Author Topic: NACA 66 Special A/BGS  (Read 596458 times)

0 Members and 1 Guest are viewing this topic.

Offline JimL

  • Sr. Member
  • ****
  • Posts: 799
Re: NACA 66 Special A/BGS
« Reply #510 on: January 23, 2013, 04:54:06 PM »
You can get some off-the-shelf software for your laptop, and an accelerometer.  You are looking for FFT spectrum analyzer that include a raster display function.  The raster function will let you see clear ringing frequencies and harmonics, after the initial "all frequency saturation" of the strike.

The quality of the result is more dependant on the accelerometer and signal conditioner, which can be the most expensive part.  You must mechanically clamp to the wheel, and test set points for comparison to your baseline displays.  Use the printout function to save the baselines.  Choose 0 dbG = .001 G so you can compare logarithmic values of the amplitude.  This will let you keep more "on the screen range" during ring decay.

Running in raster mode, you'll quickly learn to see the true ringing characteristics of each wheel.  By keeping an ongoing record of the test points data, you will develop a log that could certainly show when a significant anamoly has been spotted.

The trick is to learn to freeze the raster during the strongest ringing, and then take top line to 2d for frequency and harmonics viewing.  If it cracks, there will be a whole new set of harmonics that were not there before.  The sample instance is NOT extremely time critical during raster view.  Decay rate is only for amplitude, not frequencies.  If you know a Diagnostic Master Technician at a local Toyota dealer, they were
all trained to use the basic FFT Spectrum Analyzer that came with their original diagnostic test equipment.  Some of the dealers will still have operating equipment, even after 20 years.  I know that some technicians have purchased laptop based analyzers for their own use.

Interesting idea, I think.  Note that salt accululation on the wheel will not change the frequency of aluminum ringing, only the amplitude.  That should not prevent a tracking and diagnosis record.
JimL
« Last Edit: January 23, 2013, 05:01:16 PM by JimL »

Offline Kiwi Paul

  • Sr. Member
  • ****
  • Posts: 494
Re: NACA 66 Special A/BGS
« Reply #511 on: January 23, 2013, 11:54:29 PM »
Careful, Jim--Sounds as though you have volunteered yourself for a part time job!! :-D

Offline Jack Gifford

  • Hero Member
  • *****
  • Posts: 1568
Re: NACA 66 Special A/BGS
« Reply #512 on: January 24, 2013, 12:03:35 AM »
I'll bite- why did Toyota dealers need spectrum analyzers? :?
M/T Pontiac hemi guru
F/BFL 1-mile Loring record 2020

Offline JimL

  • Sr. Member
  • ****
  • Posts: 799
Re: NACA 66 Special A/BGS
« Reply #513 on: January 24, 2013, 12:40:54 AM »
Because its cheaper to fix a bad CV joint than to replace 5 complete sets of wheels and tires, on the same car, that was already bought back for the same complaint!  True story....they flew me and my FFT to another area to find out why the dealer couldnt fix the car. 

As the cars got quieter and smoother, all the little things that used to be masked or ignored became the big complaint problems.  No one had ever bothered to train techs how to figure out what component was the root cause of a problem condition.  I was the supervisor on the development of the new (for 1994 model year) OBD II scantool.  I had done a lot of work in the field, using spectrum analysis to find conditions ranging from radiator hose routing/shape issues to heater fan cyclic drone.   (That turned out to be a cost saving manufacturing process where it was cheaper to produce the squirrel cage with a nice geometrically even number of blades, and of course the motor armature has to have an even number of segments for the two brushes.  Unfortunately, the customers and many techs were convinced they were hearing a bad right front wheel bearing.  You can put a lot of wheel bearings in a car, trying to fix the heater fan noise.)

Anyway, there was an opportunity to put better equipment, and better training, in the technicians toolbox.  Those were exciting years for the techs, with OBD II datastreams to read and analyze, the FFT function, and a full breakout box kit that could look at cruise control, automatic a/c, and more.  It even had an oscilloscope which could select from many different signals or be used with an autoprobe.
 
We put a lot of emphasis on understanding what is supposed to vibrate, and where the transmission path of vibration should not be.  Radiator hoses, heater hoses, wire harness bundles, etc are really common mistakes made by enginners and home builders, for example.  I can get real boring, so I will stop now.

Rob, PM me if you want to talk.  I am still not certain this will be very clear in aluminum.  Large blocks of aluminum often have thermoclines during the pour, which might affect your test results.  Keep in mind, I dont claim to be an engineer...I just got stuck into the job because somebody had to do it and I think I looked expendable.

Regards, JimL

Offline Kevin G

  • Jr. Member
  • **
  • Posts: 38
Re: NACA 66 Special A/BGS
« Reply #514 on: January 24, 2013, 02:30:24 AM »
I may be over simplifying things a bit, but could you just do the old "wipe them down with dye, wipe the dye off, and take a good hard look at them to see if the dye stuck in any cracks" trick?
68 in a 55. Michigan State Police. 98
65 in a 55. Wayne County Sheriff. 02
Loud exhaust. Memphis City Police 03

Offline DND

  • Sr. Member
  • ****
  • Posts: 395
Re: NACA 66 Special A/BGS
« Reply #515 on: January 24, 2013, 02:45:14 AM »
Hi Rob

In 68' i worked in a engine shop building Can - Am engines, John Cannon was running low on bucks so after each race he would go to our cracked crank's dept.

