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Thread: Wheelchair Axle Diameter

  1. #1

    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. #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.

  3. #3
    See if you can get new bearings to make the difference.

  4. #4
    Senior Member pfcs49's Avatar
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    Quote 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".

  5. #5
    Quote 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.

  6. #6
    Senior Member pfcs49's Avatar
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    Still thinking about this!
    If the axle receivers are stainless, they will be a bitch to drill!

  7. #7
    Senior Member lazierdog's Avatar
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    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; 09-22-2015 at 11:28 PM.

  8. #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.

  9. #9
    Senior Member robotnik's Avatar
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    @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.

  10. #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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