Tongue Weight - How To Measure - Page 10 - Escape Trailer Owners Community

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Old 03-13-2013, 01:02 AM   #91
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Quote:
Originally Posted by Dixhiccup View Post
No Hotfishtacos, it rained yesterday, today and is forecast for the next three days. Re #49. I stopped reading when it was said that raising the tongue changed the tongue weight. I figured that would only happen if the wheels were chocked and couldnt move. I thought that, in order for the tongue to be raised vertically the wheels would have to be free to move slightly in reverse which would result in no weight movement. This took into account that the driveway sloped toward the road and you backed the trailer in. Of course I was thinking of a single axle unit. Maybe I read things differently. Cheers, Richard
One of the critical factors in the analysis is the location of the Centre of Gravity (C of G) of the trailer. The higher it is above the frame the greater the effect towing above or below level will have (statics 101 analysis).

When you tow a trailer tilted up from level the C of G effective horizontal distance moves slightly back towards the axle and results in a decrease in tongue weight from that at level trailer. Tilt the tongue below level and the C of G distance effectively moves forward and increases the tongue weight while towing in the that position.

Think of a loaded wheel barrow which is most like a single axle trailer setup. Picture the C of G being centered between the wheel axle and the handles and 2 ft above the handles then lift and lower the handles above level and see what happens to its horizontal location relative to the axle. In the worst case if you rotated upwards 90 deg the weight on the handles would be zero. Rotate 90 deg down and the total weight would be on the handles.

I agree with those who have stated that a single axle trailer, level, on sloping ground will give the same tongue weight as towing a level trailer, on level ground. The ground slope has no effect on vertical forces or vertical reactions. The chocks and friction resist any horizontal forces, due to slope, and you only have the vertical forces left, as Jim B stated, and you then measure only vertical tongue weight in a level position - the desired outcome if you tow level.

Towing up or down a hill is another analysis, although similar, from determining tongue weight with a level trailer. Once again it is the C of G that accounts for the weight shift. Your level trailer is still parallel to the road but the whole setup is on a slope and the effective horizontal distance to the C of G has again changed.

So pack your heavy stuff on the floor and light stuff up high to keep the C of G as low as possible. If all the mass of a trailer were only in the frame then the tilt effect would be very minimal.

That is my 5 cents worth that I had to get in before they take our nickel away as well.

Now back to the squeegee for me to get the rain off the deck!!!

Can't wait for it to warm up and the sun to come out so we can get out there and camp in t-shirts and shorts. Figure that one out, eh!
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Old 03-13-2013, 01:32 AM   #92
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All that, and thank you, explains why when I was moving a 400 lb. boulder on a dolly, and the C of G shifted, that I got fired over the dolly handles and into the fence on the other side.
No damage to me, fortunately, and I decided that the placement of the boulder in my rock garden was just perfect.
There is always a solution.
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Old 03-13-2013, 01:36 AM   #93
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I'm out of this. It seems to me that Baglo stated early on I.e #17 that his is a 17 single axle & the next ten or fifteen posts went slightly off track or agreed with him. He stated he had used blocks to get his 17 level and then raised the tongue about 1/4" so there couldn't have been any appreciable change in tongue weight or c of g. Thereafter things seem to go off the rails and it became very confusing with all the different views of the apparent problems. Glen I just read my next post, seems you had someone on your side. Now I'm going to put my grand daughters engine back in her toy box. Cheers, Richard
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Old 03-13-2013, 01:45 AM   #94
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Nothing left on the bone.
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Old 03-13-2013, 02:03 AM   #95
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Here is an example.

Trailer: 15’ Escape, total mass 2500 lbs. loaded
Tongue weight: 300 lbs. or 12%, level trailer
Assume C of G is 3 feet above frame, vertical distance.
Distance from axle to hitch: 10 ft. as measured
Assume axle and hitch are on the same plane and no friction in system
Calculated C of G: 1.20 ft. ahead of axle, horizontal distance

Assume hitch point is 3 inches above level.
Trailer slope = 1.4321 deg. or 2.5%
Calculated new horizontal location of C of G is 1.1246 ft. (shift 0.0754 ft. or 0.9 inches back)

Calculated tongue wt. tilted = 281.2 lbs. or 11.25% of trailer mass (18.8 lbs. less)

The values for a 17 ft. trailer would be nearly the same based on same weights and a 2 foot longer distance from axle to hitch and new horizontal C of G calculated.

