Ultra-portable Dog Cot for Small Dogs

My daughter, who likes to take her small dogs camping with her, asked me if I could design and build a more portable and lighter-weight dog cot than the one she currently uses. The result was this collapsible dog cot that’s patterned after my lightweight camping chairs. Set up, it's 2 feet by 2 feet and easily supports a small dog up to about 25 pounds. It packs down to about 15 by 5 by 3 inches and weighs about one pound.

I designed the hub in Fusion360 and printed it in ASA filament, and the legs are made from 11mm diameter aluminum tent poles, with 3D-printed end caps that protect the pole ends and secure the shock-cord that holds the cot together so there are no parts to lose. The center post is made from heavier 13mm diameter aluminum tubing with a thicker wall. The cot material is ripstop polyester and the pole sockets are made with heavier outdoor polyester.

The project requires access to a 3D printer, a means for cutting the aluminum tubing to length and a sewing machine. I also used a small file and a countersinking drill bit to dress the cut ends of the aluminum tubing.

If you want to make a version of this for heavier dogs, you'll need to modify the design for large tubes, and find a source for them (which I was not able to do). The aluminim tubing needs to be 7000 series alloy designed for tent poles and camp chairs, and if you're looking to support a larger dog, my guess is that you'll need a diameter of about 16mm.

In addition to the tools mentioned in the introduction, I used the following supplies to build my cot. I know that I’d be making several of these so I bought larger quantities than are listed below.

First a note about sourcing your aluminum tubing for the legs. The tubing you want is an alloy that is specifically made for tent poles, which is a 7001 alloy. I originally tried using a 6000 series alloy (more commonly available from hardware and metal providers) because it was available with much thicker walls than the tent pole tubing that I could find. I thought that the thicker walls would equal stronger poles, but this was a mistake. When I assmbled my cot using the 6000 series alloy, the tubes simply bent when my dog laid on the cot, and after bending, they stayed that way. The alloy used for tent poles are intended to flex without bending, and this is exactly the behavior that you want for an application like this. So if you want to adapt my design for a heavier dog, you will need to find larger poles, but make sure that they are still the 7000 series alloy. And in any project where you're planning to use aluminum tubing where strength and lightness is a concern, pay attention to the alloy you're using. It really matters!

With that noted, here is the list of supplies that I used for my dog cot.

Cot Frame

1. 11mm OD x 520cm length aluminum replacement tent poles (14 sections). I bought mine from eBay for around $34, shipped to the US. There are several sellers offering these and the price varies considerably. You’ll only need 8 of the sections to build a single cot.
2. 13mm OD x 9mm ID x 12” long aluminum tubing for the center post. You can buy these on Amazon from a variety of sellers, but current listings includes 2 pieces for about $9 US.
3. ASA filament. I used Polymaker Polylite ASA and had good luck with it in my Flashforge Adventrurer 5M Pro printer. I chose ASA because it has great strength and durability like ABS, but has better UV resistance and is recommended for outdoor projects for that reason.

Cot

1. 1 yard of 60” wide ripstop polyester for the main bed material.
2. About 1-1/2 square feet of heavier outdoor polyester fabric for the pole pockets. I used leftovers from another outdoor sewing project, but you could also re-purpose on old backpack or duffle bag for this material. Ultimately you need 4 pieces that are about 7 inches square.
3. 3/4” wide polyester webbing (strap material) to reinforce and finish the inner radius edge of the pole pockets.
4. Pre-folded polyester bias tape for finishing the outer cot edges. You’ll need about 10 lineal feet.
5. Polyester thread suitable for outdoor projects.

I designed the hubs using Fusion360, and based my design off the Flexlite camp chair that I own. One critical thing about the design is the location of the center post. The center post goes far enough into each hub so that the load from the cot tubes is carried by the aluminum post, rather than just the plastic hub. This is essential because 3D printer parts are weakest along the layer lines, so if the post is not deep enough into the hub, the hub can snap when the cot is assembled and tension is applied to the cot tubes.

Once you’ve downloaded the .3mf files, you’ll need to slice and print them for your printer. I’d recommend that you get the settings right for your filament before printing the hubs, because they are longer prints. If you need to adjust the dimensions or just want to change the parts in any way, I’ve also included the Fusion360 archive file (.f3d extensions) so that you can edit the parts as you see fit. Apologies for the lack of discipline in editing those files, since I am still a bit of a beginner with Fusion360).

