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Old 06-13-2013, 06:54 PM   #1
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I don't have a Sherline scale and don't want to spend $150 on one, and I don't like the bathroom scale method (seems way too prone to variation). So I'm wondering if this would work:

1) pull TV on to cat scale with TT connected BUT trailer axle NOT on the platform.
2) track weight - let's say it's 6000 lbs
3) drive off the scale and disconnect the TT
4) weigh the TV on the cat scales alone - let's say it weighs 5000 lbs
5) tongue weight = step 2 (6000) - step 4 (5000) (or 1000 in this example)

Is this an accurate way to calculate tongue weight? Are there other ways to calculate it without a dedicated scale or bathroom scale/boards/pipes?

Thanks!

Edit - this is based on a recommendation I found on a web search - not an original idea on my part...
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Old 06-13-2013, 07:12 PM   #2
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Steve,

You got it!!

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Old 06-13-2013, 07:23 PM   #3
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That feels more trustworthy than an unattributed wiki answer :-)
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Old 06-13-2013, 07:49 PM   #4
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When I weighed my trailer and truck I made several passes on the scale. For a true tongue weight I lowered the tongue on one pad with the wheels on the 2nd. I able to position it so that all I had to do was unlatch the hitch and raise it off the ball because I had the truck wheels off the front scale pad. Gives direct reading. I did go at a time that they were not busy and before doing the first weight I went inside and told the attendant what I wanted to do. I weighed the combo, the truck alone and finally the trailer alone. They were glad to help and the 2nd and 3rd weights only cost a small amount.
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Old 06-14-2013, 08:39 PM   #5
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I've done mine this way. But the jack and the ball receiver are not in the same postiion, therefore this is NOT the TW but an approximation that may be off 5-10%. PM Ron Gratz and ask how to correct for this.

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Old 06-14-2013, 08:44 PM   #6
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Quote:
Originally Posted by slowmover
I've done mine this way.

.
Are you referring to 68's process or the one I asked about in the original post? Just want to clarify.

I've thought about that problem too. I think you're supposed to weigh at the coupler/ball (not the jack) if you're using the Sherline or bathroom scale procedure. But with the PP, you isolate the coupler/ball and have a trapezoid box to work with - so where are you trying to weigh from?

This is why I want to try the procedure mentioned in the original post. It seems like I'm going to get a fairly accurate weight but what the heck so I know? :-)
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Old 06-15-2013, 03:40 AM   #7
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Quote:
Originally Posted by SteveSueMac View Post
I don't have a Sherline scale and don't want to spend $150 on one, and I don't like the bathroom scale method (seems way too prone to variation). So I'm wondering if this would work:

1) pull TV on to cat scale with TT connected BUT trailer axle NOT on the platform.
2) track weight - let's say it's 6000 lbs
3) drive off the scale and disconnect the TT
4) weigh the TV on the cat scales alone - let's say it weighs 5000 lbs
5) tongue weight = step 2 (6000) - step 4 (5000) (or 1000 in this example)

Is this an accurate way to calculate tongue weight? Are there other ways to calculate it without a dedicated scale or bathroom scale/boards/pipes?

Thanks!

Edit - this is based on a recommendation I found on a web search - not an original idea on my part...
In step 1 you need to make sure you do not have any tension on the WD bars or part of your tongue weight will be shifted to the TT axles.

The process you describe is the one I use. It seems logical to me.
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Old 06-15-2013, 04:50 AM   #8
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Quote:
Originally Posted by Ridgerunner3

In step 1 you need to make sure you do not have any tension on the WD bars or part of your tongue weight will be shifted to the TT axles.
Thanks, Ridgerunner3. I would have missed that completely! Makes perfect sense!

I'm hitting the scales later today and will report back :-)
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Old 06-15-2013, 01:57 PM   #9
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Ok. First a story. On the way to the scales, there was a traffic jam on the highway due to an accident. I was in the far right lane and we all had to merge left. No one wanted to let me in of course. But this guy in an Explorer pulls up aside me and tells me to roll down my window. I do and he says, "only because you're driving an Airstream, I'm gonna let you in. Nice ride!"

