100 Horsepower Wheel Driven Racing Kart!  


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2/19/03- I have completed mounting the oil coolers and pumps. The pictures below show the installation of the power turbine oil cooler and the Tilton electric pump. I mounted the pump on aluminum brackets off of the engine mounting plate. The next step is to have the hoses made up and connect the pumps to the coolers and the engine. Then, we can focus on the fuel system. (next entry)


2/13/03- I started mounting the oil coolers today. The shaft driven kart will have two separate oil coolers. One will cool the gas producer engine oil, which is used to lubricate the main engine bearings and the accessory gearbox. The other oil cooler will cool the power turbine output reduction gearbox oil. Because of its location, the power turbine oil will get much hotter, and therefore requires a larger cooler and a more powerful oil pump. So far I have mounted the E80 12S pump to circulate the gas producer oil.

As shown in the pictures, the coolers are very steeply raked, almost laying down. While this may reduce the amount of airflow that flows through the cooling elements, it will reduce drag and also is nicer aesthetically. Airflow will be supplemented by powerful electric fans, that will draw air from the underside of the cooler.

Another point I had to consider is allowing enough room on the power turbine side to mount an engine output shaft brake, if it turns out that one is needed. Because of this, I had to move the large cooler forward, and lay it down almost completely flat. (next entry)

2/11/03- Today I mounted the throttle onto the engine, and ran a throttle cable assembly from the accelerator pedal to the throttle lever. I had to modify the cable mounting arm on the throttle lever assembly because of clearance issues. I also connected the rear brake line. I had to have a longer hose made because of the increased chassis length.

The next step is to mount the plumbing for the oil and fuel systems. Check back soon for another update. (next entry)

2/02/03- Below are some pictures of the engine mounted on the go kart, and the chain drive connected. We are getting very close to the end now... (next entry)

Engine mounted

1/28/03- As work continues on the kart, we are now focusing on the sliding engine mount. The actual front and rear engine mountings are complete, and just need to be finish ground and painted. The rear mount consists of a vertical 3/8" steel plate welded to an angle iron to provide a flat base. The front mount consists of two vertical struts, cut from the same steel plate, welded to another angle iron. The front struts bolt into the four holes where the engine lift handles are normally located. The front and the rear mounts carry the engine and create a flat bottom so the engine can be set upon a flat surface.

These mounts will sit on top of two horizontal plates that will be welded to the chassis, one on each side. These plates form the basis for the sliding mount system. The engine mounts are not fixed rigidly to these plates. Instead, slots in the base plate allow the bolts to slide fore and aft as much as three inches, to take up any slack in the chain. A horizontal threaded bolt on each base plate is turned to slide the engine forward. Once the chain tension is set, the sliding bolts can be tightened down, fixing the engine in position.

Once the two base plates were fabricated, they were bolted to the bottom of the engine and mount assembly. Then, the whole works was set down on top of the kart chassis, and was measured for final positioning. After careful alignment, the base plates were tack welded to the kart chassis. Then, the engine and mount were removed so that the plates could be fully welded to the chassis. Once we grind and paint the plates, the engine mount will be completed. (next entry)

Above left Gregori is seen welding the engine mount to the frame.

1/22/03- The shaft has now been modified to accept the bearing in the appropriate position. We fabricated a bushing-like steel ring to slip over the small section of the shaft, and we ground away a small v-channel on the mating edges so that we could fill it with weld. After welding the 40 mm extension to the shaft, we turned it on the lathe to make a smooth, uniform surface.

After this was done, the bearing was heated and press fit onto the shaft. Finally, the aluminum bearing carrier was heated and the bearing itself was pressed into the carrier. Below are photos of the bearing, the bearing carrier, and the shaft together. Here we are measuring up the assembly to the engine mounting plate.

