Bent frame--how bad is it?

[Russell Reay]

I just laid a 4 -foot carpenter's level on the frame, centered on the middle cross-member. The sag is about 1/8 of an inch right at the x-member. There are no cracks, and no other evidence of trauma to this frame. Is 1/8" enough that I should have the frame straightened before putting the car back together? I read Les Andrews procedure for frame straightening, but I would probably take it to a shop. I don't wish to ignore a good situation in pursuit of perfection, but neither do I wish to be foolish and neglect this flaw if it will be the source of problems in the future.

[Oldbluoval]

Have you also checked for square? I’d also pull a sting from front to back and see if the 1/8 is really a bit more than over just the 4’ span....I bet it is.
The car has to assemble full length so if the 1/8 turns into 1/4 you may be getting close to vertical alignment issues on gaps and hood alignment
Just imho

[Flathead]

They usually sag the most where the rear engine mounts fasten to the frame, put your level across that spot on each side.

[Mike Peters]

What oldblueoval says X2. Hoods are difficult enough to align with the cowl and radiator shell properly without having to contend with a sagging frame. Run a tight string from end to end.

[SeaSlugs]

Originally Posted by Russell Reay

I just laid a 4 -foot carpenter's level on the frame, centered on the middle cross-member. The sag is about 1/8 of an inch right at the x-member. There are no cracks, and no other evidence of trauma to this frame. Is 1/8" enough that I should have the frame straightened before putting the car back together? I read Les Andrews procedure for frame straightening, but I would probably take it to a shop. I don't wish to ignore a good situation in pursuit of perfection, but neither do I wish to be foolish and neglect this flaw if it will be the source of problems in the future.

recheck square and flatness down the whole length of each frame rail. If your frame is "naked" nows the time to do it right and have it straightened. You wouldnt build a house on a lopsided foundation and probably not even a garden shed :P

[CWPASADENA]

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Yes,

Take care of the sag NOW. It will save you from a lot of problems later.

My opinion,

Chris W.

[todd3131]

I didn't check my frame and went to assemble it and had a hell of a time making the hood fit somewhat. I was young at the time. I have plans to pull it apart when my son graduates rebuild the motor and fix the frame my guess is it is out the 1/8 that you have and probably more. Yes absolutely have it straighted.

[BRENT in 10-uh-C]

Originally Posted by Russell Reay

I just laid a 4 -foot carpenter's level on the frame, centered on the middle cross-member. The sag is about 1/8 of an inch right at the x-member. There are no cracks, and no other evidence of trauma to this frame. Is 1/8" enough that I should have the frame straightened before putting the car back together? I read Les Andrews procedure for frame straightening, but I would probably take it to a shop. I don't wish to ignore a good situation in pursuit of perfection, but neither do I wish to be foolish and neglect this flaw if it will be the source of problems in the future.

Yes, 0.125" is WAY too much. Let 0.000" be your target. It is very obtainable.

Not sure of Les' recommendation however I can share with you that using a jack to bend a bent frame is the incorrect way to do this. This topic has been discussed several times here, -and heat & metal shrinking is the only proper method to repair a frame where it will last. Think of a bend in the metal the same as a wrong, ...and we all know that two wrongs do not make a right.

[todd3131]

Originally Posted by BRENT in 10-uh-C

Yes, 0.125" is WAY too much. Let 0.000" be your target. It is very obtainable.

Not sure of Les' recommendation however I can share with you that using a jack to bend a bent frame is the incorrect way to do this. This topic has been discussed several times here, -and heat & metal shrinking is the only proper method to repair a frame where it will last. Think of a bend in the metal the same as a wrong, ...and we all know that two wrongs do not make a right.

Yes tried the jack at the time and need to fix that spot also.

[Russell Reay]

Visited a frame shop in town today--they are scheduling into October! The owner described chaining the frame to the 'frame machine' and applying pressure with a Port-a-Power. I don't see how that is any different than Les's method. I understand metal shrinking on thin sheet metal (never tried it, though) , but how would you shrink something as heavy as frame steel (10 ga?) ?

[Oldbluoval]

Make sure it’s “square” before you leave his shop
Out of square can make for lots of weird assembly
Measure in “X” fashion

[todd3131]

I for one would like to know how you end up squaring it up.

[Oldbluoval]

Usually on a frame machine
The sag can be taken care of as RR states. But not familiar with the heating as Brent describes. I have enough confidence in Brent to believe him.
I’ve heard from some of the Super Restorers that they “tighten up”the frame rivets also.
Probably getting subject drift …..

[BRENT in 10-uh-C]

Originally Posted by Russell Reay

Visited a frame shop in town today--they are scheduling into October! The owner described chaining the frame to the 'frame machine' and applying pressure with a Port-a-Power. I don't see how that is any different than Les's method. I understand metal shrinking on thin sheet metal (never tried it, though) , but how would you shrink something as heavy as frame steel (10 ga?) ?

