Interesting film clip

[dazbt]

www.britishpathe.com/record.php?id=68932

[John]

Concrete shields, I doubt they would have stood up to some of the conditions we worked under, but certainly better than wood pit props in most locations.

[dazbt]

Aug 18, 2010 15:12:19 GMT -5 John said:

Concrete shields, I doubt they would have stood up to some of the conditions we worked under, but certainly better than wood pit props in most locations.

Not sure about that ................ but perhaps even more important is the concept of roof support principles considering the date, it took the rest of the world a good few years to catch up with what is shown there .................. or did it? I might well be mistaken.

[John]

In what respects Daz, the date on the film is 1962, Dowty had been making the Roofmaster for around six years by then, Gullick the Seaman chock about four or five years, Dobson had established their Double Twos, plus a few other makes of chocks around at that time.

In the NCB's training booklet "Mechanisation At The Coalface" they list The Wild Desford Goal Post, never saw that one, but I do recall the German Westphalias.. Closest we had to a shield was the Gullicks.

It was shown the shield was cast concrete.

[dazbt]

I didn't miss the fact that it did clearly state that the 'props' were concrete, which does seem a bit far fetched and possibly inadequate at first thought, but at a time when 'adequate' quality and quanties of steel would have been difficult to come by in Hungary it was a reasonable innovative attempt, the arched linked canopy design would perhaps have better deflected direct vertical forces.
I am surprised that Dowty Roofmasters were being used in or around 1956 but that doesn't alter the fact that the first Roofmasters in use in collieries around here in 1962 (ish) were basically vertical hydraulic props set between a seperate top and base with no protection from flushing, the later addition of belting straps, chains and eventually steel plates didn't make them shields. The concrete 'props' shown in the film seem to me to be of a much different design, the angled ram to the rear articulated shield relating much more to the shield supports used today.
My point was that the supports shown on the film just seemed so much more akin to modern supports.

[John]

Ahhhh, now you're clearer Daz, the props looked like metal to me, but the canopy concrete with metal fixings set in the concrete.
I have to agree their design was years ahead of anything we had, I wonder if they pursued the design further??

Yes Roofmasters came on the scene around 1956, patent was for that year, first ones had air rams to push the face over and advance the chocks. There are a few photos of the original Mk1 design around on the internet. I'm sure I have one face photo taken at Gedling that was sent to me dating to the late 50's.

[dazbt]

Almost certainly the legs in that Hungarian chock were telescopic hydraulic rams, the hinged canopy assemblies were the concrete 'bits', the term 'concrete props' was a media expression no doubt losing something in translation ............ in much the same way as some of the modern day reporting, especially the media reports on Chinese coal incidents, some of the garbled translation attempts would be better left in undecipherable Mandarin.

[John]

I had a horrible thought when I read concrete props, crumbling under the load of weight coming on. ;D

[John]

In all seriousness, the concept is good, but can't see concrete standing up too well when the goaf tends to hold up for yards on end, then comes crashing down. My guess would be the concrete shield would break up.

[dazbt]

Aug 19, 2010 15:38:50 GMT -5 John said:

In all seriousness, the concept is good, but can't see concrete standing up too well when the goaf tends to hold up for yards on end, then comes crashing down. My guess would be the concrete shield would break up.

Well, I not an expert in anything and I would certainly not pretend to know anything technical about Longwall Roof Support, but, my guess would be that a chock shield canopy made of reinforced pre-stressed concrete would stand up 'fairly well' to the forces of a long standing gob break which possibly would put an angular forward force onto the chock rather than a sudden vertical downward weighting. I can, in technical ignorance, also imagine that a sustained, steady and equal loading acting vertically upon a concrete canopy wouldn't cause a catastrophic failure either, obviously within design limitation, what I can visualise is that over time with frequent variable loading, release and repetive impact load that concrete would suffer incremental stress/fatigue fracturing to a greater extent than a comparative steel construction. It seems that there are plenty of modern day arguments ongoing as to the stress and impact loading quality comparison of steel and concrete structures in the building construction world, particularly in regions that are likely to suffer catastophic earthquake damage.
Having said all that, I'm fairly sure that if I had found myself crawling through faces supported by concrete chock canopies a great deal of my time might well have been spent looking closely for signs of concrete dust and cracks.