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Arron25

Flywheel/Prop Substiute

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Is it possible to use a flywheel as a prop substiute on my motor (Sub EA81) for testing?. I need to do testing in a domestic surround, and apart from saftey would be quieter without the 72" prop. making wind..

Thanks Lyle

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Have seen it at airshows when manufacturers have demonstrated engines, usually made from wood.

 

i wouldn't go too heavy though for fear of risking the psru, maybe 2x auto trans flex plates off a V6 Commodore or Falcon 6? Thinking cheap and easy to get locally.

Edited by bexrbetter

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The fly wheel only will not allow the engine to develop any meaningful power, a propeller loads the engine as revs rise like a dyno would.

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Yes you can make an engine test setup. The engine cooling needs to be catered for, and there must be a way of applying a torque load to extract power. A flywheel will not load the engine by itself.

 

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The airlines used stubby paddle bladed  props of four blades and reduced diameter for engine runs /testing An open prop is pretty dangerous. and the engines were air cooled It's liquid cooled and an auto engine so use a standard engine dyno if you must do testing and you will get some actual figures you can use to get the best prop for your plane/ engine combo.

  IF you just want to run it without load the original flywheel must be OK as they also had the clutch attached in the manual models . I've seen engines run minus flywheel and it didn't sound as though it was doing the engine much good. They often don't want to idle and give the starter a hard time if it kicks back, although many modern motorcycle engines have no or very little flywheel and seem to get away with it .Nev

Edited by facthunter
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I think I would be concerned about the substitute prop/flywheel balance - could get a heep of vibration.

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Any original flywheel would have been balanced and If you make it of billet steel the density is uniform and if machined on centre won't require balancing. Nev

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1 hour ago, facthunter said:

Any original flywheel would have been balanced and If you make it of billet steel the density is uniform and if machined on centre won't require balancing. Nev

Depends - cant speak for all but at least some fly wheels are balanced to the engine, so will not be balanced to the aero engine.

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Motorcycles use balance weights inboard of the main bearings and often quite large alternator magnets in an outside running configuration. In the case of the Kawasaki Vulcan 2000 I think the crank was 17Kg before attaching anything.

 

I like bex's idea of using flex plates. I don't like the idea of using "wood". That said, a wooden propellor can be imagined as just a disc with most of the bits missing

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Put the old flywheel back on for static testing of idle and part open throttle and a short burst of opening the throttle 

 

Put he engine into the aircraft and do open throttle down the runway with the prop on unless you want to spend a lot of money hiring a dynamometer with fully developed cooling system.

 

 

 

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Every article of overhaul information I have ever read, and every bit of training I've ever received, said you do not run ANY engine without coolant, for more than 30 seconds, for fear of causing engine damage.

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There is a big difference between running with no coolant ( air in the coolant spaces in the block ) and no cooling circulation system. The latter implies that there is liquid in the engine cavities.

I reckon that the latter is what bex was referring to.

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 Anyhow a flywheel should be direct on the engine shaft  Not after going through a PSRU .  Drag Motors don't run any coolant but they are a bit unique. I wouldn't recommend running a liquid cooled motor dry of coolant for more than a very short time as it's not warming evenly. By the time some parts are really hot, others are not even warm. Good cooling systems circulate  coolant through the motor only through a by pass until the temp is up and achieve a more uniform heating process. Nev

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Advice wanders ..it is natural on forums and I thank all who have contributed... At no time was I ever to run without coolant.. The reason for the prop simulator was to retain the motor in place in the plane with all cooling instruments exhaust just without the 72" 'food processor'. Plane is in my shed at home , and wanted to run it before I move it out to a hangar to put it all back together...  Now I will make an engine stand to with a firewall facsimile to mount the dynafocal  etc to , bolted in my trailer so I can get it out to where I can run it up properly and do proper testing.

The pic is the unit the original motor was tested on. Would have liked to use it again, but it disappeared to NSW when the owner moved. Anybody know where it went?

Thanks Lyle

1160157814_ThrustMasterEngineTester.thumb.jpg.d65d9ab69c629929c2aa079a8dbf8e19.jpg

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On 15/11/2019 at 5:02 PM, onetrack said:

Every article of overhaul information I have ever read, and every bit of training I've ever received, said you do not run ANY engine without coolant, for more than 30 seconds, for fear of causing engine damage.

I must tell 25 million VW owners that one. 😝

 

On 15/11/2019 at 5:17 PM, Bruce Tuncks said:

There is a big difference between running with no coolant ( air in the coolant spaces in the block ) and no cooling circulation system. The latter implies that there is liquid in the engine cavities.

I reckon that the latter is what bex was referring to.

15 years of importing Jap engines and bench running them, no coolant, doesn't hurt them for 2 or 3 minutes.

 

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The Cri Cri design used a homemade style of dynamometer.  A piece of square section of wood.  It has been designed and "calibrated ," to test each engine.  It provides enough air for cooling and enough ploar moment of inertia for testing.  Not sure of size details but maybe a safer option as I think that the diameter of the wood maybe less than a prop.  The square section provides drag, the HP of the engine is determined by the max speed that the engine can get to.  If I remember rightly the HP is a function to a power of around 5.  Not sure anymore, old age 😀, this maybe of help in testing.  If it is interesting and relevant, and you want me to, I could look up the function.  

 

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The square section of wood for a homemade dyno is quite a good idea. I never cease to be surprised by the number of people who mount aircraft engines with props on trailers, and who then throttle them up for testing or display, with what appears to be totally inadequate restraints. If you're going to test with a prop attached, make sure your test apparatus has more than adequate restraints, against the thrust being produced.

 

Check out the engine display clown from 15 seconds into this video ....

 

 

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GOOD GOD!!!! there is one born every minute and what about the organisers/management of the even & those looneys standing anywhere near/infront of this contraption - are they ALL nuts!!!!!!????????

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He appeared to stop it with the ignition switches not mixture control. Impulse couplings? 

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Skippy, I don't think I've ever seen so many Darwin Award candidates, in one group. That piece of red and white tape must be good stuff, if it's capable of stopping a runaway radial.

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I have always wondered about the sanity of men who wear peaked caps the wrong way round, This one seems to attend more to his cap than to anything else. Reminds me of a flash in the pan Aussie tennis player.

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