General Engineering Discussions

What's "wrong" with young engineers?

Leslie_Gordon — Thu, 15 Oct 2009 17:05:28 GMT

A letter from a reader posted on the recent CAD/CAM e-newsletter about "what's wrong with young engineers?" provoked a flurry of responses. Here are the comments:

    * Great commentary. Looking at the last statement: "At the risk of sounding nostalgic, maybe there is a need for "the good-old-days" skills when we used our minds, not computers, to derive answers." I would expand this statement to say, "...used our minds and our hands..." The company where I work is privately owned with several thousand employees worldwide but is headquartered in rural Ohio. I've heard the term "farmer-engineer" several times in reference to local engineering staff. A number of these individuals are actively engaged in farming on the side while working as engineers. They have a good sense of "what the appropriate answer should be" because they have twisted off a few bolts in their time. Furthermore, they are very creative, having repaired farm machinery or welded up some useful device in their farm workshop. They know from firsthand experience the effects of weld draw from excessive heating, how cracks propagate through a joint, and how the laws of physics can work for or against them. My preference: Give me an engineer who has an engineering degree but also has had a little grease under his fingernails. I've been using CAD since 1985 and absolutely love it, but without some practical common sense knowledge, computer programs only help you make mistakes faster!

    * Nothing that experience and working for an experienced engineer won't cure. These kind of errors happen all the time with new engineers — they have the "book smarts" but won't have the application smarts until they get some seasons under their belts. The concern I have is when these jobs get outsourced, who will be gaining the experience to review the work done on the other side of the globe? Companies that sell outsourcing solutions tend to work with the newest of the new. Your experienced engineers might catch their mistakes now but what are these companies going to do when their experienced engineers retire?

    * I agree wholeheartedly with your opinion. But it is not limited to young engineers. One must always step back and make a reasonableness check of their design. We get lazy and let the computer tell us what is right without questioning the answer. Of course, a few years experience designing stuff that doesn't fall down helps in making the reasonableness check. I am a professional Civil Engineer in California. Former Asst G.M. for water at the Pasadena Water and Power Dept. I had an engineering staff of about 50 people.

    * I have to agree. I went through engineering school with a calculator, but I was taught by teachers who used the slide rule. I developed an appreciation for the "old school" way of thought. I fear the engineers of today, who are being taught by "calculator guys," have less of a grasp on general physics as well as the importance of simply keeping track of your units! I walked into a lab one time and asked if there was an analog ammeter available. Everyone just about fell out of their seats. The few engineers in the room who actually knew what one was, tried to convince me to use a digital one. New engineers think that digital is the answer for everything. The real shame is that they were only a few years behind me. Sure, I'm a calculator, but let me be taught by a slide rule.

    * I was reminded of this article that was recently mentioned in a recent AMSER bulletin (if you don’t subscribe to The Scout Report and The AMSER Bulletin – both free - then may the bird of paradise fly up your nose!  ) In my experience the only serious mistake young engineers make on a regular basis is to make me look bad. But, as I am slowly turning into a curmudgeon it won’t be long before I don’t care!

    * Its the culture of "short-cuts." Our students are very lazy as well as short in patience. Fast food, fast relationships, and fast computers are the rage and respect for others and product pride is is "out." I teach at the high school level and they have 10-15 min. maximum patience levels. Food, commercials, attention from mom and dad, are all to blame. It'll get worse before getting better!

    * I couldn't agree with you more. I am currently enrolled at Madisonville Community College in the Advanced Technical Program and I can tell you for a fact that people are being pumped through it as fast as they can while just scratching the surface and not actually "learning" the how an why of much of the science involved.

    * You are right, we need to use our minds more, less computer, especially for the younger generation (of which i am one and plan on being one forever). I agree with too many people taking computing technology for granted and instinctively trusting the output. As it's been said many times, "garbage in: garbage out." But your claim to be "not totally 'down' on young engineers and designers" would seem a complete lie. The mere title of your editorial would claim otherwise, and your ageism, just like any other form of discrimination, is not constructive, nor well received.

