Bridge#2

[buggyman1]

I think you have a fine bridge design, I'm impressed not only with your building skill but also with your structural steel handling skills, those are big beams to get in place without a crane.

Don't know where you are in Kentucky but I have brother that lives down by Scottsville. Very pretty country down there.

Thanks...The beams were a pain, but the Kubota got the job done. Most of ky is beautiful, i'm just east of Lexington.

 

[buggyman1]

My only problem with this project is that I wish you had built it and posted about it before I built my bridge. I'm sure all bridge projects are different but there are some ideas you had that I could have used in my project. Nice job.

Thanks...i'd love to see your bridge, any pics? I bet I could have learned a lot from you're bridge design.

 

[buggyman1]

Bridgeman1, AKA Buggyman1,

I've enjoyed both threads and do hope these will not detere(sp?) you from posting your other projects as well. I've enjoyed the spirited babble, technical talk and basic BS. BTW, you engineers, what does thermo dynamics and stress analysis have to do with driving a train anyway?

Jay

Ditto on the post's by other members, i've enjoyed it also. I plan on posting more projects when i get my lazy butt moving again.

 

[buggyman1]

Remember jayste, you asked. Danno1, your answer is correct; however it doesn't scratch the surface.
Let's take Thermo Dynamics as it applies to trains. The Ideal Gas law; PV=nTR or rewritten as PV/T=nR where nR is a constant and may be written for two conditions [1] and [2] P1V1/T1 = P2V2/T2. Ok, now what? Do you have an Air Compressor? Air enters the compressor at state 1, Pressure 1, Volume 1, and Temperature 1. When the piston moves to the top of its stroke the pressure is P2, volume is V2 at temperature T2. P2 will be greater than P1, T2>T1 and V1>V2. The ratio must be satisfied and predicts the values of P, T, and V of condition 2 starting from condition 1. So now you know why your compressor gets hot. I can't write the mathematical expression with this format in word, but here is a problem that relates to our discussion.

Ten lbs. of air is compressed from 14.696 psi atmospheric and 60 deg F to 60 psi gauge when the barometer is 14.696 psi atmospheric. Find the horsepower to drive the compressor.

a) the initial volume of ten pounds of air is calculated from the Ideal Gas Law;
b) V1= 10 lb. x 53.35 ft-lb/lb R x [60 +460] R / [ 12in x 12 in x 14.696 psf]= 131.0 cubic feet of air. Adding 460 converts the temperature to absolute or Rankin temperature
c) The final pressure is P2= 14.696 + 60 = 74.696 psi absolute. Adding 14.696 converts gauge pressure to absolute pressure.
d) The final volume V2= 10 lb. x 53.35 ft-lb/lb R x [60 +460] R / [ 12in x 12 in x 74.696 psf]= 25.8 cubic feet of air.
e) The Work to run the compressor is P1V1 log V2/V1 or 14.696 x 12 x 12 x 131 x log 28.8/131.0 = - 450,000 ft-lb of work.
f) Hp = work/ 33,000 = -450,000/33,000 or 13.6 hp to run the compressor.

Now this is using the Ideal Gas Law, there are other expressions that are more accurate and more complex.
This is also the fundamental beginnings of other thermal processes, Diesel Cycle, Otto Cycle, jet Cycle.
The nR is the stuff that is the working fluid [air], R is the constant that relates to that fluid, Air is 53.35, steam 85.81, co2 35.13.
N is the number of molecules in the fluid. However it is not that simple, when you have a chemical reaction, combustion than n is a chemical term, moles and much more complex.

So now what do we do with all this compressed air? Air Breaks, in a train yard it's used to move Switch Tracks. Internal combustion engines lose Hp as they gain altutide, at 7,500 feet only 75% hp is available relative to see level. How to get it back? Turbocharger the engine.

