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I found this today in the public records. It is VERY relevant to the swaged aluminum driveshafts used in our SSRs.

Quote:
United States Patent 5643093
Aluminum driveshaft having reduced diameter end portion
Issued on July 1, 1997
Abstract

A driveshaft includes a center portion having a larger diameter, an end portion having a reduced diameter, and a diameter reducing portion positioned between the center and end portions. The reduced diameter end portion of the driveshaft is secured to a reduced diameter tube yoke. This facilitates the introduction of tooling during assembly of a universal joint. The driveshaft is formed by a method which involves first heat treating the driveshaft to a relatively soft temper, then swaging the end portion of the driveshaft, and then heat treating the driveshaft again to a relatively hard temper. In more detail, a driveshaft is provided having a predetermined first diameter, the driveshaft being heat treated to achieve a relatively soft temper so as to possess a desired elongation factor. This allows the end portion of the driveshaft to be swaged to reduce the diameter thereof to a second predetermined diameter. After swaging, the driveshaft is heat treated again to achieve a relatively hard temper to meet the strength requirements for use.
Claims


What is claimed is:

1. A drive line assembly comprising:

a driveshaft robe formed from a metallic material and including a homogeneous diameter reducing portion having a substantially uniform wall thickness, said diameter reducing portion including an axially extending cylindrical first end extending from said driveshaft tube, said diameter reducing portion further including an axially extending cylindrical second end, said axially extending cylindrical first end of said diameter reducing portion defining a first diameter, said axially extending cylindrical second end of said diameter reducing portion defining a second diameter, said first diameter being larger than said second diameter; and

a tube yoke formed from a metallic material and including an axially extending cylindrical end portion having a substantially uniform wall thickness which is co-axial with and permanently fixed to said axially extending cylindrical second end portion of said diameter reducing portion of said driveshaft tube, said tube yoke further including a pair of opposed lug ears extending from said end portion and having respective orifices formed therethrough.

2. The drive line assembly defined in claim 1 wherein said driveshaft tube is formed from an aluminum alloy.

3. The drive line assembly defined in claim 1 wherein said tube yoke is formed from an aluminum alloy.

4. The drive line assembly defined in claim 1 wherein said driveshaft tube and said tube yoke are both formed from an aluminum alloy.

5. The drive line assembly defined in claim 1 wherein said diameter reducing portion of said driveshaft tube is welded to said tube yoke.

6. The drive line assembly defined in claim 1 wherein said first diameter is about five inches and said second diameter is about four inches.

7. The drive line assembly defined in claim 1 further including a universal joint assembly connected with said tube yoke.
Description


BACKGROUND OF THE INVENTION

This invention relates in general to drive train assemblies for transferring rotational power in vehicles. In particular, this invention relates to an improved structure for an aluminum driveshaft tube for transmitting rotational power from an engine to an axle assembly in a vehicle.

In most land vehicles in use today, a drive train assembly is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical vehicular drive train assembly includes a hollow cylindrical driveshaft tube. A first universal joint is connected between the output shaft of the engine/transmission assembly and the driveshaft tube, while a second universal joint is connected between the driveshaft tube and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of misalignment between the rotational axes of these three shafts.

It is known that when any mechanical body is rotated about an axis, a natural resonant frequency is defined thereby. This natural resonant frequency is an inherent characteristic of the mechanical body and is based upon many factors, including its composition, size, and shape. When the mechanical body is rotated at a speed which is at or near its natural resonant frequency, a relatively large amount of vibration can occur. In the context of a vehicular driveshaft tube, the natural resonant frequency is often referred to as the "critical speed" thereof. Thus, when a driveshaft tube is rotated at or near its critical speed, it can begin to vibrate excessively. Such vibration can, at a minimum, generate undesirable noise in the vehicle during operation. More seriously, this vibration can cause excessive stresses and rapid failure of not only the driveshaft tube, but the other components of the drive train assembly connected thereto. Accordingly, an important consideration in the design and manufacture of driveshaft tubes and other drive train assembly structures is that they not be operated at or near their critical speeds in normal operation.

