DIY dyno build

Discussion in 'Old's Cool' started by adrenal, Aug 23, 2013.

  1. adrenal

    adrenal skrunkwerks.com

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    Here's the design of an inertia dyno I'm currently building:

    [​IMG]

    [​IMG]

    The inertia of the main wheel has been designed to suit bikes form the last century - 70's-80's. Mainly airheads. The red wheels can be installed when more powerful bike are being tested. The build is about 70% complete..
    #1
  2. adrenal

    adrenal skrunkwerks.com

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    almost 1/2 tonne K1045 steel! OD460mm x 300 wide

    [​IMG]

    Drilling pilot hole for boring:

    [​IMG]

    Boring to final ID:

    [​IMG]
    #2
  3. _cy_

    _cy_ Long timer

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    holy cow.. what a lathe!
    #3
  4. adrenal

    adrenal skrunkwerks.com

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    yeah, don't want to get your tie caught in that one!
    #4
  5. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    Oh, man this is gonna be good!
    #5
  6. dhallilama

    dhallilama Been here awhile

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    um. i've built plenty of my own equipment and such... but this is friggin' awesome. just. plain. awesome.
    #6
  7. downdog

    downdog Adventurer

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    You just got this stuff lying around in your shop? :D

    Cool!
    #7
  8. k-moe

    k-moe Long timer

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    Hmmm... I was hoping to see that lump being spun on a mish-mash of trailer tires driven by a pickup on a jackstand, and you working the OD with a file. Where is the adventure in doing things the right way? :lol3
    #8
  9. pommie john

    pommie john Long timer

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    How are you going to calibrate it?
    #9
  10. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Dang! The initial post looked pretty unsubstantial - maybe something I could build.

    No way, Jose!! :eek1
    #10
  11. victor441

    victor441 Long timer

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    VERY cool! something I'd mused about myself, will be following this with much interest...
    #11
  12. adrenal

    adrenal skrunkwerks.com

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    :lol3 I've seen those rigs - much harder to improvise like that I reckon.

    @pommiejohn. good question.Inertia dynos are not hard to calibrate. A matter of calculating the polar moment of inertia of the lump and plugging into the dyno software. Then there are ways of determining friction losses through the bearings etc and plugging these into the software as well.

    But as final tweak/check, after a run on the dyno I'm going to ride straight over to a 'real' dyno which I know is well calibrated and compare numbers.
    #12
  13. adrenal

    adrenal skrunkwerks.com

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    While better machinists than me were producing big chips, I started on the frame:

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
    #13
  14. pommie john

    pommie john Long timer

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    I remember reading that Dynojet just couldn't get the calculations to match the readings, so they measured a known bike and used that as a starting point. ( I think that's what happened).

    One thing to bear in mind ( that every dyno place I've been to in Brisbane ignores) is airflow through the dyno room. A 1000cc motor on full song flows thousand of litres of air through it each minute and it needs a good supply of fresh air delivered to the room.

    Most dyno operators don't seem to realise this. I was at one place and we kept getting inconsistent readings that didn't make sense. We went back to the original jetting and didn;t get the same power curve. Then we noticed that our eyes were watering and stinging and it turned out that we had used up lots of the oxygen in the dyno room and that was making it run rich. Opening the doors and flushing the room with fresh air got us back to consistent reading. We ended up running with the doors open and finally got readings that made sense.
    #14
  15. adrenal

    adrenal skrunkwerks.com

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    Interesting. Yep consistency and repeatability is key. In my book, the accuracy of the absolute HP number is far less important than knowing if your mods are heading in the right direction and by how much in percentage terms.

    I've drawn up a dyno room. It has a huge ducted fan cooling the bike that pulls gob loads of air from outdoors. Sounds like a jet turbine!
    #15
  16. ontic

    ontic

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    :clap

    I can't wait to see this thing, that lathe work is wild.

    What kind of surface is the main wheel going to have? Thinking about grip and tyre traction...


    :lurk
    #16
  17. mousitsas

    mousitsas Long timer

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    Very interesting built. Only 'objection' I might have is that it is inertial so you can't have measurements at constant rpms, but I don't know how important this is.
    #17
  18. anotherguy

    anotherguy Long timer

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  19. Rob Farmer

    Rob Farmer Long timer

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    great stuff :clap


    Or you could go the Norwegian way :eek1

    <iframe width="560" height="315" src="//www.youtube.com/embed/fwPuzEhB1LI" frameborder="0" allowfullscreen></iframe>
    #19
  20. adrenal

    adrenal skrunkwerks.com

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    The lump has 4mm machined cross grooves. All will be revealed !
    #20