Hello and my new POP OUT teardrop.

[Mike46-TNT]

Hello all, my name is Mike and I’m located between Denver and Boulder in Colorado. I’m a designer / engineer for the furniture industry and use SolidWorks CAD software every day for my job.

I had a Coleman Colorado popup tent trailer for a short time but didn't like the bed size or soft top construction. I like the idea of the teardrop but wanted somewhere to stand. I’m willing to give up the rear galley for some space, and move the kitchen to the side.

My idea seems original, I designed it from scratch but after further research find that it has similarities to the other designs. It has a hinged drop floor like the Gypsy King Folding Travel Trailer, but uses cable stays instead of legs to support the floor. The lifting gate element is like many squarish back teardrops. I did steal the rear door / folding support from the Kampmaster. At first it didn’t have a side teardrop style door, just the rear door. Then I realized it could be used without opening up the back, if it had the side door.

Left rear isometric in open position, left hand tent and left side of box removed.

Left side section.

Right rear isometric in open position, left hand tent removed.

Right front isometric in closed position.

Left side section showing drop floor in raised position and lid closed.

I don’t have a lot of shop space and was looking for a method that I could build quickly, spending more time at the computer designing and less time in the garage cutting and assembling. All the parts will be CNC cut out of 5’ x 5’ Baltic Birch plywood, It is like a large “flat pack” or “ready to assemble” piece of furniture. One of the main features of how it’s constructed is the use of draw bolts and cross dowels to apply most of the clamping forces to glue up the box. After the glue has dried the bolts will be removed and replaced by glued in dowels.

This exploded view image shows how the unit will be constructed. I did this model to get the concept down and to be able to have prints for the CNC guys to quote from. I created a new model (all the other pictures) to work through all the details of space and ergonomics before I return to the model with all the individual parts. The overall concept is the same but some of the details have evolved, including the box joint which will now be half blind.

Exploded view of all plywood parts.

Typical method of construction and clamping.

Some of the Spec’s are:
850 Lbs dry weight.
Length: 11’ overall, 96” box, 36” Tongue.
Width: 60” box, 68” w/ wheels.
Height: 72” overall, 56” box, 16” frame.
58” x 80” bed converts to seating for 2.
2” tube steel frame.
Dexter #9 Torflex 1200 LB Axle
14” wheels, 24” dia tires.
10 Gal fresh water.
75 AH Sealed LA Battery

You can download a 3D PDF from THIS LINK. The PDF will NOT open in a browser, but if you download it you can open it in Acrobat Reader and rotate the model to look around. The download button is in the black bar at the top of the page. Fair warning, it’s a 17 MB file.

Any general feedback would be appreciated and there are a few things that I could use some advice on.

I’m still undecided about finish, epoxy resin or polyurethane. The plywood has a good face without footballs and a second face with footballs. It might be nice to show off the joinery and clear coat the outside.

If anyone has used a #9 Dexter torsion axle I’d like to get some specific measurements.

I’m thinking about using the Heng's 17511-G1 9" vent and was wondering if anyone has used this vent.

I’m hoping to work through the engineering this winter and get the axle and trailer put together in the spring, followed by the CNC cutting and assembly.

Thanks for looking, Mike

 

[Tony Latham]

Is that dry weight with the trailer chassis? If so, I think you're being optimistic. But nobody knows right now.

Here's the last Dexter #9 I've ordered:
Axle: #9 Torflex with hubs
• Trailer weight: 1500#
• Start angle: 22.5" Down
• Hub Face: 74"
• Trailer width: 59.5"
• Hub Diameter: 6.5"
• Lubrication: EZ Lube
• Brakes: none
• 1 ea. -Side mount kit
• Bolt Pattern: 5 on 4 - 1/2" (with standard studs)

That's for a 5' wide traditional teardrop I build 'em so the exterior 1/4" skin sits off the frame so the trim doesn''t ride on the trailer.

I think that one was $329 delivered.

