Engine dynamometer, anyone?

[rtfm]

Hi,

 

I have recently bought an aero-converted Generac 990cc industrial engine for my project. Repeated emails and phone calls to the manufacturer (Valley Engineering in the US) assured me that the much reworked engine now produces 50hp. I have designed my single seat plane around this powerplant. However, recent discussions with knowledgeable members of a homebuilt aircraft forum in the US suggest that the engine will NOT be capable of producing 50hp.

 

I already have the engine here in Brisbane. What I would like to do now is to put the motor on a dyno and verify the power output.

 

Does anyone know of a local company or person who could perform such a test?

 

Thanks in advance,

 

Duncan

 

 

[facthunter]

It's a low figure by most standards. ( Most machines are hundreds of horsepower) and there may be errors in the reading(s) Being a bit of a skinflint, I would see if I could access some props and see what revs you can get, on a known prop that works on a comparable engine, and what THRUST could be obtained . (Simple tethering and spring balance exercise).Nev

 

 

[rtfm]

Hi Nev,

 

I have been in contact with a builder who recently replaced his HKS with the Valley Engineering Big Twin, and here's what he had to say:

 

The best we've been able to get out of the BT on four different planes: Kolb Twinstar, DH-2, Mariner and Morane Saulnier was 220 lbs of thrust. With the BBT All four aircraft have measured static thrust of 260-270 lbs of thrust. It makes a big difference in performance.

The following clips are of the Mariner and Morane with the BBT. The Mariner's empty weight is over 500 lbs. The 60 hp HKS was removed and the MUCH SMOOTHER AND QUIETER BBT was mounted.

 

The first clip was with no mufflers and the second one with the "mushroom" mufflers installed.

 

http://manddweb.com/upload/mariner-1.mp4

 

http://manddweb.com/upload/mariner-mushrooms.mp4

 

As for the Morane, we have videos at:

 

http://www.kcdawnpatrol.org/Fox4Video.htm

 

We don't have any videos of the KOLB in action but it has flown with the pilot at 170 lbs and passenger at 260 lbs with no problems.

 

Having said all that, we LOVE this engine. We'd NEVER go back to the Rotax. The BBT is MUCH smoother and a LOT quieter. The low fuel consumption is a big plus too.

Interesting - anyone care to make a comment based on what he has reported?

 

Cheers,

 

Duncan

 

 

[facthunter]

At what revs does the engine develop the stated power? Is it geared?. Nev

 

 

[rtfm]

3600 rpm and is fitted with a 1:1.6 PSRU

 

 

[facthunter]

It's fairly low revs to get that power out of ONE litre . It would have to breathe ok, but possible ( my guess) Being geared it would do better than direct drive, particularly with a draggy machine. Nev

 

 

[rtfm]

Question:

 

What limits the revs an engine runs at? I know the standard Generac comes fitted with a govenor - but how can one tell if it is safe to run the engine at (say) 4000 rpm, or higher? Heat dispersion? Internal engine stresses and strains? I also know the racing types run B&S motors a lot faster than 3600 rpm. I'm an almost complete engine ignoramus, so my apologies in advance for the questions.

 

Duncan

 

 

[JabSP6]

RTFM

 

Not sure if this helps but I know CAMit in bundaberg run all the motors they produce on their engine Dyno.

 

4 cyl motor produce around 80hp so it would be accurate to run your motor on.

 

It might be worth a call to Ian to see if he can help out?

 

Safe flying

 

JabSP6

 

 

[rtfm]

Thanks. I've emailed him to see if he can help.

 

Cheers,

 

Duncan