Is the frame straight enough?

E

Ed in Maine

Well-known member
I just got the body off the frame and dropped a straight edge on top of the frame in the area of the rear engine mount. The engine is still installed. It is clearly down in this area but only 1/16 in. on the pass. and the driver's sides. Other areas are flat. Can I ignore this minor sag? Ed
 
I place a 1/8" drill on top of the frame and stretch a string. You'll probably have more than a 1/16". Frame effects body mount, hood, door fit. you can take some up with shims. but then the gap between the body and rb splash aprons is effected. how much is acceptable is up to you..
 
Ed in Maine said:
I just got the body off the frame and dropped a straight edge on top of the frame in the area of the rear engine mount. The engine is still installed. It is clearly down in this area but only 1/16 in. on the pass. and the driver's sides. Other areas are flat. Can I ignore this minor sag? Ed
Click to expand...
Any sag is to much, it will give you fits when you try to line up the hood with the body. Like a house you need to start out with a good foundation.
 
George has a valid point to presently try to obtain zero sag .

At mid span of the two (2) supporting shallow, steel chassis channels, if one were to add the concentrated load of two (2) full grown passengers, the additional body weight occurring at the latch side of both doors & a full tank of gas, a battery plus tools & jacks under the seat, it all adds up to where one could expect more mid span deflection in excess of 1/16".
 
I'm too lazy to post "the works" again but I use fishing line over the entire length of the frame. "The area" is misleading depending on the specific size of that area. My read from your description is the sag is BIG.

Straighten it with the engine in and you will fare much better then those that do the bare frame.
 
There are perhaps hundreds of ways to check Model A frame straightness.

Here is one method borrowed by thousands of 20th century vintage carpenters, vintage brick masons, steel workers, etc., etc., throughout the World:

1. Obtain a piece of 1 x 4 pine or poplar (S4S), surfaced 4 sides, & cut it into three (3) adjacent pieces, each about 4" long. (At this point, if one has any doubt, one can verify with a micrometer that the thickness of all three (3) pieces of 1 x 4 are within 0.001").

2. Place two (2) pieces of 1 x 4 on the level top of the Models A steel chassis frame, one (1) at front, & one (1) at rearf the frame.

3. Securely fasten a "nylon" string to either the front or rear of the frame.

4. Pull & very tightly extend this string on the top center of the front & rear 1 x 4.

5. When this string is plucked, it should sound like a musical string instrument. After tightening same, securely fasten the string on the opposite end of the frame.

6. Using the 3rd 1 x 4 as a thickness gauge, place it on top of the steel chassis frame at several locations, adjacent to the tightened string, approximately midways between the front & rear 1 x 4.

7. With this 3rd 1 x 4 gauge, one can clearly see that when this 1 x 4 passes under the tightened string & barely touches this string, this side of the frame is dead level.

6. Repeat 1 -7 on other side of frame.
 
while you are at it. I also pull diagonals, and a line through the center of the holes in the front and rear cross members to check the frame for racking..
 
Thank you all for your excellent suggestions. I will look at it closer today. I have read the earlier posts on straightening methods. Ed
 
Last but not least:

If you ever thought that "one day" it would be a good idea to paint the frame so it looks nice from under the vehicle, "NOW" is the time to paint it right after the frame is straight.
 
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