The vertical engine mounting plate before being cut

Today we also started measuring up for the engine mount. The vertical mounting plate was cut and the engine was bolted up to it. The mounting plate will sit on a narrow horizontal plate that has been welded down onto the chassis. Though we are still experimenting with a few different setups, it is pretty clear that the installation is going to look quite neat. The engine is a perfect fit in the elongated section of the chassis.

We are now in the process of devising a sliding mechanism for the engine mount, so that we can slide the engine fore and aft in the chassis, to adjust the chain tension and compensate for various sprocket sizes. We will also need to add tube struts to support the front of the engine, and provide a way for them to slide as well. I am not confident that the vertical plate alone will be able to support the weight of the cantilevered engine. (next entry)

Test fitting the engine

1/19/03- Today, I picked up the output shaft. I had the shaft custom made so that it would plug neatly into the power turbine output reduction gearbox. The small section of the shaft contains two fingers that turn the N2 overspeed governor switch, splines to mate up with the gearbox, and an o-ring recess. The shaft then increases in diameter to 40 mm, so that the bearing can be press fitted, and also to hold the drive chain sprocket. The chain sprocket will sit on a keyway that my machinist will have to cut into the shaft. Special thanks to Eric Licht for helping to have the shaft made up.

Output shaft

We are going to have to make a few minor modifications to the shaft in order to make it work perfectly. Aside from the aforementioned keyway, we are going to have to extend the 40 mm section closer to the splines to be able to sit the bearing as close as possible to the rear of the engine. Also, the shaft was made over-long, so that we can cut it to the proper length once we have everything measured up and mounted. I still don't know if braking harware will be required on the output shaft to help slow the kart down, so the added shaft length may be very useful.

The next step is to press fit the bearing onto the shaft, and then plug the shaft into the engine. The bearing carrier and engine mounting adapter can then be mounted over the shaft.

With the shaft completed, we can then mount the engine to the chassis, and continue to work on the rest of the kart. Stay tuned! (next entry)

12/05/02- Now that the engine is up to spec and ready to go, and the chassis is completed, it is time to focus on the engine mounting system, the marriage of engine and chassis.

The mounting system consists of a vertical mounting plate, which will bolt down onto the kart chassis. We will bolt an aluminum bearing carrier onto the JFS mounting adapter, which will carry the driveshaft bearing and the driveshaft. The engine and bearing carrier will then be bolted up to the vertical mounting plate, using the same bolts that will hold the bearing carrier.

Today, we completed fabricating the bearing carrier. Our expert machinist, John Minervini, machined the bearing carrier out of solid aluminum stock. All that is left is to machine the holes that will allow it to bolt up to the JFS mounting adapter. An SKF sealed ball bearing will sit snugly inside the bearing carrier and carry the engine side loads. The output shaft will be press fit into the bearing, to drive the axle. Fabrication of the output shaft should be completed by next week. (next entry)

Special Thanks to John Minervini and Joe Colella


12/01/02- With the chassis extended, it was time for a seat fitting. We maneuvered the seat into place about where it needed to be, on top of wood blocks so that the bottom of the seat would not touch the floor. I sat in the kart, and we moved the seat around until I felt comfortable, and then made marks for the drill holes. The seat struts had to be bent slightly in order to match up the holes. Rubber bushings were used on the front seat mounts to allow the holes to meet. The holes were drilled in the seat, and the seat was bolted into place. (next entry)


11/27/02- After we finished welding in all the cross bracing and support struts to stiffen the now longer chassis, it was time to paint the new tubing. First, we ground away any of the excess weld bead. Then, after applying a primer coat, we gave it a final pass with the grinder to clean it up and make it look neat and integrated. Then, after computer-matching the paint color, we applied a generous coat of yellow to the rear end of the chassis. The finished result looks great; it is difficult to tell where the added tubing is. (next entry)