Benefits all over the place. Ok. Next post is the data.
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Old 06-15-2013, 02:15 PM   #10
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Old 06-15-2013, 02:19 PM   #11
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Here's the data table:

Click image for larger version

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The table is self explanatory. Using the procedure in the original post (with Ridgerunner3's advice re: no WD) I get 8740 for the truck w/trailer connected but trailer not on scales, minus 7900 for truck by itself on scales for 840 tongue weight.

First question: is that static no matter how much WD I apply?

Note: CGVW of TV and TT is 14740. That minus TV of 7900 suggests the TT weighs 6840. But even with 0 WD applied, the TT axle weighs in at 5760 (a difference of 1080# and 240# off from calculated tongue weight). The steer and drive axles of the TV weigh in at 8980 and the difference there is 1080 from the truck alone. So where does the 840 tongue calculation fit in??

Rest of the table shows the weight across all 3 cat scales with 0", 5", and 6" of WD applied to the PP via the WD jacks (inches measured from top of a-frame to bottom of jack sleeve on the PP). Note to Sean - have you thought of including a ruler on the inside of the jack sleeve?? :-)

With 0" of WD applied, 500# are lifted off the steer axle.

Second question: when calculating FALR, is the denominator 500# and the numerator the difference in lift of the steer axle from 500# or is the 4620 steer axle weight (truck alone) the denominator and the cat scale steer weights the numerator? I ask because in the former method, 6" gets me 56% FALR (280/500). In the latter method, I get 95% FALR (4400/4620).

I have a bunch of data but am unclear how to analyze what it's telling me. Any thoughts??

Also, I imagine my set up to be this huge beast of a thing on the highway. Here I am parked between a couple of real trucks at the cat center. My rig looks like a puppy in comparison. :-)

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Old 06-15-2013, 03:09 PM   #12
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Quote:
Originally Posted by SteveSueMac View Post
Here's the data table:

Attachment 188308

The table is self explanatory. Using the procedure in the original post (with Ridgerunner3's advice re: no WD) I get 8740 for the truck w/trailer connected but trailer not on scales, minus 7900 for truck by itself on scales for 840 tongue weight.

First question: is that static no matter how much WD I apply?

Note: CGVW of TV and TT is 14740. That minus TV of 7900 suggests the TT weighs 6840. But even with 0 WD applied, the TT axle weighs in at 5760 (a difference of 1080# and 240# off from calculated tongue weight). The steer and drive axles of the TV weigh in at 8980 and the difference there is 1080 from the truck alone. So where does the 840 tongue calculation fit in??

Rest of the table shows the weight across all 3 cat scales with 0", 5", and 6" of WD applied to the PP via the WD jacks (inches measured from top of a-frame to bottom of jack sleeve on the PP). Note to Sean - have you thought of including a ruler on the inside of the jack sleeve?? :-)

With 0" of WD applied, 500# are lifted off the steer axle.

Second question: when calculating FALR, is the denominator 500# and the numerator the difference in lift of the steer axle from 500# or is the 4620 steer axle weight (truck alone) the denominator and the cat scale steer weights the numerator? I ask because in the former method, 6" gets me 56% FALR (280/500). In the latter method, I get 95% FALR (4400/4620).

I have a bunch of data but am unclear how to analyze what it's telling me. Any thoughts??

Also, I imagine my set up to be this huge beast of a thing on the highway. Here I am parked between a couple of real trucks at the cat center. My rig looks like a puppy in comparison. :-)

Attachment 188309
At first look I see a calculated tongue weight of 1080#. I need to carefully look at all of data again. We're all of these weights taken on the same trip today?
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Old 06-15-2013, 03:11 PM   #13
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Steve,

Your TV alone steering weight is your target, 4620. Ideally you'd want to transfer that remaining 220lbs, with a level rig. We are 100lbs light and our rig tows fine.

Btw...I marked the HAHA jack with a file at 1" increments, then noted them for different loads.

What's all this FALR stuff? Front axle load rating, should be on the driver door jamb sticker. FALRatio?...I wouldn't worry, get within 100 and you should be fine, why make it more complicated than it needs to be.
Just scan the CAT tickets and post them.

Remember the TV and AS must be level with WD set.

Bob
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Old 06-15-2013, 03:27 PM   #14
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Quote:
Originally Posted by Ridgerunner3

At first look I see a calculated tongue weight of 1080#. I need to carefully look at all of data again. We're all of these weights taken on the same trip today?
Yes, Ridge. All within about 90 minutes.
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Old 06-15-2013, 03:35 PM   #15
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Bob - thanks - FALR = front axle load restoration.


