narrative of Kyler's wagon projects

wagon 00

I built "dog wagon 00" in June of 2003 as our oldest dog, Garbo, was losing his battle with osteosarcoma We had amputated the affected leg but while in California we discovered that the cancer had aggressively spread to his lungs. He had been able to get around well on three legs but his decreased lung capacity left him tired after the slightest walk once we returned to Indiana.

We love to take walks in our neighborhood and on the wonderful trails nearby. Leaving Garbo at home was not an option. Carrying him wasn't an option either. (I had a Teeft lift harness with me when he first got tired on a walk but my back still strained from just carrying him under a mile.) I needed a quick solution.

At the same time that Garbo was slowing, our youngest, Grazie, was causing me problems by pulling ahead. She was usually coupled to Garbo during walks so that he could keep her in line and she could bring him when I called. (The girls have great recalls so I couple them to the boys.) With Garbo weakened, I let him walk on his own and tried to control Grazie on her own.

When I found Grazie (~7 years earlier in the Celery Bog where the trails are now), I decided not to teach her to heel. I wanted her to pull (me on Rollerblades, scooter, sled, ...) without constantly looking back at me like the other dogs did. Well, now I was paying for it. My arm ached; I was in quite a bit of pain from being split between her pulling ahead and Garbo dragging behind. It was during one of these "wishbone moments" that I was inspired to remove myself from this painful balance of force.

My goal in assembling my first wagon was to use readily available parts. I bought the Radio Flyer ATW from Toys 'R' Us and used basic aluminum and miscellaneous parts from local hardware stores. The only delay was getting a Cascade carting harness from Black Ice.

The modification of the wagon for dog pulling is primarily a crudely-bent piece of 3/4" aluminum tubing. It's reinforced by a piece of channel aluminum where it connects instead of the normal wagon handle using a couple of small eyebolts as anchors for the hitch pin. I'd always intended to redo everything much better but the wagon has worked beautifully without modification.

That wagon was a key part of Garbo's final days with us and enabled us to better enjoy those days. We're sure that it also helped keep him alert and happy longer because we were able to get him out of the house and engaged without tiring him. It was much more pleasant to be able to enjoy spending time outdoors with Garbo like we always had, instead of just watching him wither on the bed.

After Garbo died in June of 2003, we continued to take walks with Grazie pulling the wagon. It was tough to answer the "Where's the three-legged dog?" questions but it was great for her to have a job, especially one that didn't include pulling my arm. Besides giving rides to neighborhood and family children, we increasingly used it to help Gable. Gable had suffered paralysis of his left limbs from a fibrocartilaginous embolism (FCE) in October of 2001. While we are thrilled that he recovered, he still drags his left paws, especially when he's tired.

So...Gable rides in the wagon a lot these days. It works perfectly for us, giving Grazie a job and giving Gable a break, but what's been most amazing is how people react to it. Drivers have stopped their cars to watch and take photographs. A photographer for the local paper left a ribbon-cutting ceremony to take a photo. We often encounter people who just keep repeating "That's the cutest thing I've ever seen." (Kitty gets a little tired of all of the cute jogger girls doing this on the trails. Fluffy dogs and red wagons - oh, if I'd known about this when I was young and single...)

The wagon has become quite the catch-all. It started holding poop bags, but it's just so handy that Grazie ends up toting coolers with cold drinks, water for the dogs, dishes, Kitty's purse, my hat, jackets, groceries, a small pop-up tent (for use at restaurants), blankets, ... Considering that the wagon alone weighs 46 pounds and Gable weighs about 40 pounds these days, it seems like a heavy load for my 50 pound nine year old girl to pull on those wide tires. Her frequent off-road forays make me think that it's not too much but I'd like something easier to pull.

wagon 01

In California, Greta and I survived for awhile without a car by using my bicycle with a trailer. Besides taking us where we needed to go, it provided a fun way of getting groceries and even came in handy as an off-road 802.11b network checker. I knew that it could carry a heavy load without great rolling resistance. My Burley Cub remains in California and I wanted another trailer for my bike. In order to try something a little different, I got a BOB Ibex that Grazie rides and runs (tethered) beside but I kept thinking about getting a larger bike trailer that could also serve as a low-resistance wagon for Grazie to pull.

I was fortunate to be able to attend a drafting workshop hosted by the Kentuckiana Bernese Mountain Dog Club in April of 2004. It was the first time that I got to see bicycle trailers modified for dog carting. I was inspired to make my own.

