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Danger: TiLite ZR2 front wheel assembly flutters and locks up

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    #16
    FWIW Wikipedia says that racing wheelchairs can exceed 30 kph (about 20 mph), and they use large-diameter front wheels.
    Chas
    TiLite TR3
    Dual-Axle TR3 with RioMobility DragonFly
    I am a person with mild/moderate hexaparesis (impaired movement in 4 limbs, head, & torso) caused by RRMS w/TM C7&T7 incomplete.

    "I know you think you understand what you thought I said, but what I don't think you realize is that what you heard is not what I meant."
    <
    UNKNOWN AUTHOR>

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      #17
      Originally posted by SCI_OTR View Post
      Rarely will a manual wheelchair attain anything close to 15 MPH unless it is rolling downhill.

      I use 4 x 1.5 FrogLegs Aluminum Hub soft roll casters on regular bearing forks and have never experienced caster flutter. I can let my chair coast freely down the full length of a parking garage ramp and experience no flutter at all when I reach the bottom. I don't know what my terminal velocity is, but it takes me 100-150 feet to stop.

      Now that I think about it, I don't remember seeing caster flutter on any TiLite rigid frame.

      My guess is that the source of your problem is the very basic 4x.75" plastic wheel/poly tire. A narrow, low end, caster made out of a relatively soft material on a fork that can accommodate casters that are up to twice the width. Bearings that are seated in a soft plastic hub will not have the same precise alignment as bearings seated in an aluminum hub because. Not only are the tolerances much looser because of the soft hub the caster axle is relatively wide.

      The only other thing I can think of would be a floating caster because of uneven tension in the footrest.
      Thanks. Good input. I can see how an uneven footrest could be bending the frame. But it would have to be way off. Otherwise having to get the footrest perfectly level means that the chair is not manufactured well enough to accommodate tolerances.

      Changing the wheels is a more realistic solution. But then why didn't TiLite recommend that?

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        #18
        I have to say that I did not clock the speed to be 15 mph. I am guessing that is the speed that my dog pulls me because she goes at the speed of a sprint. I also repeated the test with someone pushing me and they weren't sprinting. They were jogging. I think a human jogs at far less than 15 mph, maybe closer to 10 mph. Whatever that number is I know that my expectation is reasonable and TiLite did not disagree. I should add that the chair vibrates at any speed greater than walking speed (3 mph).

        I wonder if moving the the rear axle forward would remove enough force on the front casters to stop the flutter.
        Last edited by Axle; 20 Jan 2013, 8:42 PM.

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          #19
          When you put it that way...running speed, maybe so. Curiosity here...how do you brake at high speed? Do you have hub brakes that actually brake for you?. Downhills I tend to slow myself down as I go down... I have to admit I am kind of a chicken, and new to the active chair user thing. I'm amazed to find out chairs can go 40mph....that's friggin incredible!!
          Tourette's Syndrome - motor tics of the legs, feet and back, which can make it difficult or impossible to walk

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            #20
            Wobble seems to be a continuing problem. I'll offer up my opinion.

            My folding chair casters wobbled with 5 inch composites. I switched back to the aluminum hubs with 7" wheels and have not had a problem since. So I'm inclined to believe it has more to do with perfect bearing alignment than other factors. You can tighten the wheels on the axles and think all is well, but what I notice is that the bolt that is used for an axle is a sloppy fit. It's too small of a diameter. The spacer helps, but it is not perfect, the bearings need to be seated. So if the two bearings are not exactly parallel, you never know it until the wheel wobbles.
            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.

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              #21
              Good point nonoise. I have not looked very closely to manufacturing issues. I am giving credit to TiLite to do their homework. Otherwise if it means that I have to re-engineer the wheelchair, I don't want the wheelchair. This is not a $500 wheelchair. This is a $5K wheelchair.

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                #22
                Originally posted by Axle View Post
                Changing the wheels is a more realistic solution. But then why didn't TiLite recommend that?
                I'm sure the vast, vast, majority of calls they get are from people who have caster flutter because they mistakenly adjusted their forks to have absolutely no resistance when they swivel.

                Your situation represents a less likely scenario. Having a service dog pulling you along at a decent clip with that type of caster would generate a lot of internal resistance since the chair is also more front loaded. For that model of chair and your kind of use, that caster is like permanently using the "spacesaver" spare tire on an automobile!

                I would think that would be something they might look at if tightening the forks didn't work (especially if they knew that a poll would be posted on CareCure if their first suggestion didn't work!).

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                  #23
                  Never looked at it that way SCI OTR. This chair costs over $5K and I paid over $1.6K out of pocket. To get back to your analogy, that would be like buying a BMW and having to re-engineer it. I expect a high performance wheelchair to be able to travel downhill safely without modifications.

                  My dog pulling me at a jog is no faster than traveling downhill. I expect a stock TiLite ZR2 wheelchair to be able to do that. Otherwise they have no business delivering it in that condition. It's a liability if nothing else. I have already fallen out once.

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                    #24
                    Originally posted by Axle View Post
                    My Quickie, which is 8 years old goes over 30 mph before it vibrates and give me lots of warning to slow down.
                    30mph really!! Isn't that a bit too much, I have a dog to and top speed I go is about 10mph on my old quickie with 5,15" casters before they stat warning to slow down lolol. I believe that maybe just maybe you can go 15mph, 20mph top but it's just my opinion.

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                      #25
                      On average, humans walk at 3, jog at 6, run at 15, and sprint at 20 mph. If you had to keep up to my dog pulling me you would be running not jogging.

                      I have gone over 40 mph in my Top End racing chair. I know what speed is what.

                      Regardless of the exact number, the point is that I am able to have my dog pull me as fast as I/she wants to in my Quickie which is 8 years old. I can't even go faster than walking speed in my TiLite before I feel unsafe.
                      Last edited by Axle; 20 Jan 2013, 10:36 PM.

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                        #26
                        Thank you all for your responses. That is why I am here. I don't want to discourage anyone from responding. But I have to say that this post is not about determining top speed of a wheelchair. It is about safety.

                        Put all numbers aside and ask yourself this question. Should a wheelchair be able travel on a flat surface at a nominal speed of a human running?

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                          #27
                          What kind of dog, Greyhound?

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                            #28
                            Alex, call my husband Mike Box 951-531-3383, he will help you out and you are close enough to us to come over and he will fix it for you.
                            Alison

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                              #29
                              My Tilite TR has never had castor flutter and I live in San Francisco. I've stupidly taken it at the highest speeds it would go and still nothing but smooth. Since I caught a castor going 4mph a month ago going at an angle up a driveway from the street, I've been shy about going fast. I took a pretty good spill. With my Tilite I am not worried at all that I'll get wobble but it is made of earthly materials and I am worried that I'll be flying downhill at speed and have a castor tire chunk-out and then I go flying. Tilite is the best chair I've ever owned. Perfect from the day I got it and perfect everyday since. I don't have SCI_OTR's experience but I am wondering if you have a floating castor too. Good luck :-)

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                                #30
                                Yeah, I think for high end wheelchairs one would hope so. Heck, one would hope to be able to go even faster for what these chairs cost. But at the same time, remember...manufacturers are still covering their asses and worried about FDA approval and liability. The user manuals talk about the inherent danger of removing antippers, scorn the perils of doing wheelies and how nobody should ever do curbs without 2 attendants..... Yeah. I think that about sums up what wheelchair manufacturers are thinking with regard to mobility, for the most part, anyways. Hopefully Ti, Top End, and others like them are the exceptions.
                                Tourette's Syndrome - motor tics of the legs, feet and back, which can make it difficult or impossible to walk

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