Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site psivax.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!qantel!hplabs!sdcrdcf!psivax!friesen From: friesen@psivax.UUCP (Stanley Friesen) Newsgroups: net.origins Subject: Re: more on dinosaurs and load-bearing Message-ID: <723@psivax.UUCP> Date: Sat, 14-Sep-85 11:23:24 EDT Article-I.D.: psivax.723 Posted: Sat Sep 14 11:23:24 1985 Date-Received: Thu, 19-Sep-85 05:47:49 EDT References: <391@imsvax.UUCP> Reply-To: friesen@psivax.UUCP (Stanley Friesen) Organization: Pacesetter Systems Inc., Sylmar, CA Lines: 105 In article <391@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes: > > The objection that any animals thigh is wider than its calf or ankle is >irrelevant; a ten foot wide animal with ten foot wide THIGHS is impossible. Why is it impossible? I see nothing *intrinsically* difficult about it. See below for a fuller explanation. >If you insist that the ultrasaur's thigh was only 8 feet from side to >side, I will just as logically insist that it was then necessarily 12 or 13 >feet from back to front, still impossible on an animal whose body was 25 or 30 >feet long and 10 feet wide. > Well, here is part of your problem. You have the beasties measurements wrong. A Sauropod only 25 to 30 *feet* long would be the *smallest* one I have ever heard tell of. The correct size is more likely to be 25 to 30 *yards*, in which case a width of 10 feet would be ridiculously thin! A width of 25 feet would be perfectly reasonable, pehaps even a bit wider. At that width two 8 ft wide thighs would only add up to 16 feet, or about half the total width, which is again quite reasonable. Of course all this assumes your estimates of required muscle mass are actually correct. > The notion that the dinosaurs thighs were more efficient than Kazmier's is >simply wrong by a very wide margin... > (A list of speculative factors supporting this claim) Well, as has been pointed out, there are other factors which point the other direction, so we have now reached the limit of Aristotelian a priori reasoning. It is time for an experiment. The best one I can think of is to measure a number of species of animals of various sizes and plot the weight supported by a leg versus the average diameter of that leg. This will produce an allometric equation which estimates the size of leg expected for animals of various sizes. It will be "conservative", that is it will *over*estimate the required diameter. It then becomes a matter of extrapolating the curve to the size proposed for the Ultrasaur, and hope that the extrapolation is valid.(This is because *any* extrapolation beyond your data is somewhat suspect, since the curve may change just beyond the end of available data). > >.... I further believe that I DID that. There are >several points I didn't even bother to mention because I thought they would >occur to anyone who thought about it. These are: > > 1. The HUMAN leg being the more efficient, as demonstrated. Well, your "demonstration" was more an argument from reasonability than a real scientific demonstration. In fact since you ignored leverage, it is quite doubtful that it is correct > > 2. The fact that I was comparing what the human could lift when fully > warmed up to the load the sauropod must face when getting up after a > nap, totally cold. Who says a Sauropod would *get up* from a nap, like many large animals today it would probably sleep on its feet. Also, they may well have been warm-blooded, so they wouldn't cool off sinificantly anyway! > > 3. The fact that I was comparing what the human could SQUAT to the load > the sauropod must lift OFF THE GROUND. > See above, why lift? > 4. The fact that the constant K itself would not be as high for the > sauropod as for the maximally trained human athlete. > Why not? They would be constantly "training", since survival in the wild depends on good health and adequate strength. > I am not going to quote Mr. Friesen's article here; it is on the net. >Basically, he claims that a Mr. R.M. Alexander has computed "load factors", >based on the stress that BONES can take, and determined thereby that dinosaurs >could function normally in our world. Is there a problem with that? Anyone >who has watched houses being built knows how much weight an ordinary 2x4 can >bear when stood end on end. Bones are like that in a way. Take my own humble >middle-aged body as an example. I am about 6' 4", 207 lbs, somewhat stronger >than the general run of my fellow middle-aged businessmen, but I am no >powerlifter. I have friends who are; they are a whole lot stronger than I. >Nonetheless, if I kept my back and legs straight, and two of these friends were >kind enough to put a bar with five or six hundred pounds on it on my shoulders, >I could stand with it; the bones would not break. Mr. Alexander would no >doubt then conclude that I could function quite well at 700 or 800 lbs (my 200 >plus the bar). > No, his conclusion would be that you have sufficient structural leeway that you could run fairly fast without breaking your legs. Remember, he was mainly concerned with *gait*, but an animal that has the capability of a slow run certainly can *stand* on land. Try running sometime, see how hard you pound your feet(and legs) against the ground, you will realize just how much *extra* tension is placed on your legs every stride. In fact if your support ratio is only ~4.0 you could not even run! That is a worse ratio than an Elephant! As a matter of fact 800/200 is almost as bad as the *worst* of the Sauropods! I rather expect that your *bones* could stand a whole lot more. The basic point is that the limiting factor here is not standing on land, it is the extra impact sustained during locomotion, and this requires structural support, not muscles. Muscles can always be adjusted as necessary. -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa Brought to you by Super Global Mega Corp .com