Frame Sag, How much acceptable?

[AYooperA]

I am in process of doing a frame off restoration of my ‘29 Phaeton. I am getting about .080” sag equally on both sides of frame. Typical low area is by the 2 bolt frame bracket that secures cowl. Is not enough to concern myself and can be adjusted by body blocks and pads? Frame to be sandblasted and painted.

[Fullraceflathead]

Do you have access to a large surface plate to check the flatness of the level that you're using? Your level may not be as flat as you think.

[jwmckenzie]

Run a string or fishing line from front to back. Take three blocks (same dimensions) and put a block under the string front and back. Take the third block (red arrow) move it along the frame and see how much and where the sag is. Here is a pic to help with the description.



I personally wouldn't worry about 0.08". Depends on how picky you will be with sheet metal alignment of the hood, doors, etc.

[Kevin in NJ]

You are not measuring properly.

You need to do the string along the length of the frame.

Really, You want to take the little bit of time to do it right. It really is not hard to make your frame straight.

Especially with a pheaton body you want the best platform for the body. You will be spending way more time trying to get the body straight then then time it takes to level the frame.

Also consider the order at which you do things with the car. It is in your best interest that you blast and level the frame first. Then using a long straight edge, they are cheap at HD lowes, make the running board brackets level to the top of the frame and the holes square to factory running boards. This is actually easy to do. I bent mind cold with a pipe coupler and a long metal rod.

Then set up your front fender brackets and light bar. The light bar should look balanced and the bolts should go in easy at each end. Once the brackets are set up put on the running boards and splash apron and fit your front fenders. Any welding MUST be done on the frame and you need to keep the bead edge inline and verticle with the running board edge (I leveled the top of my frame to do this).

Once those parts are fitted you can move on with body repairs and alignment. Then take it all apart and start painting and building everything.

The restoration process goes better with that order and reduces time later in your build and you are not painting until after major fitting has been done.

That my thoughts take or leave it.

[wrndln]

I don't think you have much of a problem. The way you checked it seems pretty good to me, as long you didn't have any rivet interference under the straight edge. You may need to use another rubber pad or two toward the center on each side. Phaeton bodies are hard to align anyway because of the loosey goosey body.
Rusty Nelson

[Road Trip]

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Check it for square while you're at it.

[AYooperA]

I used a 6 foot level so I can see doesn’t take the whole length of frame into consideration. I like the block and string line method I will try that. Also take suggestion to test dimensions of all brackets prior to finishing, another good idea didn’t think of. One running board bracket has been pushed back and I know that one needs correcting at a minimum. This is a late ‘29 and all fender brackets are stampings.
Used an old junk Model A frame as a dolly for body.
Focusing on the frame and mechanicals so may be a while before I tackle that phase.

[Conaway2]

This is the best time to get the frame as straight as you can - it ll make a difference.

I recently straightened the frame on a car I’m presently restoring - used the string method to measure. I straightened it cold (like post #4) using a long 6” X 6” timber with a long steel I-beam on top. Each end of the frame was held with chains while I used a 20-ton bottle jack under the frame at the rear motor mount. There was an article published some time ago on how to do this - I think the title was something like ‘straightening the frame the shade-tree way’.

https://www.mafca.com/downloads/Rest...aightening.pdf


Good luck !
Jim

[BRENT in 10-uh-C]

Originally Posted by Conaway2

This is the best time to get the frame as straight as you can - it ll make a difference.

I recently straightened the frame on a car I’m presently restoring - used the string method to measure. I straightened it cold (like post #4) using a long 6” X 6” timber with a long steel I-beam on top. Each end of the frame was held with chains while I used a 20-ton bottle jack under the frame at the rear motor mount. There was an article published some time ago on how to do this - I think the title was something like ‘straightening the frame the shade-tree way’.

https://www.mafca.com/downloads/Rest...aightening.pdf

From my vantage point, the 'shade-tree way' is the perfect example of how a professional would NOT do it. Even more to the thought, if the late Bob and I were given two identical frames bent/sagging the same amount to repair, I could have my frame repaired in less than the time it took him to get set-up with jacks, chains, timbers, etc. in a effort to do his, ...and my method of just using a torch & water will last WAY longer than his method simply because I am correcting the initial trauma instead of adding a second bend to counteract the first one. My method has been discussed more than a few times here, and the success of my method has also been discussed by contributors here.

