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Old 11-26-2012, 01:12 PM   #1051
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Yes. As I have mentioned several times before the resonant frequency of spring bars, ALL SPRING BARS HITCHES, is just about equal to that set up while traveling over a concrete slab highway at 60 mph.

It is almost impossible to conceive that the resonant frequency of the bushings could ever be met while driving. The lack of porpoising in this case is a freebee that is going to be very hard to argue against
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Old 11-26-2012, 01:30 PM   #1052
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Originally Posted by Sean Woodruff View Post
However, porpoising is a symptom of improper weight distribution. Without the front axle loaded enough there will be "bounce" in some combinations.

That said, some tow vehicles will not bounce with under 100% of the front axle load.
This calls for a 'Porpoising Forum Rally/Workshop' somewhere near MN-23 between Ogilvie & Mora MN (or I-90 between Beloit & Madison, WI). It would be a great way to tune up a lot of rigs.

I've heard this attribution before. It certainly may be true to some degree. Regardless how I modify my WD I cannot go on some tired poured concrete roads without shaking up the propane so bad that my stove won't light for a month. Just kidding... More elaboration is gooder -- maybe even its own thread.

Bob with a GMC Sierra 3/4 ton and Reese DualCam
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Old 11-26-2012, 01:37 PM   #1053
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Yes. As I have mentioned several times before the resonant frequency of spring bars, ALL SPRING BARS HITCHES, is just about equal to that set up while traveling over a concrete slab highway at 60 mph.
I can remove it with a couple cranks of a ratchet wrench at any speed.

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It is almost impossible to conceive that the resonant frequency of the bushings could ever be met while driving. The lack of porpoising in this case is a freebee that is going to be very hard to argue against
The bounce is more a function of the weight distributed, or lack thereof, that the resonant frequency of bars or bushings.


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Old 11-26-2012, 01:41 PM   #1054
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The amount of weight (whatever that is), directed to the front axles should be an amount related to optimum handling and performance. I will continue to rely on the experience of seasoned towing professionals to advise.
Well, that depends on your definition of "seasoned". Is that a person who sells hitches and sets them up for other users, or would that be someone who has actually used several various types of hitches, with different trailers and tow vehicles over a period of some thirty+ years?
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Old 11-26-2012, 02:08 PM   #1055
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This calls for a 'Porpoising Forum Rally/Workshop' somewhere near MN-23 between Ogilvie & Mora MN (or I-90 between Beloit & Madison, WI). It would be a great way to tune up a lot of rigs.

I've heard this attribution before. It certainly may be true to some degree. Regardless how I modify my WD I cannot go on some tired poured concrete roads without shaking up the propane so bad that my stove won't light for a month. Just kidding... More elaboration is gooder -- maybe even its own thread.

Bob with a GMC Sierra 3/4 ton and Reese DualCam
I'm good for that next season, live nearby, and have the Andersen installed. Seat-of-the pants comparison would be useful.

We couldn't rid the proposing from our Equal-I-Zer (and they could be brutal) with two different-sized new Airstreams no matter how I adjusted it. Replaced that dog with the Andersen. In 3700 miles from MN to Wash DC to AZ, with plenty of side trips, we have not experienced it.

doug k
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Old 11-26-2012, 02:13 PM   #1056
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Originally Posted by Sean Woodruff View Post
The bounce is more a function of the weight distributed, or lack thereof, that the resonant frequency of bars or bushings.
-
I am sorry but this is about as far off base as you can get on this one. While resonant frequency can be changed to some small degree by the weight applied to the system it is a function of the length and material used in the spring bars. The Andersen does not have spring bars. The resonant frequency of the Andersen hitch will be the load and material of the bushings. Urethane has long been used as a damping material against many forms of vibration because it's resonant frequency is so far off scale.

Just think with the Andersen you could travel route #10 in La. and not have to stop at the dentist afterwards or pick your refrigerator door off the floor.

And the ride would be so smooth you could see those Bees Flying by.
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Old 11-26-2012, 02:19 PM   #1057
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I am not sure I can take any validity from your graph when 3 of the components of the formula are assumed and one, chain tension, you are just placing an arbitrary value on.
The essence of the graph are the nine data points which are calculated from values reported by users. The three assumed components to which you refer have nothing to do with the placement of the data points.

