frame sag

B

Bronco

Junior Member
Need some expert advice. Just noticed after my last drive that my frame is bending just in front of my motor mounts. Can this be repaired, or do I need to find a new frame? Will I do damage to the engine and trans if it is driven before its repaired or replace? Your opinions are greatly appreciated.
Bronco
 
A much discussed subject. There is an article in the May-June Restorer, by Gordon Fischer, on pages 5 -10 that addresses the problem of frame straightening with illustrations and directions. Have yet to hear of a solution possible with the body in place?
 
Bronco said:
Need some expert advice. Just noticed after my last drive that my frame is bending just in front of my motor mounts. Can this be repaired, or do I need to find a new frame? Will I do damage to the engine and trans if it is driven before its repaired or replace? Your opinions are greatly appreciated.
Bronco
Click to expand...


If you do a search on this forum on Frame Straightening, you will find it has been discussed extensively.

I guess I am more intrigued about knowing about your comment where you say your frame is bending. Is this statement more about where you just noticed it was bent, --or that it is bending each time you drive the car? Have you determined anything specific is causing the bend?

Next, what is it hurting by continuing to drive it in this condition? Is it only causing poor hood alignment --or something worse?

And finally, are you thinking this car was previously restored and at that time the frame was straightened but now it is re-bending again?

.
 
Background on when the bending began and what caused it may be interesting and help you avoud the same causes in the future, but it doesn't help you fix it.

At the rear engine mounts is where the highest concentrated load and bending moment in the whole frame is concentrated. It's where most of the frame sagging occurs.

Forcing the frame straight again is the obviously necessary fix but then the frame is weaker than before and will sag again under lesser loading next time. My roadster's frame had to be straightened while the body was off during restoration (jacks and tie-down chains). I then had a professional welder weld a "reinforcing doubler" made of 1/4' steel, 16 inches long to the underside of the frame centered on the motor mount location. The doubler is as wide as the bottom flange of the frame. When ground smooth and feathered at both ends it doesn't look too bad.

I hated to have to "disfigure" the frame that way, but I never wanted to have a bent frame problem again. And it hasn't budged in 8000 miles of driving often with full passenger loads (including 3 in the rumble seat), speed bumps, potholes, etc.

If I were to list a few of the things that Henry didn't get exactly right, I'd have to say the marginal, if not flimsy, frame design. To have gone to the next gauge or two thicker steel in the frame would not have been that high a weight or cost penalty and would have been well worth it.

Earle
 
I too am experiencing sag based on the widening hood seam at the bottom of the hood side panels. I will be straightening the frame in the near future. I anticipate using jacks and heat to shrink the bottom of the rails. This brings up a question that I have regarding Flot-O-Motor mounts. Since the bending seems to occur at the flywheel cover motor mounts wouldn't the use of FOM alleviate that by cushioning the load at that point?
 
My 31 roadster frame was sagging. I tied it down front and rear and put a jack under the motor mount. Worked for me. I've been driving since straightening for about ten years now with no recurring problem. I think the frames got bent when teen agers used them for jeeps back when they were worth twenty-five bucks.
 
Milton said:
I too am experiencing sag based on the widening hood seam at the bottom of the hood side panels. I will be straightening the frame in the near future. I anticipate using jacks and heat to shrink the bottom of the rails. This brings up a question that I have regarding Flot-O-Motor mounts. Since the bending seems to occur at the flywheel cover motor mounts wouldn't the use of FOM alleviate that by cushioning the load at that point?
Click to expand...

Actually, its generally believed they aggravate the problem. The original mounts were designed to create a cross member in conjunction with the flywheel housing. FOM's defeat that purpose.
 