I printed the hubs with the outside ends down (resting on the bed), and supports enabled. With this orientation the slicer will add supports for the holes for the cot legs and supports and the interior connecting holes for the shock cord, which I found to be unnecessary and difficult to remove. To remedy this, I used the support paint function in Orcaslicer to remove supports for the shock cord holes and for all but the outer portion of the leg and cot support holes. I’ve tried to show this in the included images.

I printed each hub separately, and found that I got the best results for the leg caps by printing them in batches of 4. I printed them on end and included brims to keep them steady on the printer bed. You'll need to test your settings to ensure that you have high-enough printing temp to ensure good layer adhesion, or your end caps may fail.

After printing the parts, I removed the supports and cleaned up any rough areas with a small grinding tool and files, and made sure that all of the tubes could be inserted easily. If you end up with any that are too-tight, you can ream the hole with a drill bit or round file.

While your hubs are printing, you can prepare the aluminum tubing for the cot legs, support tubes, and center post by separating the tent poles, cutting each piece to length and finishing the cut edges to remove burrs. Here are the basic steps.

1. Disassemble the tent poles by unscrewing the aluminum ends, untying the shock cord, and then removing the cord from the tube assembly, leaving separate tube sections. On my finished cot, the lengths of the pieces are as follows: cot support tubes (the upper pieces) = 14-1/8 inches, legs = 12-3/8 inches, and center post = 11".
2. Cut aluminum to length with a fine-tooth metal cutting blade on a bandsaw or jig saw. I'd avoid using a tablesaw because the aluminum can easily catch and ruin the end. When cutting, be sure to remove the end with the insert since you want to end up with aluminum tubes without the normal tent pole ends.
3. Remove the burr on the inside and outside of the cut ends of the tubes. I used a countersinking bit to ease the inside edge, and then used a small file to remove the outside burr.

You are now ready to assemble the cot stand.

Assmbling the cot stand involves threading the shock cord, attaching it to the first plastic tip, adding sufficient tension (pulling the cord mostly taught), and then finishing it by attaching the other plastic tip. Here's a step-by-step:

1. Work with the full length shock cord (it's easier to cut as you go) as shown in the first photo, and thread the cord through the tube, then the hub, then the other tube. Orient the tubes so that the factory end inserts into the plastic hub. This is a good idea because even though you've removed the burrs from the end you've cut, it's probably still not as smooth as the factory end, and when the cot stand is folded, the shockcord will rub against hub end of the tubes.
2. Tie the end of the shock cord to itself below the plastic tip.
3. Pull the cord taught (but make sure there is still room for it to stretch) and cut the cord WITHOUT LETTING IT SPRING BACK INTO THE TUBE.
4. Melt the end of the cord with a lighter to prevent fraying.
5. Thread the cord through the other tip, then tie it shown and insert the cord and plastic tip into the tube.
6. Repeat this for each tube assembly.
7. Finish with the center tube.

You should now have a stand that snaps and holds together firmly, but can be pulled apart and folded just like a camp chair.

As you can see in the first photo, the tube pockets are patterned after the pockets on my Flexlite camp chair. They are made with heavier Cordura polyester (the cot is lighter ripstop fabric) to withstand the stress applied to the pockets when the cot is assembled and a dog is on-board. The basic process for creating the pockets is to create the pocket with the Cordura fabric and then attach wings made from small pieces of cot fabric. I used 3D printed templates to allow me to make consistently sized and shaped pockets. Here are the steps for creating the tube pockets.

1. Cut 4 pieces of the heavier fabric into 3-1/2 by 6 inch rectangles as shown and fold them 2-1/2" from the top edge.
2. With the fold at the top, hold the folding template along the bottom and fold the corner in to match the template. Holding the fabric in this position, place a small ruler along the raised edge guide on the template and mark along the inside edge of the ruler. This is your seam location guide.
3. With the fabric still folded and held in place, remove the template and mark the fold location by tracing around the folded-in corner. You could also just hold the corner in place with a small piece of fabric adhesive.
4. Sew the folded corner in place by first sewing along the outside edge of each of the folded-in corners, and then sewing along the marked lines to form the pocket.