[updraught]

http://www.mtfca.com/discus/messages/118802/123360.html

[BRENT in 10-uh-C]

Originally Posted by updraught

http://www.mtfca.com/discus/messages/118802/123360.html

Wow, that was a trip down memory lane. Topic was from over 12 years ago however the method remains the same. Thanks for sharing.

[Kevin in NJ]

Running board brackets are pretty simple.

They will have the bolt hole in line side to side. The top of the running boards will be parallel with the top of the frame. The fore aft dimensions between the holes need to match the holes of the running board brackets.

Simple constrants that allow you to accurately set the brackets cold. I have a 8' straight edge I bought from Lowe's for not much money that lets me make the checks. Plus it had been useful for other tasks.

[CT Jack]

AYooperAI hope you don't lose any sleep over your findings. You are working with a mass produced car made by Ford with minimal finesse when compared to other vehicles of the period. The basic structural design of our A's are very similar to the T but with improved stiffness. The bodies all had their individual frames and were assembled as a completed unit or module away from the final assembly line. They were then transferred to the final line and bolted at specific points to the frame. The bottom side of the body did not exactly mate to the entire top surface of the frame it was mounted to. If you have a major gap between the assembled body and frame mounting points I would use shims to correct for any differences. The frames on our vehicles were also designed to travel on non-paved roads and are capable of flexing. An .080" gap in my view is not a concern.

[Tinbasher]

Always go for "0". Get the frame as straight as you can. In the day conventional frames where aloowed 3/16" of play. Like someone mentioned you'll spend more time shimming the body. So get it as straight as you can.

[gdmn852]

Hello, when you get to mounting the body , check the new body blocks against the original ones if you still have them, sometimes the repro blocks aren’t exactly like the originals , I had to cut the width on some of mine to fit in body channels,if the thickness is different this will also effect the amount of shims you may need, I think the judging standards give about a quarter of an inch gap between body and running board aprons but have seen it more than that on cars on the road.

[john in illinois]

Post #6 is also important.

John

[BillCNC]

Ever since the thread was posted, I have been searching for my paperwork from when I did my frame but for some reason, I can only find page 1 of 2.

To get my frame square I used page one. Looking at the sheet for a few minutes it should be self explanatory. The ledger on the right side is the guide on measuring left to right and right to left on the frame at the rivets. The chart on the top left is the rivet location on each rail. The colored boxes are color codes of the dimension ranges. As you can see, my frame was a project to start with.

Page-2 is pretty much laid out as page-1 for squareness. I'll keep looking for the other page. To get it level basically I leveled the frame on jack stands and laid 1/8" stranded cable over the top of the rails rivets and hung 50lbs weights at each end tensioning the cable. I then measured between the cable and the frame.

Is my method overkill, You Bet! But I possibly have the straightest model a frame around. It's within 1/32" to 1/16" from perfect anywhere on the frame. My thinking is that if your going to go through all the trouble to straighten a frame, you might as well be #all's-deep into it, if not, what's the point.

Regards
Bill

EDIT: I'll get the page scanned and repost it so it's more legible if someone needs it.

[Rob Doe]

Originally Posted by BRENT in 10-uh-C

Wow, that was a trip down memory lane. Topic was from over 12 years ago however the method remains the same. Thanks for sharing.

Brent, in your pictures from the MAFCA threads, you had four places to repair/straighten.

I assume you used a rosebud acetylene torch?

Did you heat on the inside, flame focused on the bottom rail?
Did you measure the general temps of the area with an IR temp gun?
Were the temps 230 ish? Or?

Did this require multiple iterations of heat to get the frame straight? If so, how long did you let things cool before putting the string back on and testing with the blocks?

I've already learned a ton from this. 3x rivet gun, heat the rivet bright red/orange from top until red on the bottom, then buck.

Thx.

[BRENT in 10-uh-C]

Originally Posted by BillCNC

Ever since the thread was posted, I have been searching for my paperwork from when I did my frame but for some reason, I can only find page 1 of 2.

