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  1. #1
    Join Date
    Oct 2011
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    Default What's inside a Biax (IV)?

    I was asked by one of the Scrapfest brothers to take some photos of the Biax when I took it apart. I did and thought that they may be of general interest so they have been posted here.
    These things disassemble from the front back. If you remove the back cover all you have access to is the motor brushes. Mine look good. The dome nut on the end holds the strap but doesn't do much else. Underneath is the front bush that the reciprocating rod travels in.
    P1010617 (Medium).JPG
    The front comes away after removing 3 nuts on studs. I was surprised to see (given that this unit is ex USA) that all the fasteners are metric. The photo shows the front housing on the left and the wobbly bit on the right. Once the nuts are removed, the front will just pivot away.
    P1010618 (Medium).JPG
    Next photo is of the stage that turns rotary motion into variable stroke reciprocating. It reminds me of a universal joint. To get past this section the stroke adjustment bolt needs to be removed (castle nut on the end and then unwound) then 3 screws on the front are undone so this part can slide out. As can be seen in second photo (above), there is a cylindrical part with holes around its perimeter. This just screws onto the gearbox output shaft and was removed with a sharp tangential tap. This then exposes two more nuts that have to be removed to give access to the gear box.
    P1010619 (Medium).JPG
    The gear box is purely for speed reduction and filled with (almost petrified) grease. The famous "irreplaceable gear" is found in this section. It rotates in bushes and steps the motor speed down to something sensible. It reminds me of an an angle grinder or perhaps angle drill. I have seen a TIG tip grinder that uses a proxxon drill as the motion source, so for a home made version perhaps something like that could be the mule.
    P1010620 (Medium).JPGP1010621 (Medium).JPG
    As for the famous gear, this is it. It has a metal shaft and the plastic part looks to be something like a Bakelite gear. There seems to be a straight knurl on the shaft, so I'm guessing that the gear is a push fit. The helix angle measures 20 degrees (put scraping blue on the teeth and roll on some paper to get a set of lines) and being Swiss machine, is M0.6 by my calculation. Weirdly it has 47 teeth. Making a replacement will not be impossible although may need some odd gearing to get the helix angle right. Attached is the exploded view I posted in the other thread for reference
    P1010622 (Medium).JPG 4ebc.pdf

    Michael

  2. #2
    Join Date
    Jul 2010
    Location
    Melbourne
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    Default

    Hi Michael,

    No Bakelite inside a Bunnix

    Could the gear have been made on the shaft?
    How close to the last and the second gear come to each other? (how close to the second gear does the third gear need to get?)
    Is the gear on the motor separate or part of the shaft?


    The Bunnix just has one large bevel gear. I wonder Biax went with this system?
    Easier to make?
    quieter?
    less vibration?
    lasts longer?
    All of the above......

    Stuart

  3. #3
    Join Date
    Sep 2007
    Location
    Country West Oz
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    169

    Default

    Is that gear plastic (bakelite) with a metal inner?
    That looks very much like the feed gear from an older Singer sewing machine.
    If you like I can look into that a little further.
    Can you supply some measurements, length, outer diameter etc just to see if it is anywhere near the size.
    Regards
    Bradford

  4. #4
    Dave J Guest

    Default

    Nice right up and pictures, thanks for posting it.

    Dave

  5. #5
    Join Date
    Jun 2008
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    Victoria, Australia
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    Default

    Thanks Michael,

    Great detailed information to have available, I've been a bit reluctant to pull mine apart, but seeing the exploded parts view and your nicely detailed description makes it much easier to contemplate.


    Regards
    Ray

  6. #6
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    Default

    To me, the gear looks to have been moulded (or cut) and then pressed onto the metal shaft (with the metal gear cut on the shaft). There is no clearance between them. I suspect that it has been done this way due to cost (length of steel diameter 30mm vs diameter 12mm) but I wouldn't go past the ideal of a sacrificial part that would break if subjected to serious mis-use. It just sounds like the part loses strenght over time so the amount of mis-use required to break them is less than when it was new.

    Thanks for the offer Bradford, but the plan is now that I have the dimensions I will make some up - probably out of acetal so that Ray and I both have spares. Murphy's law says that once we have the spares they will not be needed so we will be fine (in fact, there is probably a sub-set of laws that suggest even the plan of making replacement parts lessens the likelihood of needing said parts). I suspect a singer sewing machine would be imperial gears as well. For the record, the OD measured 28.9mm and the width was 12mm

    Michael

  7. #7
    Join Date
    Sep 2007
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    Country West Oz
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    Default

    They're from a German Singer and they are metric, that's the goog news.
    The bad news, they are not the same size, od 25mm, width 10mm.
    Regards
    Bradford

  8. #8
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    Default

    I thought both gears where one piece.

  9. #9
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    Default

    Quote Originally Posted by Stustoys View Post
    I thought both gears where one piece.
    I did too until I cleaned the gear up.
    I think the reason for a Bunnix not having a bakelite gear is that this Biax is quite old and back then engineering plastics were basically bakelite (possibly nylon). These days the development of plastics is such that the plastic gears in a Bunnix would have all the strength needed as well as being injection mouldable (cents each). If they are metal gears, then they could be die cast - again very cheap. in the last 50 years plastic has done remarkable things to manufacturing (including spin offs to other areas).

    Michael

  10. #10
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    Jun 2011
    Location
    Australia east coast
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    Default

    Quote Originally Posted by Michael G View Post
    Murphy's law says that once we have the spares they will not be needed so we will be fine (in fact, there is probably a sub-set of laws that suggest even the plan of making replacement parts lessens the likelihood of needing said parts).
    I rely on that principle - I made a spare nut for my boat steering gear just to ensure that I'd never need to fit it. I also put a camlock fitting welded through the deck so I can use an emergency steering system and made a couple spare taperlock flanges, based on the same theory.

    Of course this just ensures that a rabid whale or similar will bite off the entire rudder assembly underwater..... you *cannot* outsmart Murphy.

    PDW

  11. #11
    Join Date
    May 2010
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    Lower Lakes SA
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    Default

    Michael, is there a way to build in a weaker link, on the shear pin principle, to protect the gear? Don't know how you would test it though.

  12. #12
    Join Date
    Jun 2008
    Location
    Newport, Victoria
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    Default

    Hello Michael,

    Thanks for posting those photos. It hadn't twigged that the "special gear" was in the gear box and not part of the wobble drive. I think you're right one could probably use something like a proxxon drill or bunniax as an input to a wobble drive. (Patent US2940324 - WOBBLE DRIVE - Google Patents) .

    I've been toying with the idea of making one up.

    Christian

  13. #13
    Join Date
    Jan 2008
    Location
    Camden NSW
    Posts
    75

    Default Powered Scraper

    I thought I remember that someone on the forum made or was making a powered scraper out of a recipicating saw?

    Garry

  14. #14
    Join Date
    Aug 2008
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    near Rockhampton
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    Default

    Quote Originally Posted by Michael G View Post
    and the plastic part looks to be something like a Bakelite gear.

    Michael

    It is that fibre material that was often used for parts like this... Not plastic...

    Biax 7/EL fiber gear - Page 3
    Gold, the colour of choice for the discerning person.

  15. #15
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    Default

    Ok - technically Bakelite is a thermoset not a thermoplastic, but I think most people would have got the idea. Thanks for the link though (even if it did involve Phil's mate) - I'd mis-counted the teeth and was going to make a 47t gear but as you correctly point out it's a 37t gear.

    Michael

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