Stress Analysis; that is simple too, it pertains to every component in the train that must carry a load or resist a force.
Let's take an axel. The axle must support the weight of the car or engine. Lets say the shear force to fail the axel is 120,000 psi of the cross sectional area of the axel. An axel 10 inches in diameter is 78.5 sq in. 120,000 x 78.5 =9,420,000 lb. or 4710 tons. That's over simplified because 1) there is no safety factor and 2) every half turn of the axel the applied force changes direction. Use a safety factor of 10 and the maximum load is 4710/10 or 470 tons. Take into account spinning the axel and reversing the load and we need to de-rate the load again by 10, now the maximum load is 47 tons. Need to carry more load? Use more axles. BTW, where does the axel load end up? On the rail, more stress, and then where? The track ties and the ground/ballast.

Hope that gives you more insight to the problems.

WOW!!!

 

[buggyman1]

Here's a link to more projects, shop pics, and other things i've made if anyone's interested...(easy on the jack-stands..Transit) I hope this link works. http://www.tractorbynet.com/forums/build-yourself/140181-newby.html

 

[archerm3]

I just wanted to say good job on the bridge!

I also wanted to say to the naysayer naysayers, common sense is not the same thing as clever. Cleverness yields simple workable designs. Multiple iterations yields simple workable designs. Common sense does not. I know plenty of people that have a lot of common sense, or street smarts, that can't figure out which direction to turn a nut or screw. Mechanical ability is not common sense. Ability to detect deflection and failure is not common sense.

Common sense used to tell us that the world was flat.

I can't believe everyone is dismissing Transit's word of caution, from his viewpoint he is just trying to help out based on his own experiences, education, and value system. I know if I was doing anything that was remotely possible to cause a dangerous situation, I would want somebody's input on it.

Plenty of intelligent engineers. Plenty of intelligent die makers and line workers.

Also plenty of engineers that barely passed school. Plenty of diemakers and line workers that barely passed school too.

All of them have opinions, attitudes, and egos.

College is just a place for people to learn from the mistakes of others put in book and mathematical form, instead of having to repeat the mistakes themselves. But until there is a cure for cancer, I would say that the human understanding of science is not quite complete yet.

People don't seem to notice that many junior engineers operate under deadlines to complete designs, they are under the gun with their job on the line, sometimes steps get left out, deflection analysis gets left out, or the light bulb failed to illuminate the clever solution in the 48 hours that job was due under. The line guy that takes the plans and starts cutting/welding has about the same clairvoyance as any one of us watching ESPN on Tuesday morning. "yeah, I told my buddy that that play wouldn't work, by god I was right, I truly am smarter with more common sense than an NFL coach"

As for myself, BSME. But don't take my word for it, let the facts/design principle/math/industry standard speak for itself.

Again, great job on the bridge.

 

[jayste]

Bridgeman1,

AAAAHHHHH!!!!

Sorry for opening that can of worms!! I stand corrected, engineering theories and principles has a lot to do with driving a train! Not to mention you get to wear those cool stripped overalls and that stripped cap...I don't remember seeing a propeller on top of the cap though...??

Anyway, Wow! I started reading all that and it started penetrating my brain like Charlie Browns' Teacher's voice...Wah,wah, wah, wah, wa..w...

BTW, I managed to open that can of worms without all my PPE (personal protection equipment) on! Imagine that!

Jay

 

[RobA]

Thanks...i'd love to see your bridge, any pics? I bet I could have learned a lot from you're bridge design.

Here you go...
http://www.tractorbynet.com/forums/build-yourself/129349-finally-built-bridge.html

I built it for people, horses and ATV's. Too chicken to put the tractor on it.

 

[turbo36]

Here's a link to more projects, shop pics, and other things i've made if anyone's interested...(easy on the jack-stands..Transit) I hope this link works. http://www.tractorbynet.com/forums/build-yourself/140181-newby.html

All I can say is WOW! I wish you were my neighbor, not many people know what an English wheel is neverless have the ability to build one. What is your "paying" occupation?

 

[Transit]

All I can say is WOW! I wish you were my neighbor, not many people know what an English wheel is neverless have the ability to build one. What is your "paying" occupation?

I didn't know it by that name, seen it befor.

Hoboken Station looking East into NY skyline.

So, what is a Geneva Clutch?