Allison 501 turboprop - Completed!

dmk

Nice job Don!  You had some grief with that one and it's really looking good. 

 

 

 

CapnMac82

There were some facinating experiments with external blades on turbofan engines in a hybrid semi-turboprop configuration.  The fuel economy was good, but the sound signature from exposed supersonic blade tips was a detriment

 

 

Wasn't it the Republic F-84H "Thunderscreach" that litterally made people sick from the noise of the supersonic prop tips?

 

That's why they stick those reduction gearboxes on the front of turboprops. I'd imagine the torque multiplication from the high RPMs of the gas turbine stepped down to prop speeds must put out some incredible power. I believe making those gearboxes reliable under all that torque was a big engineering problem for a while. One they figured how to keep the gearboxes from self destructing, gas turbines driving shafts are used in all sorts of applications.

Helicopters are almost exclusively gas turbines now (Helos were really limited by piston engines, jet engines are relatively simple and light weight for the power they put out). A lot of ships have them too (destroyers and patrol ships anyway). Electric power generaton plants use them. I'm sure a lot of other stuff.

 

 

They had a good start in that recips of large power were already using reduction gears.  Those huge radials like the R-2800 and the 3350 helped develop reduction gear technology.  And, in the thirties when gas turbines were being developed, the original idea was the turboshaft.  There were gas turbine/turboshafts of a thousand horsepower driving locomotives in Europe before the Whittle and Von Ohain engines first ran.  The turbojet did not precede the turboshaft.

Nice job Don!  You had some grief with that one and it's really looking good. 

CapnMac82

There were some facinating experiments with external blades on turbofan engines in a hybrid semi-turboprop configuration.  The fuel economy was good, but the sound signature from exposed supersonic blade tips was a detriment

That's why they stick those reduction gearboxes on the front of turboprops. I'd imagine the torque multiplication from the high RPMs of the gas turbine stepped down to prop speeds must put out some incredible power. I believe making those gearboxes reliable under all that torque was a big engineering problem for a while. One they figured how to keep the gearboxes from self destructing, gas turbines driving shafts are used in all sorts of applications.

Helicopters are almost exclusively gas turbines now (Helos were really limited by piston engines, jet engines are relatively simple and light weight for the power they put out). A lot of ships have them too (destroyers and patrol ships anyway). Electric power generaton plants use them. I'm sure a lot of other stuff.

The British Westland Wyvern carrier based aircraft was a pretty successful design, again with a counter-rotating prop arrangement. 3500 hp plus another 1100 lbf of residual thrust. They saw action in the Suez Crisis.

The Westland Wessex helicopter was a version of the UH-34, powered by a turboshaft engine mounted in the nose where the original radial engine was mounted.

Another long lived plane was the Beech D-18, a pre-war aircraft that was in production for many decades, and some are still flying (if they did the expensive main spar retrofit).

And if I recall correctly after doing the S2 tracker radial to turbo conversion research, the turbos are lighter than their radial counterparts.

Oh and thank you Frank Whittle.

Anyone who thinks that building models is playing with toys should read this and many other posts in the various sections of this web site. the knowledge being passed on is phenominal. It includes history, mechanics, physics, philosophy, and a whole lot more. 

Model building teaches some very important skills, such as following directions, hand-eye coordination, working with tools, and more. (patience?) 

Keep it coming Folks. And Don, I will PM you a few picture of the bundle of control cables that run along the ceiling of the B-17G as soon as I find the right file with those pictures. Food for thought, the C-130 and the B-52 started production in the early 1950s and they are still flying. American engineering.

Great, now I want one of these kits!

Space Ranger

And the fan of a turbofan provides as much as 70% of the total thrust;

It's also important to remeber that a turbofan creates an area of low pressure into which it is draw rather than just mushing air upon air.

The compressor stages do a great deal of pressure change.  That semi-laminate airflow over the power section will reduce engine noise significantly, though.

There were some facinating experiments with external blades on turbofan engines in a hybrid semi-turboprop configuration.  The fuel economy was good, but the sound signature from exposed supersonic blade tips was a detriment.

modelcrazy

Chad, turboprop. It uses the engine to drive a reduction gear for the prop. No thrust from the exhaust. About half  of turboprop engines use a centrifical flow engine the rest, axial flow like Don's

Actually not to disimilar to a turbofan on airlines, but the exhaust there is for thrust and the fan is for cooling, extra thrust and sound deadning.

 

The exhaust of a turboprop does provide some thrust, but typically less than 10% of the total. And the fan of a turbofan provides as much as 70% of the total thrust; it's not just for "cooling, extra thrust and sound deadenimg."

They are a very fuel efficient propulsion system. The prop (s) is/are the main propulsion, and there is some residual thrust.

Prime examples currently are the C-130 Hercules, P3 Orion and the T-34 Mentor.

Commercial aircraft- the various Embraer short and midrange aircraft.

Private civil- the Beech King Air.