Chassis lengthening complete

11/19/02- Today we successfully extended the chassis, and at the same time we also relocated the rear brake to the right side of the chassis. Originally, we were going to weld the rear end to the front end, and then relocate the brake mounting bracket to move the brake. Instead, we decided it would be easier to rearrange the rear chassis tubes to move the brake to the other side. The cut rear of the chassis consists of three straight tubes, each with an axle bearing carrier attached. We removed the rear axle, cut the tubes apart, and swapped the left tube for the far right one. We then relocated the brake rotor to a keyway that was conveniently in place on the right side of the kart. I believe this keyway is there in the event that an extra rear brake is to be added. It came in very handy. The rear brake rotor now resides on the right side of the kart, on the outside of the chassis structure.

The images above show work being done on the kart chassis. After we swapped the rear chassis tubes, we slid the tubes onto the smaller diameter continuous inner tubing that was already in place. We had to modify the lengths of the outer extension tubing to make the chassis straight. Then, we carefully measured the wheelbase on the left and right sides, making sure they were equal, before we spot welded the chassis together. We stick welded the chrome-moly tubing, and then used a grinding machine to trim any excess bead and make it look neat. Finally, we mounted the brake rotor onto the keyway and we mounted the brake caliper in place over it. When we are done welding all of the cross bracing into the chassis, we will sand everything down neatly, and then paint all of the new tubing the same color as the rest of the frame to make it look homogenous. (next entry)

11/10/02- Today I picked up some miscellaneous go kart parts that I will need to complete the project. I picked up a complete set of sprockets, ranging from 21 to 30 teeth, some chain for the sprocket, a fiberglass seat, and a length of brake line so that we will have enough line to be able to reach once we relocate the rear brake to the opposite side of the chassis.

I will start with the complete set of sprockets, and figure out which ratio will best suit my needs. I will probably test a few different ratios so that I can adjust them quickly depending if I am going to want maximum acceleration, or maximum top speed. With the amount of power we are running, I should be able to gear the kart for up to 200 miles per hour and still have meaningful acceleration. I decided to go with a fiberglass seat, as opposed to a carbon/kevlar one, mainly because of availability, and because the fiberglass is just about as light anyway, and is a lot cheaper. Of course, that kevlar would be nice if the turbine decides to let go... (next entry)

11/07/02- Today I received the instrument box with starter relay, and a few other small engine parts. That completes all the engine and related parts I need for the project. Now the shift focuses on getting the chassis together.

The pictures above, clockwise from top left, show the instrument panel with starter relay, a close up of the instrument panel with digital N1 tach, on/off switch, starter button, and starter indicator, a spiral lock and retainer clip that will hold the output shaft in place, and the magnetic monopole pickup that counts gear teeth in the accessory gearbox as a frequency, which the digital tach then converts into a percentage of 73,000. (RPM) (next entry)

11/04/02- I spent the last week or so messing around with chrome-moly tubing with a view towards extending the chassis. For some reason, we couldn't find tubing that would totally match up with the kart chassis tubing. I think it has something to do with the metric system...

To ensure that the chassis remain completely straight after we weld the extensions on, I decided to use continuous pieces of smaller diameter tubing that will fit inside of the front and rear chassis sections. I cut these inner tubes to 25 inch lengths, to account for for the 11.5 inch chassis extension tubes, plus the 6 or so inches on each end that would fit inside the existing chassis tubes. Because we couldn't find the perfect fit tubing, I had to get slightly larger tubing and turn it on a lathe, to get it down to the right diameter.

