Reply
 
Thread Tools Search this Thread Display Modes
 
Old 06-01-2010, 08:24 PM   #29
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,583
Images: 1
Handling Requirements

Standard J2807 specifies that an understeering handling attitude must be maintained up to at least 0.4g cornering without a weight distributing hitch. With a weight distributing hitch . . an understeering attitude must be maintained up to only 0.3g cornering

As with above comments, disingenuity and narrow context. Even a piss-poor TV/TT combination pass "the test."

In other words, in a nasty situation on the road (high crown, bad repair, highway speed), the bar to "success" is low. That is to say, what is possible and what "meets standard" diverge pointedly, it appears in re beneficial handling/braking. Or . . . ?

Can of worms? . . . at what point does a rig benefit from a WDH?




2010 DODGE Ram 2500 shortbed, (empty)
Roadholding, 300-ft-dia skidpad: 0.70 g

2010 Dodge Ram 2500 Laramie Mega Cab 4x4 - Short Take Road Test - Auto Reviews - Car and Driver

The comparability of skidpads and roadways? Pertinence?




(March 13, 2009) RVIA’s “Current Issues in Designing Trailers” seminar was held on March 5 at the RV Hall of Fame in Elkhart, Ind.

RVIA Today Express

RVIA’s “Current Issues in Designing Trailers” seminar was held on March 5 at the RV Hall of Fame in Elkhart, Ind. Sponsored by AL-KO Kober Corporation, Dexter Axle, and Norco Industries, the seminar was attended by more than 80 engineers, designers, production line foreman and supervisors involved with trailer design and development.

RVIA Board Member Gregg Fore kicked off the five-hour training session by welcoming the attendees, who represented more than 36 member companies. Seminar leaders Richard Klein and Harley Holt focused on trailer design engineering, then on SAE standards and related activities. In addition David Kinder, Esq., and Steve Arndt, Ph.D., spoke to the group about warning labels and consumer information.


RVIA 45" Pay-per-view video (Richard Klein)
RVIA's Video Site - RVIA Video Clip Library





.
__________________

__________________
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 06-02-2010, 09:40 AM   #30
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
in looking at that steering issue, what I am finding of interest is the requirement that oversteer not be in evidence in nominal circumstances.

It is an inappropriate response to oversteer that is often behind loss of control incidents. This is being addressed in the standard.

I think bringing in "really nasty" is the reduce to absurd fallacy. When that is coupled with non referenced judgments like "piss-poor TV/TT combination" the example only supports the reason for the SAE standard: having some objective referent by which to evaluate capabilities. We can then argue about the relative merit of standard criteria rather than more subjective assessments of rigs.

re: "at what point does a rig benefit from a WDH?" -- the question like this would be better presented as something to a cost versus benefit point: "when is the benefit of a WDH worth the cost (both capital as well as ongoing, outlay and procedure)?"

Now to considering what a .3g or .4g turn is. I don't think I hit that point in my RV very often.
__________________

__________________
bryanl is offline   Reply With Quote
Old 06-02-2010, 10:47 AM   #31
4 Rivet Member
 
Airstreamer67's Avatar
 
Join Date: Nov 2002
Posts: 311
Although the new process to determine standards for the industry will have some growing pains and get hit by a lot of slings and arrows, it is great that they are finally doing it.

I have long had the feeling that many Internet myths and lessons presumably learned from the days when sedans were the main towing vehicles for travel trailers are way off base when it comes to modern towing vehicles, particularly 250 and 350-class pickups.

Let the cards fall where they may. It's a great endeavor. Maybe the 80% ironclad rule won't be so seductive anymore. Maybe some of the self-made rules "police" will become less strident. Maybe there won't be the battles over things that heretofore have had no objective testing?

Maybe?

Nawwwwww.
__________________
Airstreamer67 is offline   Reply With Quote
Old 06-02-2010, 06:18 PM   #32
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,583
Images: 1
It is an inappropriate response to oversteer that is often behind loss of control incidents. This is being addressed in the standard.

Yes, "overcorrection" is one way of saying it. The "standard" appears to be a low bar to cross.

Reductio ad absurdum: No, there are -- and will be -- better and worse possibilities in re brand new TV's and TT's (alone, to leave out the huge range of other trailer types), and some WILL be piss poor in combination. Which begs the question of whether WDH might be of help. And why the standard appears to be so low as to tell the customer it isn't needed . . when it might be a very good idea.

