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Recent content by NDimitrov

  1. NDimitrov

    Rebuilding small engines for longer life

    If the cylinder bore wears, it could be a combination of a short piston skirt and a low rod/stroke ratio. In other engines the low R/S which comes with increasing stroke, results in premature wear due to increased forces on the piston skirt . An example is the kia 1.6 and 2.4 I4 engines .
  2. NDimitrov

    Threads rolled vs cut

    Hi all, the answer to my question is in almost every engineering book, but how far off are single point cut threads from rolled ones ? To my knowledge the best scenario, regarding strength and fatigue life is rolled threads after heat treatment, but that's quite difficult to achieve in the...
  3. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    Judging by your username it's no surprise you caught that right away. In fact there are two issues with my previous setup. One is the length of the arms, which in my second attempt is 150 mm (that gives a normal frequency of less than 7 Hz ). And the output of that adxl 335 is very noisy. The...
  4. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    So I cobbled together some build information for this balancer . Hope it helps somebody . https://files.engineering.com/getfile.aspx?folder=69d20bc2-c38d-4579-836f-fa696415dc62&file=export.zip
  5. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    I'll cobble together a list and come back to you . If I'm honest, I'd build it much simpler next time .
  6. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    OK, a bit of a delay but here is some progress . I got the halves to weigh equal (+/-0.2 g ). I have the correction weights done as well . The position sensor is a hall effect 0-360 degree 0-5v output sensor, in effect giving me an absolute encoder . I'll get some play...
  7. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    I'll have to make them myself . Seeing the bobweight will have to be more than 1kg I'll be making them from steel. Calculating the acceleration of the piston in different angles with this calculator http://www.pats.ch/formulaire/cinematique/cinematique3.aspx I don't see 50 % as the ideal...
  8. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    I'd like to balance the flywheel as well . And give me more room for the drive motor . Those ADXL335 acclelrometer don't have any crosstalk between the axes , so I don't expect to see anything from deflection in the Z axis . Might end up putting a steel wire and tensioner to reduce deflection .
  9. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    That's what it looks like . Nothing fancy . For the drive I'll use a 9500 rpm angle grinder with some electronics to limit the rpm .
  10. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    There is quite a difference in weight between the original and forged rods that'll go in . And while I'm at it I'd like to also remove as much unneccessary weight as possible . Much like David Vizard shows in his videos . And to get back on topic . On a 5 cyl crank I expect number 3 journal to...
  11. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    The crankshaft in question is for an inline 5 cylinder diesel . I expect to see 5 distinct disbalances, and when the time comes to get it in spec I'll try adding play-dough until everything is balanced .
  12. NDimitrov

    DIY crankshaft balancing with an oscilloscope

    Hi all, since I cannot find a local place to balance my crank I started to make a balancer stand using ADXL335 accelerometers and a QRD1114 looking at a reflective tape for triggering . Finding the heavy spot using the acceleration plots is the easy bits . I can't make the connection between...
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