1. Durability, value, and reliability of selected electric powered wheelchairs1 
Megan V Fass, MS, Rory A Cooper, PhD, Shirley G Fitzgerald, PhD, Mark Schmeler, MS, OTR/L, ATP, Michael L Boninger, MD, S.David Algood, BS, William A Ammer, BS, Andrew J Rentschler, MS, John Duncan, BS 
Archives of Physical Medicine and Rehabilitation 
Volume 85, Issue 5, Pages (May 2004)
DOI: /j.apmr

2. Fig 1
The 2-drum (left) and curb-drop (right) machines. The 2-drum machine has 2 rollers with slats attached, which are designed to simulate driving over terrain. The curb-drop machine lifts and drops the EPW using 4 chains, which is designed to simulate driving down curbs.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /j.apmr )

3. Fig 2
(A) Durability. The total number of equivalent cycles completed until first failure and until no longer operable. (B) Value. Value takes into account both the durability and the retail price of the wheelchairs, so a higher value is more desirable because it indicates that the wheelchair lasted longer for its price. (C) Reliability, in terms of mean equivalent cycles between consumer repairs, supplier repairs, consumer failures, and supplier failures. A higher number is more desirable, because it indicates that the wheelchair completed more equivalent cycles for the given number of repairs or failures. (D) Reliability, in terms of mean equivalent cycles between repairs, failures, consumer repairs and failures, and supplier repairs and failures.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /j.apmr )

4. Fig 3
Accumulation of consumer and supplier failures. Note that the data point at 4,400,110 equivalent cycles (for the Arrow) is not actually a failure, because the wheelchair was still operable. Reprinted from Fitzgerald et al17 with permission from the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /j.apmr )

5. Fig 4
Survival curves during the first 400,000 equivalent cycles using manual wheelchairs from earlier study.17 A step in the curve indicates a first failure occurrence.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /j.apmr )