Loading and balancing the trailer - R-pod Owners Forum

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Olddawgsrule View Drop Down

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Joined: 20 Sep 2017
Location: New Hampshire
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Topic: Loading and balancing the trailer
Posted: 28 Oct 2019 at 4:38pm

I do believe I finally have the spreadsheet running correctly. If anyone wishes 'proof' it I will happily pass it along for so.

I do not wish to pass it Publicly until it's been proofed and 'all' agree. There's enough BS out there, as I do not wish this to become part of, I feel we need something that actually shows/works.

At this point the math will show what leaving a full beer on the counter means.. That is if you measure correctly and weigh correctly.

Those interested, contact me.

Byways no Highways
2017 Tacoma
Truck Camper Build
2004 F150 My Overlander

Olddawgsrule View Drop Down

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Location: New Hampshire
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Posted: 26 Oct 2019 at 4:18pm

Originally posted by mjlrpod

I use the "pack whatever stuff I want and go" formula. So far Ive had no trouble. Smile

Luckily I can carry alot in the camper, and in the bed of the truck.

Hear ya, I did somewhat the same, yet hit the scales before I left. I just needed to know.

With what I just went through with my frame, I needed to know more. With this spreadsheet I can say what I have without doubt. What I do see was I was heavy on the tongue a bit, yet still light on the axle.

I built this spreadsheet for me. Ya, selfless and self bearing. Hopefully it can help another. This is part of understanding why my frame not only bent, but fractured. I weighed in at 3200 lbs at most on departure, yet mis-factored my tongue weight. I don't believe that caused the issue yet still working through understanding all parts of this. I truly don't wish anyone to go through what I have if it's preventable.

Mounting a bike rack up front, going to dual 6's, adding that second propane tank, carrying whatever/where-ever does mean quite a it. It amazed me how much it means.

What happened to me, as I'm seeing, was not a singular incident. Situations, bumps, whatever's accumulating to the result. I believe now it is so important to know what you carry, what it's doing and how to place it.

Just me.. MHO... Wishing no one else goes through what I did.

Byways no Highways
2017 Tacoma
Truck Camper Build
2004 F150 My Overlander

mjlrpod

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Joined: 27 Sep 2016
Location: Massachusetts
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Posted: 26 Oct 2019 at 3:49pm

I use the "pack whatever stuff I want and go" formula. So far Ive had no trouble. Smile

Luckily I can carry alot in the camper, and in the bed of the truck.

2017.5 Rp-172
2020 R-pod 195
2015 Frontier sv 4.0L 6cyl
I'll be rpodding

Olddawgsrule View Drop Down

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Location: New Hampshire
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Posted: 26 Oct 2019 at 11:41am

Just returned from the scales. Saturday is the only day they us locals to come by and weigh. It's quite busy there on weekdays (scales anyway).

Wow, did I over-estimate my base weight.. My weight on axle was lower than what I estimated the base at.. Anywho, all is good now with 'real' base numbers! This is partially loaded. First section is actual weights, second section is the math.

The Scales!	Truck hitched	5220	Trailer total weight	3200
	Truck n Trailer	7980	Trailer axle weight	2760
	Trailer hitched	2760	Tongue weight	440
	Truck alone	4780

I will continue to weigh as I finish loading, yet I can see where I'm headed now. About 3100#'s on the axle and 475#'s on the hitch.

Here's where my curiosity on switching to lithium comes in for me. The weight savings allows me to put the bikes on the trailer (where the batteries were) and puts me right at 3K on the axle and 435#'s on the hitch. And I still have 100ah capacity!! Win, win!

Byways no Highways
2017 Tacoma
Truck Camper Build
2004 F150 My Overlander

Olddawgsrule View Drop Down

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Posted: 19 Oct 2019 at 2:18pm

Ran to the dump in hopes of returning and hitting the scales.. Way too busy after the Nor'easter we went through. I will go Monday and confirm base weight.

What I really like about the spreadsheet, is I can work items into places and see the effect on both the axle & the tongue. I am having fun with this and loading accordingly.

I have decided that the dual 6v's are coming off and my small lithium (40ah) issuing in the camper as house power. So I ran numbers..

The spot I've chosen is the compartment of the water & trailer heaters. I have space there. Though now is I could easily buy another (when the sale happens) and double up to 80ah. I'd be very happy with that!

