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Old 10-30-2007, 12:23 AM   #43
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Thanks, 2air,

I used to weigh loads 5-7 times weekly as an OTR driver. I've had two discussions with CAT techs (oughta see their service trucks, whoa!) and have had to slide the rear tandems more times than I care to think about and re-weigh to not violate what is commonly called "the bridge law".

The above numbers are from across several months, and about 10-11 tickets, all but three are re-weighs (like you, I'll not bore everyone with details; about how much my weight dropped off from full fresh water to empty fresh water, etc).

Thanks for the info on springs weakening, and what you've done. I am not full-timing at this point so am willing to experiment somewhat. I'd be more likely to order up a custom leaf pack to fit the bill if I were full-timing and had a better grasp of this issue vis-a-vis my rig. And I'll bet that Dodge trucks are more stiffly sprung than the competition. Do you recall what your spring capacity is, and what you have (numerically) increased it to?

Am familiar with the Mor-ryde options; I'd like to also fit their Ind/Susp to my trailer as retrofit. AND disc brakes.

My concern is NOT with ride quality at this time. A truck is a truck. But the motions affecting the trailer are not to be ignored.

By the way, any of you know the drive-axle-to-rearmost-trailer-axle distance on your doubles or triples? I think mine is a bit longish, and would like to compare. Also, the length from hitch head center to that same rear axle hub/point.

Thanks all. I look forward to your advice and comments.
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Old 10-30-2007, 01:28 AM   #44
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Quote:
Originally Posted by REDNAX
SECOND WEIGH TICKET: W/D bars at max
(TV with full fuel, usual bed load and passengers. TT with full fresh water, empty waste tanks, empty propane [two 40# bottles]).

Steer: 4,060
Drive: 4,560
Trailer: 7,360#
Gross: 15,980
ok, final comment this round.

was this with the reese or haha? not that it matters from a w/d perspective...

this last ticket suggests that whatever spring bars you have, they are less than the tongue mass...

which WILL go up another 80lbs with lpgas on board and that will translate into another 100+ lbs on the drive axle.

fully flexed you don't appear able to evenly balance the load distribution, and that may not be your goal...

there are lots of guideline on steer/drive loads...

and my truck felt really good towing with 50/50 as noted in the o.p.

the set up was declared 'perfect' by those who know this stuff....

your measurement difference is within the '10% rule' without lp gas and may still be after adding lp gas.

recently as an experiment i towed 5k miles with the drive axle 900 lbs heavier than the steering axle or right AT 10%...

tire pressures were adjusted to the load difference.

the steering felt a tad lighter (if 4400 lbs is light) for the first few hours but i soon adapted and the lightness vanished.

i towed this way at up to 75 mph over mountains, with high winds, in urban commuter traffic and through snow, rain and hail. yes hail.

the ONLY differences i reliably could find were...

1. slightly higher tire temps on the drive axle (about 8-10 degrees)

2. 3-4/32nds MORE tire wear on the drive axles after 5,000 miles...

but steering control and drive stability seemed no different from towing with more load on the steering wheels.

so my point is the rules for balancing steer/drive axle loads exist, but perhaps they aren't fixed and absolute.

cheers
2air'
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Old 10-30-2007, 04:00 AM   #45
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Quote:
Originally Posted by REDNAX
According to Andy/Inland RV I'll need:
1. Length of Trailer
2. Tongue Weight
3. TV Wheelbase
4. TV Spring Capacity
What information would you have me gather to get this underway besides the above?
I suggest you also need:
5. Length of rear overhang on tow vehicle from rear axle to hitch ball.
6. Length from trailer hitch to center of trailer axle system.
7. Length of load distribution bars.

If you read this thread:
http://www.airforums.com/forums/f464...sis-19236.html
and punch your numbers into the equations, you should gain a greater understanding of your rig, so as to make more informed decisions.
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Old 11-01-2007, 07:21 AM   #46
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2Air, those numbers are with the H/A. I first "studied" them as a result of your thread (and my ensuing search on this forum and others), but I somehow missed Crowhursts outstanding thread.

