New Jet Kart

With the jet kart running and getting good results, it was time to update the engine. The engine upgrades can be viewed in the HR-1A section of the site. Let me tell you, there is a big difference in engine performance now!

The addition of the afterburner and other engine modifications made it necessary to modify the kart design a bit. Here we will document the building of the new Jet Kart.

Original Jet Kart

Here is the beloved Jet Kart in its original incarnation. Things are tight, the wheelbase is too short, there isn't much room for fuel, and the engine placement is a bit, well, "less than optimal". That is all about to change. I have grand ideas, and hope that the outcome will prove to be more pleasing to look at as well as having better handling characteristics.

Hacking the frame

Well, the more I looked at the kart, the easier it looked like it could be done. If only I knew then what I know now! (I think someone famous said that) The rear of the kart was the first to be changed, so that I could make room for the HR-1A engine which will no longer fit. The plan is eventually to put on shows with the kart at racetracks and airfields, so making it look professional is a top priority.

Extending the frame rails

The first part was easy. Just remove the rear bearing carriers and lengthen the frame rails. So far, so good. The hard part is keeping everything lined up and straight, since you wouldn't want a crooked frame.

Tubular extensions

The frame extensions are made simply with steel tubing that will slip over the original frame rails. The larger tubing will be easier to weld this way with a stronger joint, and will also provide a bit more stiffness to the frame with its larger cross section.

Attaching the axle

With the frame longer, attaching the axle was the next order of business. The axle uses bearings mounted in special bearing holders, or "cassettes". Lining things up isn't that hard, it just requires a good bit of measuring and rechecking to make things straight and true.

Cassettes and brakes

The cassettes hold the bearings in place, and the cassette bracket on the left hand side also holds the disc brake caliper. Alignment here is critical as I couldn't afford to have the brakes binding up and causing premature brake pad wear. It isn't fun to try to stop from high speed to find that your brakes are gone! Since this is the only brake on the whole kart, it is even more critical.

Axle remounted

With the axle back in place and the brakes set up, the kart had been extended by about 1 foot in total length. This makes for a lot more room to fit things. As a note here, I thought it would be enough room. Things have a funny way of creeping up on you, and this area will get cramped again pretty quick!

Engine placement

Getting the engine back on the kart was up next. As you can see in the picture above, I used a hoist to hold the engine above the rear of the kart so that I could get it aligned properly.

Fitting for the best room

The engine placement turned out to be a "not so easy" task, since thought must be taken as to what space will be available for everything else that has to fit back here.

Engine placement from the front

The new engine location also has the benefit of improved airflow to the engine intake. And besides, it just looks a lot cooler! I especially like that it is no longer behind my head. I lose enough hair from the frustration of getting things right with my engines, and I don't really need another way for my engines to make me go bald any quicker!

Offset design

The other really neat thing about the new engine placement is the offset design of the kart. In this type of kart, the driver sits slightly to the left side to provide better weight distribution for high speed cornering. With the engine placement just slightly to the right, it all works out like "gravy on top".

Final engine position

With all things considered, this is the final mounting position I decided upon for the engine. It should leave space in front of, below, and behind for me to mount the many pumps, tanks and controls the kart will need.

Engine mount fabrication

Once I had my mind set on a location for the engine, I had to fabricate the engine mounts to keep it in place on the kart. Since I am hoping for lots of thrust, nice strong engine mounts are the order of the day.

Engine mount top view

To keep things nice a tidy, I decided on a mounting system that will bolt to the two holes adjacent to the oil drain. The oil drain pipe will pass through the notch in the engine mount plate seen above.

Strong attachment

A triangular brace is used to give the mount extra rigidity, as high thrust loads will be transmitted to the frame through here. Notching the tubing takes some time, but really does give a clean look to the work an add a lot of strength.

Rear of engine mount

Top of engine mount

Right side of engine mount

The three pictures above illustrate the rest of the fabrication of the engine mount. Overall, I am pretty happy about the way it turned out, and felt that I could safely move on to the lower mounting surface.

Mounting table

This table was added to give support to all of the pumps and other things that would have to get attached below the engine. Since I will have 4 pumps on this version of the kart, I will need lots of room to mount them, and this should do the trick.

Steel tubing for the oil tank

The oil tank was up next, and I thought I should give it a go at making my own tanks. I started with a piece of basic steel 3 inch tubing and cut it to length.

End caps on oil tank

I then capped the ends of the tubing, and had the beginnings of my tank. The capacity should be good considering the size.

Threaded bungs

To make the connections to the oil tank, I will need some way to attach the threaded hoses and fittings. To make things easier, I turned some tank bungs on the lathe. These will mount to the tank by drilling a hole and welding them in. To keep the lined up (and from falling in!) there is a small lip on the back of them. Just drop them in up to the lip, weld them on, and hook up a hose. Easy as pie!

Aft end of the new frame extension

The new frame extension now has a large space in the rear which I can use to mount the new oil tank. I still have some other parts that can be mounted here as well, so I will have to make another table in this location.

Axle location

The new table in the rear will have to make allowances for the axle to clear. I will gain a lot more real estate to mount things on though, and measured from the rear of the new frame to the point I can get closest to the axle. I cut my table to fit that area.

Oil tank mount

While I was at it, I took some 3 inch tubing and cut in in half to make some cradles to hold the new oil tank.

Mounting the cradles

The new table was bolted to tabs that are welded to the side frame, and the oil tank cradles were bolted to the table. Using a bolt together method of construction is a bit more complex and time consuming, but it does mean that I can make changes much easier than if I were to just weld everything together.

Oil tank in mounting cradles

The oil tank now slips right in to the cradles and is held down with large "hose clamp" style adjustable clamps. Everything is looking nice and tidy so far.

Clamps installed loosely

As seen from the side, there is now even more room to mount things. Again, my thoughts that this would be enough room were soon dashed, but it does help and gives me much more room as compared to the old kart design.

Painted tank

I threw some paint on the new tank to keep it from rusting, and this gold / brass color was all I had at the moment. No matter, it will serve its purpose to protect the metal, and I can paint over it later. It does have a neat look to it though!

Tank bungs

The connections to the tank can pretty much all be seen above. There will be a drain, suction line, vent, bypass return, and filler cap. The large tank bung in the top center of the tank is the filler location, and I chose to use a plain pipe plug as a filler cap. It does the job well, and is inexpensive.

Clean install

Overall, I am happy. The oil tank looks nice and clean. It is certainly an improvement over the previous one, and I don't even mind the color. If things keep going this way, I might just be able to get this kart done yet!

I glad you decided to stop by and see me breathe some new life into the old jet kart. I'll have more updates on the way shortly, and think you will like what I have in store for the finished design. Thanks for stopping by, and please do remember to help us by supporting the site!

Gary Richards

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