SJ10

The SJ10 uses a T03 turbo with a compressor inducer diameter of 1.70”, a scroll A/R = 0.42 and a turbine exducer diameter of 2.3”, and an A/R = 0.48.

SJ10November 1999

Dear Fellow Turbine Enthusiast,

One of the recent aircraft video documentaries has stated, “If the Wright Brothers first flight was aviation’s greatest milestone, then the advent of the jet engine [aircraft gas turbine] was certainly the second greatest milestone.” It is no doubt that the aircraft application has driven the development of the gas turbine. As an example, the cores of aircraft gas turbines have been used to power ships, large generators, pipeline compressors plus many other applications.

Gas turbines are amazing engines for the amount of power produced for their size, the amount of exhaust they put out, and the wonderful turbine sound. Gas turbines have been around for almost a century and have been flying for 70 years. However, it has taken this long to evolve a design for a small gas turbine that is inexpensive and can be fabricated by someone with average shop skills and operated safely by someone familiar with engines.

With the advent of the common application of turbochargers to many of the production automobiles and trucks, the price for turbomachinery parts has fallen. The gas turbine has at least six main components – a compressor, combustor, turbine (which drives the compressor), shaft, bearings, and housings. The turbocharger has five of the six, a compressor, turbine, shaft, bearings, and housings. The piston engine acts like a combustor by supplying hot gases. Somewhere, in years past, someone got the idea of replacing the piston engine with a combustor (like those developed for gas turbines) and using the turbocharger as an engine. Now here is an engine (which is based on a turbocharger) that does not have any complex aerodynamic blades to machine or weld, the balancing is already done, and the bearings and seals are already in place.

There were several additional design requirements which needed to be satisfied before a truly easy to build miniature engine could result. The first was to reduce as much as possible the need for high temperature steels. This was accomplished by mounting the plenum/combustor on the turbine scroll flange such that the hot combustion gases feed directly into the turbine. Therefore, only one fabricated part, which requires high temperature stainless steel, is the Combustion Liner (or Flame Tube). The material is available from a number of suppliers.

Another design requirement was to eliminate TIG welding since the majority of engine builders do not have access to TIG welding. The engine requires only silver soldering, soldering, and spot welding (on the combustor liner). Other “design” requirements were definition of the accessories required to support engine operation and definition of proper engine operation and safety procedures. These are outlined in detail in the plans set.

The SJ10 plans have 10 pages (8 ½ X 11) of instructions on how to fabricate the parts, assemble the engine and test setup, and operate the engine safely. In addition, there are 21 drawings (three are 11 X 17, rest are 8 ½ X 11) of such a quality to allow parts to be accurately reproduced. There are 5 pages in the Appendix which are a table of cutting dimensions for the Inlet (2 pages), a sample check list for engine running, plots of engine test data from the first run of the prototype engine, and a sheet of sources for engine materials and accessories. There are eleven photographs to clearly illustrate engine features. A sample drawing is shown below; the line quality is somewhat diminished due to the scanner.

Many people ask what the engine is used for. The prototype is used as a test stand engine to test new accessories, component design changes, and technology programs. These small engines can be used to test different thrust nozzle designs and to develop a drive turbine. It has been suggested that an engine with a drive turbine could be used to power a car, boat, motorcycle, bicycle, go-cart, lawn mower, garden tractor, leaf blower, heat source to melt snow/ice, etc., etc. It could also be used as a gas generator for an afterburner.

With the plans, the average engine builder has access to the knowledge to successfully and safely build and run a miniature gas turbine engine.

If you have any questions, contact SJET and I will answer your questions. I have had 46 years of experience with AlliedSignal (Garrett/AiResearch) and with DIY Turbocharger Engines designing and developing new turbines (which means I still have a lot to learn).

Sincerely,

 

Michael L. Early
Sjet, Inc.
8642 S. Kenwood Lane
Tempe, AZ 85284
Tel: 480-838-2588
Email: sjet@cox.net


 

VIDEO OF SECOND ENGINE RUN

Second Engine Test

This was taken in 1999; notice I was 130 pounds heavier. The guy with the yellow ear protectors is Don Palmer – he did the aero design of all of Garrett’s centrifugal compressors (look for the backward curved blades).

