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Geoff_H

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Everything posted by Geoff_H

  1. Geoff_H
    Only go to a garage that has a torque limiter attached to a rattle gun. It is what I do with my alloy wheels, observe the setting and attachment of the device. And when they say that they won't let the car back on the road without them as tight as possible, inform them of their knowledge inadequacies and publish the company on social media.
  2. Geoff_H
    The stud is a spring. Steel is elastic and by extending it just a little very large forces can be generated to hold two things together. How much force is a function of pressure in a cylinder or sideways forces on wheels. The true way to determine the force is to measure the bolt extension. Difficult on small bolts, easily done on large bolts. The extension on small bolts is infered by the torque applied to the nut. The wedge force determines the bolt force by mechanical infered calculations taking into account friction in the nut. Bolts can be over stressed particularly when it is the first 1.5 threads that take the overwhelming part of the strain. It the wheel nuts are overtightened the threads are put under stresses that will allow the thread areas of both the nut and bolt to permanently deform and eventually break the bolt or strip the thread.
  3. Geoff_H
    In the 1970's I was commissioned to do a study on bolt failures. Amongst the things that I discovered was that 90% of the bolt load is taken by the first 1.5 threads. So over tightening, using the full impact force of a rattle gun just damaged the threads. The tyre service I use these days has a torque limiter on their rattle guns. I was able to use the cars wheel wrench to change the flat tyre. If your tyre fitter over tightens the bolts you are at risk of stud failure.
  4. Geoff_H
    A month ago I went through one of the monster potholes in Sydney's castle hill. it damaged the drivers side front and rear tyres. Front tyres are a different size to rear tyres, so I had to buy 4 new tyres. $2000. I also got the experience of driving on run flats at 80km/hr, the vehicle was controlable, but would not have been at any faster speed.
  5. Geoff_H
    For turnover you will also need the coefficient of friction road to tyres lol. I need to a quick calc before in tear into a corner lol
  6. Geoff_H
    Got my medical for Class C drivers licence yesterday. Went to DAME that has been doing my class 2 medical's. She was totally aware of my medical history, only cost $99. Good result. P.S. she is now my GP.
  7. Geoff_H
    My Class 2 far exceeds the motor vehicle medical, but the beauricracy of the government prevents it from being a satisfactory substitute.
  8. Geoff_H
    I did the class 2 basic a few medicals ago. My doctor required a full eye exam and report as per heavy vehicle licence. Took a lot longer than optometrist and cost $160, then my doctor charged $250 for rest. Next med I went to DAME, she did eye test and charged $250. Full class 2 cheaper and let's me night fly, not that I do much of that these days. I see that my dame does the road and maritime so I will go to her.
  9. Geoff_H
    Very shortly I turn 75. NSW require that I get a medical from my GP. She is requiring that I also get an optometrist report at additional cost. I have a class 2 CASA medical certificate the DAME does my eyesight at no extra cost. As a car licence can be a medical for a RAA licence this question is probably a revelamt topic for this site. Anyone had to do the 75 medical?
  10. Geoff_H
    I like the dual cycle engines that are becoming popular in modern vehicles. The combustion starts as an Otto then converts to a diesel cycle (using petrol). These engines are more efficient than both diesel and Otto. When you see the temperature entropy and pressure enthalpy graphs this is shown. The best reason that I like them is that Mercedes is getting 400hp out of a 2 litre engine. I feel that a small engine with that output and efficiency could be the future for aircraft. My vehicle has a 2 litre 250hp engine and gets 6.4 litre/100km, very reliably, it has a dual cycle engine. It's manufacturer was talking about dropping the less efficient diesel engine in its favour. All seems to have changed now that the "climate change religion" reigns suprime.
  11. Geoff_H
    What is Warnervale like these days? Is it good for doing the biannual flight review for a private pilot licence?
  12. Geoff_H
    The speed of sound is a function of the density of the material it is being transmitted through.
