Recently picked up the Atlantis repop of the old Revell Allison turboprop engine. I love to build engine models, and this is a neat kit. While very old, so am I, so I figured I could handle a kit from about 1960. It has some flash but not that much. To get the compressor section, however, any rotor disks must be trimmed carefully or you will not be able to get the rotor into the compressor case.
I do not plan to operate the finished model, and felt the prop reduction gears were not that interesting, so didn’t add them. Here is the gearbox with the door glued in place and gaps filled, ready for finish paint (subsequently painted.)
The instruction color callouts are for a “exploded view” display, so I plan to find out as much as possible to finish it in more appropriate colors. I am planning on using a lot of Alclad.
Trying a new Alclad color call high gloss aluminum. I didn’t want a perfect mirror finish, but still shiny stainless steel color. Since I wanted a slight blue tinge to it, I tried it directly on the plastic. The blue base did not come through- this stuff is thicker than the other metallic colors and worked fine.
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.
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?
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.
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.
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.
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.
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.”
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.