PLANS ARE AVAILABLE FOR $50US PLUS POSTAGE

The section below is the write up that goes with the drawings. After the plans and postage are paid for (either cash or check), then the drawings will be sent.

The plans are $50US plus $10 for shipping and handling in the U.S. and $20US for foreign shipping.

I do include support with the plans.

SJET Inc.
Michael Early, Pres.
8642 S. Kenwood Lane
Tempe, AZ 85284-2573

Revised Inlet

I have had some comments that the Inlet was difficult to fabricate, I agree. Therefore, I have designed another which is just a sheet metal truncated cone, similar to the one shown on the latest pictures of the SJ20. Those that have bought just request the new drawings (2).

 

PLANS WRITE UP

SJ10 Gas Turbine Engine Plans
(Copyright 1999, Scaled Jet Engine Technologies, Inc.)

 

1.0 METHODS OF FABRICATION, DRAWING NOTES

The methods of fabrication presented in these plans should not be considered as the only method or as always the best method. They were basically the methods used to construct the prototype engine. All instructions and drawings should be read and studied carefully before beginning fabrication of the engine. If you doubt your ability to construct and operate the engine safely, then do not build the engine.

The drawings are made and dimensioned to facilitate the fabrication of the parts and do not necessarily conform to ANSI standards in all cases. If there is any question on the drawings or any aspect of this engine design or operation, please contact SJET, Inc.

This engine is NOT A TOY! The engine should not be operated by children or if children are in the area.


2.0 TURBOCHARGER MODIFICATIONS

The modifications and parts shown in these plans are for one turbocharger model only. The turbo model is a Garrett (also AiResearch) TB 0335, part number 466298-7. ATTEMPTS TO USE OTHER MODELS/BRANDS COULD RESULT IN AN ENGINE THAT WON’T RUN PROPERLY AND MAY BE DANGEROUS. ALL TURBOS ARE NOT THE SAME!

If a turbo is obtained which has been rebuilt, it is ready to begin modifications. If a used turbo has been obtained, it should be cleaned and inspected. All wastegate parts may be discarded. The rotor should turn freely and feel tight in the bearings. The compressor and turbine should be inspected with a magnifying glass for nicks or cracks. If cracks are found, the part should be discarded. Rotating parts with nicks should be sent to an overhaul shop for disposition. If there is evidence of a rub between the compressor and shroud (stationary cover over the compressor wheel) or the turbine and shroud, the turbo should be sent to an overhaul shop for an overhaul. The turbine scroll should be inspected for cracks, particularly around the shroud area. The scroll should be discarded if there is a crack through the shroud area. Cracks may or may not be okay in the wastegate bypass hole area. If there are any questions, consult a turbo rebuilder. The bearings should be replaced and the rotor balanced if necessary.

There is a bolt circle on the compressor scroll (cast aluminum) with six 13 mm (head size) bolts. When these are loosened, the scroll can be rotated; the bolts will have to be removed to remove the scroll to machine the seat for the tach sensor housing (see drawing 10.1 and figure 2.1). There is another bolt circle of four 10 mm (head size) bolts. These should not be loosened; they are for disassembly during overhaul. Also (very important) do not loosen the shaft nut holding the compressor on the shaft. There is another bolt circle on the turbine scroll (cast iron) with six 13 mm (head size) bolts. When these are loosened, the scroll can be rotated; the bolts will have to be removed to remove the scroll for grinding the 2.5" diameter circle in the flange (see drawing 10.2 and figure 2.2). Of course, do not do any machining on the scrolls when they are bolted to the turbocharger. In addition, make sure that all burrs have been removed and the parts are clean when ready to re-install. Inspect also to make sure that no foreign objects are in the turbo or the scrolls. Re-install the scrolls, snug the bolts but do not fully tighten them.

 

Figure 2.1  Compressor scroll machined for
tach sensor housing

Figure 2.2  Turbine Scroll showing 2.5” diameter passage

 

3.0 INLET

The Inlet shown in figure 3.1 and drawing 10.4 was fabricated first as a turning on a manual lathe using a “method of increments” to cut the inside and outside one-quarter ellipses. The method of increments involves making a cut, moving a few thousandths in the X-direction, and making a new cut in the Y-direction. This is repeated over and over until the entire curved surface has been cut. The surface then has small steps (several thousandths) over the surface. The surface is blued and emery cloth is used to smooth the surface until the blue has been removed. For appearance sake, the inlet was polished while mounted on the lathe.

