Sportsman 4: Checking the Frame for Straightness

The chassis has found its new home in the shop, comfortably placed on a dolly and jack stands.  It doesn’t look too bad on the painted concrete floor, but it certainly shows signs of its age.  The first step in this project will be disassembling the chassis to strip it down to its most essential components.  As it sits, this chassis could be something you found in a chicken coop in Washington State, buried in mud in a Louisiana barn, or even under an original pickup truck in New York.

American Bantam Frame

Once the frame is stripped bare, you can begin to imagine all of the forms it may someday take on.  Will it the backbone of a stock restoration?  Will it hold together a special?  Perhaps it will be pushed to the limits keeping together a pepped up custom?  So long as it is still straight and strong, its possibilities are nearly unlimited.

Properly supporting American Bantam Frame

Whatever your dreams and plans may be, you need to make sure that you are not only starting with the correct foundation but, more importantly, a true one.  Bantam chassis consist of a forged front crossmember, two hat channel steel side rails, a central steel K member, and a rear crossmember of one of various configurations.  Like a model T, these frames were built to flex a bit.  They have little in common with the chassis of standard cars built during the same period.  These chassis are meant to have a bit of a spring to them which you can really sense if you put a foot on each frame rail near the center and put all of your weight on them.  It will undoubtedly bow in the center.  While this motion is normal, you should make sure that your rails are not buckled, twisted, or otherwise out of line.  You should also make sure that your frame doesn’t show any signs of rot or heavy pitting.  If the frame is damaged, you may want to consider finding another.  Frames are fairly plentiful and as this is the basis of the whole project, you are better off starting out with the best.

There are no published specifications indicating what a “straight” bantam frame should exhibit. The first endeavor was to mount the frame on four corners with the two at either end being level and the positions symmetrical from left to right.  Using some strong and straight wood provided for a flat mounting area so I wouldn’t have to worry about my frame slipping off of the jack stand grips to skew my measurements.

Remember, lifting this frame is not a hard feat, it’s probably 75 lbs at best.  However, be careful when lifting and shifting it.  You may need to adjust it a few times as you shim the jack stands or wood to level them out.  Once they are level, you can start inspecting and measuring your chassis.

Amazingly, three of the four mounting points were positioned well for leveling the frame. The front drivers side stand required a shim for which a small piece of junk mail filled the part quite well. Once I determined the wood itself was level, I placed the frame on it at similar points on each side. The frame made perfect contact at each point and the levels appeared to indicate relative trueness of the frame. I’m sure there are better ways to do this which would allow for more accurate results, but this seems to work.

Once it appeared there there was no twisting of the frame, I decided to see if the frame was pinched at all. Seeing the slight bends on the rear cross-member let me to believe there may be some issues in this regard. After realizing how hard it would be to do this with a standard tape measure and only one set of hands, I devised a better system.

First, I marked the frame with respect to fixed features found on each side using a heavy duty crayon. I marked off two measuring points on each side on the rear of the frame and one set of marks on the front. I then stretched out each of two very cheap harbor freight measuring tapes to hold them down to the frame using equally cheep harbor freight welding magnets. The magnets managed to hold the tape taut, but did pull a little bit when I exerted too much effort on the tape.

Both of the diagonally strung tapes measured up at the same distance which really began quieting my fears that this frame may be bent. Finally, I took my very precise Lowes ruler and suspended it across the frame where the tapes intersected. Sure enough, they intersected at the center of the span at that portion of the frame.

Not pictured was my determination that the frame was straight along its span.  Using a straight edge, I checked both hat channel side rails.  Both rails were flush with the straight edge until the point where the chassis sweeps upward.  Combining the straight edge test with the flush alignment of the chassis to the level wood helped me establish that the frame was in decent shape.

I’m sure I may have done better with factory measurements for the frame and a fancy frame jig, but I am very satisfied with the results. For all intents and purposes, this frame is straight.  After all of this, I am ready to begin transforming this bare chassis into the Bantam Sportsman project.

For this project you may need:

Tape measure

Two Thin Tape Measures, at least 10′ long

Click here to see the auction for the Tape Measure

Jack Stands

Four Jack Stands – these will come in handy for the entire project

Click here to see the auction for the Jack Stands

level straight edge

A straight edge / bubble level – Probably a good thing to always have for other projects.

Click here to see the auction for the Straight Edge / Level

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