Hydraulic Buffers

In message , Hunt James writes

Peco had one (SL-42) on their September 2003 price list, shown as a new item. I can't find a picture of it in their catalog.

Indeed they do a hydraulic buffer stop and it looks better than the hornby one. Lord and Butler have them in stock if anyone is interested.

Or real oil?

Yes, it comes as a small kit you assemble. Looks ok too, much more like te hydraulic buffers I have seen at terminus stations than the hornby version.

I know "hydro" means water, but isn't water incompressible? "Hydraulic" usually refers to oil.

(For a while in the 70s/80s the Toronto Transit Commission tried water- filled rubber bumpers on buses and trams; they were filled with a water- salt mixture, to avoid freezing, and had filler caps that popped open if they hit something. The problem was, they popped open rather too easily and covered the front of the vehicle with corrosive salt solution.)

I've seen water filled ones in action where the fluid is pushed out through a small hole

Main reason for using oil is that it hasn't evaporated and the system hasn't siezed up just when it's needed. Jolly glad oil wasn't compressible when I had to hit the brakes on the A7 this afternoon.

Ken

The British ones at at least one London station used water (possibly with anti-freeze), when a train hit them the jet described as dirty water shot up to the roof and upset some passengers.

Mike

Plain water does tend to freeze, evaporate and encourage corrosion.

Hydraulic brake fluid is one of many types of "oil" with additives - it's also good for removing tampo printed decals from diecast models.

Oil definitely has different "hydraulic" characteristics from water, and has the benefit of built-in lubrication!

I can imagine (in fact I remember), especially in steam days, the amount of dirt and soot that would accumulate on a terminal station roof.

Thanks for the info. on hydro. buffer stops, not quite the same as an artillery piece recoil system. When the buffers become compressed, and the water or oil has been expelled , I assume that they are returned to the ready position by pumping liquid back into their cylinders, or do they also have return springs? Regards, Bill.

It would be great if someone could confirm the design parameters for these buffers, i.e. what is it they were desgined to do?

As a nipper, I used to spend day after day at Waterloo waiting for a train to hit the buffers so I could see the jet of water. Of course, it never happened, but it was inconceivable to my frugal mind that the railways could invest in a piece of equipment that was never used. So I always thought that the very next train might be the one to miss its braking point!

Anyway, once I got a grip on reality, it was definitely my understanding that the buffers were rams that drove a plunger in a huge reservoir under the platform from which ordinary water would be expelled, and that they were not intended to deal with the odd tap from a slightly late application of the brakes, but rather were intended to protect the concourse passengers should the Atlantic Coast Express arrive with a dead or unconscious driver at the helm.

In other words, any actual use of the hydraulics would probably involve a public enquiry and the rebuilding of the buffers and platform, once the wreckage had been removed.

But, as I say, I'd love some expert illumination.

Cheers, Steve