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Thread: Trailer Material Size..
02-06-2009, 12:04 AM #1
Trailer Material Size..
I will be building a trailer shortly. Here are the specs;
3000lb single axle
My question is what is the ideal size for tubing for the frame, crossmembers and tongue. Based on the reasearch I have done, I have found that
2"x3"x1/4" rectangular tubing is generaly used for the frame.
Does this sound ideal?
Or...... is there a better (lighter weight) alternative?
Someone suggested this to me;
Main frame = 2x4x3/16
Crossmembers = 1.5x3x3/16
Tongue = 3x3x3/16
That will save me some weight, but I want to make sure it is going to be strong enough.
Is there any logic to determining the sizes? Obviously experience and trial and error, but I need to be able to explain my reasoning here too.
Thanks for your help!
02-06-2009, 07:21 AM #2
thats some metal there (2x4") , i use angle where i can to save money and weight. or even c-channel so the flat side is out and its looks like tube.
02-06-2009, 09:14 AM #3
I would look into having a sheet of suitable Gauge material broke up into channels at a local sheet metal shop.
Strong and light
02-06-2009, 07:30 PM #4
3/16 wall may be a bit on the heavy side but I think it's good to use closed sections for the major structural pieces. Blodgett's column in Welding Magazine is a great reference for this sort of stuff, I'll try to add a link to one particular column that I think is relavant.
02-06-2009, 08:13 PM #5
This may help you out some. I made my own trailer several years back to haul my motorcycles around on. I needed it to fold up so that I could store it inside the garage standing on end. The idea worked perfectly.
The trailer takes up a footprint size of 24 inches by 63 inches and rolls around easily on the 4 caster wheels bolted to the underside of the tailgate ramp..................
I made the entire trailer frame is out of 1 inch by 2 inch by 1/8 inch wall tubing. This is plenty strong to support the weight of the trailer with a spare tire, a full size 700 lb Harley Davidson motorcycle loaded onto it's back, and misc other items stacked on the deck.
The tongue was made out of 2 inch square 1/8 inch wall tubing. I ran this member down the entire 8ft length of the trailer. I put a sheet of aluminum on top of the frame for a deck.
This trailer is hinged at the rear, so it all folds up and can be uprighted on end in about 15 minutes. It takes me about 45 minutes to turn it into a trailer and load the bike.
I have pulled this trailer all over the United States, from coast to coast in both directions. Thousands and thousands of miles and there has never been one bit of trouble with it.
The underside shows the layout of the frame members. I like the 1in x 2inch box members because they are easy to cut, easy to weld together and easy to weld tabs onto. If angle were used in place of the tubing......... Well, let me just say that would not be my trailer!
The torsion axle and wheels were purchased from Southwest Wheel up in Amarillo TX. The axle has a load rating of 2000lbs and Southwest used a 2-1/2 inch square tube for the axle.
I wanted this type of axle because I wanted the trailer to sit low and I did not want to deal with putting springs on the trailer frame. That's a PITA!
The trailer will carry any of my 4 motorcycles, but only one at a time of course.........pg
02-06-2009, 10:29 PM #6
the bad thing about tubing is it gets water inside and rust's from the inside out. thats why most people seam to use channel.
02-06-2009, 10:43 PM #7
If you really want to dig into figuring out the design on your own, Blodgett has a book called Design of Weldments, which is very good.
If you just want to get a basic feel for how it should be, you could just check out similarly sized trailers that are commercially available. Better yet, just buy one of those commercially available trailers, it's hard to beat a mass produced product for cost and resale value, unless what your making needs to be custom for some reason.
02-06-2009, 10:46 PM #8
What is the load?
Before selection of material you need to determine the loads and stresses.
What is the function of the trailer?
What is the weather and other environmental conditions?
What type of roads do you have?
What is the tow vehicle ?
If you have a heavy load and nasty bumpy roadss then the trailer will need additional strength to handle the weight on the landing past the bump.
Capacity of tow vehicle limits both the weight of the load and thy type of trailer.