Wind Power: A critical look

Stephen_Mraz — Thu, 10 Sep 2009 14:22:22 GMT

The following is from: David Pristash

If you are here on this forum, then you are probably an engineer or technical person like me and are interested in technical issues. Over the past six years or more I have worked exclusively on energy related projects. But I got into energy seriously after CWRU sponsored the National Energy Seminar in June 2005 at Severance Hall here in Cleveland. That was an eye opening event as I came away from it seeing that there was no US Energy Policy despite the fact a panel of "experts" knew then an Energy crisis was coming.

Since then I have devoted as much time as I could to see from a technical point of view what would make the most sense. What I found was confusion on terms, what energy and storage are, where the energy is and how to get clean energy. For example, how can E85 be considered clean when it emits more CO2 then gasoline on a per mile basis? But then the DOE is driven by politics more then science and so its no surprise we get E85 and there is a big push for wind turbines.

What I would like to do is show why "wind turbines" are a bad idea. But before I do that, I'm going to need to set the stage. So the first thing I'm going to do is show how energy should be classified and what it costs to produce.This is an important issue as the US Congress is going to be voting on a bill -- H.R. 2454, the "American Clean Energy and Security Act 2009." But this bill will not achieve any of it primary objectives. Instead, it will seriously reduce economic growth and cost hundreds of thousands of jobs.

The following Table shows the source of energy (in quadrillion watts) on the left and where it was used. What you will not see is that electric power generation is the only a way to take fuel and deliver it to the users in a suitable formr. The upper part of the table shows fuels that are carbon based and which therefore emit CO2 including E85. The bottom half of the table shows fuels or sources which do not emit CO2. Clearly this country runs on carbon, almost 90%.

UNITS of ENERGY

Analysis Based On LLNL and EIA data for 2002 and 2005

	QUADS	Percent	Residential	Commercial	Industrial	Transport
Carbon Based:
Petroleum	40.1	40.4%	1.8	1.2	9.5	27.6
Natural Gas	23.2	23.4%	7.5	4.9	10.8	0.0
Coal	22.0	22.2%	8.1	5.5	8.4	0.0
Biomass	2.7	2.7%	1.1	0.8	0.8	0.0

Total	88.0	88.6%	18.5	12.4	29.5	27.6

Non Carbon:
Nuclear	8.1	8.2%	3.4	2.4	2.3	0.0
Hydro	2.6	2.6%	1.1	0.8	0.7	0.0
Wind Solar Geo	0.5	0.5%	0.2	0.2	0.1	0.0
Electrical	0.1	0.1%	0.1	0	0.0	0.0

Total	11.3	11.4%	4.8	3.4	3.1	0.0

Grand Total	99.3	100.0%	23.3	15.8	32.6	27.6

The next table shows what the Energy Information Agency (EIA) thinks that energy costs. (I did the best I could at getting this information properly classified. And I'm confident that any errors of classification are not material).

COSTS

Analysis Based On LLNL and EIA data for 2002 and 2005

	Billion	Percent	Residential	Commercial	Industrial	Transport
Carbon Based:
Petroleum	$594.7	57.1%	$27.6	$12.3	$89.0	$465.8
Natural Gas	$193.7	18.6%	$80.1	$50.2	$63.4	$0.0
Coal	$159.9	15.4%	$67.4	$58.0	$34.5	$0.0
Biomass	$3.5	0.3%	$0.0	$0.0	$3.5	$0.0

Total	$951.8	91.4%	$175.1	$120.5	$190.4	$465.8

Non Carbon:
Nuclear	$62.8	6.0%	$27.3	$23.5	$12.0	$0.0
Hydro	$19.4	1.9%	$8.4	$7.3	$3.7	$0.0
Wind Solar Geo	$6.9	0.7%	$3.0	$2.6	$1.3	$0.0
Electrical	$0.0	0.0%	$0.0	$0.0	$0.0	$0.0

Total	$89.1	8.6%	$38.7	$33.4	$17.0	$0.0

Grand Total	$1,040.9	100.0%	$213.8	$153.9	$207.4	$465.8

Now since we have the units and the cots of energy in the same format we can determine unit costs and so the next table shows what it costs to produce a Quad of energy (in billions of dollars per Quad).

