i figured out that there are two studs because this is basically a "u-joint'. the steering shaft is on a slightly different angle than the steering box input shaft. so you need a u-joint to connect the two. if they used 4 bolts to hold the two couplers together, they could not achieve this result, so they use two studs. this creates a "sliding" joint at 90 degrees to the fixed joint [the two bolts]. ta da..... a cheap u-joint! any thoughts? also, i found a diagram of the correct coupler assembly in my [yoe guessed it] assembly manual. thanks to all the guys that responded with pictures etc
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Re: rag joint insight
No doubt that is one reason, Werner but the other reason is that with a body-on-frame, there will be some flexing between the body and the frame that has to be accommodated. The rag joint also serves as a vibration isolator since anything coming from the frame would be transmitted to the wheel if the connection were not isolated. Though, there are plenty of unibody cars made prior to 1967 that used a solid shaft out of the steering box straight to the wheel but I feel these examples can't be directly compared to the body-on-frame construction. -
Re: rag joint insight
gerry, you said it better than i did, but the mal-alignment of the steering shaft relative to the box input shaft [while thay are both rotating], whether due to body flex or due to mis-alignment while stationary [like my car] is why you need a u-joint. the only reason i raised the question is because i could not figure out why they are using studs alternating with bolts, instead of just using four bolts. the stud "sliding" into and out of the cut out space in the coupler is what creates the u-joint effect. of course the thick rubber acts as an absorber of minor vibration.
finally, i made some bushings this morning to equalize the size of the 4 holes in the rubber disc with the diameter of the bolt/stud that goes into each hole. i am hoping to minimize the tendency for the holes to become oval because the holes are quite a bit bigger than the bolts/studs that go through them. i'see if it helps, but it sounds good in theory. should keep the joint tight.Comment
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Re: rag joint insight
The "studs" and open slots on the opposing flange are there as a fail-safe system; if the carcass portion of the joint fails, the studs and slots will prevent total steering loss. The primary purpose of the "rag joint" is to isolate chassis vibration from the steering column/wheel.Comment
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Re: rag joint insight
john, this time i cannot agree. i can't believe that this joint is primarily a vibraton reducer. i know that to some extent it will do this [although that hard pieced of rubber tightly clamped between two metal plates ought to transmit plenty of vibration], but the primary purpose must be as a u-joint. as for the studs and safety, no way. i looked carefully at that, and considered the same thing you did, but if it were primarily a safety feature then the upper free end of the stud should have somewhat of a "t" shape to prevent the upper coupler from riding over the free end of the stud with hard turning [remember, you said that the rag would be in failure mode]. what i am saying is that the stud is too short to be any sort of a safety feature. and if it were, then why were 2 rivets and not 2 studs used on the original rag joint? hm?
i am still not sure why they actually use a stud when it really seems that a bolt would do the trick of letting this thing serve as a u-joint and as a vibration damper. i looked at the stud and asked myself: how would it change anything if someone were to cut off the portion of the stud that protrudes freely through the space in the upper coupler? doesn't seem it would change anything. any thoughts?Comment
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Re: rag joint insight
I respectfully disagree with you----John's explanation is right on!
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Re: rag joint insight
Werner -
Believe me, after 37 years in OEM Engineering and Manufacturing, the first 21 of which were in Chevrolet (including the Corvette Group in '67-'68), and having spent most of my career in assembly plants, I'm intimately familiar with the function, design, component manufacturing, test programs, safety requirements, and mandatory assembly and process control procedures related to "rag joints". You'll note in the A.I.M. that there is a spec for engagement distance from the base of the safety studs to the adjacent surface of the other flange with the open slot in it, to ensure that the finished assembly has the studs protruding the required distance through the safety slots. It's there as a vibration isolator; if you replace the "rag" with an identical solid metal disc, you'll find out how much of a "tuning fork" a steering column and instrument panel can become when excited by transmitted steering, suspension, and chassis vibration frequencies. It's also the ground path for the horn relay circuit (the copper strap riveted to the "rag" attachments).Comment
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Re: rag joint insight
John,
Do you know why GM used two different size studs on the rag assembly in 1964? Do other years also use two different size studs. I'm sure there is a reason and I can't figure out what it is. I'm just curious. It doesn't appear that it is an issue of indexing the assembly.Comment
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Re: rag joint insight
that's fine, but why don't you share with us "why". i pointed out my reasons why i disagree; why don't you do the same. i'd love to hear your reasons, as i don't consider myself close minded and i love to learn from the insights of others. let us know, please.Comment
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Twenty Years ago I had the privilege
of listening to a discussion between James Gaylord and Zora Arkus Duntov about these rag joints where Jim told Zora "You see, I was right, that joint was the way to eliminate vibration.". To which Zora responded "Yes, you were right about that, but very wrong on many other things.".
Vibration.Comment
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Re: rag joint insight
Werner, As I said in my first post, I agreed with John's first post----I didn't think it needed any clarification! With that said, John's second post has put some more clarification to your quire---do you understand it now?
John was mostly in the Plant environment, and I was always in Engineering, therefore, when it comes to an assembly situation I and usually count on John's insight to be right on.
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Re: Twenty Years ago I had the privilege
FELLOWS- there is obviously no question in my mind, nor ought there be in anyone's, that using a rubber disc [as opposed to metal] will improve vibration damping. it doesn't take years and years of whatever experience to figure that one out. the fact that the rag joint is a simple u-joint is also obvious [because the two shafts rotate on different longitudinal axes], and if i recall, later models of gm cars actually went to a u-joint [but i may be wrong on that point].
however, the real question i asked has not been answered, despite all of the posts: why 2 different size studs?
we all know the original rag joint used rivets to hold the rag to the lower coupler; these rivets are replaced by two uneven studs [instead of simple bolts] in all kits i have seen;
a stud is simply a bolt with a long round smooth head; it looks to my eye that the studs would do everything they are supposed to do without these heads; why are the heads different sizes anyway; etc. john hasn't answered this except to say that this is a "safety feature". yes, the assembly manual points out the distance that the stud should "protrude" into the gap in the upper coupler, and it sure isn't much.
but, that distance is in a "healthy joint". who really knows what that distance would be in an unhealthy joint [ie deteriorated or torn rubber etc] john says it is a safety feature, inplying that it will allow one to steer the car with a failed joint. i hope he's kidding about that , because i don't want to trust my steering to this design. at the least there ought to be a "t" shape to the top of the stud so that the upper coupler will "hook" the stud; but there isn't. then there is the problem of the uneven sizes. only the fatter one would be pushed, so this is really a dreadful safety feature, if it is a safety feature at all, which i doubt. also, none of what he says explains why there are two different size studs. location cannot possibly be a problem in this simple system of two bolts and two studs, so why the different sizes? that was the question, and if duntov didn't answer it, maybe someone else knows.
finally, if the disc is ONLY a vibration damper, as john claims and duntov conceded, then why are the two couplers not made with flat surfaces. it would be less machining. no, the gaps are there to accept the different planes of rotation as the joint functions as a u-joint. if you were ONLY concerned about vibration, you could easily put a flat joint somewhere in the steering column, without the fancy shaped couplers and studs etc. IMHOComment
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Re: rag joint insight
Ford rag joints were made the same way for the same reasons, for what that's worth to the discussion.Comment
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Re: Twenty Years ago I had the privilege
Because "Bubba" is everywhere, including assembly plants, service departments, independent garages, and owners' back yards, this critical safety system is designed so every single part from the steering wheel hub to the pitman arm is designed with idiot-proof assembly features so it's correctly indexed radially from top to bottom and can't be incorrectly assembled without significant effort (in current politically-correct engineering terminology, the design is "error-proofed", and the assembly process is "mistake-proofed"). The steering wheel hub has a "blind spline" to match against an index mark and blind spline on the end of the steering shaft, the lower end of the steering shaft is indexed to the upper flange of the rag joint, the lower flange of the rag joint is indexed to the steering gear input shaft, and the pitman arm is blind-spline indexed to a matching blind spline on the pitman shaft from the steering gear. Within the rag joint assembly, there are two different diameter threaded studs with nuts on them (one of the nuts is a "special", with the same hex size as the standard one on the other smaller-diameter threaded stud so the assembly plant can use the same power tool on both nuts), and the holes for those two threaded studs in the opposing part to which they attach are also different diameters to match the studs. This makes it virtually impossible to index the two halves of the joint assembly 180 degrees off - that's also why the two riveted safety studs are different diameters, along with their corresponding slots in the opposing flange; if you try to join the two halves of the joint 180 degrees out of position, the threaded studs won't go through the holes, and the larger of the two riveted safety studs won't fit in the narrow slot of its opposing flange.
The safety studs and slots weren't intended to drive the car around on - they're intended to signal a warning of excessive wear or incipient failure via unusual noise and vibration through the steering column from the resulting metal-to-metal contact, and to provide enough steering to get the car off the road without total loss of steering control in the event of total failure of the "carcass" component. About 100 million cars and trucks have been built with exactly this same design for decades.Comment
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Re: Twenty Years ago I had the privilege
John, I couldn't have said it better!!!!!!!!!!!!!!!!!!!! That's why I waited for your response-----Werner, does that help?
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