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Thread: Finally gonna try to use Medicare to get a chair

  1. #61
    Senior Member Oddity's Avatar
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    Ahhh, I gotcha. I'm not a material scientist either, armchair analysis all the way.

    I never thought ultimate tensile strength was terribly important for wheelchairs, but maybe it is. Resisting axial stretching doesn't seem like something we need. Both Stiffness and Strength to Weight, at bending points, apply to wheelchair tube stress more so than axial (compressive or tensile) forces, but the obligatory "I'm not an engineer" certainly applies. Aluminum (7075) has higher Stiffness to Weight bending ratio (by ~25%) but titanium (Grade 5 4AL) has a higher Strength to Weight (by ~10%), when measured at bending points, rather than stretching or compressing (axially tensile) points.

    Stands to reason, by using less material (thereby eating into that 10% Str to Wgt bending advantage), titanium frames can certainly be made to be lighter, as raw frames, by that 10% margin. Also stands to reason, that will expand the Stiff to Weight advantage of aluminum (assuming a rigid frame is desired). The old Quickie Ti took this trade off to the extreme! It flexed like a wet noodle under load. The TiLite ZR seems to be more a conservative balance. The TR nearly negates the issue of flex entirely.
    "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

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    "Even what those with the greatest reputation for knowing it all claim to understand and defend are but opinions..." -Heraclitus, Fragments

  2. #62
    [QUOTE=Oddity;1878342]
    (Interesting aside: TiLite frame warranties are the same for aluminum as for titanium. If their titanium chairs were, in fact, stronger and more durable, you'd think they'd have assigned longer warranty periods to reflect that benefit to the consumer. They aren't.)

    (Another interesting aside: Do they make an identical ZR frame in aluminum? Is that even an option? If they're comparing their ZR to, say, their Aero Z, then is that even a relevant claim - beyond its marketing value? I dunno...)

    While the ambiguous wording of the warranty is confusing (and annoying), TiLite warranties the wheelchair frame "for life," despite its "expected life" of of 5 years. The warranty is for the life of the original user.

    Unfortunately, TiLite doesn't offer an aluminum frame equivalent of the TR and ZR, only the "A" (adjustable) versions of each model. Though of course it couldn't hurt to ask.

  3. #63
    Quote Originally Posted by Oddity View Post
    [Titanium] flexed like a wet noodle under load.
    Whereas aluminum may fracture vs flex.

    Want to rethink your statement that there isn't an advantage to titanium over aluminum?

  4. #64
    Senior Member Oddity's Avatar
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    Thanks for the clarification on the warranty! The wording is crappy. If Designs Unlimited wouldn't do a ZR in aluminum, I'd cheekily suggest they change their name to better reflect their limits.

    Seriously, though, I'd buy one, if it was priced lower than their Ti. Couldn't imagine they'd do a "one shot" aluminum ZR for less $, since they aren't necessarily setup to do it quickly, or efficiently, being something they don't do routinely. But, who knows? I guess they do, if I'd ask.

    (On that note, there are precious few options when it comes to reasonably priced, custom "to spec", ultra-light, welded everywhere, non-adjustable, aluminum alloy chairs. Less than a few. Only a couple. Seems like a significant hole in the market. A simple, minimalist, inexpensive, welded to spec, aluminum alloy chair. Is that too much to ask of the industry?)
    "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

    "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

    "Even what those with the greatest reputation for knowing it all claim to understand and defend are but opinions..." -Heraclitus, Fragments

  5. #65
    Quote Originally Posted by Oddity View Post
    Thanks for the clarification on the warranty! The wording is crappy. If Designs Unlimited wouldn't do a ZR in aluminum, I'd cheekily suggest they change their name to better reflect their limits.

    Seriously, though, I'd buy one, if it was priced lower than their Ti. Couldn't imagine they'd do a "one shot" aluminum ZR for less $, since they aren't necessarily setup to do it quickly, or efficiently, being something they don't do routinely. But, who knows? I guess they do, if I'd ask.

