Haven't seen any new frames posted in a while

[teardrop_focus]

^ ^ ^ That lil' aero is interesting... and it's something we've talked about before... somewhere here. The fact that the trailer body in some cases might act as a link from tongue to axle... but very few are brave enough to have tried it.



Notice that the central square tube more than likely resists torsion, relieving the plastic body from taking all of the force from the axle tube wanting to twist in it's outboard mounts... which is why most frames are perimeter frames.

dh

Just curious, what tubing are you using? What is the (estimated) frame weight?

It's all 14 ga mild steel; 2 X 2 and 1 X 2... I don't have total footage of the different tubing near me at this time. I'll weigh it when it's welded together.

I'm going to cut some small, almost half-circle plates to mount longitudinally on the opposite side (bottom side) of the axle plates on the ends of two 2 X 2 crossmember tubes. There is some concern that the 2 X 2 will twist, or warp, if only the top side is welded to when the half-axle plates are attached.

I should be able to report back tomorrow after a good metal fab guy has a look at them... I'm driving 40 mins to go see him tomorrow afternoon.

[eamarquardt]

It looks like the only connection between the fore and aft frame members to the axle cross members are butt welds. Intuition and experience tells me that relying on butt welds between pieces of thin wall tubing at the most stressed part of a trailer frame is not good engineering/design practice. The three MEs (and one senior at Cal Poly school of engineering) that I showed your pics to, shared my concern. They all recommended adding plates/gussets above and below the tubes to tie them all together.

I'd seriously consider the thoughts of these engineers (PhD in ME and professor at CSUN after 35 years at Rocketdyne, ME with 25 years experience at Rocketdyne, and the others) and add reinforcing plates top and bottom to tie all the tubes together.

Cheers,

Gus

[teardrop_focus]

Good sense will then prevail.

I'll fab up some plate gussets to bridge the crossmember, connecting the front and rear frame assemblies. Squares, on a diamond, with triangular cutouts - to avoid collecting water (and to save weight) - would be the ticket...

Please remind your rocket scientists that when it comes to the typical teardrop's wooden monocoque structure, one could almost bolt a tongue to the front and an axle to the aft midsection and it would work. Almost.

Remember this is an 1100 lb rig. It is not heavy.

[eamarquardt]

Please remind your rocket scientists that when it comes to the typical teardrop's wooden monocoque structure, one could almost bolt a tongue to the front and an axle to the aft midsection and it would work. Almost.

Remember this is an 1100 lb rig. It is not heavy.

All we know is what we have pictures of. W/O knowing the details of the box everyone else that comments is "flying blind". Rocket scientists have to get right the first time so they play it somewhat safe sometimes. Your teardrop may start out at 1100# but it may put on weight. When I bought our boat it floated about 2 inches higher than it did 10 years later. When I unloaded all the diving gear, spares, extra sails, dingy, outboard, etc., etc., etc. it returned to it's original waterline.

"Big"Guy's suspension is bottoming out (he's promised to let me fix it when he returns to the area) and has caused his frame to bend a bit. His "box" is also suffering damage due to the flexing.

You're planning on adding the gussets so you must agree (at least a little bit) that their comments are valid.

IMHO Murphy was an optomist.

Cheers,

Gus

[teardrop_focus]

All we know is what we have pictures of.

You're on a teardrop trailer forum. You yourself, sir, know that I'm building a teardrop trailer.
Is it too much to ask that when you show pictures to strangers that you might include some pertinent info?

Your teardrop may start out at 1100# but it may put on weight.

A pilot of any aircraft would not allow his airframe to be loaded beyond specification... I am placing a cap on the trailer's gross weight at 1100 lbs. If it weighs 1101, then an offending item will be removed and that item will stay home.

My tow vehicle only has so much performance, and to add engine performance would be tampering with emissions equipment, and that is a violation of a federal law.

Keeping the tug and trailer combination's gross weight within this cap is vital to maintaining a certain highway performance standard. Removing weight, not adding it, will be the key to success.




