Jet Kart

I decided it was time to put the thrust and power of the HR-1 engine to some good use, and have a bit of fun at the same time.

My daughter had enjoyed racing shifter karts at a younger age, and I had a spare chassis laying about that would make an excellent test vehicle for the jet. With a little hard work and determination, I figured that it could be made to work. A jet powered go kart would certainly be a lot of fun.

The mounting of the turbo

The first thing that needed to be done was to find a good way to mount the turbo solidly to the chassis of the kart. I used some tube steel to fabricate and weld the triangular support bracket setup that would hold the engine up in a good position. Note the original exhaust nozzle on the engine. A redesigned one is visible later in this section.

The engine mounts

The engine placement on the kart keeps it high enough to allow a good flow of air into the inducer of the compressor. There is plenty of space underneath for support equipment such as the oil pumps and tanks. Since I plan on wearing a helmet any time I operate the kart, I am not concerned with the proximity of the drivers head position to the intake of the engine. If you look closely, you can see that the engine is slightly off center to allow the intake air to pass over the driver's shoulder so that the air can take a straight path directly in.

Fuel tank

I fabricated a fuel tank to fit in one of the kart's side bumper locations. The tank was made from 5 inch diameter pipe with end caps welded on and finish ground. I had to make modifications to the initial tank design due to a design flaw. To regulate fuel pressure, a pressure dump is used to return excess fuel back to the tank. I originally placed the fuel return and the fuel pump suction port on the same end. The frothing of the fuel as it is returned to the tank would cause air bubbles in the fuel being pulled by the pump. A simple relocation of the fuel return line solved the problem.

Combustor mounted

With the combustor painted and cleaned up nicely, it was mounted to the turbo to check for clearance and general fit. The mounting system held well, and because of the offset entrance to the compressor inlet, the engine was centered nicely in the frame.

Oil tank

An oil tank was fabricated similar to the fuel tank by using 5 inch diameter pipe. The drain line from the turbo to the tank is solid pipe, and also helps to support the weight of the turbo itself. At the end of the tank, a remote filter adapter originally designed for automobile use was mounted. It is very important to have a clean oil supply, as the hydrodynamic bearings in the turbo have close tolerances and tiny oil ports that could become clogged very easily.

Original oil pump

The original oil pump for the jet kart can be seen at the bottom of the picture above. This pump did end up failing during the initial tests on the kart and had to be replaced. Without a good steady flow of oil, the bearings in the turbo were ruined, and a complete rebuild of the turbo was required.

Shurflo pump

After my previous oil pump failure, I spoke with some friends who also build these engines and found that there is a good self contained pump available. I purchased one of the pumps and found that it is indeed a very reliable pump that comes as a self contained unit with its own 12 volt motor. The pump is manufactured by Shurflo, and is model number 8000-643-236. Similar pumps from this company are used for water pumping in recreational vehicles and also for agricultural spraying. While this pump is almost identical, the seals and valve materials are designed to hold up to higher temperatures and are resistant to oils. The pump puts out plenty of oil pressure, and has a good flow rate. It has never let me down, and I am sold on them.

Ignition system

I built a simple ignition system for the kart which consists of an automotive coil, a condenser, and a flasher relay. The system is wired so that when the relay energizes it powers the condenser, and then the relay switches to off and the current from the condenser pulses the coil which acts like a big transformer and allows the voltage to be spiked to create the spark. Since the flasher relay keeps cycling while it is powered, it will continue to create sparks until I switch off the ignition system. This is a very simple circuit to build, and will work for most any home built turbine engine with very little knowledge of electronics.

Gauge panel

For engine monitoring, I created a simple gauge panel. The panel consists off 4 gauges mounted on a panel that fits above the steering wheel. The temperature of the engine is viewed on the two gauges to the far left and right. The left gauge is for turbine inlet temperature (TIT) and the one on the right is for turbine outlet temperature (TOT). The gauge at the top is for reading oil pressure, as keeping a steady flow of oil on these engines is very important, and the gauge at the bottom reads the pressure in the combustion chamber, also called P2 pressure.

Ready to run

With all of the engine work and subsystems complete, I tested the kart. With the kart running I did many tests, but ultimately there were problems. As this is still a relatively new hobby to me, I knew there would be some growing pains. I disassembled the engine and went to work fixing the issues and soon had the kart back up and running again. For more information on the issues with the engine, be sure to see the HR-1 engine section of the site.