The general equation of an ellipse is AX2 + CY2 + DX + EY + F = 0. Using this general equation in a spreadsheet, the increments can be calculated in a few minutes. The specific spreadsheet output used to generate the cuts for the prototype inlet is included in the appendix.

When the Inlet was taken off the lathe, the flange was round. The Inlet was then mounted upside down on a small CNC mill (Maxnc) and the outline of the flange cut and the holes drilled. This also could be done several other ways such as: a manual mill with a rotary table, or carefully bandsaw then smooth the shape of the flange. It could also be left round.

 

Figure 3.1  Inlet compressor scroll

The Inlet shown is approximately three inches long; aerodynamically it could be much shorter. However, at the present length, it could possibly prevent the fingers (of the average hand) from being cut off if sucked into the inlet while the engine is running at high speed (or any speed). If a hand is put in front of the Inlet while the engine is running, the hand can be sucked into the engine in a matter of milliseconds. The strength of the suction is much greater than any shopvac and can pull in loose rags and papers from several feet away. Make sure there are no loose objects (large or even very small) within several feet of the inlet. Make sure that all wires and instrumentation lines are fastened down. Do not shorten the inlet and keep bystanders away from the engine while running.


4.0 COMBUSTOR PLENUM FABRICATION

The Combustor Plenum is made from a Coleman propane gas cylinder. All of the gas should be used out of the cylinder. Then, in an outdoor area free of any ignition source, use the Valve Removal Tool (see drawing 10.5) to remove both valves and blow compressed air through one opening to clear out any traces of the gas. Mark a straight line around the cylinder to cut off the bottom of the cylinder. A piece of paper wrapped around the cylinder can be used as a straight edge to mark the line. The bottom can be cut off using a bandsaw with a fine toothed blade. Drill out the vent hole with a drill large enough to clear away the protuberance on the inside. Referring to drawing 10.6, mark the cut line to remove the top at the required dimension and make the cut. Deburr all edges. Remove the paint from the outside of the cylinder and top.

Cut four 3/8-16 studs 1.20” long and screw into the Plenum Base just far enough that they don’t interfere with the cylinder. The cylinder is set in the groove and silver soldered (solder must have a rated melting temperature of ~1200F) to the Plenum Flange and the Plenum Base with studs. Make sure that the offset stud is soldered on top of the base to prevent turning. Mark the location of the sparkplug hole and drill. If a plenum pressure gauge will be used, prepare an 1/8” copper tube fitting and silver solder it ~1.5” above the bottom of the base. After it is soldered in place, drill a .063 hole through the cylinder wall.

Figure 4.1  Compressor discharge elbow

 

A 2.0” OD pipe 1.1” long is cut and soldered (minimum ~400F melting point solder) to a 1 5/8” copper pipe 45 degree elbow. It is soldered with the elbow tilted in 2” pipe (see figure 4.1). Make sure that the 1 5/8” OD portion of the elbow is the end sticking out of the 2” pipe. Cut a 2.0” length of 2.0” ID radiator hose and lightly clamp the elbow assembly to the outlet of the compressor scroll.

Silver solder the Plenum Top to the Plenum Flange. Temporarily mount the plenum assembly on the turbine scroll. Adjust the relative position of the elbow assembly and the plenum such that when the 1 ½” diameter sink trap (actually 1 5/8” diameter on the end) is cut to length and placed on top of the plenum assembly, the two outlets will line up. A hole is cut in the center of the Plenum Top and the sink trap silver soldered in place. Care must be exercised that the sink trap is soldered to the top such that the air enters straight down into the plenum. The hole where the vent valve in the gas cylinder was located is also soldered shut; it may take a small piece of sheet metal to cover the hole. Then use the solder to cover and seal it.

The Plenum Top is mounted upside down on the mill and the mill centered on the center of the flange. A 3/16” end mill is used to drill the fuel line hole in the air inlet “sink trap”. A 3/16” line union fitting is drilled through with a 3/16” drill and one end of the fitting cut at an angle to fit the curve of the “trap” at that point (see figure 4.2). In order to hold the fitting in place over the hole in the sink trap, a fixture is made. The fixture is a 1 X 5 X 1/8 steel strap with a 3/16 hole in the center and .166 holes 2.25” from the center hole; this strap is then bolted to the plenum flange. A 10-32 threaded rod is bolted through the strap, the hole in the trap, and the fitting to hold it in place while it is soldered to the trap.

