================================== I, too thought of inset metal load-spreading plates, but the hard plastic castor cups mentioned by the OP (and recommended by Steinway) seem to be a sensible compromise. It gives the OP an option to move the piano to an entirely different position if he should decide to do so without having to re-work the whole of his floor. Of course the OP, if he wished, could prepare a fixed location with inset plates and use the castor cups for occasional use in other locations.
Cic. ================================== Using Ubuntu Linux Windows shown the door ===================================
In fact I face a related problem. I plan to put an upright piano into our 1960s house and the position it will occupy means that all the weight will be one two joists running parallelto the piano. the joists in the house are inadequate; I have alrady had problems with the floor moving when I piled a lot of books on it, so I plan to add some supports under the floor first. i was going to support the centres of all the joists by wooden struts up from the ground each standing on long planks placed on damp-proofing membrane placed on the ground. Adjustment would be by carpenters wedges hammered together and then nailed. I woul ddo the whole floor, to reduce the pringiness, not just the two joists under the piano.
In my case it is the springyness that is the problem, not the danger of collapse.
The finished floor will be thickened by a further 15mm as we have T&G engineered oak floor to go on top of the Caberboard. This should help with the point loading but will not help much with any bounce if there is any.
Metal plates would be a good idea but would be difficult to implement with the oak floor.
It is unlikely that the piano would be moved from the spot. There just isn't the room!
Z is called the section modulus (b*d^2)/6 for a rectangular section as noted earlier B is the width of the section D is the depth of the section I is the second moment of area of the section (b*d^3)/12
The key starting point is that the stress due to bending (f) = [Bending Moment (M)] / Z
To understand how this lot relates, you would need information on basic structural engineering either steel or in the case of this thread timber. Timbers a bit nasty cos there's dodgy variables which affect strength like moisture content, grain direction etc.
160kg on most castors is going to put grooves in a wooden floor IME.
I wondered what the acoustics will be like and if it will hold tune if the floor sags unevenly. Is there a mechanism to level the piano or doesn't it matter?
Have you considered casting some concrete pads under the floor and building some small supporting piers in the correct places? It is probably easy if you are going to cover the floor.
BTW you can get some nice electronic pianos these days that play like the real thing and don't need maintenance every six months, take up less space and are cheap(er).
================================== Seems like a good example of 'Hobson's Choice' then!
If you like the idea of metal plates you might consider three rectangular plates (rather than circular) which could be the exact width of your t&g flooring but each plate long enough to bridge two joists. Short sections of the 15mm t&g could be planed down sufficiently to accept the plates (about 3mm thick) which wouldn't be too visible as t&g is quite normally laid randomly. This would effectively take almost all the weight off the floor boards and put it on the underlying joists.
You could keep a few offcuts of the flooring to make good when / if you eventually move or dispose of the piano.
Hopefully the cups will do that. It is presently sitting on a laminate floor on those cups at my sister in law's , who is piano sitting for us (350 miles away) and they report no damage to the floor.
Yes, this is also a worry... tuning is not cheap and any settlement could put it off tune. Hence the need to stiffen the floor as much as possible.
Thanks this option looks to be the best so far and would be relatively easy to do while the floor is open.
Tell my wife ;-) We did have a Yamaha electronic piano for several years but even to my untrained ear it was not a touch on a proper piano. A concert grand is in a different league yet again.
I am not a music man but I would suggest that, for a steel framed piano of that size, the lack of complete temperature control will detune the piano more significantly than any settlement (which should happen straight away). Thermal cycling found in a normal house with the central heating system would ensure it was never in tune, I suspect! I believe, from what I have been told, that such pianos are tuned prior to concerts and can be heard drifting off (quite frequently) during the performance.
In other words, if the structure stands up, I shouldn't worry about detuning due to physical movement!
I would have thought easier to implement with a surface floorcovering; just cut a neat x mm diameter hole in the oak with a hole saw, and drop in a 15mm thick metal disk of similar diameter. Polished brass might look nice.
Keep some spare oak, and you can cut and insert oaken plugs when you move house, to replace the brass. Save lifting and replacing the whole floor.
Yes they are tuned prior to concerts. Thermal cycling is a worry as is changes in humidity. I think Sister-in-law has had it re-tuned two or three times in the couple of years that it has been at her house.