Here are the pics of the tix :laff: in the order I did them.

W/6" WD on the jacks:

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With 5" on the jacks:

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With 0" on the jacks: (and it bottomed out coming off the scales :dang:

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TT attached, 0" WD, only truck axles on a single portion of the scale:

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Disconnected TT and TV alone on drive and steer scales:

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Those are the numbers I put in the table earlier an I included a column for max allowed values for each axle and tongue weight.
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Old 06-15-2013, 04:05 PM   #16
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Steve,

Any more left on the jacks?
It would be good to get at least another 100lbs to the front.

How did it tow?
Are you level?, especially the AS.

Bob
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Old 06-15-2013, 05:25 PM   #17
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Bob - I think I can get to 7" on the jacks. I'm also thinking I REALLY should have followed Sean's advice and ordered the 1400# bars not the 1000. My AS manual said the TW shouldn't go above 1000 - or in any case - not to exceed the hitch manufacturer's limit (1500 in my case).

Towed well and the trailer is almost perfectly level at all 4 corners.
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Old 06-15-2013, 05:30 PM   #18
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I may not be calculating tongue weight correctly. I weigh the TV with each axle on a different pad. I then weight the TV and TT with no tension on the WD bars. I then sum the weight of the truck axles alone. Then I sum the truck axles with TT attached and no WD tension. I then subtract lone TV weight from the TV weight with TT w/o WD tension to calculate tongue weight. This would be 1080# for your rig by the method I use. I may be using the wrong process. I hope someone chimes in on my process for calculating tongue weight.

My rig (propride 2012 GM 2500 & 6300# 25 footer) is more comfortable to me when I do not return all of the front axle to the TV.
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Old 06-15-2013, 05:37 PM   #19
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Great Job!!

Try it at 7" first. You'll get a softer ride with them. I have 1000's on our 2500 Burb and they work fine. I can max them out and get that 100lbs forward, but the ride is better and and everything's level without.


Now about the possible water leak. Boy you'd think with it leaking that quickly there would be a LOT on the ground. I know when I drain the FW thru the pet-cock it takes a good long time to empty a full tank.

RR3,

1080 is my TW for Steve's rig also. That seems more in line with my 1200 for our Classic using the SL scale.

Bob
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Old 06-16-2013, 11:05 AM   #20
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Originally Posted by SteveSueMac View Post
---I get 8740 for the truck w/trailer connected but trailer not on scales, minus 7900 for truck by itself on scales for 840 tongue weight.
In one of the ticket captions, you mentioned dragging when coming off the scale. That indicates a down slope at the exit and, probably, an up slope at the entrance. If so, the TV would have been higher than the TT and the TT tires might have been on the up slope. This would make it difficult to make much sense of the TV weight of 8740#. I recommend we disregard that weighing to reduce the confusion.

Quote:
First question: is that static no matter how much WD I apply?
If the tongue weight is properly determined, it should remain constant unless the trailer loading is changed.

Quote:
Note: CGVW of TV and TT is 14740. That minus TV of 7900 suggests the TT weighs 6840. But even with 0 WD applied, the TT axle weighs in at 5760 (a difference of 1080# and 240# off from calculated tongue weight). The steer and drive axles of the TV weigh in at 8980 and the difference there is 1080 from the truck alone. So where does the 840 tongue calculation fit in??
As stated above, I think it would be good to disregard the "840 tongue calculation". IMO, the 1080# value is a better estimate, but I'll say more about that later.

Quote:
Second question: when calculating FALR, is the denominator 500# and the numerator the difference in lift of the steer axle from 500# or is the 4620 steer axle weight (truck alone) the denominator and the cat scale steer weights the numerator? I ask because in the former method, 6" gets me 56% FALR (280/500). In the latter method, I get 95% FALR (4400/4620).
FALR is the amount of load restored to the front axle via application of WD (4340-4120=220# for 5") divided by the amount of load removed when the TT was initially attached (4620-4120=500#). The FALR for 5" is 220/500 = 44%. The FALR for 6" is (4440-4120)/500 = 56%.

More later --

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