02-06-2009, 11:06 PM #9
Perhaps a little overkill, but I'd go with 3 inch channel for side rails, boxed 3" channel for tongue, 3" channel for last (rear crossmember. Make the other cross members from 2" channel, and Gusset Everything - 3/16" plate cut into triangles on all joints.I like to v the side rails in to just about 18". behind the hitch, and run the tongue back to where the side rails are straight, and T into a 3" channel crossmember. ....Made a number of trailers up to 16 foot tandem axle with 3, 4, and 6 inch channel. Only had one bend - it was a tandem axle w/4" channel sold to a local rental place. They rented it to an idiot who took it to the building supply store and loaded 1200 lbs of shingles in a stack at the front, followed up with a stack of plywood sheathing and 2X4s. Course the 1200 lbs wound up square between the hitch and the axle. No welds broke, just the 4" channel bent. We offered to repair it for free, the owner said, no way, the idiot pays.....
02-07-2009, 10:58 AM #10
If the state where you live uses sand and salt on the roads in winter like they do here the best thing to use is channel and angle iron. Water will find a way to get into the inside of a sealed tube and rust it out. Been there, done that.
I like to use 4" side channels and 3" for crossmembers. Weld the "C" section outside and put the crossmember flush with the bottom of the side rail and use 1.5" treaded lumber for the deck. Then the deck sits just a bit above the trailer. If the "C" section is welded to the outside then you can put your side marker lights inside for protection from getting smashed.
02-07-2009, 11:13 PM #11
02-11-2009, 08:46 PM #12
I built this one a couple of years ago. #3500lb. torsion axle. 2"x3"x1/8" wall rectangular tubing for perimeter of frame. 1-1/2"x1-1/2"x1/4" angle iron for cross members. 3" channel for tongue.
Note how I flush-mounted the tail-lights inside some rectangular box tubing for protection.
02-14-2009, 03:23 PM #13
I quit using tube for trailer frames and went to channel , so I am biased towards channel .
Weight is relative , too light a frame the service life of the trailer is shorten , to heavy a frame wastes a lot of fuel but lasts a longtime .
Tube is nice to work with as you have four flat sides , but needs more prep than channel before welding . Also drain holes need to be drilled to allow air movement so it can dry out or the trapped moisture will quickly rust it out . I have repaired several trailers that had tube cross members that were completely rusted through . I replaced the tube with channel to cure this problem .
For a 3000# trailer 3" X 4.1#/' channel is heavy enough or go up to 3 X 5#/' would add 31lbs to your GVW , but would be stiffer .
Single axle trailers should have around a 60%/40% ratio in the positioning of the axle if they do not tip . I set up ones that tip at 50/50 , with at tip latch on top and a safety pin under the tongue that is made from 3" X 3" X 1/4" wall tubing and a one inch or larger pivot point .
Angle Iron trailers might be lighter than the same sizes trailer made from Channel but in my experience do not last as long . I weighed out my 6' X 12' 6000# trailer at the same time as my buddy weighed out his 6' X 12' angle iron trailer (both single axle) for titling purposes and my trailer weighed about 100 pounds more then his . But he got the angle iron for real cheap . Angle iron trailer frames need to be of a truss design to stiffen them also .
On to the axle and wheels , I use Dexter Tor-Flex axles with mounting brackets instead of leaf springs and have not as of yet had a failure of one of them . They give a better ride quality and are much less noisy going down the road . The mounting brackets make mounting the axle easier and make replacing one very simple . If you use leaf springs make sure you get them with spring eye bushing as they wear out and need replaced over time . Bushing are cheaper then new springs . Wheels use the largest you can , they reduce bearing speeds which makes them last longer and run cooler . If your wheels and tires are under the bed of the trailer than the choices are somewhat limited .
Now it comes down to personal preference among the members of this board as to what they build their trailers out of . Here in the northern U.S. Road salt kills more trailers then most other causes so rust proofing and painting is a good idea .
JMHO's , Dan