Alrighty. I bought a massive piano and it will be delivered this week. I live on the 3rd floor. I feel bad for the movers, so I’m trying to figure out easier ways to do things than with simple brute force.
The stairs are at a 32 degree pitch. It’s a 700 pound piano, after removing the legs and the lid. If I put the piano on rollers and haul it up a ramp placed on the stairs (assume it’s one straight shot, no turns), I would need to pull with just 371 pounds of force to get it up there (700lbs * sin32 to get the component of the weight that acts down along the slope). Not too bad.
But what if they decide to just carry it up between 3 or 4 people? For simplicity’s sake, let’s assume there’s one really strong person on each end. How much weight will each person have to hold? That’s a completely different problem, right?
I appreciate your help, inasmuch for the practical value as the academic exercise. I need to be able to do this stuff on my own!
The times I had to move a piano three fit people could just move it and only changes in height of about 3 feet occurred. I’d say four fit people is the minimum that should try to move a piano, and that doesn’t included 3 stories of stairs. I hope you made the movers aware the a huge piano was being moved. A ramp on the stairs you will have a heavy piano on and people walking up is a disaster likely to happen. Try not to get somebody killed.
I wouldn’t even worry about it, really, as a practical matter. Piano movers may not know the physics involved, but they’re the experts; let them decide how best to move the thing. It’s what they do.
Now, if it’s just an academic exercise you’re interested in, then carry on.
Q.E.D. is, as usual, right. Piano movers are extremely strong and experienced at what they do. I’ve seen one guy carry a spinet up two flights of stairs on his back, and two guys moved my 727-pound baby grand up one flight into my condo.
Don’t bother trying to suggest a better method to them. They know what they’re doing. And if they don’t, and drop it, it’s on them. If they follow your suggestion and damage the instrument, at least some of the fault is yours.
If we assume for the sake of simplicity that the center of gravity of the piano is more or less in its geometric centroid, it’s going to weigh 700 lbf/3 = 233 lbmf(or 700 lbf/4= 175 lbf) for each of the movers regardless of how they orient it (although in practice, the guys on the uphill side will generally be carrying less of the weight because of the ergonomics of the situation). Since either of these weights is far in excess of what a normal person can carry for any distance, the movers will, as Q.E.D. notes, already have some technique and/or equipment for doing this.
I’ve never moved a piano, but I have moved heavy equipment and loads weighing several hundred pounds each (generator, cement mixer, construction supplies) up a hillside and back down the other side. This was accomplished by laying improvised rail, then hitching the load to a pair of comealongs secured to several trees. The tricky bit was actually the crest; owing to reasons to complicated to explain, the rails on each side were offset from one another and the load had to be lowered onto rollers, maneuvered into position for the downhill rail, jacked up into position and rolled onto the rail. Amazingly, nobody got hurt and we never lost control of the load, but in retrospect it would have been far easier to just blast a temporary road through the hillside and hauled that stuff on the truck rather than the business of going overland with it, although at the time I was thinking more along the lines of a really big trebuchet and a diesel semi-tractor just flinging that crap over the hill and then walking away.
Stranger, you’re usually fabulous with physics (especially theoretical physics), so I regret to say that in this instance, you are mistaken.
If you and I lift a piano of moderate weight, say 300 pounds, and it is level, we will each carry 1/2 of the load. However, if I lift my end higher than yours, I will certainly be carrying less than 150 lbs, and it has nothing to do with ergonomics. If I put each end of the piano on a scale, one higher than the other, they would register very different weights. What I want to figure out is, how does that change relate to the angle at which the mass is supported? Surely someone remembers their statics class better than I…
Stranger, you may be right in that the *force * required is evenly distributed, regardless of the slope, for the case where everyone has a handle on the load they can hold onto; in other words, the person in front can pull forward as well as up. Even so, I’m not sure the sum of the forces exerted by each person equals the total weight of the piano.
Imagine if the piano is completely vertical - the entire weight in this case, obviously, will rest on the person holding the lower end of the piano. If the piano is horizontal, the weight is evenly distributed between the two carriers. Therefore, if the angle of the piano is somewhere between vertical and horizontal, the weight distribution must be somewhere between 50/50 and 100/0.
Come on, Ray, these people aren’t engineers - they may not have even taken high-school physics. They just haul stuff the easiest way they can think to do it. That doesn’t mean there isn’t an easier way still. There’s also a lot to be said for tact and the way in which one makes suggestions.
By the way, if someone were to tell me an easier way for me to do *my *job, I would be *very *grateful.
I operated a moving van for 10 years and moved many pianos. If a customer had told me how they wanted their piano moved, I would have informed them that I was experienced and knew how to best accomplish he job. If they insisted I would have had them talk to a company rep., who would have informed them that the customer would accept responsibility if they insisted on supervising the work.