The plenum and top should be painted with a heat resistant aluminum spray paint. The plenum is now complete.

 

Figure 4.2  Fuel fitting cut at an angle and soldered
to sink trap

 

 

5.0 COMBUSTOR LINER AND TOP

 

Fabricate the tools shown in drawings 10.12.1, 10.12.2, and 10.11. Cut a 4.5” length of .375 drill rod and thread both ends for a length of .75”. This rod will be used to bolt together tools 10.12 and the liner top. Cut out a disk of sheet metal for the top to the diameter called out in drawing 10.13. For deburring sheet metal (and any other metal) and smoothing out any jagged lines, a deburring wheel (Scotch-Brite or Bear-Tex) mounted on a grinder can’t be beat. Drill the center hole slightly undersize and ream to size. Mount the sheet metal disk in tool 10.12 and mount tool 10.11 in the lathe toolpost. With the lathe running at a fairly low speed bring the bearing on tool 10.11 against the disk and follow the contours of tool 10.12.1 around to form the liner top. Next, mark and drill or punch the four small holes around the edge and use an end mill to cut the four partial holes at the edge of the center hole. These are used to direct cooling air on the fuel nozzle.

 

Make a copy of drawing 10.8 (Combustor Liner), cut out the pattern, and glue it to the sheet metal with rubber cement. Do not use any other type of glue as nearly all will wrinkle or shrink the pattern and/or be very difficult to remove. Cut out the pattern and deburr with the deburring wheel described above. The slots at the bottom were cut with a fine tooth blade on a bandsaw. Punch the holes or drill with a sheet metal drill such as a Unibit drill. Roll the liner into a cone. Put the liner into position in the plenum base, push on the edges to minimize the overlap, and mark the overlap. Do the same thing with the liner top. Spot weld (or TIG) the edges of the liner together. Next, put a close fitting rod (an ice pick was used) through each of the sixth row holes and push the rod up (toward the liner top) forming the hole into a scoop (see figure 5.1).

 

Fabricate the sparkplug standoff as shown in drawing 10.9. Make two copies of the drawing and cut out two patterns for the fixture. Rubber cement the patterns to the sheet metal, cut out, and deburr. The ends should be spot welded or soldered together with the center spread enough to get an 8-32 screw through. The 8-32 screw should be assembled with a washer, fixture, combustor liner (through the sparkplug hole), standoff, washer, and nut; this will hold the standoff in the proper position while silver soldering it to the liner. Do not use larger sparkplugs as this would block some of the cooling holes and may result in a failure.

 

Cut out two sheet metal standoffs (see drawing 10.8) using the method described previously (copies and rubber cement). Spot weld (or TIG) them approximately 120 degrees from the sparkplug at approximately the same height. Bend as shown in figure 5.2 such that with the liner and the sparkplug installed in the plenum, the sheet metal standoffs rub against the plenum and keep the liner centered in the plenum.

 

Put the top in place and mark the position of four corresponding .063” holes on the liner. Drill the holes and replace the top. To hold the top in place, put small pieces of stainless steel safety wire through the holes and twist the wire tightly as shown in figure 5.3.

 

The combustor liner assembly is now complete.

Figure 5.1 Rod shown forming 6th Row holes

Figure 5.2  Shape of sheet metal standoff

5.3 Safety wire twisted

 


6.0 OIL OUTLET FLANGE

The end of a ¾” NPT x ½” compression sleeve fitting is turned down until it just fits inside the large hole in the flange and is soldered in place. See figure 6.1. Make sure that nothing sticks through to the flat side of the flange.


7.0 ASSEMBLY

Install the Inlet and put flat and split lock washers under the bolt heads. Install the Exhaust Flange and Rear Engine Mount using stainless steel bolts and flat and split lock washers.

Install a 1/8” NPT in the oil inlet port in the center section. Set the turbine scroll flange horizontal, entry passage facing up, and move the center section around until the oil inlet port is straight up. Tighten the six 13 mm turbine scroll bolts.

