Efficiency question: Barco Jackhammer - Simple old technology

  • 50 Replies
  • 20784 Views

0 Members and 1 Guest are viewing this topic.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar

How efficient would this hammer be?



www.gothotrocks.com/barco/barco/barco.htm


With only one moving part & no crank or valve gear it should have a theoretically high efficiency, yes?

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #1 on: 27/07/2009 14:22:29 »
Simplicity doesn't necessarily imply efficiency although I can see where you're coming from.

Efficiency is defined as
Useful work out / Energy supplied

It would be difficult to define the useful work got out of it. That would depend upon the amount of actual displacement of the ground surface that it achieves on each impact.
Work  = force times distance
If the ground is springy, then the hammer will bounce up and, eventually, heat will be generated, rather than useful work in deforming the ground permananetly - lowering the efficiency.

The efficiency could be maximised by measuring the characteristics of the ground - density, stiffness and friction  (lumped together as Impedance) then designing a hammer with the appropriate mass, piston area etc. to match to this impedance.

I'll bet they design them by the suck it and see method and that they have no idea of actual efficiency - just whether they 'work' well or not.

*

Offline Bored chemist

  • Neilep Level Member
  • ******
  • 8736
    • View Profile
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #2 on: 27/07/2009 19:03:57 »
On a trampoline its efficiency would be practically zero (except possibly as a means to commit suicide).
Please disregard all previous signatures.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #3 on: 28/07/2009 11:31:39 »
Okay, yes - good points.
For arguments sake let's assume we are working on some sort of ideal material.
Say the work we want to do is break-up a very brittle material like individual concrete blocks (on a non-bouncy surface). The hammer is ideally 'tuned' to the task smashing the blocks almost to dust then moving on to the next (during the bounce).
so we're not worried about the external losses, just how the hammer utilises each bang.

For a crank engine at least, I am aware that most I.C. have best efficiency at high revs, but I don't know if that applies for this configuration.
The main difference I can think of is that for slow running pistons engines there is more time for heat to dissipate away from the cylinder walls, but I would have thought this is another 'tunable' issue.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #4 on: 28/07/2009 23:53:54 »
To get an idea of efficiency I think you could only hope for a comparative figure. Take a measured quantity of standard 'big' rocks and see the time taken (multiplied by the respective input powers) of two different jack hammers to reduce the rocks to a specified grit size.
That would tell you which one to buy.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #5 on: 29/07/2009 11:08:48 »
I don't see why the best that could be found is a comparative figure between two jackhammers.
It has been pointed out that efficiency is Useful work out / Energy supplied which means that a true quantitative measurement can be given for any machine.

Modern jackhammers use a crank engine (I imagine for smoother & safer operation [I mean look at that thing!!]), but this means reciprocation to rotation and back to reciprocation again.  So apart from not killing the operator are there any other efficiency gains that only a crank engine will have?

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #6 on: 29/07/2009 14:59:21 »
If you could define the conditions of operation so that you could establish the "work got out", then you would have a chance of measuring efficiency. I just think that would be too difficult.

*

Offline Don_1

  • Neilep Level Member
  • ******
  • 6890
  • A stupid comment for every occasion.
    • View Profile
    • Knight Light Haulage
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #7 on: 30/07/2009 08:46:42 »
Do they still use those things, I haven't seen one for years?
If brains were made of dynamite, I wouldn't have enough to blow my nose.

*

Offline Mazurka

  • Hero Member
  • *****
  • 510
    • View Profile
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #8 on: 30/07/2009 10:27:35 »
On the scale shown in the piccy, I guess they have been replaced by hydraulic hammers mounted on excavators.  On small scale jobs hand held pneumatic (or hydrualic) drills are still used - although issues such as vibration white finger are increasingly limiting their use.  The flexibility, ubiquity and work rates of modern excavators on construction sites can often mean it is cheaper to hire in a breaker for a day or two than have all of the faffing about of using pneumatic kit.

For tamping down material such as pipe bedding etc.  vibrating roller or plate machines tend to be used instead of jack hammers.

The picture looks like a health and safety nightmare - the best steel toecaps in the world are not going to stop that hammer...