The two theoretical curves were included for reference. They simply show what the FALR vs Tongue weight relationship would be for chain tensions of 1000# and 2000#.
One of the "assumed" parameters, the Lever Arm, actually is a measured value reported by Bruce H. I referred to it as "asssumed" because I do not have independent verification of the value.
Typical values of "BOH" might range from 4.5' to 5.5' versus the 5' which I used for producing the example curves.
The theoretical calculation is relatively insensitive to "TTL". A 100% variation in this value changes the result by about 8%.

As for the "correct" value for FALR, that's open to much discussion. People express strong opinions, and then they change their minds.
For example, in this post -- http://www.airforums.com/forums/f238...ml#post1154357 -- you stated:

"What you are attempting to accomplish is to at least return the weight to the front axle that the trailer reduced by the cantilevering effect of have applied the trailer weight behind the rear axle. This insures the steering system is in a normal configuration and improve sway control that would be reduced by the reduced weight on the front axle."

I take that to mean you previously believed the FALR should be at least 100%.
Now you seem to be saying that 40% is okay.

Ron
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Old 11-26-2012, 02:25 PM   #1058
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Quote:
Originally Posted by Sean Woodruff View Post
I can remove it with a couple cranks of a ratchet wrench at any speed.

The bounce is more a function of the weight distributed, or lack thereof, that the resonant frequency of bars or bushings.

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Quote:
Originally Posted by HowieE View Post
I am sorry but this is about as far off base as you can get on this one. While resonant frequency can be changed to some small degree by the weight applied to the system it is a function of the length and material used in the spring bars. The Andersen does not have spring bars. The resonant frequency of the Andersen hitch will be the load and material of the bushings. Urethane has long been used as a damping material against many forms of vibration because it's resonant frequency is so far off scale.

So you're saying I can distribute very little weight and just replace spring bars with Urethane and I will not get any bounce? The bounce IS NOT a function of the weight distributed?

Interesting...
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Old 11-26-2012, 02:31 PM   #1059
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Ron

Actually if you go back a bit further in my writings, several years worth, you will see that I have written on the Reese systems often. I wrote that one wanted the front axle to drop in the range of a 40/60 ratio to the rear axle, depending on the springs set of the TV. That was based on a need to get the rig in a drivable condition mostly attempting to reduce the Porpoising so characteristic with a Spring Bar system.

Have I changed my mind? No not with respect to a Reese or other spring bar systems. But YES having set up the Andersen originally as per above and now having used it enough to realized I do not have to go that far to get the functions I am looking for from the Andersen.

The slight reduction that I currently have on the front axle is well within the range of design load for the Ford Excursion. Again 120 lbs on a 4220 axle is lost in the second decimal place.

The published beat frequency for a Bee wings is from 190 to 200 beat per second. That is a 5% range. You will note that if he changes frequency from day to day he can still fly. There is room for deviation hear also.
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Old 11-26-2012, 02:50 PM   #1060
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So you're saying I can distribute very little weight and just replace spring bars with Urethane and I will not get any bounce? The bounce IS NOT a function of the weight distributed?

Interesting...
No Sean. Spring Bars are loaded perpendicular to the center line and the bushings are loaded along the center line so a direct replacement is not possible. Design changes are required and they have been done.
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Old 11-26-2012, 04:40 PM   #1061
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Can you get Anderson to chip in for the testing?

I'll chip in with my product and money.


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Hi, how and what kind of testing would you do? And would it be more accurate than the totally unbalanced spring bar test done by another vender? [comparing the flexability of a 800 lb bar to a 1,000 lb bar]
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Old 11-26-2012, 04:53 PM   #1062
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Actually if you go back a bit further in my writings, several years worth, you will see that I have written on the Reese systems often. I wrote that one wanted the front axle to drop in the range of a 40/60 ratio to the rear axle, depending on the springs set of the TV. That was based on a need to get the rig in a drivable condition mostly attempting to reduce the Porpoising so characteristic with a Spring Bar system.
Okay, I did a search of your posts using the keywords "40/60" and "60/40".