Set the Plenum Base and Gasket on the turbine scroll flange. Looking from inside the plenum, make sure that the gasket is centered on the turbine opening. Install stainless steel flat and split lock washers and nuts and tighten the plenum to the turbine scroll flange.

Refer to drawing 10.16. Put the Combustor Liner inside the plenum and install the sparkplug. Put the Fuel Nozzle through the fitting on the sink trap and set it such that it sticks inside the Liner Top by ~0.75”. Fabricate a 1/32” thick gasket to fit between the two Plenum Flanges. Install the Plenum Top and plenum flange gasket with 8-32 x ½” allen head screws with flat and split lock washers.

 


Figure 6.1 Oil return fitting

Cut an approximate 6” length of 1 5/8” ID radiator hose and install between the sink trap and the elbow. Tighten the hose clamps. Fabricate the two front engine mounts and install them on the two compressor scroll bolts that are approximately horizontal; the engine mounts should hold the engine horizontal and the plenum upright. Tighten the six 13 mm bolts on the compressor scroll.

Install the tach sensor in the Tach Sensor Housing and use a small amount of RTV Silicone Rubber on the outside to retain the sensor in the housing. Install the housing to the compressor scroll using 6-32 x 5/8” allen head screws with flat and split lock washers.

The Oil Outlet Flange and gasket should be mounted with two 8 x 1.25M bolts, 25mm long, with flat and split lock washers.

Check all bolts and clamps for tightness.

 

8.0 INSTRUMENTATION

One of the things that distinguishes a gas turbine from a piston engine is the gas turbine’s natural ability to self-destruct. As the throttle (or fuel) is increased on a piston engine, decreasing volumetric efficiency and increasing fuel-air ratios provide limits to prevent the RPM’s from going beyond a certain point. However, when the fuel is increased on a gas turbine, the engine becomes more efficient and the RPM’s and maximum temperature increase even further. This goes on until the rotating parts burst and/or parts in the hot gas stream melt and fly out the exhaust. In order to prevent this from happening, a tachometer is required to measure RPM and an Exhaust Gas Temperature (EGT) gauge is required to measure exhaust gas temperature. The limits for measured parameters are given in the test plan.

Providing oil at the proper pressure and temperature is essential to keep the engine operating properly and to prevent failures. Automotive gauges are adequate for this instrumentation.

A plenum pressure gauge is useful, but not required. When the pressure fluctuates, it indicates that the compressor has gone through surge. This is usually benign, but it is worthwhile to check the condition of the rotor and bearings and for any obstructions in the inlet or exhaust of the engine after the engine is shut down.

 

9.0 ASSEMBLING TEST SETUP

The engine needs to be mounted solidly. The prototype engine is mounted on a metal service cart. The Rear Mount is shown in drawing 10.20 and the front mounts are described in paragraph 7.0. Please note that source and part numbers for the prototype lubrication system components, accessories, and some engine materials are listed in the appendix. These recommendations are the ones tested on the prototype. SJET, Inc. is continually testing other components and will add them to the list after successful testing.

Figure 9.1  Prototype engine test setup prior to first engine test

 

9.1 LUBE SYSTEM

The oil pump is assembled into the housing (drawing 10.19 if using the Honda pump) and the housing and an electric motor (1/4 HP or larger) can be mounted to a 5” wide aluminum channel 14” long. A toothed belt can be used to drive the pump since it comes with a toothed pulley already installed. A switch should be installed in the electrical line and mounted on the instrument panel. A valve should be installed between the inlet and outlet, either a pressure relief valve set for the proper pressure limits or a simple adjustable valve (see Oil System Schematic, drawing 10.21).

Later testing has shown that a Shurflo 12V pump used with an off/on toggle switch and a PWM (Pulse Width Modulating) circuit for speed control to be a more efficient and slightly lower cost method for providing pressurized oil.

The oil lines should be hooked up as shown in drawing 10.21. It is helpful to install a short length of ½” tubing on the oil outlet fitting and clamp a length of ½” ID clear plastic tubing to it. The other end of the clear tubing is fastened to the oil tank return. The clear tubing allows confirmation of oil flow through the turbo bearings. An oil filter is required to protect the bearings from the possibility of wear from foreign material. The recommended oil cooler is high efficiency and is presently being used without cooling fans. With several runs of 15 to 20 minutes each and an ambient temperature of 90F, the oil temperature only reached 170F. If in any installation the oil temperature climbs higher, a fan may be needed on the oil cooler.



