Marimba!

  1. Screwdriver

    Screwdriver Member

    Messages:
    6,481
    UK London
    Not my problem :dontknow:

    It's a 500 mile round trip now she moved out of London.

    The actual problem now is that I can see it's not only going to be enormous, it will also be fantastically heavy. But hey, that's not my problem either! :cool:
     
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  2. Mark 2

    Mark 2 Forum Supporter

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    406
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    London UK
    Did you hear about the lump of wood that walked into The Marim bar and came out half cut :laughing:
     
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  3. Screwdriver

    Screwdriver Member

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    6,481
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    No. Did anything funny happen?
     
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  4. Parm

    Parm Oh how I’ve missed my play pen this year

    Messages:
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    Location:
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    Will be a lovely present for the lad and a great conversation piece for the grown ups
     
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  5. Screwdriver

    Screwdriver Member

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    6,481
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    On to the resonator.

    I found this reasonable looking panel in the shed.

    [​IMG]

    I has a decent thick veneer and solid wood filler strips. Looks a bit cupboardy to me but it's lighter than the solid oak floor tiles I had been looking at. First and most difficult jopb (without a table saw) is to rip it to length. Incredibly, the bandsaw did a decent job of it.

    [​IMG]

    I won't bore you with the typical issues with "found material" like edge damage nail holes and splits or as in this case, one veneered edge but no other. The front and read panels require a 4 degree bevel which was a perfect job for the linisher.

    [​IMG]

    Get one good edge then just mark out the dimension the next edge has to meet.

    [​IMG]

    I chopped out the base so that it rests at the front and rear, possibly on little feet if there's time.

    [​IMG]

    There is a base for the resonator and a couple of baffle plates to go in there so it doesn't stay open but I do need to finalise the construction before finding and chopping up a suitable panel of ply (as yet undiscovered!).

    [​IMG]

    Once the resonator is done I can mark out the pins and drill the bars and fit some handles and... damn, I am running out of time!

    Back later.
     
  6. Screwdriver

    Screwdriver Member

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    6,481
    UK London
    Well that was a lot trickier than I had hoped. Glue up was fiddly but I didn't want to screw or nail it. The angle meant I needed an angled shim and it just wanted to pop out under pressure. Plus I needed to make sure the box didn't twist.

    [​IMG]

    Yes inappropriate clamps, couldn't find them either...

    Main event tonight was the soundboard (for the want of a better word. Didn't have any material on hand except some massive sheets of ply or a bit of a plank. I may regret using it as it dries out but hey, ho, at least it will get done. But it's an odd shape to say the least which when you tilt it up at an angle creates a headache working out the dimensions. The headache is compounded by the need (in my case) to keep one good straight edge to work from. Long rip cuts are very difficult on a bandsaw, especially if they are also angled! Anyhow, the calculations...

    [​IMG]

    Map onto a plank.

    [​IMG]

    Cut out.

    [​IMG]

    Had to account for the increased length due to the tilt AND the thickness of the plank when the ends are angled. Makes the required stock length 2.7mm longer. Might not sound like much but a 2.7mm gap in the soundboard would be a disaster.

    [​IMG]

    Loosely fitted for now because I don't want to disturb the glue up. Tapers are extremely sensitive to adjustment, just a few mm off the side and you'll end up shifting it by a mile. In this case I think the ratio is about 10:1 but even so, it's not something I want to get wrong at this stage.
     
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  7. Screwdriver

    Screwdriver Member

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    6,481
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    Disaster. The glue failed. Just fell apart.

    [​IMG]

    It was because I had too severe an angle on the end caps (looks like I doubled it) so that the sides bent to accommodate it and the glue joint was forced apart by the back board. Pretty old glue and impermeable finish on the board didn't help either.

    So I glued it and screwed it.

    [​IMG]

    Happy with the fit of the back board which I had been worried about more from a logistical perspective, how to fit it tightly into a glued up box, and how to support things during the assembly etc. But it went in good and tight, exactly 1 1/2 inches deep at one end and 3 1/2 at the other (except in mm).

    Of course the other head bender is: are the sides of the tapered section perfectly 90 degrees once it is angled inside the box as shown?

    Answers on a postcard...
     
  8. Screwdriver

    Screwdriver Member

    Messages:
    6,481
    UK London
    Houston, we have a problem...

     
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  9. Maker

    Maker nEw mEmBeR

    Messages:
    7,635
    Location:
    Don't ask questions
    Can you scoop more out from the underside of each bar to tune it? You can get spectrum analyser apps to easily measure the pitch, assuming of course you don't hear in perfect pitch. :laughing:
     
    Last edited: Dec 27, 2019
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  10. TechnicAl

    TechnicAl Member

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    7,792
    Location:
    Rotherham
    Its the Jazz version
     
  11. Seadog

    Seadog Forum Supporter

    Messages:
    6,547
    Location:
    NE London - UK
    Each piece needs to be free floating not laid on the box. But I'm sure you know that. Surely the contact with the box is affecting the resonance of each piece.
     
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  12. slim_boy_fat

    slim_boy_fat Forum Supporter

    I bet this seemed a really simple project when ' twas first conceived. :laughing:
     
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  13. Parm

    Parm Oh how I’ve missed my play pen this year

    Messages:
    12,312
    Location:
    Towcester
    Yep it’s never going to resonate if fixed to the box. And it’s the resonance that creates the sound
     
  14. Screwdriver

    Screwdriver Member

    Messages:
    6,481
    UK London
    No I rang each piece individually, on wires, handheld (at the nodes), balanced on rubber etc., truth is, that’s the wrong sort of wood. It should be ok though and a LOT better than it is. I have amassed a few apps to help tune though most of them don’t.

    so I would need to spend a fair bit of time reshaping the cutout and tuning each and every one of them. The plan was to finish off the box first so that I could more easily tune them all rather than one at a time.

    Time was the killer though and I am not taking it with me. I had another issue with the resonator and that was with the fixing/holding posts. I wasn’t able to come up with anything better than simple plastic pins, actually narrow flooring screws over a cut down plastic frame fixing. That made the ideal pin I could wrap a rubber strap around or for some rubber tube etc but I wasn’t happy with handing that over to a 2 year old.

    Even if I could have finished that, I still had the tuning issue which might have meant remaking at least two bars. The shed is a disaster area (hence working in the forge off the top of the anvil) and darkness fell so I went to plan B. Rang up the recipient, told her I had planned this as a surprise but would be turning up empty handed. I think the has been overwhelmed with “stuff” from helpful friends and family so she didn’t mind a bit.

    Means I won’t have to drive the four or five hours with a heavy heart plus I get a good nights sleep rather than stressing myself to finish this off with an all nighter...

    I will finish it off anyway but not for some time yet. This was a Christmas thing, now it isn’t. Hey ho...
     
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