All safety devices have a cost/benefit ratio. Nothing new. Still says nothing about efficacy of WDH.

A .3G turn is easily attained. Thus the "concern" about yaw. .5G might mean something (however scary to experience . . which is the point).

Maybe there won't be the battles over things that heretofore have had no objective testing?

It is a question of whether it actually is objective. "Definitions" that allow any and all to succeed cannot be said to be defining. Straw man arguments ensuing . . . .

I'm in favor of a better explanation of what is involved in meeting J2807 by GM. It may be a decent floor from which to work for the rest of us.

Thus far I have the impression that it is a way to forestall responsibility by manufacturers about what works -- and why -- in regards towing best practice. It appears minimal, and setting up WDH takes work . . so let's eliminate the need (via distortion of meaning). Keep the plaintiff lawyers away. Continue current practices without genuine change.

.
__________________
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 06-03-2010, 06:24 AM   #33
4 Rivet Member
 
Airstreamer67's Avatar
 
Join Date: Nov 2002
Posts: 311
Testing vehicle-specific factors to determine their towing abilities under a regimented formula is a giant leap forward.

No, as we've already seen, it won't be possible to get everyone to agree on what parameters should be incorporated in the formula.

However, the endeavor should help tremendously to determine safe towing limits of a vehicle...and to be able to better compare one vehicle to others...and to perhaps update good practices for modern vehicles used for towing.

I don't think the hitch manufacturers have the resources to get the job done. I think they have been necessarily winging it, basing their recommendations on a little engineering and a lot on outdated and overgeneralized anecdote. In defence of them, how could they possibly test every vehicle that has a tow rating on them and to give specific rigging advice for each?

I'm hoping the larger vehicle industry will be able to guide us better as to what their specific vehicles can do based on standarized criteria.

However, I don't expect them to set the criteria so high that a trailerist feels he can maneuver his rig like a sports car. I think too many accidents are already caused by high-speed drivers trying risky maneuvers on the highway with varying types of vehicles and trailers, combined with road adhesion factors that change with the weather.

I think we would all be better off if we all haul our trailers like we KNOW the things won't maneuver very well, certainly not as well as an unladened vehicle, and to set our speeds and driving techniques accordingly.

High levels of G-factor turning ability when towing doesn't seem very attractive to me given all the circumstances involved in towing heavy trailers, especially since developing and testing for a high level of maneuvering ability with the extreme variations of rig and road combinations would probably be impossible to realistically and consistently achieve anyway.
__________________
Airstreamer67 is offline   Reply With Quote
Old 06-03-2010, 06:58 AM   #34
Rivet Master
 
Road Ruler's Avatar
 
Currently Looking...
St. Catharines , South Western Ontario
Join Date: Aug 2002
Posts: 2,364
Images: 39
Quote:
Originally Posted by Airstreamer67 View Post
High levels of G-factor turning ability when towing doesn't seem very attractive to me
It seems a lot of folks have the same thoughts.

Consider the ones that tow large heavy 5th wheels with large heavy TV's that both have a high center of gravity and a high hitch mounting point. No doubt they have reduced control in an emergency maneuver.

On the positive side most of us tow an Airstream and it is no secret that these trailers when pushed have superior road handling qualities. This is a huge benefit when a situation unfolds (and they do happen) and one finds themselves at the mercy of those road handling abilities.

Not long ago we were heading out with Airstream in tow. It was getting dark and we were on a straight flat road on flat land. Out of nowhere we came upon a sharp right hand curve. I'm not sure whether I missed a sign of the sign was AWOL but we made it through the turn without an issue.

I was amazed at how well the TV and Airstream tracked doing this aggressive change in direction producing a multitude of "G's".

Sometimes crap happens out there on the roads and we need to be thankful the hardware is up to the task of handling it.
__________________
Airstreams..... The best towing trailers on the planet!
Road Ruler is offline   Reply With Quote
Old 06-03-2010, 09:16 AM   #35
4 Rivet Member
 
Airstreamer67's Avatar
 
Join Date: Nov 2002
Posts: 311
Road Ruler, I agree with that. I've towed my Airstream since 1986, and often feel lucky to be towing a low center-of-gravity, well-balanced and torsion-bar-suspended trailer. I think it's the trailer of choice for anyone who wants the best towing rig possible.

