Weight Calculations

[klr650goldwing]

My son has a Dutchman (24QB)24' 4500 lb TT. He wants to haul a 300lb motorcycle on the back of the trailer. How much will that motorcycle decrease tongue weight?

[drsteve]

I once tried hauling a 250 lb dirt bike on the bumper of a 23' TT. Caused a sway event that nearly put me in the median. Never again.

[TomG2]

A couple of the guesses are not too far off, but they totally disregard the dynamics of the situation. What happens when things move, bounce and flex as the trailer is towed down the rough highway? Much more complex and beyond the scope of an Internet opinion game.

"Statics is (physics) the branch of mechanics concerned with forces in static equilibrium while dynamics is (mechanics) the branch of mechanics that is concerned with the effects of forces on the motion of objects."

[GrandpaKip]

schlep1967 wrote:

GrandpaKip wrote:
Real world measurement.
I added a cargo rack to the frame of my camper. It weighs 55 pounds. I put 100 pounds on the rack.
All this was done as the tongue sat on a scale with the trailer level.
The weight went down 24 pounds.
So, the tongue weight decreased by about 15.5%.

Let me finish your sentence. So, the tongue weight decreased by about 15.5% of the weight added to the rear of the trailer.

What was the tongue weight (scale reading) before? The 24 pounds divided by that number would be the amount the tongue weight decreased.

You are correct. Thanks for the clarification.
The tongue weight was decreased by 4.1%...24/585
For the OP’s query, he could figure that about 15% of the weight added aft would be removed from the tongue weight. If he added 500# to the rear, it would remove about 75#. To know what the effect would be, he would have to know the trailer and tongue weights.
Of course, this assumes (yeah, I know) that the frame can handle it.

[TomG2]

valhalla360 wrote:
....snip.....
So far no point has been made.

A lot of darts have been thrown but not many points made.

[valhalla360]

JIMNLIN wrote:
LOL..those dimensions won't do any good simply because A 38' triaxle has no center point as in a teeter totter. From the farthest fore and aft spring hangers can be 8-9' apart.
I've made my point to the OP .... I'm done.

Give me the numbers and I'll run the calculations.

Assuming even spacing, the center of the 3 axles is the center point of the axle group.

So far no point has been made.

[JIMNLIN]

LOL..those dimensions won't do any good simply because A 38' triaxle has no center point as in a teeter totter. From the farthest fore and aft spring hangers can be 8-9' apart.
I've made my point to the OP .... I'm done.

[Jebby14]

tongue weight isnt the issue (it can be added back and it will likely only be 50-75 lb reduction anyway). the issue is how is he holding it there? the frame is going to take a pounding as is the bike. put it in the bed.

[valhalla360]

JIMNLIN wrote:

Gooseneck & 5th Wheel trailers have a different geometry from bumper pulls as they are shooting for 20-50% of the weight on the hitch

Looks like your experience with owning and pulling rv and working non rv trailers has been different than mine. Before making claims about my trailers suspensions you need to do some home work prior on what trailers I have and see the different suspension setups out here on non rv trailers. Their not all the same.
My 38' GN triaxle stock trailer and other flatdecks suspensions are set up no different than big 5th wheel/toy haulers for 15-25 percent hitch weights. Even my 18' and 22' bumper pull car haulers suspensions are set up as a TT with 10-15 percent hitch weight. I bought them this way so they can be pulled with a heavy duty 3/4 ton truck.

Your point of non rv trailer suspension set ups has been made before but in the real world not all are as you claim. Sure we have various types of non rv trailers that their suspensions are set farther aft which....but not all are as such.

That 200+ lb was a measured weight number on the hitch from the 2200 lb bull. All my trailers are pulled level.

A teeter totter principle of a center balance point is a poor example of how suspension work on trailers especially with multi axles. Point is adding 300 lbs on the back of the tandem axle trailers rear bumper won't make the hitch weight lessor the same amount.

The actual suspension system doesn't make much difference unless you get wildly out of level in terms of calculating the hitch weight. If it's running level and there is nothing wrong with the suspension, the weight should be pretty close to evenly distributed between the axles and the teeter totter analogy still applies.

Give us the dimensions on your cattle trailer including the position of the bull. I'll give you 1000-1 odds, the calculations make it quite obvious why you saw only 200lb come off the hitch with no consideration of the suspension type only the spacing between the center line of the axles and the hitch/bull.

[schlep1967]

GrandpaKip wrote:
Real world measurement.
I added a cargo rack to the frame of my camper. It weighs 55 pounds. I put 100 pounds on the rack.
All this was done as the tongue sat on a scale with the trailer level.
The weight went down 24 pounds.
So, the tongue weight decreased by about 15.5%.

