Reply
 
Thread Tools Display Modes
Old 01-12-2011, 01:51 PM   #41
Moderator Emeritus
 
MtnGuy's Avatar
 
Join Date: Sep 2008
Location: Shenandoah Valley
Posts: 9,274
I gotta draw things out to cipher on this type of problem, but this is the way I kinda see it.

Click image for larger version

Name:	img028.jpg
Views:	171
Size:	57.5 KB
ID:	4205

By my understanding of high school geometry, you find the center of a triangle by using 1/2 of each vector angle, and drawing a line outward to the opposing side. That is the cross with the circle around it (triangle CG).

The other cross is the CG of the camper.....which I should have put back further.....that trailer would have really light tongue weight.

If a tire goes down, I would think that the CG of the camper would stay at the same location, or even shift slightly towards the flat tire side, since the top of the camper would move that direction because of lean. That would move a lot of weight to the single tire.

I figure the only way that each tire would support 33% of the weight, is if the CG of the camper should move towards the CG of the triangle....which doesn't seem like it should happen.

Do I have everyone thoroughly confused yet ??
__________________

__________________

Chap , DW Joy, and Fur Baby Sango
2017 F350 Lariat CCSB, SRW, 4x4, 6.7 PS
2017 Grand Design Reflection 337RLS
MtnGuy is offline   Reply With Quote
Old 01-12-2011, 02:10 PM   #42
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,157
Now see, that is what I said! (and got spanked). In your drawing the CG is closer to the two tandem wheels. If all four were on the ground the CG would be in the exact center. If the CG moves away from the failed wheel the load should move with it.

However my sister had a valid input on this very point. The CG should not move (very much) because the tire that is flat still weighs the same as a tire with air in it. In fact due to compression in the single tire it will have a lower height due to spreading out the load over a larger footprint. This would shift the CG slightly towards the single tire as the camper leans toward that side.
Attached Thumbnails
Click image for larger version

Name:	Project1.jpg
Views:	139
Size:	25.3 KB
ID:	4206  
__________________

__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is online now   Reply With Quote
Old 01-12-2011, 02:19 PM   #43
Moderator Emeritus
 
MtnGuy's Avatar
 
Join Date: Sep 2008
Location: Shenandoah Valley
Posts: 9,274
But the CG of the camper does not move towards the CG of the triangle, where it would be closer to the 2 wheels on the good side. The CG of the camper stays at the same place, leaving leaving a lot more weight of the triangle on the single wheel.
__________________

Chap , DW Joy, and Fur Baby Sango
2017 F350 Lariat CCSB, SRW, 4x4, 6.7 PS
2017 Grand Design Reflection 337RLS
MtnGuy is offline   Reply With Quote
Old 01-12-2011, 02:39 PM   #44
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,157
Quote:
Originally Posted by mtnguy View Post
But the CG of the camper does not move towards the CG of the triangle, where it would be closer to the 2 wheels on the good side. The CG of the camper stays at the same place, leaving leaving a lot more weight of the triangle on the single wheel.
The CG is the center of gravity. That is the place where in the solid object where all weight vectors are zero except for gravity. Of necessity it will be above the plane of the frame (since there is a camper up there).

For simplicity we were discussing there the center of gravity weight vector breaks the plane of the frame. (When the CG weight vector crosses the side of the camper, the camper topples over).

I think you meant the center of the triangle; and not the CG of the triangle in that case. Your drawing made the CG logic more clear to me.

The CG will stay exactly wherever it was in the centroid of the mass of the camper. The downward weight vector is what we were discussing. Front to back the CG should stay the same since the flat tire is still ON the axle and its weight has not changed very much. Top to Bottom its should stay the same. Left to right, it should actually move toward the flat tire side a bit since the tire will "squat" more than the two tandem tires since there is more tread there to distribute the weight.