The oil pump is assembled into the housing (drawing 10.19 if using the Honda pump) and the housing and an electric motor (1/4 HP or larger) can be mounted to a 5” wide aluminum channel 14” long. A toothed belt can be used to drive the pump since it comes with a toothed pulley already installed. A switch should be installed in the electrical line and mounted on the instrument panel. A valve should be installed between the inlet and outlet, either a pressure relief valve set for the proper pressure limits or a simple adjustable valve (see Oil System Schematic, drawing 10.21).

Later testing has shown that a Shurflo 12V pump used with an off/on toggle switch and a PWM (Pulse Width Modulating) circuit for speed control to be a more efficient and slightly lower cost method for providing pressurized oil.

The oil lines should be hooked up as shown in drawing 10.21. It is helpful to install a short length of ½” tubing on the oil outlet fitting and clamp a length of ½” ID clear plastic tubing to it. The other end of the clear tubing is fastened to the oil tank return. The clear tubing allows confirmation of oil flow through the turbo bearings. An oil filter is required to protect the bearings from the possibility of wear from foreign material. The recommended oil cooler is high efficiency and is presently being used without cooling fans. With several runs of 15 to 20 minutes each and an ambient temperature of 90F, the oil temperature only reached 170F. If in any installation the oil temperature climbs higher, a fan may be needed on the oil cooler.


9.2 FUEL SYSTEM

The recommended fuel is propane; care should be taken to make sure that the propane bottle is not placed within an angle of ~20 degrees of either side of the plane of rotation. The newer 20 pound propane bottles have a built in flow limiter which may only allow enough fuel to get to idle.


The above pictures show the propane tank that I use.

After fabrication of the fuel nozzle, it should be flowed with either water or air to make sure that there are no obstructions.

 

9.3 IGNITION SYSTEM

Let me explain something about spark systems. A normal IC engine has a compression ratio from 8 to 14. That means that the dielectric constant of the fuel air mixture around the plug is very high. Which means that it takes lots of voltage and a small gap to get the spark to jump from the center electrode to the arm. When the fuel air ratio is atmospheric then it doesn't take much voltage to jump across a wide gap (my coil enclosure is 1 x 1.5 x 1.5). On that plug the spark jumps from the center electrode to the sparkplug rim.

One ignition unit that has been used was a special C&H unit set up for continuous spark, although almost any unit that produces a continuous spark can be used. The prototype engine tested an ignition unit consisting of a GM distributor, a motor to drive the distributor, and a coil. This also produced satisfactory ignition.

The pictures shown below are of the new, smaller combustion system not included in the plans, but it shows the plug and current ignition system being used.


This is the present ignition system that I’m using on the engine. As you can see the coil and point system are very small - they don’t need to be large. Since the coil is 6V, I am using “C” cell batteries to power it. I found this set up at a miniature engineering show. However, these are no longer available and so I am putting together the system from Bill Hinote using a Bosch relay. Once I have completed one and run it, I will make the circuit available and possibly a few units for purchase if there is interest.


The first ignition unit that I ran the engine with was one I built and it didn’t cost me anything. It was made from a GM distributor and a small 12V motor - both came out of the scrap box. Not thinking things through, I reasoned that I should put a lot of spark into the combustor, so I bought a big hot rod coil (you can see the big yellow coil in the first run pictures). When I tested it, I set it on the tailgate of my pickup truck and hooked it up. When I turned it on, I touched the side of the truck and got knocked flat on my fanny. Boy, did that hurt. But when I hooked it up to the engine, and being careful not to touch the cart, and worked great starting the engine.

You can decide what best fits your needs. Actually all you need is a method of opening and closing the points and hooking it to a coil and sparkplug.

The recommended instrumentation should be hooked up and mounted in an instrument panel. Make sure the operator is not in the plane of rotation of the turbine and compressor.

The air for starting is provided by a leaf blower or a large shopvac with the end manually inserted into the Inlet forming a loose seal. Other starting systems will be tested in the future.

10.0 TEST CHECKLIST

A sample checklist for engine starting is included in the appendix. This list should be reviewed and modified as necessary for applicability to your test setup. Be sure to review and be familiar with the engine limits and safety procedures. You should not run the engine without another person present and designated as the safety officer (someone familiar with the safety requirements).

