# Tag Info

## Hot answers tagged biomechanics

14

You could just hit a pendulum and measure the angle to which it swings. I have found that three liter soda bottles filled with water and hanging from a rope are good for hitting. Knowing the weight of the bottle, a little trig will give the energy, from which you can get the force. Edit: If the transfer of energy from fist to target happens through a short ...

11

high pulse rate + low pressure means low pumping efficiency of the heart. this can be caused by: leaking valves, especially the main aortic valve, due to disease or calcification; low blood volume, due to bleedout as in bodily injury or an aneurysm rupture; incomplete contraction of the heart muscle due to a breakage or damage in the nerves which carry the ...

10

I think that an impact force sensor is what you're looking for. I'm not sure how expensive the linked sensors are so you could also use an acceleration sensor and do a little math. The second option is likely to be less accurate but I suspect that it will also be significantly less expensive! I know you said that you didn't want the complete system design ...

10

I think what you want is a piezoelectric pressure sensor. You might be able to steal one from an old bathroom scale, but the sensors in a scale may only be good up to ~100 lbs of force. These piezoelectric transducers convert applied pressure to a small voltage across the two leads. This pressure can be converted to force by measuring the surface ...

7

While it is an interesting idea, I don't think a "static treadmill" is going to give you results similar to walking. A PFTE(teflon) surface would be really low friction, but I think there are some bigger issues you may need to address first. Walking is essentially a repeated process of balancing, tipping, and re-balancing. The algorithms your brain uses to ...

7

I'm going to offer a slightly less helpful answer by poking holes in the answers of others to explain why they aren't ideal, then offering an incomplete, poorly thought through answer of my own. The majority of answers here suffer from one of three stumbling blocks: they require unnecessarily large jigs to be feasible with complexities which make them ...

6

Conductive foam will change it resistance when compressed, so it makes a good, cheap force sensor, as long as you have a system to make many measurements in quick succession and remember the one with the least resistance. Depending on the force you want to measure, you can use several layers above each other, and because you can cut it into any shape, you'...

5

I agree 100% with Jeff, the advantage of this is that you could build it for cheap, very, very solid. The height it swings to will give you the energy with the formula $E=mgh$ where E=energy in Joules, m=mass in kg, g=9.81m/s^2, h=height difference in m This will be the total amount of energy transferred to the target. Unfortunately, this amount of ...

5

It's fairly complicated. I found an article in The Bone Journal Comparison of three-point bending test and peripheral quantitative computed tomography analysis in the evaluation of the strength of mouse femur and tibia where they used tomogrphy to calculate inertia. However if you don't have CT you can try the hard way. You'll have to calculate bending ...

5

You are asking for an unrealistic material. If you peruse the engineering toolbox you'll find that the Young's modulus of typical materials is measured in 109 Pa so the value you are asking for is 7 orders of magnitude smaller than typical materials. Even the Young's modulus of the rubber in rubber bands is ~107 Pa. Another simple thought experiment will ...

4

Here is a really cheap and cheerful way of showing the size of an impact. Take 2 boards of plywood, put a large compression spring between one and the other board so the spring is sandwiched but removable by at least one of the boards like an "H". Bolt this to a wall."H|" Get set size balls of playdo (kids putty) place on of these inside the spring (...

4

A strain guage attached to a target would be helpful. Unlike piezzo, they are very durable against impact type force (piezzo crystals tend to shatter when the pressure is applied rapidly). They can be attached to pretty much arbitrary "board" which yields very little, so unlike pendulum types they will not falsify the results with force applied slower, or ...

4

These are few suggestions to develop the system I suggest using a polymeric bladder type approach used in Passage Occupancy Detection Systems in automotive industry. This patent describes the automotive application. The bladder system would be part of the focus mitt, which include a MEMS base differential pressure sensor. When impact force will be detected ...

4

Chronic animal experiment. This is not the only stage of evaluation of the material, but it's a mandatory stage. Chronic means that the animal is survived after implantation for a period of time and observed. Afterwards, the animal is sacrificed and autopsied. Humans have a strong immune system, compared to other animals. So, you would want to use an ...

4

The problem with quantifying impact force is the short duration of what is usually a 'peaky' pulse. Bathroom scales are usually damped to give a steady reading of a static force and won't capture transient peaks. Ballistic pendulums also have problems - some of which have been discussed. However, for training young fighters, I'd suggest that you don't ...

3

There is a fascinating historical collection of mechanisms compiled in the late 19th century here: Mechanical Movements and somebody is working through the task of making animations of them for the website. Manufacturing technology has progressed since then, but the basic ideas are timeless. We used to have a printed copy of this book in our "office library"...

3

If you have to select a material for this application, I would use ultra high molecular weight polyethylene (UHMW). It has a very low coefficient of friction, very high wear resistance, and is a lot cheaper than Teflon.

2

This actually isn't as much of an engineering question as it is a physiology question. There are actually a number of widely used estimates to predict your one-rep maximum, aka "1RM", if you know how many repetitions you can do at a lower weight. See here for more info. All of the methods are based on empirical studies, and are basically look-up tables of ...

2

This is quite a poorly-worded question. After all, how do the layers interact with one another? Can they be considered to be fully bonded to one another? I assume not, because then they've behave as one element, which kind of beats the purpose. Should we assume that the load is evenly distributed between each of the layers (so, for a given load $q$, if you ...

2

This is actually quite a difficult problem. Measuring the work done by a specific exercise output, eg treadmill, cycling, rowing machine etc is easy enough. However this only measures what you might call 'shaft horsepower' and ignores any effort that doesn't go directly into the output being measured. This also ignores the efficiency of the underlying ...

1

There is no general relation between the stiffness and strength of different materials. Also, be aware that in general, the mechanical behaviour of biological materials much more complicated than the "simple" linear-elastic isotropic materials typically used in structural engineering. I'm not a medical expert, but common sense suggests that for a living ...

1

First, I'm assuming that by "moving window", you mean breaking the signal up into smaller chunks and filtering each chunk separately. In the signal processing word, "moving window" would often mean an FIR filter (e.g. fir1() in matlab), but because you explicitly said you are using butterworth filter, which is an IIR filter, I assume that is not what you ...

1

Why not simply record back angle wrt vertical axis in your data then state your assumption that you base your analysis on. Then, the results can be analysed both ways.

1

One very easy solution is to spray the required surfaces with latex based contact adhesive. This is fairly tacky when cured and the spray will also give a bit of texture. Alternatively liquid latex is cheap and easily available and can be applied by dipping the fingertips and/or palm into it. Without fillers or vulcanisation it is not as durable as some ...

Only top voted, non community-wiki answers of a minimum length are eligible