This is the first thing ive found using my new snazzy GPS. The tomb is situated in the middle of a number of fields and ive tried to find it before unsuccessfully. There is an esker ridge to the north of this site. The biggest stone is pretty impressive and the boundaries to the field that it is in have a number of huge stones of similar size so this is probably what happened to the rest of the tomb. It was a bit misty so I couldn't see its relationship to any hills in the area especially the Devils Bit but the 'front' of it is east-facing so it may be aligned to general sunrise.
North Tipp Archaeological Inventory
Situated on a gently sloping ridge in rolling farmland. The northern side of the E-facing chamber and its displaced roofstone survive. To the E there is a portal-stone. 2.25m high. To the W and leaning against the last there is a side-stone, 1.7m high, the roofstone 2.2m x 1.8m and 0.45 thick leans against the western end of the sidestone. A displaced slab, 1.9m in maximum dimension, rests against the outer faces of the orthosats (Manning, 1983-4, 44-5)"
Very rough directions
Its just over a 1km from the main road (Nenagh-Borrisokane) and isnt far from the bye-road that leads from Ardroney village roughly north-east-ish. However there are a lot of new houses built on the bye road so the easiest place to access without going through someones garden and getting some strange looks is from the main road. The fields are pretty ok just loads of electric fences to duck and dive over.
About a mile to the east of Ardcroney in a district called Lough Fada (Loch Fada), which according to tradition, was visited by St. Patrick. The place was, as the name indicates, at one time covered with water, but it is now quite dry. The bed of the river, which drained the lake into the Shannon, can still be traced. Faint with hunger, the saint was one day, according to legend, passing the lake in which three men were engaged fishing. Though hard at work for hours they had caught no fish till a few minutes before St. Patrick's arrival. Explaining his plight to the fishermen, he asked them for some fish to relieve his hunger but they refused. He thereupon changed them into stones. Three large pillars of stone, each about six feet high and four feet wide, are still pointed out as confirming the truth of the legend.
As is the case in most legends, there is probably a stratum of truth in the story. According to Dr. Healy, the saint visited Rathurles, about three miles distant, on his journey northward from Cashel. From Rathurles he proceeded to Terryglass, and Ardcroney would be in a direct line between these two places; near Loch Fada are the remains of a large fort which is still called "The Doon" (An Dun), where a king or chieftain resided in olden times. It was St. Patrick's policy to convert the ruler of the district first, and having done so in Ardcroney, he would probably proceeded to Loch Fada to view the Druid's altar - for such undoubtedly were the three large stones. According to tradition, a number of smaller pillar stones formed a circular enclosure round the altar but these were removed by the planters for building purposes. It is also stated that the smaller stones were covered with rude inscriptions on the edges. These were probably the Ogham characters as used by the Irish till St. Patrick's time."