Posted On: January 27, 2016 by National Seating & Mobility in: Lightweight Wheelchairs Manual Wheelchairs Wheelchair Adjustment wheelchair adjustments
Centre of Gravity (COG)
COG is likely the most effective adjustment you can make to maximize wheelchair performance. The centre of gravity of a wheelchair is the point at which the weight of the wheelchair is balanced. A wheelchair will need an adjustable axle plate in order to adjust the COG.
Some factors affected by centre of gravity are:
- Wheelchair stability.
- Ability to do a wheelie.
- Ease of propulsion.
- Ease of wheel access.
- Posture.
Centre of gravity is adjusted by moving the rear wheels forward or backward.
By moving the wheels back you're moving the COG forward. This makes the chair more stable but also puts more weight on the front casters. This can make the wheelchair harder to propel and turn. If the COG is too far forward there is a risk of a shoulder injury or strain from the increased effort it can take to propel the chair.
To move the COG backward, the rear wheels need to be moved forward. This takes the weight off of the front casters, which makes the wheelchair easier to propel and turn. This also causes the chair to be more tippy (more likely to tip over backward, especially without anti-tippers).
Tippy is good if you want to do wheelies, but much caution is required when wheeling up hills and ramps. This particular type of COG setting would only be recommended for experienced active wheelchair users. However, a slightly more forward centre of gravity can also be helpful for seniors or facility clients to make their propulsion easier.
Keep in mind:
- A wheelchair's centre of gravity will change if someone is sitting in a chair (as opposed to an unoccupied chair).
- A general starting point for COG adjustment is 80% of weight over the rear wheels and 20% over the front casters. From there very small adjustments can be made to optimize for that particular user.
- For the most effective propulsion, the rear wheel should line up with the shoulder, or just in front of the shoulder.
- There are many things that will affect how to adjust the COG. The user's height, weight, strength and position will all play a part, as will the type of wheelchair and seating.
- Sometimes multiple adjustments over multiple days are necessary to get the COG perfectly set up for a particular user.
Check out our website for a wide selection of lightweight manual wheelchairs. Contact us with any questions about centre of gravity, or any other questions you might have.
0 comments