We are putting TRVs on all three radiators to start with as an attempt to prevent wild temperature excursions but it may be that extra work is needed in this area.
It will probably drift in and out of tune in a cyclic manner which may give us an idea of what to do. My ears don't notice these subtle changes but my wife is pitch perfect so she does. One case where ignorance is bliss!
I just did a quick calc in SB with a 1.3m 4x2" beam. Assuming a uniform floor load of 0.8kN per joist, plus a worst case point load in the middle of the span of 1.6kN (i.e. one piano leg), your current floor fails to meet the spec in bending and deflection - but not by a huge margin. Doubling up the exiting joists with another the same size sat beside it (and nailed too it would probably be simplest at that size), seems to make it stiff enough.
I have downloaded the software from Tony's website and had a quick play. But it is clear that I need to follow the advice on there and print out the instructions! It does seem a very nice piece of software that has the potential to teach me a lot more apart from this question... but I need to learn how to drive it! Also I was very impressed that the only feature 'nobbled' in the demo was the ability to print out the results - fair enough. Nice not to have a time limited demo with lots of features disabled as so many are.
So thanks also to Tony for generously making the software available to non professionals like myself.
Coming back to the joists, I had a gut feeling that deflection would be more than desired and your results back this up although you have quite rightly taken the worst case with the load in the centre of the span. In our case most of the load will be near to a sleeper wall for each leg. But I would rather be conservative and use worst case!
One idea was to double the joists up i.e. putting extra joists in between but in the areas of high load to have double joists joined, but I had thought of glueing them together and bolting through the neutral access. Any problems with glueing and bolting?
I also had an extension to this idea...I thought of cutting 8" strips of
18mm WBP, glueing two together and then sandwiching that between two joists, all glued and bolted. In effect a 'T' beam. Obviously the ply can't extend the total length because of the sleeper walls but that would probably not matter as shear is unlikely to be a problem, I think. Any comments on this idea?
18mm ply glued and screwed to the top of the joists (instead of unglued chipboard) , forming a T beam was a solution proposed by a structural engineer and adopted by me when I did a loft conversion some years ago. We didn't put a piano up there, but the purchasers of the house did install a water bed and there have been no adverse reports from neighbours whom I have remained in contact with. The increase in strength over the unglued floor was impressive, confirming in practice what the Moment of Inertia calculations indicated. We were able to jump up and down on the floor and detect very little spring.
Our joists were 6x2 inches, at 16inch spacing and spanned 12 feet, to give you an idea of our configuration. The resulting stiffness was, if I remember correctly better than what would have been achieved with recommended joist depth for that span. Sorry I can't remember if 8 inch joists would have been sufficient for that span. I remember that the addition of the ply to form a T beam gave lots more improvement over doubling up the beams. Where our span increased to 14 ft . the solution was to double up on the 6x2 beams
I'll try to find my own calculations which I did to "prove to myself" the efficacy of the scheme, and perhaps substitute your 4x2 beams.
She is an amazing woman. Carol originally trained as a concert pianist in Edinburgh and that is where she fell in love with this actual piano that was brand new then (c.1979). As a keen student and with a new piano that needed to be 'broken-in', she was allowed to play it whenever it was not in use. Apparently, she made a resolve that one day she would own it. She gave up music, I'm not quite sure why, and learnt to fly instead. Nowadays she is an airline pilot.
However, she never could never get this particular piano out of her mind and a couple of years ago had the urge to find out what had become of it. My suggestions that it would have been sold on by now were brushed aside and she started making enquiries. Blimey! it was in Steinway's showroom in London, refurbished and for sale! I won't say how much it cost but it was a lot of money.
The next day, or it might have been the day after, we were on a train to London and she bought it. We had nowhere to put it in a ground floor flat! Her sister Elaine, also a concert pianist and piano teacher, kindly agreed to give it a home near Glasgow, in her new extension. Elaine has fallen in love with it too and now has plans to get one of her own.
When I finish the floor in our new house it will be making the long journey South to Crawley to be finally and fully reunited with Carol. A dream that slowly is coming true!
Apart from the fantastic sound when I get the chance to hear it, I just love to look inside it and marvel at the workmanship and incredible engineering.
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