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Old 08-26-2012, 06:47 PM   #29
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Yeah man!

Excellent Post Ron!
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Old 08-26-2012, 07:21 PM   #30
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Quote:
Originally Posted by Ron Gratz View Post
The scales data are -- TV only: front axle = 4300, rear axle = 3720
TV&TT attached with no WD: front axle = 3980, rear axle = 4820, trailer axles = 5380, GCW = 14180
TV&TT attached with WD: front axle = 4340, rear axle = 4280, trailer axles = 5560, GCW = 14180
Thanks a lot Ron ! The maths as above clarifies everything and is much more informative that any other posts on WDH I found so far.

If my understanding is correct, the tighter you set the spring bars, the more weight you transfer from the rear axle to the front axle and to the trailer axles. In theory, this weight on rear axle varies from 4820, as in your example when spring bars are not attached, to 0 (zero), when spring bars are set at the tightest position.
What could happen in practice when the spring bars are set too tight and/or front wheels of TV come on the steep ramp or kerb ? Could it result in rear axle lifting off the ground ? If so, then the stress on the hitch attachment point would be immense !
Am I wrong assuming this could happen ?
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Old 08-26-2012, 07:50 PM   #31
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Yes, I think a very tight setting with stiff bars and you could lift the wheels and impart a large force on the trailer. I have seen a hitch head that broke wnen going over a curb at relatively low speed. The torsion bar socket just broke out of the cast iron head. It was on a 1/2 ton ford van, so it was not a really stiff suspension. It probably ran out of travel and was down on the stops when it broke the hitch. It is sometimes suggested to undo the WD bars when pulling or backing into a space with a large incline or level change. It is also suggested to use relatively soft torsion bars with trucks with very stiff suspensions.
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Old 08-26-2012, 09:11 PM   #32
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Quote:
Originally Posted by Timofeevich View Post
If my understanding is correct, the tighter you set the spring bars, the more weight you transfer from the rear axle to the front axle and to the trailer axles. In theory, this weight on rear axle varies from 4820, as in your example when spring bars are not attached, to 0 (zero), when spring bars are set at the tightest position.
What could happen in practice when the spring bars are set too tight and/or front wheels of TV come on the steep ramp or kerb ? Could it result in rear axle lifting off the ground ? If so, then the stress on the hitch attachment point would be immense !
Am I wrong assuming this could happen ?
If we assume that in an extreme situation the load on the WD bars of the example TV/TT could be increased by a factor of four, the load removed from the rear axle via application of WD would be 540*4 = 2160#.

The remaining load on the rear axle would be 4820-2160 = 2660#.

I think it's very unlikely that the load on the rear axle ever could go to zero with a realistic TV/TT combination.

Ron
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Old 08-26-2012, 09:42 PM   #33
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There was a story of a guy who did lift the rear axle with weight distribution some years ago on a front drive Olds Tornado as a demonstration or stunt, then drove it.

doug k
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Old 08-26-2012, 09:52 PM   #34
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There was a story of a guy who did lift the rear axle with weight distribution some years ago on a front drive Olds Tornado as a demonstration or stunt, then drove it.

doug k
EAZ-LIFT did that as an advertising, mainly to sell dealers, and it got great press. Drove it around the country sans rear tow vehicle axle in/around 1968. It is posted elsewhere on this site.
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Old 08-26-2012, 10:36 PM   #35
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Rear axle weight, zero: Post #49

http://www.airforums.com/forums/f463...html#post27393

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Old 08-26-2012, 10:40 PM   #36
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Quote:
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There was a story of a guy who did lift the rear axle with weight distribution some years ago on a front drive Olds Tornado as a demonstration or stunt, then drove it.
Here's a photo of it on page 134: Popular Mechanics - Google Books

The Toronado weighed about 4000# with about 1600# on the rear axle.

The trailer probably was ballasted for zero or negative tongue weight.

A reinforced WDH with extra strong bars would have to transfer about 600# to the trailer's axles to make the rear of the Toronado "float". That's about 2-3 times the normal amount of load transfer but could be done.