Tony

 

[going2mars]

evening Mike46..
I was just looking at your innovative design... (I am also a designer NX7.5)
couple Q's.. when you remove the 'clamping hardware' will you be relying on a 90deg smooth glue joint only??
and... have you thought of purchasing a cnc router?.. the price has come way down lately.. couple links..
http://www.veloxcnc.com/vr5050x_cnc_router_4_x_4.asp (this one is 7600$)
http://pdjinc.com/ (I think this is slightly less $$)
I read where you said you were going to "have the parts cut" unless your brother-in-law owns the machine
wont that be several thousand dollars??..
with ideas as clever as yours you could build your TD and have a machine for your next ideas..
and/or any design changes or additions you could design/make yourself....just a thought..
I am new here... can we post STEP files?? or IGES files maybe??
your idea was very clever...thanks for sharing.. cheers g2m

 

[pchast]

Welcome.

That's a real interesting design.


When you sleep in the trailer or otherwise use it won't you be exceeding
the axle limits You've picked with the storage you accumulate?????????

You probably should choose a larger rating. Check with others that know!

 

[Tony Latham]

On reviewing it, I think you need to consider moving your axle back. As it stands, that little beast is going to be tail heavy and could be a towing problem. There are rules of thumb for tongue weight somewhere on this forum.

Tony

 

[Mike46-TNT]

I'll try to answer a few questions at once. In Solidworks I can specify materials for all the components. They have all been modeled to be of appropriate weight, Tires, Axle, battery, etc. even full water tank if I want. The wood and all the materials have specific densities, and because the software knows the volume it knows the weight. As it stands I know that the center of gravity is 42" behind the front of the box when the tank is full and the tongue weight is about 70 lbs. and about 40 lbs. when it's empty. The axle will probably move back a few inches to increase these tongue weights. I also may go up 100 lbs. on the axle. All will be adjusted with more precision as I proceed to my final model.

Going, The edges of the plywood parts sit in pockets that are routed into the sides and elsewhere 4mm deep (1/3 of the 12mm thickness). The picture of the hardware is not entirely accurate. The right angle joints are going to be a half blind box joint. The CNC shop in Denver that will do the job quoted me 1/2 hour machine time per sheet at $120 per hour. The sheets cost about $35 each so just about $100 a sheet fully processed. I'm looking at 12-14 sheets now. It's not the cheapest method but it may be one of the easiest.

Thanks for the feedback, Mike

 

[Mike46-TNT]

Tony, That is pretty close to what I'm going to spec. on the axle. Do you know how much it weighs, that's one of the only things where I'm estimating on the weight, My axle model came out at 60 lbs.

Axle: #9 Torflex with hubs
• Trailer weight: 1200#
• Start angle: 32deg Down
• Hub Face: 52"
• Trailer width: 48"
• Bolt Pattern: 5 on 4 - 1/2" (with standard studs)
- Short spindle

I'm wondering about how much offset wheel I can get away with on the #9 axle. I was thinking of using 14" car aluminum wheels, if they work. Is the axle you mention still in your shop, maybe I could provide you with a print that you could dimension for me.

Thanks, Mike

 

[Tony Latham]

78 pounds.

 

[starleen2]

You might want to consider an outside hatch to reach items underneath the bed are for the inclusion of the design. I have found it a PITA to have to lift the bed in order to get at something - usually something big. My latest build finally had an outside access hatch that allows me to reach under the bed area and store whatever under the bed. I don't have to stoop, bend over, scuba dive, or get on hands and knees to get at whats under there. I also have a removable front panel in front of the main bed just in case it's raining outside and I need to get something. Just a thought

 

[Mike46-TNT]

I am new here... can we post STEP files?? or IGES files maybe??

I'm not sure about a place to post files on the TNTTT site, I think we may be better off hosting them somewhere else and link to them, the 3D files can get large and it would save the site bandwidth. I did that with the 3D PDF I linked to above, It's on my Google drive. Has anybody downloaded and viewed it, I had no problem getting it to work. I use this PDF feature quite often when a client wants to get a better look at a new design.