What that weight IS is what I am still struggling with.
__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is online now   Reply With Quote
Old 01-12-2011, 02:48 PM   #45
Moderator Emeritus
 
MtnGuy's Avatar
 
Join Date: Sep 2008
Location: Shenandoah Valley
Posts: 9,274
Quote:
Originally Posted by herk7769 View Post
I think you meant the center of the triangle; and not the CG of the triangle in that case. Your drawing made the CG logic more clear to me.
Yes, I should have stated the center of the triangle. But if each vector holds the same amount of weight, then shouldn't the center of the triangle also be the center of gravity for that triangle ?? So in the case of a flat, if those tires each supported 33% of the weight of the camper, then the center of gravity would be at that point of the triangle........which is not the case.....it stays the same, somewhere down the centerline of the camper.
__________________

Chap , DW Joy, and Fur Baby Sango
2017 F350 Lariat CCSB, SRW, 4x4, 6.7 PS
2017 Grand Design Reflection 337RLS
MtnGuy is offline   Reply With Quote
Old 01-12-2011, 03:06 PM   #46
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,157
Quote:
Originally Posted by mtnguy View Post
Yes, I should have stated the center of the triangle. But if each vector holds the same amount of weight, then shouldn't the center of the triangle also be the center of gravity for that triangle ?? So in the case of a flat, if those tires each supported 33% of the weight of the camper, then the center of gravity would be at that point of the triangle........which is not the case.....it stays the same, somewhere down the center line of the camper.
Well that was wear my logic fell apart. All my engineer family members clearly informed me that the CG does not move (much). I thought the CG vector WOULD move to where you indicated (the center of your triangle).

If the CG WAS in the center of the triangle, only then would the weight be evenly distributed between the three remaining tires. Since it does not move (much) the load does not transfer to the other (good) side. It stays even 4000 on each side. That much everybody agrees on. Where we still are debating (Seattle Amadios and Valley Forge (Amadios) Arringtons, is whether the actual tire load for the good side (4000) is evenly shared by the two tandem tires or is carried by one (mostly). And WHICH one if true. The same axle? or the opposite axle?
The wobbly 4 legged chair argument or the Symmetry argument.

This debate is complicated by the fact that they actually have to WORK and not just humor the old man all day.

While this is all great fun, I can't help but realize that whichever it turns out to be, I was wrong. The 3 legged stool is not the answer.
__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is online now   Reply With Quote
Old 01-12-2011, 03:12 PM   #47
Moderator Emeritus
 
MtnGuy's Avatar
 
Join Date: Sep 2008
Location: Shenandoah Valley
Posts: 9,274
The way I look at it, is that both sides still carry the same weight. The good side weight per tire should not change, but the good tire on the flat side would carry all of the weight of the bad side, minus what little weight the wheel to the ground flat would carry.

Lou, you think we might be hogging this thread.

Seriously, this is a good way to work this out, get members input, and come up with an answer to have for future reference.
__________________

Chap , DW Joy, and Fur Baby Sango
2017 F350 Lariat CCSB, SRW, 4x4, 6.7 PS
2017 Grand Design Reflection 337RLS
MtnGuy is offline   Reply With Quote
Old 01-12-2011, 03:35 PM   #48
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,157
Oh! I have no doubt we are beating a dead horse!
Unfortunately its my nature to want to nail this sucker to the floor.

What started this line of discussion was a concern that once a tire blows, the other tire on the same side should also be replaced ASAP since it was subjected to a 100% overload. I did not think it needed to be since the overload would not be all that much (assuming 1/3 of the load not 1/2).

Now I see that there is a possibility that all four tires may have experienced overloads in excess of their safety margin. If nothing else, I would like to "know..."
__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is online now   Reply With Quote
Old 01-12-2011, 06:00 PM   #49
Senior Member
 
fonzie's Avatar
 
Join Date: Sep 2010
Location: Eastern Ontario
Posts: 3,236
Lou and mtnguy, looking at your drawings and without doing calculations, I believe that if tire B goes flat, the weight would be mostly transferred to tire A and D and less on tire C as it would try to rotate on axis AD?? How much weights is transferred?? my 2 cents
__________________
fonzie is online now   Reply With Quote
Old 01-12-2011, 06:11 PM   #50
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,157
Fonzie, I have to tell you that was the Rocket Engineer's read as well.
That was what he thought. The wobbly chair argument.
__________________

__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is online now   Reply With Quote
Reply

Tags
flagstaff

Thread Tools
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




ForestRiverForums.com is not in any way associated with Forest River, Inc. or its associated RV manufacturing divisions.


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 01:27 PM.