You're now ready to finsh the pockets by adding wings and cutting to shape in the next step.

To finish the pockets and prepare them for sewing to the corners of the cot bed fabric, you need to add material to each end (I call these the wings) and then cut the wings to shape. The pocket assemblies are assymetrical to more clesely match the geometry of the cot tubes. In order to keep the shape of the finished pockets consistent, I made a 3D printed template that I can simply place over the Cordura pocket and trace the finished pocket shape. Here are the steps for sewing the pockets together and cutting them to final shape.

1. Cut the wings from the cot material. You want them to be oversized so I made my pieces about 4 inches square.
2. Fold about 1/2 inch over on one edge of the wing material and position on the Cordura pocket as shown in the picture. You can use the 3D printed template to help you ensure that you are leaving enough material to trim the finished pocket to sixe later. The folded edge of the wing should overlap the seam for the pocket by about 1/4 inch so that you can sew the seam to attach the wing about 1/8 inch inside the original pocket seam. this ends up creating a narrowower final pocket.
3. After sewing all of the wings on, use the template to mark the final shape of the pockets and mark them. IMPORTANT: be sure to flip the template for two of the pockets so that you have two right-hand pockets and two left-hand pockets.
4. After marking all of the pockets and ensuring that you have two of each different pocket position, cut along the marked lines to finish the pockets.
5. Trim the excess fabric from the back of each pocket, as shown in the photo. this will make it a little easier to sew the pockets to the cot fabric.

You are now ready to position and sew your pockets to the cot fabric!

When sewing your pockets to the cot material, you're aiming for a tight fit so that you have to stretch the fabric onto the cot tubes and flex the tubes a bit. If you end up with too loose a fit, you will have to remove and re-sew pockets, but if it end up too tight, you can re-cut the cot tubes until you get the right fit. Here's the process I followed for this.

IMPORTANT: when positioning each pocket make sure you pay attention to the asymmetry of the pockets. The angle of the pocket should match the angle of the cot tube.

1. Cut the cot bed about 2 inches oversize in each direction.
2. Cut a piece of the polyester webbing to wrap the inside curve of the pocket, making sure to leave about 1/2 inch of webbing at each end of the pocket. I folded and ironed the webbing so it would hold it's shape while sewing, and also tried to pre-shape it into a curve. I then tacked it in place with straight pins so that it would stay in a curve while sewing.
3. Sew the first pocket in place just along the inner curved edge (the outer radius of the pocket is sewed when you finish the cot edges in the next step.
4. Place the leg assembly on the fabric, insert a cot tube into the pocket, add a pocket on the adjacent cot tube, and stretch the fabric while compressing the tube assembly (to ensure that the cot will be sufficiently taught when assembled), and mark the location of the next pocket.
5. Sew the next pocket in place.
6. Repeat the steps above for each remaining pocket.
7. Check the fit. It should be a little difficult to stretch the fabric onto the leg assemby (this will ensure that the cot is nice and taught to start, since it will sag a bit with the weight of a dog on it). If it's too tight, you can trim a little length from each of the cot tubes until you have a good fit.

At this point you are ready to finish the sewing on the cot by trimming it to size and adding a nice edge finish.

To finish your ultralight dog cot, the last thing you need to do is cut the cot material to final size (remove the excess beyond each pocket) and finish the cot edge with the bias tape. In the process you'll also be sewing in the outer edge of each pocket. After trimming the two remaining edges of the cot material, I cut around each pocket so the cot material was even with the outer radius of each pocket.

To sew the bias tape, I first cut it about 6 inches longer than I needed, and started sewing it on a couple of inches from the first corner. I then tacked it in place with some straight pins to follow the curve of the corner and sewed the corner. I then tacked the next staight edge and sewed that, repeating this process for each corner and stright edge until I was close to my starting point.

To finish sewing the bias tape, I trimmed it about 1-1/2 inches beyond the starting point of the tape, folded about 1/2 inch of the bias tape in on itself, and then finished sewing it with about an inch of overlap over the starting point. I'm not at all an experienced at sewing this type of thing, so there may well be a better way to finish this.