Weight and Dexter axle help! (frame idea added scroll down!)

[toolferone]

I have been doing lots of reading and I had a great chat with Christine (a engineer at Dexter) about the torsion axles. They need to know the weight of the trailer to build a axle just right for the weight. It seems to me the only way to do that right would be to build the trailer and TD and then weigh it. I know that is not how you all are doing it. I know I can figure the weight of the frame and get pretty close with the shell, but that leaves the galley componets and all you are going to pack in it. So what am I missing here? How are you all deciding the weight before you build? Oh, does anyone know about how much the Dexter axle weighs for a 60" frame?

Thanks for your thoughts on this.

This will be a long term project for me. I will be collecting info and designing for over a year before I start. Besides the fact that my wife is due with our second child in August. She told me if I started any work on the TD this year I would be sleeping in it forever (finished or not)

P.S. Are there any TD owners near me that I could come visit to see there trailer (Raleigh NC). I travel to Hickory and Charlotte to see family so anywhere in between is good too.

[angib]

Here is some assorted weight estimating data I have collected, mostly from Northern Tool's web site. Christine* supplied me some weights too, but they are for axles to suit a 48" frame - I would guess there's less than 5lb extra weight for a 60" frame.

Wheels (source: Northern Tool)
Wheel and tire, 205/70x15, D range - 1710lb capacity, each : 44lb
Wheel and tire, 205/70x14, D range - 1710lb capacity, each : 37lb
Wheel and tire, 175/70x13, C range - 1360lb capacity, each : 32lb
Wheel and tire, 175/70x13, B range - 1100lb capacity, each : 29lb
Wheel and tire, 5.30x12, C range - 1045lb capacity, each : 24lb
Wheel and tire, 4.80x12, B range - 780lb capacity, each : 20lb
Wheel and tire, 4.80x8, C range - 745lb capacity, each : 12lb
Note: capacities and weights are PER WHEEL

Axles (source: Dexter/Northern Tool)
Rubber torsion axle, #8, no brakes, 1100lb capacity, 60" over hubfaces : 53lb
Rubber torsion axle, #8, electric brakes, 1100lb capacity, 60" over hubfaces : 75lb
Rubber torsion axle, #9, no brakes, 2200lb capacity, 60" over hubfaces : 68lb
Rubber torsion axle, #9, electric brakes, 2200lb capacity, 60" over hubfaces : 89lb
Leaf sprung tube axle, no brakes, 2000lb capacity, 60" track, complete : 65lb
Note: thanks to Dexter who provided weight data for the examples above.

Chassis Hardware (source: Northern Tool)
Coupler, 2" ball, 3500lb, straight : 4.5lb
Coupler, 2" ball, 5000lb, A-frame : 7lb
Coupler, 2" ball, 5000lb, A-frame, heavy duty : 14lb
Jack, side mount snap-ring, 2000lb : 13lb
Jack, top mount, A-frame, 2000lb : 11lb
Caster for jack : 6lb
Stabiliser jacks (corner steadies), 1000lb, pair : 10lb
Fender, round, steel, 23.5"L x 7"W x 6.5"H, each : 6lb
Fender, round, steel, 27.5"L x 8"W x 11"H, each : 9lb
Fender, round, steel, 32"L x 9"W x 16"H, each : 16lb

Electrics
Battery, Group 24 : 50lb
Battery box : 3lb

*And doesn't Christine do a fine job of representing Dexter? Give her a raise, Dexter bosses - she earns it.

Andrew

[Jiminsav]

are you getting a full axle or a half axle?
I got half axles rated at 1000 lbs each for a grand total of 2000 lbs, and so far the trailer weighs 1000 lbs.
seems to me that everyone uses axles rated near 2000 lbs, so just get some 2000 lb axles and go to town.

[toolferone]

Thank you for all those weights. I will add them to the list. I was planning on using a full axle because I am going with a light weight frame. the stub axles need more support. I understand what you say about just getting a 2000 lb axle and going for it, but wont the trailer ride rougher. I plan on trying to build really light and a smoother ride should help keep things together maybe? I am open for all thoughts as I am in the learning/preplanning stage right now.

[Keith B]

I heard Madjack was able to get a d'rated axle to like 1500 from Dexter... Pretty much you're gonna have to guess... if you know the weight of your frame and an estimated weight of the camper you're 1/2 way there... now just think of other things... like battery at about 40#, 40qt cooler full and w/ ice could probably top 70#s, and then just start looking up weight for other things you have, stove, lanters, water (rougly 6#p/gallon), get all your camping gear, put it in a box and weigh the box, lawn chairs... personally, I just went w/ a 2k axle... I can always "add" weight w/ lead in the frame rails, etc. if I "have" to, but more difficult to take it away...but I "think" the rule was guess the weight and add 10-20% or something like that for "shock" value in hitting potholes, etc... Andrew is the expert probably.

