MTFCA Forum

Few folks are reconstructing a Model T.

How many are checking the Frame Alignment?

I was cleaning out years of collected stuff and the book "The Restoration of Antique and Classic Cars," 1957, Wheatley and Morgan dropped on the floor opening to page 30. Chapter on the frame and checking it before a rebuild.

For the benefit of the group I am including a copy of their suggestion for making certain the frame is square.

With the Model T Frame being a simple rectangle it should be straight forward to check for squareness.

I have found that most Model T frames have a sag where the crankcase ears bear on them. That's easy to check (on a bare frame) using a string along the upper inside edge.

Mike speaking on the sag by the ears. What are your thoughts on boxing that section? I’ve got a early suicide door coupe that has a sag so bad the doors will not close. I’ve been mulling it over & first time I’ve asked. Best John

The usual place of sag is where the pan ears are attached. This is especially on the right side facing front. This sag will also cause the engine to drop on that side pushing the ball joints for wishbone and universal joint out of alignment. This will cause the steering to pull to one side while driving.
The same sag will cause problems with hood alignment and the fit of doors. So that is one important thing to address. Another would be frame straightness from front to back on both sides. This could be altered if the car has been hit on the side. The third alignment is diagonal. If you measure from one point at the rear of the frame to a point diagonal at the front. The measurement should be same from both sides. All these changes can be straightened by fastening down the frame and jacking up for a sag, or pushing diagonally in the opposite direction for diagonal misalignment. Final minor adjustments can be made by placing shims on body to frame. Start with the radiator to cowl and shim up whichever side might sag until you get the hood to fit. Then adjust the doors by raising or lowering to make the door shut (note) be sure hinges are not sagging before making door frame adjustments. Finally adjust until both sides open and close correctly.
Norm

Thanks Norman I’m going to lift the body and do just that but as I asked Mike would boxing that section make it less likely to sag again?

Some methods others have used
Sag
http://www.mtfca.com/discus/messages/80257/86146.html
http://www.mtfca.com/discus/messages/33 ... 1364403935
Front Cross
member http://www.mtfca.com/discus/messages/33 ... 1367904024
Others
? http://www.mtfca.com/discus/messages/118802/123360.html
? http://www.mtfca.com/discus/messages/70 ... 1495179236

Boxing the frame would certainly strengthen it, but it would destroy the flexibility designed into it. Boxing a portion of the frame might cause cracking issues at the ends of the boxed section. Best to carefully straighten it to spec, then check all rivits for tightness. With a closed car, it might be advantageous to adjust the frame to have a VERY slight upward bow in both rails. You need a dead level surface for measuring, straightening, and assembling and adjusting the car. I'd stay away from using heat.

I agree with Pat on stress risks with boxing a portion of the frame, but don't share his concern regarding heat.

a guy with the right knowledge, armed with a torch and wet cloth can do wonders shrinking stretched metal back to it's previously formed shape and length. It's done on sheet metal and frames all the time. If you think you're going to damage the frame's metallurgy, I encourage you to take a swipe on one with a new file and report back on how tough it is. They're not the same as a '26 axle, that's for sure, and spot heating isn't going to harm a thing.

ON the coupe, have you considered placing shims under the center body mounting bolts to compensate for the frame droop?

Shims under the body at points of sag will help the doors This will work with slight sag, but if it sags very much the engine will drop on one side and throw the driveline and wheels out of alignment. Norm

I will say this for the last time as it appears to fall on deaf ears.., but here I go!

The upper bolts of the rear engine oil pan bolts are a "peg". Meaning you tighten them, then loosen by about 1 1/2 turns or so. Tightening is not to be confused with an 1/8 turn more to snap off. The side bolts going into the wooden blocks need another metal surface to ride on other than the pan ears, ie, 3/8" fender washers times 2 per side normally work fine. I use Vaseline on all surfaces, sightly longer grade 5 bolts and nylon inserted lock nuts. Tighten side pan bolts and then loosen 2 full turns!

Remember folks, the frame MUST flex, this is a trinity, radius design, using the frame as parallel control beams! You MUST have good, properly installed shackles, leaf springs that MUST slide on each other, etc.

Straightening a bent frame without fixing the real problem is a bigger problem. Bandaid for a gun shot wound to the head! Remember.., these frames had the holes punched prior to forming, then slightly tempered. Once they bend, they are weak. Fix the core of the problem!

Enough of the SOAPBOX,

Hank

Do you mean like this --
--
Did you mean like this

And the two parallel frame rails (Beams) are twisted by the forces of the double trinity. You get an "A"!

There are band-aids and there are fixes. The fix involves straightening the rails and checking the frame for square. If it is square, diagonal measurements from each corner will be the same. Straight rails should be obvious obvious. Straightening them can be a challenge, involving sash cramps, timber spacers, a hydraulic jack and chains, and an extra pair of hands. The sag occurs over time, with no heat. I prefer not to use heat when correcting it.

Allan from down under.

this is how I measured my frame looks straight to me
Passenger side along rail passenger side at location of oil pan ear no sag driver side along rail driver side at location of oil pan ear no sag passenger side extreme rear to driver side extreme front 104 5/8 " extreme driver side rear to extreme passenger front 104 5/8"
did I miss any measurements?

To be complete I think you need to measure if the frame is square. That is is the distance between the rails at the cross members correct to the drawing above and then are the diagonal measurements from cross member to cross member,as described by others, the same.

A square frame:

Education and learning are based on mistakes and repetition.

Square frame: AH = BG.

That picture in the above post is not a T frame. The side rails on a T are straight.
Norm

The non-model T frame is just used to show where to measure the diagonal lines. If the rails are of equal length then to square up everything (square, trapezoid, rectangle, etc you could measure the angles between the rails and cross members. However, a slight degree of difference can be multiplied at the other end of a long run. The easy way to square things up is to get the diagonal measures equal. So the example below shows an irregular trapezoid squared up and how the same applies to a rectangle (Model T)

Woodworkers use a simple tool to check frames when gluing up, a piece of wood with a nail driven through one end. Put the nail up into one corner, and mark the wood at the opposite corner. Switch to the corresponding points on the other side and check to see if the mark is in the same place. They can correct out -of-square by angling the sash cramps used to hold things together while the glue sets. The measuring technique works just as well on a T frame.

Allan from down under.

Reading my post I forgot two pictures. I did measure the frame diagonally.

TRDxB2 wrote: ↑

Wed Aug 03, 2022 7:53 pm

Do you mean like this
440301.jpg
--
--
Did you mean like this

It is absolutely INCREDIBLE that these are able to flex the way that they do. Vehicles now couldn't dream of doing that. If they did there would be damage to them.

JTT3 -- I tried calling you, but apparently your number has changed. I agree with the others that boxing a T frame would not be a good idea, for the reasons given above. And I agree that over-correcting the sag a bit in the upward direction is a good idea. Use heat and cooling to try to shrink the lower part of the frame rail in that area. Otherwise, when you add the weight of the engine and body, it will sag again.