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Old 01-12-2011, 04:13 PM   #161
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Old 01-12-2011, 05:36 PM   #162
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Quote:
Originally Posted by Dave Park View Post
I am not trying to court controversy. I am attempting to confirm your findings.

Due to the lack of information on how the tests were conducted, I or anyone else are unable to repeat your tests and produce comparison data, even if we were inclined to.

That makes your data unverifiable and unsupportable.

That's why I asked the questions - to clarify the method used and to rule out any potential problems with your protocol. Without those answers, you can't even say, "controlled tests" because no-one beside you knows what the controls were.

Answering everyone's questions simply removes uncertainty about your 'data' and allows ALL of us to have more confidence in it.
Hey Dave, could you please call some tire manufactures and unload this thinking on them about their ST tires and do us ALL a favoure?
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Old 01-12-2011, 05:45 PM   #163
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Hi All, Please keep a cool head while posting...

Weight distribution threads seem to bring out all lot of emotion.

Please be nice!
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Old 01-12-2011, 07:17 PM   #164
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First class work Andy, that had to be a lot of work and expensive..........

thanks
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Old 01-12-2011, 07:44 PM   #165
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Its obvious he has a love for airstreams and has devoted a great part of his life to them. So when he tells you to balance the running gear, he isnt trying to sell you centramatics, he doesnt want you to hurt your airstream......
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Old 01-12-2011, 11:23 PM   #166
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Very interesting data, Andy - thank you for collecting this.

As predicted, all the bars displayed linear load-displacement curves... save one. I'm curious if there were any experimental issues with the Reese 1000# tapered bars, as they displayed more deflection at high loads than the Equalizer 1000# bar - a result not predicted by beam theory and practice. The Reese 800# bar, which (presumably) has a very similar profile to the Reese 1000# bars, displays linear results to within measurement precision.

Note for a moment the very high loads produced by 1.5" deflection of the Equalizer 1000# bar. When beginning to climb a hill, the relatively angle between the TV and the Airstream will produce many thousands of lbs of extra load on the A-frame and hitch assembly.

The stiff bars are a design compromise needed to secure sufficient weight transfer force available with the limited bar deflection distance between unloaded and properly tensioned positions.

Thanks again, Andy.

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Old 01-13-2011, 09:13 AM   #167
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Ok, I'll take a stab at this and try and see if there are any real world take aways for us relative to approach angle hitch bar flexing.

DISCLAIMER: This is a simi-mathmatically based SWAG analysis FROUGHT with variables!!!! So, with that in mind, take your potshots with BETTER math. This is the best I could come up with while trying to recall a lot of advanced math I haven't used much in 30 years. My head started to explode, then I realized, with all the variables, reasonable approximations would suffice.

Since spring bar flexing is a direct function of the change in angle between AS frame and TV frame, some of these variables are:
1) WB of TV
2) Distance from ball coupler to center of AS axle(s)
3) Distance of overhang from rear axle to ball on TV
4) Compressability of TV and AS suspension
5) Tongue weight (component of base static bar flex)
6) Sprung load in TV (component of base static bar flex)

Using my AS and TV here are some numbers:
(This scenerio assumes NO front TV, no AS suspension compression and no rear TV suspension lifting, so should RESEMBLE a worst case scenerio)

TV WB = 135"
TV + hitch overhang = 59.7"
Coupler to center of AS axles = 223.4"
Spring bar effective length = 30"

Worst case, hitch drags ground with a 20" rise of front wheels over my TV WB with a 8.9" drop at hitch. Again this assumes NO suspension flexing! But still, it is an aggressive approach which would result in about 4.5" of spring bar flex.

HERE'S A BIG SWAG.

4.5" of flex is unrealistic, I believe, in the real world because of the effect of the bars to flatten out the change in angle between the TV and AS due to suspension extension and compression. (Here enters the discussion of 1/2 vs 3/4 vs 1 ton IMHO, as well as the tongue weight and load on rear axle of TV)

I SWAG that we would expect to see 3" - 3.5" of flex in our driving when approaching step entry angles.

ANOTHER SWAG!!!!

It is necessary to extrapolate (read, "guess", with some predictability) the extension of the chart lines to get to some of the anticipatd data!!!!! (scary in and of itself!)
Like Bart, I am not understanding the last few data points for the REESE 1000#er. (yes Bart, although I still can't reconcile in my noggin the linear function of the tapered bars.....the data don't lie, and I concede!)

