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PostPosted: Wed Jun 04, 2014 8:33 pm 
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A buddy and I have been working lonnnnggggg and hard on restoring a collision damaged, rusted out, and improperly repaired 1965 coupe at my body shop. We started work with it on a rotisserie and then transferred it to a mini-"celette" that we had fabricated. It includes fixtures that look like those in the shop manual that attach to the torsion bar tubes, and an "outrigger" that attaches to the door post hinge mounts. This was needed because we had to remove all of the front end and wanted to make sure to get all the replacement parts on correctly, and then for the car to roll straight and level. We never expected to use a laser level to do car repair/ body work, but it has been invaluable. Also, this site has been invaluable. We logged many, many hours here 2-3 years ago. Not so much the past year, but now we are back.

Our current headache (opportunity) is with the fit up of the rear quarters in the area of the rear bumper. There are some chassis dimensions that are giving us trouble. First, the book shows a 12mm dim from the top-of-frame up to the threaded holes in the frame (2 each side) that the bumper brackets bolt to. On our car, these holes are perhaps 1mm below the top-of-the frame. Both sides match pretty closely. We have scraped off the undercoating and looked carefully for collision damage in this area and can't find any. All the chassis metal is straight and smooth. What's going on here?

Next, what does the 42mm dim go to? It looks like it is from the top-of-the frame up to the rearmost, top corner of the frame. If so, ours isn't. It is around 20mm low. Again, no collision evidence back here.

And, what is the 7mm dim to? It appears to be from the top-of-frame up to some point on the bumper braces that are welded to the side of the frame. It kind of looks like it goes to the top of the horizontal portion of the brace, or does it go to the hole in the little "L" bracket that bolts onto the brace, or something else?

This all became a question because the rear body panels are not fitting the welded-on bumper braces very well and not fitting up with the bumper very well. (New bumper.) The larger holes on both sides of the body, where the ends of the bumper bolt to the welded-on brace, are sitting so high that they interfere with the bolts that should pass through them. And, the C-shaped indentations surrounding these holes do not line up well with the ends of the bumper.

Does it appear that the rear end of our frame is at the right height or not? Looking for clarification with dimensions, drawings, and/or pictures.

Thanks,
Jeff


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PostPosted: Thu Jun 05, 2014 4:43 pm 
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Jeff,

As far as the 12mm dimension goes, it may be tied to how you set up your top of frame datum line. In particular the 42mm dimension is given to allow you to set a line from the top of the torsion bar cover plate bolt boss (top right one) to the end of the chassis. If this not set exactly you may be off by the 1mm in question. How did you shoot this line without the 42 mm dimension ? If you used the 140mm dimension (floor datum to C-L of the bottom right T-bar cover bolt) and the 147mm to the frame top datum, could this be off some ?

The 7mm dimension appears to be from datum line to the top of the fender bracket (attachment surface to fender).

Do I understand that you have removed the rear clip or some part thereof and are now replacing it with a new one ? How did it line up before the disassembly ?

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PostPosted: Mon Jun 09, 2014 12:29 pm 
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Thanks for the help Larry. So, is the top of the torsion bar cover plate bolt boss tangent to the top-of-frame datum? I never noticed that - I guess because of how small the drawing details are. Anyway, you asked about how we set up our top-of-frame datum line. First, we leveled our "celette" jig. The fixtures on the jig have large measuring pins (per the book) that are slip fits into each end of all three torsion tubes. With the jig level, the center of the rear torsion tube is to be 24.5mm higher than the center of the bottom front torsion tube. (This number comes from the 77mm from center of the rear torsion tube to the top-of-frame datum, 147mm from there to the C-L of the bottom right T-bar cover lug, the 140mm from there to the tram gauge illustration, and 185.5mm from there to the center of the front bottom torsion tube.) We used a laser level to "strike" our lines. (We double checked using a liquid level.) We then mounted the car on the jig. We then used the laser level to establish the top-of-frame datum on the car, 77mm up from the center of the rear torsion tube, established by the center of the measuring pin. We could not use any of the T-bar cover lugs because they were obscured by the jig fixtures. By the way, when setting the laser line 77mm up from the torsion tube, it does fall along the top surface of the frame in the door opening.

We didn't replace the rear clip. In the rear we replace on quarter, from the door lock post back to the "C" impression around the hole the end of the bumper bolts through. We also replaced the bumper and one of the welded-on bumper braces. The portion of the chassis from the center of the rear wheels back, looks in good shape, with regard to no prior collision damage. But, the height dimensions relating to the bumper mounting that I was asking about, don't line up with the illustrations.


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PostPosted: Mon Jun 09, 2014 4:56 pm 
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Jeff

I am envious of your Cellete bench ! I've had to depend on careful measurements and my engineering background to finesse a lot.
The top t-bar cover bolt boss is within a mm of the datum, hence I use it to pull a string to the end of the chassis (at the 42mm dimension) for setting my datum line when setting torsion bars and trailing arm angles.

As to why the 42mm dimension measures 22mm short is a perplexing question ! You would have to be about 7/16” (slightly less than 1°) off at the rear torsion bar tube to get that much off at the chassis end Since most levels are hard pressed to measure 1°, I would consider re-checking your setup distances from the Celette base surface.

