, sticking brakes etc. A lot of this is much less of a problem with the increased use of distributed power nowadays anyway.

[nkalanaga]

Stretch braking used to be common with passenger trains, especially with steam engines, to avoid slack action when stopping and starting. 

Steam-powered freight trains usually stopped with the slack bunched, to make it easier to get started.

In most cases, neither is a big issue today.  Diesels can start anything they can pull, even with slack stretched.  And diesels (or electrics) can start a passenger train smoother than most steam.

[Hawghead]

Stretch braking is essentially pulling the train with the brakes set with the slack stretched. it's a good way to have good control over train speed as all you need to do to stop is shut off the power with train stretched. Bunched is the other slack condition bunched is when braking force is applied to the head end of the train causing the trains slack to bunch to the head end.

It's also the best way to control slack in the train.  Trains break in-to when there is bunched slack in the train and either terrain or train handling causes it to stretch out to quickly.  Stretch braking prevents this because all the slack has been stretched out.  I was always taught that it's almost impossible to hurt a train that's stretched.

Scott

[nkalanaga]

Especially on "flatland" railroads that go up and down little hills, sometimes two or three hills in one train length!

[John]

So the Micro Trains slinky effect is proto afterall

[davefoxx]

So the Micro Trains slinky effect is proto afterall

Ed's Law strikes again.

[peteski]

So the Micro Trains slinky effect is proto afterall

By the same token, instead of stretch-braking, why don't they just install those little MTL friction springs in journals of few cars in the train?

[sd45elect2000]

By the same token, instead of stretch-braking, why don't they just install those little MTL friction springs in journals of few cars in the train?

in the real world we call those plain bearings. getting them moving was not so easy.

[Maletrain]

Thank God the prototype couplers do not have the kind of springy oscillations that the MTL couplers have in N scale trains!  I have never seen a real train act like a slinky as it went by me.

[peteski]

in the real world we call those plain bearings. getting them moving was not so easy.

I was just joking, but now that you mentioned it, that makes sense.

[nkalanaga]

Especially in cold weather, the plain (solid, friction, etc) bearings were much harder to get rolling than modern roller bearings.

[Hawghead]

Thank God the prototype couplers do not have the kind of springy oscillations that the MTL couplers have in N scale trains!  I have never seen a real train act like a slinky as it went by me.

You'd see it better if you were close to the train and the train was at slow speed.  Cushioned draw bars are the culprit.  A cushioned draw bar has about 18" of movement, that 3' on each cushioned draw bar car, now figure if there are 75-80 cushioned draw bar cars in a train that's about 200' of movement, then factor in that some will be loads and other empties and you end up with a formula for a lot of broken knuckles and draw bars.  I've been railroading for 18 years and never "got a knuckle" until they started running these super long trains and I got two in the last two years.

Scott

[sd45elect2000]

You'd see it better if you were close to the train and the train was at slow speed.  Cushioned draw bars are the culprit.  A cushioned draw bar has about 18" of movement, that 3' on each cushioned draw bar car, now figure if there are 75-80 cushioned draw bar cars in a train that's about 200' of movement, then factor in that some will be loads and other empties and you end up with a formula for a lot of broken knuckles and draw bars.  I've been railroading for 18 years and never "got a knuckle" until they started running these super long trains and I got two in the last two years.

Scott

I haven't got a knuckle in years. last time was an ore train, 13500 tons- 4000 feet- AB brakes- steel shoes

[Maletrain]

Are you saying that the prototype car on the end of a train will oscillate back and forth as it runs on straight level track, just like an MTL car in N scale?

[Missaberoad]

I haven't got a knuckle in years. last time was an ore train, 13500 tons- 4000 feet- AB brakes- steel shoes

I imagine all those tiny cars are a nightmare for slack action and run ins...

Knock on wood I've never had to change a knuckle. We had an engineer who got 3 in the same incident including one between engines on the lead consist... He still hasn't  lived that one down...