I need a good quality wooden artist's model; in which the balls joining the legs with the hip can twist.?
The ones I've found that are readily available around town in Michaels, Hobby Lobby, Barns & Nobel, etc. aren't very good quality in the sense that they aren't nearly as flexible as I need them to be. I need to be able to twist and turn the legs; make them be able to sit spread-eagle and such. And if they're the magnetic kind which you can take off the base, that'd be even better; I need 2, and so I'm going to end up sawing the metal pole off of one of them at least in order to do what I need to do with them.
Strength of properly welded joint is more than parent metal. Is this statement true?
‘The strength of welded joint is more than parent metal’.The answer to this depends on what type of weld you are using(butt weld, lap weld, fillet weld etc) and the amount of filler metal or the molten metal penetrates in the joint i.e. is it full penetration weld or half penetration. Besides this the type of strength test you want to perform on weld joint.Here are some examples of the strength of welded joint with respect to parent metal.For butt welds the most critical form of loading is tension applied in the transverse direction. It has been observed from tests conducted on tensile coupons containing a full penetration butt weld normal to the applied load that the welded joint had higher strength than the parent metal itself. The yield stress of the weld metal and the parent metal in the HAZ region was found to be much higher than the parent metal.Fillet welds are broadly classified into side fillets and end fillets. When a connection with end fillet is loaded in tension, the weld develops high strength and the stress developed in the weld is equal to the value of the weld metal. But the ductility is minimal. On the other hand, when a specimen with side weld is loaded, the load axis is parallel to the weld axis. The weld is subjected to shear and the weld shear strength is limited to just about half the weld metal tensile strength. But ductility is considerably improved. For intermediate weld positions, the value of strength and ductility show intermediate values.I hope this helps you. For any questions for this answers please comment.-Nainesh.
How would you make a 3-D model of a blizzard?
My friend and I are doing a project in our science class on blizzards as part of our exams. For our presentation, we need 2 visual aids and a 3D model. He's already gotten one visual aid. I'm in charge of making the model. The only problem is, I don't know how to make a model out of a blizzard. We're also making a video of it tomorrow, so basically we're going to show it snowing on a town or something. Does anyone have a clue how to make a 3D model like this?
Why are gaps left in between rails when laying a railway track?
In traditional railway construction, rails are laid down over sleepers, clamped to them and then fastened to one another by means of fishplates. These fishplates not only help the whole track structure to maintain its integrity, but also ensure that a certain (small) distance between rails is kept. This is due to thermal expansion.All solids expand (increase in size) in a certain measure when subjected to high temperatures — and contract when cooled. This is a basic thermodynamic fact: molecules always vibrate and when heated, this vibration increases, slightly expanding the bulk of the material. When the main dimension of a solid is linear (like in rails) we talk of linear thermal expansion. This effect can be modeled with a constant coefficient for ambient temperatures. Rails are made of a steel which has a linear thermal expansion coefficient of around 12 µm/(m·K). That is: each meter of rail expands 0,012 millimeters for each degree of temperature increase (Kelvin and Centigrade are the same “size”, and being a relative measure it does not matter which one we consider).In practical terms: let’s assume we are using 90 m rails at 15 °C. What will be the rail length in a hot, 40 °C summer day? Computing 12 × 90 × (40 – 15) gives 27000 µm, that is, a whopping 2.7 cm which must be accounted for when laying down tracks, lest rails expand beyond the dilation clearance and start pushing against one another, risking sag and perhaps a derailment. Dilation clearances between rails are best calculated for the most usual temperature at the locale.Modern railways employ continuous soldered rails and track expansion devices at regular intervals (and usually at the start and end of bridges, tunnels and other structures) to avoid the maintenance problems posed by rail thermal expansion and to increase rolling comfort.Images from Images from Tano4595 - CC BY-SA 3.0, File:Junta de vía.jpg and Ferropedia - CC BY-NC-SA 3.0, Aparato de dilatación de vía.
Why do we prefer PVC pipes instead of iron pipes?
PVC pipe is preferred in many scenarios because of the ability to cut it quickly (in 3–4 seconds) as opposed to cast iron which would take up to 30 seconds for a 4 inch piece. PVC is obviously a lot cheaper than cast iron but there is a lot of argument for cast iron even today.First of all, cast iron piping is a lot less noisy than PVC and can withstand water temperatures of over 160 degrees F, which PVC cannot.The downside presented in cast iron pipes is that after a couple of decades, rust buildup can drastically influence the ease of water flow and they have been known to clog up easier. However, modern cast iron pipes are spun cast, unlike the olden days, which makes the pipe wall much more consistent and helps prevent against clogs.Back in the sixties, installing cast iron pipe used to take much longer but now the ability to install cast iron pipe is as quick as it is with PVC.
Since train tracks are metal, why don't they expand in warm weather and buckle?
Since train tracks are metal, why don't they expand in warm weather and buckle?They sometimes do. In the United States these bucklings are called “sun kinks”. When I was on the railroad, my regular crew hit a sun kink while I was on vacation and derailed in three places. Tank cars were still blowing up hours later. Fortunately, nobody was injured, including a boxcar of Mexican nationals in the middle of the mess.I experienced a sun kink once where the rail was bent about six inches to a foot out of alignment. It probably looked worse than it was. The engineer braked the train, and then kicked the brakes off before we hit the kink. You don’t want to be braking the train while going over a kink, because the slack running in and out can force cars off the track if it coincides at a kink. When we hit the kink, there was a quick side-to-side movement, and then we were over it. I looked back and saw each car in turn do the same thing. This time, nothing derailed. I think locomotive and railcar trucks are designed to be able to handle such quick movement side to side to a certain extent.Sun kinks happening on curves bulge to the outward side of the curve. Sun kinks on straight track can go either way. Look at the following video at how quickly a sun kink happens. Sometimes, it is the vibration of the train that encourages the kink to occur.In the old days of 39-foot rail sections, expansion wasn’t much of a problem, as there was room for a little expansion at each rail joint, but with modern welded rail it is a problem. Normally, welded rail is laid during warm weather when it is close to its expanded length. Then, when the rail contracts in cold weather, it is not as big a problem.Another way to minimize the effects of expansion in welded rail is to place a section every so often where the rail can slide on itself when it expands. See below.Col André Kritzinger [CC BY-SA 3.0 (Creative Commons - Attribution-ShareAlike 3.0 Unported - CC BY-SA 3.0)], via Wikimedia Commons:
Should i leave my prop up or down over the winter season?
1st, have it winterized, or if you know how do it yourself. if you dont know how, feel free to ask. but please provide more info, year, make and model of what its powered by. 2nd, wash it very well and once dry cover it very well. cover should be in a tight tent like shap so water and/or snow dont stay on it. 3rd, leave the prop, or rather the drive/outboard down. prop shaft is also the exhuast and cooling water exit on most models, if its in the up position water will stay in it. 4th, your drive/outboard should also be covered, so it wont be exposed and no water can get in it. you should also cover the tires on the trailer, sunlight rots them. most people dont wear out trailer tires before they have to get replaced, shelter them from sun and you get a better chance of getting full mileage on them. 5th, you most likely have a sterndrive, all sterndrives have rubber bellows, depending on make and model it may have three of them, exhuast, shift cable and u-joints. when fully turned or raised teh bellows are stretched. down and straight and they are most relaxed.
Does my knee replacement prosthetic weigh more or less than my previous real knee? (I have a Genesis II).
That's a good question, and actually a frequent one that is asked by my patients. Its important to understand the different pieces that comprise a knee replacement. There are two major materials used. The first is usually a metal alloy, but sometimes can be a ceramic material. The second is a specialty plastic called polyethylene. Source: (The knee replacement component types)The image above is missing one of the plastic components that is frequently used on the knee cap (which was removed for easier visualization on the model).There are some variations on these components depending on the manufacture. However, in general these pieces typically weigh about the same. One difference that could occur is if a specialty prosthesis is used for ligament deficiencies or in "revision" situations. Those prostheses may have stems that go into the thigh or shin bone (or both) and will weigh more.During the surgery, the surgeon will remove a small amount of your own native bone. However, the weight of this bone is minor. I have never actually put the bone on the scale and weighed if after the resection was complete, but in my hand the pieces do not seem very heavy.The prosthesis that I use frequently is the Depuy Attune system. According to a representative, the average knee replacement for the Attune weighs in at .94 pounds (less than one pound). This will vary by size, as the larger prostheses (larger knees) will weigh more.Most surgeons also cement the components to the bone which adds some further mass. Overall, I believe that the replacement does add a small amount of weight to your knee once all of the healing and swelling has completed after a year.