Post your results of this problem, I will be most interested !

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PostPosted: Mon Jun 09, 2014 11:34 pm 
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Larry,
Before you get too envious, let me be perfectly clear, I use quotation marks when referring to my "Cellete" because it is not a real Cellete. My buddy and I are mechanical design engineers working in my auto body shop part time. We designed the bench that we call a jig and had it made by a fab shop. The fixtures were made by a machinist. We took great pains to true everything up before mounting the car on it. That being said, we are very pleased with how it turned out. And, it is robust enough to pull and push against to do some straightening, but we mostly just use it to hold everything in the right locations. If we ever get done with this car we will probably sell the jig.

We will now recheck these setup dimensions. By the way, we are in Burlington, NC. Thanks for the help.


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PostPosted: Tue Jun 10, 2014 12:51 am 
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Pictures would be great! Not hard to post ... =8^)

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PostPosted: Tue Jun 10, 2014 1:15 am 
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Jeff,

Well I'm still envious as I wish I had had the space and time to have made such jig. The closest I have come to date is to make some drawings of the interface fixtures for a friend who had a chassis table.
Do you have a fixture for trans hoop mounting bosses ? Or alternatively checked the 109.75mm dimension ? If this dimension is short by 11.75mm (15/32”) then you are most likely not level.

With luck I'll get the opportunity to admire your creation in person but pictures would be nice till then.

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PostPosted: Wed Jun 11, 2014 10:22 pm 
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Last night we checked the dimension to the trans hoop mounting points. They are within a mm of being dead on. BTW, that dimension is very obscure in the book. It also might be worth mentioning that when we strike a line with the laser level at the top-of-frame datum, it lines up with the top of the frame in the door openings. We are now very confident the the chassis is level. We still have the nagging rear end problems though. The two threaded holes on each side where the bumper brackets bolt onto are level, and line up with the top-of-frame datum give or take 1mm. They should be 12mm above the datum according to our book. The 42mm dim is also out, and we don't even know what the 7mm dim goes to. When the bumper is attached, to the bolt-on brackets, the ends of the bumper do not line up with the thru holes in the quarter panels to attach to the welded-on braces. What we are looking for now is for someone to tell us that the 1965 356C coupe must have the threaded bolt holes for the brackets 12mm above the top-of-frame datum or not.
When we can we will post pics.

Thanks,
Jeff


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PostPosted: Thu Jun 12, 2014 2:01 am 
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As I suggested in my previous post the 7mm dimension is between the datum line and the top of the bumper brace. Further you do realize that there is an angle bracket that fits between the fender brace and the fender/bumper, see sec. 6/1 of the parts book. Also the fender has an extra-large hole to allow a lot of adjustment between the three pieces being bolted together, fender, bumper & brace.
Since no running gear attaches to the frame way out there at the bumper bracket attachment holes, it would seem short of tweaking the chassis aft of the trans hoop mounts to suit the drawing dimensions, a compromise might be found to accommodate the bumper/fender/fender brace ? You did say the car had been improperly rust repaired with collision damage, although not in the immediate area in question. Note also that no tolerances are given for the 12, 42 and 7mm dimensions which implies that they are not critical !

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PostPosted: Thu Jun 12, 2014 4:24 pm 
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Larry, now that you sound more confident about the 7mm dimension I will have to take your word for it. :-) I was hoping that the 7mm went to the hole in the angle bracket that you were referring to, because that's what it is on mine! And, this is why the hole in the angle bracket does not line up with the extra-large hole in the fender. Only half of the hole in the angle bracket can be seen through the hole in the fender. So, I think we will study on tweaking the aft end of the chassis. Thanks for your help. I'll let you know what comes of it.
Jeff


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PostPosted: Thu Jun 12, 2014 5:12 pm 
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Just for interest, do your angle brackets (#48 on pg 6/1 of parts book) not have slotted holes ? This along with the extra large hole in the fender usually allow enough adjustment to get the bolt through everything. If not you do have your work cut out for you !

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PostPosted: Thu Jun 12, 2014 8:01 pm 
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Hey, maybe you are on to something. These angle brackets have a slot on one leg and just a simple bolt clearance hole on the other leg. The slot side is bolted to the brace and the holed side goes toward the fender. Is this correct? Thanks.


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PostPosted: Thu Jun 12, 2014 10:47 pm 
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Actually mine are slotted on both legs of the angle bracket. Which is as they are supposed to be from what I've seen in tghe past and per the illustration in the parts book (6/1)


Attachments:
B-C bumper.jpg
B-C bumper.jpg [ 137.07 KiB | Viewed 3139 times ]

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PostPosted: Sat Jun 14, 2014 7:15 am 
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Maybe you have window-track bottom brackets (from inside the doors) by accident which have only one leg slotted.

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PostPosted: Sat Jun 14, 2014 1:20 pm 
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Jeff,

Did you take this car apart ? Or has it been just a long time since you did ? Do you have a parts manual ?
How well do the main bumper mounting brackets fit through the square body holes and mate up with the bolt holes on the chassis ?

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