I'm adding gussets because:

A. I too like the idea. I like the potentail for any increase in chassis reliability and they won't add much appreciable weight.

B. The chassis will first be used as a camping utility trailer; a "convertible" teardrop... that has a galley. Then when the standard, enclosed teardrop cabin is complete it will replace the wooden structure that had been acting as a camping utility piece.

C. I'm also adding gussets/plates so that you will stfu. With all due respect, of course.

[eamarquardt]

All we know is what we have pictures of.

You're on a teardrop trailer forum. You yourself, sir, know that I'm building a teardrop trailer.
Is it too much to ask that when you show pictures to strangers that you might include some pertinent info?

:scratchthinking:

Your teardrop may start out at 1100# but it may put on weight.

A pilot of any aircraft would not allow his airframe to be loaded beyond specification... I am placing a cap on the trailer's gross weight at 1100 lbs. If it weighs 1101, then an offending item will be removed and that item will stay home.

My tow vehicle only has so much performance, and to add engine performance would be tampering with emissions equipment, and that is a violation of a federal law.

Keeping the tug and trailer combination's gross weight within this cap is vital to maintaining a certain highway performance standard. Removing weight, not adding it, will be the key to success.




I'm adding gussets because:

A. I too like the idea. I like the potentail for any increase in chassis reliability and they won't add much appreciable weight.

B. The chassis will first be used as a camping utility trailer; a "convertible" teardrop... that has a galley. Then when the standard, enclosed teardrop cabin is complete it will replace the wooden structure that had been acting as a camping utility piece.

C. I'm also adding gussets/plates so that you will stfu. With all due respect, of course.

:lol:

Siimply put: YOU ARE BICKERING! WTF does stfu mean?

You posted pictures of a very unconventional frame. I took the initiative and got you some free excellent input. You, apparently, have taken the input to heart and will follow through and use the suggestions. Good!

NOW, as someone once told me: "YOU NEED TO LET GO".

Cheers,

Gus, OUT!

[dh]

Please remind your rocket scientists that when it comes to the typical teardrop's wooden monocoque structure, one could almost bolt a tongue to the front and an axle to the aft midsection and it would work. Almost.

Hell, I've seen it done. Can't remember who, but I saw it a while back. They bolted the half axles directly to the wooden floor of the tear cabin. Don't remember what they did for the tongue, but it wasn't attached to the half axles by wnything at all but the floor of the teardrop.

[dh]

http://www.jiminsav.com/newtrailer/slid ... 20002.html

Maybe I embellished a little, but here is the link. The half axles are just bolted to wood, and it looks like the tongu might connect to the same piece of wood. But there is no metal connecting the half axles and the tungue.

[teardrop_focus]

^ That's alright. The point was illustrated.

teardrop_focus

There is some concern that the 2 X 2 will twist, or warp, if only the top side is welded to when the half-axle plates are attached.

I should be able to report back tomorrow after a good metal fab guy has a look at them... I'm driving 40 mins to go see him tomorrow afternoon.

I left the crossmember bits with Mr. Fabricator... 'cause he seemed to think it'd be fine. And the tubes didn't warp; he stitched alternately top and bottom, 1 inch each.

Others here on T&TTT whom I have spoken w/ in PM have said too that the planned chassis is fine as is; that no additional gussets or plates are necessary.







Waiting now on a 2" square tube-bending die... I need to raise the coupler to meet the hitch ball height. I'm going to bend the tongue 30° up for a rise of 4.5 inches, then bend it 30° again to level. Sorta like you see on the '40s Kit teardrops...

(the hitch ball needs to stay where it is to provide ground clearance when entering or exiting steep driveways and the like)

[WesGrimes]

I don't know nuttin 'bout nuttin 'bout all this frame design debate stuff, but that is a purdy looking weld you got yourselft there!

