Ultralight Design?

[Kevin A]

I dunno, BG,

Ya think that table will hold up all that steel during your trailer build?
Where do ya plug in the welder?

[bg]

I'll only be picking up 260 lbs of steel in the morning. 'Course part of that is for Julie's trailer to fix my boo-boo , and I'd rather not make an additional trip for something trivial.

As far as the welder, I just slide out the stove and plug'er in. In reality, I'm going to 'borrow' a neighbor to help me get the table moved outside, where the real plug for the welder is.

I'm almost positive I'm going to hate myself for selling the little mig I had when I'm doing all of these joints; Probably going to be about 100 joints in the frame work, but all of the strength should be in the main frame, not in the skins. I plan to leave the interior unfinished for now, just in case I do have a need to add more framing later on.

I was at HD earlier and noticed plastic 'drive rivets' near the FRP/wallboard. They're $13/100 pack which really isn't that bad once you consider I wouldn't have to buy a rivet gun. They install with a 1/4" drillbit and a hammer, 2 drillbits should do the whole project. I do intend on using the PolyWall product that HD carries, it is very similar to Poly-Max, and I'm willing to take a chance that it won't last.

Comments/critiques, please!

[mikeschn]

Okay I've added the spars and the interior cabinets to the ultralight.

The spars add 14#
the bulkhead/cabinets add 54#.

So our running total is now 292#

All that is left is to glue on a roof skin, add windows and door handles...

I think we'll be pretty light...



Here's a wrl if anyone is interested... BTW, the TV doesn't count towards the weight!

http://www.mikenchell.com/Ultralight/ul ... binets.wrl

Mike...

P.S. The wrl's are starting to get large, so you might want to use your broadband connection!

[Miriam C.]

WRL's are good. Looks good. At this rate I can modify that to a 5x8 and pull it with my lawn mower.

Will making the cabinet removeable make it a lot heaver?

Miriam

[mikeschn]

:thumbsup:
WRL's are good. Looks good. At this rate I can modify that to a 5x8 and pull it with my lawn mower.

Will making the cabinet removeable make it a lot heaver?

Miriam

The cabinets are screwed in thru the framing on the outside. To make your cabinets removable is do-able, like using barrel bolts for example... but then you lose the structural support that the bulkhead walls give it...

Mike...

[angib]

Do you think that this latest frame design with the tongue not attached to the axle structure is robust enough for a full weight, (i.e., 1000 lbs. dry) trailer?

Greg,

I don't think so - you're talking about a trailer that's three times heavier. It isn't fixing the tongue to the body that I have a problem with, as the trailer gets heavier, but using a single tongue that ends in the middle of the floor.

I hope Mike will now add a post showing the alternative A-frame tongue that I sent him for the Ultralight, as his 3D lighting skills (or software!) are much better than mine. I believe this could be scaled up to a heavier trailer, using 2" square tube, rather than the 2" angle that is sufficient for the Ultralight. By using an A-frame, the back end of the tongue(s) can now lie right under the sidewall which is as solid a mount as you could want. However on the Ultralight this point is right at the front of the axle mount angles, so the length without a chassis drops to zero.

I should stress that all this talk of fixing the axle and tongue separately to the trailer body assumes several things:
- The trailer body is strongly constructed with proper glued joints onto fillets - no screws into the end grain of ply or such like.
- The door openings have decent-sized frames above and below (say, at least 3-4" deep).
- The roof/front panel meets the floor at an angle of at least 45deg to the horizontal - vertical is best.
- The attachment points for the axle and tongue are properly reinforced, either by bolting through plates inside the trailer or by using both horizontal and vertical fasteners (I would allow lag screws here, but I'm probably alone in that).

I don't want anyone to get the idea that I'm suggesting that bolting the tongue to a 3/4" ply floor is enough!

Andrew

[vairman]

Mike how bout this for your side walls....

1/2" thick ply 3"thick beams? then maybe cover the outside with 1/8 luan and leave the inside uncovered?


Just a thought


Greg

[mikeschn]

Greg,

Certainly using plywood framing and puting it on the inside is a thought. The Problem comes when we try to drive screws into the endgrain of plywood. I've split so much plywood doing that, and it doesn't have the holding power of solid wood...

Let me think about that some more...

Mike...

[Miriam C.]

I wrote

At this rate I can modify that to a 5x8 and pull it with my lawn mower.

Sorry if I caused Andrew and Mike a stroke. No way would I modify a design in progress.

However, My mommy's mind tells me this is a perfect place for Andrew's Warning. I may be more cautious than most.

Keep up the good post, and the pdf's. Luvin it.
Miriam

[vairman]

Greg,

Certainly using plywood framing and puting it on the inside is a thought. The Problem comes when we try to drive screws into the endgrain of plywood. I've split so much plywood doing that, and it doesn't have the holding power of solid wood...

Let me think about that some more...

Mike...

Why would you have to drive the screws into the endgrain??

Greg

[GregB]

Andrew,

Would this design be along the ideas of what you're referring to? Say using 2x3x3/16" angle (or even C channel) with a 2" tube tongue?


It would be more robust and yet still lighter than a traditional chassis. I bring this idea up because if you notice in Mike's pic of the trailer parts there is a piece that would marry the a-frame to the tube of the tongue. Then the rest can be bolted together until you can have it all welded. I suspect that the rectangle behind the a-frame really isn't even needed, its just there to make me feel better.

GB

[bg]

Oh boy! I've missed tons of fun stuff today.

Made it down to the steel supplier this morning and picked up this. Believe it or not, they didn't charge me extra for the cuts!


And so far I've managed to get one side framed and tacked:


I'm putting some other pictures in the the link in my signature.

After I finish lunch, I'm going to get the other side tacked up, and hopefully get to connect the sides before I run out of daylight.

[bg]

For some reason or another, I'm tired.

[bg]

That was my stopping point for the day. Picked up the tools, unloaded the trailer, and threw a tarp over it. I can already tell that I did buy more steel that I'll need, but that's not a bad thing Almost evey scrap piece has been invaluable in clamping. I did change my framing layout slightly, but I feel that it'll be more functional with those changes. I'm going to get this 'mocked up' and Julies frame clamped, and go to town welding either tommorrow or wednesday. I will be going with an A-Frame style undercarraige, Simple, quick and strong.

[mikeschn]

BG,

It's looking good... You're definitely the first to build this ultralight... Hey, you even beat me to it...

Mike...