UNIT COST OF ENERGY

Analysis Based On LLNL and EIA data for 2002 and 2005

	B$/Q		Residential	Commercial	Industrial	Transport
Carbon Based:
Petroleum	$14.8	0.0%	$15.3	$10.3	$9.4	$16.9
Natural Gas	$8.3	0.0%	$10.7	$10.2	$5.9	$0.0
Coal	$7.3	0.0%	$8.3	$10.5	$4.1	$0.0
Biomass	$1.3	0.0%	$0.0	$0.0	$4.4	$0.0

Average	$10.8	0.0%	$9.5	$9.7	$6.5	$16.9

Non Carbon:
Nuclear	$7.8	0.0%	$8.0	$9.8	$5.2	$0.0
Hydro	$7.5	0.0%	$7.6	$9.1	$5.3	$0.0
Wind Solar Geo	$13.8	0.0%	$15.0	$13.0	$13.0	$0.0
Electrical	$0.0	0.0%	$0.0	$0.0	$0.0	$0.0

Average	$7.9	0.0%	$8.1	$9.8	$5.4	$0.0

Overall Average	$10.5	0.0%	$9.2	$9.7	$6.4	$16.9

What stands out is the very high cost of wind, solar PV ,and geothermal. But since the real focus today is "wind" power and that is the majority in that category, we'll assume that that row represents Wind Energy.
The purpose of the House bill called Cap And Trade is to raise the price of carbon energy in the hopes of driving down the costs of wind generated power. That is not likely for a number of reasons, so the net result will be a significant increase in the cost of energy. Remember, 90% of our energy is carbon based.

Over the next few posts that I intend to place here, I will try to show that the move to wind is environmentally risky, will do little to slow the growth of CO2 emissions, and it will do nothing to improve our energy independence.

This is not a discussion on Global Warming it is a discussion on how to produce clean energy.

I'll give a clue as to why wind is risky. In 2050, the US Census bureau predicts there will be almost 420 million people in the US. And since we are planning a major overhaul of the energy sector, we must think in decades and 2050 is therefore not all that far off. So if nothing changes we will need at least another 40 Quad just to handle the extra 100 million people. So assuming we can convert 17.7 Quad of electric power to wind and 9.9 Quad of the personal transportation fleet to an all or partial electric, we will need 27.67 Quad from wind power.

What would that, what would it cost, and what are thee hidden and serious environmental risk associated with it?. I've work it out already and I'll take you though the steps over the next couple of weeks.

setting up forces to properly perform stress analysis

J2201987 — Fri, 17 Apr 2009 15:26:01 GMT

Hello,

I am new her to Machine Design forums. I am a student at an engieering school and I am in a major class, Mechine Design 1. I have a project about stress analysis.

I am performing a stress analysis on a part of an elliptical (exercise) machine, specifically, the center shaft and the side shaft connected to the foot pedal that spins. Sice the machine part is in fatigue, I need help in properly placing my forces and transversing my forces across the part so I can properly calculate stresses. I have pictures of the part. I really appreciate any help I can get. Thank you.

Justin

How do you calculate frictional heat between ball acrew and nut?

shyamreddysunder — Thu, 09 Apr 2009 05:05:58 GMT

Respected sir/madam

We are performing an analysis on ball screw and nut using ANSYS. In this regard, we require calculating frictional heat flux generated (input to the analysis) between the Ball screw and nut. For calculating this we are using the following formula now.

∫ μrωwdx

μ – Coefficient of friction

r – Radius of ball screw

ω – Rotational velocity

w - Distributed load along the nut

Here we know the values of μ, r, and ω, but we are unable to find the formula for finding the distribution load along the nut. So please help us in this regard. Or if you suggest any other method to find the heat flux between ball screw and nut will be helpful for us.