    (On that note, there are precious few options when it comes to reasonably priced, custom "to spec", ultra-light, welded everywhere, non-adjustable, aluminum alloy chairs. Less than a few. Only a couple. Seems like a significant hole in the market. A simple, minimalist, inexpensive, welded to spec, aluminum alloy chair. Is that too much to ask of the industry?)
    I reached out to a TiLite contact. Their response:

    -The warranty extends for the lifetime of the original end user. However, it must be normal wear and tear, not abused.
    -No, we just don?t have an aluminum bullet to have a fixed aluminum chair.

  6. #66
    Senior Member Oddity's Avatar
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    I said the only advantages are anecdotal, hypothetical, or marketing claims. There is a dearth of independent research, materially speaking, and even less so medically. Also said the purported advantages don't jive with the cost premium, over the life and typical usage cycle of a manual wheelchair.

    We have no idea if typical wheelchair forces are strong enough to compromise either material's properties. Not a ton of cracked wheelchair posts here...but...

    ...having said that, the number of TiLite 4Al frames we've seen posted here, cracked, tells another story. I suspect because they're made fairly thin-walled, to make up for being naturally 60% heavier than 7075Al, that they don't end up actually being any stronger. "Expected life-time" isn't any longer, according TiLite, which supports this notion.

    There aren't a ton of "cracked frame" posts here, but TiLite enjoys at least a few of the honors.






    Quote Originally Posted by August West View Post
    Whereas aluminum may fracture vs flex.

    Want to rethink your statement that there isn't an advantage to titanium over aluminum?
    Last edited by Oddity; 05-09-2019 at 02:44 PM.
    "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

    "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

    "Even what those with the greatest reputation for knowing it all claim to understand and defend are but opinions..." -Heraclitus, Fragments

  7. #67
    Senior Member Oddity's Avatar
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    Cool! And, for the record, I'd send them a piece of aluminum billet.

    Quote Originally Posted by stephen212 View Post
    I reached out to a TiLite contact. Their response:
    -The warranty extends for the lifetime of the original end user. However, it must be normal wear and tear, not abused.
    -No, we just don?t have an aluminum bullet to have a fixed aluminum chair.
    "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

    "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

    "Even what those with the greatest reputation for knowing it all claim to understand and defend are but opinions..." -Heraclitus, Fragments

  8. #68
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    Quote Originally Posted by Oddity View Post

    (On that note, there are precious few options when it comes to reasonably priced, custom "to spec", ultra-light, welded everywhere, non-adjustable, aluminum alloy chairs. Less than a few. Only a couple. Seems like a significant hole in the market. A simple, minimalist, inexpensive, welded to spec, aluminum alloy chair. Is that too much to ask of the industry?)
    Check out Box Wheelchairs which, I think, fit all of your wishes:

    https://www.boxwheelchairs.com/

  9. #69
    Senior Member Oddity's Avatar
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    Yeah, Per4Max does it too. Lasher too. Prices, on the other hand, are generally worse than high end TiLites when going the boutique", or bespoke, route. Are Box chairs priced competitively?

    (You can get a 'fully-welded', minimally adjustable, 7075 aluminum, ultralight from Top End for ~$2k, at online discounters, fully featured. That's about the only thing I've found that ticks all my boxes.)

    Quote Originally Posted by Tetracyclone View Post
    Check out Box Wheelchairs which, I think, fit all of your wishes:

    https://www.boxwheelchairs.com/
    "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

    "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

    "Even what those with the greatest reputation for knowing it all claim to understand and defend are but opinions..." -Heraclitus, Fragments

  10. #70
    Quote Originally Posted by Oddity View Post
    (You can get a 'fully-welded', minimally adjustable, 7075 aluminum, ultralight from Top End for ~$2k, at online discounters, fully featured. That's about the only thing I've found that ticks all my boxes.)
    Top End is no longer making everyday wheelchairs.

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