Advice please on core drilling a slab

[saveasteading]

I have hired a serious bit of kit, a Hilti D150 drill with stand, and a 110mm diamond core drill. One of those drills and a core a bit like that but longer ( and blue)

I'm looking for any experienced advice.

 

 

This is to take samples through the existing floor slab which is clearly very strong, and which the drawings from 40 years ago say to be 6" thick.

I simply want to confirm the thickness, and the quality by inspection, and will take a few cores.

 

They sold me some anchor sockets to drill into the slab to hold the stand in place. I wasn't expecting to have to do that,

Now I see that the 4 bolts that should screw down into the floor are jammed. Therefore I know that the previous hirer did not have to bolt it down.

Maybe they are really for horizontal drilling.

 

it also looks like a very precise bit of drilling for those 4 fixings.

 

Has anyone used one of these? Will it likely work without bolting down? especially if I take it very slowly and gently on the lowering handle.

 

I have a water connection for it.

But there is no instruction leaflet and I am  deemed to be an 'experienced operator' who did not need a demo.

 

All the signs are that it will indeed be  as designed, 6" thick on average with a single layer of mesh, probably stamped in after the pour.

ie a thorough design with rural construction processes. So it will need this heavy drill to get through it.

 

Has anyone used one? Any other suggestions or hints?

 

Just for fun, assuming this works, I am estimating an hour per hole, including moving it, if it doesn't need  bolting down.

 

 

[saveasteading]

I like that BH members say nothing if there is nothing to say.

 

I've had a day with the machine. 4 cores successfully removed and the quality and thickness is all good.

 

I didn't bolt it down, instead using 14.5 stone carefully placed on the stand and applying the lever pressure gently.

 

If I was 11 stone it wouldn't have worked.

 

I am now the BH expert on the reality....a hole should take 10 minutes but 4 holes took 5 hours, including umpteen hassles.

 

[Gus Potter]

Well done!

 

Who told you a proper core would take 10 min? This is a proper core sample not making a hole for a duct say where you can afford to be rough.

 

Coring a slab for techinical investigative info takes time. If you thrash into it you won't get a proper slab depth. Every 10mm matters when you are coring a slab for strength analysis / verification.

 

From memory the going rate is £100 - 150 a core on a 150mm anticipated slab depth with a recovered sample (in good shape) for the operative time. If you have managed 4 in a day then that is not bad. Each one needs to be logged, photgraphed etc and they need thinking time too!

 

 

[MikeSharp01]

6 hours ago, saveasteading said:

I like that BH members say nothing if there is nothing to say.

Yes, sadly, or perhaps not, none of the chaps who took part in the Hatton Garden job seem to be members.

Image from the FT.

[SteamyTea]

12 hours ago, saveasteading said:

I like that BH members say nothing if there is nothing to say.

I posted a response, asking you to video it.

Don't know what happened to it, seemed to have 'vanished'.

[markc]

I didn’t see the post until now, the 4 corner screws are for jacking the base to plumb and account for uneven surface. You generally use a single bolt in middle of the base plate (for horizontal or overhead drilling) or stand on it for slab work.

many bases have a rubber ‘skirt’ to seal using a vacuum pump but bolting or standing on it are the usual methods

Edited August 2 by markc

[Alan Ambrose]

>>> a serious bit of kit

 

That, pah, a kids thing - could probably hurt a soft human some though.

 

The Hatton Garden guys didn't seem to bolt theirs down and it was horizontal. I wonder how that worked - some kind of frame maybe? And that's, say, 400mm? No rebar at all?

[saveasteading]

5 hours ago, SteamyTea said:

I posted a response, asking you to video it.

I have one more to do so may ask for spousal assistance.

 

The whole kit wants to rotate counter to the drill, of course. Plus it lifts at the drill end in response to downward pressure on the rig handles.

3 hours ago, Alan Ambrose said:

didn't seem to bolt theirs down

this must have been serious kit, and serious expertise. I wonder if it had a bolt down through the drill, so it would come out with the core. Or Acrows across the room.

Anyway, the tech guy should be given a job in the army where he could do some good while being contained.

Where has the filth gone? No cooling water?

[saveasteading]

Just now, saveasteading said:

No cooling water?

On that. I had a pressurised water tank , but could have used a hose. I  thought this was for cooling, and it clearly does that as witness the very warm water coming out of the hole. But it seems to be crucial in turning the dust to slurry which probably lubricates the process, but certainly removes the muck. The finished hole is very clean.

Everything got hot. the transformer, some of the extension plugs, and the core and adjacent concrete of course.

2 of my extension plugs fused, with 10A fuses which I thought should be ample. Not that I have checked the sums.

 

re the power supply. It was 50m from the site supply to the furthest hole, so I used 240V leads p the the 110V transformer next to the work. For reasons someone else can explain, 110V runs out over long distances.

[SteamyTea]

7 minutes ago, saveasteading said:

For reasons someone else can explain, 110V runs out over long distances

[Onoff]

13 minutes ago, saveasteading said:

For reasons someone else can explain, 110V runs out over long distances.