[kennyrayandersen]

[quote="teardrop_focus"]^ ^ ^ That lil' aero is interesting... and it's something we've talked about before... somewhere here. The fact that the trailer body in some cases might act as a link from tongue to axle... but very few are brave enough to have tried it.



Notice that the central square tube more than likely resists torsion, relieving the plastic body from taking all of the force from the axle tube wanting to twist in it's outboard mounts... which is why most frames are perimeter frames.



There is really no torsion in the center tube forward of the front support because the coupler is free to rotate about the x (fore/aft) axis. I suspect it adds torsional stiffness between the axle and the front support though. If the trailer is loaded evenly it shouldn’t be too much though. I think the typical teardrop body though acts more like a closed shoe box (despite the cutouts for the door) and is quite capable of reacting any torsional loads. Assuming that you join the sides and center section together with good joints all you really need to do is 1) get the vertical loads into the sidewalls (which are very stiff in the vertical direction) and 2) react the tear to frame loads which are also not particularly high. The tear box will react the torsional loads quite easily IMO.

I did so finite element modeling of just a single-member tongue and it looks to be quite feasible, though practically speaking it’s only marginally heavier to go with Andrew’s Piccolo trailer frame which would be more robust. Sometimes trading robustness for a little bit of weight is a good thing. My hat’s off to Andrew on that one as he solves quite a few problems with just a little bit of structure – always the sign of a good engineer IMO.

For the Flea, which I’m working on now but haven’t started a thread, I will be using Andrew’s piccolo frame, but I’m looking into making a material switch to aluminum to save a bit more weight.

[kennyrayandersen]

With regard to the previous brouhaha, I think there are valid points on both sides. While you could bolt a half axle to a wood frame, I personally wouldn’t – the day will come…

Conversely, a couple of big things to remember are:
1) the teardrop loads are not real high
2) the box, if built correctly can react a lot of those loads; so,
3) The frame can be a bit superfluous
Having said all of that it seems that there have been several posts about the Lil Guy trailers having some issues (sides separating from the center section). They are a production trailer and a quite a bit less robust than quite a few of the homebuilts; still, there is no way for a manufacturer to be assure that it is not being abused, so If I were to manufacture a trailer (if I could ever afford the cut in pay) I would probably make them overbuilt due to liability and warrantee considerations.

I’d also like to make a couple of comments on the last frame posted. Dad-gum I wish I could weld like that and it looks like there is plenty of beef there (in my own professional opinion).

[dh]

[quote="kennyrayandersen"] Dad-gum I wish I could weld like that.../quote]

Practice practice practice, and a good welder helps too.

Remember, those are profesional welds.

[kennyrayandersen]

Dad-gum I wish I could weld like that...

Practice practice practice, and a good welder helps too.

Remember, those are professional welds.

That's why I'll have mine professionally welded! It's as art really, and I've just never had that steady of hands. I can do plenty of other stuff - stained glass, lapidary silversmithing, wood working etc. but welding is a whole nother animal -- hats off to all the good welders out there. I'll get me a welder when I get the new shop built, but I suspect it will be a long while before my bead starts looking like that!

[teardrop_focus]

k.r.a.

Dad-gum I wish I could weld like that...

dh

Practice practice practice, and a good welder helps too.

Remember, those are professional welds.

k.r.a.

That's why I'll have mine professionally welded!

Indeed!


Update:

The rest of the chassis has been welded by a different person; a friend of mine who has welded many, thinner-wall 2 X 2 tubing structures for dynamic motor racing simulators...





Wheels arrived (3 weeks late, among other issues, but...) they look nice in black primer... with stainless beauty rings and inexpensive chrome baby moons.





Again, this design also depends on (at least) a plywood H-beam (I-beam on it's side) to add beam stiffness and was never intended to serve as a utility trailer in the usual sense of service. It is strictly a chassis for a teardrop trailer that sleeps two forward of the axle, has a well-equipped galley aft and one posessing minimal tongue weight. The teardrop body can and will be moved aft if necessary... (since we cannot now move the axle).