The inner tubes turned out to be a tight interference fit, but a little bit of hammering got them home. Aside from keeping the chassis straight, these inner tubes should add a lot of strength to carry the weight of the engine and any excess load. Once the inner tubes were inserted, the 11.5 inch chassis extensions slid easily in place. All that remains now is to slide the rear end of the chassis in place over the inner tubing, and weld everything in place. I will be bringing the chassis to my shop tomorrow where it will be welded, and where work on the kart will continue. (next entry)

Fitting the chassis extensions

10/16/02- With the chrome-moly tubing arriving at my shop, I decided that now was a good time to figure out exactly how much I should lengthen the chassis by. To do this, I suspended the JFS-100 from a hoist in my garage, and then wheeled the two cut sections of the kart frame into place underneath the engine. The carbon fiber/kevlar seat still has not arrived, so I used the seat from my turbojet kart so I could see how the engine would fit in place behind the seat. After I lined the chassis parts up, I started raising and lowering the engine, and moving the chassis sections side to side, backwards and forwards, and moving the two sections further apart and then closer, until the engine looked like it was more or less in the right place. Then I started making some measurements and fine adjustments, to really see if it would fit.

We are working with a few tradeoffs here. Obviously, the longer I make the frame, the more extra room I will have to to comfortably fit the engine and the connections (hoses, wires, etc.), but at the same time, I don't want to make the chassis too long. A longer wheelbase will make a vehicle more stable, but that increased stability means that the car won't change direction as quickly. A defining characteristic of a go-kart is sharp, crisp, and almost twitchy handling. I want my go kart to handle, well, like a go kart. Another tradeoff is the height of the engine. Ideally, the engine should sit as close to the ground as possible, giving the kart a very low center of gravity. A low center of gravity means minimal body roll, keeping all four tires firmly planted on the road in the corners. Then, the cornering load is taken up more evenly by all the tires, instead of just the two outside tires, and the final result is more grip, and sharper direction changes. However, keeping the engine low means that the frame must be made longer, because of the way the engine is shaped. I had to find the perfect compromise between all of these factors, and I feel that I did. I am very pleased with the way that the engine sits snugly and low inside the chassis. It is barely visible behind the seat. I also had to offset the engine to the right slightly on the transverse plane. Because a shifter kart chassis normally carries its engine on the right side of the driver, the kart frame is not built symmetrically, but rather it is offset to the left somewhat to compensate for the weight of the engine, clutch, and transmission. The driver does not sit on the centerline of the kart, but off to the left a little.

After I decided on a final mounting position for the engine, I made a few marks on the frame, and measured the distance we had between the front and rear sections of the frame. I will have to cut the chrome-moly tubing to 11.5 inch lengths. The next step is to weld those lengths, and reunite the frame. (next entry)


10/05/02- I received the engine mounting adapter and band clamp from Avon Aero, and I mounted it to the engine to get a sense for how it is going to work in supporting the weight of the engine. The adapter is actually quite slick. It has a lip that locks into a groove on the output reduction gear case, to prevent the engine from trying rotate in the mount, due to engine torque. The band clamp locks everything together nicely, but actually doesn't support any load. The adapter has six bolt holes in it. Before the plate is clamped to the power turbine, the bolts are set in place. Then, these bolts can be used to securely mount the engine to a vertical plate which will then be bolted down to the go-kart frame. A bearing carrier with a sealed grease bearing will be mounted in the center of the kart chassis mounting plate, and that will support the stub shaft that will transfer engine power to the drive sprocket. (next entry)

"And this one time, at band clamp..."

9/30/02- Today we went ahead and cut the kart frame. Even though it was sad to cut up such a beautiful piece of chassis, I know that the end result will be well worth it. Because of the tight clearances between the seat mounting bracket and the rear bearing carrier, we decided to use a hacksaw so that we could be as precise as possible. The cuts ended up being quite clean.

