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There are a number of detachable trike wheels available to purchase for active wheelchairs. These devices typically cost about $600 or more. They also typically have a large trike wheel that protrudes well beyond the front of the wheelchair. As a result, I find them to have numerous disadvantages in crowded urban landscapes, elevators, and bathrooms, as well as being expensive.
My goal was to create a prototype for cheap and easy to construct detachable trike wheel that was as small and light as possible, while improving my ability to deal with rough streets, cobble stones, sidewalks, cracks, potholes, grass, and gravel pathways. And also provide me with increased ability to carry luggage/duffle bags on city sidewalks when traveling. With the criteria that it doesn't hinder my ability to open doors, jump curbs, and maneuver in tight spaces and among thongs of pedestrians by creating a trip hazard.
The design is a simplification of my original DIY Nature Trike Wheel which uses a 6.5” x 2” pneumatic caster wheel ($22). While this pneumatic caster wheel works great on nature trails, it tends to flutter on smooth surfaces. Therefore, the Urban Wheel uses a 5” x 1.5” solid wheel caster from Home Depot ($25) which does not flutter on pavement even at high speeds. This is the same caster that I use for “running” road races which includes marathons.
Generally speaking, many active manual wheelchairs’ performance are limited by their front casters. Caster performance is a tradeoff. Small diameter casters work well on smooth surfaces and don’t interfere with the footplate, but they tend to get stuck on uneven surfaces. Large diameter casters tend to flutter and interfere with the footplate placement but are better for rolling over obstacles.
If the frame of the wheelchair gets slightly out of alignment, one caster tends to float in the air while the other takes all the weight. This results in erratic caster movement and jerkiness. If the casters are not well maintained, loose, or have defective bearings, they will tend to flutter. The end result is a wheelchair that is annoying and difficult to propel.
A trike wheel solves the above problems. The larger diameter wheel which sits in front of the footplate rolls over obstacles and increases the forward stability of the wheelchair by lengthening the wheelbase. The wheelchair is less likely to tip over forward when the caster encounters an obstruction such as a pavement crack or pothole. A trike also is able to track straight on a beveled surface better than dual front casters making it easier to push on side slopes.
For these reasons, racing (pushrim) wheelchairs and many rough terrain wheelchairs are trikes with a large front wheel and long front end. The tradeoff is that this configuration is not maneuverable indoors and in tight or crowded quarters. Therefore, the Urban Wheel uses the smallest diameter front caster wheel, as close to the footplate as possible, while still improving wheelchair performance by creating a trike configuration.
Since the Urban Wheel will raise the front end of the wheelchair, the wheelchair’s geometry and center of mass will change making it more rearward tippy. For extended use such as a road race, I suggest temporarily switching your rear wheels from the typical 25” (559) to 26” (590). The larger diameter rear wheels will counter the effect of the raised front end. You could also place a small wedge pad behind your back, or you can just deal with it.
The Urban Wheel is easily installed and removed. It weighs about 2 lbs and is compact. Therefore, it can be used as desired and removed then carried/stored when not wanted.
I designed the Urban Wheel to be compatible with my Tilite TR footplate. The basic design can be used on other solid footplates, but some modifications may be needed. The height of your footplate off the ground will also affect the height of the front wheel corner bracket. My footplate is 2.25” off the ground. A footplate that is higher off the ground will require an additional caster support block to compensate. I am using scrap pieces of 1" punched Zinc square tube as the support blocks. The top support block should extend all the way to the right angle in order to prevent the metal angle from bending (becoming more acute).
The Urban Wheel is secured to the footplate by the T that is created by the 1" Aluminum Angle Iron and the Corner Bracket #2. The Velcro straps hold the Corner Bracket #2 down to the footplate while also securing the ends of the Aluminum Angle Iron to the tube of the footplate.
As seen in the video below, I can install the Urban Wheel from my wheelchair in about 60 seconds. Another way to install the Urban Wheel is while not in the wheelchair and then transferring back in. You can also place your front casters on a block to raise the front end (same as a wheelie) while in the wheelchair.
Video of installing the Urban Wheel.
Watch multiple stress tests of the Urban Wheel on YouTube.
Note. The steel corner brackets I am using provide springiness which creates suspension. It is likely that a heavier person than me (140 lbs) may need a stronger corner bracket or some other type of reinforcement.
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Disclaimer - The material in this post is provided for informational purposes only. Use the ideas and suggestions at your own risk.