Axle placement and frame design question

[unicknn]

Im in the planning stages of building a teardrop to tow behind my minitruck. the plan is to put an adjustable airbag suspension under the trailer which will be controled from inside the truck.

My question is what would happen if I moved the axle back further then the 40% that is suggested? I want the wheels back as far as possible because there will be a big notch in the fram and I dont want to loose sleeping space

Im trying to keep this thing at about 8 feet but unless I can move the axle back its going to have to be 10 feet to acomodate the notch. Heres a real quick frame I drew up in Inventor last night. This is for the 10' trailer EDIT: its 10 foot not counting the tongue, which I have set at 5' but Im gonna make it smaller because I just read a thing about tongue strength.



Also for those who are building their trailers from scratch do you think 2x2 square tubing would be strong enough? Those harbor freight ones look pretty crappy but they hold up just fine so I think 2x2 is gonna be ok.

[jim patterson]

i built my 5X10 frame out of 2X2X1/4 Angel and have had no problams.

[unicknn]

what gauge steel did you use? I saw someone else used 16 gauge box tubing. I really do want to make the frame on this thing REALLY tough being bagged it will take some abuse. lol

[angib]

The further back you move the axle, the more weight gets carried on the tongue and hitch. If you've got a truck, that may be no problem to the truck, but you will need to consider the extra load on the tongue when choosing the tube for that. Moving the axle back is likely to increase the towing stability of the trailer.

So you can do it, but remember to increase the tongue strength to match.

[unicknn]

what gauge steel did you use? I saw someone else used 16 gauge box tubing. I really do want to make the frame on this thing REALLY tough being bagged it will take some abuse. lol I may even use thicker metal than 16 gauge just to be safe

[unicknn]

The further back you move the axle, the more weight gets carried on the tongue and hitch. If you've got a truck, that may be no problem to the truck, but you will need to consider the extra load on the tongue when choosing the tube for that. Moving the axle back is likely to increase the towing stability of the trailer.

So you can do it, but remember to increase the tongue strength to match.

Hmm ok thats good to know. Yea the truck can handle it, Ive got an air suspension so more weight on the tongue means nothing to me, I edited my drawing and used 2X3 tubing on the tongue and shortened it to 42". Do you think this would be enough to support the load?

[unicknn]

Just for reference this is the truck that will be towing it.



Basically the frames of both will be able to sit on the ground when Im parked

[Forrest747]

A low rider tear I love it.
2x2 will be fine i did mine in 2x2 with a 2x3 tongue.
been doing calculations for using 3/4 inch or 1/2 wide and 2 inch rectangle tubing for the next one to help lighten the trailer
are you planning on any offroading (doubting you are) than you can go smaller in tube size
what is your width you are thinking about
with a 10 foot trailer your notch into the sleeping area would be in your feet area
i also did 10 feet long and 5 feet wide

[unicknn]

A low rider tear I love it.
2x2 will be fine i did mine in 2x2 with a 2x3 tongue.
are you planning on any offroading (doubting you are) than you can go smaller in tube size
what is your width you are thinking about
with a 10 foot trailer your notch into the sleeping area would be in your feet area
i also did 10 feet long and 5 feet wide

No I wont be doing any offroading. Maybe really light offroading but nothing serious. My tires arnt made for dirt lol. So pretty much just down dirt roads and maybe off into a pasture or something. The truck lifts up to almost stock height so I can get around some small obstacles.

Yea my design for the trailer frame is 5X10' as well. Heres an new frame I did with the shorter tongue made out of 2x3. What gauge steel did you use? The reasons Im woried about the 16 gauge is its REALLY thin and I dont want to have it rip apart the first time the trailer hits the pavement while Im driving down the road lol.




The trailer will be built to match the truck as much as possible, Im gonna be running the same wheels as the truck and everything

[Forrest747]

I want to say i went with 14 gauge i could be wrong. i will look at it when i get home. 16 should be ok for your purpose. i would put your notch now that i see your plan at your height plus 2 inches. will not be too far back and you can do some of the moment arm calculations with more weight on the rear to make the tongue weight proper. the stress point i would be worried about is the tongue attachemtn point since you will not be going under like alot of us do. maybe a flat gusset to help stiffen that area. cant do the calculations right now but will on monday

[unicknn]

The notch should be fine. The wheels and tires are 26.8" tall. so thats a radius of 13.4. I plan on using a 6" drop axle, unless I can build one with more drop (havent looked into that yet). So 13.4-6 means I need a 7.4" notch to lay the frame on the ground. That notch is 9" higher than the bottom frame. Im open to more gusseting if the need arises, this is the very beginning of the planning stages. I may bump it up to 14 gauge though just for piece of mind. I want to drag this bitch once in a while at truck shows lol.

[Forrest747]

Page 48 is where i am getting this data.
http://www.steeltubeinstitute.org/pdf/brochures/beam_load_table_bro.pdf

just peliminary at this point
You are looking at a 4 foot span at 1/4 inch thickness will have 3800 pounds of force with 1/4 inch deflection (not a big deal in our application)
goto 1/8th inch thick and your looking at 2500 pounds of force with 1/4 inch delfection.
with the load distributed along the length of 75 inches (just before the notch) with 3/16 wall thickness you are looking at 2100 pounds to have a 1/4 deflection.

[unicknn]

Page 48 is where i am getting this data.
http://www.steeltubeinstitute.org/pdf/brochures/beam_load_table_bro.pdf

just peliminary at this point
You are looking at a 4 foot span at 1/4 inch thickness will have 3800 pounds of force with 1/4 inch deflection (not a big deal in our application)
goto 1/8th inch thick and your looking at 2500 pounds of force with 1/4 inch delfection.
with the load distributed along the length of 75 inches (just before the notch) with 3/16 wall thickness you are looking at 2100 pounds to have a 1/4 deflection.

OK Im confused as to what all this means lol. I understand the terms and everything I just dont really know what part of the trailer youre talking about lol. Are you talking about the tongue here? The length from the begining of the notch to the tip of the tongue is 102" and from the notch to where the tongue starts is 58".

Do you have inventor or anything like that? I could just send you the files and you can look at them

[Forrest747]

Sorry I was talking from the notch to the point where the tongue is attached. You also have to factor that u have 2 beams. I am not concerned with the notch to the rear. So you could do 3/16 and be ok. The point where the tongue and the frame meet is where I would be concerned

[unicknn]

ok so the 16 gauge wont work then lol. Thats gonna add to the cost of the frame but no worries. What do you think I could do to strengthen the tongue attachment? Should I just use 3/16 on the entire frame?