JJBIRISH wrote:Ron Gratz wrote:
Apart from the possible structural consequences --
reducing TW by adding load to the far rear of a trailer, IMO, is a bad idea.
Adding load at that distance from the trailer's center gravity has a big effect on the trailer's polar moment of inertial.
Both the decreased TW and the increased polar moment of inertia tend to decrease the trailer's yaw stability and make sway more likely.
If you need to reduce TW it is much better to move load from the front of the trailer toward the center of the trailer.
Ron
This is the right answer… almost all the other answers fall under the category of I did it and got away with it, or is just blind luck…
In addition to encouraging sway there are other reasons why it’s a bad idea though…
Loading the extreme ends of a beam to balance the load on the beam is about as bad of an Idea as there is… you have to consider the magnitude and amplification of the dynamic loading when doing this… it is equivalent to trying to convert the beam into a spring to absorb and compensate for the shock of the improper loading… on a trailer this is magnified on the rear half of the beam that has no support design for this purpose… less problematic for the front load because it has 2 load points… it’s much more than just the bumper or welding a receiver hitch to the frame as so many want to believe and advocate…
The only correct why to balance the trailer is by relocating weight within the trailer by putting heaver items closer to the axles and lower, with lighter loads toward the front and rear and higher to achieve the balance you need…
While the 10% t0 15% TW is correct achieving that by over or under loading the other end is poor advice…
Ron Gratz wrote:
Apart from the possible structural consequences --
reducing TW by adding load to the far rear of a trailer, IMO, is a bad idea.
Adding load at that distance from the trailer's center gravity has a big effect on the trailer's polar moment of inertial.
Both the decreased TW and the increased polar moment of inertia tend to decrease the trailer's yaw stability and make sway more likely.
If you need to reduce TW it is much better to move load from the front of the trailer toward the center of the trailer.
Ron
W.E.BGood on 09/07/14 wrote:
The tongue weight was 625 lbs. before filling the 30 tank with 240 lbs. (30 gallons) of water, which raised it to 760 lbs.
W.E.Good on 09/08/14 wrote:Perhaps the higher tongue weight was measured after the tank was drained rather than after the tank was filled?
The weights were obtained with a Sherline LM2000 belonging to the service mgr. at a local RV dealership that we placed under the tongue jack foot, first with the tank full, then drained. He and I both looked at the dial.
bkcauley wrote:
The TT I'm looking at is 6450 with a tw of 745 so that's 11.56 percent on the tounge. So that's good.
W.E.BGood wrote:Impossible.
"Perhaps you need to re-check your weights.
Ron"
Ron and Peeps, you're correct, I didn't read my own notes, it should have been 50 gallons (not 30) for 417 lbs. (not 240).
The fresh tank is, in fact, in the rear of the trailer (the fill is about 2 1/2 feet forward the rear corner, and I can see the tube and the pump line where they go down into the tank from the inside).
The weights were obtained with a Sherline LM2000 belonging to the service mgr. at a local RV dealership that we placed under the tongue jack foot, first with the tank full, then drained. He and I both looked at the dial.
While my first water quantity and weight numbers were incorrectly posted, the illustration is still valid, eg. adding weight to the "rearend" CAN still add weight to the tongue.
Regards, BGood
Huntindog wrote:
I relocated my batteries on my last TT to reduce the TW. It worked well,BUT.... My TW was a lot due to my generator and 26 gallon fuel tank install.
TW questions appear here often. They always generate a lot of opinions. Most of them are right,,,, and wrong.
The reason is simple. Everyone bases their opinion on their experiences.. But someone could have the exact TT as I, and have TW that is hundreds of pounds different than I have. No two peoples usage, gear and loading will be the same.
8-10% may work for a light utility trailer, but is not a good idea for a TT.
TTs need more TW because when they start to sway, the box catches the wind like a large sail and makes it worse, AND many TTs weigh more than the TV... With those two factors working against a smooth tow, it is foolish to try to make the TW as light as possible.
And then there is another factor unique to TTs. During a trip, the weight in the TT shifts around quite a bit. FW gets used and ends up in the grey/blackwater tanks. Food/drink gets eaten and ends up in the black tanks. Propane gets burned and disappears from the TW. Clean clothes get worn and end up in the hamper etc... Other things may ride home in a different location for many reasons. So cutting it close on TW can be really bad.
TTs generally need 10-15% TW. More is better. But as a practical matter, 15% is usually the limit due to hitch and TV limitations.
I have a stout TV, so I like my TW heavy. I also have 4 42 gallon waste tanks that are full for the return trip... So my TW can really change a LOT.
rexlion wrote:Be sure to leave a cushion for shifting of weight.hbillsmith wrote:
I've done exactly what you suggest however I followed a process to insure it was safe. First, in order to mount the box on the rear of the Trailer, I took it to a machine shop where they fabricated and installed a receiver hitch welded to the trailers frame and it's good for 300# to 500#. Next I loaded my stuff in the rear box and went to the CAT scales for 3 weights (a-truck with trailer attached and WDH active, b-truck with trailer took off the WDH and c-truck alone). The difference between truck alone and truck with TT is imputed gross weight of the loaded trailer. The imputed gross trailer weight minus the CAT scales weight of the trailer is the tongue weight. First check is to make sure the imputed gross trailer weight is within the trailer mfg. stated weight capacity. Second check is to divide the tongue weight by the imputed gross trailer to see if the percentage is between 10% to 15%. If either check fails, make adjustments. If you are over the total weight, take stuff out of the trailer and put it in the truck (assuming you have surplus truck payload). If the second check fails, move stuff from the rear toward the front.
This is the way to do it. Weld to the frame, and add enough weight to lighten the hitch to the 10%-12% range (no less than 10% though).
hbillsmith wrote:
I've done exactly what you suggest however I followed a process to insure it was safe. First, in order to mount the box on the rear of the Trailer, I took it to a machine shop where they fabricated and installed a receiver hitch welded to the trailers frame and it's good for 300# to 500#. Next I loaded my stuff in the rear box and went to the CAT scales for 3 weights (a-truck with trailer attached and WDH active, b-truck with trailer took off the WDH and c-truck alone). The difference between truck alone and truck with TT is imputed gross weight of the loaded trailer. The imputed gross trailer weight minus the CAT scales weight of the trailer is the tongue weight. First check is to make sure the imputed gross trailer weight is within the trailer mfg. stated weight capacity. Second check is to divide the tongue weight by the imputed gross trailer to see if the percentage is between 10% to 15%. If either check fails, make adjustments. If you are over the total weight, take stuff out of the trailer and put it in the truck (assuming you have surplus truck payload). If the second check fails, move stuff from the rear toward the front.
