Weight and Balance

Anything to do with mechanical, construction etc

Weight and Balance

Postby Tom&Shelly » Tue Mar 27, 2018 11:57 am

My wife and I are in the process of designing our 1st teardrop, which has evolved to a 10 x 5 benroy with 14 inch wheels, with air conditioning, two 6 v batteries (at least notionally), storage up front (in lieu of a tongue box), and a 24 inch deep galley. We intend to build it mostly following Steve Fredrick's techniques, except we plan to use 3/4" plywood for the skeleton instead of 1 by pine.

Our original weight goal was something slightly north of 1000 lbs, but, well, I think the military calls it "mission creep". After a fairly elaborate weight and balance calculation, I'm getting about 1540 lbs overall fully loaded (but not yet including fiber glass and paint/bedliner), and I wonder whether others here would comment on 1) whether that sounds about right? and 2) is this going to be a problem for our 2 door Jeep Wrangler to tow across the US (hopefully more than once)?

We plan to have a custom chassis built mostly out of 2 x 2 1/8" steel tube (3.05 lbs/ft), with a composite tongue ala Andrew Gibbens' "Simple Tongue Strength Table". With the frame, axle, 3 tires, and tongue, I calculate about 544 lbs.

For the wood and foam in the cabin, hatch, galley cabinets, etc. I get 534 lbs. I'm using published values for 1/4" plywood (22 lbs/sheet) 1/2" plywood (28.5 lbs/sheet) and 3/4" plywood (60.8 lbs/sheet), as well as estimates for poplar spars, foam, etc. As mentioned, I haven't yet included fiber glass, epoxy, or paint.

Then (here's the mission creep) the AC weighs about 72 lbs, the two 6 v batteries are about 62 lbs apiece, and our camping gear (folding table, folding chairs, privacy tent, easy up, etc.) to go in the forward storage (individually measured) comes out to 83 lbs. That doesn't count what goes in the galley: the propane stove (10 lbs), cooking items, 5 gallons of water (42 lbs), 20 lbs of ice and cold stuff in a cooler, and ~40 lbs of food.

I put all of this in a spreadsheet and also did some balance equations. Initially the camper was nose heavy unless I moved the axle too far forward (interfered with the door), so I kept it at 40 inches from the rear, moved the batteries from the front utility compartment to the galley, and moved the spare tire from the tongue to the left side behind the axle. what's left is, as I said above, a total loaded weight of about 1540 lbs, and a tongue weight of 182 lbs.

Our 2 door Jeep Wrangler has a rated tow weight of 2000 lbs with 200 lbs on the tongue. So, we're under specs, but will we have long term problems if we take the teardrop, say, from New Mexico to Update New York, or to the Northwest US/Canada every Summer?

Thank you in advance for your comments!

Tom and Shelly
Tom&Shelly
Palladium Donating Member
 
Posts: 95
Images: 46
Joined: Tue Sep 05, 2017 3:27 pm
Location: New Mexico

Re: Weight and Balance

Postby GuitarPhotog » Tue Mar 27, 2018 12:27 pm

I don't see any mention of axle rating nor of brakes. Calif. and some other states require trailer brakes on any trailer weighing 1500 lbs or more.

<Chas>
:beer:
GuitarPhotog
Silver Donating Member
 
Posts: 1697
Images: 55
Joined: Tue Feb 08, 2011 12:52 pm
Location: Grants Pass Oregon

Re: Weight and Balance

Postby Tom&Shelly » Tue Mar 27, 2018 12:44 pm

Hi Chas,

Yes, thanks: We will have trailer brakes. The company giving us the quote (pending) on the trailer frame suggested an axle rated for 3500 lb, with spring leaf suspension (easier to make emergency repairs than torsion axles). The weight rating corresponds with things others here have said, so I'm going with that.

Tom
Tom&Shelly
Palladium Donating Member
 
Posts: 95
Images: 46
Joined: Tue Sep 05, 2017 3:27 pm
Location: New Mexico
Top

Re: Weight and Balance

Postby Sparksalot » Tue Mar 27, 2018 1:38 pm

Your weight estimates sounds high to me. My Rose is 5x10 with solid 3/4" outer walls, 1x framing/spacers, and 1/8" inner skin. She's about 1,400# or so.
You don't know the power of the Dork Side.