I had been eyeing trailers at our local bike shop, Hodson's Bay, for months. I had been spoiled by the hard floor of the Cub; it was great for hauling dogs and I was reluctant to get a soft-floor trailer such as the Trek Transit Deluxe they had in stock. I also didn't think that I liked the wrap-around frame of the Transit. Biking near the SF Bay, I'd had difficulties maneuvering the Cub through the barriers on the trails. I thought that having anything more sticking out beyond the wheels would make the situation worse. I finally decided that I could mount a carbon fiber plate to stiffen the floor and that the frame around the wheels could help slip through tight spots instead of catching like the Cub's hubs did. (Trek calls the frame a "full wrap around aluminum bash guard". I like the sound of that.) The Transit weighs about half as much as the Radio Flyer, quickly folds flat (The roof goes down.), and has quick-release 20" wheels. With the wheels removed, it's easy to carry the Transit under my arm. (That will be handy the next time we have a room on the second floor of an inn.)

The Transit does seem to be tough enough to handle the abuse we're likely to give it. Because it's made by Chariot, there are a bunch of great accessories. The accessory that interested me most was the stroller kit. These castering wheels would stay out of the way of the pulling dog, unlike the single centered front wheels on typical trailer conversions. I wanted a stable four-wheel vehicle (wagon) but I like the easy turning of a two-wheeler (cart). The castering wheels are a simple answer.

Although Chariot has conversions for strolling, jogging, biking, hiking, and skiing, strangely enough they don't have a dog pulling conversion! I wanted to build one that would be simple, lightweight, and not require modification of the trailer. Being able to quickly stow and deploy the new wagon is a requirement. To get the Radio Flyer into our plane requires either removing the third row of seating or removing the wagon's front wheels. Squeezing our Burley Cub in there with two full-size bicycles always requires removal of seats. It will be a big help to be able to put the trailer (and folding bicycles?) in the baggage compartment easily and take off for some adventure. (Yes, dog is my copilot...)

The square receivers make an easy place to connect conversion fixtures. (For my first attempt, I used one inch square tube which was very tight. I now have 25mm tube but I was only able to find it with 1mm rounded corners. The squarish corners blocked insertion but some hand filing made it slip. I plan to use a 1/16" round over router bit to round the corners a bit more.) I inserted pieces of rounded corner square aluminum tubing into these receivers and drilled holes for the lynch pins and for the front tube. One-inch nylon webbing is also screwed to the sides of these tubes to act as the tug lines. I've been tempted to use a single tree, but I haven't seen a need for it so I went without again for this project.

The 0.625" OD 0.058" thick aluminum front tube is captured between these two square tubes. It serves as the pivot for the poles. The poles are the same 0.625" OD 0.058" tubing, TIG welded to make a 'T' with a short piece of 0.750" OD 0.058" tubing. The poles slip over the front tube and are secured to the front tube with cotter pins. These pins keep the poles at the desired width and cause the poles to rotate together.

At first I tried leaving the poles straight. They were usable but I decided to bend them enough to rise to be nearly horizontal along the length of the dog. This was done to keep the poles away from the dog's hind legs and so that the tips would not extend up toward the dog's face. The bending has an added benefit; it allows the poles to swing out of the way under the trailer so that it can be readily used as a pushed stroller without removing the poles. This will be handy when we're traveling to/through heavily-congested areas. (Ah! There's yet another benefit of the poles being bent to be higher at the back of the dog. Grazie learned from Garbo to lift her leg to pee. She can barely get her leg over the pole of wagon 00 but the poles on this wagon appear to be too high now. That should keep the tug lines a little cleaner.)

In order to keep the poles in this position under the trailer, I took advantage of some excess length on two bolts holding the wheel mounts. I pushed tee nuts through a rubber strap and then threaded them onto the bolts. This strap can be pulled over the poles to secure them under the trailer. I plan to put rounded tips on the poles so that they won't dig into the underside of the trailer (or my leg...).

The push handle (part of the full stroller kit) slips easily into the round receiver tubes behind and above the trailer and locks in place with snap buttons. Even with a dog pulling, the push handle is a useful addition. Running into the padded handle when Grazie abruptly stops to sniff something is much more pleasant than tripping into the wagon. It will also be easier to assist Grazie up hills and through deep snow by pushing on the handle instead of the sides of the wagon. I've already used it to guide her in heavy traffic areas. Having a wagon configuration instead of a cart is a benefit here. The vertical forces from the handle are not transfered to the dog. Grazie often pulls hard enough to lift the front of the wagon when I'm pulling on the handle but because the poles rotate, there's no significant vertical force on her.

The brakes on the poles are simply pipe clamps with clear tubing covering the screw. My bare legs have suffered from being pegged by the bare clamps that I use on my other wagon (Grazie likes to walk right beside me.) so I decided that I needed some protection. The tubing works well.