 

It's why transmission lines run at up to 400kV.

[Adrian Walker]

2 hours ago, Onoff said:

 

It's why transmission lines run at up to 400kV.

I2R losses

[saveasteading]

4 hours ago, SteamyTea said:

 

1 hour ago, Adrian Walker said:

I2R losses

 

 explain implies a making plain or intelligible what is not immediately obvious

 

I  am none the wiser. Is there perhaps an analogy I might understand? 

Mr Watt, Sr Volta, Herr Ohm and M Ampere got into a fight......

Edited August 2 by saveasteading

[dpmiller]

for a given power consumption, lower voltages mean higher currents and so more voltage drop or "transmission losses" along the resistance of the wire.

[SteamyTea]

9 hours ago, saveasteading said:

explain implies a making plain or intelligible what is not immediately obvious

Shall use the old pipework analogy.

 

You have to get some water from one place to another, in a set time.

You can use a large diameter pipe with a slow flow, or a small diameter pipe with a high flow.

The diameter is analogous to the amps, the flow to the volts.

 

(the trouble with that example is that it does not take the resistance of the pipework into account, which is assumed to be laminar at all flow rates)

 

 

 

[Adrian Walker]

2 minutes ago, SteamyTea said:

Shall use the old pipework analogy.

 

You have to get some water from one place to another, in a set time.

You can use a large diameter pipe with a slow flow, or a small diameter pipe with a high flow.

The diameter is analogous to the amps, the flow to the volts.

 

(the trouble with that example is that it does not take the resistance of the pipework into account, which is assumed to be laminar at all flow rates)

 

 

 

Losses in a cable are the square of the current, so increase voltage to keep current low for same power. So 230V is better than 110V

[SteamyTea]

Just now, Adrian Walker said:

Losses in a cable are the square of the current, so increase voltage to keep current low for same power. So 230V is better than 110V

Yes, as that allows more electrons to 'flow' at the same speed.

 

Electrons, which have a mass, are the particles that do the work.  But we should really talk in coulombs (an amp per second).  There are 6.241509×10¹⁸ elementary charges in a coulomb.

[Onoff]

[saveasteading]

So....I am washing down a wall. A big pipe gets plenty of water there but it is slow moving.

A thinner hose ejects water at speed and displaces the muck.

They would fill a butt at much the same rate. Friction ignored for simplicity.

 

???? 

 

And the reason for 110V is safety. I break the cable / hose and the water soaks but doesn't pummel me ( electrons travel slowly through me to earth)

 

Would 55V be safer yet?

[Onoff]

4 minutes ago, saveasteading said:

So....I am washing down a wall. A big pipe gets plenty of water there but it is slow moving.

A thinner hose ejects water at speed and displaces the muck.

They would fill a butt at much the same rate. Friction ignored for simplicity.

 

???? 

 

And the reason for 110V is safety. I break the cable / hose and the water soaks but doesn't pummel me ( electrons travel slowly through me to earth)

 

Would 55V be safer yet?

 

Well 110V tools are 55V centre tapped to earth...

 

Isn't a case of if you get a belt you're only likely to take something like 25% of the "amps" you would with a 230V tool?

 

I've had a 110V belt in my sweaty armpit (shirt off, all Poldark etc). Leant over a machine where the case was live. That wasn't centre tapped to earth but a very ancient control voltage. Not funny. 

 

The clever people will know.

[SteamyTea]

14 minutes ago, saveasteading said:

And the reason for 110V is safety

Not really.

a 230V to 110V transformer electrically isolates from the neutral.  There are two separate windings.  If you ground either of the secondary (110V side) windings, the voltage drops to zero.  At zero voltage, no current can flow, so it is intrinsically safe.

 

 

The other reason is that in the past, it was cheaper to buy in 110V equipment from the USA and add an isolating transformer, than build 230V and 110V units at home.

 

14 minutes ago, saveasteading said:

I am washing down a wall. A big pipe gets plenty of water there but it is slow moving.

A thinner hose ejects water at speed and displaces the muck

You are talking two different things here.  One is getting the wall wet, the other is dislodging dirt.

Wetting is just mass transfer, the other is breaking a mechanical lock, which may require a minimum power or energy level.

Edited August 3 by SteamyTea

[Onoff]

18 minutes ago, SteamyTea said:

Wetting is just mass transfer

 

Was this a chat up line you used on the stem gerds at uni?

[SteamyTea]

6 minutes ago, Onoff said:

 

Was this a chat up line you used on the stem gerds at uni?

One I still use.

[Onoff]

1 hour ago, SteamyTea said:

One I still use.

 

It's up there with spherical chickens in a vacuum! 👊

[saveasteading]

On 03/08/2024 at 09:20, SteamyTea said:

zero voltage, no current can flow, so it is intrinsically safe.

If the machine is idle or disconnected, is the transformer still drawing current?