Frame measurements

[orange383]

I'm going to be replacing the rear frame rails soon on my 68 charger.
The car is sat on a jig with 6" uprights at the 4 gauge hole points. The top of the jig is now my datum line as per the drawing for the 1969 - 1970 Dodge Coronet that includes the charger and super bee.

I read somewhere that these dimensions were taken with the suspension/axle in place and on all 4 wheels so the frame rails were under load. Is this correct? If so does anyone know the measurement from the center of the top shackle pin to the datum line with the axle and springs removed.
Is it the same or slightly less now the rails do not have an upward load on them?

My car is very rusty and the passenger side is 16 3/4" and the drivers side is 16 5/8". The passenger side rail seems weaker than the drivers side and definitely has more rust.

I'm thinking the passenger side is bent upwards and should be 16 5/8 but I could be wrong. The car doesn't appear to have been in a collision. The rear quarters are already off as they were shot and the trunk floor was pretty much non existent so that is out also.

I'm hoping someone knows the answer and can offer some advice. I'll also be fitting frame rail halves rather than full length. One is a Sherman rail and the other is a genuine used rail but still just the rear half.

Cheers.

[kent]

So your looking for the dimension from the center of the rear shackle pin to this "Datum Line" And this Datum line is 6 inches below X-6? You are getting your info from the 1970 Charger Registry?? Frame specs??  Should not the height be 16"7/8? So by your measurements your frame is sagged down??  I also see the those measurements are for the 69 and 70 years. Would 68 be different?
If so I don't have my frame on a jig but on a rotisseri. That being said if I was to turn my car upside down and take a measurement from the center of the rear shackle bolt hole to a straight edge laying on top of the frame at the X-6 points plus 6 inches would that work?

Let me know. My car has the original frame rails front and rear. Like I said all I could do was get a measure from a straight edge. The straight edge I'd be using is a frame tram gauge tool and a level. Let me know if this would work for you as I'm going back to the shop in the morning.

[orange383]

Hi kent,
Yes I think that would work if you could measure yours plus 6 inches.
I think the '68 would be the same dimensions.
It would be interesting to see what yours comes out as without the suspension on there.

Many thanks!

Matt.

[Mike DC]

  
Just keep things jigged in place, weld it back together aiming at the factory specs, and hope for the best.  That's about all you can do.


When originally built, these bodies did end up reasonably rigid.  (Very good for the era, and decent even for now.)  But they had panels coming together crooked/non-symmetrical in many places.

From what I have seen, you can trust the big (quarter-size) alignment holes on the bottom surfaces of the subframe rails.  Those seemed to always be in the correct places while the car was welded together.  Everything else . . . all bets are off.  Even the rocker boxes' bottom flanges could be uneven from side-to-side, and the collision repair industry normally uses those as reference & clamping points on newer stuff.      

IIRC the original tolerance range given by the factory was 1/2".  Pretty wide.  Today it's measured in millimeters.  


As for having the body loaded up (drivetrain, panels, etc) when you weld it together?  In theory it's a good idea but it can get hard to do in practice when the whole car is blown apart for rust repair.  I don't know of any specific areas that will be in the wrong place if you have it unloaded.   Just make sure it's not sitting perched on a non-symmetrical surface/jacks.  

-----------------------------------------------


Cheapo trailer jackstands can be really useful for this sort of thing if you aren't working with a nice chassis jig of some kind.  They are threaded so the height is infinitely adjustable.  



They aren't as strong as a regular car jackstand.  But if you've got the car all torn down it probably won't be an issue.  Get several 2-packs of them and spread them out all around the underside of the car.   You can dial all the heights just right.  

I would want to combine them with some regular jackstands, though.  Both for strength, and because the tops of the screw-jacks are pretty flat so they don't hold onto the frame rails as well.  If you have the whole car held up with only threaded jacks then it could get knocked off them too easily.    

[kent]

Right Matt. I'll get to it first thing in the morning. I'll take my lap top with me and post from the shop.  I should get back to you by 10 am AST.  Someone else might come back with the right answer in the mean time but I'll let you know my results anyway.

I always try to help if I can because by the time I'm done with mine I'm going to need some help also. So hopefully the guys will see that and be willing to give me a hand.

Later Matt

[kent]

Boy you said a mouthful there Mike. You ain't whistling Dixie. Especially that Matt is only around a quarter of inch out. I think I mentioned it before on here... It's pretty obvious that there was a different man working on each side of the car at certain points in the line of production. You can tell by the welds and the spreading of the seem sealer or lack of it. On my floor pans where it joins from the front to the back. Seam sealer on one side no one ounce on the other. Guy must of went for a smoke when mine went by. Another spot is the welders when they were attaching the shock tower to the frame rails. One side not to bad the other slag and undercut. Had to be two different men. Nothing too symmetrical on my car anyway. Must of been a Monday morning car. 1/4 inch or under not to bad in my opinion.

