Paul et al,


   The recent TTC engine run postings, turbo compound threads, and my own
   efforts have started me thinking about an engine test stand and the
   features/performance it should demonstrate.


   Obviously a control/instrument panel would incorporate some of the basic
   parameters like...


     oil pressure

     oil temp

     engine (coolant) temp

     exhaust temp

     manifold pressure

     air/fuel ratio

     rpm

     throttle position

     fuel flow/totalizer

     time

     hobbs


     throttle

     mixture

     ignition



   What other controls/measurements should be incorporated on a basic level?


   What about on a more advanced, special situation level (e.g. waste
   gate position when testing turbos)?


   Should it be easily transportable?


   And what about safety features (fire extinguishers, kill switches,
   etc.)? What do you suggested?


   Ideally a data acquisition and control system would collect, log, and
   display the data. I use National Instruments LabVIEW software and
   hardware (along with other manufacturers like Omega, Interface, Banner,
   etc.) for such at work. But it looks like other solutions are available
   through some of the systems discussed in postings here. Personally I'd
   prefer to use something available and proven in order to get to the
   engine testing instead of debugging I/O systems (even though I do that a
   lot with NI LabVIEW!!). What is available and what are your thoughts on
   that?  There are many automotive type test stands out there for basic
   run in testing. But I would expect an aircraft test stand to measure
   torque and thrust for a prop generated load. Not too many (none???) out
   there that I saw, but please let me know about any that you know of.


   Is there any sort of "standard" test prop that would be suited for
   initial or comparative testing?


   A DIY stand seems more practical from a cost and achieving desired
   capability standpoint.


   Therefore, what would be a good upper limit of each value to start
   sizing a stand?


     Max engine torque = ?

     Max engine thrust = ?


   Obviously the answers to my questions are very subjective with many
   variables and personal preferences that could affect the answers. At
   this point I'm just looking for some rough initial numbers for the upper
   limits and capabilities that "amateur home builder" folks like us might
   like to see a stand incorporate.


   I think the TTC engine might be representative of such performance
   limits? Yes? No?


   And what are the thrust and torque goals for TTC?


   Is anyone else interested in building such a stand?


   So put on your thinking caps, let your imagination run wild, and let
   me now your thoughts on this matter.


   Looking forward to your responses!


   Warm Regards to All,

   Brad Chubb



   Be careful optimizing thrust. The best static thrust is not the best
   prop pitch for an
   airplane.  Here are some prop dyno ideas.



   Airplanes fly on HP.


     HP = Torque  X RPM / 5252


   If you measure the torque and of course the RPM you know the HP.


   An aircraft engine will increase the RPM until the prop torque
   requirements are met.


   Paul Lamar



   Please note that almost every item mentioned is on the dyno Steve and
   Everett built. One other thing to mention is the flow straightening fins
   behind the prop. They found that the torque readings were being effected
   by prop swirl until they put them on. Only important if you are
   interested in very accurate HP readings. Most of the time relative
   readings are good enough. Get your baseline and you can tell if what you
   did helped or hurt your performance. For someone looking to build a dyno
   I would suggest looking for a used airboat prop in good shape if testing
   for high power. They are usually designed for large V8 power and will
   work for 200+ HP

   Bill Jepson


   Brad,
   Try advertising for an existing test stand no longer being used.
   It may not be perfect, but it is a start.

   Milo


   Am I to understand then that a pusher propeller would not affect the
   torque reading or not
   as much as a tractor prop?

   Dale Davies

   Yes. That would be correct. The fact is though most dynos run tractor
   props so they can provide air to the heat exchangers. We have run
   Steve's for over an hour to test heated operation power and for that you
   need a good radiator and oil cooler.

   Bill Jepson

   Bill are you in the Portland area?

   Paul Lamar

   I'm in central California right now. We are moving to the Portland area
   in future.
   I have family in the area and I'm there frequently. I've recently been
   at Steve's place.

   Bill Jepson


   What about the Baker Fan that farmers used to measured the output of their tractors? One could have variable length (Incremental bolt holes) paddle blades, or larger paddles to handle more power. By calculating the flat plate drag for various RPMs and using a prop RPM counter under ($20) one can measure the output HP fairly accurately.

   Dave James

Regarding the pusher and cooling. You could do like automotive chassis dyno,
a box fan or two blowing air across the coolers.

Dale Davies


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