by ex-Gooserider » 05 Feb 2019, 04:28
For the same volume of metal, aluminum is lighter... However it is weaker. Therefore unless you do a lot of engineering design work to optimize construction, you lose some of the weight reduction in order to recover strength....
Aluminum is also harder to weld and do some fabrication operations on, compared with the cost of steel...
Titanium is lighter for comparable strength, but even more expensive and difficult to work with.
In a manual chair, the frame is one of the largest pieces that contributes to the weight of the chair, so there are big advantages to taking advantage of the weight savings of titanium or aluminum (and even more recently carbon fiber) to shave every ounce off the frame as this gives a big %age weight reduction.....
So the traditional steel "E&J" transport chair can weigh on the order of 50-60lbs (~25kg) and doing light weight engineering to make the frame out of aluminum or titanium cuts that down to around 20-25lbs (~10kg) it is WELL worth the costs and effort for the better than 50% reduction in weight...
In a power chair, the frame is only a small part of the total, with the motors and batteries weighing far more... My chair weighs around 250lbs - very roughly....
100lbs of lead bricks
60 lbs of motors (guessing - I've never actually weighed them)
60 lbs of seat and other stuff including wheels, electronics, etc.
30 lbs of frame....
250lbs total....
Going to lithium chops the battery to 50lbs
can't do much about the motors... Some of the other stuff is electronics and so on, so can't do as much with that as might be possible with the frame...
So figure I redesign for light weight and cut 50% off the frame and 20% off the seating etc... I end up with
50 lbs of batteries
60 lbs of motors
40 lbs of seating and other stuff
15 lbs of frame
165lbs total...
That's a nice weight reduction, but nothing like what you get with a manual chair - so it's a lot harder to justify the effort...
ex-Gooserider
T-5, ASIA-B
Jazzy 1100
Jazzy Select 6
Quickie Q-7
Invacare Mariner
Want to make / get a better chair, ideally one that stands.