Motor Stay Rods (anti-chatter rods)

[DavidG]

Bubsyouruncle,

The starting point goes back to the initial design of the front motor mount brackets, one-piece front motor insulators, and steady (stay, anti-chatter) rods at the beginning of '32 V8 vehicle production. Those three components provided no 'wiggle' room when an engine was installed in a chassis as the insulators bolted to un-slotted holes in the front cross member and the brackets had un-slotted holes for the bolts that threaded into the insulators. Compounding that resulting requirement for a very precise relationship of the front cross member to the center cross member, the steady rods attached to the front of the center cross member which likely resulted in a gap between the front of the shoulder on the rod and the back of where the rods attached to the engine block on one side or the other. Hence the need for shims. (In the case of the earliest '32 V8s the rods did not attach directly to the bell housing of the engine block, but rather to separate brackets which attached to flats on either side of the engine block bell housing. But that is not germane except that it increased the number of components that had to be held to close tolerances.) I've attached photos of those early insulators, motor mount brackets, and front cross member which will give you a sense of how everything had to line up perfectly in order to install the engine/transmission assembly in the chassis.

It was a dumb design and that became clear immediately once vehicle production commenced and all three components were re-designed to provide for some flexibility for the inevitable slightly-out-of-spec relationships between the front and center cross members, the hole locations in the front cross member for the insulators, the length of the engine/transmission assembly, the location of the cast-in holes for steady rods on the engine block, and the various dimensions of the front motor mount brackets.

Apart from the new multi-piece front insulators and redesigned front cross members, the most obvious change was to increase the size of the holes for the insulator bolts in the front motor mount brackets. Those holes became slotted and were widened as well. The instructions for installing engine transmission assemblies were revised to specify that the insulator bolts were not touch the walls of the holes in the front motor mount brackets. With that goal, once again it was inevitable that one or even both engine steady rods might not seat up against the shoulder of the hole(s) for it (them) on the engine block bell housing once the steady rods were securely attached to the center cross member and hence a need for a shim or shims. (At the same time of the other changes the steady rod and center cross member designs were changed so that the rods passed through the cross member making engine/transmission installation infinitely easier, but the new instructions made it clear that the rods must first be firmly attached to the center cross member before finalizing the attachments of the threaded end of rods on the engine block bell housing.

In other words, the relationship of the threaded ends of the steady rods to the engine block bell housing was dictated by the fit of the motor mount brackets to the insulators and the fit of the insulators to the front cross member. In that sense perhaps distortion is too strong a word for this purpose.

My apologies for going off the deep end on this topic.

[Bubsyouruncle]

Good Heavens! You stay up late answering questions.

Once again you provide a wonderfully clear observation and description of the situation.

As a longtime practicing mechanical design engineer I think I understand the problem after your description.

In essence, with the '32, the basic front to back locating surface was/is the front face of the K-member. Transmission and engine tolerances accumulated forward from there and the driveshaft and rear axle back from there. So you get a stack of +/- tolerances from the transmission housing and the block before you get to the surface at the back of the block where the steady rods seat.

What a mess! Suspect that the "silo effect" was in charge during design time.

And it is obvious that relocating the steady rods from in front of the K-member to behind the K-member made life on the line much easier, although it did introduce the thickness of the crossmember as an additional tolerance. Having to slip those two rods into place at the same time you were lining up the transmission with the drive shaft must have been aweful. Unless they put the rods on the block before they put the engine in the car. And then if the rods were too long nothing would fit properly.

Assembly - my guess:

After the engine was correctly placed and tied in front and back the steady rods would be inserted into the holes in crossmember and block and it would then be determined whether shims were needed either between the block and the mushroom on the steady rod or between the flange of the rod and the crossmember.

[HenryFord]

Does anyone know the length of the the 4 cyl. 46-6044 anti-chatter rods? I have a 33 sedan delivery without them.

[DavidG]

If you don't obtain that dimension beforehand, I can provide it in the week of the 17th.

[DavidG]

Bubsyouruncle,

I lived the nightmare of that assembly challenge as I recently installed one of those earliest engine/transmission assemblies with the earliest version of the steady rods, steady rods, motor mount brackets, and insulators in a very, very early phaeton. Like a station wagon restoration, one of those per lifetime is more than enough.