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Old 10-21-2010, 06:56 PM   #15
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We may be overlooking one thing about rotating castings, they may machine rough and look off center, but in fact they are balanced.


I "borrowed" these random pic's from a national supplier just to illustrate the factory balancing technique. Notice the added lug at 12 O'clock on the first drum and the semi-circle at 3 O'clock on the second drum? the first is a balance weight just like our car tires except this is welded on, permantly and the second removed some material .

This is why I asked for a full shot of the drum. IIRC, drums can be balanced like this or they may remove a section from a sacrifical flange on the inboard side of the drum.

Rotors may have a roll pin weight tapped into the cooling fins to correct the balance.

Castings are rough by nature and cosmetic satisfaction may not be a print specification, but our TV's and AS don't have eyes, they are looking for a correctly machined and functioning part, if the casting is a bit fat on one side, the balance weight gets larger on the opposite side.

I can't confirm if your drum was balanced, these are just automotive samples.

One other balancing requirement, you must use the same reference for balancing as the part will be as installed. For example, to balance from the ID of a drum has nothing to do with the mounting reference on the hub.
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Old 10-22-2010, 02:46 AM   #16
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Quote:
Originally Posted by GCinSC2 View Post
We may be overlooking one thing about rotating castings, they may machine rough and look off center, but in fact they are balanced.


I "borrowed" these random pic's from a national supplier just to illustrate the factory balancing technique. Notice the added lug at 12 O'clock on the first drum and the semi-circle at 3 O'clock on the second drum? the first is a balance weight just like our car tires except this is welded on, permantly and the second removed some material .

This is why I asked for a full shot of the drum. IIRC, drums can be balanced like this or they may remove a section from a sacrifical flange on the inboard side of the drum.

Rotors may have a roll pin weight tapped into the cooling fins to correct the balance.

Castings are rough by nature and cosmetic satisfaction may not be a print specification, but our TV's and AS don't have eyes, they are looking for a correctly machined and functioning part, if the casting is a bit fat on one side, the balance weight gets larger on the opposite side.

I can't confirm if your drum was balanced, these are just automotive samples.

One other balancing requirement, you must use the same reference for balancing as the part will be as installed. For example, to balance from the ID of a drum has nothing to do with the mounting reference on the hub.
Motor vehicles have been balancing their drums for decades, but trailer drums aren't. Mine have no signs of added weight or removed weight for balancing purposes.
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Old 10-22-2010, 07:34 AM   #17
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In my original post, the drum pictured was definitely out of balance. No matter which way I rotated it on the spindle, it would return to rest at exactly the same location, heavy side down. That is a clear indication that it is out of balance otherwise it would come to rest in random orientations. (The drum was spinning freely with no interference from brake pads.)

My point in posting the photos was to illustrate the need to balance the drum/wheel/tire combination because some folks seem to believe their drums were manufactured to the same standards as automotive parts. That doesn't appear to be true for the vintage Airstreams as Andy and several others have confirmed.

I guess that even if I owned a modern Airstream, I would take a close look at the drums to see if any attempt had been made to balance them....
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Old 10-22-2010, 10:01 PM   #18
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My point in posting the photos was to illustrate the need to balance the drum/wheel/tire combination because some folks seem to believe their drums were manufactured to the same standards as automotive parts. That doesn't appear to be true for the vintage Airstreams as Andy and several others have confirmed.

I guess that even if I owned a modern Airstream, I would take a close look at the drums to see if any attempt had been made to balance them....
Hi, mine is a 2005 model and the drums are not balanced. That's why I installed Centramatics.
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Old 10-23-2010, 06:59 AM   #19
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driftless,

I cannot argue with the gravity balance observation that you describe, that would get my attention also, I hope.

Robert,

This is another notch in my AS learning belt, thanks. I deal with rotating castings for engines and BALANCE IS CRITICAL! for correct performance. Still doesn't make a lot of sense that a highline trailer mfg'r would'nt spec balancing of the brake drum or rotors.

Thanks,

Gary
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Old 10-23-2010, 10:10 AM   #20
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driftless,

I cannot argue with the gravity balance observation that you describe, that would get my attention also, I hope.

Robert,

This is another notch in my AS learning belt, thanks. I deal with rotating castings for engines and BALANCE IS CRITICAL! for correct performance. Still doesn't make a lot of sense that a highline trailer mfg'r would'nt spec balancing of the brake drum or rotors.

Thanks,

Gary
Gary.

Airstream "could" spec the top of the line for everything it uses. There are 2 questions though.

First, what would be at the top as well as at the bottom of the list.

Second, who could afford one, as the cost would soar through the heavens.

Many manufacturers of thousands of products, still believe that the owner, has certain responsibilities too.

Balancing running gear is one of them.

Tires are not balanced either, yet millions are sold each year.

I basically agree with you, but..........

Andy
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Old 10-23-2010, 11:08 AM   #21
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I suppose if I replaced my hubs as often as I replaced the tires, and if the hub dealer balanced the hubs the way my tire dealer balances my tires, then I could buy that argument.

The reason Airstream doesn't balance the hubs is simply cost, and the fact that most customers don't notice because they don't ride in the trailer.

It's not a matter of being at the top or bottom of some list. That argument is just a distraction and an abstraction.
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Old 10-24-2010, 10:03 AM   #22
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it's called Value Engineering

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The reason Airstream doesn't balance the hubs is simply cost, and the fact that most customers don't notice because they don't ride in the trailer.