The frame was bent cold. Then straighten it cold and it will go right back to like it was before the bend. Putting heat to the frame could anneal the frame and make it softer and easier to bend where the heat was applied. Putting heat to the frame will straighten it only where the heat is applied. The actual bend covers a longer area than just the small heated area. Chain down the frame ends and jack up the sags to straighten again. When I was a kid on the farm, it was always fun to see how much air we could get with the old cars. We did bend a few frames. Puckered body panels, ill fitting doors and hoods, and broken motor mounts were the immediate results of our wild entertainment.
 
pat in Santa Cruz said:
Actually, its generally believed they aggravate the problem. The original mounts were designed to create a cross member in conjunction with the flywheel housing. FOM's defeat that purpose.
Click to expand...

I understand the x-member concept, but that is a lateral situation while sag is perpendicular to that, so my question still stands regarding FOMs and sag. Can you tell me the "problem" that is aggravated?

However, since the original mounts do create a rubber mounted x-member what is its purpose? There are three real (riveted) x-members in a model A frame, one at each axle and one centered between the other two. So, with three little 1/4" bolts through the frame, mounts, exterior plates and two rubber pads what is the gain of an additional x-member less than two feet away from the center x-member? In other words, what lateral forces are diminished with the use of this theoretical x-member design.

Geo. H
"I think the frames got bent when teen agers used them for jeeps back when they were worth twenty-five bucks."

I'll vouch for that, nothing like an off road experience in a Model A. :D
 
Milton said:
I understand the x-member concept, but that is a lateral situation while sag is perpendicular to that, so my question still stands regarding FOMs and sag. Can you tell me the "problem" that is aggravated?

However, since the original mounts do create a rubber mounted x-member what is its purpose? There are three real (riveted) x-members in a model A frame, one at each axle and one centered between the other two. So, with three little 1/4" bolts through the frame, mounts, exterior plates and two rubber pads what is the gain of an additional x-member less than two feet away from the center x-member? In other words, what lateral forces are diminished with the use of this theoretical x-member design.

Geo. H
"I think the frames got bent when teen agers used them for jeeps back when they were worth twenty-five bucks."

I'll vouch for that, nothing like an off road experience in a Model A. :D
Click to expand...

milton,
i'm with your thinking on this subject, as i've thot the same. in addition, all you've done with the change to FAM units is change the rubber location from rail sides, to another location in the mounts,no? ...like what cars have from then on. and, roads today are mostly, not remotely bad as what was back when. we don't treat our cars to loads/roughly like was common back then. finally, we lighten flywheels and clutch setups,etc to even improve/lessen frame/mount loads
 
I was afraid this would turn into another " what kind of oil" type of thread. There will always be those with alternate opinions. I used to think that way about FOM,s too. Until I restored my station wagon, which came with them.

They were on the car a long time, including a trip across Canada and back to Oregon. The guy I bought it from said he had put 40K miles on the car since he bought it. When I removed the body, the frame was not only sagging at the mount area, but had twisted, as the weight from the engine bore down on the lower rail and forced it outward as the top rail caved inward. The inward turn resulted in the cowl sagging so bad the doors stuck in the jambs. As the engine sagged, the choke rod wore into the cowl hole and made the most annoying squeak when driven. That twisting would not be possible with original mounts. I agree the common sag occurs even with original mounts, but the frame on my car was worse than many original Ford motor-mounted frames I have seen.


Milton said:
I understand the x-member concept, but that is a lateral situation while sag is perpendicular to that, so my question still stands regarding FOMs and sag. Can you tell me the "problem" that is aggravated?

However, since the original mounts do create a rubber mounted x-member what is its purpose? There are three real (riveted) x-members in a model A frame, one at each axle and one centered between the other two. So, with three little 1/4" bolts through the frame, mounts, exterior plates and two rubber pads what is the gain of an additional x-member less than two feet away from the center x-member? In other words, what lateral forces are diminished with the use of this theoretical x-member design.

Geo. H
"I think the frames got bent when teen agers used them for jeeps back when they were worth twenty-five bucks."