You might want to consider an outside hatch to reach items underneath the bed are for the inclusion of the design. I have found it a PITA to have to lift the bed in order to get at something

I have thought of this but it's kind of tight, It's only a 12" high space and by the time I include a little space between the floor and cutout, the door is getting pretty small. I have seen some small doors but they have openings that are pretty small, 6" x 11". Making my own door seems to be the only option. On the interior the toe third of the bed platform will be bolted down, using the same cross dowel and bolt hardware. Under that panel will be the water tank and battery, and some storage that will be a PITA but hopefully wont be used much. The cushions will be 3 sections and stack in the toe section (see pic), the middle third is the hinged section and should be an easy reach from the seat. The hatch is still in play, just haven't made up my mind, thanks for making me think about it again.

The blue lines are the stacked up cushions at the foot of the bed, and the hatch in the raised position. I'm thinking of some hanging soft storage indicated by the blue lines at the top.

Mike

 

[Mike46-TNT]

g2m, I tried IGES but Solidworks broke it into all its component parts and created IGES files for each part. The STEP file worked and made one file, relatively small at 1.6 MB too.

3D Trailer Model in STEP file format

As for the 3D PDF's they will only work on Acrobat Reader, it's free from Adobe http://get.adobe.com/reader/

Mike

 

[going2mars]

g2m, I tried IGES but Solidworks broke it into all its component parts and created IGES files for each part. The STEP file worked and made one file, relatively small at 1.6 MB too.

3D Trailer Model in STEP file format

As for the 3D PDF's they will only work on Acrobat Reader, it's free from Adobe http://get.adobe.com/reader/

Mike

hmm.. I tried to import that 3 times... it wont convert... you can tell data is there.. it thinks about it.. but then says will not convert...will solidworks make a Parasolid file?? or a STL file??..
and you are dropping these on a google account?.. is that right?..

 

[DMcCam]

Hi Mike,

Interesting design for sure. A few things crossed my mind as I looked it over. With your ceiling gussets or spars you have very little head clearance both side to side and in height above the table. Even sitting down might be an opportunity to hit your head. From there the forward space narrows very quickly and with the gussets, could be a real head banger too. If you've ever been working in the eves of an attic you'll know what I mean. I agree with Starleen2, regardless of how you stack the bed, under bed storage is not as easy as you'd think. Of course you'll have to make the call based on how you camp.

It doesn't look to me that you have enough support for your hatch hinge to attach to. There will be a lot of stress on that hinge in use and your current design has it attaching to just the plywood roof. If possible, I'd move the aft gusset to the end of the roof edge and maybe double it for strength.

You might consider making a full size cardboard mock up of the space to test the design. It can be a real eye opener for sure.

I like the overall concept. It will be fun to see it come into being.

All the Best,

Dave

 

[Mike46-TNT]

Dave, Here’s a picture to clarify the sleeping arrangement, it’s backwards from a traditional teardrop, My head will never get down to the front of the trailer. The mannequins aren't perfect scale when seated. From seat to the top of my head I sit at 36”, and there is 37” from the seat with compressed cushion to the spars. This was mocked up in one of my baths, if you have a 60” tub that sits at the end of a bathroom you can sit at the head of the bed. I taped the hatch profile on the wall, and stretched tape across the 60” opening where the aft spar is. It’s easy to stand into the 72” high space and sit down on the edge of the tub without hitting your head. The aft spar, as well as the roof behind the aft spar, will be double thickness.

Thanks for the feedback, Mike

 

[Mike46-TNT]

Because of the way I’m going to have my plywood cut by a CNC router, when cutting the door opening I will use the cut out piece for the door without any waste. The router will also cut the filler and door stop, along with ¼” dowel holes in all the parts so they will all align precisely. I was also thinking of using this method for the windows, CNC route ¼” Lexan to fit the opening. The seal would be either foam or rubber bulb style. McMaster has several types in both materials. I know I'll have to get some samples in but I was hoping the experts could give me some direction.

Section through door and window.

From McMaster catalog

From the look foam may be too soft.

I’ll be using Living Hinge for all the hinges in my build, doors, windows, lid, floor, hatch, table leaf. Probably this one from Monroe.

Mike

 

[fireball]

While the design is neat and original, I'm not sure I really like it

Are you really going to be sitting down inside the teardrop?

It also seems like a lot of effort to have a small standing interior space. What are you going to do with that space?

