Reply
 
Thread Tools Search this Thread Display Modes
 
Old 12-13-2013, 09:51 PM   #155
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Thanks Ron. I found those diagrams in a couple places and kinf of figured they were not jiving with your explanation a few hours ago. I imagined from your explanation that there would be an ellipse or circle trace, and so it is very interesting to see your second diagram! Once you see it projected that way, it all makes perfect sense. I've learned a lot today- it's a good day!
__________________

__________________
mstephens is offline   Reply With Quote
Old 12-13-2013, 10:17 PM   #156
Rivet Master
 
dkottum's Avatar
 
2012 25' Flying Cloud
Battle Lake , Minnesota
Join Date: Jun 2009
Posts: 7,716
Quote:
Originally Posted by Ron Gratz View Post
Certainly, as far as the 4-bar bump is concerned -- a pivot point projection hitch can provide some surprises of a type not encountered with a conventional hitch. However, the likelihood of a bump can be reduced if the user is forewarned and takes preventive measures.
Ron
Ron Gratz,

Would you be more specific about the "surprises of a type not encountered with a conventional hitch".

We have towed with the ProPride now for some 10,000 miles about the country in all types of terrain, traffic, and weather conditions including dodging highway fools and crossing deer.

Never have experienced any surprises, never had the hitch move off center, never had a Hensley bump. Nothing but the most pleasant towing experience and a huge improvement over conventional hitches we used in the past.

What is your surprising experience with a Hensley/ProPride? What are we in for?
__________________

__________________
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 12-14-2013, 07:33 AM   #157
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,603
Images: 1
Just as most tire problems come about due to lack of attention to their condition, a VPP hitch needs to be well set up (as with any WDH) and this "cures" the problem (more imaginary than actual). Classic examples are struts not tightened, or the effects of poor or a poorly-calibrated set of TT brakes.

The "problem" of "hitch bump" is surpassingly small, afterwards. One knows the conditions under which it may surface and that is a footnote to a main text which makes for a gulf between this WDH type and any other. First place among hitch types makes second place so distant that the differences between those others becomes tiny.

A detail. But, then, so are radial tires, gas shocks, electronic engine controls and disc brakes. Add them together, for effect. Alternately, this is what may account for the changes of some truck manufacturer guidelines on towing: restoration of 50% or so of FALR where electronic stability control, etc, is substituted for being painstaking (ha!, a few hours of work at most). Tire loadings, CG concerns . . these are the details which one works towards to give that term its due.

Where the rubber meets the road with an articulated vehicle, (as SAE likes to call it, I prefer "combination vehicle") is the TV rear axle tire contact patch.

The bigger picture -- of TV, TT (their design), and the best conditions of hitch rigging (design and verification) -- are where to focus. A tiny half-century old Caravel versus an SO 30' of ginormous weight loaded to maximum doesn't change the main concerns, only the how-to.

.
__________________
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 9-cpm solo, 15-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 12-14-2013, 07:40 AM   #158
4 Rivet Member
 
Livingston , Texas
Join Date: Dec 2007
Posts: 394
Quote:
Originally Posted by dkottum View Post
Ron Gratz,

Would you be more specific about the "surprises of a type not encountered with a conventional hitch".
Doug, as you will note from my text which you quoted, I was specifically referring to problems associated with the "bump".

Some examples of unexpected bump-related events are described by SteveH and others in http://www.airforums.com/forums/f238...ml#post1324867

Also please note that I said "can provide" rather than "will provide". The vast majority of users of 4-bar linkage hitches have not reported bump-related problems.

Ron
__________________
Ron Gratz is offline   Reply With Quote
Old 12-14-2013, 07:43 AM   #159
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,410
Images: 5
I've only had the bump once. It was the result of one or the other (or both)..air in the disc brake system causing more of a pad application delay than normal....and a controller that was not as compatible, or high quality as the one I have now.
__________________
-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 12-14-2013, 07:47 AM   #160
Rivet Master
 
1988 25' Excella
1987 32' Excella
Knoxville , Tennessee
Join Date: Oct 2010
Posts: 2,165
Blog Entries: 1
"With a 4-bar hitch it's always a good idea to have a brake controller which can cause the TT brakes to "lead" the TV brakes"

Somebody please explain how is this even possible??