Thus, the critical speed for a driveshaft tube is a function of, among other things, the nature of the material used to form the driveshaft tube. Generally speaking, the lighter the material used to form the driveshaft, the lower the critical speed. Traditionally, vehicular driveshaft tubes have been formed from steel alloys. Steel alloys have been found to be acceptable materials not only because they possesses sufficient strength to transmit the rotational loads which are normally encountered during use, but also because they are relatively heavy and stiff materials. As a result, the critical speed of steel alloy driveshaft tubes is usually sufficiently high that it is not encountered during normal operation of the vehicle. Unfortunately, because they are relatively heavy materials, steel alloys contribute an undesirable amount to the overall weight of the vehicle. To address this, driveshaft tubes have more recently been formed from lighter weight alternative materials, such as aluminum alloys. Aluminum alloys have been found to be desirable for use in vehicular driveshaft tubes because they are much lighter than steel alloys, yet possess sufficient strength to transmit the rotational loads therethrough. Unfortunately, for this same reason of lighter weight, the critical speed of an aluminum alloy driveshaft tube is usually much lower than the critical speed of a comparably sized steel alloy driveshaft tube. The critical speeds of typical aluminum alloy driveshaft tubes have been found to be undesirably close to the normal operating speeds of the vehicle than comparable steel alloy driveshaft tubes.

As mentioned above, the critical speed for a driveshaft tube is also a function of the size and shape of the driveshaft tube. Generally speaking, the longer the driveshaft tube is in length and the smaller it is in diameter, the lower the critical speed. The use of aluminum alloys has allowed the replacement of traditional two-piece steel alloy driveshaft tubes with newer one-piece aluminum alloy driveshaft tubes. The newer one-piece driveshaft tubes are preferable to the traditional two-piece steel alloy driveshaft tubes because fewer parts are required. However, because they are longer in length, one-piece aluminum alloy driveshaft tubes have a lower critical speed than a comparably sized two-piece steel alloy driveshaft tubes, undesirably close to the normal operating speeds of the vehicle than comparable steel alloy driveshaft tubes.

Attempts have been made to alter the critical speed of one-piece aluminum alloy driveshaft tubes to facilitate their use in vehicles. For example, it is known that the critical speed of an aluminum alloy driveshaft can be increased by covering it with a coating of a high strength material, such as a resin matrix reinforced with graphite fibers. Though effective, the use of such a covering undesirably increases manufacturing costs. It would be advantageous, therefore, to provide an improved structure for a driveshaft tube which would enable the use of lighter weight aluminum alloys, yet would not require the use of relative expensive reinforcing coatings to raise the critical speed thereof above the normal operating speed of the vehicle.

SUMMARY OF THE INVENTION

This invention relates to an improved structure for a vehicular driveshaft tube which enables the use of lighter weight aluminum alloys, yet which has a critical speed which is sufficiently high as to not be encountered during normal use of the vehicle. A new driveshaft has now been developed which permits the use of a larger diameter driveshaft while still allowing the requisite access for the tooling needed to assemble the universal joints. By using a larger diameter driveshaft, the driveshaft can be formed from an aluminum alloy and yet not require an expensive reinforcing coating. The increase in the driveshaft diameter will increase the critical speed to a commercially acceptable level. In order to enable the use of a larger diameter driveshaft while still allowing the requisite access for the tooling to put together the universal joints, there is a diameter reduction which provides a conversion from the larger diameter driveshaft to a reduced diameter tube yoke. This invention provides this diameter reduction by forming a driveshaft with a center portion having a larger diameter and an end portion having a reduced diameter. A diameter reducing portion of the driveshaft is positioned between the center portion and the end portion. The reduced diameter end portion of the driveshaft is secured to the reduced diameter tube yoke. This facilitates the introduction of tooling to the lug bolts during assembly of the universal joint. The driveshaft of the invention is formed by a method which involves first heat treating the driveshaft to a relatively soft temper, then swaging the end portion of the driveshaft to reduce the diameter thereof, and then heat treating the driveshaft again to a relatively hard temper. In more detail, a driveshaft is provided having a predetermined first diameter, the driveshaft being heat treated to achieve a relatively soft temper so as to possess a desired elongation factor. This allows the end portion of the driveshaft to be swaged to reduce the diameter thereof to a second predetermined diameter. After the swaging operation, the driveshaft is heat treated again (referred to as "aging") to achieve a relatively hard temper to meet the strength requirements for use.

end quote

Jim G
 

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Driveshaft

Jim,
Does this explain everything?
My Automatic does in fact "whine" at lower acceleration under cold conditions.
No big deal after warming up. Can't hear it after warm up at all.
 

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Discussion Starter #3
Mine also is much more notable when outside temperature is cold. Also, the sound almost disppears when the driveline gets hot (12 miles or more at 70 mph or more).

I was told this afternoon that GM is working on a replacement driveshaft with cardboard lining inside to attentuate noise, but now that the Lansing plant is being closed, and the SSR might be discontinued, work on that might stop.

My source also suggested trying even multiple "rubber bands" (not literally office supply rubber bands of course, but you get the idea) wrapped around the EXTERIOR of the shaft as a trial to see if they dampen the vibration frequency just enough to make a difference. Maybe a rubber shrinkwrap sleeve of some sort?