Engine modifications (before on left, after on right)

With the engine modifications ready, everything was mounted back on the the kart chassis. Looking at the engine in the two pictures above you can see where the air inlet to the combustor has been moved from the middle of the combustion chamber and placed at the rear near the end cap. The new placement of the air inlet helps to get more air in the primary zone of the flame tube and allows the burn to complete more quickly. Having the flame front of the combustion process further away from the turbine inlet will keep the temperatures lower, and allow more power to be extracted from the engine.

Nozzle

With the new modifications to the engine, I changed the jet nozzle as well. The engine ran like there was not even a nozzle attached to it. Further testing of jet nozzles in the future may lead to a better design optimized to produce more thrust while keeping the temperatures within limits.

Rear of the kart

From the rear, you can see all of the components mounted underneath the actual turbine. While I could have mounted the engine lower to the ground, it would not have afforded me all of the extra space that was obviously needed.

Wiring

All of the wiring was completed for the ignition and gauge panel. A large battery was installed to provide power to the pumps. While it is not generally very hard to mount an engine to a kart frame, making everything self contained is the trick. There is just so much to fit into the frame that you find yourself becoming very creative with the space and learning to take careful measurements. I would like to have more room for fuel eventually so that I can run the kart for longer periods of time before having to stop.

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Oil cooler

I had installed an oil cooler to keep the temperature of the bearing oil in check, but it is not large enough to do the job on longer runs. I must mount a larger cooler to the chassis and supplement it with fans to make sure that everything stays within a reasonable operating temperature. The main problem with the oil getting too hot is that it thins out and does not allow the pump to maintain an adequate pressure. From previous experience, this is known to be a huge problem.

Test drive

During further testing I took the kart out for a ride and was somewhat pleased. It ran well without any problems except the overheating. I am still working on the problems with controlling the heat of the oil and the turbine inlet. The engine runs cool from about 20% to 70% of the full power, but the real thrust comes into play at the last 30% of the power range of the engine. When the engine is pushed near the 100% power range, the TIT temps are near 1900 degrees Fahrenheit, and the TOT temps hover at about 1400 degrees. These temperatures must be kept in check, and I had to disassemble the engine to check for further signs of wear and melting at the inlet to the turbine housing.

After replacing the tires and doing a bit of cleanup work on the plumbing system as well as other light maintenance, I took the kart back out for a test. The neighbors watched and shook their heads in disbelief as I ran the kart up and down the street. I did not officially clock the speed of the kart, but if my math is correct it was doing about 50+ MPH! The neighbors watching the kart said that it seemed to be much faster today than in previous testing. I am unsure whether or not I can get the kart to go any faster without the addition of an afterburner, but further testing will see if it is possible.

It seems as though the kart is moving faster but is using less fuel on the test runs. This could very well be due to the kart moving faster and covering the same amount of ground in a shorter time. The engine is still running very hot at higher thrust levels, but by feathering the throttle when the kart is already up to speed the temps can be kept in check. Oil temperatures are running hot as well, and a new oil cooler is on its way.

Hard line plumbing

The original oil lines I was using were braided hose. Not a stainless braided hose, but more of a poly vinyl type hose with a braided component embedded into the hose itself. These hoses were not used near the engine itself because of the extreme heat, but I discovered that their use was not appropriate at all for the kart. On two separate occasions I had oil lines blow off or rupture. If this had happened while driving, the result could have been catastrophic. Hot oil coming into contact with a hot turbine will produce a very large ball of fire.

I have since re-plumbed the oil system with hard copper tubing. I did also attach a new oil cooler to the system as well as an oil temperature gauge so that I can keep a visual check on everything. I ordered an optical pickup sensor to use as a tachometer to determine engine speed. Although it is possible that I have the engine operating at full RPM, I believe that it is doubtful and there is much more room to push the limits of the HR-1's capabilities.

After one final test run on Oct. 22, 2005, a neighbor filmed me running the kart up and down the street. We clocked the kart at 50 MPH without an afterburner. I believe that I have reached the limits of the engine in this configuration and have decided to undergo a full rebuild of the engine to be called to HR-1A. More information about the rebuild can be found in the HR-1A section of the site. With an impending hurricane moving into Florida, work on the kart and engines will have to wait for a while. As soon as things return to normal after the big blow I will pick up where I left off and resume the rebuild process.

I have provided a video of the run for you to view. It is about 3 megabytes in size and may take a bit of time to load on a dialup connection.

I have had a lot of fun so far with the build of the jet kart, and know that it will only get better from here on out. Although there is quite a bit of work to be done in completely rebuilding the engine, it will just add up to more experience for bigger projects down the road. I hope that you have enjoyed reading about the first life of the go kart, and invite you to continue the journey with the HR-1A section of the site to see the engine completely reborn.

Gary Richards

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