Setting coupling slack?

[truckman060473]

Ok I was wondering about the common sight in days gone by where a shunter would attach a loco to the coaches after running round etc. Today at my local preserved line (Gwili Railway) the 03 or 04 shunting locomotive was in use with a pair of coaches. The loco approached the coaches until it gently struck the buffers of the coaches and stopped. The loco then revved up and pushed into the coaches until the buffers compressed. The man then went under to couple up. The pipes were attached and the coupling assembly was slung over the hook. Then the handle was spun round and the opposing thread studding drew together taking up the slack. My question is, how do they know how far to turn the handle? I was thinking that if it was made too short then on a sharp curve it could force the buffers in past their "end stops" and possibly cause a derailment and or snap the coupling?

 

[E&W Lucas]

The coupling is designed to be would up. It is normal just to leave a couple of threads of slack, just to stop the thing jamming. The reason for easing the coupling us so that you can get it over the drawhook without unwinding it.

From what you have described, they were making a horlicks of the whole process. The last thing you do is couple the brake pipes, for obvious safety reasons!

 

[ralphchadkirk]

I wouldn't usually comment in such a way, but knowing the Gwili's history I would have thought they tried to get such things perfect now, and attaching the pipes before doing the coupling is not only an inconvenience, but means the driver can now move off with the shunter underneath. Leaving the brake pipes off is the shunter's protection.

 

[33056]

From what you have described, they were making a horlicks of the whole process. The last thing you do is couple the brake pipes, for obvious safety reasons!

Correct, last things to couple together and first bits to split when detaching, though I have been told that the easiest way to couple first generation DMUs is to work methodically from one side to other to make sure you don't forget anything! (never had to deal with those personally)

 

[truckman060473]

Sorry I'd just like to point out I only gave a general description of the coupling process. That said, It is possible he did it the correct way round.

 

[66526]

Whenever I am coupling/uncoupling I would never pipe up before hooking up. It is one of the basic things we are taught when training. As for a screwlink coupling we get taught to have 3 threads on all sections (all the same length). This is the Underground though so could be different to mainline. 'Going inbetween' is definately the part of my job where I feel the most vulnerable!

 

[Grantham]

Sorry I'd just like to point out I only gave a general description of the coupling process. That said, It is possible he did it the correct way round.

He probably did it the correct way around, otherwise it would be tricky to spin the screw weight around, not only because the hose was in the way, but the brakes on the carriages would release and the compressed buffers would make the cars push off!

The screw is wound up as far as it will go, it won't break unless it is overloaded. I have seen photos of trains in Germany of 4,000 ton mineral trains (hauled by two 2-10-0 s, presumably on reasonably moderate gradients) with screw couplings. Here in NSW, Australia, the limit for screw couplings was 900 tons on 1/40 gradients, although in older rollingstock there might be a lower weight limit. Almost all couplings here are now automatic knuckle couplings with a 1/40 limit of many thousands of tons.

If the couplings are left slack, there will be more dynamic forces between items of rollingstock than is desirable without careful driving. Knuckle couplings without buffers or sprung gangways have a great deal of slack and great care has to be taken with driving technique to avoid adverse slack action.

Mick

 

[33056]

............As for a screwlink coupling we get taught to have 3 threads on all sections (all the same length). This is the Underground though so could be different to mainline.

Though I don't remember it being a specific instruction, "three threads" was the usual rule of thumb in the "mainline" as well (at least round here)

One dodge when uncoupling if you are a little on the large side (or just plain awkward like me ) is to go in, split the pipes and destroy the brake; get back out then ask the driver to "ease up" to slacken the coupling which makes it easier to undo - works well on coaching stock or anything with a push-bar due to limited space.

One last thing - always make sure that the driver knows where you are and what you are doing at all times; I used to hate dealing with class 90s as there is no side window for the driver to lean out of which restricts their view. Shunting is a dangerous activity and I have known several people who have lost their lives or limbs through a moments inattention :cry:

 

[Hydro]

'Going inbetween' is definately the part of my job where I feel the most vulnerable!

I have to "go underneath"! Checking, cleaning and repairing the bogie mounted equipment prior to the shift. Even with full protection in place, wheel scotches, destroyed brake pipe held open to atmosphere, not to be moved boards plastered here there and everywhere, constant radio contact with the shunter/driver I'm still thinking "My groin is level with the wheels. My head is wedged under the bogie frame. Let's work quicker."

 

[Cherry_Picker]

It's times like this where I am glad I just have to sit in the drivers chair waiting for a voice on the radio telling me I can release the brakes and move.

 

[spurs4life]

The one part that always concerns me is coupling on a Preserved line and working with steam heat and trying not to get your hand burt off especially when your fireman does not turn it off at the vale in the cab to find it still gushing out. (happy days lol)

 

[E&W Lucas]

The one part that always concerns me is coupling on a Preserved line and working with steam heat and trying not to get your hand burt off especially when your fireman does not turn it off at the vale in the cab to find it still gushing out. (happy days lol)

More to the point, why hasn't your driver ensured that the fireman has turned the heating off 15 - 20 mins prior to reaching your terminus?

It's basic knowledge, and if they don't possess it, then they shouldn't be doing the job.