Russell, with no disrespect to Les and his book, I will just say that not everything that is printed in that book is totally accurate. Others will confirm this. This topic of frame straightening has been covered several times on this site with a full explanation of the process. The search function on this site is your friend.

Also, you likely need to find another frame shop that is more familiar with the process. In a nutshell, your frame has been stretched to create the bend. If someone uses a jack (i.e.: Porta-power) to move the rail, what they are effectively doing is just bending the metal in a different direction. Now you have two separate bends, and not a corrected bend. A knowledgeable craftsman can straighten your frame and never have a jack (-or Porta-power) within sight.

Originally Posted by todd3131

I for one would like to know how you end up squaring it up.

The way we do it is use a tram gauge and measure in a diagonal 'X' pattern to compare measurements. I have copies of the A-5005-* frame drawings that gives the dimensions from certain holes or attachment points.

To square a skewed frame, compression is placed on the longest tangent to pull the frame back square. (-think 'come-along winch' or turnbuckle & cables to pull with) At that point where it is back within specification, it is best to heat and re-buck all of the rivets at the crossmembers to hold the A-5015/16 Frame Side Member (rails) square with each other. This process is best done after the side members have been straightened both in a horizontal and vertical direction.

[Russell Reay]

Checked for square. There is a hole in the top of the frame rail directly opposite the dipstick, and a corresponding hole on the other side. With the engine still in place, that is the forward-most feature I can measure to. From the extreme rear-most points on the frame diagonally to the center of these holes, I get a difference of 1/16". Will search the forum archives for more about the frame straightening process. If anyone has a link to an especially good thread, please post it.

[BRENT in 10-uh-C]

Originally Posted by Russell Reay

If anyone has a link to an especially good thread, please post it.

https://www.fordbarn.com/forum/showthread.php?t=162055

https://www.fordbarn.com/forum/showthread.php?t=168668


And here is one where the jury is hung between hypothetical and real-world experiences. Still an interesting read where perceived theory often overshadows reality. (Kinda like the mindset that you should never clean Model-A parts in gasoline because it could explode. I agree it could, and most of us here have done it more than a couple of times without any casualties though. So is the occasional using of gasoline for parts cleaning right or wrong?? )

https://www.fordbarn.com/forum/showthread.php?t=119693

[Russell Reay]

Brent-see PM

[todd3131]

Good information thank you! Maybe the best part is I bring it to you to get it right. At this point in my life I just want it done and done correctly.

[Russell Reay]

Update!! Spoke with Brent and referred to his post at https://www.fordbarn.com/forum/showthread.php?t=119693. Used heat with my rosebud--no quenching- and the frame returned to a sag of a sheet of paper. Follow the logic he presents, and bottle jacks and frame machines have no applicability. After a coat of paint I can return to re-assembly. Thanks Brent!

[Oldbluoval]

Russell
So where did you heat it? How did you decide where and how much area to heat. All parts of the “C” frame?
Enlighten please.

[Bob C]

If you look at post #11 in the link Russell posted you can see where Brent
heated the frame.

[Russell Reay]

First of all I stretched a chalk line from a hole in the front of the frame horn back to a hole in the top chord just in front of the rear running board bracket. This showed me that I had about 1/8" sag between the middle crossmember and the rear hood holddown bracket. Per Brent's standard, the sag should be 0. With reference to Brent's pics in the cited post, I heated the bottom chord in that area using a #6 rosebud tip. No particular need to heat the web, and if so, only a short ways up from the bottom. DO NOT heat to red hot. Heat hot enough to make a wet towel sizzle and steam, but DO NOT quench it. Use the sizzle and steam description as a performance standard, not an actual practice. Shoot the heated segment w/ compressed air, or not. This is Brent's standard, not my own invention--credit where due. I let the heated frame cool overnight, and this morning I stretched the chalkline, and could just about see daylight between it and the frame. I have declared victory, and will continue with re-assembly. Note:--the first time I tried this method, the engine was still in, and I heated a length of ~8" in front of the middle X-member and the same under the motor mount. The next day the sag had increased from 1/8" to 1/4". Pulled the engine, removed the motor mounts, talked w/ Brent on the phone, and proceeded as described.

[Oldbluoval]

I found on another thread. #11 is my own thread…on this one!
Apparently this subject is addressed on various threads
Got it thanks

[nkaminar]

What Mike K wrote in May of 2010:

OK, I've heard this heat shrink/ cold bend debate about frame straightening too many times. Let's apply a little engineering/ math:

If a 4' long straight edge across the motor mount shows a 1/4" (0.250000") sag, the difference in the top and bottom chord will be 0.00260". I dont know if it will be all stretch in the bottom chord or all compression in the top. Likely some mix of the two, as the same sectional area of the same material makes up both chords.

Applying either straightening method, cold or heat, will cause one chord to compress (shorten) as the other stretches. Cold press will cause the chord acted upon (pushed with the jack) to re-compress while the opposite chord stretches. Heat shrink will cause the chord acted upon to shrink while the opposite chord will stretch. Whether the stretch/compress between the two chords will be 50/50 or 90/10 I don't know, but both chords will be affected by either method.

