Well SWMBO thinks I am an idiot but then she always have. ( with due justification ). Well I had to replace a fence post and lacked the energy to dig out the concrete. So I thought I would try capping ( I hope this is legal ). It has worked very well though the police may be knocking on the door soon and the cat has fled. Luckily the neighbours think I am an idiot so have taken little notice so far.

The post was in a hard to get place so capping was an ideal method.



I used water to soften the hard clay around the concrete.



My capping kit.

Slide hammer, poking rod and capping mat. The slide hammer is top weighted with lead for a better effect. Not shown ,of course, are the safety gear. Ear muffs, eye guard  and good gloves. What is essential is a blow tube to eradicate the dust as dust on the caps will mean the firer wont work.



Stainless steel rim firing rod.



Slide hammer with lead top weighted outer section.



Firing rod set in lead but would be better to have a welded in screw thread. Best to carry a spare firing rod on trips. Mine screws out of the lead insert.



That's it for now. I just have to look for the cat ---

Finished. A hard job made easy.

Thanks. That's a really useful guide - sorry about the moggie.

Round here, many of the houses are built on steeply sloping limestone. Some have undercrofts that are not full height across their width. We've been looking at one such house and only this morning I was pondering using caps to remove some of the rock to extend the full height section of the undercroft.

A couple of questions - is a licence needed to use these caps and what volume of rock can be reasonably be removed per cap?

I hardly think you need a licence as Hilti Caps can be bought on Ebay. However they are for use in Hilti nail firing guns though I cant see a problem. Actually the bang was not too loud and the cat was in the shed. I had never used them on concrete before but they worked well " double shotted ". Using them in caves on limestone is far more effective and much will depend on the inherent fractures and irregularities in the rock. Basically limestone shatters well but a fair bit of the target must be exposed. Although this post was tongue in cheek a bit it was also designed to help those using caps in a caving environment. Another safety feature would be to have a reinforced hole in the mat using two washers screwed together. If the slide fails to set off the caps you can hit the top hard with a hammer. Using just a rod is dangerous as it can fire out of the hole so hold the slide in place when firing.

Stepping up the issue you would need snappers or cord . The latter to be used only by somebody with a licence. Trouble is you would have less control over debris with both of those . We used a shaped charge this week fired by a licence holder in the cave. The target was too unstable to drill but things worked very well.

The Old Ruminator said:

Using them in caves on limestone is far more effective and much will depend on the inherent fractures and irregularities in the rock. Basically limestone shatters well but a fair bit of the target must be exposed.

Click to expand...

Capping is most effective when the shock wave can bounce of an air surface or fracture, so capping is a lot more effective on boulders than bedrock.

There is an article here on best capping practice.

grahams said:

Thanks. That's a really useful guide - sorry about the moggie.

Round here, many of the houses are built on steeply sloping limestone. Some have undercrofts that are not full height across their width. We've been looking at one such house and only this morning I was pondering using caps to remove some of the rock to extend the full height section of the undercroft.

A couple of questions - is a licence needed to use these caps and what volume of rock can be reasonably be removed per cap?

Click to expand...

I'd be a bit cautious about your foundations if I were you.