[orange383]

Kent. Thank you so much that will be a massive help. I really appreciate you taking the time to do this for me.

Mike. I actually bought some of those stands to get my jig levelled correctly as the adjustable castors I have on the jig have rubber tyres and it wasn't easy to get the level spot on so these helped a lot. I only bought 4 though just to try them. I'll order some more tonight.

Regarding the drivetrain being fitted I was referring to the dimensions on the drawing being taken from a fully built car so with everything removed the distance from centre of the top shackle pin to the datum line might be slightly less.

You're right though I will have to hope for the best. I'm tempted to test fit all the new panels quarters, trunk floor and rear valance etc over the old rails to make sure every thing lines up before I cut them off. I know I should locked the rails in place before I started but too late now.

Thanks for your advice on this.

[orange383]

Just spent some more time double checking my measurments.
Front frame rails are bang on at 13 5/8 both sides at point "A" on the diagram.
If I jack the drivers rear frame rail up until the shock crossmember is perfectly level the passenger rear frame rail is bang on at the axle bump stop at 16 7/16 while the shackle pin to datum is 16 13/16 and if I push upwards with my finger tips it is 16 7/8.

The drivers rear is 18 1/4 at the bump stop and the shackle pin to datum is 16 1/2 so not far off. I think now that maybe the drivers rear frame rail was this way from the factory.
So I think it's in spec but I can get it closer when the new rails go in.

I'm a bit happier now. It will be interesting to see how kents all original Charger compares.

Roll on tomorrow morning!!

[Mike DC]

The repro sheetmetal is gonna stack up and make you think things are a mess.  It's probably just the repro metal. 

The lower corner caps (quarter skins to valance) are always complained about.  But it's not really the repro caps.  They are pretty accurate.  What's happening is that all the other repro metal on the back end is slightly wrong here & there.  The differences add up and show themselves when you try to fit the corner caps on.   

I think the AMD trunk floor (the one-piece version) has always gotten good marks for fitting well.  But the extensions & wheel housings can be more of a problem.   



Example of goofy original tolerances - one time I took a vertical measurement from the top corner area of the trunklid opening, straight down to the trunkfloor below it.  This was an original car.  The distance was almost 1" different from left to right. 

[orange383]

Good point about the repro sheet metal Mike and interesting that tolerances can be that far off on an original car.

[kent]

   "Example of goofy original tolerances - one time I took a vertical measurement from the top corner area of the trunklid opening, straight down to the trunkfloor below it.  This was an original car.  The distance was almost 1" different from left to right." 



I'll give that a whirl this morning when I reach the shop Mike and let you know my results. But I have a floor replacement. Got the floor from the Paddock back in 2003. You all remember them?? So that floor wan not from AMD. Oh and it was a two piece. Fit pretty nice. Just some (about 1/4 inch ) trimming around where the floor pan meet the wheel wells. Other than that fit like a glove.

[orange383]

Well after a good nights rest I've had another look at these frame rails with a clearer mind. I was getting pretty tired last night and missing the obvious.

Now my jig is made from from scrap "I" beams that I got from work but they are not as long as the car so I opted to make a removable section for the front and the rear of the frame jig. These are bolted and tacked in place.

With jacking up the drivers rear rail to level the shock crossmember I hadn't noticed the rear corner of the jig lift slightly. Adding a 20kg weight to the corner of the jig brought it back down level. The measurements on the drivers rear rail are now just 1/8 shy of what I'm looking for when working to the diagram. This is also confirmed when measuring from the garage floor which is level so I'm happy with that. But being as picky as I am I will try and get that closer.
That way I may have an easier time lining up the sheet metal and any issues won't be down to the rails.

I'm going to cross brace the sides of the removable part of the jig to the main jig to lock it into position and I think I'll be good to go but will wait for kents measurements before I start. I still have plenty of prep work to do and some uprights to make for the rails.

[kent]

Kind of late Matt. Just back at the shop now. We had to wait for the high build primer to dry. Roger my body man didn't know anything about our plans and he put some high build primer on the floor and frame rails where we fixed some little dents. So when I got here today at around 10am it was still wet,


Any way we took some measurements and they are pretty well on to the diagram. We also took some measurements from side to side and they are even and level from side to side. So both rails are even. Preety much 10" 7/8 or 16" 7/8 in your case. 10-4?? There was extensions on the tram gauge so all we had to do was make sure that the tram gauge was level with the car. I took some pictures but can't download off my phone from here as I don't have a cable to hook the phone to the lap top. I'm here for a few more hours. I'll check in later to see if you need anything else.