  13. Geoff_H
    I am talking about the control systems inside the power systems not the 330kV or 500kV systems, they are very specialised systems. I was the commissioning engineer for the first Eraring 500kV switchgear. Another item that makes large spikes is the size of the wiring. The original power stations used 24/48V systems with 7/0.29 wire, modern systems use 1mm or less. Larger wiring gives larger spikes.
  14. Geoff_H
    I use autocad 3D for 3D printing. I have used acad since its inception in the 1980s ( or about then). I tried a free 3d cad package but it was too hard to learn at my age, something about old dogs and new tricks. 😁
  15. Geoff_H
    30 years ago I was writing acad program files (name eludese at the moment) I was able to take an excel file and extract data and create dwg files from the excel data. The formats for acad and SLC files is well documented. I expect that pdf file format is documented. I am 74 and too old to do it these days but you should be able to find a young budding programmer that would write such a program for you, maybe even for free. It appears that the software exists, for free some of them, do a PDF to DWG search on the internet. Feel free to contact me privately if you wish
  16. Geoff_H
    30 years ago I was writing acad program files (name eludese at the moment) I was able to take an excel file and extract data and create dwg files from the excel data. The formats for acad and SLC files is well documented. I expect that pdf file format is documented. I am 74 and too old to do it these days but you should be able to find a young budding programmer that would write such a program for you, maybe even for free.
  17. Geoff_H
    Is your a to make SLC files?
  18. Geoff_H
    Can I assume that you have pdf files and want them converted to DWG/dxf files?
  19. Geoff_H
    Sorry just realised it was 50 years ago I started work in Power Stations. I am getting old and forgetful.
  20. Geoff_H
    40 Years ago when I started working in power stations we used relays for control. We recorded spikes of nearly 5kV. We imposed a 5kV spike tolerance on the new electronic control gear. We didn't even consider that with the relatively slow switching of electronics a maximum tolerance to 1kV spikes. That was until Siemens forced us to accept the 1kV tolerance. The electronic control systems worked great. The moral of the story is avoid relay switching spikes and go for electronic switching as much as possible.
  21. Geoff_H
    Active inlet dampers could possibly be used to regulate the amount of air into cowling for regulated cooling. Many aircraft use exit dampers, a simpler and better idea to only using as much air as necessary. But inlet dampers such as that used on some vehicles could be used. Inlet restriction may reduce airframe drag, may, but the complexity and weight penalty may negate their effect. It's just a thought, my design process has always been, "what can we do different" then suggest even stupid ideas then examine possible implementation of the stupid idea. I then usually end up seeing that things as they were traditionally designed are the best. I live by the motto that there are no stupid questions just stupid answers.
  22. Geoff_H
    That's why well designed heat exchangers are contra flow. Hot flows one direction through heat exchanger, cooling fluid the reverse.
  23. Geoff_H
    In the early days of my career I did lots of work with low pressure airflow including heat exchangers. It was all designed with mathematics, get the older guys to use experience to modify the maths. The measure extensively when commissioning and alter as needed. It was very impirical. The airflow was with furnace airflow. I am sure that aircraft manufacturers go through several interactions of cowling design, I would expect that with any one off design would need redesign, a reason among others that manufacturers charge so much.
  24. Geoff_H
    The oil cooler was part of it. But there is a lot of similarities between fins and "radiator" flow. Metal cooled by air. Big difference is that the 'radiator' style has to be more complex owing to lower temperature of metal. Yes the Mooney fight was with oil temperatures.
  25. Geoff_H
    With properly designed inlet I would expect laminar flow in, the inside would then ensure turbulent flow in the heat exchanger (reynolds number drastically increasing) and exiting turbulent. One of the biggest problems is a design that works well at climb out velocities then works just as well a cruise velocities. Mooney used an exhaust duct, its opening size adjustable from the cockpit. Mooney always have temperature issues, it was a constant job to adjust the duct.
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