I also think it's a big concession to not have a proper galley. That is a pretty big appeal of the TD - the easily accessible and always ready-to-go kitchen area.

Perhaps the type of camping you like to do or for your needs it works, so maybe I am just asking what are your design goals? Please don't take the wrong way

 

[Mike46-TNT]

Scott (g2m) asked me a few questions in a PM that were good points to get in the full post.

...and many Q's..
do you own the trailer part already?
is that why it has a narrow wheelbase?
what type of roofing are you thinking?..
after you fold out the addition (love it) what supports it?.
in the addition do you have a vertical hard mount?.. for wind
so the top doesn't lift n fall in a storm you may be camping in??
the side door is 33.5" off the ground??? that's a step or two..
any insolation?
I'll stop before you are pulling your hair out ..or mine..
hope you don't mind the Q's..
call it fellow designer curiosity...
cheers…

Scott, the trailer is that width to keep the whole unit as narrow as possible, I wanted the 60" width of the box because of the width of the plywood and as close to queen bed as possible. But because of the axle, if I put the wheels on the outside of the box, it would be 10" wider than it is now. The 60” wheel track also fall right in line with my Subaru Forester wheels in this configuration and it's not wider than the car, all that makes negotiating tight fire roads easier.

No roof, just finished plywood, probably epoxy resin. I’m hoping people will chime in on this point. The trailer will be under tarp when at home. It seems like it goes both ways on this forum, some people use a roof cover some don’t.

Google “Kampmaster” and look at the images. This is where I got the idea for the rear door, befor that it was going to be a tent door and the lid was going to be supported by some sort of prop. The lid will be bolted (see “Typical method of construction and clamping” picture) to the door and the door is attached to the floor with a continuous hinge. Still thinking about the mechanism that keeps the door straight when in the open position, could use a latch or ribs and a four of the same bolts.

The side door is an afterthought and probably will only be use in a pinch, so yes it is high at 33 1/2" off the ground but easy enough with a step stool. I could lower the whole unit but I want the ground clearance for those same fire roads.

Happy to answer any question, Mike

 

[Mike46-TNT]

FIREBALL05, you make good points, let me try to address them. The standing interior space was a requirement after many years of tent camping and wanting a place to stand without having to set up a monster tent. Then my year with the Coleman Colorado reinforced this idea. A place to stand and change, sit in a chair, sit on the pot (bucket). You're right the table probably won't be used much, I think sitting on the head of the bed will probably be used more, than the other person can sit in a chair on the floor. I’d rather sit outside while camping, but sometimes rain or bugs make that difficult.

Never had the galley, so nothing to change from the way I’ve been camping for years. You probably didn't see the sink and stove space on the right side of the unit unless you downloaded the 3D PDF. here’s a picture to clarify. The canopy is low on the agenda but doable.

Maybe it’s not a teardrop, we can call it a Tiny Travel Trailer if that's more accurate.

Thanks for your feedback, Mike

 

[ctstaas]

Hi Mike,
Most of this conforms to personal user preference but axle placement will effect performance and safety so is more of a technical issue. The opinion I agree with most thinks the axle should be at 65% of the length of the load (Do not consider the tongues length when placing). Closer then 50% of the load and your trailer will skip around like towing a wild jack rabbit. So, technically from 50% of the load to 65% of the length of the load. More then 65% and the tongue weight goes up fast. My 4x8 weights #1050 ready to camp. My frame is 1 1/2"x0.065" and 3"x 3/16" for the tongue and axle tube. My torsion axles bolt onto plates welded to the axle tube. I could have gone down to 3"x 0.120" but the thicker material doesn't add that much weight compared to strength. When I buy steel it's by the pound so price comparison is easy to figure also. I would advise to buy the axles or at least consider the mounting when you design the frame. I built my frame, then bought my axles and am a couple of inches off (too far back). It was before I found the site so don't tell anyone. My pictures are posted in the member area under "C" on page 25 for reference. You'll find lots of opinion on this site so pick the one you like best. When designing my cabin I consider materials that are readily available for price, joinery and weatherproofing concerns.
Enjoy, Chris