Been a while - new project, T04 Gas Turbine.

[Johansson]

Ok. The downside with a separate oil container is that it takes more space, and if one don´t check the oil level regularly the bearings can run dry.

About the combustion chamber, will you use straight vapour sticks with propane preheat or do you intend to do it any other way? Just curious...

//Anders

[multispool]

Hi Ash,

I don't participate in the forum much anymore but have been following your thread with some interest! Very nice work, hope you will have success!

The code to pulse small quantities of fuel would be only for the bearings - to keep them lubed and help bring the temps down, although, this will also mean small quantities of fuel will also be delivered to the primary fuel ring to the combustor, which isn't so desirable.

If I may offer some guidance here!
The best way to bring the temps down after shutdown will be to pulse the Starter to keep an airflow through the engine to cool it until a predetermined low temperature is reached (typically 100c). This will limit heat-soak to the rear bearing and ensure that the shaft doesn't warp by uneven cooling. I would suggest that this is even more important with a radial inflow turbine because of its greater mass.

But I figure that while the engine is still hot after shutdown and continuing to drive the rotating group will just vaporize off the small amounts of kero/oil that are injected into the combustion chamber so as not to have a runaway condition from pooled fuel in the CC lighting off at next startup. I'll probably also incorporate a drain plug in the main body to prevent this condition from occuring, if it does.

Its unlikely that the fuel will evaporate and will pool in the case (as you say). Runaway on a later start won't happen, what will happen is a wet start will be more than likely. As the air velocity in the case increases, it will whip up the kero pool and produce flames and fluffing sound much like a soft pulse-jet sound with a lot of heat. In fact, if anything, I would suggest doing exactly the opposite, like momentarily reversing the fuel pump direction on shut-down to ensure no fuel reaches the burner or case un-vaporised...

[Ash Powers]

So you are suggesting to entirely stop all fluid flow to the engine after shutdown and just rely on airflow to cool the parts down? I presume with the lower RPMs that the starter motor drives the engine at the bearings will be fine with the amount of latent lube still in them? If so, that makes things even easier. :lol:

[multispool]

Yes, assuming you are using ball races then they will stay wet enough until the next start. The only time I have experienced dry bearings is when somthing was wrong with the fuel system and stayed too long on the gas pre-start.

[Ash Powers]

Yes, assuming you are using ball races then they will stay wet enough until the next start. The only time I have experienced dry bearings is when somthing was wrong with the fuel system and stayed too long on the gas pre-start.

Yes, I will be using full-compliment angular contact ceramic bearings for this engine. Thanks for the advice!

[Fricke]

Nice work!

//Fredrik

[Ash Powers]

To make the compressor inlet shroud, I cut the mandrel from wood on the lathe to a guess-shape. A 0.065" thick aluminum disc was cut from sheet and annealed to soften it up for spining, and mounted into the lathe. It took a good bit of time to work the metal considering I was just using the butt-end of a hammer's wooden handle, frequently dipped in some Mobil1 10W30 to keep things rubbing smoothly. For the first try, I'm happy with the results - it isn't perfect - as I spun more towards the end, the metal was getting thin and it split in one spot. It is just a hairline fracture about 3/16" long and not even noticeable unless you closely inspect it, and you can see some non-uniformity in the thickness as bands around the part. I'll probably spin another part at a later time but this one will work for now.... there are still many more critical components to be made.









I've also spent several hours getting the PDA to DAQ connection going. Had a problem with the IOGear BT-RS232 wireless adapter as it demands on using handshaking while the DAQ device does not have handshaking. I contacted IOGear to see if I could get their engineers to write new firmware for the device that would allow the user to toggle handshaking on or off, but they apparently had better things to do than support a paying customer, so, *#$@ you IOGEAR! (explicatory statement about IOGEAR goes there). So, I ended up having to make a small adapter cable (seen with the white and black wires) to loop the RTS and CTS line around on the bluetooth serial port to make it send and recieve data as it is put on the IO lines.

I found a new development software package called HB++ (Handheld Basic) as a fully operational demo version for FREE. It has a silly splash screen at startup of your application but other than that, the program is fully functional. I started in on creating the forms and getting the bluetooth communication routines working and have been successful in establishing a connection with the DAQ, sending commands, recieving analog and digital input data as well as toggle the digital IO.

Right now, most of the forms just sit there and have no functions assigned to them with the exception of the main form, which is used to connect to the bluetooth and DAQ device. The rest of the code will be written over the next few days and I'll post some screenshots of it once it is completed.

[thecheat]

WOW

you're doing one heck of a job on this! That's a VERY pretty engine you've got going! I can't wait to see how it's going to run!

I check on this thread so often just to see if new pictures are posted... every one intrigues me. love seeing how these are built, especially by those who know what they're doing!

[Ash Powers]

Compressor diffuser assembly is finished. I found some suitable SS counter-sunk hex head screws and loaded them into the lathe to turn down the threaded section through the middle to reduce turbulence created by the diffusing gases having to ride a "speed bump". The bolts turned out to my satisfaction and I proceeded to drill and tap the diffuser cover and diffuser plate.