What I thought I was referring to are new testing standards for tow vehicles. My point is that there are so many types of vehicle-and-trailer combinations, that setting some arbitrarily high G-rating for safe towing for a particular vehicle would not be particularly helpful in determing what they can safely tow. If they did, Airstream likely would be the trailer of choice for testing, and perhaps a beefed-up Corvette would get the top tow vehicle G-factor rating :-)
__________________
Airstreamer67 is offline   Reply With Quote
Old 06-03-2010, 09:53 AM   #36
Wise Elder
 
Jammer's Avatar
 
2010 30' Classic
Vintage Kin Owner
South of the river , Minnesota
Join Date: Dec 2009
Posts: 4,119
It would seem to me that a responsibly engineered combination would maintain steering stability until the point where the combination skids or rolls is approached, just as responsibly engineered brakes should provide stopping ability approaching the limits of the tires.
__________________
Jammer is offline   Reply With Quote
Old 06-04-2010, 09:41 AM   #37
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
Oh, but if steering and braking were simple things!

but they aren't.

Vehicle brakes are much stronger than any possible tire friction on the road - so much so that modern systems now have modulators to keep that state (skidding) from happening.

Skidding the trailer tires, though, is still how you can test your trailer brakes and breakaway switch. The real issue with braking is heat dissipation for long term braking such as using brakes rather than gears on a long downgrade.

As for steering, what I find interesting is the concern for how it changes under various conditions, the change from understeer to oversteer, for instance. Out of control conditions often stem from the driver not reacting properly to rig handling. I don't have my thoughts well formed here, yet, so I can only suggest taking a closer look rather than just writing it off to some extreme. There is much for many to learn about some of the topics (especially sway) that get a lot of heat in discussions.

I think that caveat also applies to those trying to minimize the standards efforts. Rather than claim "arbitrarily" set criterion, why not see if you can find out how they were developed? The people involved have a lot at stake and are much closer to the issue than most here so it is probably not a good idea to dismiss their efforts without an extremely good basis.

From what I see here, I wonder if some folks understand what 'G' really measures in turns or its scale.
__________________
bryanl is offline   Reply With Quote
Old 06-04-2010, 08:42 PM   #38
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,583
Images: 1
My thoughts echo every same above. Yet, there is more to consider.

(Who has "dismissed effort"? Or, claimed "arbitrary"?)

Some "standards" are worked out in advance: a predetermined conclusion; in this case, I suspect, only to limit liability. While there would be nothing new in this for the automotive industry, to appearances it is disappointing. Which is why I asked if anyone had specific insight.

In other discussions I have seen references to papers by Korn and Bundorf (1965 & 1967, respectively). I see that (below) that there is a Tow Vehicle Trailer Rating Committee from which one might assume is not a purpose-specific recent assembly. Surely there is an institutional memory and more papers in the intervening years. Thus my hope of "enlightenment".



Performance Requirements for Determining Tow-Vehicle Gross Combination
Weight Rating and Trailer Weight Rating

Product Code: J2807 Date Published: 2008-04-23


Issuing Committee:
Tow Vehicle Trailer Rating Committee

Scope

This document establishes minimum performance criteria at
GCWR and calculation methodology to determine tow vehicle trailer rating for passenger cars, multipurpose passenger vehicles
and light trucks up to 19500 lb GVWR (Class 5).





A weight-distribution hitch is, in the experience of even the oldest of us, a strong recommendation or requirement in using travel trailers (to limit things) from a predetermined tongue weight.

To say that some vehicles no longer need a WDH is a big step.

A pickup truck is still a pickup truck. I see no announcement by GM that their trucks have some magical suspension/brakes or electronics (but suspect the latter is part of the "new" rating standard; and that using the "black box" this may be derivable after an accident; not my interest in asking).

Having searched I also find no announcement of revised towing guidelines for these 2011 trucks, or, a precis of what they may be.

In other words, why is it that a 1,200-lb TW off of a 25' lever no longer requires WDH even though dynamic forces may increase that weight x10. Or, x20?


