Mike wrote on 01/24/07 09:11:
I found out about the 4QD site which has a number of handy online
calculators. I found out that if I wanted to climb a 60% slope at one
mph with a chair + me + trailer + load totalling 1,000 pounds, I could
expect to draw 30-35 amps at 48 volts with appropriate gearing, not
counting inefficiencies.
Jeff,
I some how missed some of your posts so I went back and scanned them but
I guess I'm still not sure what it is you want to do. You want to
build your own Super Chair that can tow a trailer? Is that right?
Mike
Actually, I already have one that’s commercially made.
It's an Omegatrac made by TEFTEC.
You can see several examples at:
http://www.teftec.com/
One of the factory options is a pin hitch for a trailer. It's rated to
handle a 1,000 pound trailer on gentle slopes with appropriate gearing.
Different gearing on the chair constitutes just one toothed belt and two
toothed pulleys swapped out, which I think is supposed to take less than
a half hour at most. For that load, it has to be geared for somewhere
between 2.5 and 3 mph. Of course to handle that kind of load, you would
have to go with the heavy-duty suspension, either the dually or the wide
front wheels, and a heavy duty anti-sway bar. This kind of technology or
features is simply not available in any other manufactur's wheelchair,
unfortunately.
Power is supplied by 2 Group 24 gel cell batteries, and I believe the
controller that feeds the traction motor is rated at 120 amps, which is
more than any other chair I've ever heard of. Cheap chairs often use 50
amp controllers. Slightly better ones use 70 amp controllers, and what
are considered top-performing chairs go as high as 100 amps. I don't
believe any of these are continuous ratings -- they are probably for 2
minutes at a time or so.
The disadvantage of all this is a fixed top speed governed by your
gearing. A TEFTEC is the only kind I've heard of in recent years where
this can be changed, but it's not exactly convenient to change back and
forth. That's why I want the gearshift -- there are times I need a lot
of torque, and others where I need more speed than anything.
Also, with the recent cuts in Medicare and Medicaid, no one will pay for
a TEFTEC anymore, unless you weigh more than 400 pounds.
So... my only choice is basically to try to build my own, if I can
manage it.
jeff
