"Fat Boy" 12/118 thrust engine

[pitciblackscotland]

Good for you John, all that R&D looks like it's paying off

Cheers,
Mark.

[racket]

Hi Mark

Yep , she's finally doing what she should . ............LOL, took me by surprise when the test stand's rear wheels left the trailer deck and it started to tip forward , I can barely lift the rear of the stand.

The maximum difference between thermocouples was 47 C degrees at a 3.5 PR , last test it was 216 C degrees at 3.5 PR .

Compressor efficiency is holding good at better than 80% even at a 3.5:1 PR , a few points higher at more modest speeds ..

Jetpipe total pressure P4t was 8 psi at 3.5 PR , a few psi below theoretical ,( 2020, after recalibration P4t g/g found to be under reading by ~2 psi , so P4t ~10 psit) but so are my temps , a slightly smaller jetnozzle could correct this as its currenty 107 mm and my design size was 4" - 101 mm , but I went with the slightly bigger one for safety in these early tests .

Even the fuel burn rate was around 2,400 ml/min which is close to "design" .

I'm satisfied with the outcome , thanks to Monty supplying the larger G Trim turbine wheel its been invaluable , ........ thanks Monty :-)

Cheers
John

[Deleted]

Hi John


Running real well.... going to need something with good tyres to handle that power

Wonderful

Chat Soon
Andy

[Sweetenough]

Hi John,
Congratulation to a successful test run!
Really impressive to see the take off behavior of the test stand!

Cheers
Thomas

[racket]

Hi Thomas

LOL.....yep , it was something different , thankfully it was well tethered down , so restricted lift .

The thrust at 3.5PR should have been at least 160lbs from the temps and pressures in the jetpipe , velocity ~1565 ft/sec and a mass flow of ~3.2 lbs/sec , but at near 4:1 PR there was a big increase in thrust causing the test stand to lift , unfortunately I didn't get any temps or pressure readings as I wasn't going to take it that far.

Theres still some fine tuning that could be done , but its close enough for now .

Cheers
John

[finiteparts]

John,

Congrats on the run! Glad to see it running so well.

- Chris

[racket]

Hi Chris

Thanks for that , yep, I'm pretty happy its finally getting there , its been a bit of a long process but I've learnt a lot along the journey .

Next step is to setup an Allison C30 4th stage freepower wheel downstream , fitted onto the input half of the new gearbox I'm building ibb.co/nn90Vfd , then do some static stalled torque readings for the "pinion" , it'll provide some power output guide for the engine rather than having to make up a thrust measuring stand .

Possibly the thing thats made me the happiest is the combustion improvements with this very short flametube, the jetpipe temps are more "even" and they're staying that way up the full range of fuel flows, a ~40 C degree difference at 0.7 Bar P2 and 47 C deg at 2.5 Bar, well within the variability of the syringe bore size differences , also the fuel flow rate isn't showing any excessive flows that could be linked to poor combustion , I feel what I'm putting in is actually being burnt , theres now only a 10 psi pressure drop across the injectors at a 3.5 PR, which from my earlier flow testing of the fuel manifold and 19G injectors would have produced ~2,400 ml/min- 144 lph - 38 US GPH - 250 lb/hr flow , much better than some earlier test runs where I had flows heading towards 4 lpm where most of which was probably being blown out the exhaust unburnt

Cheers
John

[turboron]

John, your persistence in getting "Fat Boy" lined out is an example to all.

Thanks, Ron

[racket]

Hi Ron

LOL.......theres been more than a few times when I thought I'd never make it , but let it sit for a few months and come back to it seems to work for me , ........my motto " Theres always a way around it" :-)

My first build with the TV84 took a decade to get sorted , this one has been relative quick at 4 years .

Cheers
John

[turboron]

John, thanks for sharing your experience on the time it took you to sort the bike and the Fat Boy. I started work on centrifugal compressors gas turbines in 1968. I started my Mike Early SJ10 based DIY gas turbine in February 2013. In other words, I have been working on it for amost 7 years. I still have to test to full power and finished the FADEC digital control. Time flies when your are having fun.

Thanks, Ron

[racket]

Hi Ron

LOL............the years start to go faster the older I get ............I'm running out of time real fast ;-)

Cheers
John

[turboron]

John, Mike Early set a good example for us. He was developing DIY gas turbines when the sand ran out of the hourglass.

Thanks, Ron

[racket]

Hi Ron

Thats seems like a suitable objective ;-)

Cheers
John

[racket]

Hi Guys

A start has been made on the freepower stage to make up an assembly to test stall torque outputs .

A dummy freepower pinion shaft has been made up to fit into the pinion section of the gearbox that will have the C30 4th stage freepower wheel at one end and a keyed collar at the other end which will have a "2 foot" arm welded to the collar at one end and a pickup for a spring balance at the other to measure the foot pounds of torque produced .

The assembly will be mounted up onto an extension of the test stand







Now to make up the tin ware

Cheers
John

[turboron]

John, it is great to have experimental data to bounce off a analytical prediction. What do your calculations predict?

Thanks, Ron