*

Offline nicephotog

  • Sr. Member
  • ****
  • 390
  • H h H h H h H h H h
    • View Profile
    • Freeware Downloads
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #9 on: 30/07/2009 12:44:13 »
It would be immensley efficient,
-but for fuel yield type and
-full usage of compression ratio
-with the 15:1 parts carburation mix.
Depends what those three points reach.

I wonder if the carburation was effective.
In terms of ware, its efficient.

Amazing they weren't modified over there in the US and turned into motorised pogo sticks.
Did they all get sent to Somalia?
http://www.thenakedscientists.com/forum/index.php?topic=24602.0

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #10 on: 30/07/2009 13:48:53 »
It would be immensley efficient,
But how can you say that if you can't identify the work done? However good the  internal combustion bit is, you may still get nothing useful out of it at all. If the rock it is trying to break up doesn't break - or if you try to break up a trampoline (see above) then there is no useful work.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #11 on: 30/07/2009 20:05:52 »
Okay if its a question of identifying work done (useful or not) then find a large mass of a material that is immune to deformation or cracking at these forces (high grade cast iron?) Stick it and the hammer in a vacuum, then measure how much the worked material heats up. After all where else can the energy go?
One problem: the hammer's engine would need to be cooled, plus some of the heat from it could conduct through the foot to the worked material.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #12 on: 30/07/2009 23:59:47 »
Okay if its a question of identifying work done (useful or not) then find a large mass of a material that is immune to deformation or cracking at these forces (high grade cast iron?) Stick it and the hammer in a vacuum, then measure how much the worked material heats up. After all where else can the energy go?
One problem: the hammer's engine would need to be cooled, plus some of the heat from it could conduct through the foot to the worked material.

Yebbut there would be no 'jackhammer type work' done, in which case the efficiency would be zero.
I can see you are after some measure of output along the same lines as brake horsepower measurement - fair enough. But bhp etc. can be well related to actual motor car performance because the work done is quantifiable.
You could possibly have a defined volume of a defined mix of tarmac which would take a certain amount of energy to compress to a defined percentage of its volume as a standard measure of jackhammer work. 

I guess you could relate a jackhammer output in terms of 'manpower' - how many standard stones a standard man could break into standard small grit in an hour with a standard sledgehammer.
omg, this is really getting daft!

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #13 on: 31/07/2009 09:42:05 »
It would be immensely efficient,
-but for fuel yield type and
-full usage of compression ratio
-with the 15:1 parts carburation mix.
Depends what those three points reach.

The biggest loss as with all IC engines is going to be thermal - mainly heat exiting through the exhaust. Like I mentioned earlier the idea of a high reved crank engine having less time to cool between bangs implies a natural gain in efficiency if things are happening fast (although I can't say exactly why or if that applies to a free-piston configuration [like our hammer]). I'm sure modern carburation and lean burn techniques would improve efficiency by some degree also.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #14 on: 31/07/2009 10:33:08 »
The efficiency of the IC iwill certainly impose an upper limit but, as I keep saying, if you can't match the engine to the job, you can have almost zero efficiency.
The OP asked about efficiency of the machine - not just the combustion bit.
Bearing in mind that the material you're working on will be non Newtonian, the time profile of the impact is likely to have a major effect. It may be that a rotary mechanism with a cam, appropriately shaped, would give an improvement  much moe significant than any choice of motor.
As a lad, I used to see compressed air hammers. They would have a very different time profile.

*

Offline AllenG

  • Hero Member
  • *****
  • 503
    • View Profile
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #15 on: 31/07/2009 17:54:26 »
Do they still use those things, I haven't seen one for years?
I believe that one is used as an earth tamper for compacting soil.
Used when prepping road surfaces for asphalt.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #16 on: 04/08/2009 14:49:28 »
The OP asked about efficiency of the machine - not just the combustion bit.
...
As a lad, I used to see compressed air hammers. They would have a very different time profile.

OK - I want to ask about the 'combustion bit' - how does that compare?

What do you mean by time profile?

Thanks!

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #17 on: 04/08/2009 15:34:43 »
By time profile, I meant the way the force they produce varies with time. With a rotary engine, you tend to smooth this out with the flywheel and multiple cylinders but, with a 'hammering' machine, you need an impulsive force. The way the force varies as the machine operates should affect its effectiveness a lot. So, if you let compressed air in through a valve (like the old pneumatic drills) the force may build up slowly but if you ignite the fuel / air mixture, the force may be much more impulsive.

The efficiency of an IC engine can't be much more than 50% (limited by thermodynamics) but, as I keep batting on about but people don't seem to be catching on, that efficiency can only be realised when the piston is allowed to move optimally. If your hammer is pushing against solid, massive concrete, the only work that can be done is in lifting the hammer itself. The time taken to do this will be very different from the time involved in the head of the hammer penetrating some optimally soft road surface and, at the other extreme, when the head is pushing against very soft (no- existent, even) surface. The optimum will depend on what the IC engine designer would want and the mass and footprint of the head, in addition to the surface characteristic.

As with all things, if you can actually ask a defined question, you may get a proper answer. But this question is too undefined to be answered.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #18 on: 07/08/2009 14:26:59 »
Thanks SC.

I quite agree that the question of efficiency is of course inseparable from load matching.  When we think of most uses for mechanical energy the purpose is generally some type of smooth constant movement (like a rotating wheel or a crane hoist), but some jobs can use the concussive shock of a piston engine directly (like a hammer).

Are there any reasons why this configuration could not be used for pulping wood for instance?

The concussive action would be similar to flail-chipper if properly designed.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #19 on: 07/08/2009 17:50:15 »
You could have a point. Every application seems to use rotary engines these days.
btw, I was looking at a huge beam engine the other day - linear in every way!

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #20 on: 09/08/2009 17:57:36 »
Indeed! Spinney spinney is not always better than upy-downy!
Getting technical now!
I was also wondering if a barco type hammer could be made using a twin-pot diesel engine. Starting & stopping would be more tricky though!

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #21 on: 09/08/2009 21:58:55 »
I have a feeling that you would possibly need an FG flywheel, which might make it a bit of a lump to hold!

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #22 on: 10/08/2009 11:42:53 »
I have a feeling that you would possibly need an FG flywheel, which might make it a bit of a lump to hold!
FG is?

Providing the compression is high enough no flywheel should be necessary (remember it's a free-piston configuration). With two cylinders one piston would be on the compression stroke whilst the other was on exhaust. It would need some valve gear though.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #23 on: 10/08/2009 14:23:28 »
This might work for one cylinder compressing whilst the other is expanding but I think, with the four stroke system, the first cylinder will be exhausting during the ignition stroke of the other.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #24 on: 10/08/2009 14:47:51 »
I'd invisaged:

To start:
Cyl 1 & Cyl 2 -   Lift up, then close decompresser & let drop.
Cyl 1 -   Squash  Cyl 2 -   Blow
Cyl 1 -   Bang    Cyl 2 -   Suck   
Cyl 1 -   Blow    Cyl 2 -   Squash
Then (repeated):
Cyl 1 -   Suck    Cyl 2 -   Bang
Cyl 1 -   Squash  Cyl 2 -   Blow
Cyl 1 -   Bang    Cyl 2 -   Suck   
Cyl 1 -   Blow    Cyl 2 -   Squash

Open decompresser to stop.
« Last Edit: 10/08/2009 14:49:28 by peppercorn »

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #25 on: 11/08/2009 23:22:59 »
I think I see your idea but don't you need bang and squash to coincide as that's the only way to get the compression: letting the engine do it for you?

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #26 on: 12/08/2009 14:04:14 »
Not if you use the tool's weight to compress the air/fuel - although I concede that the tool would be incredibly heavy or the cylinders being seriously undersquare (for higher pressure for equal force).

I see that one piston could drive the compression of the other, but that seems to defeat the object of the design.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #27 on: 12/08/2009 14:12:17 »
The energy used for compression is tiny, compared with the energy from the ignition stroke. After all, mutticylinder, rotary engines do this, effectively.
I can't see a system being popular if the operator had to provide his own compression effort!

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #28 on: 12/08/2009 14:58:32 »
I've been thinking. Perhaps the existing ones must be two Stroke engines???
The link seems to suggest it is.
« Last Edit: 12/08/2009 15:01:56 by sophiecentaur »

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #29 on: 12/08/2009 18:37:00 »
Yes. I'm sure they are (two stroke).
Obviously, it's hardly advanced technology even for its time!

I'm not suggesting the operator has to provide the compression each time just to start then the process then the weight of the hammer takes over.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #30 on: 12/08/2009 18:55:10 »
I remember hearing that wonderful "Doompha Doompha" sound, as a lad. The operator was the coolest one in the team.
Having read more about it, I think you're prob right that two, four stroke halves would be more efficient than the single one. But I'm still not sure of the timing.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #31 on: 12/08/2009 21:20:03 »
I don't know how 'cool' I'd feel operating one of those big ol' things - petrified more like!!  You'd certainly need balls-of-steel (plus toes of steel) to use one of those all day!

I think the timing would be relatively straight forward - just replace the cam shaft with a ratchet.
« Last Edit: 12/08/2009 21:26:20 by peppercorn »

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #32 on: 12/08/2009 23:54:19 »
I was referring to the relative timing of the two cylinders!  [:-\]

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #33 on: 13/08/2009 11:04:02 »
I was referring to the relative timing of the two cylinders!  [:-\]
Is it not just: one goes bang whilst the other sucks clean air - i.e. 180░ out of phase?
« Last Edit: 13/08/2009 11:06:27 by peppercorn »

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #34 on: 13/08/2009 14:03:42 »
But, as I said, if you 're talking fourstroke, I think that the phase isn't right the other way round.

I guess it calls for a picture of the workings you have in mind.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #35 on: 16/08/2009 13:58:03 »
Here's how I imagined it (whilst running):



I have illustrated for spark ignition, but Diesel will be the same cycle.
The cylinders are labelled 1 & 2 with each stage shown down the page.
The bang of one cylinder powers the hammer back up (the conn rod fixed to the hammer end) & draws clean air for the other cylinder. The weight over the cylinders works to compress the gas prior to ignition & exhaust the gas for the other cylinder.
« Last Edit: 16/08/2009 14:06:51 by peppercorn »

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #36 on: 16/08/2009 23:18:34 »
Nice pictures. I see what happens.
You get four stroke efficiency and a bang every time.
There is the same trade off as with a big single pot 2stroke or a twin 4stroke motorcycle engine. It can't 'rev' at a different rate- it needs to dumpha dumpha at the same rate.
You will have one explosion each time from a half capacity cylinder instead of the less than full capacity two stroke power stroke.
There is the weight factor. The whole thing can't be much heavier. But the standard model is probably very heavy in any case, so probably not relevant.
What about the symmetry of the load on the machine? It's no longer coaxial as it has two parallel pistons. A lot of highly impulsive loads could be an embarassment to this slick new piece of kit.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #37 on: 17/08/2009 10:01:23 »
Yes. There would be a tendency to rock the operator from side to side. Maybe it would need some kind of half weighted flywheel (although reciprocating not rotating) to cancel the lateral effect.
Ford used off-centre weighted flywheels on their V4 engines, I think.

Maybe this technology would be better suited to braking up material fed in to a stationary device. As I alluded to earlier, the design could partly pulp waste wood or other dry biomass in batches as a step in bio-fuel (or similar process) production.
« Last Edit: 17/08/2009 10:04:24 by peppercorn »

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #38 on: 17/08/2009 11:36:17 »
IS it all appropriate for a device for pounding roads? It is getting a bit like fitting a gunsight to a clubhammer!

Bearing in mind that all the effective compactors use high frequency impulses nowadays, I think that the Jackhammer, charming as it is (and I'd love to play on one), is probably a dinosaur.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #39 on: 18/08/2009 14:31:54 »
Maybe this technology would be better suited to braking up material fed in to a stationary device. As I alluded to earlier, the design could partly pulp waste wood or other dry biomass in batches as a step in bio-fuel (or similar process) production.

Beats using electric motor or 2-stroke driven machines...
« Last Edit: 18/08/2009 14:34:05 by peppercorn »

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #40 on: 18/08/2009 22:42:45 »
Except that the frequency is, necessarily, very low. This is because there is a large mass which falls under gravity. A rotational system gets over this - which is probably why the jackhammer and beam engine are the only examples I can think of which don't use rotation!

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #41 on: 19/08/2009 10:28:08 »
Yes, of course! Return under gravity is the limiting factor here - I should have realised that!
Although slow & steady might not be a bad thing for every application.


Alternatively, like I think you were alluding to previously, using opposing stokes would overcome this:


The yoke is just for timing the two cylinders and is shown massively over-engineered here for illustration. Power is the red arrows (on alternate strokes).
Clearly, this will only work for two-stroke, but a bit more thought could make a 4-stroke equivalent.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #42 on: 19/08/2009 14:10:00 »
Quote
Alternatively, like I think you were alluding to previously, using opposing stokes would overcome this:
'fraid not - the hammer can't fall any quicker however many times you lift it up. If you fire very frequently the hammer will merely be suspended at a higher average position. It won't return to the fully compressed position if it isn't given time.
See how clever the use of a rotary system is? The speed is only limited by the breathing and the strength of the components.

*

Offline peppercorn

  • Neilep Level Member
  • ******
  • 1466
    • View Profile
    • solar
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #43 on: 19/08/2009 16:48:53 »
Bugger! Really must engage brain!

The original configuration (both pistons in sinc.) would work if material being broken up is forced back up against the hammer (a bit like if the barco was suspended on an A-frame pinned to the ground with a big spring pushing it back down each time). So pulping wood, etc could conceivably utilise a high speed hammer action of this sort.

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #44 on: 19/08/2009 18:15:40 »
Yes, a spring would do it.
Though, there would still be the problem /consideration that your system would have a resonant frequency, set by the mass and spring constant.  Sodding great spring and sodding strong A frame needed!
 
I have just thought of a possible advantage in that the stroke of the system would not have to be constant (unlike the stroke of a rotating engine) so it wouldn't 'stall' but just carry on vibrating with smaller amplitudes.

*

Offline Geezer

  • Neilep Level Member
  • ******
  • 8328
  • "Vive la rÚsistance!"
    • View Profile
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #45 on: 20/08/2009 05:25:09 »
Regarding efficiency, would it be possible to derive some measure of useful work done from the heat generated in the rock? I imagine there must be quite a lot of friction produced while the rock is getting smooshed. (Not to mention the heat coming out of the operator's mouth when the thing lands on his toe.)  [:o]

Measuring the temperature increase might be a bit tricky, but perhaps not impossible if you had some sort of "calibrated" rock in a well insulated setup.

There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

*

Offline nicephotog

  • Sr. Member
  • ****
  • 390
  • H h H h H h H h H h
    • View Profile
    • Freeware Downloads
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #46 on: 21/08/2009 13:53:15 »
Quote
If the rock it is trying to break up doesn't break - or if you try to break up a trampoline (see above) then there is no useful work.

I'm well aware that work-done is an expression of used-levels-of-resource-expended-SUCCESSFULLY.

It's in context of fuel used per strike / per time to achieve the cycle of load - reload in the sequence of moving the hammer,
the fuel yield and gravitational attraction and inertia never will actually change(at least for the fuel grade).

*

lyner

  • Guest
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #47 on: 22/08/2009 23:06:52 »
The clue is in the term 'useful work' which is essental to know before you can calculate efficiency.
If you can't specify that then you can't know the efficiency. The only hope of some sort of idea would be amount of flattening of a specific thickness of Tarmac or breaking of a specified sample of stones. Neither of these could easily be related to 'real life' work situations.

*

Offline Geezer

  • Neilep Level Member
  • ******
  • 8328
  • "Vive la rÚsistance!"
    • View Profile
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #48 on: 23/08/2009 05:39:55 »
All measurements of efficiency MUST be related to "real life" situations, otherwise they are entirely meaningless. There is a set of "real life" assumptions behind every measure of efficiency. They may be explicit, but they are more commonly implicit.

In the case of the "instrument of dread" in the photo, its main purpose is to compact aggregate and soil. Devising a method of comparing its effectiveness compared to the alternative methods should not challenge your average fifth year pupil too much.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

*

Offline nicephotog

  • Sr. Member
  • ****
  • 390
  • H h H h H h H h H h
    • View Profile
    • Freeware Downloads
Efficiency question: Barco Jackhammer - Simple old technology
« Reply #49 on: 24/08/2009 03:25:55 »
Quote
sophiecentaur: Neither of these could easily be related to 'real life' work situations.

Would measuring the resultant "mode" of the tarmac p/cm and in a grid do that?
avg.pdf www.nicephotog-jsp.net fortran95 "Plato IDE"
What a thought for MATLAB