After driving this rig again last night there is, again, no problem about "sway" because of the H/A. Still, it rides nose high with a trailer whose floorplan has all the heavy items and closet storage on or behind the tandem axle; the front of the trailer is quite open and features little beyond some kitchen cabinetry and moveable furniture (original owner did not order either of the two dinette options and minimized overhead cabinetry). We removed the sleeper sofa and some other cabinetry and have reduced axle forward weight by 100-200# that way.

This (I believe at this point) exacerbates the rocking motions which concern me; that the trailer is tail heavy. The stiff rear TV suspension sets it going.
Maybe, just moving to a 4" drop will suffice. We'll see.

The tire inflation is down by 10% from rated max and I noted a 10F difference between the front and rear TT tires on a break at a rest stop. The usual difference (fully-inflated) is about 5F.

I'll be weighing at a Cat Scale south of Waco, TX later this morning, and will provide all the numbers for the Crowhurst calculator. I re-weighed the truck separately yesterday.
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Old 11-01-2007, 09:56 PM   #47
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Allright, weights and measurements on the Silver Streak


Truck, solo

Steer: 4,320
Drive: 3,580
Gross: 7,900
F/R bias: 55/45


TT & TV, 8/10's of W/D max; TT tanks empty

Steer: 4,140
Drive: 4,500
Trailer: 7,460
Gross: 16,100

Truck gross is: 8,640
FF/RR bias: 48/52
Spread is: .9
TW to TV: 740
TW to TT: ??? (140 registered, 240 needed)


Second scale tkt: (yes, amigo, drove off & back around)

Tongue: 980
TT Axles: 7,320
(TW: 13%)
Had to lower tongue 2" to level.

(On some old scale tkts, the rear tandem is experiencing 400-600# bias to the rearmost axle; I am tail-heavy w/o question)


Andy/Inland RV & Nick Crowhurst Q's:

1. Trailer length, hitch center to rear bumper: 35.3'

2. Tongue weight: 980#

3. Tow vehicle wheelbase: 161"

4. Rear spring capacity: 6,000#

5. Rear overhang (axle center to hitch center): 76"

6. Hitch center to TT axle center: 260"

7. Length of bars: 35" +/- (H/A hitch; silvered bars)

Other numbers: Ttl length of combination: 61'
Spread from TV to TT: 64" (body-to-body)


TV specific:

FF end (fenderwell)
Buckled: 35"
Unbuckled: 34.25"

Tires at 63% (50-psi) factory-spec for all loads.

RR: (same)
Buckled: 36"
Unbuckled: 36.25"

Tires at 88% (70-psi) factory spec for MAX load


TT specific:

FF axle (fenderwell)
Buckled: 26"
Unbuckled: 26"

RR axle: (same)
Buckled: 25-5/8"
Unbuckled: 26"

Tires at 100%
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Hensley Arrow. 9-cpm solo, 15-cpm towing
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Old 11-01-2007, 10:11 PM   #48
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ok i'll start b4 those who know get here...

the numbers don't look unreasonable...

it appears that even with the w/d at 8/10th...

your 980 lb tongue has added 920lbs to the drive axle, while reducing the steer axle by 180lbs...

not a great difference on the steer axle or f/r distribution, but still...

now IF the trailer is nose high with the 2 inch drop

isn't a 4 inch drop going to increase the effective tongue mass?

while improving the effect of the spring bars?

also that's without fluids?

how big is the fresh tank and where is it relative to the axles?

did you have lp gas in the bottles?

did you get a ticket with the w/d fully relaxed but still hitched up?

i'm not sure what 8/10s means but tightening the screw jacks up to beyond (by 1") the last mark,

which is the most 'tense' position, moves several hundred lbs on my unit.

cheers
2air'
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Old 11-01-2007, 11:31 PM   #49
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Yes as to changing to a 4" drop, I believe that the w/d will work better. That will be the first change (to order on Monday).

