Reply
 
Thread Tools Search this Thread Display Modes
 
Old 12-14-2013, 10:50 AM   #169
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
Adopt was incorrect. Implement is more like it. Jim
__________________

__________________
Jim
Jim Flower is offline   Reply With Quote
Old 12-14-2013, 11:22 AM   #170
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
The SAE J2807 Braking Test is a bit limited, I think.

QUOTE
Braking Requirements

The test vehicle and trailer must stay within an 11.5 foot wide traffic lane during stopping tests. Stopping requirements from 20 mph without use of trailer brakes are;
1. in 35 feet or less with a tow rating of 3,000 lbs or less and no trailer brake requirement
2. in 45 feet or less with a tow rating of 3,000 lbs or less and a requirement for trailer brakes
3. in 80 feet or less for tow ratings above 3,000 lbs
The parking brake must be capable of holding the rig on 12 percent up and down grades
END QUOTE (from a blog, not from an SAE document)

There apparently is no test for 55MPH or 60MPH braking. I can see why the 20MPH test is useful, but it seems incomplete.
__________________

__________________
mstephens is offline   Reply With Quote
Old 12-14-2013, 01:00 PM   #171
4 Rivet Member
 
Livingston , Texas
Join Date: Dec 2007
Posts: 394
SAE J134, J134: Brake System Road Test Code - Passenger Car and Light-Duty Truck-Trailer Combinations - SAE International

and SAE J135, J135: Service Brake System Performance Requirements - Passenger Car-Trailer Combinations - SAE International

might be of interest.

Ron
__________________
Ron Gratz is offline   Reply With Quote
Old 12-15-2013, 09:58 AM   #172
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
I just paid SAE $61 each for those two documents plus a membership fee. Appears these will put you right to sleep, not thrilling reading.
__________________
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 12-15-2013, 10:00 AM   #173
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Quote:
Originally Posted by switz View Post
I just paid SAE $61 each for those two documents plus a membership fee. Appears these will put you right to sleep, not thrilling reading.
I was briefly tempted to buy them also, and I thank Ron for pointing to them. But I decided I could do some homework, googling, and probably find someone posting ABOUT them instead.
__________________
mstephens is offline   Reply With Quote
Old 12-19-2013, 09:33 AM   #174
New Member
 
Business , Alabama
Join Date: Dec 2013
Posts: 2
Quote:
Originally Posted by Ron Gratz View Post
Without providing the derivation, the relationship among these four variables is given by:
a*b = I/M
From this equation, if you knew the value for I, you could calculate an "optimum" value for a/(a+b) which is numerically equal to TW%.
From the book Vehicle Stability, by Dean Karnopp: he gives mab>Ic as a stability criterion for trailers. If that's the case, then ab = Ic/m is a minimal condition for stability, and more tongue weight adds stability, at the cost of more lateral hitch load. Thoughts?

As CAD practice a few years ago, I modeled my 5x8 utility trailer. While empty, ab=Ic/m at 8.4% TW. Actual TW=10.7%.
Actual Ic was 72% of Ic when using the formula for a rectangle: Ic=m*(h^2+d^2)/12
__________________
JeremyB is offline   Reply With Quote
Old 12-19-2013, 01:29 PM   #175
4 Rivet Member
 
Livingston , Texas
Join Date: Dec 2007
Posts: 394
Quote:
Originally Posted by JeremyB View Post
From the book Vehicle Stability, by Dean Karnopp: he gives mab>Ic as a stability criterion for trailers. If that's the case, then ab = Ic/m is a minimal condition for stability, and more tongue weight adds stability, at the cost of more lateral hitch load. Thoughts?
I agree that, for this single criterion, ab = Ic/m is a minimal condition for stability, and greater TW% (greater distance of CG forward of axles) adds stability.

However, the vertical force due to greater TW also will tend to cause less yaw stability.
On one hand, greater TW% is good for yaw stability. OTOH, greater TW is bad for yaw stability.

The challenge is to keep TW low while keeping TW% high enough for minimal Routh Criterion stability.

Ron
__________________
Ron Gratz is offline   Reply With Quote
Old 12-19-2013, 02:08 PM   #176
CLOUDSPLITTER "Tahawas"
 
ROBERT CROSS's Avatar

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

Now these guys must have have it figured out...

Bob
Attached Thumbnails
Click image for larger version

Name:	6331F314-902B-4359-99B6-BB9E734BBF6F-2908-0000018EB3DB3F2B_zpsc76d7638.jpg
Views:	70
Size:	186.8 KB
ID:	202045   Click image for larger version

Name:	16kthc6.jpg
Views:	70
Size:	36.4 KB
ID:	202046  

__________________
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 12-19-2013, 02:50 PM   #177
New Member
 
Business , Alabama
Join Date: Dec 2013
Posts: 2
Quote:
Originally Posted by Ron Gratz View Post
I agree that, for this single criterion, ab = Ic/m is a minimal condition for stability, and greater TW% (greater distance of CG forward of axles) adds stability.