The Compass Rose build thread
viewtopic.php?t=23213

Inspiration
http://tnttt.com/Design_Library/Trailer%20for%20Two.htm
User avatar
Sparksalot
Silver Donating Member
 
Posts: 1095
Images: 459
Joined: Fri Feb 15, 2008 9:36 pm
Location: Texas by God (TX, Buda, TX)
Top

Re: Weight and Balance

Postby tony.latham » Tue Mar 27, 2018 3:03 pm

Your wheels are turning. :thumbsup:

I think your weight estimate is probably close. I do wonder what you're going to power with those two batteries though. I would think you could shave that down to one 12V. Having said that, It's obvious you're doing your research so perhaps you've figured out you'll need that many amps. :frightened:

:beer:

Tony
Image
User avatar
tony.latham
Gold Donating Member
 
Posts: 2673
Images: 17
Joined: Mon Jul 08, 2013 4:03 pm
Location: Middle of Idaho on the edge of nowhere
Top

Re: Weight and Balance

Postby dancam » Tue Mar 27, 2018 3:14 pm

tony.latham wrote:Your wheels are turning.

I think your weight estimate is probably close. I do wonder what you're going to power with those two batteries though. I would think you could shave that down to one 12V. Having said that, It's obvious you're doing your research so perhaps you've figured out you'll need that many amps. :frightened:



Tony
Maybe running ac off em?
Or a fan all night?
Its pretty unbelievable how big of a battery you need just to run a fan for a few hours...

Sent from my SM-G920W8 using Tapatalk
dancam
500 Club
 
Posts: 528
Joined: Wed Jun 01, 2016 3:27 am
Location: Edmonton Alberta Canada
Top

Re: Weight and Balance

Postby John61CT » Tue Mar 27, 2018 3:19 pm

Trailer brakes for sure

Keep the tongue weight to 10%, unless you're really diligent about the rear GAWR, do you need the rear seats? Etc

Easy in the mountains, tranny temp gauge and a cooler.
John61CT
500 Club
 
Posts: 779
Joined: Thu Nov 17, 2016 4:36 pm
Top

Re: Weight and Balance

Postby tony.latham » Tue Mar 27, 2018 3:30 pm

dancam wrote:
tony.latham wrote:Your wheels are turning.

I think your weight estimate is probably close. I do wonder what you're going to power with those two batteries though. I would think you could shave that down to one 12V. Having said that, It's obvious you're doing your research so perhaps you've figured out you'll need that many amps. :frightened:



Tony
Maybe running ac off em?
Or a fan all night?
Its pretty unbelievable how big of a battery you need just to run a fan for a few hours...

Sent from my SM-G920W8 using Tapatalk


My Fantastic fan uses about 2 amps/hour (and we only need it for an hour or less on hot summer nights in the Rockies anywho). I question whether you can run AC with a couple of true deep cycle batteries for any length of time. (I would think one might suck 40-50 amps/hour????)

:frightened:

Tony
Image
User avatar
tony.latham
Gold Donating Member
 
Posts: 2673
Images: 17
Joined: Mon Jul 08, 2013 4:03 pm
Location: Middle of Idaho on the edge of nowhere
Top

Re: Weight and Balance

Postby linuxmanxxx » Tue Mar 27, 2018 5:01 pm

If your gonna fiberglass, I'd do something a lot lighter than 3/4 plywood. Stick frame using 1x would take over 500 pounds off the total. Much easier on TV to go that far.

Sent from my Pixel 2 XL using Tapatalk
Steve
MicroCampers
512-522-2810
info@microcampers.com
User avatar
linuxmanxxx
500 Club
 
Posts: 696
Images: 10
Joined: Fri Sep 10, 2010 1:50 am
Location: Abilene TX
Top

Re: Weight and Balance

Postby Tom&Shelly » Tue Mar 27, 2018 5:44 pm

tony.latham wrote:Your wheels are turning. :thumbsup:

I think your weight estimate is probably close. I do wonder what you're going to power with those two batteries though. I would think you could shave that down to one 12V. Having said that, It's obvious you're doing your research so perhaps you've figured out you'll need that many amps. :frightened:

:beer:

Tony


Actually I haven't yet. Tomorrow I'll measure my Maxxfan to see how much it draws. I've read the posts here from folks who have made the calculations and I concur that it isn't practical to run an air conditioner on batteries. When we're in territory where we need AC, we'll go to camp sites with shore power. The idea for the two golf cart batteries was just, when we want to spend a few days boondocking in one spot, we might want that reserve. May not be necessary. Maybe by the time we're ready for that, I'll add a solar panel.

