As I try to keep my sword sharp in the midst of the hardest semester of my collegiate career, I have come to the conclusion (at the suggestion of my wise, big sister) that I should attempt to write and study about where I see God in my course work (I’m certain that a study of the burning bush while I was still in Heat Transfer would have had rich rewards – perhaps I can conduct it someday).
So come with me on a journey of which I know neither the extent nor the duration. My academic studies have taught me so much about the mechanics of the world we live in. But it’s God’s world, high time I remembered that fact while I’m learning about it.
In my Machine Design class last week, my professor was talking about design safety factors. 95% of everything we use was manufactured with a design safety factor, and the other 5% is what is commonly referred to as “cheap junk.” Ever seen a “Don’t put more than ____lbs on this____” sticker on something? If the label said 50 lb, you still wouldn’t expect it to break if you put 51 lb on it. That’s the design safety factor kicking in. If a kitchen chair needs to hold a 250lb person, whoever designs the chair will make sure it can hold 350lb.
Obviously there are different levels of safety factors. The strength in the threads in your socks to withstand dozens of washings isn’t as important as the brakes you expect to bring you to a stop at a red light. Sure, you can make socks out of Kevlar, but unless your coffee table’s legs have stepped up their game and have started trying to assassinate your feet with AK-47’s - it’d be a waste of money. So there’s also a problem of being “too safe.” Why would your kitchen door need hinges made out of 1in stainless steel with tungsten pins? - wouldn’t make sense. It’s a waste of material and space.
So, here is the list of considerations that go into calculating the required safety factor.
1. Accuracy of loads knowledge
2. Accuracy of stress calculation
3. Accuracy of strength knowledge
4. Need to conserve material or money
5. Seriousness of failure consequences
6. Quality of work in manufacture
7. Conditions of operations
8. Quality of maintenance
All of that has to be taken in to consideration when you’re designing something. If you know that it will be very difficult to maintain your product, or that it will be operating in harsh conditions, you’d better step up the quality and quantity of your materials, but it’s a delicate balance. Aircraft commonly have a safety factor of 1.5, much lower and the first time the plane encountered worse than average turbulence the wings would tear off, much higher and the plane would be too heavy to fly.
Now, take a moment to look at the back of your hand. Move your index finger up and down and see the tendon attached to it move. Now think about how you told your finger to move, or how if you cut your finger it would repair itself. The bones in your fingers don’t have a 2in diameter, nor are your tendons made out of an organic metal – God could have done it that way if he wanted to, but hands like that would be over designed for the world he put us in and would have been very cumbersome to use for delicate tasks. Conversely, you don’t worry about breaking your fingers every time you bring in the groceries. Our hands can defend us, hold our children, build houses, sew clothing, pick flowers, or dig post holes.
In the words of my professor:
“The human body is brilliantly designed.”
In the words of King David:
Psa 139:14 I will praise thee; for I am fearfully and wonderfully made: marvellous are thy works; and that my soul knoweth right well.
Ecc 11:5 As thou knowest not what is the way of the spirit, nor how the bones do grow in the womb of her that is with child: even so thou knowest not the works of God who maketh all.
Think of all creation: all the different species in all the different environments that have lived together on this planet for thousands of years, sustained with water moved across continents in clouds miles above the earth, that feed on vegetation that dies back in the winter but grows back in the spring, or of the 500 different species of bacteria living in your gut that greatly aid in the digestion of food but could kill you if they got out of balance. Yet it all hasn’t come to a screeching halt because of a design flaw or something the manufacture cut a corner on to save money.
Ecc 1:7 All the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come, thither they return again.
I highly recommend reading Job 38-41 where God does an excellent job (Job, job - ha) declaring the wonders of his creation - the work of his fingertips.
Psa 8:3-4 When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained; What is man, that thou art mindful of him? and the son of man, that thou visitest him?
That’s all for now, but perhaps I’ll be led to look at that list of 8 considerations in a little more detail. Just of the top of my head, here are some closing verses that go with the first three.
1. Accuracy of loads knowledge
2. Accuracy of stress calculation
3. Accuracy of strength knowledge
Psa 103:14 For he knoweth our frame; he remembereth that we are dust.
Isa 53:4 Surely he hath borne our griefs, and carried our sorrows: yet we did esteem him stricken, smitten of God, and afflicted.
Heb 4:15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin.
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