NECEES Mechanical PE Reference Manual Released

[OldSquaw 2]

Also just in case anyone was curious, I have been studying for the exam using the online "learning hub" through PPI. It's an online database of practice problems, quizzes, and books. I have also found several errors in these practice problems. Most of the errors are in the solutions to the problems. I haven't been using this resource very long either. It is extremely frustrating to study for the exam using a reference manual and practice problems that are both filled with errors. I'm really starting to think this whole new format is a complete joke.

[jean15paul_PE 302]

18 hours ago, OldSquaw said:

Also just in case anyone was curious, I have been studying for the exam using the online "learning hub" through PPI. It's an online database of practice problems, quizzes, and books. I have also found several errors in these practice problems. Most of the errors are in the solutions to the problems. I haven't been using this resource very long either. It is extremely frustrating to study for the exam using a reference manual and practice problems that are both filled with errors. I'm really starting to think this whole new format is a complete joke.

To be fair, there are lots of errors in the MERM and in the old NCEES practice exam. ... and in every other thing every published. But they have been around a long time so (1) many errors have been corrected during multiple revisions, and (2) erratas are readily available. Eventually these newer resources will catch up. But I feel what you're saying, it kinda sucks to be the gen1 guinea pig.

[Audi driver, P.E. 1,088]

21 hours ago, OldSquaw said:

Also just in case anyone was curious, I have been studying for the exam using the online "learning hub" through PPI. It's an online database of practice problems, quizzes, and books. I have also found several errors in these practice problems. Most of the errors are in the solutions to the problems. I haven't been using this resource very long either. It is extremely frustrating to study for the exam using a reference manual and practice problems that are both filled with errors. I'm really starting to think this whole new format is a complete joke.

Look at it this way. If you're able to discern why the problem solution is wrong, you're probably going to do OK on the exam.

[Dr. Barber 34]

The unit conversion table in page 2 erroneously has the viscosity unit "reyn" as equal to 1 lb-ft/s^2 where it should be 1 lbf-ft/s^2. 

[Dr. Barber 34]

Ok, I welcome any clarification and pointing out what I'm doing wrong here. If I'm not making any dumb mistakes, then this is further proof that this handbook is an unmitigated disaster.

Consider this simple question: What is the dynamic viscosity of SAE 50 oil at 50C?

If we use the graph in page 10, we get... what do we get? I have no idea. is this 4.5? 45? 450?

Note there is a 10^2 below the horizontal red line and another 10^2 above the red line. At first I thought the 10^2 below was a typo and should be just 10, but there is already a 10 further below. So, ¯\_(ツ)_/¯

 

 

Then I thought I could use the imperial units graph of page 9. Going in there at 122F (50C) I get 16 reyn, which is 1.1x10^8 mPa*s which is nowhere near anything close you could get from the SI chart.  So, yeah, unless I'm doing something really wrong, this is REALLY screwed up.

[jean15paul_PE 302]

On 11/27/2019 at 6:59 PM, Dr. Barber said:

The unit conversion table in page 2 erroneously has the viscosity unit "reyn" as equal to 1 lb-ft/s^2 where it should be 1 lbf-ft/s^2. 

Well. I'm old school solid mechanics guy....
lb ALWAYS means lbf. lbm is a unit for mass that I personally hate and never use because gc is evil. 
SLUGS 4 LIFE!!!!

But I know that's not how yall thermal-fluids engineers think.

[Dr. Barber 34]

5 hours ago, jean15paul_PE said:

Well. I'm old school solid mechanics guy....
lb ALWAYS means lbf. lbm is a unit for mass that I personally hate and never use because gc is evil. 
SLUGS 4 LIFE!!!!

But I know that's not how yall thermal-fluids engineers think.

 

 That's the kicker with this manual. They use lb, lbf and lbm. Sometimes by "lb" they mean "lbm" and sometimes they mean "lbf". I mean, this thing is just a real hoot.

 

 

[Audi driver, P.E. 1,088]

On 11/27/2019 at 6:04 PM, Dr. Barber said:

Ok, I welcome any clarification and pointing out what I'm doing wrong here. If I'm not making any dumb mistakes, then this is further proof that this handbook is an unmitigated disaster.

Consider this simple question: What is the dynamic viscosity of SAE 50 oil at 50C?

If we use the graph in page 10, we get... what do we get? I have no idea. is this 4.5? 45? 450?

Note there is a 10^2 below the horizontal red line and another 10^2 above the red line. At first I thought the 10^2 below was a typo and should be just 10, but there is already a 10 further below. So, ¯\_(ツ)_/¯

 

 

Then I thought I could use the imperial units graph of page 9. Going in there at 122F (50C) I get 16 reyn, which is 1.1x10^8 mPa*s which is nowhere near anything close you could get from the SI chart.  So, yeah, unless I'm doing something really wrong, this is REALLY screwed up.

What a Charlie Foxtrot.  First of all, at 50C, SAE 50 Oil would be about 97 mPa-s, which is 14.1E-6 Reyn. So the first chart would (apparently???) indicate a value of 45 (to be in the correct ballpark for factors of 10), but that corresponds to the actual value for SAE 30 oil (from other references I have). If you look at the Imperial units graph, you will note that it properly has a mu symbol (indicated on the Y axis label) but for some reason there is a comma between that and reyn. That chart is closer to correct, value-wise, for micro reyn. If you use a value of 16 micro reyn, you get about 110 mPa-s, which is closer to the actual value. I don't know how to read that first chart. On your exam, I would use the second chart, convert, and call it a day.

Edited yesterday at 01:43 AM by Audi driver, P.E.

[OldSquaw 2]

Here's another issue I found:

[Dr. Barber 34]

15 hours ago, Audi driver, P.E. said:

What a Charlie Foxtrot.  First of all, at 50C, SAE 50 Oil would be about 97 mPa-s, which is 14.1E-6 Reyn. So the first chart would (apparently???) indicate a value of 45 (to be in the correct ballpark for factors of 10), but that corresponds to the actual value for SAE 30 oil (from other references I have). If you look at the Imperial units graph, you will note that it properly has a mu symbol (indicated on the Y axis label) but for some reason there is a comma between that and reyn. That chart is closer to correct, value-wise, for micro reyn. If you use a value of 16 micro reyn, you get about 110 mPa-s, which is closer to the actual value. I don't know how to read that first chart. On your exam, I would use the second chart, convert, and call it a day.

Thanks. I hadn't noticed the "mu" -- good catch. Yeah, what a sh*t show. That first chart is useless. In their defense, they do provide a reference to where the chart came from. Maybe it's messed up in the original source and they just copied it.  It shows, however, that nobody who is participating in the creation of this manual has used the dang chart. 

[Dr. Barber 34]

12 hours ago, OldSquaw said:

Here's another issue I found:

LOL

JFC

 

 

[OldSquaw 2]

Dr. Barber,

Are you reporting all of this to NCEES? I haven't reported anything in hopes that you were, lol! If you're already doing this then I won't bother.

I'm one of the poor people that is taking the exam in April with this reference.

[Dr. Barber 34]

Yes.

I have reported most of the things in this thread to them. Not this latest set of findings, but I will get around to it probably this weekend.

 

Edited 11 hours ago by Dr. Barber

[OldSquaw 2]

Awesome! Thanks!