Although this wagon is considerably wider than the Radio Flyer, Grazie was able to pull it immediately without any problems. (On our second walk, she crossed the street, went around a parked car, pulled into the driveway just ahead of the car, and returned to the sidewalk, dodging two large trash bins in the way. I held my breath but the wagon missed everything.) It makes much less noise than the wagon and it seems to pull easily, even with a load.

planned enhancements

The tips definitely need to be covered to protect bare legs. I have some expansion (well) nuts for this (as I did on the first wagon) but I'm also considering using some "aluminum putty" to fill the tips.

The 8-inch castering wheels seem a little small. Resting on those wheels, the trailer seems to tip forward. I'd like to install 10-inch casters to raise the front and to assist in traveling over larger obstacles.

I strapped a strobe light to the Radio Flyer for use on our evening walks. It's a big help, especially at night when Grazie is a hundred yards up the road/trail on the other side of some brush. There's a built-in flag holder on the Transit but I plan to take advantage of the extra height of the structure to add highly-visible flashing LED lights.


On Friday, 2004-05-29, while waiting for some files to move in order to clear some /tmp space, I noticed a couple hits to this page with as the referrer. In quick order I thought "Why the heck would Slashdot readers look at this?" and then "Oh, crap!" I've been meaning to move more of my personal files from my server at Wintek in Lafayette, IN to the one I have with in Chicago, but I'd run into problems and delayed it. No more! There are high fees for bandwidth usage at Wintek and the FDCservers machine is unmetered. It was time to move quickly.

Because of a lack of disk space at Wintek it took me awhile to get my data exported. Then I quickly installed it in Chicago and configured redirections ( -> in time for the Slashdotting. Unfortunately I didn't configure caching of the Zope data in time and the HTTP server became very slow to respond due to all of the dynamic images. (It was interesting that the machine was still quite responsive for SSH sessions. Yea, 2.6.5!)

It's 1:30AM EST Saturday morning now and I have the caching established. (Remember "CacheEnable disk /"!) It seems to be much more responsive. Caching good.

Now to track down the "Anonymous Coward" who submitted this as a Slashdot story...after some sleep.

wagon 02

Wagon 01 has become part of an independent study course that I'm taking at Purdue to study dog-guided vehicles. The other part of that course is the creation of an electric-powered dog-guided vehicle.

I started with a Sunrise Medical Quickie G-424 electric wheelchair and added a RoboteQ AX2550 motor controller. This was a surprisingly easy conversion, pretty much plug and play after I had all of the right power connectors made.

For my initial testing, I used a Toughbook with 802.11b and a USB camera to drive the controller. I have replaced the Toughbook with a MiniITX system screwed to the back of the chair and powered by a 24V-12V DC-DC converter.

The goal of all of this is to create a wheelchair that can be guided by a service dog but powered by electricity. The chair will follow the dog (and also avoid some obstacles if I get other sensors working) without providing a significant load on the dog. I hope that this will show that it's possible to use smaller/older dogs to perform wheelchair assistance duties in a more efficient configuration. Some wheelchair users (those with limited vision/fine motor control, and those who use the same hand for controlling both the wheelchair and a "talker") need the assistance in guidance that a service dog provides, but normally this means choosing large dogs who can handle the large stresses that result from also pulling from the side of the wheelchair. In talking with wheelchair users who have service dogs, I've also found that having the dog pull from the side of the chair is often inconvenient (in crowds) and sometimes impossible (on narrow ramps).

The big challenge for the work I've outlined for this course will be sensing the position of the dog. I don't want to use rigid poles because they're too clumsy in a crowd. I'd like for the dog to be able to easily move from heeling beside the wheelchair (or even riding on it), to performing retrieval/delivery tasks away from it, to leading in front of it as the user's needs dictate. I also want the dog to be able to take sharp corners (such as on the switchback wheelchair ramp outside Lilly Hall) with the wheelchair tracking the path of the dog instead of simply homing on the dog. I've considered IR, RF, ultrasonic and mechanical sensors.

In order to just get something workable implemented, I'm leaning toward adding a rotary encoder and (optical?) deflection sensor to the smallest retractable lead I can find. The detection of the dog's position doesn't have to be precise at this point; I just want to get an idea of how this might work. Although it's not "high-tech," a tether will probably be required anyway and being retractable might be convenient. The tether could even extend the capabilities of the wheelchair by allowing the dog to provide assistance in climbing curbs that the chair alone might not handle. (I'm sure there are lots of complex considerations to this but my empty G-424 is stopped by the rounded curb in front of our house and I've seen Grazie pull heavy loads over the curb with ease.)

