Reply
 
Thread Tools Search this Thread Display Modes
 
Old 01-15-2016, 08:29 AM   #15
Rivet Master
 
switz's Avatar

 
2014 31' Classic
2015 23' International
2013 25' FB International
Apache Junction , Arizona
Join Date: Sep 2012
Posts: 4,799
Images: 8
Our dynamic changes when the fresh water moves aft into the black and gray water tanks on the Classic. I find I have to drop the height of the jacks to 5" from 5.5". Initially we had a 6" setting, but after taking 175 pounds of battery and stainless steel enclosure weight off of the tongue weight and getting rid of the original water heater and the six gallon hot water storage (which was 80 pounds less weight just behind the street side wheel well), the dynamic changed.

We are still playing with the height of the jacks. If I get them too short, we get both slight oscillations and bounce.

We had more than the provided number of washers in the adjustable hitch head, but I may need to add some more, perhaps with a longer bolt for them to ride on.
__________________

__________________
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC

TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell

2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels
switz is offline   Reply With Quote
Old 01-15-2016, 05:05 PM   #16
Wise Elder
 
Jammer's Avatar
 
2010 30' Classic
Vintage Kin Owner
South of the river , Minnesota
Join Date: Dec 2009
Posts: 4,119
Quote:
Originally Posted by dznf0g View Post
On some pavements, it is what it is and you can't get rid of all of it.
Rich is correct.

Up-and-down (vertical) movement of the rear of the tow vehicle is not sway and cannot be controlled by changing the hitch around. This is not a problem unique to ProPride; all hitches do it.

The root cause is an undulating pavement surface. Usually the amplitude of the pavement changes is small enough that it isn't noticeable without a trailer. The physics of it has to do with the "normal mode" or resonant frequency of the combination of the tow vehicle rear springs and the weight on them.

If the rear shock absorbers in the tow vehicle have failed, that will make the movement much worse. If they are still good, it will help somewhat to replace them with heavy duty shocks, at the expense of an overall stiffer ride.

Front shocks can also help a little.

Reduced speed can help somewhat.
__________________

__________________
To learn to see below the surface, you must adjust your altitude
Jammer is offline   Reply With Quote
Old 01-16-2016, 07:39 AM   #17
Rivet Master
 
1996 25' Excella
Tillsonburg , Ontario
Join Date: Aug 2014
Posts: 787
Quote:
Originally Posted by cwf View Post
Oh how fast do you pull? I pull about 60.. Too fast you can develop an oscillation if roads undulate. I have had that in our 34'
Also our truck original shocks were incapable of decelerating. Had to slow under 45 to get it to stop.
Just ideas since we do not know your situation, operating speeds.. Etc.
I have had several situations where it was impossible to stop the porpoising and others where a change in speed settled things down somewhat.
The issue is partly spring rates in the truck and the ability of shocks, but I also believe the spacing in the road joints is a more important factor. The porpoising is due to a natural frequency in the total rig. Some roads simply match the distance between the TV wheels and the Trailer in a way that sets the whole rig into a natural bounce usually referred to as sympathetic frequency. Longer rigs like tractor trailers don't (usually) have the problem.

In my worst case it didn't matter how much I slowed down; sometimes speeding up actually improves it but it will always be there if the road conditions are right!
JCW
__________________
JCWDCW is offline   Reply With Quote
Old 01-16-2016, 08:59 AM   #18
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,408
Images: 5
Quote:
Originally Posted by JCWDCW View Post
I have had several situations where it was impossible to stop the porpoising and others where a change in speed settled things down somewhat.
The issue is partly spring rates in the truck and the ability of shocks, but I also believe the spacing in the road joints is a more important factor. The porpoising is due to a natural frequency in the total rig. Some roads simply match the distance between the TV wheels and the Trailer in a way that sets the whole rig into a natural bounce usually referred to as sympathetic frequency. Longer rigs like tractor trailers don't (usually) have the problem.

In my worst case it didn't matter how much I slowed down; sometimes speeding up actually improves it but it will always be there if the road conditions are right!
JCW
Yup
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is offline   Reply With Quote
Old 01-16-2016, 09:56 AM   #19
Rivet Master
 
dkottum's Avatar
 
2012 25' Flying Cloud
Battle Lake , Minnesota
Join Date: Jun 2009
Posts: 7,716
Could this be one of the reasons the Airstream Owners Manual cautions to never exceed 1,000 lbs hitch weight (similarly, amplifying any sway tendencies)?

Using their guidance of at least 10% of trailer weight, not to exceed 1,000 lbs, our hitch weight must be between 720 lbs and 1,000 lbs, for example.
__________________
Doug and Cheryl
2012 FC RB, Michelin 16, ProPride 1400
2016 Ram 1500 Laramie Crew Cab 4X4 Ecodiesel 3.92 axles

The Truth is More Important Than the Facts
dkottum is offline   Reply With Quote
Old 01-17-2016, 04:52 AM   #20
Rivet Master
 
switz's Avatar

 
2014 31' Classic
2015 23' International
2013 25' FB International
Apache Junction , Arizona
Join Date: Sep 2012
Posts: 4,799
Images: 8
We had a diesel Suburban in the mid 90s (it lived at the dealership due to exceptionally poor engine design) and were driving in Wyoming at the posted 80 mph with just two of us and some luggage in the car. The road was undulating and we were getting pounded by the suspension. Slowing to 72 mph, the frequency of the road and the long wheel base came into synch and the ride was smooth again.

That road and vehicle harmonic also comes into play when towing.
__________________
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC

TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell

2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels
switz is offline   Reply With Quote
Old 01-17-2016, 09:11 PM   #21
1 Rivet Member
 
2014 31' Classic
Hot Springs , Arkansas
Join Date: Jan 2016
Posts: 16
Thanks for the many replies. To answer one of the questions asked, we tow at 58-60 mph. The AS has the original D rated tires with 65 mph limits so we don't push it.

We hook up next Monday for a 130 mile drive to our next destination. We'll experiment with some of the suggestions, including taking measurements on the front wheel well and from the back of the WD bars to the ground. Thanks again.
__________________
Gigi1957 is offline   Reply With Quote
Old 01-17-2016, 11:00 PM   #22
cwf
Rivet Master
 
cwf's Avatar
 
1999 34' Excella
Currently Looking...
Hillsboro , Texas
Join Date: Feb 2013
Posts: 5,934
Images: 2
Quote:
Originally Posted by Gigi1957 View Post
Thanks for the many replies. To answer one of the questions asked, we tow at 58-60 mph. The AS has the original D rated tires with 65 mph limits so we don't push it.

We hook up next Monday for a 130 mile drive to our next destination. We'll experiment with some of the suggestions, including taking measurements on the front wheel well and from the back of the WD bars to the ground. Thanks again.
Also... Check from ground to the "belt line", bow and stern...
__________________

__________________
Peace and Blessings..
Channing
WBCCI# 30676
cwf is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pro Pride Hitch cpfdret Airstream Classifieds 0 11-05-2014 06:04 AM
Pro pride hitch questions gomotomoto Our Community 4 10-11-2014 12:09 PM
Pro-pride (Hensley) Hitch for sale Schilling Airstream Classifieds 0 06-06-2014 09:56 AM
Pro pride hitch/weight distribution question dkottum Hitches, Couplers & Balls 19 03-03-2010 10:42 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 07:54 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.