I'll vouch for that, nothing like an off road experience in a Model A. :D
Click to expand...
 
"I was afraid this would turn into another " what kind of oil" type of thread. There will always be those with alternate opinions."

Pat,

The only kind of thread I want to turn this into, if possible, is one based in fact. I asked the question only to clarify statements I have heard and/or read in the past. It was once "generally believed" that the Earth was flat therefor I don't put a lot of creedence in these types of beliefs. This is in no way a challenge, nor an attempt to one up anyone, the questions I posed were simply meant to get to the facts or any supporting documentation that will settle the matter. As a result of this discussion I will contact my man, Sancho Panza, and ride off into the sunset on Rocinante in search of a factual answer to this question.
 
Milton said:
"I was afraid this would turn into another " what kind of oil" type of thread. There will always be those with alternate opinions."

Pat,

The only kind of thread I want to turn this into, if possible, is one based in fact. I asked the question only to clarify statements I have heard and/or read in the past. It was once "generally believed" that the Earth was flat therefor I don't put a lot of creedence in these types of beliefs. This is in no way a challenge, nor an attempt to one up anyone, the questions I posed were simply meant to get to the facts or any supporting documentation that will settle the matter. As a result of this discussion I will contact my man, Sancho Panza, and ride off into the sunset on Rocinante in search of a factual answer to this question.
Click to expand...

MILTON,yes indeed...evidence, not beliefs!
i still think that your logical position prevails over beliefs!!
sure some frames were abused , and sagged. but from what...abuse or lack of proper engineering, lack of preventative maintenance what???

what kind of severe trauma do any of you think could/would cause teeth to be knocked out of both the ring AND pinion in a model rear end? hard use/abuse?

well when i bought my junker '30 roadster, that is exactly the condition of its rear end! but when /after stripping to the frame, the frame was found to be in perfect condition..other than pitting. there was reason to believe that this car had never been stripped to the frame ...so was in original condition. no evidence of sag, even tho one of the original engine mounts was cracked! point is, after running this same frame for six years with FAM and a hot B...no evidence of sagging:D!
 
SSsssteamer said:
The frame was bent cold. Then straighten it cold and it will go right back to like it was before the bend. Putting heat to the frame could anneal the frame and make it softer and easier to bend where the heat was applied. Putting heat to the frame will straighten it only where the heat is applied. The actual bend covers a longer area than just the small heated area. Chain down the frame ends and jack up the sags to straighten again. When I was a kid on the farm, it was always fun to see how much air we could get with the old cars. We did bend a few frames. Puckered body panels, ill fitting doors and hoods, and broken motor mounts were the immediate results of our wild entertainment.
Click to expand...

Wow, ...interesting perspective. If you don't mind me asking, is this based on your personal experiences, --or just a hunch??


.
 
Thanks for all the responses. Prior to purchasing the truck it had been stored in a barn since 1957. I have restored the truck from the frame up. Did not notice any issues with the the frame after sandblasting at the time of restoration. Their is small kink in the lower frame rail about 5 inches in front of the motor mounts. Noticed the issue due to change in hood spacing between gas tank an radiator.
Bronco
 
sorry to have drifted off your original question: the small kink you refer to is probably the normal beginning of the narrowing of the frame rail. The rail thins out from just ahead of the motor mounts until it is just the frame horn. see pics

5611310701_44c57115e3_z.jpg
IMG_0992 by tiopato2000, on Flickr

5611894420_b95ca5cdd5_z.jpg
IMG_0993 by tiopato2000, on Flickr


Bronco said:
Thanks for all the responses. Prior to purchasing the truck it had been stored in a barn since 1957. I have restored the truck from the frame up. Did not notice any issues with the the frame after sandblasting at the time of restoration. Their is small kink in the lower frame rail about 5 inches in front of the motor mounts. Noticed the issue due to change in hood spacing between gas tank an radiator.
Bronco
Click to expand...
 
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