The bolts are countersunk to allow the compressor inlet duct to sit flush with the diffuser cover.



I also spent some time working up a plan to interface the fuel and oil feed tubes to the compressor diffuser plate. I ordered some 1/8" silicone orings from McMaster-Carr and machined out some components from aluminum. I also recieved the 1/8" stainless tubing and cut a short piece to test the idea with. The seal bulkead is cut with a seat for the oring which is about 0.020" shallower than the thickness of the oring. The oring drops into the seat and the bulkhead is fastened to the plate which is drilled out with a 1/8" bit for the pipe to feed through. With the bolts slightly loose, the tube slides right into position and upon tightening the fasteners, the oring is compressed enough to provide a really good grip and seal on the tube. This should make for easy disassembly/servicing/replacement of the fuel/oil feed systems and not require any welding or brazing to the fittings.







I also recieved the 0.012" stainless sheet to buld the combustion chamber from and started on that. I had to build a spot-welder to assemble the component and it went pretty well but this was just a test part. The seam is a bit rough and I need to make a mandrel for crimping the edge of the sheet for an overlap seam as well as either build or buy a sheet metal roller. Here's the pics though >>

[Johansson]

I keep repeating myself, but that is one nice looking engine!

About the casting, what method did you use to cast the aluminum parts? I saw a wooden pattern on one picture so I am guessing that you used sand casting and not some kind of lost wax method.

I am asking because I will soon try to make castings in my fathers forge so I can make the gearbox for the bike among other things without having to pay $$$ for a solid chunk of aluminum...

//Anders

[Ash Powers]

The very first casting I produced after building my refractory/furnace was an investment casting, but that is a stretch - it was just a piece of styrofoam cut out in the shape of a "Z", about 2" X 2" X 3/4" with two styrofoam gates - buried it in some silica sand and poured the metal. The part came out but as you can imagine, styrofoam and silica sand leaves a lot to be desired in the finish department.

Here's the refractory:


Complete image gallery for the refractory build here:
http://ashspecz.com/Image%20Gallery/Ref ... /index.htm

And my first casting :D


For everything else I've cast, I've just made wooden patterns. In one case, I modified an original part and used that as the pattern. I also use a product called "Petrobond" as my mold making medium. It is an oil-bonded fine silica sand that produces castings with pretty decent finish.

Here's the rig: (an old big-screen TV base was converted into my "sandbox" - I call it "The MAGNABox", affectionately. :-)



New housing to produce an electric water pump for my Nissan Z.

Original pump disassembled:



Modified housing:












Endtank castings for intercoolers for the Z.




Radiator endtank patterns built from 3" PVC pipe, acrylic sheet, bondo, etc..






Engine Mounts for the Z:








You can make patterns out of just about anything. Just pat the pattern down with some parting dust, ram up your mold, and pour your metal.

If your father has a forge, that's a different animal compared to casting. A forge uses steel dies that form the "mold" and the forge literally "presses" the metal into shape rather than pouring liquid metal into a mold. Forgings are notably stronger given the higher grain density you get from compacting the metal into shape, but require quite expensive machining to produce the dies. Forging and casting are two different processes but for your application, casting the components for the gearbox shouldn't be an issue. Just overbuild the components and you'll be OK.

[Johansson]

Oops, my bad. When I wrote forge I meant a blacksmith forge, which has a coal burning furnace in it. With English as the second language it is hard to find the right words sometimes...

Really nice finish to the parts, but how do you use the original pattern to make the water pump housing? I have read a book about sand casting but it didn´t say anything about how to use complex patters.

Sorry if I am clogging your project thread by the way, we can take this discussion in PM if you want to.

//Anders

[Ash Powers]

The original water pump housing was created with a 2-piece mold as the part has enough draft in it along its center axis. You can see in one of the images that I added after the original posting how the mold is made. It is just an upper half and a lower half that forms the void that the liquid metal fills when poured into the gate.

I'm not sure if your father has the equipment necessary for casting alumiunum though - you need a refractory/furnace similar to what I built to melt the aluminum as well as the mold flask and molding sand.

Here's a cheesy video I took of pouring one of the endtanks - you can get a feel for that step of the process...

http://ashspecz.com/Image%20Gallery/200 ... IM0562.mpg

[Johansson]

I will try to buy a couple of buckets of oil sand from somewhere, and the flask is quite easy to build so I will hopefully be able to do some simple castings later this vinter. Thanks for the pics and video!

//Anders

[Irvine.J]

G'day Johansson,
As you might have seen i'm just putting the final touches on my brazier to melt down some aluminium whilst waiting for the metal place to open next week. However, i'm having trouble with my burner and was hoping you could help me. I seem to get a whopping great flame without a regulator but its not controlled like yours. It does melt it without one after an hour or so, but i'm trying to make it a quicker and easier process.

Just wondering the following.
Is there a regulator on your gas tank, if so is it a standard low pressure one?

I noticed the cover to let in the desired amount of air, but is it just 1 very small hole the gas is coming out of?

How long should the burner tube be, it looks like a simple tube.

Thanks for your help mate.