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  1. #16
    Join Date
    Apr 2019
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    Adelaide
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    589

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    So my motor appears to be very over-powered. Does anybody see an issue with this?

    EDIT:
    If I understand it correctly (and I probably don't), an 850W rating is the power the motor can output for ever without damage. The motor will not necessarily be running at 850W all the time? Free running my DIY scraper would presumably see it use a far lower amount of power as there is no load. If I pushed the blade into the workpiece with everything I had it was exceed 850W?
    Last edited by Mk1_Oz; 15th Jan 2022 at 09:00 PM. Reason: thinking time...

  2. #17
    Join Date
    Feb 2013
    Location
    Laidley, SE Qld
    Posts
    1,038

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    I have this repurposed reciprocating saw - its not my work - which weighs just under 3kg.

    Story time. I forget who the donor was, this Bunix as it was referred to was donated to one of the sadly missed Phil Fehring's (Machtool) scraping classes. All the names went into a hat, I was the lucky winner.

    IMG_4381.jpg

    IMG_4382.jpg

    IMG_4383.jpg

  3. #18
    Join Date
    Oct 2007
    Location
    Alexandra Vic
    Age
    69
    Posts
    654

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    Quote Originally Posted by Mk1_Oz View Post
    If I understand it correctly (and I probably don't), an 850W rating is the power the motor can output for ever without damage.
    The motor power rating is the maximum power level the the motor can be operated at long term at whatever duty cycle the manufacturer specifies. Off load the motor alone would be in the 85 to 100W region, but in usable form with drive mechanism losses etc would be higher. Once upon a time power ratings were specced for mechanical output power, nowdays it is a mixture of mechanical power output and electrical power input depending on manufacturer, application, and price point.

    Power rating is based on wire sizes, number of turns in the windings, and the units ability to dissipate heat. Overload the motor, it tries to draw more current to provide the power output being demanded, it generates more heat that may not be dissipated, overheats and burns out. There is no issue with operating the motor below rated power provided that you meet duty cycle requirements, the motor basically runs with less current and heat buildup.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  4. #19
    Join Date
    Oct 2008
    Location
    N.W.Tasmania
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    1,407

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    Of course all things being equal, the more powerful the motor, the heavier it will be, and the more expensive to make because it uses more material. With a Biax type scraper, it is advantageous to have a certain mass, to resist the push back from the scraper blade on the workpiece. The more mass, the less reaction felt by the operator. A compromise has to be reached, so that the tool is not so heavy in the hands of the operator that it tires him (or her) prematurely, or perhaps a design featuring a reciprocating balancing mass moving 180º out of phase with the blade to keep the vibration level in a reasonable comfort zone. A spring balancer as referred to by Stu will enable you to have more mass without having to carry all the load on your own.
    I, like nearly everyone else would love to have a cheaper alternative to a biax but sadly the demand volumes are not there to support alternative suppliers it would seem.

  5. #20
    Join Date
    Aug 2010
    Location
    Near Bendigo, Victoria, AUS
    Age
    72
    Posts
    3,102

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    Given that most members here only ever use a scraper for a short period at a time (a few weeks), and that quite a few of us have them, I wonder if we can do a "loan scheme" or "rent scheme" on the forum?
    I have a BIAX flaker that I rarely use and certainly would be happy to make it available to such a scheme. My scraper is in use a bit more frequently (I hate and mostly fail in filing and can often do a nicer job scraping), so there are a few reservations about that one....
    Ideas? Concerns? Solutions?
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  6. #21
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    9,088

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    Quote Originally Posted by Mk1_Oz View Post
    So my motor appears to be very over-powered. Does anybody see an issue with this?
    Mine is 840W, I doubt 10W will make much difference


    One thing I should add here. When I first made mine I know I said a few times that "I can remove as much metal per cycle by hand as I can with the bunix"or something along those lines. That was when I had it set to a pretty short stroke. When I finally upped the stroke length that statement because BS but may not have been corrected everywhere, so if someone comes across that please disregard.


    I'm not so sure about the mass reaction theory. Yes it applies to any moving mass in the tool, but surely ANY work done by the tool does goes into the operator? The best mass can do is average that out over time. So yeah maybe a bit, but given the amount of work being done, the number of strokes and the at best 50% difference in mass.....twice "not much" still isnt a great deal(or is it not as simple as "twice"?).

  7. #22
    Join Date
    Jul 2006
    Location
    Athelstone, SA 5076
    Posts
    4,255

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    Quote Originally Posted by jhovel View Post
    Given that most members here only ever use a scraper for a short period at a time (a few weeks), and that quite a few of us have them, I wonder if we can do a "loan scheme" or "rent scheme" on the forum?
    I have a BIAX flaker that I rarely use and certainly would be happy to make it available to such a scheme. My scraper is in use a bit more frequently (I hate and mostly fail in filing and can often do a nicer job scraping), so there are a few reservations about that one....
    Ideas? Concerns? Solutions?
    Are Biax scrapers available for hire from any where in Aust?