[madjack]

TF...I get Dexters #9 2200# axle and have them de-rate it to 1500#s...my rule of thumb is to have a 50% overcapacity in the axle rating...this gives about the best on ride Vs. longevity ...the 1500# rating gives me a 1000#s of trailer and gear with a 500# cushion...you do not want to have an axle rated at exactly what your weight is because it just won't hold it...a few have had 'em matched exactly and flattened them out....this is not rocket science, sufficient capacity with an adequate cushion is pretty open to interpretation...in other words, unless you are building really large and heavy, something in the 1500-2000 pound range will work just fine.............
madjack

[elmo]

+1 on Christine. That is who helped me also. She does a great job!

[toolferone]

Great, these are the kind of answers I was looking for. I think a #9 derated for 1500 should work fine.
Thanks again

[angib]

my rule of thumb is to have a 50% overcapacity in the axle rating...this gives about the best on ride Vs. longevity

The additional piece of 'experience' to add is from Cary at Camp-Inn trailers who reckons that a rubber torsion axle loaded at less than half its rated load rides rough, so its 'sweet spot' (I'm quoting from memory) starts at 50% of its rated load.

you do not want to have an axle rated at exactly what your weight is because it just won't hold it...a few have had 'em matched exactly and flattened them out.

Visiting the Fiberglass RV forum as I do, it is apparent that most of these trailers (Scamp, Boler, etc) from the 60s to the 80s had axles that had to carry at least 100% of their rated load and often more, once the trailer was loaded. After 20-30 years most of these axles need replacing, having lost any springing.

So, many trailers lasting 20-30 years at 100% (or more) of rated load suggests that madjack is being very pessimistic when he reckons that 67% of rated load is about the maximum.

Andrew

[madjack]

Andrew...Cary's numbers pretty much bear out my rule of thumb...ask the Snoopester(Doug) about his experience with maxing out springs(I have seen it elsewhere as well)...my rule of thumb comes from twenty plus years of commercial trucking, where fleet operators and anyone else who can, will spec big trucks with 17,000#(12,000#s required) front axles and 50,000#(34,000#s required) rear/trailer axles which adds up to 117,000#s for a rig designed to weighin at 80,000#s max...this is done for ride/handling characteristics as well as longevity/maintenance issues...so MY rule of thumb(as I stated) is based on my experience in the commercial trucking industry...as always...Your Mileage May Vary
madjack

[angib]

Should there be different numbers/ratios for leaf spring and rubber torsion axles? Transferring experience from one to the other doesn't seem logical to me, when the spring part is so different.

Andrew

[madjack]

Should there be different numbers/ratios for leaf spring and rubber torsion axles? Transferring experience from one to the other doesn't seem logical to me, when the spring part is so different.

Andrew

Andrew...torsion axles are relatively new to me(only a couple of years experience)...I can only go with what I know...the fact that Cary talks about the "sweet spot" and that spot falling right smack dab into my rule of thumb about ride, leads me to believe that other "spring" related experience may be related as well.....
madjack

[Cary Winch]

Andrew,

You pose a good question. Does a buggy spring respond to load percentages different than a torsion? Don't know. My guess would be that without the reflex dampening of the rubbers in a torsion that it would have a higher percentage.

50% is a good rule of thumb. It actually is a little bit less. We use all 2000lb axles. A 900lb unit rides good. A 800lb will be a bit bouncy. Less than that and it will feel like there is no suspension. These are all empty weights.

Don't forget too that people bring along way more stuff than any of us would guess. A customer of ours gave us a really good trip report recently. He has a very well equipped 560 that probably weighs empty at about 1,300lb, maybe a hair more. With all his gear in it he ran it on a scale and it weighs 1,960lb. Now that is alot of stuff. He didn't even have the water tank filled. Had he filled it, the 67lb of water would have put him over.

So, Tom. I guess what I am saying is to take a really realistic look at what you will all put into it too. Also, most homebuilts that are built light are still probably overbuilt some. Most everyone here will attest to that. So, plan on a higher weight than planned (is that a proper sentence?).

Cary

[toolferone]

Okay, all this make sense. I do beleive that most folks building light still are heavy.

I have not run all the weights yet, but my thoughts at the moment are to build the frame out of 1" square 11 ga. and build my floor as a torison box to add the stiffness I need. I think it will be much lighter. I will add up all the weights first and see. If some people here are building with out frames then this should work. I will make the tongue out of 2 x 3 x 3/16.

Any thoughts would be great.

[alaska teardrop]

It seems to me the only way to do that right would be to build the trailer and TD and then weigh it.

Tom,

I like your thinking there. When I built, it was on a 2 x4 dolly with caster wheels. You can complete your td, load it and then weigh it with 3 or 4 bath scales. Apply the info that the guys gave & order the axle.

Another idea that other builders have done - from info already on this board, you can determine the correct balance point (hitch weight) fairly close in the design stage. When you build the frame allow for mounting the axle 4 to 6 inches to the front or back from that point to get the precise hitch weight that you want. Note that this requires close attention to the fender/door relationship in the design stage and mounting fenders last.

Fred