Let me finish your sentence. So, the tongue weight decreased by about 15.5% of the weight added to the rear of the trailer.

What was the tongue weight (scale reading) before? The 24 pounds divided by that number would be the amount the tongue weight decreased.

[GrandpaKip]

Real world measurement.
I added a cargo rack to the frame of my camper. It weighs 55 pounds. I put 100 pounds on the rack.
All this was done as the tongue sat on a scale with the trailer level.
The weight went down 24 pounds.
So, the tongue weight decreased by about 15.5%.

[JIMNLIN]

Gooseneck & 5th Wheel trailers have a different geometry from bumper pulls as they are shooting for 20-50% of the weight on the hitch

Looks like your experience with owning and pulling rv and working non rv trailers has been different than mine. Before making claims about my trailers suspensions you need to do some home work prior on what trailers I have and see the different suspension setups out here on non rv trailers. Their not all the same.
My 38' GN triaxle stock trailer and other flatdecks suspensions are set up no different than big 5th wheel/toy haulers for 15-25 percent hitch weights. Even my 18' and 22' bumper pull car haulers suspensions are set up as a TT with 10-15 percent hitch weight. I bought them this way so they can be pulled with a heavy duty 3/4 ton truck.

Your point of non rv trailer suspension set ups has been made before but in the real world not all are as you claim. Sure we have various types of non rv trailers that their suspensions are set farther aft which....but not all are as such.

That 200+ lb was a measured weight number on the hitch from the 2200 lb bull. All my trailers are pulled level.

A teeter totter principle of a center balance point is a poor example of how suspension work on trailers especially with multi axles. Point is adding 300 lbs on the back of the tandem axle trailers rear bumper won't make the hitch weight lessor the same amount.

[valhalla360]

JIMNLIN wrote:
I've loaded several hundred GN/pintle hitch flatdeck and stock trailers and was always surprised how small the percentage was of adding a load on the azz end of the trailer and changes hitch weight.
First off the center of the axles doesn't work like a teeter totter #1 because one end sits on the trucks hitch. #2 can be distance behind the last axle spring hanger and #3 is the distance from the hitch to the first axle spring hanger. Without seeing the trailer I wouldn't guess a weight.

Loading a 21000 lb 38' GN tri axle stock trailer with young stuff....cows...and big mature bulls is a guessing game. I know adding the 2200 lb bull in the last stall didn't change the weight on the ball by a quarter of a inch = approx 200+ lbs.

Adding 300 lbs on the rear bumper of a small TT IMO can make a ill handling combo.

Assuming you keep the trailer reasonably close to level, the weights do transfer like a teeter totter:

#1 The teeter totter is purposely out of balance with the front end longer than the back end. This would be like putting a 10ft arm on one side and a 5ft arm on the other end...to keep the teeter totter level, you would need a lifting force (ie: hitch weight) under the rider on the long end.
#2 & #3 Unless The trailer is wildly out of level, this won't have an impact as the springs will give pretty closely approximating a central pivot point.

Gooseneck & 5th Wheel trailers have a different geometry from bumper pulls as they are shooting for 20-50% of the weight on the hitch (semis are typically around 50%). This means the trailer wheels are set much further back typically. As a result, the moment created by a weight put way at the back has far less impact on the pin weight.
- Bumper pulls travel trailers tend to have the wheels centered 55-60% of the length back from the hitch. So weight placed a few feet behind the rear bumper will tend to remove 80-100% of that weight from the hitch.
- 5th Wheels tend to be 65-75% back from the hitch. This will result in a similar weight removing 30-60% of the weight from the hitch. Add in that the hitch weight is much higher to begin with and you can absorb more weight without significant impact on the handling. On a lot of commercial GN trailers, the trailer axles may be 80-90% back and it may only remove 5-20% off the hitch (hence your 2000lb bull example)

[JIMNLIN]

I've loaded several hundred GN/pintle hitch flatdeck and stock trailers and was always surprised how small the percentage was of adding a load on the azz end of the trailer and changes hitch weight.
First off the center of the axles doesn't work like a teeter totter #1 because one end sits on the trucks hitch. #2 can be distance behind the last axle spring hanger and #3 is the distance from the hitch to the first axle spring hanger. Without seeing the trailer I wouldn't guess a weight.

Loading a 21000 lb 38' GN tri axle stock trailer with young stuff....cows...and big mature bulls is a guessing game. I know adding the 2200 lb bull in the last stall didn't change the weight on the ball by a quarter of a inch = approx 200+ lbs.

Adding 300 lbs on the rear bumper of a small TT IMO can make a ill handling combo.

[CavemanCharlie]

MFL wrote:
Back of a TT??? NOPE...tell son to forget that idea! Best look at other options.

Jerry

I agree.