  8. #23
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,651

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    Quote Originally Posted by jhovel View Post
    Given that most members here only ever use a scraper for a short period at a time (a few weeks), and that quite a few of us have them, I wonder if we can do a "loan scheme" or "rent scheme" on the forum?
    I have a BIAX flaker that I rarely use and certainly would be happy to make it available to such a scheme. My scraper is in use a bit more frequently (I hate and mostly fail in filing and can often do a nicer job scraping), so there are a few reservations about that one....
    Ideas? Concerns? Solutions?
    Its a great idea Joe, but unfortunately I can see how it could go pear-shaped if it were a general loan/hire thing.
    Given that they are hideously expensive to replace new, and not readily available used (and still relatively expensive), my main concern would be what happens if one gets lost/damaged or smokes a motor etc.
    In my case as a potential loanee, I'd be hesitant to take on the responsibility of borrowing a genuine Biax knowing that if something went wrong I could potentially be up for a few thousand to make it right. Some might not have that concern and be happy to take the "all care - no responsibility" approach, but personally I cant.

    Steve

  9. #24
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    Jul 2006
    Location
    Athelstone, SA 5076
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    Quote Originally Posted by OxxAndBert View Post
    Its a great idea Joe, but unfortunately I can see how it could go pear-shaped if it were a general loan/hire thing.
    Given that they are hideously expensive to replace new, and not readily available used (and still relatively expensive), my main concern would be what happens if one gets lost/damaged or smokes a motor etc.
    In my case as a potential loanee, I'd be hesitant to take on the responsibility of borrowing a genuine Biax knowing that if something went wrong I could potentially be up for a few thousand to make it right. Some might not have that concern and be happy to take the "all care - no responsibility" approach, but personally I cant.

    Steve
    would insurance be an answer?

  10. #25
    Join Date
    Aug 2010
    Location
    Near Bendigo, Victoria, AUS
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    72
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    I'd be extremely surprised if any were for hire somewhere in Australia. In fact, I suspect the total number of Biaxes in Australia would be less than 30 - and probably more than half in possession of members of this forum - lol....
    The issue of repair/replacement on failure or loss is the biggest concern, of course.
    Anyone got any ideas of how hire services deal with that? What sort of insurance would be available?
    It just seems a pity that we have these expensive and difficult to get tools for occasional use and couldn't find a way to share them....
    When I loaned a member my magnetic drill (replacement way over $1000), to drill 200 holes in 50mm steel plate, I did have some concerns about life-span reduction, but the machine never even got warm drilling the holes - unlike to operator.... and I was glad I could share it.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  11. #26
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    Nov 2017
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    Geelong, Australia
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    There’s definitely hire insurance available Joe, but I don’t have any idea of costs or conditions.

    That could be a reasonable solution from my perspective.
    Even if the excess was say $500 it would bring the financial risk for both parties to a reasonable level IMO.

    The other thought I had was what about some sort of group Bunax project. Decide on a cheap donor tool and build a bunch of them.

    Steve

  12. #27
    Join Date
    Jul 2006
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    Athelstone, SA 5076
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    Quote Originally Posted by Stustoys View Post
    Mine is 840W, I doubt 10W will make much difference


    One thing I should add here. When I first made mine I know I said a few times that "I can remove as much metal per cycle by hand as I can with the bunix"or something along those lines. That was when I had it set to a pretty short stroke. When I finally upped the stroke length that statement because BS but may not have been corrected everywhere, so if someone comes across that please disregard.


    I'm not so sure about the mass reaction theory. Yes it applies to any moving mass in the tool, but surely ANY work done by the tool does goes into the operator? The best mass can do is average that out over time. So yeah maybe a bit, but given the amount of work being done, the number of strokes and the at best 50% difference in mass.....twice "not much" still isnt a great deal(or is it not as simple as "twice"?).
    what length stroke did you end up with

  13. #28
    Join Date
    Jul 2010
    Location
    Melbourne
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    9,088

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    Quote Originally Posted by eskimo View Post
    what length stroke did you end up with
    Tricky
    Having just reread my first post in the thread I linked, I had forgotten I even had that idea about "steps", what I actually built uses a couple of grub screws and a tee slot to give infinitely adjustable stroke length.
    A quick check has it adjustable between 0-11mm.
    It was set on 4mm but I'm pretty sure that's more finished.(its been awhile)
    Most likely just maxed it out when roughing.
    Last edited by Stustoys; 18th Jan 2022 at 02:55 PM. Reason: indefinitely adjustable lol

  14. #29
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,779

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    Hi all,

    I'm in need of a power scraper but I just cannot justify the expense of a Biax machine.

    I would be keen on a group online project to build a Metalwork forum project copy!

    There a few members on this forum who have successfully made these machines from a cheaper donor machine. I'd be keen to do the same.

    We could start a joint project thread.

    Simon


    Sent from a galaxy far far away
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  15. #30
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,439

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    Hi Guys,

    Some time ago either Lidl or might have been Aldi, "Powerfix" brand anyway, sold an electric scraper intended for use on wood or wallpaper, complete with several chisels. One intended for wood, about 3/4" inch wide is an ideal candidate for modification as a metal scraper. The machine has a variable speed control and will reduce the speed to almost a stop. I modified mine with a carbide insert when I made my Brooks grinder ! Once you got used to using it, it worked well. Without going and digging it out the motor was about 250 watts.

    I've seen these same electric chisels on Banggood and Ali express for the same money that I originally paid which was £29 or £30. I've since used the tool for removing grout from between floor tiles prior to re-grouting them.
    Best Regards:
    Baron J.

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