Author Topic: CBC (Chassis Broadcast Copy) Prop. Shaft information  (Read 3143 times)

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
CBC (Chassis Broadcast Copy) Prop. Shaft information
« on: June 10, 2021, 02:58:06 PM »
OK need some help here in regards to possibly refining the CRG Driveshaft Report.  As with anything, we are always looking for new data and we update reports as we get new solid confirmed information.

Some recent information has surfaced that is suggesting there is yet another driveshaft that needs to be documented for 1967 and another for 1969.

If you have a Chassis Broadcast Copy (CBC) for 67,68 or 69 Camaro we would appreciate your help. These are quite rare, but they do surface sometimes. Would be interested in a clear photo of the whole sheet, or if you want to just include the 2 letter code and the propeller shaft (driveshaft) box, that is fine too.  For 69s it is box 230. 

Thanks in advance.

You can post here or email me direct.
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #1 on: June 10, 2021, 03:08:21 PM »
Any CBCs with a six cylinder engine in 67, COPO or L78 in 69 would be the most helpful but we will take any information you can provide.
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

asm69

  • Member
  • ***
  • Posts: 196
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #2 on: June 12, 2021, 08:18:35 PM »
Hi,

I have 1969 Camaro z28 October 1968 Van Nuys build. I have the Chassis Broadcast Copy sheet.
Box 230 has the letters "WN".  I have attached an image.



bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #3 on: June 13, 2021, 08:49:17 AM »
Got it. Thank you!
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

firstgenaddict

  • Hero Member
  • *****
  • Posts: 2867
  • caretaker of 1971 LT1's 11130 & 21783
    • View Profile
    • Groome Family Automobiles
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #4 on: June 16, 2021, 08:11:14 AM »
The first ZL1 with auto is GL - sheet is known.
James
Collectin' Camaro's since "Only Rednecks drove them"
Current caretaker of 1971 LT1's - 11130 and 21783 Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
https://plus.google.com/photos/112392262205377424364/albums?banner=pwa

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #5 on: June 16, 2021, 04:53:18 PM »
Correct.  But we do not have COPO with manual transmission verified.

« Last Edit: June 17, 2021, 12:28:09 AM by bcmiller »
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #6 on: June 22, 2021, 04:05:53 PM »
Was able to get a sheet recently that confirms for 1969 that an L35 with M20 does use the same driveshaft as a Z28, other small blocks and L6. 

http://www.camaros.org/driveshaft.shtml

There is some question though whether other big blocks with manual transmission received the same driveshaft. Evidence is leaning toward something different.

Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

KurtS

  • CRG Coordinator
  • *****
  • Posts: 5659
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #7 on: June 22, 2021, 06:15:02 PM »
I know of 5 BB Muncie cars that all have the same WN driveshaft (L6, SB, BB with powerglide or manual).
1 BB Muncie with a different driveshaft - why is unknown.
Kurt S
CRG

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #8 on: June 22, 2021, 07:46:32 PM »
I have 3 examples indicating a different driveshaft was used for a 427 with a Muncie.

Thus the reason for the thread.
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

rich69rs

  • Hero Member
  • *****
  • Posts: 1070
  • LF7/M35/Z22/Z87
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #9 on: June 23, 2021, 02:40:05 AM »
http://www.camaros.org/driveshaft.shtml

I would like to have a serious discussion as to why GM/Chevy offset the yokes 32 degrees on some applications and not others.  From a pure engineering perspective this makes absolutely no sense.

No engineering/technical reference will state that this is how you design a double cardan propeller/driveshaft.

For a double cardan driveshaft to function with minimal vibration, the yokes have to be in phase in order to maintain the same operating angle at both ends.  In phase yokes will also accommodate a certain degree of side to side mis-alignment.

At a minimum, offsetting the yokes will stiffen and introduce both a 2X and torsional vibration into the driveline.  Any significant side to side mis-alignment would aggravate the issue.  (Retired now, but during my 45+ years of experience as a registered professional mechanical engineer, root cause analysis of vibration in rotating machinery was an area of my expertise.)

Did the SCCA Trans-Am series have anything to do with it?

Richard

« Last Edit: June 23, 2021, 04:14:10 AM by rich69rs »
Richard Thomas
1969 RS

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #10 on: June 23, 2021, 10:21:49 AM »
This thread is not the place for a discussion like you want. Obviously I didnít do the designs - but apparently the engineers back in the day knew what they were doing. So does it REALLY matter WHY?

Some of the big block driveshafts have inline yokes/trunnions because of how the engine is slightly offset toward the passenger side.
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

rich69rs

  • Hero Member
  • *****
  • Posts: 1070
  • LF7/M35/Z22/Z87
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #11 on: June 23, 2021, 04:09:45 PM »
....... - but apparently the engineers back in the day knew what they were doing. So does it REALLY matter WHY?

I'm going to make the following comments, and then I'll move on....

Yes it matters, at least to me....from both an engineering as well as a historical perspective.  For the sake of completeness of the CRG report, I would hope that it matters as well - if nothing more than to add a footnote in the report noting that 32 deg out of phasing of the yokes is well outside of normative engineering practice and at this time the reason(s) are not known.

I have been pondering why this happened for almost 30 years; since July 1992 when I had the driveshaft in my '69RS corrected to in phase yokes.  I would simply ask that you take 2-1/2 minutes to watch the following video from Spicer:
      https://www.youtube.com/watch?app=desktop&v=Idk3BVDVHq4

The demonstrator they use in the video, both visually as well as audibly, shows the effect of:
                         1) not maintaining the same operating output angle between driveshaft ends (first two minutes) and 
                         2) what happens when you change the yokes from in phase to out of phase.

I don't doubt that the engineers knew what they were doing.......one possibility is that they had discovered a high rpm driveshaft resonance problem.  An inexpensive fix for a driveshaft resonance issue could have been to offset the yokes which would effectively stiffen the driveshaft and shift a resonance frequency(ies). 

They could have accomplished the same thing by changing the diameter/thickness of the driveshaft tube material, but that would probably be a more expensive route to take. 

Of course the downside of knowingly offsetting the yokes would be that they were fully aware that they would be introducing a 2X vibration into the driveshaft along with both inertial and torsional forces and resulting vibration(s).  One could argue that as long as the driveline lasted the length of a race or for 5 years for the general public.....   

Richard

 
 
Richard Thomas
1969 RS

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #12 on: June 23, 2021, 05:36:23 PM »
Richard I appreciate your insight.

The only way you are going to get an answer is build a time machine, go back to the 60s and ask the design engineers. Itís in the design drawings that way.
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

Hans L

  • Member
  • ***
  • Posts: 364
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #13 on: July 02, 2021, 04:43:43 AM »
CBC from my 04B VN Built '69 Camaro Z/28 - pretty deteriorated at the edge unfortunately.   Best guess - WN...

https://www.instagram.com/69camarorsz28/
'69 Camaro RS Z/28 Van Nuys Built
'69 Chevelle SS 396 4 Speed

bcmiller

  • CRG Member
  • *****
  • Posts: 3497
    • View Profile
Re: CBC (Chassis Broadcast Copy) Prop. Shaft information
« Reply #14 on: July 02, 2021, 12:36:45 PM »
CBC from my 04B VN Built '69 Camaro Z/28 - pretty deteriorated at the edge unfortunately.   Best guess - WN...



Thank you. Yes WN seems correct.
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016