Because of that odd trend on the REESE 1000#er, I really don't even trust my SWAG (and that's too bad, as that is the setup I would most like to be comfortable with, data wise)

SO!, at 3" - 3.5" of flex, I THINK this:

Hitch Force exerted on tongue (approx)

REESE 800# tapered 1900 - 2100#
REESE 1000# tapered 1900 - 2000# (?????? odd curve)
REESE 1000# round 1600 - 1800#
Equal-i-zer 1000# 2800 - 3200#
EAZ Lift 1700 - 2000#

Ok, a lot more to discuss and this is just a STARTING POINT for meaningful DISCUSSION, please.

How much is too much on various AS frames?

Andy, The REESE 100# tapered results seem odd. Is there a way to validate that set of data? Maybe with a couple of different sets of bars?

Ok, all you brainiacs out there, do I lose the Equalizer 100#er and go with a REESE 800# tapered, or 1000# tapered with sway control?

No, I'm not going to go with Hensley or Propride. I've got nothing against them and appreciate them, but FOR ME, I don't see the cost/benefit analysis working. I am very comfortable with a PROPERLY set up conventional hitch with sway control.
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Old 01-14-2011, 08:55 PM   #168
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Thanks

Your work is appreciated Andy.
Thank you,
Robert
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Old 01-14-2011, 09:05 PM   #169
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Your work is appreciated Andy.
Thank you,
Robert
Thank you.

Andy
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Old 01-14-2011, 09:32 PM   #170
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This works for chain based hitches that are more or less static - does it hold true for ProPride or Hensleys where the bars are more dialed in to raise the vehicle, thus even with 1,000 pound bars you may only be using 700 lbs of force to level the vehicle?
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Old 01-15-2011, 07:27 AM   #171
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This works for chain based hitches that are more or less static - does it hold true for ProPride or Hensleys where the bars are more dialed in to raise the vehicle, thus even with 1,000 pound bars you may only be using 700 lbs of force to level the vehicle?
We, obviously, don't have data for those setups, but the principles are the same. But do the springs behave more like an equalizer or something else. We don't know. My concern is not so much driving down the road as it is hitting those entry/exit driveway aprons and really flexing the bars. You can see on the graph how dramatically the forces climb.

I know Andy states that heavy bars transmit a huge amount of shock while driving over expansion joints, patches, etc. but I think more of the shock is transmitted through the ball and coupler, since this is a "solid" connection under not only the tongue weight, but also pressure exerted by the spring bars.....and there is the relationship of bar stiffness and shock transmission. BUT, say there is 1400# of force on the ball (TW + clamping force). How much does it matter if that force is applied by a 600# bar or a 1000# bar. Certainly, the 600# bar will have more flexibility, but does that make a dramatic difference in shock transmission through the ball? I don't know, but I think it is not as big a deal as some think. I am in the camp that believes rivet snaps etc. are the result of excessive torques and twists from stiff bars and traversing larger undulations in pavement....or especially unimproved roads.
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Old 01-15-2011, 07:27 AM   #172
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This works for chain based hitches that are more or less static - does it hold true for ProPride or Hensleys where the bars are more dialed in to raise the vehicle, thus even with 1,000 pound bars you may only be using 700 lbs of force to level the vehicle?
Good question.

We did not test those brands.

Perhaps some others might invest some time and money to do it.

We tested the most commonly used brands and ratings.

Andy
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Old 01-15-2011, 10:50 AM   #173
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Andy,

I really want to thank you for your continued support and participation in supporting the Airstream members here on our forums!

I believe your posts, studies and years spent in the insurance industry have not only educated many of us, but more importantly, you continue to spark conversation and discussions that keep us all on our toes!
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Old 01-15-2011, 11:06 AM   #174
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Andy,

I really want to thank you for your continued support and participation in supporting the Airstream members here on our forums!

I believe your posts, studies and years spent in the insurance industry have not only educated many of us, but more importantly, you continue to spark conversation and discussions that keep us all on our toes!
I think John that the large majority of us feel the same way and your post says it a lot better than I could have put it. We may not always agree with results regardless of who posts them, but it is more information for us to ingest and assimilate for our own use. Andy continues to support the forums, events, and shares his knowledge. It is appreciated.
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Old 08-05-2011, 08:33 AM   #175
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Smile Thanks for the help.

I appreciate the work by Andy and the comments. Monday I pick up my new 2008 Safari SE 27FB which I will tow with a 2011 Ford F250 Diesel. The owner is including a Reese Dual Cam with 1200 lb bars. Thanks to the information on this and other threads I'm switching to 800 lb bars and having the Airstream dealer near the soon to be prior owner (Colonial) look over and adjust everything.

These forums are a great source of information for wanabees and newbies. I've been a member for almost a year and read the portal almost every day. The many discussions have helped me in both selecting and evaluating my new acquisition as well as making my wife and I excited we will next week be joining the Airstream community.
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