John would pick up each crank and ring it with a hammer and put in the best sounding of the bunch, well that year it rained at Laguna Seca and he won that race with a cracked crank and never broke one.

Just another cool racing story that makes this stuff so great, you could write a few books on all the neat storys like this one.

Don

Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: NACA 66 Special A/BGS
« Reply #516 on: January 24, 2013, 07:54:07 AM »
JimL  GM was having the same kind of problems---on of the reason GM (corrections) used SVC (speed volume control) was to make sure the radio volume went up with speed  because folks were hearing a lot more wind noise than they were use to.  On Astro vans also primary reason for the fiberglass rear springs be cause it was UNIBODY!
« Last Edit: January 24, 2013, 01:37:40 PM by SPARKY »
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline manta22

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: NACA 66 Special A/BGS
« Reply #517 on: January 24, 2013, 11:12:09 AM »
Sparty;

IIRC, the first car radio volume/speed control appeared on a Ford Thunderbird in about 1956 (?).

If you have your aluminum billet x-rayed you might find which ones look the cleanest internally before you invest in machining.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Rex Schimmer

  • Hero Member
  • *****
  • Posts: 2626
  • Only time and money prevent completion!
Re: NACA 66 Special A/BGS
« Reply #518 on: January 24, 2013, 01:06:03 PM »
Having your alum stock x-rayed is a great idea, the stuff coming from Korea and China is notorious for internal lapse and voids. It needs to be perfectly clear, better yet make sure it comes from a US mill.

I must be Neil's "yes man" second post that I followed him on to say that I agree with him!!

Rex
Rex

Not much matters and the rest doesn't matter at all.

Offline Dean Los Angeles

  • Hero Member
  • *****
  • Posts: 2370
Re: NACA 66 Special A/BGS
« Reply #519 on: January 24, 2013, 02:43:21 PM »
Quote
If you have your aluminum billet x-rayed you might find which ones look the cleanest internally before you invest in machining.

I think the better plan is to request ASTM grade A certified material from your metal supplier.

Gas porosity, shrinkage porosity, inclusions, and cracks are graded A-D. Grade D castings lose 30-40% in strength. The reference radiographs in ASTM E155 are the standard against which these grades are judged. Grade A material is sold at a premium.

You still need to have the finished part x-rayed, ultrasonic tested, and dye penetrant tested. Having those records will make the tech inspector happy.

Inspecting between runs can only be a visual test. The time it takes to do any other test rules them out. Between events a Zyglo test should do.
Well, it used to be Los Angeles . . . 50 miles north of Fresno now.
Just remember . . . It isn't life or death.
It's bigger than life or death! It's RACING.

Offline Jack Gifford

  • Hero Member
  • *****
  • Posts: 1568
Re: NACA 66 Special A/BGS
« Reply #520 on: January 25, 2013, 02:17:26 AM »
JimL- not boring at all. Quite interesting.
M/T Pontiac hemi guru
F/BFL 1-mile Loring record 2020

Offline robfrey

  • Hero Member
  • *****
  • Posts: 1206
    • carbinitelsr
Re: NACA 66 Special A/BGS
« Reply #521 on: January 25, 2013, 10:55:01 AM »
JimL- not boring at all. Quite interesting.
I agree!
496 BGS
carbinitelsr.com
carbiniteracing.com
carbinite.com

Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: NACA 66 Special A/BGS
« Reply #522 on: January 25, 2013, 11:02:46 AM »
JimL  it is amazing all of the technology a good tech or salesperson is exposed to in the various parts of the transportation industry---thanks for sharing :cheers:
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline robfrey

  • Hero Member
  • *****
  • Posts: 1206
    • carbinitelsr
Re: NACA 66 Special A/BGS
« Reply #523 on: January 25, 2013, 11:26:20 AM »
Still not running yet but it's very very close.
Some of you may have already seen some of these pics but for those who have not been following the project that closely, I will try to explain how we have built the body parts.


First step was for me to section the solid works model  into 12" segment and 6" segments where more detail was required. Then I could release dxf formatted drawings to the water jet guy.with instruction to cut them from 5mm plywood that I supplied him from Lowes. I then shipped them to Eric.
Note that there is 1.5" square locating feature that keeps proper alignment of the segments.


Eric then painted all outside edges of the plywood black so that it would contrast with the 2 part foam during the sanding operations.


They were then laid out on large sheet of plywood which had a 2x2 (1.5) secured to it. Eric could then layout and cut the bases (right and left).




Segments are then secured to base.
496 BGS
carbinitelsr.com
carbiniteracing.com
carbinite.com

Offline robfrey

  • Hero Member
  • *****
  • Posts: 1206
    • carbinitelsr
Re: NACA 66 Special A/BGS
« Reply #524 on: January 25, 2013, 12:04:36 PM »

Cardboard was then fitted between the segments to minimize foam consumption.


Foam added between segments.




Then foam is the sanded to shape of body using segment edges as guide.




Conventional body working methods are  used to smooth and final shape the mold.
496 BGS
carbinitelsr.com
carbiniteracing.com
carbinite.com