An oil pump test should be done. Check to make sure that all fittings and lines are tight. The recommended oil is Mobil 1, 0W-30 or 5W-30; fill and check oil level. It should be between one-half and two-thirds full. Turn on oil pump and check for leaks, check oil pressure and set if necessary, and check for oil flow through clear plastic oil return line. Turn off oil pump, check oil level and add if necessary. Note the prototype system held nearly a quart in the lines, oil cooler, and oil filter.

Turn on ignition and listen for buzz inside plenum. Turn off ignition.

Turn on oil pump and tach. Turn blower on low and note engine RPM’s; switch to high blower and note RPM’s. On high, the RPM’s should be in the 5 to 10,000 rpm range for easy starts. Turn off leaf blower. During prototype engine testing, a variac was used to vary the voltage to the leaf blower to vary the rpm and airflow.

11.0 RUNNING THE ENGINE

Upon completion of the pre-test checks, you are ready to begin the checklist for the first engine run. Make sure all fuel lines are tight. At the point in the checklist when the engine begins to spool up, turn on the fuel slowly at the instrument panel, listen for ignition, and increase the fuel flow while watching the EGT and RPM’s. Continue the checklist and take data as desired.

 

12.0 THE FUTURE

Future projects in the works at SJET include lower cost accessories, extended capability of the SJ10, and new engines. Lower cost accessories include a new compressed air start system to do away with the leaf blower, a home made tach, and a lower cost oil pump.

Some of the possible projects to extend the capability of the engine are a recommended thrust nozzle, a redesign of the center section for ball bearings, a free turbine for shaft power, and modified accessories and designs to ease the starting and operation of the engine.

Engine improvements and new designs are in the planing stage and will depend greatly on what you the customer want. Please communicate what products you would like to see in the future. News regarding the SJ10 engine and accessories will be posted on the future SJET web site at www.diyturbinejet.com. Present email address is sjet@cox.net

 

 


Legal Notice

All high speed rotating machinery is inherently dangerous. Scaled Jet Engine Technologies, Inc. assumes no responsibility of any kind, in any way, for any reason, for injuries and/or damages which may occur physically to persons or property, intellectually, financially or any other form or type of damage, for any reason. Scaled Jet Engine Technologies, Inc. issues no warranty of any kind for any reason concerning this publication’s suitability for any purpose or for the accuracy of the information referred to herein.

This publication is for entertainment purposes only and is the sole property of Scaled Jet Engine Technologies, Inc. The information presented is copyright protected and is not to be reproduced in any way except as designated herein for personal use

 


APPENDIX

 

SAMPLE CHECK LIST FOR SJ10 ENGINE RUN --

__Set up video camera and focus on instrument panel (optional)
__Take still pictures of set up (optional)
__Record ambient temperature
__Check oil level
__Both propane valves off
__All switches off
__Designate safety officer and get out fire extinguishers
__Hook up propane bottle
__Check fuel and oil lines for leaks
__Hook up any extension cords required
__Hook up electrical for leaf blower, oil pump, ignition
__Turn on video camera
__Tank propane valve on
__Turn on oil pump, oil temp, ignition, EGT temperature display, tach
__Set blower at low speed, insert blower nozzle into inlet and turn on
__Turn on propane until ignition
__Increase blower and propane (monitor RPM’s and EGT)
__At 50K remove blower
__Turn off ignition
__Establish idle speed (~60K rpm)
__Set one minute at each data point (every 5 to 10,000 rpm)
__Record data
__Come back to idle for one minute
__Shut down, all switches off, use forced air to cool engine, inspect

-- LIMITS --
RPM = 145,000 Max
EGT = 1450F Max
Oil pressure = 25 psi Min, 60 psi Max
Oil temperature = 250F Max
-- SAFETY PLAN --
__Ear protection for everyone
__No one to stand in plane of rotation or in line with turbine exit
__One person designated as safety officer with two fire extinguishers
__Bystanders to stay back at least 15’


SOURCES FOR ACCESSORIES AND ENGINE MATERIALS



*Costs are approximate only. Cost does not include shipping & handling or sales tax. Costs are for reference only and subject to change without notice.

 

PICTURES

Below are some of the pictures taken during building:

SJ10