Step 1: Getting the measurements - Chest
Getting accurate measurements is a very important step as proper fit is key to a comfy and safe dog. If you are designing the cart yourself use a tape measure to determine the measurements. However, if you are having a designer build the wheelchair, take and send pictures so that the designer can have a feel for the dog. First, the measurement needed is the circumference of the chest and the length of the rib cage. With those the basic shape of the main frame can be made. Then, take a third measurement of the width between the nubs on the chest.
Step 2: Getting the measurements - Chest continued
The third measurement of the width between the nubs on the chest shows how big the cutouts need to be to allow room for what nubs they do have. (Be careful to not get bitten, as they may not be too happy about this whole process).
Step 3: Getting the measurements - Height
For getting the height you want to hold the dog in a natural standing position. Be sure the legs and back are straight with the chest at a natural level. The proper height is extremely important for designing of the fork for stability and comfort. Adjusting the height of the fork and the angle that it mounts to the frame can completely change how it works for the dog. If your dog seems to be tipping forward, check the height and maybe make it a little taller. You may also consider adjusting the angle and moving the forks more forward. The opposite goes if it seems like too much weight is being placed on the dogs back.
Step 4: Printed items
Frame x 1
Fork x 1
Rim x 2
The main printed parts are the frame, fork, and the rims. The other printed items are not completely necessary, but help in adjusting and using the cart. They are the strap loop and spacer.
Non-Printed Items:
M5 nut x 2
M5 locking nut x 2
Bearings size 5x14x5 x 4
M5 x 30 Pan head machine screw x 2
Flat Phillips Machine screws 1/4-20 x 1-1/2 x 2
hex Nut 1/4-20 x 2
1 inch nylon strap x enough to wrap around dog about 4 times
Metal loop
3mm thick craft foam sheet x 1
Double sided Velcor x enough to wrap around dog about 2 times
Sewing kit x 1
Spray glue x 1 can
Superglue x 1 bottle
Step 5: Making the straps
The straps are made of 1-inch wide nylon strap the author purchased from Hobby Lobby. There are two main straps and each one needs to be roughly 1.5 times the circumference of the chest. On one end a metal loop will either be sewn or secured with super glue. Once that is done you will want to place the strap in the frame as illustrated and mark the edge of the frame on the strap. Then lay the strap out and mark the circumference of the dog starting at the metal loop. Fold the strap at the circumference mark. With the strap folded back onto itself cut the extra where it lines up with the mark from the edge of the frame. Now the metal loop will fit at about where the fold is and the other mark shows where the edge of the frame will be. Knowing that you can attach the Velcro. Copy that strap to make a second. The third rear strap is very simple. It is made using double-sided Velcro. It should go around the dog and overlap a few inches. Then just cut the width so it with fit in the two rear slots. To attach the straps to the frame, the author used simple superglue. Caution: Just be careful not to glue yourself or burn your eyes. Place the straps on the inside of the frame as pictured with the loop up against the edge. Mark the outline of the strap and then remove strap. Using the outline apply a small layer of glue to cover that area, then carefully reapply the strap and hold until the glue sets. Repeat this step with second strap. The third strap is not installed until later and a thumb tab can be printed out and sewn on for easier use.
Step 6: Adding the chest padding
First, take the spray glue and coat the back of the foam sheet. While the glue that is drying, cover the straps so that it does not get covered with glue. Then carefully place the foam into the frame pressing it in and working from the middle outward. Now go around and trim the extra off. Leave about a 1/4 inch of material, pull around the edge and superglue. Let the glue dry, trim and flush with bottom. Doing that makes sure that any part the dog skin touches should be covered in foam. Finally, cut slits for the fork bolts and the rear strap. You can now install the rear strap as pictured. Just ensure that the soft side of the Velcro is on the inside towards the dog.
Step 7: Assembling the cart
Now you're almost to the fun part. All that you have left is to assemble your puppy’s new cart.
1. First step is to install the 5 millimeter bolt into the bottom of the fork. Due to the tight space a stubby or 90 degree screwdriver can be very helpful. As you thread the bolt through the fork you will want to install one plain nut on each bolt. Continue tightening the bolt down till secure insuring that the nut lines up into the cutout in the fork.
2. Now its time for the wheels. Each wheel rolls on an identical inner and outer bearing. The easiest way to press the bearing into the wheel is to use a 5-millimeter bolt and a couple over size washers to squeeze the bearings into the wheel. You will want the over size washers to make sure you are only putting pressure on the outer race of the bearing. With bearings installed it is time to place the wheel onto the fork. Then place one locking nut on each bolt and tighten till it just makes contact with the rim. Now spin the wheels and watch how well they spin. If this seems to drag, try loosening the nut just a little. If they spin freely, but the wheel has a lot of side-to-side movement, try tightening the nut. Continue adjusting until your wheel spins freely with little wobble.
3. The third and final step for assembling the cart is simply installing the fork onto the frame. On the frame, you will see some holes. The number may very depending on the design of the cart. Pick two that are side-by-side and place a large machine screw in each one from top to bottom. Now install the fork onto the two bolts protruding from the bottom of the frame insuring that the angel of the fork is forward (Number on fork facing forward). Install one plain nut on each bolt. Continue tightening the bolt down till secure insuring that the nut lines up into the cutout in the fork.
Step 8: Installing the Pup and Adjusting
Placing the dog into the cart is pretty straightforward. Place their chest up against the front of the cart insuring there nubs and shoulders clear the cart. Then strap them in. The straps need to be secure but be very careful not to over tighten and injure the dog. If your cart has a third strap it is fastened loosely towards the hip to help support the cart and keep it level with the dog.
The moment you have been waiting for since you fell in love with your little two-legged companion. Its time to place them on the floor in there new cart.... and nine times out of ten they just look at you scared not having a clue what to do. But no worry with time, proper training and adjustments they will learn to use their cart. With them now in the cart, take a good look at how the are standing. Make note of if their back is straight or if there front seems to be too high or low. If the cart is not sitting correctly, it will really affect how fast they learn.
Here are some examples of problems and how to correct them. The main issue is sagging or curling the back.
Sagging in the back can be due to the wheels being angled forward to far, the forks being place to far forward on the cart, the cart need more support in the rear or simply the dog just has to get used to it. Fixes are to decrease the fork to a lower number (Less forward angle), more the forks to mounting holes further back, modification of the frame of the cart and practice with the pup helping them stay level.
Curling is the exact opposite of sagging. So to accommodate, you should increase the fork number, move the forks to more forward mounting holes and again just work with your dog to try and get them used to it. One extra cause for curling I have seen is the forks being two short and the front of the dog being to low. Easy fix is to install a space between the fork and frame or replace the fork with a taller one.
Step 9: Carts in action and Upcoming updates
The author is continuously working to improve the carts to make it easier for the dog and easier to produce while keeping the build cost a low as possible. One of the newest ideas the author is working on is with making the frame extendable. This will make it possible to print carts for larger dogs on smaller printers as well as adding another way to adjust the cart for the dog. Another couple things in the works are anti-tip forward bars to keep the puppy from tipping forward on their nose and wheels with replaceable tread.