Later

[orange383]

That's brilliant kent. Thank you for taking the time to this. That confirms then that the measurements on the diagram would be the same regardless of wether the drivetrain was installed or not.

Bit of an update on mine. After some thought I wasn't happy with jacking up the drivers frame rail to bring it up to the required spec. My garage is very small and it wasn't easy getting the Charger onto the frame jig and the neither the car or the jig were perfectly level as it was before I bought the levelling stands. I remember there being a gap of 1/4" at the front of drivers rear frame rail between the upright and the jig.

As it wasn't the safest of situations in there with so little room I went ahead and welded the car to the jig. I closed the 1/4" gap up by raising the jig thinking this would bring the car into position and I could level everything later.

Today I decided to cut that upright where it joins the jig. This has reintroduced the 1/4" gap but now everything else is spot on with no tweaking required. Jig is level, car is level and all dimensions are as per the drawing. I just have 6 1/4" at the front of the frame rail.
The floorpan was partially removed by a previous owner and replaced with sheet metal. Maybe the extra 1/4" was introduced then or it's always been that way.

I think I can go ahead now and replace the frame rails once I've made some more uprights to support and locate the new ones.

Any thoughts?

Thanks again for the measurements kent and yours and Mikes thoughts and advice.

[kent]

Good deal Matt! Glad I could of be of some help. I'm thinking maybe a bolt and a nut welded to the bottom of you jig legs to help level it since you said your floor is not level. You could thread the bolt in or out to make your jig perfectly level and go from there. Leveling feet is what I'm trying to spit out.

Post those pics this evening.

[kent]

Hey Mike, I measured the trunk opening from one side to the other and I'm out like less than 1/4 of a inch. Not too bad I think. Roger my body man said my upper trunk lip might be slightly bent. But not too much. I took a pic of where I measured from on both sides. I'll post a few pics too this evening to show. I know no one really cares but it's great picture resizing and posting practice. This way I might not for get how to do it.

[orange383]

Hi Kent,
Maybe I mistyped before. The floor is level and I also have the levelling stands to dial it in just right along with the adjustable castors. I'll move some photos from my phone to a hard drive tonight to free up some memory and post some photos of the carnage tomorrow.

I'm feeling pretty good about things now!  

[kent]

Sorry about that. Yes would love to see some pics of her.

Always good to feel pretty good on a Saturday afternoon.

Bud time. 10-4??

[kent]

Here's a few pics of the set up I was using Matt. Not precise but close enough. Meaning going by eye to see if level. Then doing the math. Using a level but hard to hold everything.

[orange383]

Thank you kent. Your rotisserie looks good. Is tha mounted at the spring shackle holes?

If all goes well I will be removing one of the frame rails today!

[kent]

Yes it is Matt. But when I started I had it mounted to the rear bumper mounts. But then I had to finish welding in the rear bumper braces inside the trunk so I had a set of shackle mounts made. I will be switching it back to the bumper mounts before paint. The car sits a little lower on the bumper mounts and will be nicer for Roger to paint once in his booth. Since we have that option.

That's what I ment by not precise. I centered one end of the combination square on the bolt that runs through the shackle hole(I made a aluminium bushing on my lathe to center the bolt in there to make it very sturdy)then eyed it up with the tram gauge. Real close. Both sides are pretty much the same. The best I could do with out making special attachments for the tram gauge. Once I made the car level it was just a matter of doing the math.(it's a really nice rotisseri. Lots of adjustments)

Good deal on taking one of the rails out today. Just take your time and don't rush. And expect the unexpected.  Something always seems to come up when you least expect it. You think it will take a few minutes but you could be a hour or more at something??? I think it's meant to relax us. 

Good luck and yeah shoot us a few pics.

[orange383]

I really appreciate you going to all that trouble Kent especially when you have a major project of your own on the go yourself.

I've been getting everything jigged place today and that is taking quite a bit of time so I may not get as far as cutting anything out today. I need to clean up the donor piece yet and straighten the cut line from when it was removed from the donor car. The spring perch is still attached which is a real bonus. The other side is all repro so a bit more to do there.

[orange383]

Passenger side frame rail removed. Left it long for final trimming. The donor piece is 4" shorter than it could have which is disappointing as I will have a small amount of rust repair to do to the original piece that remains on the car but as this is close to the join it will also be reinforced with some extra metal on the inside of the rail so not a major problem.

I tried adding a photo from my iPhone but I need to resize it so I'll try again later on.