HAVING TROUBLE UNDERSTANDING FORD MUSTANG UNIBODY DIAGRAM

[aypsears]

Hi I am in the process of repairing a 1971 mustang fastback. I do have some questions concerning the Ford frame diagram. First I do not understand what the -10 located at the base line represents. second, the planned view contains dims as follows 47.88,20,42.50,62.50, If any of you guys out there have a explanation would be highly appreciated the rest of the diagram I understand. I have uploaded a copy of the diagram. thanks Aypsears. I also did a search and found the frame diagram posted by marks73 Thanks Mark

View attachment frame dims 001.jpg

 

[Vicus]

Aypsears

I do not have any idea for the -10

but the others are distances and the subtotals of the length:

-47.88

+67.88

= 20

+42.50

=62.50

+52.56

=115 (roughly) :whistling:

just my two cents

Cheers

Frank

 

[TommyK]

Not an expert on this but my recollection is that there are a couple of diagrams out there with some conflicting dimensions.

Scott aka Qcode351mach has decades of experience in all facets of collision repair and body work and may be able to help you decipher what is correct and what is not. He has a shop in the Danbury area so based on your location is probably somewhat local to you and may be able to consult in person.

 

[Carolina_Mountain_Mustangs]

When they design a car they establish a zero line in X,Y,Z. The left to right, X is usually the center line of the vehicle. The Y or length dimensions are usually Zero at a point in the firewall. And Z can be a plane that is below the vehicle just to set a zero. The 10 is possibly that zero plane in the Z axis.

All the dimensions in the diagram are to tooling holes that are used in the Body Shop assembly fixtures to locate the parts in the weld fixture. I think the Right one in the front sub frame is what they call the MCH or Master Control Hole. Been a while since I saw a diagram with that shown.

When you go to a frame shop they hang gages from those holes to check the dimensions shown. Q might have one of the layouts that shows more dimensions. I know when I put a front end on a 84 mustang we had dimensions from the cowl area locator holes that we set up all the panels to before welding.

It is great that you are doing the chassis verification before you start on your project. You will fight fit up if your chassis is not right. Will make a much better car if you have a true platform. Frame shop is place you need to go won't break the bank and they can pull it if it needs it. Most of our cars have sagged due to rust and bouncing down the road. The shock towers will get closer together. Most changes in the front end alignment is due to chassis moving not wear in suspension.

Didn't answer your questions but maybe shed some light on the subject.

 

[aypsears]

When they design a car they establish a zero line in X,Y,Z. The left to right, X is usually the center line of the vehicle. The Y or length dimensions are usually Zero at a point in the firewall. And Z can be a plane that is below the vehicle just to set a zero. The 10 is possibly that zero plane in the Z axis.

All the dimensions in the diagram are to tooling holes that are used in the Body Shop assembly fixtures to locate the parts in the weld fixture. I think the Right one in the front sub frame is what they call the MCH or Master Control Hole. Been a while since I saw a diagram with that shown.

When you go to a frame shop they hang gages from those holes to check the dimensions shown. Q might have one of the layouts that shows more dimensions. I know when I put a front end on a 84 mustang we had dimensions from the cowl area locator holes that we set up all the panels to before welding.

It is great that you are doing the chassis verification before you start on your project. You will fight fit up if your chassis is not right. Will make a much better car if you have a true platform. Frame shop is place you need to go won't break the bank and they can pull it if it needs it. Most of our cars have sagged due to rust and bouncing down the road. The shock towers will get closer together. Most changes in the front end alignment is due to chassis moving not wear in suspension.

Didn't answer your questions but maybe shed some light on the subject.

Thanks and yes you did shed some light on the subject. I want to check the car out for any type of damage

 

[Qcode351mach]

In order to measure the car your going to need to jig the unibody level front to back and side to side at the rear of the rocker pinch weld and at the front of the rocker pinch weld. Once thats done you need to set up a set of bars with pointers set to the correct heights in the spec, locations (from the spec sheet. Take a look at my pics here and you can see how I jigged the car on a dolly then the bars underneath with pointers. Not sure where in CT you are but if close you could always stop by my shop for help.

http://s1136.photobucket.com/user/FUZZENUT/slideshow/MUSTANG-%20BACK%20FROM%20THE%20GRAVE

 

[Stanglover]

Now I know exactly why I went to California to buy my Mach 1, which turned out to be TOTALLY rust free............. I mean no rust anywhere other than some very minor surface oxidization. Die draw lines are still easily visible on the frame rails!! I absolutely applaud you guys who are willing to take on "rust-buckets" and bring them back to life. Also, I enjoy reading and learning about the restorations going on. I have also enjoyed sharing what I can from my experience.