Fresh water tank is over axles; empty on this ticket; full adds 340-lbs.
LP gas 40# bottles are full (aluminum tanks).

No ticket this time with bars backed off; I had two trucks backed up already. Fueling and weighing had already consumed an hour.

8/10's, in this instance, meant I was 2" from case covering shaft; that is, 2' showing on inner portion. I use tape measure all over the place, kinda like that handly little 18V Ryobi drill motor.
(Found an old pair of tkts, different load: notes not great but looks as though an additional 50# was placed on front with max W/D).
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Old 11-01-2007, 11:41 PM   #50
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tail heavy no, but perhaps widely spread...

red'

with the tongue at 13% the trailer isn't really tail heavy, right?

now IF some your heavier gear is way back and way forward, this isn't ideal,

even when the tongue is 10-15%...

i'm no engineer but a widely placed load affects the rotational dynamics and handling negatively, i think.

the haha could mask symptoms of this (yaw) but it isn't ideal.

also with the higher cog on the ss the rotational axis? is important.

a/s do handle better with water on board and most heavy gear stowed near the axles...

that must be true for the ss too...

cheers
2air'
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Old 11-02-2007, 12:26 AM   #51
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Sure, this is a leaf-sprung buggy with shock absorbers (HADCO axles). It rides fairly close to the ground (fully enclosed belly) and the springs have a very short movement. Not as nice as A/S; that I/S is superior without question (except in longevity and maintenance).

The reason I say that it is tail heavy is that all of the "furniture" and appliances and water tanks start at the axles. It is pretty much wall-to-wall floors the first seven feet, and the next seven includes only the kitchen sink/counter. The majority of weight is on or a few feet aft of the axle tandem. Preferably there would have been more furniture forward to offset this rearward bias, but the original owner didn't spec it so.

Yes, 13% looks okay, but remember that is with the trailer leveled, a position it is not riding in. I'm pressing down on the rear axle (you should see tires at rest when hitched, it's obvious) and doubt I am seeing a "proper" amount of tongue weight, especially underway. Yes, the H/A is covering incipient sway. Thus these post requests for help, so I don't leave anything out (and before I get too busy with a new job, etc).

The original REESE hitch rode quite well (level). My truck receiver and the PO's were at the same height. In fact I towed the trailer over 30-miles w/o sway control to see how it would do, and it never jumped me (on my way to Williams Airstream to have H/A installed.) Barely twitched in fact, (similar to some boat/trailer combos of the same weight).

My parents bought their 28' S/S in 1976 or so, and the floorplan, while not as open, was better from the standpoint of weight distribution. All S/S have underfloor tanks, nothing is above the frame. Theirs was easy to tow (used a Cadillac the first twelve years) and never balky. This one is hanging back on me like a tired kid with the current hitch rigging, exacerbating floorplan trade-offs.
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Hensley Arrow. 9-cpm solo, 15-cpm towing
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Old 11-02-2007, 07:30 AM   #52
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The Load Distribution Hitch Calculator calculates the chain tension required to restore the steering axle to its height before the trailer was attached. It does not calculate the higher tension required to put extra weight onto the drive axle. The result after punching in your figures is:

Load Distribution Hitch Calculator

Inputs
W= 161 inches (Wheel base of tow vehicle)

H =76 Inches (Distance from tow vehicle rear axle to hitch ball)

T =980 Pounds (Tongue weight of trailer)

L= 260 Inches (Length of trailer from ball coupling to mid-point of axle system)

B= 35 Inches (Length of load distribution bars)

Outputs
R =1443 Pounds (Extra load on TV rear axle before chains are tightened)

C =463 Pounds (Uplift on front steering axle when trailer is attached but chains not tightened)

Now the chains are tightened to bring the front axle back to its original height :

D =1647 Pounds (Total chain tension required to restore front axle level)

U= 684 Pounds (Reduced loading on TV rear axle caused by chains being tightened)

E= 758 Pounds (Final loading on TV rear axle with trailer attached and chains tightened)

A =222 Pounds Load transferred to the trailer axles

Use at your own risk! (My son, a U.S citizen, tells me I have to add this in the USA!)