Next is the spare is now in the camper (instead of the truck bed) and under the rear bunk (182g here). With the batteries of the hitch frame, I can now get my bike there (which I've always wanted to bring along).

With all these changes, I fall right into where I hoped to be. 420lbs on the hitch & 3320lbs on the axle. 12% hitch weight! I put just my Curt Sway (maybe even sell my E2 WDH) and I'm rock n rolling again with even more cargo space in the TV!

Byways no Highways
2017 Tacoma
Truck Camper Build
2004 F150 My Overlander

offgrid

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Posts: 5290

Posted: 18 Oct 2019 at 5:15pm

Originally posted by Olddawgsrule

Being hard for me to understand how the 107lbs come back into play again, I used the math you have shown me. Load (253lbs) x distance to axle (66") / Distance to hitch (156"). That solves at 107lbs.

What I have just learned is that by counter-balancing I'm placing the full weight of the object on the axle. Guess I should have realized that, yet hoped it would not.

"What is your Taco's hitch weight limit? Do you really need to keep the hitch weight down to 420 lbs?"

650lbs. This exercise is to show me what and where. I do believe I carry approximately 200+lbs aft of axle. I will discover how much and where I actually carry. At 400-420lbs I have no requirement for WDH. So ya, I'd like to keep it in that range. Will it end up there? Only completing this exercise and knowing what I have can I make that decesion.

107 lbs of trailer weight isn't "coming back", it never went away. If the total trailer weight goes up 253 lbs and the hitch weight goes down 107 lbs (because we fooled with the moments around the axle) then the axle weight goes up 360 lbs. Has to or we would be destroying 107 lbs matter, which Einstein says we can't do without creating one heluva big explosion (about 1000 megatons if I did my math right) Star

If you have 650 lb capacity on the Taco I highly recommend that you let it take some more tongue load rather than put that onto the relatively weak trailer frame and axle. If you end up wanting a wdh to help the truck ride better then that won't hurt anything.

1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Olddawgsrule View Drop Down

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Posted: 18 Oct 2019 at 2:37pm

What I really like about this is not only can you see what is happening, yet work out options of placement of goods and the results.

The biggest thing 'I' see immediately, is working on my battery base! It changes so much so quickly!

I have a 38ah lithium that I do use, yet working out how to make it 'house' on the tongue and larger capacity elsewhere.. Hmm.. Now I can play with this and 'know' what the results could be.

But that's another thread!

Byways no Highways
2017 Tacoma
Truck Camper Build
2004 F150 My Overlander

Olddawgsrule View Drop Down

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Posted: 18 Oct 2019 at 2:28pm

Getting very close and being able to really look at things now. I have almost everything back, short of a few lighter items which I will do and add. What I hope is you take a look and offer suggestions of improvement.

First up is my results of of now.

Next is a sample of fore axle item

Then a aft axle item

Still need to work coloring of cells.. Yellow being input cells, light blue as informative and green as important results.

I found that if I inputed 'aft' of axle as a negative, the formula's worked. Yet still required inverting to positive in one of the result cells. I'll work on that formula so that's not required.. Actually didn't think of how till I wrote this.. Ya, for me I have to write things out to 'see' what I need to do.

Anywho. You can see where I'm at and got there fairly quick. Results section is the most important to me! 400lbs of items, placed accordingly and I have 619lbs on the axle. WOW! I going to hookup tomorrow and run to the dump and hit the scales. Really need at this point to factor a correct baseline. Right now I have my baseline at 2800lbs (remember, I was stripped further tan what factory calls empty).

More to come!

Byways no Highways
2017 Tacoma
Truck Camper Build
2004 F150 My Overlander

Olddawgsrule View Drop Down

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Posted: 18 Oct 2019 at 8:34am

Originally posted by offgrid

I think your 107 lbs and 253 lbs are correct if I understand your spreadsheet right. But you need to also consider the effect of the 253 lbs on the axle (and on the frame aft of the axle). I think if you add the 253 lbs 66 inches behind the axle you are increasing your axle load by 360 lbs (253 lbs plus the reduction in hitch load of 107 lbs). That's a LOT of extra weight/stress on the axle/stress on the frame to carry around.