While this sounds stupid, I have been told by multiple automtoive truck people that many commercial trucks have COATED driveshafts to eliminate or dampen vibration and noise, right from the factory. These are the coatings mentioned in the above patent application.

The key issues wth either coatings or bands are:

1. Perfect balance
2. Durability under road conditions

Jim G
 

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...

duraliner ... that spray on, brush on pick up box liner ?
 

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The aluminum drive shaft is very desirable due to the low weight and less parasitic loss. The aluminum driveshafts have been used by GM since the 1998 Z28 and everyone has always complained about the tink. The good side to the shaft is the low weight with less parasitic loss do to less rotational mass. The only better driveshaft would be a carbon fiber one but they tend to be a little pricey.

Here is a company that builds carbon fiber drive shafts where you get the benefit of the lighter shaft like the aluminum but no noise.

http://www.acpt.com/
 

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JimGnitecki said:
My source also suggested trying even multiple "rubber bands" (not literally office supply rubber bands of course, but you get the idea) wrapped around the EXTERIOR of the shaft as a trial to see if they dampen the vibration frequency just enough to make a difference. Maybe a rubber shrinkwrap sleeve of some sort?
Jim G
An Ace Bandage perhaps? :lol

Edit: Or maybe you could unspool a couple of golf balls. :thumbs
 

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JimGnitecki said:
Mine also is much more notable when outside temperature is cold. Also, the sound almost disppears when the driveline gets hot (12 miles or more at 70 mph or more).

I was told this afternoon that GM is working on a replacement driveshaft with cardboard lining inside to attentuate noise, but now that the Lansing plant is being closed, and the SSR might be discontinued, work on that might stop.

My source also suggested trying even multiple "rubber bands" (not literally office supply rubber bands of course, but you get the idea) wrapped around the EXTERIOR of the shaft as a trial to see if they dampen the vibration frequency just enough to make a difference. Maybe a rubber shrinkwrap sleeve of some sort?

While this sounds stupid, I have been told by multiple automtoive truck people that many commercial trucks have COATED driveshafts to eliminate or dampen vibration and noise, right from the factory. These are the coatings mentioned in the above patent application.

The key issues wth either coatings or bands are:

1. Perfect balance
2. Durability under road conditions

Jim G
I wonder if drilling a small hole (or 2 or 3) in the shaft and spraying in some expanding foam insulation would do the trick?

Roger
 

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I have know a few that drilled the holes in the center of the shaft behind the universals and sprayed the expanding foam into it. i would definitely have it checked for balance no matter what method you try. The large rubber bands also work and when made for that purpose they will not throw the balance off either.
 

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2005SSR6Speed said:
I have know a few that drilled the holes in the center of the shaft behind the universals and sprayed the expanding foam into it. i would definitely have it checked for balance no matter what method you try. The large rubber bands also work and when made for that purpose they will not throw the balance off either.

Any feedback from them??? Did it do any good?

Roger
 

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Discussion Starter #11
2005SSR6speed: I didn't realize that the rubber bands were an already established solution for this problem. I7ve never looked under anyone's car to check out their driveshaft! :)

Where do you get the appropriate rubber bands?

How many do you normally use (or is it completely trial and error)?

Jim G
 

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I have seen them used at the driveshaft place I have used for years. It is meant to stop the harmonics only. The bands are about 1/2"-1" wide that I have seen. You should be able to get them at a custom driveshaft shop. The shop I use is real old school, the last driveshaft they made for me it took about 3 hours to balance before it was perfect. They just dont build aluminum shafts, only steel, I have never heard of one of their shaft breaking though.
 

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Has anyone tried wrapping the driveshaft in a spiral fashion with a fiberglass or monafilament line? This type of wrap is usually covered with an epoxy or resin to keep the wrap in place and protect it some. This is used on thin wall or aluminum pressure vessels to increase pressure limits. I think it would also muffle the "tink" to an acceptable level.

Whaddaya think Jim?

Mike
 

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2005SSR6speed: Thanks! I will check with a local driveshaft shop and possibly do some experimentation.

Mike in AZ: Your idea would work IF you can apply the material EVENLY enough to keep the shaft BALANCED. I don't know how easy or hard that would be. The people that do the winding might not know either, as their typical wrapped object (pressure tank or fishing rod) does not normally rotate at high speed! :)

Jim G
 

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You are right Jim. Balance is critical, but if a thin fiber wrap was applied and then spray coated, the amount of induced imbalance should be minimal. Naturally, you would leave the ends clear for balance weights. I am only suggesting wrap on the main portion of the shaft. It could even be a loose wrap, as long as the ends were secured and the coating applied.

Not rocket science, just a little acoustic damping.

Where can we get a driveshaft to try this on? Maybe the carbon fiber driveshaft manufacturer would like to take this on.......

Mike
 
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