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    Wheelchair Axle Diameter

    I have my original ZRa with stock wheels. I also have a set of Sun Fusion wheels I bought a few years ago. I don't recall being asked about my preferred axle diameter, but the new Sun wheels came with compatible 0.5 inch axles. Then just two months ago I bought a Permobil Helium manual standing chair. My expectation was that the wheels on it, Spinergy SPOX, would be interchangeable with the ZRa wheels. Unfortunately, the Spinergy wheels on the Helium chair have 12mm axles. Since the chair was made in France, it is not too surprising, in hindsight, that the axles are a metric size. It did surprise me, though, since I've never been asked about my preferred axle diameter during this or any prior order. So now I might be stuck with wheels that work fine on the chair they're with, but nothing else. The workaround seems to be to replace the Spinergy hubs with a 0.5 inch compatible version and find a machine shop to ream out the camber tube to 0.5 inch, a job complicated by the two degree camber. If I only wanted one-way interchange, I could probably make the 12mm axles fit the 0.5 inch hole in the ZRa camber tube by use of some 0.010 inch shim stock. But I really want them to go both ways.

    Any suggestions or how others have dealt with this?

    #2
    I think trying to retro fit your Spinergys to 0.5 compatible is going to cost as much as picking up a used set. Drilling out the camber tube the additional mm should not be an issue for someone with a shop with the correct equipment.
    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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      #3
      See if you can get new bearings to make the difference.

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        #4
        Originally posted by spinner View Post
        See if you can get new bearings to make the difference.
        Yes! Measure the OD & thickness of the bearings, then look for a match w/.5" ID.
        Whoops-now they won't fit the French chair anymore if that's a problem (bet it is)
        Then, machine the French axle out to .500".
        69yo male T12 complete since 1995
        NW NJ

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          #5
          Originally posted by pfcs49 View Post
          Yes! Measure the OD & thickness of the bearings, then look for a match w/.5" ID.
          Whoops-now they won't fit the French chair anymore if that's a problem (bet it is)
          Then, machine the French axle out to .500".
          Agree, if you can swap out the bearings to match 0.500" axles, you will skin this cat by just boring out the axle reciever. And it might just be as simple as using standard Spinergy US 1 1/8 x 3/8 x 1/2 bearings.
          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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            #6
            Still thinking about this!
            If the axle receivers are stainless, they will be a bitch to drill!
            69yo male T12 complete since 1995
            NW NJ

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              #7
              I'm in the exact same boat as you. My helium came with 12 mm axles, 28 mm OD on the radial bearings, on 24" wheels too. The sad part is, I also ordered set of 26" wheel at the same time hoping to use those instead but they have 0.5" axles. I'm using the 26" wheels on my tilite, which also had 26" wheels. I already looked into swapping out bearings from the hubs but nobody makes bearings with a 12 mm bore and 1.125" OD, in your case 0.5" bore and 28 mm OD, so don't bother looking. It's literally off by 0.5 mm (28 mm vs. 1.125"), which might as well be a mile. I'm taking the threaded tubes to a machine shop tomorrow to open them up to fit 0.5" axles and will probably scrap the 24", don't like 24" anyway. Btw, nowhere on the order form do they tell you the wheels will come with 12 mm axles. This is the first time I ran into this problem. One of many gripes I have with permobil.
              Last edited by lazierdog; 22 Sep 2015, 11:28 PM.

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                #8
                Bummer 1 1/8 inches = 28.575 mm. If those non conforming wheels are spinergies, keep the spokes.
                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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                  #9
                  @lazierdog: same problem here when we buy a TiLite ! We have to match with the .5" axles… and of course, all the chairs here manufactured in Europe use the metric dimensions, 12mm bore, 28mm OD. BUT there are resellers for special bearings that can do the job, 12mm bore and 28,5 OD, or the opposite 12,7mm bore and 28mm OD. I can give you the adress if you want.
                  C6-7 since mid 2002, no hand control nor triceps.
                  my website & my job (in France): Accessibility advisor www.acceslibre.eu
                  Also working on a French research about Peer counseling and Empowerment.

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                    #10
                    Lazierdog, thanks for the response. I guess misery loves company so it makes me feel a little better. And Robotnik, thanks for letting me know that the pain goes both ways. I would appreciate if you could pass on information about a supplier of bearings that mix inch on the bore and metric on the OD or vice versa. I suspect, however, that the long-term economics work out better by modifying or replacing the hubs and modifying the camber tube rather than committing to buying special bearings forever.
                    Since I have two sets of wheels that work perfectly well on the chairs for which they were intended, I may just accept the current situation and not try to work out a way to interchange. Life would be better if the US had just gone metric back in the 80's when we almost did.

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                      #11
                      Originally posted by robotnik View Post
                      I can give you the adress if you want.

                      Please do, that would be good info to know. I checked suppliers like fastenal and manufacturers like SKF without luck. I'll probably still open up the tube to accept a 0.5" axle since I know people who have the right equipment and are willing to do me a favor.

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                        #12
                        Originally posted by nonoise View Post
                        Bummer 1 1/8 inches = 28.575 mm. If those non conforming wheels are spinergies, keep the spokes.
                        The 24" wheels are the standard ones that comes with the chair, which is code for cheap, so the spokes aren't worth keeping. I've owned the helium for under two years and the spokes already shows signs of corrosion on them. I have wheels that are over 15 years old in better shape. I'll still keep the entire wheel assembled just in case someone around me is in desperate need of wheels that requires a 12 mm axle.

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                          #13
                          Originally posted by endo_aftermath View Post
                          Since I have two sets of wheels that work perfectly well on the chairs for which they were intended, I may just accept the current situation and not try to work out a way to interchange.
                          If they're high quality wheels that you like then that's the safest play. Btw, keep an eye on the helium's struts. Mine are practically worthless now. They give little assistance when going up. I'm looking to replace them but haven't heard back on the cost from my DME. I suspect it'll be an arm and a leg.

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                            #14
                            this guy sells these special bearings, but you can't find them in his catalogue, as they are for very specific use.
                            You can ask him anyway, and if you have a problem (explanations, or maybe shipping) feel free to ask me for fixing it.
                            C6-7 since mid 2002, no hand control nor triceps.
                            my website & my job (in France): Accessibility advisor www.acceslibre.eu
                            Also working on a French research about Peer counseling and Empowerment.

                            Comment


                              #15
                              I found a reasonably easy solution after working on my learning curve. In the process of changing my Helium chair from 2 degrees camber to zero camber, I learned that the angle was set by the tapped hole in the camber tube, and not by the axle sleeve. Yeah, yeah, it's obvious in hindsight and everybody else already knew this.
                              Anyway, this creates a pretty easy way to make the wheels interchangeable with my ZRa that has 1/2 inch axles. Since the 12mm bore in the axle sleeve is concentric with the OD, it's an easy job to drill or ream it to 1/2 inch. Then I can buy a set of 1/2 inch axles and get them turned down to 12mm (0.472 inch) only for the part of the length that goes in the bearings. This would leave over half of the 1/2-20 thread depth (with a minor diameter of 0.437 inch), probably strong enough for the light loads required to keep the nut on. If I get doubts, installing the nut with JB Weld would add some security. Then these wheels function like they have 1/2 inch axles.

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