Geoff.

 

[aypsears]

In order to measure the car your going to need to jig the unibody level front to back and side to side at the rear of the rocker pinch weld and at the front of the rocker pinch weld. Once thats done you need to set up a set of bars with pointers set to the correct heights in the spec, locations (from the spec sheet. Take a look at my pics here and you can see how I jigged the car on a dolly then the bars underneath with pointers. Not sure where in CT you are but if close you could always stop by my shop for help.

http://s1136.photobucket.com/user/FUZZENUT/slideshow/MUSTANG-%20BACK%20FROM%20THE%20GRAVE

Thanks Q I just might come up to visit you some time in the coming weeks also looked at your photos of the trammel under the car. right now I have the car jacked up and I am using chief frame gauges. I have a body guy in town who has helped me in the past with this car. I was just trying to find out if anyone had an idea concerning those dims on the diagram.

 

[Qcode351mach]

In order to measure the car your going to need to jig the unibody level front to back and side to side at the rear of the rocker pinch weld and at the front of the rocker pinch weld. Once thats done you need to set up a set of bars with pointers set to the correct heights in the spec, locations (from the spec sheet. Take a look at my pics here and you can see how I jigged the car on a dolly then the bars underneath with pointers. Not sure where in CT you are but if close you could always stop by my shop for help.

http://s1136.photobucket.com/user/FUZZENUT/slideshow/MUSTANG-%20BACK%20FROM%20THE%20GRAVE

Thanks Q I just might come up to visit you some time in the coming weeks also looked at your photos of the trammel under the car. right now I have the car jacked up and I am using chief frame gauges. I have a body guy in town who has helped me in the past with this car. I was just trying to find out if anyone had an idea concerning those dims on the diagram.

Your welcome,

The old style hanging gauges ? No Idea what the -10 is on that diagram. I really don't see where it comes into play any way. I don't have it on the chart I have. A much more accurate setup is using pointers set to height from the base line or datum line up like in my pictures.

 

[will e]

The top down also view has a number 20 that appears to be a similar reference point. These are the only two that are not carried out to the hundreth. Well, the 115. MUSTANG is the other exception but I think this was either a mistake or they were short on space for type. You will note even the rear distance of 43.00 includes the extra decimal points.

But the values don't make sense in the side view. The first value, 12.38 is visably longer than the value next to the C which is 15.86 and the value to the right of that is clearly almost the same length but it shows at 10.4.

I am stumped.

 

[basstrix]

The datums and considered to be "exact". Datums are exact because they are theoretical and considered to be of "perfect form". Real features are dimensioned from the datums and have tolerance values because they do physically exist and do have variability in form and location. In the case of the plan view, the datum has been aligned with the gauge holes aft of the trans cross member.

It may be that the chassis was on some sort of a fixture that had a surface aligned with the -10 datum. If nothing else, 10 is easy to add/subtract from some other arbitrary datum.

In the days of hand-drawn "blue prints" it was not uncommon to have features that were not accurately scaled. The same argument can be made for the COUGAR/MUSTANG references. Different dims, same picture. There may exist some chassis where these two holes are positioned as shown and they reused the plan and side views to create this document.

Side note: It's typical for a drawing to have a note in the title block which states "DO NOT SCALE".

 

[aypsears]

The datums and considered to be "exact". Datums are exact because they are theoretical and considered to be of "perfect form". Real features are dimensioned from the datums and have tolerance values because they do physically exist and do have variability in form and location. In the case of the plan view, the datum has been aligned with the gauge holes aft of the trans cross member.

It may be that the chassis was on some sort of a fixture that had a surface aligned with the -10 datum. If nothing else, 10 is easy to add/subtract from some other arbitrary datum.

In the days of hand-drawn "blue prints" it was not uncommon to have features that were not accurately scaled. The same argument can be made for the COUGAR/MUSTANG references. Different dims, same picture. There may exist some chassis where these two holes are positioned as shown and they reused the plan and side views to create this document.

Side note: It's typical for a drawing to have a note in the title block which states "DO NOT SCALE".

Thanks everyone for there input I measured the unibody according the the factory dims came out square