It's not a matter of being at the top or bottom of some list. That argument is just a distraction and an abstraction.
As a professional engineer for the past 40 years, I have a good understanding of the design process for projects and products. An important part of the design process for an engineered system such as the body/frame/running gear of an Airstream is what is known as Value Engineering.

From Wikipedia: Value engineering (VE) is a systematic method to improve the "value" of goods or products and services by using an examination of function. Value, as defined, is the ratio of function to cost. Value can therefore be increased by either improving the function or reducing the cost. It is a primary tenet of value engineering that basic functions be preserved and not be reduced as a consequence of pursuing value improvements. For more information go to : Value engineering - Wikipedia, the free encyclopedia

So, hubs are certainly included on a list of all the components of the system. And somewhere along the line someone has determined that the additional cost of balancing the hubs does not increase the function of the entire system to a point that it would result in an equivalent increase in the value of the entire system.

As consumers we need to recognize that the products we purchase are designed and built to a standard that will allow the manufacturer to produce and sell the most units at a price which is acceptable to the most buyers. If you don't like the quality of a manufacturer's product at their price, find an alternative.

As far as hubs go on older Airstream trailers, you can do your own bit of value engineering. Leave them alone and have them balanced with the wheels/tires, take them to a machinist and have them balanced, or buy a set of centra-matics.

Yes, the philosophy of manufacturing is full of abstractions. But I don't see Andy's response as a distraction, just a dose of reality.
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Old 10-24-2010, 10:27 AM   #23
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i find it odd that a quality product would not balance the drums or at least have them conform to a reasonable standard. if using part of the product can cause harm to the rest of the product, someone wasn't thinking. it might be ok for a park model but certainly not for a travel trailer.

the only other thought i had on that drum was that it was machined incorrectly and was mounted off center.
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Old 10-24-2010, 11:29 AM   #24
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driftless,

Your value engineering explanation is a good explanation of the ways things are sometimes vs. the way they could be and it adds the element of value vs. payback to the equation.

Frankly, I would have thought them to be balanced, my automotive experience said that would be a natural, but this is not automotive in the pure sense, so I'll watch a bit more closely.

Andy,
If AS put it in writing that an owner should balance the running gear, or offer it as an option, that would help us understand this a bit. I have read a lot in my manuals and AF.

AF,
I just checked my 2007 AS Owners Manual and found the following:

Pg. B-1: DISC BRAKES..."Many automobile manufacturers and others have used this type of rotor installation for many years" It might be possible to infer that AS is calling their brake system Automotive, but not using Trailer Service as the primary reference. And the brake drum or rotor is a major element in this discussion/equation.

Pg. D-5: "All tire and wheel assemblies are balanced at the factory. Be sure to rebalance the tire and wheel assemblies each time a tire is changed."

I'm not trying to start a flame fest, I'm a 1st year owner learning A LOT by my estimation from our new to us AS, lots of reading, forum time, questioning and field learning in 4 outings YTD and taking my experience of many years of vehicle ownership and hands on repair, any of you Dodge 5.9L CTD guys will know what this is: Fixed KDP on the 12V at home w/new gear case, not JB Weld, so I'm not a novice wrench, just not pro in the 9-5 sense.

Someone is always a new guy and needs and appreciates your help.

More to learn, thanks to all.
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Old 10-24-2010, 12:22 PM   #25
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Quote:
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driftless,

Your value engineering explanation is a good explanation of the ways things are sometimes vs. the way they could be and it adds the element of value vs. payback to the equation.

Frankly, I would have thought them to be balanced, my automotive experience said that would be a natural, but this is not automotive in the pure sense, so I'll watch a bit more closely.

Andy,
If AS put it in writing that an owner should balance the running gear, or offer it as an option, that would help us understand this a bit. I have read a lot in my manuals and AF.

AF,
I just checked my 2007 AS Owners Manual and found the following:

D-5: "All tire and wheel assemblies are balanced at the factory. Be sure to rebalance the tire and wheel assemblies each time a tire is changed."

I'm not trying to start a flame fest, I'm a 1st year owner learning A LOT by my estimation from our new to us AS, lots of reading, forum time, questioning and field learning in 4 outings YTD and taking my experience of many years of vehicle ownership and hands on repair, any of you Dodge 5.9L CTD guys will know what this is: Fixed KDP on the 12V at home w/new gear case, not JB Weld, so I'm not a novice wrench, just not pro in the 9-5 sense.

Someone is always a new guy and needs and appreciates your help.

More to learn, thanks to all.
Everyone has an opinion, even Airstream.

To balance running gear each time a tire is changed, is a huge joke. Running gear should be balanced every 10,000 miles, if not sooner.

Of course adding automatic balancing systems to the running gear, of the trailer, is a huge advantage, that even car or truck owners don't use on their tow vehicles.

Andy
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Old 10-24-2010, 12:39 PM   #26
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GCinSC2,

It's all about learning new things and applying the knowledge we already have from our vocation or profession. I think you made a very reasonable assumption based on your personal experience.

I expected there would be a lot to learn when we bought the AS. And, like you, I'm a relative newcomer and trying to take it all in. These forums are a great resource. I couldn't even begin to thank all of the members who have contributed to my understanding of all things AS (or at least those things that I've looked into).

I guess you might say, "we're all in the same boat...except it is a Land Yacht."
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