.
__________________
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 06-05-2010, 09:14 AM   #39
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
re: "Who has "dismissed effort"? Or, claimed "arbitrary"?" -- perceptions, mostly, as backed up by the above post and re-reading the thread. It needs clarification if it is not a reasonably accurate perception.

re: "A weight-distribution hitch is, in the experience of even the oldest of us, a strong recommendation or requirement" -- The trailer is only part of the equation, the tow vehicle also contributes. The appeal to authority (the "oldest of us") doesn't help either IMHO.

re: " To say that some vehicles no longer need a WDH is a big step." -- not for many who don't use one. I know many who have found better towing performance by removing the WDH.

re: "why is it that a 1,200-lb TW off of a 25' lever" -- With 30' trailers and 20' tv's, I think this is a bit overdone.

The idea of a specification is that now we have a set of criteria to argue (discuss?) about. Instead of doing that, though, we see allusions to conspiracy, appeals to authority, arbitrary rules that don't consider circumstances, and straw men (i.e. manufactured scenarios).

The issue is whether or not there needs to be a measurable reason or whether we should do things based on arbitrary assertions. Many of the nonproductive discussions here tend towards supporting the latter. I think we need much more of the former.

What I find encouraging is that the spec is based on performance, not design criteria. That means it ties more directly with what people are after in a tow vehicle. From reading these forums, too many get hung up on design criteria like weight ratings, hitch configurations, weight ratios, and so on while most folks towing are after making the trip safe and sound without breaking anything.
__________________
bryanl is offline   Reply With Quote
Old 06-05-2010, 09:47 AM   #40
Rivet Master
 
Road Ruler's Avatar
 
Currently Looking...
St. Catharines , South Western Ontario
Join Date: Aug 2002
Posts: 2,364
Images: 39
Quote:
Originally Posted by bryanl View Post
What I find encouraging is that the spec is based on performance, not design criteria. That means it ties more directly with what people are after in a tow vehicle. From reading these forums, too many get hung up on design criteria like weight ratings, hitch configurations, weight ratios, and so on while most folks towing are after making the trip safe and sound without breaking anything.
This is the way I see.
__________________
Airstreams..... The best towing trailers on the planet!
Road Ruler is offline   Reply With Quote
Old 06-05-2010, 11:16 AM   #41
Rivet Master
 
3Ms75Argosy's Avatar
 
1975 Argosy 26
1963 24' Tradewind
Seattle , Washington
Join Date: Aug 2002
Posts: 2,341
Images: 7
Someone asked for a definition of "oversteer" and "understeer"... from racing...

As one approaches and enters a corner, 3 cornering attitudes can occur...

1) A "neutrally" handling car will slide all four tires in unison, going exactly where (up to the limit of adhesion) it's pointed via the steering wheel.

2) At the limit of cornering adhesion, a "understeering" car will start to "push" through the corner towards the outside of the corner, requiring more and more steering input to make the car go around the corner. The front tires loose adhesion first, making the car want to go towards the outside of a corner.. maybe not making the corner. Most factory cars/ trucks are tuned towards understeer (esp FWD cars because of the forward weight bias) because it's considered easier for everyday people to recover from in an emergency situation.

3) At the limit... an "oversteering" car will loose adhesion at the back of the car. As the car goes around the corner, the back of the car will start to pivot to the outside of the corner, and the front will point to the inside of the corner.. if not corrected, leading to a spin.

Most high performance TRACK drivers want either a neutral or slightly oversteering attitude at the limit. I can see why oversteering AT THE LIMIT would lead to a jackknife.

I think one might be surprised how easy it's to get to .4g's...

Marc
__________________
3Ms75Argosy is offline   Reply With Quote
Old 06-05-2010, 11:35 AM   #42
Rivet Master
 
Road Ruler's Avatar
 
Currently Looking...
St. Catharines , South Western Ontario
Join Date: Aug 2002
Posts: 2,364
Images: 39
This combination could pull 4 G's...... maybe even 6 or 7!

YouTube - Maserati Gran Turismo pulling caravan
__________________

__________________
Airstreams..... The best towing trailers on the planet!
Road Ruler 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
SAE vs Manufacturer's Tow Ratings Denis4x4 Tow Vehicles 5 11-16-2007 01:09 PM
SAE to correct Tow Rating lies... Road Ruler Tow Vehicles 9 04-15-2007 02:19 PM
Trailer length standards jcanavera Airstream Trailer Forums 4 08-10-2006 06:16 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 11:27 AM.


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.