The only way I can see to assure that the trailer brakes come on first is to delay the TV brakes slightly from the initial push on the pedal. I do not think I want a setup like that. You are sure not going to get the trailer brakes on first with one of the very common inertia based controllers.
__________________
Bill M. is offline   Reply With Quote
Old 12-14-2013, 07:50 AM   #161
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,410
Images: 5
You're right Bill, On many of the newer units, which are not pendulum type, there may not be any adjustment for "leading" the trailer brakes. On the old pendulum type you could lie to the controller about the levelness of the unit and adjust in an early application.
__________________
-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 12-14-2013, 08:12 AM   #162
4 Rivet Member
 
Livingston , Texas
Join Date: Dec 2007
Posts: 394
Quote:
Originally Posted by Bill M. View Post
"With a 4-bar hitch it's always a good idea to have a brake controller which can cause the TT brakes to "lead" the TV brakes"

Somebody please explain how is this even possible??
Some brake controllers use the brake light circuit to activate a feature which sends current to the trailer brakes before TV braking action takes place.

Examples are the acceleration-based Prodigy's "boost" feature and the pressure-based BrakeSmart's "Initial Brake Constant" feature.

The small delay time between brake light circuit activation and application of TV brake force is sufficient to cause the trailer brakes to "lead" the TV brakes.

Ron
__________________
Ron Gratz is offline   Reply With Quote
Old 12-14-2013, 08:13 AM   #163
CLOUDSPLITTER "Tahawas"
 
ROBERT CROSS's Avatar

 
2003 25' Classic
Zanadude Nebula , WNY
Join Date: Jun 2007
Posts: 11,153
Images: 1
Thumbs up

Quote:
Originally Posted by Bill M. View Post
"With a 4-bar hitch it's always a good idea to have a brake controller which can cause the TT brakes to "lead" the TV brakes"

Somebody please explain how is this even possible??

The only way I can see to assure that the trailer brakes come on first is to delay the TV brakes slightly from the initial push on the pedal. I do not think I want a setup like that. You are sure not going to get the trailer brakes on first with one of the very common inertia based controllers.

Determine how much pedal movement you have before the brake lights come on.


With the Tekonsha's I previously used..

The best way I found was to wire to the brake pedal and not the light circuit.

The first 1/2" or so of pedal movement usually won't apply very much TV braking....hence you see brake lights on while following a car with a headless driver.
A switch taking advantage of that 1/2" took care of the problem on our 95 Burb.

POI..I've had no 'bumps' since using the TruControl Gold with the haha.

Bob
__________________
PFC.....

“After all these years the reason I continue to love Thanksgiving.....I still sit at the kids table.”
RLC

Sandra wanted to go to Cleveland on vacation,
but I’m the Husband, so we went to Cleveland.
RLC
ROBERT CROSS is offline   Reply With Quote
Old 12-14-2013, 08:48 AM   #164
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,603
Images: 1
BenK over on WOODALLS did a very nice job of showing how he modded a brake light switch to get "TT brake first".
__________________
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 9-cpm solo, 15-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 12-14-2013, 08:51 AM   #165
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Quote:
Originally Posted by slowmover View Post

Where the rubber meets the road with an articulated vehicle, (as SAE likes to call it, I prefer "combination vehicle") is the TV rear axle tire contact patch.
What are your thoughts about that?
__________________
mstephens is offline   Reply With Quote
Old 12-14-2013, 09:08 AM   #166
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,603
Images: 1
If the contact patch is lost, then real trouble ensues.

The gold standard in all this, IMO, is in braking to a full stop. All else depends from this.

Remaining upright and lane-centered is the ongoing, lesser, goal which feeds that.
__________________
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 9-cpm solo, 15-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 12-14-2013, 09:54 AM   #167
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Quote:
Originally Posted by slowmover View Post
If the contact patch is lost, then real trouble ensues.

The gold standard in all this, IMO, is in braking to a full stop. All else depends from this.

Remaining upright and lane-centered is the ongoing, lesser, goal which feeds that.
Right. In spite of the confusion that ensues over the second law of friction, it certainly appears true that large patches with sticky rubber definitely shorten stopping distances. This is another example of why there is more to tires than load capacity.

I think the idea of being able to come to a panic stop in your own lane in a short distance should be the goal of any tow vehicle design. A good standard for a TV with large TT might be 225' from 60MPH, as an example. We rarely see such data reported for TVs. Wouldn't it be fascinating to take a particular TV, and then test stopping distance from 60MPH with say a 22' a 25' and a 30' Airstream? To me, that would be far more enlightening than simply reading "9500# towing capacity."
__________________
mstephens is offline   Reply With Quote
Old 12-14-2013, 10:49 AM   #168
Prairie Schooner II
 
Jim Flower's Avatar

 
2012 30' International
1997 25' Safari
1967 20' Globetrotter
Burlington , Ontario
Join Date: Jul 2009
Posts: 1,182
I wonder if the manufacturers have this data and it helps to explain their reluctance to adopt J2807.
__________________

__________________
Jim
Jim Flower 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



Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 05:53 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.