Welcome to the world of power wheelchair bases, where you have three options to choose from: front-wheel drive (FWD), mid-wheel drive (MWD), and rear-wheel drive (RWD). In our previous blog posts, we delved into the advantages and considerations of FWD and MWD. Now, let's take a deep dive into the realm of RWD and uncover its unique benefits and considerations.
Rear-Wheel Drive
Rear-wheel drive was the first type of power wheelchair base configuration manufactured. It is still used today but is more rarely utilized than front or mid-wheel drive. The drive wheels are in the back of the chair and the casters are in the front. The following pros and cons should be considered when thinking about RWD configuration. Remember, these are general concepts and apply differently to each individual chair model. Depending on the chair model, the size of the casters used will affect both indoor and outdoor driving, and lower extremity positioning, and potentially impact the client’s ability to transfer safely.
Benefits of Rear-Wheel Drive
- Typically, RWD power bases offer good suspension, minimizing vibration in the chair and softening the ride for the client.
- Four wheels on the ground minimize the energy and forces that are distributed through the chair.
- RWD bases provide good tracking for successful use at higher speeds.
- The configuration may feel intuitive to clients since the client can see where their feet are going and doesn't need to worry about how the back of the chair is turning.
Considerations of Rear-Wheel Drive
- The front casters on a RWD power wheelchair move first during turning tasks. This may compromise maneuverability in tight spaces and during turning tasks.
- These rotating front casters must be straightforward to negotiate obstacles and turning into an obstacle may be challenging.
- As the rear wheels are connected to the drive motors, the casters are being pushed over obstacles and through various terrains in a more effective way than other configurations where the casters are being pushed. When casters are being pushed, the force generated is forward and downward, which can increase the likelihood of becoming stuck in certain situations.
- The area for proper weight distribution and balance in a RWD wheelchair is small. As most of the weight is in the back, it can be difficult to position the client properly while maintaining stability and balance in the base, often requiring rear anti-tipper wheels.
- As the weight is more rearward, the client may have limited access to larger angles of tilt and/or recline, which shift the client’s weight posteriorly.
- Rotating front casters may limit lower extremity positioning options. Revolving front casters could collide with optimally positioned footrests. If this happens, adjustments may be required to compensate for this, such as raising the seat to floor height, or positioning the client more forward on the base (using caution not to impact balance and stability).
- Front caster placement may potentially interfere with stand-pivot transfers by limiting how close the chair can get to the transfer destination or interfering with foot placement during the transfer
Amy Morgan, PT, ATP
Director Product Management ‑ Power Wheelchairs
Amy has been involved in complex rehabilitation technology since beginning her career as a physical therapist in 2000. Amy’s clinical experience primarily includes outpatient and inpatient pediatric care at Cincinnati Children’s Hospital where she worked with a variety of patient populations. Additionally, Amy was the lead therapist in the Wheelchair/Seating Clinic and Comprehensive Neuromuscular Care Center. In 2007, she joined Permobil as the Pediatric and Standing Clinical Specialist/National Clinical Education Manager where she presented lectures both nationally and internationally and provided input to design for new products. Amy has also worked in Sales at Permobil as the Territory Sales Manager for central/southern Ohio where she earned top sales awards multiple years. She is now part of the Marketing organization as the Director of Product Management for Permobil’s power mobility product line.
Faith Saftler Savage, PT, ATPSeating Specialist and Consultant
The Boston Home
Faith has over 40 years of experience as a physical therapist, seating specialist and rehabilitation technology supplier, treating persons of all ages with a variety of disabilities. She has been working as a seating consultant at The Boston Home for 30 years assisting residents with MS and other chronic disabilities in obtaining appropriate manual and power wheelchair systems to improve posture, comfort, function and independence in mobility. She runs an outpatient clinic at The Boston Home and assists people in the community with diagnoses including SCI, MD, CP and MS to obtain appropriate equipment.
She has published chapters in journals and books including; International Journal of MS Care, Fundamentals in Assistive Technology and Physical Rehabilitation. Speaking topics include seating assessment, power mobility and alternative positioning. Faith received her BS in Physical Therapy from Ithaca College in New York.