Friday, June 3, 2022
In my last discussion we looked at how suspension impacts the ride comfort and stability of Power Wheel Chairs (PWCs), and the functional impact this can have on your client. Similarly, we need to start to consider the power of the PWC in a functional manner.
More power does not always mean better, and with great power comes great responsibility; this is also true when prescribing PWCs. Over the last decade, when learning about motors, we would often discuss PWCs having a two or four pole motor. Functionally however, poles do not really have an impact on your client. I would encourage you to instead to think about motors as how much power (or watts) they have. Considering how much power a motor has is functionally important for your client, as greater power means that the PWC will tolerate more work, and harder work for longer.
What does this actually mean? As I am most familiar with Permobil chairs I will use the 3 Series which has a 300W motor and compare this to the 5 Series which has a 500W motor. The 500W motors are more clinically appropriate for clients who are navigating the outdoors on a regular basis, need to climb or navigate a hilly environment. The 500W motors will also work harder for longer. They will be a little more forgiving for those clients who push and drive the PWCs to the limits.
More power, also means more torque. Torque is the rotational force which is created by the gear box and turns the wheels. A motor with increased torque is going to contribute towards a smoother ride and an increased ease of climbing obstacles at a slower speed. This will have a positive impact on the client as they are able to access more difficult terrains, and they will also experience less movement in their seated position when going over obstacles. This is important to consider for your clients who may need to mobilise with alternative controls, requiring them to maintain the same position. For some, millimeters matter to maximise function. For these clients, this is where I would consider prescribing a PWC with a larger motor over a smaller wattage motor.
Having said this, a 300W motor provides ample power and torque for clients to navigate within their home and urban environments on a day-to-day basis. A 300W (or similar) motor and associated torque provides ample power to navigate footpaths, gutters, thresholds, and urban environments. For the majority of clients we work with who live in these environments, I would personally start with a PWC that has a motor of around 300W. If you then find that this size motor is not allowing for independent mobility or access, does not provide adequate climbing or the client is having difficulty managing terrains at low seed – I would then look at a PWC with a larger motor. Using this line of clinical reasoning will assist greatly when justifying the proposed PWC for your client.
Don’t forget, that programming torque and acceleration can also be done with most PWCs. Changing the % of torque in different settings can impact your client functionally in a variety of mobility related tasks. Ask your supplier to make changes during the trial and see what difference a change in torque or acceleration speed could make.
If you are prescribing a larger motor, don’t forget to check on the battery size. Larger motors will require larger batteries – typically Group 24 for motors of 500W. Not all batteries are created equally either – but I’ll leave that discussion for another day.
If you are not sure where to start when comparing chairs, please do not hesitate to reach out to one of the Clinical Services team members at email@example.com.
Tilly Brook graduated from the University of Adelaide in 2008 with a Bachelor of Health Science followed by a Masters of Occupational Therapy (Hons) in 2010 from the University of Sydney. Tilly worked within rehabilitation, working primarily with adults with a brain injury until 2015 when she moved to Singapore. In Singapore, she worked with children and adults at the Cerebral Palsy Alliance School (CPAS). In 2017 Tilly’s clinical knowledge continued as she worked with Mobility Solutions in Auckland, New Zealand. On her return to Australia, Tilly assisted in the development of the Clinical Hub Team at Sunrise Medical where her passion and experience for mentoring and educating therapists grew. Tilly Joined Permobil in January 2022 and is driven to grow therapists, enabling them to be the best therapist they can be.