Ron
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Old 10-31-2012, 03:04 PM   #37
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Quote:
Originally Posted by Ron Gratz View Post
This is an interesting thread and I think some actual scales data might help to explain how a WDH transfers load to/from all three axles. The data are from a post on another forum RV.Net Open Roads Forum: Towing: Sharing Scale Numbers.

The F-250’s wheelbase is 156.2” and the ball overhang is estimated to be 64” (based on 52.4” rear overhang). The TT is a Jay Feather 29Y. The assumed ball to axles’ midpoint distance is 235”.

The scales data are -- TV only: front axle = 4300, rear axle = 3720
TV&TT attached with no WD: front axle = 3980, rear axle = 4820, trailer axles = 5380, GCW = 14180
TV&TT attached with WD: front axle = 4340, rear axle = 4280, trailer axles = 5560, GCW = 14180

The first two data sets show that TW caused 320# to be removed from the front axle and 1100# to be added to the rear. The indicated tongue weight is 1100-320 = 780#.

In theory, for this TV, the 780# TW would remove 780*64/156.2 = 319.6# from the front axle, and 780*(156.2+64)/156.2 = 1099.6# would be added to the rear.

The 2nd & 3rd data sets show that application of WD caused 540# to be removed from the rear axle with 360# being added to the front and 180# being added to the trailer axles.

In theory, for this TV/TT combination, transferring 180# to the trailer axles would correspond to 180*(64+235)/156.2 = 345# being added to the front axle. And a corresponding load of 180*(156.2+64+235)/156.2 = 525# would be removed from the rear axle.

The net result shown by the scales data is 360-320 = 40# (5.1% of TW) added to the front axle, 1100-540 = 560# (71.8%) added to the rear axle and 5560-5380 = 180# (23.1%) added to the trailer axles.

As for a 1/3, 1/3, 1/3 distribution – it is possible, but quite unlikely. First, you would have to transfer a load equal to 1/3 of the TW to the trailer axles. This requires an unusually high loading of the WD bars. A range of 15-25% is more typical. Second, the distance from the ball coupler to the midpoint between the trailer’s axles would have to be exactly equal to the TV’s wheelbase plus two times the ball overhang. Obviously, this cannot apply to all TV/TT combinations.

Hope this helps,

Ron
Here 'ya go....simple, just post the tickets.




All but 100lbs returned to the steering axle, tv & trl LEVEL.

Can anyone determine the ACTUAL tongue weight?

Bob
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Old 10-31-2012, 03:14 PM   #38
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The tongue weight remains constant and unchanged.
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Old 10-31-2012, 03:15 PM   #39
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It would seem by these numbers that if you put a 400 lb person in the back of your TV you would need a WD ??? Wonder if all those using 1 ton trucks towing without a WD are effected as much by Tongue weight?? I'm Guessing every vehicle is going to be a little different..
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Old 10-31-2012, 04:44 PM   #40
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This discussion about force on the ball being the same no matter what the weight distribution is not true. When you tighten the load bars you are changing the force on the ball in a different direction. The load bars create a moment or torque with the ball as the hinge. The vertical force on the ball turns into forward force as you tighten the bars. If you tighten the bars enough you support the whole tow vehicle and the forward force on the ball is huge. The vertical force turns to zero at that point. The vertical force is taken up by the chains on the load bars and the torque about the ball.

Perry
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Old 10-31-2012, 06:04 PM   #41
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I give up. No matter the explanation, some just can't get it. I think I need to unsubscribe from this thread.
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Old 10-31-2012, 10:13 PM   #42
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All but 100lbs returned to the steering axle, tv & trl LEVEL.

Can anyone determine the ACTUAL tongue weight?


Analyzing the Rob't Cross Lash Up

TW of 13.6% at 1,160-lbs

So, since this rides on the definition of "actual", how was that determined? Best out of three via bathroom scale, SHERLINE scale or drops to the certified scale pad and calculating distance from jack to coupler center, etc?

.
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