However, the vertical force due to greater TW also will tend to cause less yaw stability.
On one hand, greater TW% is good for yaw stability. OTOH, greater TW is bad for yaw stability.

The challenge is to keep TW low while keeping TW% high enough for minimal Routh Criterion stability.

Ron
I'm missing why increased greater TW is bad for the trailer yaw stability. (Not being facetious ) I can see where it would cause worse combination vehicle yaw stability.
A later derivation in Vehicle Stability adds rotational damping and comes up with stability criterion that includes speed:

c(a+b)/U + mab > Ic

c= rotational damping
U= forward speed


Although if it stable by the previous criterion (mab > Ic), it will always be stable with the criterion with rotational damping.
__________________
JeremyB is offline   Reply With Quote
Old 12-19-2013, 04:17 PM   #178
4 Rivet Member
 
Livingston , Texas
Join Date: Dec 2007
Posts: 394
Quote:
Originally Posted by JeremyB View Post
I'm missing why increased greater TW is bad for the trailer yaw stability. (Not being facetious ) I can see where it would cause worse combination vehicle yaw stability.
Sorry, I should have been more explicit. When I introduced "vertical force due to greater TW", I was alluding to effect of TW on the TV.

Quote:
A later derivation in Vehicle Stability adds rotational damping and comes up with stability criterion that includes speed:

c(a+b)/U + mab > Ic

c= rotational damping
U= forward speed

Although if it stable by the previous criterion (mab > Ic), it will always be stable with the criterion with rotational damping.
I agree. However, with the introduction of rotational damping, stability no longer requires mab>Ic. With rotational damping, you can have stability with Ic>mab as long as U does not exceed a critical speed, Ucrit.

Ucrit can be defined by replacing U in the above inequality with Ucrit and changing the inequality to an equality.

Then, Ucrit = c(a+b)/(Ic-mab)

This equation says the critical speed decreases as the polar inertia increases and/or the product, mab, decreases.
This could explain why some improperly loaded trailers suddenly develop oscillations at a certain speed.

Ron
__________________
Ron Gratz is offline   Reply With Quote
Old 12-19-2013, 06:07 PM   #179
Rivet Master
 
SteveSueMac's Avatar

 
2012 27' Flying Cloud
W , New England
Join Date: Oct 2012
Posts: 5,412
What do you think about c(am)/p-ing ?


:-)

Sorry - just being a wise guy.....back to the adult table :-)
__________________
SteveSueMac is offline   Reply With Quote
Old 12-29-2013, 01:24 PM   #180
Rivet Master
 
mefly2's Avatar
 
2015 25' FB Eddie Bauer
Western , ** Big Sky Country ** Montana
Join Date: Feb 2010
Posts: 2,283
Good to know about the smart car ...guess that we can ditch the 3/4 diesel and just use our chev spark to tow now ... lmao!
__________________
mefly2 is offline   Reply With Quote
Old 12-30-2013, 04:37 PM   #181
Rivet Master
 
ALANSD's Avatar

 
1966 26' Overlander
Woodstock , Georgia
Join Date: Feb 2002
Posts: 8,463
Bottom line this multipager for me...can I tow a 4500lb Airstream with a 6 cylinder chrysler 300?
If so that would be a great option for me..and affordable used.
__________________
1966 Overlander
AIR #005
Please visit our blogs and web pages:
OUR AIRSTREAM PASSION! BLOG
RESTORING AN AIRSTREAM
Our AIRSTREAM and TIN CAN TOURIST Rallys
ALANSD is offline   Reply With Quote
Old 12-30-2013, 05:52 PM   #182
Rivet Master
 
mstephens's Avatar
 
2013 25' Flying Cloud
Cat City , California
Join Date: Sep 2012
Posts: 854
Quote:
Originally Posted by ALANSD View Post
Bottom line this multipager for me...can I tow a 4500lb Airstream with a 6 cylinder chrysler 300?
If so that would be a great option for me..and affordable used.
I think absolutely yes, but my own 300 TV won't be ready yet for a couple weeks. All the parameters for a good tow are met by the V6 300 if you get the sport shift option so you can choose your gears in the 8-speed box. And, assuming you make the mods mentioned in the thread. The Airstream was designed specifically for easy towing. You're paying extra for that, you may as well take advantage of it.

I think the price used is especially good.
__________________

__________________
mstephens 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 11:40 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.