We're actually building our teardrop for several distinct kinds of camping. After we build it this Summer, we want to take next Summer and spend 8-10 weeks driving from New Mexico to Upstate New York to visit my family, along with some of Shelly's relatives on the way. That will necessarily involve developed campsites (not much national forest or BLM back there), and will likely require the AC through the South. Then, we want to visit the National parks in the West in future years. There, we probably will go for dispersed camping on forest service land. We'd be up in the mountains where no AC is necessary. And then there are the long weekends in the deserts here in the Southwest. (I may try and build a swamp cooler, which could run off of a battery. But they only work in low humidity. Anyway, in Fall, Winter, and Spring, cooling isn't usually the problem in the deserts.)

I want to make sure the battery box is large enough for two batteries, but probably can get away with a single 12 v at least for the first trip. This was a "worst case" weight budget.

Thank you all for your comments!

Tom
Tom&Shelly
Palladium Donating Member
 
Posts: 95
Images: 46
Joined: Tue Sep 05, 2017 3:27 pm
Location: New Mexico
Top

Re: Weight and Balance

Postby tony.latham » Tue Mar 27, 2018 5:50 pm

Image

:thumbsup: :beer:

Tony
Image
User avatar
tony.latham
Gold Donating Member
 
Posts: 2673
Images: 17
Joined: Mon Jul 08, 2013 4:03 pm
Location: Middle of Idaho on the edge of nowhere
Top

Re: Weight and Balance

Postby Tom&Shelly » Tue Mar 27, 2018 5:53 pm

John61CT wrote:Trailer brakes for sure

Keep the tongue weight to 10%, unless you're really diligent about the rear GAWR, do you need the rear seats? Etc

Easy in the mountains, tranny temp gauge and a cooler.


Excellent ideas, thank you John! Just yesterday we tried to back our HF utility trailer loaded with junk, up our (uphill) driveway, and Shelly's Jeep complained about overheating transmission fluid. First time we'd seen that. She researched it last night, and now we plan to upgrade or add a 2nd cooler. A gauge is a very good idea.

Oh, we always take our rear seat out of the Jeeps when camping. Takes up too much room. :D

Tom
Tom&Shelly
Palladium Donating Member
 
Posts: 95
Images: 46
Joined: Tue Sep 05, 2017 3:27 pm
Location: New Mexico
Top

Re: Weight and Balance

Postby John61CT » Tue Mar 27, 2018 9:09 pm

Well my point is, to the extent you weigh down your back axle, the less capacity you have for towing (safely)
John61CT
500 Club
 
Posts: 779
Joined: Thu Nov 17, 2016 4:36 pm
Top

Re: Weight and Balance

Postby dancam » Tue Mar 27, 2018 10:10 pm

Tom&Shelly wrote: Just yesterday we tried to back our HF utility trailer loaded with junk, up our (uphill) driveway, and Shelly's Jeep complained about overheating transmission fluid. First time we'd seen that. She researched it last night, and now we plan to upgrade or add a 2nd cooler. A gauge is a very good idea.

Tom


Just a larger cooler for the transmission should be all you need, not a second one. Its probably a common modification so if you google what others use on that particular jeep you should find a good solution pretty quick.

Sent from my SM-G920W8 using Tapatalk
dancam
500 Club
 
Posts: 528
Joined: Wed Jun 01, 2016 3:27 am
Location: Edmonton Alberta Canada
Top

Re: Weight and Balance

Postby Tom&Shelly » Tue Mar 27, 2018 10:14 pm

John61CT wrote:Well my point is, to the extent you weigh down your back axle, the less capacity you have for towing (safely)


Yes, we will keep it between 10 and 15%. When I was planning the put the batteries in front, it was getting up to 18% and a bit over 200 lbs.

Tom
Tom&Shelly
Palladium Donating Member
 
Posts: 95
Images: 46
Joined: Tue Sep 05, 2017 3:27 pm
Location: New Mexico
Top

Next

Return to Teardrop Construction Tips & Techniques

Who is online

Users browsing this forum: No registered users and 1 guest