I don’t recall if I took HS physics or not, but I know how to move a piano, even up several flights of stairs.
You might contact the moving company to assure that they realize the difficulty of the job and are sending experienced piano movers, but do not interfere w/ the actual job, even if you don’t agree w/ their method.
If they complete the job w/o damaging your piano, give them an appropriate gratuity, they need the money since they probably don’t have the benefit of higher education. :dubious:
BTW, I just told you how to do your job, as a customer. Do you feel grateful?
They also presumably have the experience of generations of piano movers to guide them. It’s not like the moving company hires these guys and sends them out with no training. They don’t want to get sued or stuck with the cost of replacing a damaged piano. They WILL teach their people how to their jobs in the most effective and safest manner that past experience has proven out. I rather doubt you can improve upon it, regardless of how many linear equations you solve.
When I say that each of the workers will be carrying a proportionate share of the load, I’m assuming that “a horse is a sphere to make the math easier” (which is an old engineering joke and Q.E.D. is rolling his eyes about now). If we’re talking about a rectangular box in which the center of mass is at the geometric centroid, then taking it by opposite corners–that is, the uphill guys grab the bottom forward corners, and the downhill guys grab the upper rear corners–will keep the load centered between them, whereas you are assuming that the workers each hold the bottom corners regardless. Now, of course it usually doesn’t work like that; in order to physically keep hold of the box and make sure it doesn’t fall backward the guys on the downhill usually have to get underneath it, getting closer to the centroid, and the guys at the top may have to rotate it up, and thus taking an even smaller portion of the load. But in an ideal world, where there are handles on all of the corners and the stairs don’t get in the way, each worker would be carrying only his percentage of the load. The only reason the piano movers would end up taking a higher portion of the load is because they don’t stay at the outer extents of the piano; the guys in back get gypped into moving closer to the c.g.
Regarding your latter question–what is the effect on static load when you rotate a object “hinged” at one end–it depends on how high the c.g. is when it is in the initial orientation. The higher the c.g. the faster load will be transfered to the hinged end, and the easier it is to cause it to tilt over center and fall; conversely, the lower it is, the further you have to push it to make it to over center, and thus it is more stable. (This is, all things being equal, why passenger cars have much lower incidence of rollovers than high-centered SUVs.) You can visualize this graphically by drawing a box and following the path of the c.g. as it rotates about a corner, and you can calculate this as a function of the horizontal component of the vector from the origin (hinged corner) to the c.g.
For instance, if the box is 8 feet wide and the c.g. is located 3 feet up from the bottom, the distance to the hinged corner is r= 5cos(arctan(3/4)+θ ). where θ is the angle at which you’ve rotated the box (so initially θ=0° ), while the horizontal distance to the lower non-hinge corner of the box where you are lifting is R=8cos(θ ). The ratio between these two (r/R) will give you how much of the load you’re carrying. (Technically you need to take the moment about the hinge point and set it equal to zero, then do the algebra, but it works out to the same thing.) Once you tilt the box more than 53.1° (for this particular example, I’ll leave it to you to back through the trigonometry), r≤0, the c.g. will be over the hinge, and now you’re going to have to pull back in order to keep it from falling over away from you.
I’ve looked online for an image to show this but didn’t find anything that satisfied me as being clear (although there are a lot of good statics tutorials online) but you can find this in any basic physics or statics book.
On behalf of regular people everywhere I’m officially disgusted right now. And yes, I take into account things like flow and pressure drop and static pressure everyday while designing emissions controls and test systems, and I’ve never even taken a physics or engineering course! I guess I just somehow picked it up along the way. Unbelievable, I know…
Or have a mover make an unnecessary Workman’s Comp complaint or otherwise expose themselves to undue liability. I agree that the o.p. is best to just stand aside and let the movers do their work without comment or suggestion. My interest in this exercise is purely academic.
Thank you Stranger. I understand your explanation above, I think it makes good sense. That works as far as answering my question, which no one else in this thread has even attempted to do, if I may be so blunt.
And to everyone else who has commented in this thread, I would like to make it very clear that when these men are working on *my *property, on *my *stairs, with *my *fucking piano, I am responsible for their safety and the security of my piano. I know I will not be held legally or financially responsible by any means, but that doesn’t take away my professional or moral responsibility to make sure that I understand what they’re doing, and to help if I can. That doesn’t mean I’m going to start barking orders as soon as they get here. It simply means I will have assessed the situation, possible methods of execution, hazards of the operation, and ways to minimize those hazards. It’s the least a responsible person can do, in my opinion.
Fuck you and your tiny little mind, QED. I already told you, I *know *that I am not liable, but no amount of insurance will make me feel better after somebody maims himself right in front of me, just because I was too much of a faggot to speak up when I saw something was wrong. Obviously, you don’t give a shit about the safety of others around you. You watch your back and I’ll watch mine, is that right? What a trophy to society you are.