While I'm enjoying just exploring right now, I think about turning this into a Doctorate research project. I've talked about it with people in Vet. Tech and ABE, and I'm also thinking about ECE and BME. I'll be happy if I can simply demonstrate that it can do what I think it can, but I'll be thrilled if someone finds a use for it. The ultimate would be to also receive funding to work on the project. My wife and I are members of Delta Society as part of their Pet Partners program so I'll probably query their National Service Dog Center for some advice.

wagon 03

[I usually think of "wagon" meaning "four wheel vehicle" but I see that it's "a wheeled carriage," "a chariot," and " any of various kinds of wheeled vehicles drawn by a horse or tractor" so I'm going to continue to use the word to describe my first two-wheel dog-powered vehicle.]

A friend organized fundraising walks around the state and our church had a team. We wanted to carry our church banner with us on the walk. It sounded like a good task for our new dog, Morgan.

Morgan had experience pulling me at high speeds on my bike and scooters and recently I'd made a rubber sledge/travois for him to drag on slower family walks. He indicates a strong desire to pull; he practically leaps into his harness when I pull it out and he's always trying to get into position to pull the things I build. He stuck close to me the night I built this cart, always available for fitting and testing.

I only had a few hours to build this cart so I stuck with a very simple design using readily-available parts. Keeping it light was not a concern so I used galvanized steel pipe throughout. The cart is essentially an axle of 1/2" all-thread through 1/2" pipe fittings necked down to 3/8" pipe near the wheels. The 3/8" pipe needs to be reamed out with a 1/2" drill bit to allow the all-thread to fit through. The tee fittings connect to the two dog poles and the single banner pole. Normally there would be a set of traces for pulling but I used the dog poles for steering, braking and pulling. The braking and pulling was achieved through Allen-head screws that stuck out horizontally from the poles, capturing the D-ring of Morgan's multipurpose harness.

We took a quick jaunt around the neighborhood and the cart worked well that night. I didn't attach the pole with the banner until we were at the event. It was a hectic time (and we were running late) but Morgan did a fantastic job with it. It was a good job for him to have and it was a great way to publicize our group.

After the walk I decided to play with the cart a bit more. The all-thread axle was easy to use but I really wanted to be able to disconnect the wheels more easily. I swapped out the reducing coupling and short 3/8" section of pipe for a hex coupling and 2.5" section of 3/8" pipe. I bored out the pipe with a 33/64" bit and now it fits my quick release axles perfectly. For walks around the neighborhood I switched to a short vertical pipe with an end cap that captures some old weights. I also swapped the washers (rivet backs, really) on the brake screws with nylon spacers so that the D-ring is less likely to slip beyond the screws. I wrapped a length of nylon strapping around the frame and knotted the end so that I can easily step on it to stop the cart. This works remarkably well.


For wagon 00, I just used a simple conduit bender. Making complex curves and repeating them with this tool is difficult. In order to easily make good bends in the future, I ordered a Van Sant Model 3 tube bender. That was three weeks ago and it'll probably be another three weeks before the dies arrive.

The biggest challenge for wagon 01 was welding the poles. I decided to jump in to aluminum welding by buying a Lincoln Precision TIG 185 from Indiana Oxygen. (The Indianapolis store quoted a very low price for the package with the cart. I double-checked that it included the cart. Later I realized that we have a branch in Lafayette. I called them and asked if I could pick up the welder there. They checked, discovered that I had gotten the price without the cart, but still honored the quote, and were very helpful in loading it and getting me set up with accessories.) At first I was trying to not deform the 3/4" tube at all as I welded so that it would still slip on the 5/8" tube. I found that I could build a weld on the surface without pushing through the tube, but anytime I got a nice puddle developed, it would make a dimple into the tube. Finally I bought a 41/64" drill bit and solved that problem. Now I can think about getting good weld penetration and stop obsessing over not deforming the tube.

In making the poles, I used an Ol' Joint Jigger to cut the ends to fit nicely. It's a great tool but mine seems to be off center a bit. I found that a very similar-looking tool is available at Harbor Freight for only $50. I used my 1/2" Dewalt 18V hammer drill to make these cuts but I've since purchased a floor drill press.

I also recently bought a cheap digital caliper. It confirms that the square tube used for the bicycle attachment is smaller than one inch. I now have 20 feet of tube with 1mm round corners so I plan to make it available to others who would like to tackle such a project.

I purchased a 30" sheet metal brake to form an aluminum plate so that I can mount the motor controller in the back of wagon 02's base.

owned by: kyler


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