What is your Taco's hitch weight limit? Do you really need to keep the hitch weight down to 420 lbs?

I don't have a handle on the side to side weight distribution on the axle. I do agree that the slide side is almost certainly heavier, numerous ppl have noticed that that side rides lower on their pods, and its my impression that there have been more axle failures on that side. The thing that is needed is for someone to actually measure their side to side weight balance. That's not so easy. It could be done with individual wheel scales or (maybe) with a Sherline with a board on top using legos to get each trailer wheel on there one at a time.

"But you need to also consider the effect of the 253 lbs on the axle (and on the frame aft of the axle). I think if you add the 253 lbs 66 inches behind the axle you are increasing your axle load by 360 lbs (253 lbs plus the reduction in hitch load of 107 lbs)."

Okay, I need to write this out to understand..

Will deleted the long write up and here's the short version:

Being hard for me to understand how the 107lbs come back into play again, I used the math you have shown me. Load (253lbs) x distance to axle (66") / Distance to hitch (156"). That solves at 107lbs.

What I have just learned is that by counter-balancing I'm placing the full weight of the object on the axle. Guess I should have realized that, yet hoped it would not.

"What is your Taco's hitch weight limit? Do you really need to keep the hitch weight down to 420 lbs?"

Byways no Highways
2017 Tacoma
Truck Camper Build
2004 F150 My Overlander

offgrid

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Posted: 18 Oct 2019 at 5:52am

I'll trade you your next snowfall for my next tropical storm if you want. LOL

Here's a thought experiment that hopefully will make it easier to understand what's going on with trailer weight and balance.

A 200 lb dad makes his 100 lb kid a teeter totter. For the sake of making the numbers easy let's say the teeter is a 16 foot board and assume its weight is negligible.

Now, the kid sits on the left end of the teeter and lifts his feet. What happens? The rule is that both the forces and moments (torques) on the teeter have to end up netting out to zero for it to be stationary and stable.

So, the kid lifting his feet is applying a 100lb x 8ft = 800ft-lb torque due to gravity to the teeter. His weight forces it to swing counter clockwise till his feet touch the ground again. He will end up with 100 lbs of force pushing up on his feet to counteract the 100 lbs from gravity forcing it down. Net torque (moment) = 0 so nothing is rotating.

Total net force on the teeter also has to be zero or it will either lift in the air or dig itself into the ground. Since the teeter plus kid weigh 100 lbs and the ground is pushing up on his feet with 100 lb force to counteract the torque, the forces are balanced too, and so there is zero force required on the teeter pivot.

Now, let's say the dad gets on. Being a savvy guy on teeters, he sits 4 feet out from the pivot and lifts his feet. What happens?

He is now imposing a clockwise torque of 200 lbs x 4 ft = 800 ft-lb on the teeter due to gravity. This exactly balances the kids 800 ft-lb counterclockwise torque so the kid can lift his feet and the teeter doesn't rotate.

But what about the forces? There is now 300 lbs gravity force on the teeter from the weight of the two ppl on it, but neither one's feet are touching. So, were does the force get countered? By the pivot of course, which now has to push up with 300 lbs force. So the force on the pivot just went from zero to 300 lbs. even though we only added 200 lbs of weight.

This is whats going on with the rPod when you add weight aft (the dad) to try to reduce the hitch weight (the kid). The load on the pivot (the axle) goes up by the added weight plus the reduced weight on the hitch.

That's why its not such a great idea to add a lot of weight aft to reduce hitch weight. Its kinda self defeating at some point because it can quickly overload the axle.

It also increases the "polar moment of inertia" which is a measure of a vehicle's resistance to turning/sway. That's why the best handling sports cars are mid engine designs, by keeping most of the weight near the middle of the car its easier to get it to turn. By having lots of weight out at the far ends its both harder to get a trailer to start swaying but more importantly its harder to get it to stop swaying once it starts.

So, I think the approaches to reduce hitch weight (in my order of preference) are

1) leave stuff at home

2) move stuff from the front of the trailer to in front of the tow vehicle rear axle (the most lightly loaded axle on the rig is the front axle of the TV).

3) move stuff from the front of the trailer nearer to but in front of the trailer axle.

4) move stuff from the front of the trailer to behind the trailer axle.

1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold