Acceptable frame square limits

[Daisy Mae]

Hoisted Daisy's body off the frame.

All body mounts are solid, and 5 of the six body/frame bolts were original size, but driver side rear had a slightly smaller diameter bolt. Could be an odd bolt replacement, but it kicked my spidey senses for a possible Uh-Oh.

Once off, I checked the frame for square, and she's off 5/16".
I don't see any signs of frame damage, and see no obvious curvature of the frame rails.

So, in the flexible world of Model T, what is the general consensus as to what is acceptable vs not? Is 5/16" significant for a Model T, or an acceptable limit and therefore why am I being anal over a car with slap it together tolerences and quit worrying?

[TXGOAT2]

Is the frame "diamonded" , or is one side shorter than the other? Measuring diagonally, it should be fairly easy to straighten the frame if the side rails are not bowed or sagged. The straighter, the better. Check for loose rivets or any other fasteners and correct as needed. A straight frame makes for an easy driving, easier riding, better looking car, and it will probably be easier to assemble, too. Might even go faster, use less gas, and get better tire mileage....

[Jerry VanOoteghem]

At a glance, that seems trivial. How did you measure the squareness to arrive at 5/16"? Without knowing your method, it's difficult to determine if 5/16" is significant or not.

[Daisy Mae]

Measured diagonally, tape end centered on front frame corner, and measured both at the far outer edge of the rear cross member, as well as outer edge of the frame rail tab riveted to top of cross member. Both readings the same variance.

The rails themselves were then measured entire length, both rails measure exactly the same, so no frame bowing, the frame is simply diamond.

Driver (left) side to rear (right) passenger side (for you Allan ) is the longest, which I figure means driver side is pushed rearward.

The frame appears tight, no loose rivets.

The most glaring item that is off is the driver/left side forward running board bracket is bent forward under no tension without the board attached, left side being a good inch longer than right. Will have to make some judicious tweaks on that arm.

[Jerry VanOoteghem]

I wouldn't worry about it. It's probably one of the better frames out there.

[Allan]

It'snot hard to remedy, so why not do so?
A carpenter"s
tool to check squareness is a simple length of light timber with a nail in one end. Park the nail in one corner and mark off the diagonal. The swap to the other side corner to check.
Allan from down under.

[TXGOAT2]

I'd straighten it. It shouldn't be difficult. If it's skewed, the car will dog track, since both axles will be at a slight angle to the car's center line. It may make fitting body parts more difficult, and it can set up strains in motor mounts and springs that can affect ride handling, and more. Pulling it a little past straight and bumping the corner joints with a big lead or brass hammer will get it straight.

[John kuehn]

Since it’s off the car I would try to straighten it. But it’s not off that much. If it’s square that’s a plus.

[Mike Silbert]

Maybe I overdo it but If I do frame work I aim for being off by 1/16" or less in error.
That is 1/16" or less in sag, straight, rack, square, length etc.
All the measurement points are at important locations like mounting points.
I assume that 1/16" could possibly be measurement error
If it is off in an area between the important point is is less concerning and only a cosmetic issue.

The Model T can take being off quite a bit but I prefer if I am getting out the tools and fixing it to make it better than just acceptable.
Time, loads, twisting, and driving will make the frame move around a whole lot, I want to start out in the middle of the range if possible.
If I straighten it, I want to have it so it fits together easily and looks nice.
Everything builds off the frame and it is difficult to make the car look good if the foundation is not right.

Others are sure to have a different opinion but if it were my frame and it was sitting there loose I would fix it.
Mike

[TXGOAT2]

Cars with sagged frames look tired. Cars with distorted frames never handle quite right. It may be difficult to get a top to fit really well on an open car with a mis-aligned frame.

[Dennis_Brown]

For straightening, can a simple method be used by using a carpenters square to see which side needs to be moved to square it up and then put a chain loop around the opposite corners and use a come a long between the loops to pull it back? Slack off the come a long and see if its square and if not pull it again. You might have to go slightly over square as it may spring back but I would only go in slight increments over square.
This may sound like a backwoods way of squaring it up but I believe Henry made the Model T so that even the backwoods people could work on them too.

[Daisy Mae]

Thanks everyone for the input/suggestions.
I'm looking for easy & cheap but effective.

[Daisy Mae]

Duplicate post

[Allan]

A carpenter's square has short sides and this relies on the cross members being in perfect order to get an accurate reading. Check the diagonals. If you do not have access to a porta power use a couple of lengths of chain and a turnbuckle to pull the longer diagonal back a bit. Go easy and do it in short steps

Allan from down under.

[jsaylor]

I would male sure its at least square at the engine mount holes. If your engine pan is straight, set it in and make sure the mounting holes line up.

[Ned L]

Keep in mind that if you have a 5/16 difference in the diagonal measurements, you need to “adjust” only 5/32 to have equal measurements.
As you correct the frame, when you reduce one diagonal measurement by 5/32 the other diagonal measurement will increase by 5/32.

[Jerry VanOoteghem]

Keep in mind that if you have a 5/16 difference in the diagonal measurements, you need to “adjust” only 5/32 to have equal measurements.
As you correct the frame, when you reduce one diagonal measurement by 5/32 the other diagonal measurement will increase by 5/32.

Great observation. I doubt whether this frame was ever better than this since it was made.

[Ned L]

And I should have added, that if you do choose to try to improve it, I would recommend working with just the diagonal dimensions, and not to try to use a framing square. This is off by such a small amount you will not be able to accurately see the error with a square.

Personally, I would call it good as is.

[speedytinc]

Thanks everyone for the input/suggestions.
I'm looking for easy & cheap but effective.

My first thought was to use a come along on the long diagonal side.
Maybe on the bottom side to resist adding a sag.
As mentioned, you only need move it 5/32"

[TXGOAT2]

A straight frame will avoid handling issues, needless strain on engine pan arms, and a number of other problems.