The tongue weight value for 3 inches lower would be 318.7 lbs or 12.75% of trailer mass.

3 inches above or below level is a lot I believe, with small change in tongue weight? Problem

Please comment if you agree or do not agree with my static calculations.

Has anyone actually measured tongue weights to compared level vs. sloped?

I know Glen would love to go out and do it but he is probably tired of setting up and there is more rain in the forecast! Time for an Okanagan Spring, beer eh.
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Old 03-13-2013, 02:05 AM   #96
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I have been following this forum for a month or so, and decided to jump in on this thread with my two bits (skipping from pennies, right past nickels and dimes). The forces and weight distribution on the wheel may differ depending on the slope of the surface, and also the addition of wheel chocks and blocks. However the weight transfer from the wheel to axle and axle to trailer frame should not vary because of the slope of the surfaces supporting the wheel. So, the remaining trailer weight (the tongue weight), also will be constant, whether it is supported on a pedestal the same height as the trailer wheel or not.

Now, if the scale measuring the tongue weight is not vertical (if it is not sitting on a level surface), then the scale will not show an accurate measurement - it will be measuring diagonal forces. Here is something else for all of us closet physicists to consider.

Baglo's tongue scale set up appears to be on the level, so should be accurate.
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Old 03-13-2013, 02:08 AM   #97
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I have a solution ... of water, malt, sugar and hops. Oh ya, yeast.
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Old 03-13-2013, 02:18 PM   #98
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Quote:
Originally Posted by gbaglo View Post
Nothing left on the bone.
Hopefully it will not be a three dog night on top of the rain.
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Old 03-13-2013, 04:43 PM   #99
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Quote:
Originally Posted by JohnB View Post
...Assume C of G is 3 feet above frame, vertical distance
...
Assume hitch point is 3 inches above level.
Trailer slope = 1.4321 deg. or 2.5%
Calculated new horizontal location of C of G is 1.1246 ft. (shift 0.0754 ft. or 0.9 inches back)

Calculated tongue wt. tilted = 281.2 lbs. or 11.25% of trailer mass (18.8 lbs. less)
Since the single-axle trailer is sitting on a wheel which rotates on a hub when the trailer is tilted (not a leg extending to the ground at the tire contact point, and nothing to do with the frame height), I believe that the relevant height for the shift calculation is the height of the C of G above the axle, not above the ground or the frame. If the C of G were right at the axle height the shift with small angle change would be entirely vertical - no horizontal shift or tongue weight change at all. Although the real C of G is well above the axle, this still means that the effect is small - I don't think it's a big deal for single-axle trailers of a reasonable height.

I did check this experimentally with my single-axle Boler and a scale; unfortunately it was years ago and I do not recall the numbers.
I checked with a tandem-axle cargo trailer that I had rented, and the larger (and opposite direction) load shift for even 2 inches of hitch height change was significant.

Quote:
Originally Posted by KirkB View Post
The forces and weight distribution on the wheel may differ depending on the slope of the surface, and also the addition of wheel chocks and blocks. However the weight transfer from the wheel to axle and axle to trailer frame should not vary because of the slope of the surfaces supporting the wheel. So, the remaining trailer weight (the tongue weight), also will be constant, whether it is supported on a pedestal the same height as the trailer wheel or not.

Now, if the scale measuring the tongue weight is not vertical (if it is not sitting on a level surface), then the scale will not show an accurate measurement - it will be measuring diagonal forces. Here is something else for all of us closet physicists to consider.

Baglo's tongue scale set up appears to be on the level, so should be accurate.
I agree with all of this! Despite all the flak we have given him for complicating things, in his situation it is perfectly valid to prop up the tongue to get a correct tongue weight measurement and confirm appropriate loading before a trip.
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Old 03-14-2013, 12:14 AM   #100
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What are we going to do without Toad On A Slope to talk about? Sounds like a drink. I'll have to come up with some concoction!

I appreciate Doug having started the thread and Glenn's question as such threads are always a learning experience or at least a little refresher course for the experts. We do not, however, have any real world examples with numbers. That would be good to get. I have never seen an instruction to get tongue weight except on a level surface but I guess I want to include slopes now!

I still suggest what I always suggest in such a case, namely, that a person becomes familiar with his own situation by doing the numbers. It is rare that scientific or engineering claims can be checked but TWs can be done easily. We apparently do still have some unresolved points. Might as well check on them to make sure.
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