To get my frame square I used page one. Looking at the sheet for a few minutes it should be self explanatory. The ledger on the right side is the guide on measuring left to right and right to left on the frame at the rivets. The chart on the top left is the rivet location on each rail. The colored boxes are color codes of the dimension ranges. As you can see, my frame was a project to start with.

Page-2 is pretty much laid out as page-1 for squareness. I'll keep looking for the other page. To get it level basically I leveled the frame on jack stands and laid 1/8" stranded cable over the top of the rails rivets and hung 50lbs weights at each end tensioning the cable. I then measured between the cable and the frame.

Is my method overkill, You Bet! But I possibly have the straightest model a frame around. It's within 1/32" to 1/16" from perfect anywhere on the frame. My thinking is that if your going to go through all the trouble to straighten a frame, you might as well be #all's-deep into it, if not, what's the point.

Regards
Bill

EDIT: I'll get the page scanned and repost it so it's more legible if someone needs it.

Geez, you are right about overkill! You definitely have the Grand Prize award for achievement locked-up for that worksheet!! Even we do not use such a detailed method!!

To begin with, straighten the rails to be flat. Once that has been done, measure from the center of the rear crossmember tie-bolt hole (-the square hole) up to the center of the #1 body mount hole in the frame on each side, and you should find the measurement to be matching at 73 57/64th inches ...which is a tad over 73 7/8". Then measure the opposite side and see that those two numbers match. To verify, then place a string from the center of the square hole in the rear crossmember (-or a laser) to the center of the square hole in the front crossmember. Next measure at various points from the string (-or laser) line between the rear and front crossmembers to each area along the frame rail to verify the measurement on each side match. When both measurements match the entire length, the frame is square. At that time you will heat and re-buck all of the frame rivets. After you have re-bucked about ½ of hem, recheck all of your measurements and correct as necessary. Once the frame is finished, you should easily be able to match less than 1/32" sag.

Originally Posted by Rob Doe

Brent, in your pictures from the MAFCA threads, you had four places to repair/straighten.

1 I assume you used a rosebud acetylene torch?

2 Did you heat on the inside, flame focused on the bottom rail?

3 Did you measure the general temps of the area with an IR temp gun? Were the temps 230 ish? Or?

4 Did this require multiple iterations of heat to get the frame straight? If so, how long did you let things cool before putting the string back on and testing with the blocks?

I've already learned a ton from this. 3x rivet gun, heat the rivet bright red/orange from top until red on the bottom, then buck.

Thx.

1 Not always. We use a pencil-tipped torch (Henrob brand) for the rivets as we can concentrate the heat into the rivet and not the surrounding areas. That torch is plenty adequate to heat the rails.

2 Probably heated in multiple areas just trying to spread the heat out over a larger area. Experience from straightening other frames generally dictates how area we heat and quench.

3 Nahh, using a heat gun is just a waste of time for us. Somewhere between straw and blue colors will cause the quenching water to turn to steam when applied to the hot metal. If it makes steam, then that is hot enough to do what we need to shrink the metal.

4 Let the metal temps normalize back to the entire frame area being room temperature. Sometimes a couple of subsequent heat cycles in surrounding areas are needed for minute corrections.

As far as heating the rivets, the key is transferring the heat down into the rivet shank so that it will swell during the bucking process to fill the entire hole of the frame rail and crossmember. If you just heat the head until red but not the shank, all it does is deforms the rivet head but does not tighten the rivet down in the drilled hole. If you use too large of a flame, it heats the surrounding metal of the crossmember and frame where the hole is enlarged by the heat just like the rivet. When it is re-bucked during that scenario, you don't allow the rivet to swell enough to be effective.

.

[BillCNC]

Originally Posted by BRENT in 10-uh-C

Geez, you are right about overkill! You definitely have the Grand Prize award for achievement locked-up for that worksheet!! Even we do not use such a detailed method!!

Sheet 2 measures from the frame center outward for both sides and the measurements of flatness as well. Also the front crossmember needed to be removed for the bending process. Riveting was much easier than I had anticipated.

Actually, it was the first frame I tackled a frame that needed this much work so I figured that stripping a car to a bare frame isn't something you spend a few minutes on then reassemble.

After all that work a few years ago, I have to go and have my frame trammed because I was rear-ended this past March sitting at a stop sign. So if she's bent again, the prosses should go faster.

Regards
Bill