The calculator is designed as an aid to understanding what is happening to your rig, rather than dictating what you should do.
Nick.
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Old 11-04-2007, 09:52 AM   #53
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Thank you, NickCrowhurst, for the development of your calculator, and its' application here. (Granted, it's use is as an exercise). I downloaded, but couldn't get it to work.

Given original numbers for the TT at 7,320 (TW 980) I should be seeing ("might" be seeing), once buckled up: 7,542 at the TT axles with the Crowhurst Calc. I am seeing 7,460; a difference of 80-lbs. So, short on rearward transfer.

Using Andy/Inland RV Ctr numbers of 2/3 TW forward, and 1/3 to the TT axles, that TW of 980 would be split: 647# onto the TV, and 323# onto the rear axles (with the TV numbers split near evenly between the FF & RR axles). One-third of 980 = 323#, and I am getting only 140#.


On the TV, with original numbers of 4,320 Steer, 3,580 Drive, I "ought" to be seeing 4,330 on the Drive according to the Crowhurst Calc. I am seeing 4,500 at present. Same as the above, not enough weight transferred onto the TV front axle and TT axle; it's mostly going to the TV drive axle.

With Andy/I-R-C suggestion it ought to be 323# to Steer and Drive axles, approximately (or, @ 3,900 on the drive axle).

At present, nearly all the weight is going to the Tow Vehicle drive axle, no real W/D happening (and I did not have the hitch jacks screwed all the way tight).

I won't be moving again for a couple of weeks (have to get 2" drop stinger swapped for 4" drop as well), so will be back with more work after re-rigging. I'd like to see closer to 50/50 weight distribution on the TV, and see if I can't get the rear-ward weight bias off the TT tandems after some re-arranging of items to the truck bed. I'll be weighing the trailer axles split onto two scale pads this time as well.

I don't quite grasp what the different weight ratings of bars are capable of, but that will be the third set of rig weights after the second obviously needed here.

Am looking forward to more results and am very apppreciative of the help offered here.
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1990 35' Silver Streak Sterling; 9k GVWR.
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Hensley Arrow. 9-cpm solo, 15-cpm towing
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Old 11-05-2007, 12:58 PM   #54
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Rednax, the calculator will not work online unless and until the forum administrator permits the attachment of Excel spreadsheets. I am awaiting a response on that issue. I have today added a relevant post to the Load Distribution Analysis thread. You may find it of relevance to your current quest:
http://www.airforums.com/forums/475541-post61.html
Nick.
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Old 11-09-2007, 07:50 PM   #55
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I have done some re-arranging (re-packing) of trailer storage items to the truck; moved maybe 120# but most of it was from the last two feet of the trailer.

I have confirmed that I have 1,000-lb W/D bars and have ordered a new stinger to drop the hitch ball down to level ( I can understand the dealer having installed it as done; it is a coin flip. But towing it is a different matter than just eyeballing it).

I can't use the .xls spreadsheet, but it sure is good to see it available. I have been reading the referenced thread linked, and am trying to digest what I've read.

I much appreciate the help, as life otherwise is busier than I can describe in a short paragraph; coming home to the trailer and working on this has been a real relief: I feel I have some direction now on fixing what I see as [a] road-ability problem[s]
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Hensley Arrow. 9-cpm solo, 15-cpm towing
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Old 06-26-2008, 06:36 PM   #56
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Ok I promised 2 air I would post my weight findings when I got them.
This is an 01 F350 S/W 7.3liter Diesel Crewcab 8ft bed. 3/4 tank of fuel and abt 35 gal of fresh water on board.Small amount of food and clothing.Blue Tote and misc items in the bed.
Steering <<<<<4120
Drive<<<<<<<<4580
Trailer tandem<<5060
Gross <<<<<<<<13,760
Although the axles are at the end of their life and new axles due to arrive any day ,we find that this balance of weight gives us/the truck and trailer a smooth ride.
It is very important to Use the CAT scale and get the balance correct.
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