Maybe Patrick Madsen does not have front or rear casters.Originally Posted by SCI_OTR
Maybe Patrick Madsen does not have front or rear casters.
I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.
It's more like the front end of the ZX dips down, making the arms drop low.
I've got the front caster on the ZX, Nonoise, it's that it dips. I'm sure it wouldn't tip or anything, just weird if a person is holding onto the arm fo the ZX and it all of a sudden drops way low. I think that's the point of the anti tips on the ZX; to keep the arms from dipping low when going down a ramp etc. They're not to stop a person from tipping over backwards but rather flippin the machine forward too much, causing the arm dip.
I think they may have replaced elastomers with metal tubing because the big anti tip wheel does come very close to motors when the caster swivels. If there was a flexing elastomer there, then under load it might flex enough to strike the motors.About what Pat wrote:
Did they replace it on both the front and rear forks with aluminium, or only the rear fork? Does anyone know their rationale for doing this? Maybe Pat can chime in.
When I look at the ZX-1 Photos on the Spinergy FaceBook site, some photo's (as well as the Operators Manual Z100080 Rev 4) show the elastomers on for both front and rear fork:
Another photo on the Spinergy FaceBook site shows that at least in the rear, the elastomers is off.
I would like to know if the elastomers can be reinstalled too. You can order Frog Legs polymers (a.k.a. elastomers, suspension springs) from Frog Legs and others.
Unless Pat or others say there is a good reason for not using the polymers, I'm going to see if I can get them from Sportaid to ship with the ZX-1 that is coming soon. We are looking for as much suspension as we can get, as our roads are really rough here (cobblestones, bricks, etc.).
Actually, that would be consistent with my question. On the original design, any forces caused by the change in momentum act directly on the powerbase itself. Angular displacement of the powerbase would cause the arms to drop down. Those forces need to go somewhere, and it looks like the Anti-Tilt Assembly transmits those forces onto the backrest of the wheelchair.
If the backrest could fold, angular displacement about the hinge would cause the backrest to fold. Since the backrest on an occupied wheelchair will not fold, those forces act on the entire chair--mostly at the front casters.
Couldn't you accomplish the same thing as the Anti-Tilt Assembly by clamping some sort of stop onto the tubular armrests that came into contact with the backrest? Or possibly a strap?
If in fact the pressure of the anti tipper bars against the rigid back is being transferred to the front casters and further loading them, then I wonder if use of the Freewheel (which works great on ZX-1 without any adjustments) with the ZX-1 would increase the range?
We are calling our ZX-1 the Mars Rover.
On the other hand, if those forces are shifted onto the backrest, and subsequently to the entire chair, the FreeWheel would add more stress to the footrest than it already does.
Fortunately, deceleration would tend to be more gradual with the FreeWheel and you wouldn't use in on a van ramp. Situations where the powerbase would tilt forward should be rare.
These are the types of issues that the vast majority of people haven't thought of until now.
On one of the RESNA tests where a 250lb user travels down a 6 degree ramp at full speed and turns suddenly and reverses direction 180 degrees and travels uphill, if the rear wheels of the manual wheelchair are too high during this maneuver, the chair could tip over sideways. When trying to find a solution it was observed that the rear Frogleg fork deflected and possibly added to the problem. The real solution came by adding a proximity switch that reduced the speed to 40% when the manual wheelchair's rear wheels are lifted too high by the ZX1. It's important to keep your rear wheels as low as possible at all times, even slightly scrubbing the ground. They act as a sort of training wheel or outrigger. The ZX1 is allowed to raise the manual wheels higher for when encountering obstacles like thresholds where the rear manual wheels may interfere with traction to the drive wheels. After manuevering past the obstacle you should lower the rear of the manual chair to the safe driving position.
To be clear I don't work for or represent Spinergy and they must make the final decision on what they think is necessary to put out as a product that they feel is safe in every possible use. I can only give my advice.
Having said that, in my opinion it is a non issue and a polymer could be used. I have them on all of my ZX1s and they are on the others that I originally built and sold with no problem that I'm aware of. I would though recommend getting their stiffest polymer. Under normal use the difference will be negligible because most of your weight is transferred directly to the drive wheels.
Last edited by pattherat; 06-11-2013 at 02:00 PM.
Back to the topic, Spinergy called me today and they offered to ship me a new anti tip something - I was half asleep so I can't remember what it was. They offered me a overnight shipping which was very impressive but I told them that Monday is fine Since I don't want the UPS guy waking me up in the morningThey shipped it ground to save a buck... and I'm not sure if they sent the right part we'll see on Thursday
I just found out that They shipped a rear frog legs setup
Last edited by Mac85; 06-11-2013 at 02:30 PM.
C5/C6 Complete since 08/22/09
That's right, but most of this is caused by the user leaning forward and putting his weight on the armrests which is natural but if you can avoid doing this then only suddenly stopping mid ramp would cause the ZX1 to rotate forward. It takes practice but I have no fear going down a steep ramp with no anti-tilts. It's not reasonable to expect every user to master this before using the ZX1 so hence the anti-tilt mechanisms that prevent this. Also if you have your armrest brackets setup correctly for your chair's COG, and no anti-tilts, the armrests can only dip down a few inches which is disconcerting but shouldn't throw you out of your chair.
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