Thanking you sir,

Regards

Shyam Reddy.A

physics of holding a gun sideways

Lee_Teschler — Thu, 29 May 2008 14:31:45 GMT

Here is a question up for discussion for anyone who can answer it. One of my buddies emailed me this exchange about holding a handgun:

Don't ask why, but I've been trying to figure out the origin of the 'gangsta horizontal gun stance'--you know, the one from the movies where they hold the gun sideways. Is there any good reason, ergonomic or otherwise, for holding a gun sideways, except maybe when firing blindly around a corner? The answer is apparently no (and in fact there are plenty of reasons not to in terms of accuracy, etc.).

So why? And which came first, the Hollywood portrayal or actual street usage? Well, here's one theory as to the origin. I'm not sure I believe it, but haven't heard one any more plausible:

"You know why they hold the gun sideways, don't you? A bunch of Hollywood stuntmen and actors got tired of the fact that automatic pistols tend to eject the cartridge back and up. It's not usually a problem when you fire bullets at the range with safety glasses. It is a problem when you're on camera with no eye protection. Add to the mix that blank cartridges are often packed with three times the powder to get that great muzzle flash and bang the audience has grown to expect. So the cartridge is ejected three times hotter and with three times the force. So now all those actors hold the gun sideways because, let's face it, hot brass in the face is unpleasant. Those gangsta wannabes holding the gun sideways learned to shoot by watching movies. They didn't learn to shoot by actually shooting somebody. So be thankful they're showing off their ignorance."

http://blogs.smh.com.au/entertainment/archives/videohead/005613.html

---

I passed this on to a friend of mine who is a licensed gun dealer and gun collector. This is what he wrote:

i do not have a clue about where this originated from. the claim that blanks have 3x the powder is false. there is a blank called a "three in one" because it can be used in rifles (1), pistols (2), and revolvers (3). so i doubt the explanation is valid either. btw: it is called "canting" your gun. bad habit.

Does anybody have something to add about whether the physics of firing a gun in a sideways position tends to promote or degrade accuracy or some other aspect of performance?

Making metallic objects when only a physical part is available

Leslie_Gordon — Wed, 12 Nov 2008 13:58:52 GMT

A reader writes, "I am looking for information on making metallic objects when only a physical part is available. You need a bit of background to answer this though. I am an editor looking for information to pass on to my readers. We are interested in antiques, and some parts are simply not available. I am thinking that stereolithography may be a way to "create" the parts we need--sort of like what they consider to be a prototype. Most, but not all, would be some sort of metal, but probably would need some basic machining to make them usable (tapping, sizing holes for bearings, etc.)

One of the things I want to find out is whether the stereolithography process is advanced enough to make metallic objects, and whether there is a way to generate a computer file from a borrowed physical part when no drawings of any sort exist.

So, which resource would be best to learn the state of the art from?

Halbach Array Motor : Manufacturer or maker information

dwaris — Wed, 09 Jul 2008 22:04:12 GMT

hi All,

I have designed a motor using halbach array (rotary machine, with the halbach array based rotor). At this point, the halbach array is realized using magnet segments which are magnetized in particular directions.

Can anyone please tell me any suitable manufucturer who can support to make such motors? Particularly they can make and assemble the halbach array rotor. Was looking in web, coule not find a suitable manufacturer.

If needed I can provide further information regarding the motor.

Thanks in advance.

~Dwaris

need a motor switch

Lee_Teschler — Fri, 06 Feb 2009 20:21:33 GMT

Kindly let me know which type of switch should I use in the following case. I have a motor which can move in both clock wise and anti clock wise directions. It is used to pull a stand with wheels horizontally from A to B and again send the same from B to A. I want that the change of the motor's direction from clock wise to anti clockwise should be done by the body of the stand as it comes from A to B and from B to A.

