26 September 2001 - Amsoil passes the test
I've now been using the Amsoil 0W30 synthetic oil for some time now so thought it was about time I reported on just how it has performed.
It flows far more freely when cold than the Mobil Trisynthetic 0W40 that I was using before (particularly important when spooling up in colder weather) and I've had no problems running the engine for prolonged periods at high power settings.
No wear has been detected either on the turbocharger journals or thrust bearing despite long, hard runs at over 120,000 RPMs with exhaust gas temperatures of more than 650 degrees C.
In short -- I'm sold -- it works as advertised and certainly appears to be superior to the Mobil 1 I was using before.
I can't imagine an oil being subjected to anything like this level of punishment in a car engine so the fact that it has worked so well in this application is truly amazing.
Anyone who knows me, knows that I'm the kind of guy that calls a spade a spade and if this oil wasn't any good I'd say so -- whether Amsoil had provided me with a free sample or not.
25 October 2000 - Construction of a
power-take-off assembly underway
24 October 2000 - My engine got a mention in PC World magazine
9 September 2000 -- Now There's a FAQ!
1 July 2000 -- Amsoil To The Rescue
The only one which took the time to reply was Amsoil, who not only offered some very valuable information on which of their oils might be best suited for use in my engine but were also happy to assist by giving me some free product to use.
Top mark Amsoil! A company that takes the time to respond to a customer's requests in this way deserves respect.
I am about to try out their 0W30 synthetic motor oil shortly and I'll post a full report on how it compares to the Mobil 1 0W40 I've been using recently.
23 May 2000 -- Got The Afterburner Going!
Check out the afterburner page
16 April 2000 -- Latest Runs
In this image you can see the fiber-optic pickup lead which picks up light reflected from the compressor turbine nut. I painted the nut half black and half white to provide the strongest possible signal. Even so, I had to build an extra stage of amplification into my tachometer circuit in order to get a nice reliable reading under overcast skies.
I installed the pickup by drilling a 3mm hole down the center out of a 5mm hex-socket head machine screw (to take the fiber) and then drilling and tapping the intake tube so that I could screw the machine screw into position.
In order to grip the fiber strongly I used the sleeve of a pop rivet which was a snug fit into the head of the screw. I lightly crimped the pop rivet sleeve around the fiber and this means it all hangs together very nicely -- but it's still very quick and easy to remove if necessary.
Boy... what a surprise -- the engine idles at 60,000 RPMs and this is the lowest sustainable speed. Even at this speed I have to be careful to keep the oil pressure at 30 PSI or below or it starts losing RPMs.
At idle the compressor is producing 5 PSI of pressure and the exhaust temp is around 650 degrees Celsius.
This is the control panel while the engine is running at 100,000 RPMs. The tachometer dial readings should be multiplied by 3,000 to get the actual RPMS -- hence it's indicating 33 here.
Note that the EGT is just 631 degrees C which is after revs stabilized. The oil pressure (on the left) is about 42 PSI. Compressor boost is around 10 PSI here (top right gauge).
Throttling up to 20 PSI of compressor pressure gives me about 135K RPMs (yes, 135,000 !!) and there's still plenty of throttle left (and it was altogether too loud -- even with hearing protection) to get close enough to get a good shot of the control panel.
Last weekend I did a couple of runs at more than 40 PSI of compressor pressure but that was before I had the tach connected. I guess it must have been spinning in excess of 160K RPMs -- I don't think I'll try it that fast again as I'm surprised it didn't fly to pieces. Besides, my tachometer (which is a 270 degree analog meter that was originally calibrated 0-50 MegaWatts -- so cool!) is presently calibrated to show 150K RPMS at full scale so I can't measure RPMs higher than that.
Now some bad news -- perhaps it was a legacy of those hi-power suicide runs but when I checked the magnetic trap I installed in the oil drain line last night I found a small fragment of steel that looks like a piece of a bearing shell.
Today the engine seemed a little harder to start and the oil pump has to spin faster to generate the same amount of pressure so I'm thinking that it won't be long before the bearing collapses completely.
9 April 2000 -- Good news -- my gas turbine runs!
Surprise, surprise -- after removing the camp-stove regulator on my propane tank which was severely restricting the gas-flow, the damned thing burst into life with only a few prods of the leaf blower.
I've created a 4MB AVI file using MPEG encoding, a 1MB Quicktime movie, and a 800K RealVideo file that you can download and view to see the first test run. Unfortunately the RealVideo server isn't working at the moment but when it is I'll put up some smaller streaming files.
During the video you'll see me turn on the oil pump and set the pressure (you'll hear the noisy motor grinding away) then I apply the leaf-blower
It surprised me just how much fuel was needed to even get an idle out of the engine so it takes several attempts to get the engine up to sustainable revs.
Once it's running I turn up the oil pressure to 40 PSI.
To prove it's not all done with smoke and mirrors, I drop a rag into the exhaust stream -- then have to go chase after it. The hot gasses blew it some 50 feet!
As I've realised in subsequent runs, during this first trial, the engine was running at little more than 1/4 throttle with just 10 PSI of compressor boost. If you listen carefully you'll hear the engine throttle up just a little before I turn it off and it spools down.
That noise you can hear once it stops is the oil pump still going.
In subsequent runs I've had the compressor boost pressure gauge pegged to the stop with over 40PSI -- now that's an experience, you can feel the noise in your body and it's still very loud even with industrial ear-muffs on.
Today I have a headache and my ears are still ringing :-(
Like so many others, I've based this engine on a regular car turbocharger unit (mine came out of Nissan) and simply linked the compressor output to the exhaust turbine input using a combustion chamber.
As you can see from the pictures on this page, it looks much the same as almost all the other DIY gas turbine engines that have been documented on the Web.
Since the the flame tube is one of the most important components in any gas turbine engine, I've included some images and description of my design which seems to work very well indeed.
I'll post some more pages detailing the other components as I get time over the next week or so.
Here are some static images of the engine before it was finished.