Once I get the carbon/kevlar seat in, I will install it and then figure out precisely how long the chassis extensions need to be. I will also need to flip the rear brake caliper and rotor to the opposite side of the axle, to make room for the chain sprocket. (next entry)

9/21/02- We have starting thinking about how we are going to approach the lengthening of the kart frame. I brought the engine and the chassis together to visualize what I will need to do to fit the JFS engine within the wheelbase. The way it is now, the JFS could be mounted immediately behind the rear axle, but I fear that this will move the weight distribution too far rearward, and could even cause the kart to tip backwards, especially under heavy acceleration. For the best balance, the engine should be mounted just in front of the rear axle. I will have to cut the frame at three points, just in front of the rear axle bearing carrier mounts, and TIG weld 12 inch lengths of chromoly tubing. I have marked off where we will cut the frame, and in the next week or so should bring the frame to my shop where we will use a bench mounted circular saw to do the cutting job. (next entry)

9/15/02- The JFS-100 engine has been completely converted for turboshaft use for the kart, has been bench tested and is completely functioning, and is back at my house. All that remains, as far as the engine is concerned, is to install the stub shaft that will drive the chain sprocket. The engine has some pretty impressive stats:

Garrett/Allied Signal JFS-100 Turboshaft

  • Peak Power: 100 shp @ 3,100 rpm
  • Peak Torque: 300 lb/ft @ stall
  • Weight: 84 lbs. (wet)
  • Power/Weight Ratio: 1.2:1
  • Compression Ratio: 3.5:1
  • Air mass flow: 1.6 lbs/sec.
  • Compressor Speed: 75,000 rpm
  • Maximum TIT: 1,850 deg F.
  • SFC: 1.17 LB/shp/hr.
  • Max. Power Turbine RPM: 60,400

Because of the free shaft arrangement of this engine, it will be relatively simple to hook up a direct drive system. At low power settings, the power turbine should act as a torque converter, and we should be able to bring the kart to a stop by just pressing on the brakes. In the event that the torque at idle is still too much to be able to stop the kart effectively, then we may have to add some braking hardware onto the stub shaft coming out of the engine. I will know this immediately after testing it.

Because of the immense torque of the engine, we will not need any sort of multi-step transmission with a large gear reduction to get rolling. In fact, in order to achieve our target speeds, I will actually have to configure the chain drive so that we are running an overdrive, ie. the rear wheels will have to turn at a higher rpm than the engine output shaft. This arrangement will have to take advantage of the engine's torque, but running a very tall rear ratio will make the kart easier to stop. The brakes should be able to drag the power turbine rpm down to stall. I will have to experiment to find the exact ratio.

Here are some pictures of the JFS-100 Turboshaft: (next entry)


9/02/02- Today we picked up the kart chassis. It is a CRG Kalifornia shifter kart model, intended for a 250 cc engine. It has a more robust feel than our Will Kart chassis, and is probably a little bit heavier as well. I am going to have to cut the chassis apart at the rear, so that I can extend it approximately 10-12 inches. This may be difficult. At any rate, the kart will probably sit in my garage for a while, until we finish getting the engine sorted out. We are also waiting on kart parts and a carbon fiber seat. (next entry)

Bare chassis for Turbokart II

8/24/02- Today I picked out the kart chassis that we will be using for for this project, and put a deposit on it. The chassis is a slick CRG chassis made by Italian kart chassis maker Kali-Kart. The chrome-moly frame is worthy of the 100 horsepower turboshaft engine. I found the kart at Keller's Motorsports out on Long Island. I'll pick up the kart sometime next week, at which point I will post some pics. (next entry)

8/21/02- Last week I picked up the oil coolers that we will be using for our shaft driven kart. The gas producer and the power turbine each have their own gearboxes and oil sumps, therefore, two separate oil coolers must be used. For the gas producer, we will be using a Flex-A-Lite transmission oil cooler, with a built in electric fan to pull cool air through the radiator core. The power turbine cooler is a larger and more efficient Perma-Cool heat exchanger, also with a built in fan. At this point I don't really know if the coolers can handle the high temperatures of the turbine oil, but we will just have to wait and see. I got these automotive parts from Summit Racing.

I am also in the process of searching for a suitable kart chassis and the kart parts I will need to get everything up and running. We basically know how we want the kart to be set up, now it is just a matter of getting all the parts. (next entry)

7/27/02- Engine work still continues. In the meantime, I am gradually procuring the supplies we need for the project. All of the external electric pumps have arrived at this point.