OK, let's assume the worst: 1) The sag caused only one chord to stretch or compress 0.0026". 2) The method or technique you choose and apply to straighten the frame acts only on the wrong chord. 3) Only one of your two frame rails was bent.
RESULT OF STRAIGHTENING: A frame that has one side 0.0052" longer.

If anybody thinks Henry's frames were accurate within 5 thousanths, think again! There's more slop than that in every bolt hole.
__________________

[nkaminar]

I checked the math. 1 minus the cosine of the arcsine of 0.25/24 times 5 inches is 0.00027 inch. .25 inch the amount of sag over 4 feet (48 inches) 24 inches is half of that. 5 inches is the frame depth So my math shows a factor of 10 less than what Mike K got. He used a different way of calculating the difference, using the chord. Please, if you can, check the math.

A stretch of .005 inch over 5 inches would result in the reduction of thickness of 0.1% or 0.00025 inch. If you take my figures then the reduction in thickness is 0.000025 inch.

In any case the difference in length (and thickness) of the frame is insignificant.

[BRENT in 10-uh-C]

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Originally Posted by nkaminar

I checked the math. 1 minus the cosine of the arcsine of 0.25/24 times 5 inches is 0.00027 inch. .25 inch the amount of sag over 4 feet (48 inches) 24 inches is half of that. 5 inches is the frame depth So my math shows a factor of 10 less than what Mike K got. He used a different way of calculating the difference, using the chord. Please, if you can, check the math.

A stretch of .005 inch over 5 inches would result in the reduction of thickness of 0.1% or 0.00025 inch. If you take my figures then the reduction in thickness is 0.000025 inch.

In any case the difference in length (and thickness) of the frame is insignificant.

Neil, a chain is only as strong as the weakest link. It doesn't matter if it is weaker by .0001%, ...however when there is enough stress, the likelihood of the next stretch or failure will be that one that is the weakest. Engineers tend to over-analyze and because I am not in that area of study, you can use figures that I cannot, -nor do I choose to understand. That is not to say I am wrong, -but it is to say that just because you have a theory using equations as your foundation does not make you correct. When there is an area that is compromised by whatever the amount of the stretch, -then it is weaker. I spoke with Mr. Reay by telephone for a bit, and he learned that after heat was applied, the sag in the metal became noticeably greater. In all likelihood, this was caused because the area that he heated was not stretched to begin with from any trauma, and therefore it expanded from the heat to exacerbate the sagging issue. My point is, by theory this should not happen, ...however those of us that have hands-on experience know differently. My feelings is if you do not agree with me in this area, then state your opinion and actual hands-on experiences, ...and then lets both move on.

[jerrytocci]

I would do it "cold". Put thick wood across the frame to raise the jack and protect the frame. The higher the jack the easier it can be done

[rotorwrench]

When a frame bends, the inside angle is compressed and the outside angle may be stretched. I would say that both application of pressure and heat to shrink can be used to affect the movement needed. If you only shrink, the metal that is compressed doesn't move very well. Shrinking and stretching in moderation can both be accomplished. 1/8" is a fair bend but I've seen worse. A person can discuss this with the frame man. One who knows how steel members react will understand.

Cold bending can be effective but it depends in large part on the profile, shape, & thickness of the member plus the extent of the bend. The experience level of the man performing the job is also important.

[nkaminar]

In response to Brent: There is nothing wrong with the method he is using. Heating and cooling with a wet rag is done all the time in body work to shrink metal and I have done that myself to straighten out door panels. I think that there is also nothing wrong with chaining down the frame and bending it using a bottle jack. Lots of frames have been straightened that way and that is what I plan to do to my frame when I get the time. One advantage that I can see with the cold bending is that it can be done on an assembled car. Brent may object to that but I have seen the frame on an assembled car straightened with a bottle jack.

[rotorwrench]

A nice big I-beam, chains, one or more hydraulic jacks, or other items such as wood blocks or other metal members can be used to straighten frames. It's been done this way since Christ was a corporal. Cracks and fatigue are the major concerns and should be addressed. Sometimes reinforcement plates or patches are needed to fight the sag of an old fatigued frame.

Straightening with the car assembled does not allow a person to check for other bends, twist, or squareness of the whole frame very well nor will it be easy to manipulate to correct all deficiencies. I would only try correcting a bare frame. Actions can have adverse reactions

[Tinbasher]

Use Brent's technique to straighten the frame. It works great and it lasts. I always use to straighten them cold on a frame rack. How I use the heat and shrink the side and lower edge and it works great. I've done it one driving cars by placing the axle stands about 8" behind the rear engine mount and heating the frame and let the weight of the front of the car bring the frame back into shape. Heating to a dull red and cooling works well. About 3 hrs. a side on a frame with 3/8" sag. JP