|
|
Post by coalfire on Jul 30, 2008 21:18:46 GMT -5
I was talking with an old Miner the other day who worked the face at Eastern Associate Affinity mine in the 80's and he was talking about using dowty longwall shields. Anyone know anything about these?
|
|
|
|
Post by dazbt on Jul 31, 2008 2:44:37 GMT -5
I was talking with an old Miner the other day who worked the face at Eastern Associate Affinity mine in the 80's and he was talking about using dowty longwall shields. Anyone know anything about these? Hydraulic cantilever coalface roof supports, Dowty being the manufacturer. clear pic on here; www.epm.com/shieldsupports.html |
|
|
|
Post by John on Jul 31, 2008 7:53:38 GMT -5
|
|
|
|
Post by dazbt on Aug 2, 2008 17:07:32 GMT -5
I was talking with an old Miner the other day who worked the face at Eastern Associate Affinity mine in the 80's and he was talking about using dowty longwall shields. Anyone know anything about these? In fairness to this 'question', it could just require a bit more than a simple answer that shields are a type of Longwall roof support. I would never even attempt to say that I know all the technical differences, but as far as I can recall Shields were the very latest innovation in such roof support units, a development from the original simple relatively unstable four legged hydraulic chock through the Chock Shield which incorporated direct canopy to base linkage based on a cantilevered arrangement, that in turn created a much more robust and stable support which provided an integral flushing shield protection (deflection of goaf breakage) and eventually resulting in a pure Shield, in my words (probably to be destroyed by a roof support expert), which is designed to provide adequate direct forward support whilst ensuring reactive and controlled breakage of goaf. |
|
|
|
Post by John on Aug 2, 2008 17:19:32 GMT -5
I concur. Haven't a clue what Daz was on about, but have to agree. ;D ;D ;D
No, in all fairness, Daz is right, they provide protection from goaf flushings.
All the last ones I worked under had side flaps that had a hydraulic ram to push the flap to the adjacent chock when pressurised to the roof, preventing any roof "dribbles"
As Daz and myself and many of the older members of this site recall, the older chocks were open to the goaf, and when the goaf collapsed, it was common for it to flush into the crawling track.
|
|
|
|
Post by Wheldale on Feb 20, 2010 6:46:15 GMT -5
A undermanager at Wistow once explained that with chocks the legs were at 90 degrees to the base were as shields the legs are at a angle. This is the simplest explanation between the two types of supports I have heard.
|
|
|
|
Post by John on Feb 20, 2010 6:54:40 GMT -5
Shields give full coverage to prevent the goaf "flushing" into the walkway. Dowty shields and Gullick shields all had legs that were vertical as did their chocks.
|
|
|
|
Post by John on Feb 20, 2010 6:57:17 GMT -5
|
|
|
|
Post by dazbt on Feb 20, 2010 8:32:10 GMT -5
Again, I'm no expert but I reckon the supports in your pic. John are 'Chock Shields' i.e four legged chocks incorporating a linked shield. I thought that 'Shields' were two legged and 'Chocks' were multilegged supports that didn't have shields connected by ....... (what I think is called?) Lemniscate linkage.
Send for the Dowty rep .................
|
|
|
|
Post by John on Feb 20, 2010 8:54:28 GMT -5
Again, I'm no expert but I reckon the supports in your pic. John are 'Chock Shields' i.e four legged chocks incorporating a linked shield. I thought that 'Shields' were two legged and 'Chocks' were multilegged supports that didn't have shields connected by ....... (what I think is called?) Lemniscate linkage. Send for the Dowty rep ................. You could be right Daz, just going by American sites, they never use the term "chocks" at all just shields. Chocks to us were the "Gullick Seaman", "Dowty Roofmaster", "Dobson Double2's" etc. Then along comes "shields" whuch total protection, ie no open gaps between supports, backs enclosed to prevent the goaf from "flushing in" etc. My guess with the likes of Joy and Continental style (European) shields with the sloping legs, is it's done to create a beam support at a slight angle to encourage a "break" in the roof for hard sandstone roofs. As an example, bot the types I worked under, Gullick and Dowty, caused the roof to "hang up" sometimes for many yards in the goaf. One of the reasons longwalls took a long time to get established in Australia. The first was a disaster, I think it was at Bellambi Colliery in the late 1960's early 70's. Comprised an AB16 shearer, worked alright so was told, but chocks were Gullick Seaman 5 legs modified for the thick seam. Nowhere large enough to work under heavy sandstone roofs as found down under. When the roof eventually "caved in" after one of these "hangups" it wiped all the chocks out. They lost all the equipment. It was several years before anyone was willing to give longwalling a try again. Angus Place was the next try under Gullick/Fox chock shields, which were a success. Would be handy having a Dowty expert though to clarify things. |
|
|
|
Post by John on Feb 20, 2010 12:39:29 GMT -5
|
|
|
|
Post by dazbt on Feb 21, 2010 3:03:23 GMT -5
I'm glad that I was never a 'Chock Doctor' cos. I would never have known the difference between a chock shield and a shield, in fact I still don't  ......... but I do remember the 'crocodile props' and how soddin heavy the link bars were. |
|
......... but I do remember the 'crocodile props' and how soddin heavy the link bars were.