With regards

Pramod Kumar

From: Pramod Kumar[SMTP:PRAMODKUMAR023@YAHOO.COM]

How to control DC motor from 2 locations?

tomdoo — Thu, 12 Jun 2008 07:03:20 GMT

Greetings,

I am trying to retrofit an existing piece of industrial machinery to include a 2nd (remote) operator's console. The existing console features a rotary knob type operator interface for speed control (potentiometer wired to DC motor speed controller). This rotary type of input is preferred by the end user. Ideally, the operator will be able to adjust motor speed from either of the two consoles via a simple pointer-less dial (machine run rate is measured and displayed independently of the control circuit).

So, one speed controller, two rotary input devices... I would have thought there would be an off-the-shelf solution to this problem, but hours of searching have produced nothing. Closest thing I've seen are 3-way ceiling fan speed controls, but these would not integrate well with the DC speed controller, nor would they survive the industrial setting.

I suspect the solution is to use a pair of rotary encoders in place of potentiometers? My experience with encoders is limited, but I understand some have a directional output in addition to the usual pulses. This would allow for two pointer-less input devices. The operator could dial the machine speed up from one console and down from the other regardless of where either knob was left. An intermediary device would be required to decode the signals from the two encoders, and convert them to something the motor speed controller can use (4-20mA or 0-5vdc signal).

So, where do I find this mysterious device?

Any ideas?

The current components are:

1/2 HP, 180VDC geared motor

DART Controls 250-series analog controller, with a single potentiometer input for speed control.

Your comments are appreciated!

-Tom

Needing lighting or power source?

cnmaker — Thu, 12 Mar 2009 03:55:16 GMT

if you need lighting or power source, contact me pls.

design and consult

China

Purposes of Food Irradiation

raymond723 — Mon, 09 Mar 2009 04:32:20 GMT

The purpose of food irradiation is to improve the quality of the food being irradiated, either from a microbiological, physical, or organoleptic perspective. Very low doses (< 1 kGy) are used to prevent sprouting in potatoes or delay the ripening of fruits. These doses can also be used to disinfect foods by killing insects in grains and fruits or inactivating parasites (trichinae) in meat. Slightly higher doses (1–5 kGy) can be used to pasteurize foods. Radiation pasteurization, or radurization, significantly reduces or eliminates bacteria of public health significance in the food while also decreasing the total number of bacteria in the food. As with pasteurization by heating, this reduction in the total number of bacteria in a food also results in an increase in the shelf life of the food. Finally, very high doses, on the order of 25 kGy or greater, can be used to sterilize foods. In practice, most of the current interest and research has focused on the low doses commonly used in pasteurization.

One of the main interests in food irradiation is that it can be used as a "cold" pasteurization technique. Many food-borne disease bacteria, including Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes, are very sensitive to irradiation. Although there are some variations in sensitivity among the previously listed bacteria, a dose range of 1.5–3.0 kGy is sufficient to eliminate all these bacteria as they naturally occur in foods.

An advantage of irradiation is that it can penetrate packaging material. Foods can be prepackaged and then irradiated, eliminating the potential for contamination during packaging. In addition, irradiation can be used as a replacement for many food additives that are used to inhibit bacterial growth. Irradiation can also be used as a quarantine treatment for imported fruits and vegetables, which eliminates the need for the use of toxic fumigants.

need a prox sensor

Lee_Teschler — Wed, 28 Jan 2009 21:25:11 GMT

On January 22nd, 2009 Roman Neubauer (not verified) says:

sensor for compound blank & pierce die,I cannot use a light curtain because of the parts reteiver. I need a sensor to install between stripper and punch retainer so no more then 1 part will stay in the die before the sensor will shut press dowm.

Design of tubular fire boxes in steam boilers

comalitalia — Mon, 16 Feb 2009 02:17:22 GMT

Anybody knows how the corrugated fire tubes of steam boilers are manufactured? I am interested in the whole process of the tube design and manufacture...but more specifically the method of corrugating the pipe.

We are talking tube material thickness of 3/8" to 1" thick!

Any input will be appreciated...