The Douglas A2D Skyshark, following the A-1 Skyraider, was an Allison turboprop set up driving counter rotating props on a single axis.

That powerplant had 5,000 equivalent (prop plus thrust) shaft horsepower, compared to the 2,700 hp of the Skyraider's R3350 radial engine.

You are no doubt familiar with the Russian Tu-95 Bear bomber. It has enormous Kusnetsov turboprops driving counter rotating props and develops about 12,000 equivalent shaft hp each.

A good spotting feature in photos is the single very large exhaust port per engine. The primary spotting feature in real time is the incredible NOISE!

Power and eficiency make them excellent endurance powerplants for patrol aircraft.

Bill

Chad, turboprop. It uses the engine to drive a reduction gear for the prop. No thrust from the exhaust. About half  of turboprop engines use a centrifical flow engine the rest, axial flow like Don's

Actually not to disimilar to a turbofan on airlines, but the exhaust there is for thrust and the fan is for cooling, extra thrust and sound deadning.

I've never seen anything like this. It's propeller driven and uses jet propulsion?

armornut

   That is really cool Don,  I might have to add one to my stash....being an airplane machanic.

 

If you have a Hobby Lobby near you, they carry it, and with their weekly coupon it is quite cheap.

Mighty fine, Don.

Very cool Don!! This is a lot of fun to see come together. =] Hang in there.

Don this is great. I enjoy your engine builds. You do nice work for sure. 

T e d

Oh wow Don! Excelent!

I saw on of these at HL the other day and though about getting it, now I think I will.

   That is really cool Don,  I might have to add one to my stash....being an airplane machanic.

Got a lot done lately.  Fixed those two burner cans fine. The turbine section (interior, anyway), is finished and fastened to the compressor section.

Got a decent Alclad aluminum coating on the spinner and blades, so these are ready to install.

I am now putting all the bangles and beads (piping, wiring and small accessories) around the outside of the engine. Back half of compressor section went fairly well, but the compressor door was a nightmare.  Almost every piece had fit problems.  I trimmed some as best I could, even replaced some of the piping with some aluminum wire I had.

This is the view of the junk on the other side of the compressor case.  Next step is stuff on bottom.  After that I can assemble all the sections and make some new mounts (I think the kit mount is not up to the level of the rest of the kit.

Starting to work on a base, but had to cut some strips of oak today, and saw blade is just to worn out, so it will be tomorrow or Monday before I go out and buy a new one.

I made the shaft out of eigth inch styrene tubing.  Didn't need the bosses- they hold the turbine rotor from moving axially, but that is captured by the vanes. 

Have mounted the rotor in the turbine case now.

Also got the compressor mounted to firewall and intake section.

I had lost one of the fuel nozzles!  I used one of the others to make a mold from that RTV moldmaking putty.  Then, cast the nozzle with casting resin.

Bet you can't tell which is which.

Had another whoooops.  I had spilled a little bit of lacquer thinner on the bench.  While cleaning up I dropped a kleenex on the bench and it happened to land right on the wet spot.  A minute or two later I was picking up parts to get them out of the way, and I dropped the burner can assembly right in that wet Kleenex and didn't notice.  When I did, I found pieces of wet Kleenex stuck on a couple of cans, with steel color washed off others.  Not a big thing- sanded everything off with 1000 grit, and I'll touch up the next time I use the steel color.

Here are some progress photos.  Includes the black accessory section, the compressor section, the burner section and an unmounted burner can, the exterior casing of the turbine section, and the firewall and front of the turbine section.

Now I need some help.  I lost a part- the turbine coupling shaft!  I cannot find it, and have lost hope that if I leave it alone, it will come home wagging its tail behind it.

If anyone has the kit, could they make some measurements for me, so I can scratch the shaft?  I believe, from the holes it goes through, it is about 1/8 inch in diameter.  But I need to know the length.  And, it has three bosses along it- a rectangular one and two cylindrical ones.  I need to know the spacing along the shaft for these bosses, and their size.  Can anyone help?

These things, in particular the V8; were notorius for not really working. Look forward to seeing it done.

Yes, that scale Hercules will have a 13.2 foot wingspan.

That looks like a really fun build.

I first built this kit when I was 12 or so and always remembered it because of the variable pitch propellers. When I saw that Atlantis had reissued it I grabbed one and it's now sitting in front of me as I type this. Each section of the engine rotates as it should but combined I'm unable to get it to work so I probably needed to shave a bit more off the turbine blades. The only part that works flawlessly is the prop and reduction gears. Once you think you've got things fitting well take a little bit more off just to play it safe. I really like the color you chose for inside the engine. The instructions call for some sections to be orange and I only had some Tamiya orange. It looks just like the molded plastic before painting and I wish I hadn't used it. 

Well excelent Don.

Looking forward to another beauty Don engine

Looking great Don!  I think it's neat that we can build kits from yesteryear from fresh boxes!  That gloss aluminum looks fabulous.

Now build three more and add a C-130 Hercules to display them on.