Capping

[sambo]

Hi all

I am in the very early stages of attempting to design an electrical firing pin which can be activated remotely to set off HILTI caps. I have no practical experience of capping, which is why i have come here to ask a simple question for those of you that have done it.

Basically could you give me an average as to how far you generally drill into the rock before placing the charge. obviously i expect a lower and upper limit I.E 60-100mm but i would like to have some idea as to the depth before i manufacture an incorrect length for the firing pin.

For those that are interested, i plan on using a 9mm expansion bolt to grip the inside of the hole, which will hold the rest of the tool in place, with an electromagnet to actuate a hammer that will strike the firing pin, and hopefully set off the charge. This means that the charge can be set off from a distance and will improve safety. (Well that's the basic idea). The manufacture should not be too difficult, as i am an engineer with access to all the relevant tools and materials.

Obviously i am very new to all of this, and i appreciate any feedback that can be given.

Thanks

Sam

 

[nickwilliams]

PM sent.

 

[Rob]

Sounds like an interesting project. Do keep us informed if it works...

 

[Pitlamp]

Another PM sent, with something (I hope) useful to consider in the early stages.

 

[Bottlebank]

Not wishing to belittle the idea, but I can see a few problems, and I'd suggest you'd be far better getting some capping practice in before trying to design it. If you're Dales based you'd be welcome to join us at some point. PM me if you'd like my thoughts in detail, I'd rather not post them publicly.

Huh - do you like it "PM me" - I've gone all "forum"!

 

[sambo]

I think your right bottle bank, as i might be getting a bit ahead of myself here. However due to my job and the fact that i am also completing a part time degree, i don't plan on this being a quick project done overnight. With that in mind i plan on getting as much experience as possible after my exams, which i hope will bring me up to the required standard, and will help me to manufacture the capping mechanism.

i intend to keep you all informed, but you will have to bear with me . 

Thanks for the input guys as well, i will reply to your PM's now.

Regards

Sam

 

[woollydigger]

Have thought about using  air  power I've seen one's on cave digger's.com what could be used with a little. Mod-ing could fire the caps i put a link to it tonight

 

[woollydigger]

The website  is www.mirco-blaster.com let me know what you think?

 

[Rob]

That link doesn't work, here's a working one:
http://www.micro-blaster.com/

Looks like a very useable system, especially the MB 2 which can be fired from a bicycle pump.

 

[blackholesun]

The micro blaster system does look good, but it costs about $700 for the basic spring version and more for the air powered one?

Have you considered trying to make a spring system with a pull cord? It seems like it might be easier (though uglier) than using electromagnets or pneumatics.

I agree that its a worthy goal and if you find capping as terrifying as I do then you'll have plenty of motivation.

 

[Bottlebank]

I agree that its a worthy goal and if you find capping as terrifying as I do then you'll have plenty of motivation.

There've been a few comments on here lately that make me wonder if someone should organise a bit of a capping course - done right it's pretty safe and not at all frightening, admittedly different people have slightly different approaches but I think in general we established what is and isn't a good idea some time ago, and so far as I know there hasn't been a serious injury for a number of years.

 

[paul]

It might be worth viewing http://www.onrope1.com/MicroShaving.htm . "Micro shaving" is a term used in the US.

 

[blackholesun]

I think a capping course would be an great idea, though not without logistical issues. (How to publicize it etc.)

As for my comment, even if I deluded myself into thinking that capping is 100% safe, I'd still find making something go bang at arms reach in a constricted space to be unnerving.

 

[Bottlebank]

If you do review that article bear in mind it's a guaranteed recipe for getting badly hurt. I'm surprised it wasn't amended years ago.

 

[sambo]

Apologies for the lateness of my reply, the last few weeks have been hectic.

I had a look at the micro blaster website, and i have certainly picked up some good ideas. However i am attempting to stay away from pneumatics due to the difficulty in its design as well as increased cost.

I am currently about a third of the way through in designing the capping mechanism. You wouldn't believe how many times i have changed the design. But basically it will now be cocked manually with a cocking handle which compresses a spring, and is locked in position by an electromagnet. Upon firing, the electromagnet will release the bolt driven forward by the spring, which in turn, strikes the firing pin.

Issues that i have identified include.

- This design is a one shot method. If the cap does not explode, the operator will need to return to the mechanism and re-cock the bolt. 

- The electromagnet may not be strong enough to release the bolt if the pressure from the spring is too high. i will only be able to test this once i have made the bolt and bolt housing. I can then clamp  the housing in a vice to simulate the operation.

- This device does not eliminate the issues of having to tap the cap down before firing. From what i am told, this is when a lot of accidents happen due to the rod striking the rim of the cap.

To sum up, some progress has been made, and hopefully i will have a working device within the next few months. 


Sam

 

[Pitlamp]

Will the device operate when the electromagnet is switched on or off? (I ask because if it's the latter, what happens if there's an interruption to the electricity supply when you're still next to it - e.g. someone stands on & breaks the supply cable/battery goes flat/corroded contacts etc?) Switching the electromagnet on to operate the device (rather than off) would be much nearer the fail-safe end of the spectrum.

Not sure about other folk but I use all the PPE (and the mat) as standard when pushing the cap down the hole as well as when actually firing. It takes a few seconds longer but it just seems to be common sense to me.

 

[TheBitterEnd]

I have to say I'd be uncomfortable working near a loaded spring type device, supposing you don't quite cock it right, something fails, etc. and it goes off while you are in close proximity? That's why pneumatics seem better, you can be a reasonable distance away before you even connect the compressed air.

Also how do you hold the device in the hole? What are the expectations regarding accuracy of hole depth?

 

[Pitlamp]

I suppose that if you wear all the standard PPE you'd use without this remote firing device you're no worse off if something goes wrong and considerably safer when it all does go right?

 

[TheBitterEnd]

I guess we will have to wait to see the final device but I can only imagine that either you cock the device and push it in after the caps, or push the device in and then cock it. Either way (unless the device is on the end of a 2' bar) at some point you have your hand around a device with enough stored energy to fire the caps. With the conventional approach the energy is stored in a lump hammer plus elbow grease, these are not applied until you have had time to get your feet, hands, head etc. out of the way.

 

[Pitlamp]

. . . so I presume a capping mat will still be used?

(Good point, TheBitterEnd.)