Complete revelation.

[sjm]

I,m in Cornwall and with all the granite knocking earth rods in can prove difficult, to say the least.

Had a job recently that required new rods.
Managed 1 + 1/2 5/8ths rods in one location, using a sledgehammer, before the rod started to bend, and my arms started to hurt lol.

Installed a new rod in new location, 2 rods length across. This took about an hour to knock in. Still the resistance was 390 ohms, so I thought $%#t I'll have to knock down another one.


Having looked for advice on the internet, as I didn't fancy another couple of hours swinging a sledge, I returned to the job today with another rod and coupler. However I also had an SDS Max breaker and SDS Max arbour for TCT core drills (it just fits over the end of the rod) hired for about £35 quid.


40 mins later the 2nd rod was driven into the ground and the kit was all back in the van. WOW!!

I will need to rethread the top of the rod, because the arbour won,t fit over the coupler and driving stud and I'm going to have to drive a 3rd rod as the resistance is still above 200 ohms but I say again WOW! I certainly won't be going back to sledgehammers.

 

[tony mc]

I take it PME is out of the question !

 

[telectrix]

when you hit a tin lode with your rod, you'll get a good earth reading.

 

[sjm]

I take it PME is out of the question !

Yes Western Power now refuse to make new connections of PME to the overhead network. Also did a loop reading and got 0.61 ohms.

 

[sjm]

when you hit a tin lode with your rod, you'll get a good earth reading.

LOL! Very good

 

[Engineer54]

I,m in Cornwall and with all the granite knocking earth rods in can prove difficult, to say the least.

Had a job recently that required new rods.
Managed 1 + 1/2 5/8ths rods in one location, using a sledgehammer, before the rod started to bend, and my arms started to hurt lol.

Installed a new rod in new location, 2 rods length across. This took about an hour to knock in. Still the resistance was 390 ohms, so I thought $%#t I'll have to knock down another one.


Having looked for advice on the internet, as I didn't fancy another couple of hours swinging a sledge, I returned to the job today with another rod and coupler. However I also had an SDS Max breaker and SDS Max arbour for TCT core drills (it just fits over the end of the rod) hired for about £35 quid.


40 mins later the 2nd rod was driven into the ground and the kit was all back in the van. WOW!!

I will need to rethread the top of the rod, because the arbour won,t fit over the coupler and driving stud and I'm going to have to drive a 3rd rod as the resistance is still above 200 ohms but I say again WOW! I certainly won't be going back to sledgehammers.

That's basically standard practice, to use a good SDS hammer drill to do the rod driving for you. You can also hire special earth rod 40 to 50mm core drills, which would have been much better in your case. After doing your core drilling fill the cores with bentonite slurry and drop the rods in. ...I bet you would have got below 200 ohms using that method!!

 

[Rockingit]

Bentonite - isn't that what used to frighten Supergran?

 

[Knobhead]

Bentonite is weird stuff. Good for electrical conduction and yet a fantastic thermal insulator. It’s use in casting iron where it’s mixed with kerphalite fibres.

 

[sjm]

That's basically standard practice, to use a good SDS hammer drill to do the rod driving for you. You can also hire special earth rod 40 to 50mm core drills, which would have been much better in your case. After doing your core drilling fill the cores with bentonite slurry and drop the rods in. ...I bet you would have got below 200 ohms using that method!!

How many extensions to get 6 ft down. Not sure I'd like to risk a snagged core drill that deep, they're bad enough in the middle of a granite wall.

 

[Engineer54]

Use to come in One to Two metre sections, and can get them at 3 metre long too. On some projects they have gone down 60 or more feet!!! When drilling it's always better to hire the full drilling rig, it's so much easier then, than just using a hand held SDS type machine!!

Using a sledgehammer is the worst way of driving rods in the ground, the rods tend to spring around as the enter the ground, usually end up with a 40mm cone shaped entry hole...lol!!

 

[stuart569]

How come you have to rethread rod?We use a coupler and a decent bolt that does the trick.Never seen these purpose built rigs.Where would you get them?

 

[Engineer54]

The bigger and/or specialist hire companies, would be a good place to start looking.

 

[sjm]

How come you have to rethread rod?We use a coupler and a decent bolt that does the trick.

Because the arbour only fitted over the rod, without the coupler and driving stud, so it make a bit of a mess of the top of the rod and hence thread. I did hope that 2 x rods would do the trick though bearing in mind that there were already 1 + 1/2 rods in the other location.

 

[Geordie Spark]

How come you have to rethread rod?We use a coupler and a decent bolt that does the trick.Never seen these purpose built rigs.Where would you get them?

In the 1970's when diamond core drilling was a specialist thing I used to make them.

They had a hollow base with a rubber sealing strip around the underside edge & a column sticking up vertically from the top face of it. A saddle driven by a rack & pinion slid up & down the column and the drill motor was fitted to the saddle.

A vaccuum pump hose was attached to the hollow base & the vaccuum produced in the base was strong enough to stick the complete rig onto a wall & allow you to core a hole up to 12"" diameter through the wall.

There were additional safety devices (screwjacks, chains etc) that you were supposed to use just in case the vaccuum failed, but as the blokes using these things were paid by the hole, needless to say these were rarely used ........... :nono:

(ours were similar to this: http://www.redbanduk.co.uk/shop/ite...-drill-rig-c-w-110v-motor-and-107mm-wet-core/ )