I'll need three electric pumps for my kart. The first, an Airtex automotive E80 12S will be used as a fuel boost pump for the engine. Another Airtex pump will be used as an external oil pump for the gas producer oil system, to circulate oil from the accessory gearbox to the oil cooler and back. For the power turbine oil cooler, however, a pump which can flow more oil and handle higher temperatures is needed. I will be using a Tilton differential oil cooler pump to circulate oil from the power turbine reduction gearbox to the power turbine oil cooler and back. This pump is used to cool the oil in the rear end of a NASCAR stocker. The pump has an integral fan to cool the electric motor. (next entry)

7/19/02- The generator has been replaced and is functioning properly, however the engine doesn't light up on every start attempt, and has been showing an increasing reluctance to run. We supposed it was a problem with one or more of the fuel nozzles, however, replacing them has not helped the situation. Keep checking back for news. (next entry)

7/15/02- During some initial bench testing of the JFS-100 turboshaft engine, the alternating current generator has seemingly stopped working. It will have to be taken it apart to see if it can be fixed, or replaced altogether. The AC generator, driven by the high pressure turbine, provides electric current which holds open the starter relay, provides a spark at the igniter plug, and holds open the fuel solenoid valve. The engine cannot function without the generator. (next entry)

6/30/02- I have removed the output shaft from the power turbine. The output shaft is not designed to support a side load, so it will need an external bearing. We are in the process of fabricating a driveshaft that will plug directly into the power turbine reduction gearbox, in the hole left by the removal of the original output shaft. This shaft will be supported by the reduction gearbox's internal bearing, as well as an external bearing that we will obtain. The drive sprocket will then fit over this shaft. I am in the process of designing the driveshaft. (next entry)

6/24/02- With the engine still in the works, I have also started to design the chassis. As a starting point, I plan on using a bare shifter kart chassis. A shifter kart chassis seems like a good choice, because it is designed to handle high speeds, has powerful vented and cross drilled disc brakes, and has a nifty little shift lever that could come in handy.

In order to accomodate the JFS-100 engine, the chassis will have to be substantially modified. Most importantly, the frame and wheelbase will have to be lengthened. Lengthening the wheelbase will not only allow us to fit the JFS neatly behind the rear seat, as low as possible, but it will also increase the stability and traction of the go-kart. With nearly 300 lb/ft of torque on tap, traction is of utmost importance. Here is what some of the modifications will look like:

Artist's Rendering

Lengthening the chassis might make the kart a little reluctant to turn in very tight corners, but we will attempt to rectify this by shortening the rear track as much as possible. While our thrust powered kart is only at home on a large open runway or maybe an oval track, we plan on taking this kart to all types of tracks, including tight, twisty kart tracks, automobile road courses, ovals, and even the drag strip. (next entry)

6/17/02- I have already started work on my turboshaft powered go-kart. I expect it to be extremely fast. With a power to weight ratio in the neighborhood of 2:1, it should accelerate like a dragster.

Unlike our thrust driven kart, this kart will require a good deal of planning in order to get everything to work the way we want it. In order to accomplish this, I have divided up the project into three sections: The engine, the chassis, and the mounting system. The first two are fairly straightforward, but the mounting system is what will require a little clever engineering. More on that later...

The first step is to order the engine. I have ordered another complete JFS-100 turboshaft engine, this time directly from Tim Arfons. Before the engine can be used as a turboshaft, a number of modifications will have to be made:

-Modify the fuel governor to accept the throttle lever

-Add the throttle

-Rotate the power turbine section 90 degrees so it faces rearward instead of downward

-Add the power turbine mounting clamp which is used to mount the engine in its original application.

-Build a start control box with tach. (next entry)

The JFS-100 gas turbine starter unmodified




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