I found 24 posts over six years in which you told people they should adjust their WDH so that load was added to both the front and rear axles reative to the unhitched values. The recurring emphasis was on steering control. I found no mention of porposing in these 24 posts.

You repeatedly stated you wanted a 40/60 ratio of front-end drop (load increase) to rear-end drop (load increase).

Now, the primary emphasis for your combination apparently is on porposing rather than on steering control. And, you believe that a ratio of -29/+129 is okay instead of your previously-preferred +40/+60.

I really don't care what you prefer to do with your rig. But, are you now advising other Andersen owners that load transfer is not important?

Ron
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Old 11-26-2012, 06:20 PM   #1063
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Which numbers were you using for me Ron, the ones for the Hensley or the Andersen? I posted both. I'm not sure I'm following you showing the 50%. Or maybe I just do not understand your theory. The Andersen was within acceptable range of less than 10% difference and handled very good.
I have not taken the rig to the scales with my Ford but I'll try to get there this week sometime. I still had a lot of adjustment room with the Chevy so I'll work on the Ford to get as close to 100% to the unhitched front axle as I can and post those numbers. In the past, I was attempting to get within 10 % of front and back axles. Did that and did not do more adjusting.
With the Hensley, I probably could not get it to 100% unless I changed and put stiffer bars on it. I was at 1,000 pounds. REDNAX had posted he also had the same problem with his but I never saw a post where he corrected it. I think he was out about 200 lbs. Jump in if you want to Red.
The lack of porpoising is real. With the Andersen, it is almost gone.
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Quote:
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For those who are interested in load transfer data and theory --

Front Axle Load Restoration (FALR) is chosen as the indicator of load transfer effectiveness.
For measured front-axle loads, FALR is defined as the amount of load added by application of WD
divided by the amount of load removed by tongue weight (with NO WD applied).
For measured front-axle heights, FALR is defined as the front-end lowering due to application of WD
divided by the front-end rise due to tongue weight (with NO WD applied) .
When the front end is observed to be returned to the unhitched height, the FALR is taken to be 100%.

The data indicate FALR=100% can easily be achieved for low tongue weights.
However, for tongue weights in excess of 1000#, it is not clear that FALR=100% can be achieved.

The curves labeled "FALR Theory" are calculated from: FALR = 100*CT*2*LA*(1+BOH/TTL)/TW/BOH
where
CT = chain tension in #/chain
LA = lever arm from ball center to chain in ft (assumed to be 6.5"/12 per Bruce H.)
BOH = ball overhang in ft (assumed to be 5')
TW = tongue weight in lbs
TTL = distance from ball to mid-point between axles (assumed to vary from 12' for TW=400# to 20' for TW=1200#)

Contributors of data can be identifed by their TW and achieved FALR in the following table:

TW - FALR - Load/Height - Contributor - DataSource

400---100%----hgt.----SteveH------Airforums.com
400----91%----load----Bruce H.-----Lanceowners.com, RV.net, Airforums.com
900----75%----hgt.----gallifrey------RV.net
600----54%----load----hbillsmith-----RV.net
800----50%----load----airheadsrus---Airforums.com
1250---45%----load----housedad-----RV.net
960----43%----load----renojack------RV.net
600----43%----hgt.----zues----------Airforums.com
670----40%----load----HowieE-------Airforums.com

Ron
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Old 11-26-2012, 07:33 PM   #1064
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Which numbers were you using for me Ron, the ones for the Hensley or the Andersen? I posted both. I'm not sure I'm following you showing the 50%. Or maybe I just do not understand your theory. The Andersen was within acceptable range of less than 10% difference and handled very good.
Joe, I took the unhitched front axle load of 3360# from Post #1031.
The hitched, with no WD, was taken from Post #1034 -- 2900# adjusted up to 3000# as you suggested.
The hitched, with WD, also was taken from Post # 1034 -- 3180#.

The load added via the WDH was calculated as 3180-3000 = 180#.
The load removed by tongue weight without WD was 3360-3000 = 360#.
The Front Axle Load Restoration was calculated as 180/360 = 50%.

I would be happy to add your new scale results to the chart when you have them.

Ron
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