Artin Chatmajian

Comal Italia

artin@comalitalia.com

How much flexing in machine frame?

gtoutounji — Sat, 14 Feb 2009 21:58:25 GMT

Hi,

I am new to the forum. I am designing a simple frame from HSS (Hollow Steel Sections) welded structure with load at end of frame (cantilevered). How much deflection do we allow? (torsional, bending).

How do I attach a file with the post?

Thank you,

plastic repairs

Lee_Teschler — Wed, 28 Jan 2009 21:23:16 GMT

On January 25th, 2009 Anonymous art (not verified) says:

I would like information on bonding and repairing pollypropelene and pollyetheline also a pricelist of products I need to acomplish this project

need a flow rate sensor

Lee_Teschler — Wed, 28 Jan 2009 19:18:47 GMT

On January 27th, 2009 Akinsola Olawale (not verified) says:

Am working on a research, which i need flow rate sensor that can measure flow of water in pipeline of about 2km, the diamter of the pipe is 2" and the sensor should have a connectivity wire to a circuit develop by the researcher and it should be able to read in numeric form for the computer to sense the value reads.

motor bearings that fail

Lee_Teschler — Wed, 28 Jan 2009 19:14:52 GMT

:

We have a vertically mounted 15KW motor with fan. The bearing type is deep groove ball at D.E and N.D.E. Both bearings are standard sealed 6309.Could you recommend a better set up, we struggle to get 6 months use before d.e bearing failure.
Regards Damian Cox

Rotary clamps on flat glass disk edging machines

semionb — Sat, 24 Jan 2009 23:43:58 GMT

Hi everyone:
Is anyone familiar with design of machinery used to grind edge on
disks made from glass, ceramics (brittle materials), sapphire, etc.? I
particularly need help with design of the rotary clamp used on
edging machines to hold the disk in place during rotation. If anyone
knows and/or can recommend anyone familiar with the manner and issues
involved in this process, I would appreciate any help. I am
particularly interested in plano/plano blanks, and clamp operates in
vertical orientation. It uses a hydraulic cylinder to clamp, as
opposed to vacuum or air pressure.
Thanks.
Semion

how to do ...

menboren — Fri, 19 Dec 2008 00:30:43 GMT

I wish to do design how to do that

How to do?

menboren — Wed, 17 Dec 2008 03:18:27 GMT

How to do for auto machine design?

Designing stuff that's fun and not going to ruin the world...

kyledonovan — Sat, 13 Dec 2008 23:30:03 GMT

Hi everyone, I just joined and would like to introduce myself. I'm an upcoming student at Bristol-Plymouth High School in the Drafting course. I've already completed Mechanical Drafting and have started Architectual. I'm interested in learning all I can about Mechanical. I would like to hook up with other Mech drafters out there, so if your available to chat, please send an email or post on this site. Kyletron2281@yahoo.com

Thanks!

Kyle Donovan

Design Royalties

jhale32526 — Thu, 04 Dec 2008 15:37:08 GMT

I have designed and built a automated machine that replaces an otherwise manual assembly process.

I can put an actual dollar amount on the cost savings.

This was outside of my job description.

The company I work for paid all expenses.

How do I go about getting something for efforts?

Roll Over Valve for Aerospace (Fuel System)Appliction

Sohan_Vinchurkar — Thu, 04 Dec 2008 04:55:16 GMT

Looking for complete detailed information Roll over Valve also design of it

Design query

plani25 — Wed, 03 Dec 2008 12:41:47 GMT

Hallo,

I am having a query in regarding with the design of a housing ...There is a rotating shaft from a motor, and the motor setup is completely enclosed in a cylinder (Which is also rotating in opposite direction). That means, I got 2 roating components mounted in the same plane, I need to provide the suitable beaings

Shaft Diameter : 25 mm, Cylinder Inner Diameter : 76 mm

I am thinking of proving 2 bearings(But I could nt find any standard baerings) with a bush inbetween (Stationary one)....

Please help me out, if anyone has good solution for this...

JCIS versus Torx Plus Screw Design

rjpark — Tue, 25 Nov 2008 22:50:30 GMT

Which is better for high volume manufacturing?