Well, it is finally time to put the GR-5 to work! I have been kicking around some ideas on how to use the GR-5 and have settled on a muli-purpose project. I plan to build a vehicle that will act as a gas turbine test bed that I will be able to field test small gas turbines on. The GRV-1 (Giandomenico Research Vehicle) is what I will call it and it and it will accommodate thrust engines as well as turboshafts.
The basic layout of the GRV-1 will be like a flat bed truck with the driver being over the steering axle. The reason for this is two fold: The flatbed will work best for the interchangeability of engines and the “cab-over” design will allow for greater use of space. This design will not follow the conventional approach to jet powered go karts as it will be non-aerodynamic and have a high profile. The purpose for the GRV-1 is to have a sturdy test platform that I can bolt the kitchen sink to if I want. I like this design also because it will allow the driver to “bail” quickly if there is a “problem” as a sit-in kart would be hard to get out of in a hurry.
To get the GRV-1 project started I had to devise a drive system that would connect the GR-5’s drive shaft to the wheels. After some thought I decided on using a “jackshaft” system to allow for the use of a clutch and drive chain as used on go karts. I figured on using the shaft and bearings I used on the dynamometer project for my jackshaft. Because there will be more electrical devices on this vehicle, a bigger alternator will also be needed so I incorporated a 55 amp alternator to the jackshaft design. By machining a spider drive coupling to fit an automotive alternator shaft, I was able to couple the alternator to the end of the jackshaft. I built bearing mounts below the turbine gearbox and then installed the jackshaft system. To transfer the power to the jackshaft I used two 3” pulleys and a v-belt. The v-belt is tensioned by an automotive idler pulley.
With the jackshaft in place, I was able to get the alternator situated at the end of the shaft. Once the alternator was positioned I measured the dimensions and built the brackets to hold it. I removed the alternator and welded in the brackets.
After fine tuning the alternator mounts, I bolted it into it’s cradle. The shaft assembly was ready for testing so I rolled the engine out for a test run.
Once the GR-5 was up to operating temperature I ran her up to see the effects of the alternator. As the engine was running I disconnected the alternator armature circuit to see the change in speed. When the alternator was operating it slowed the shaft at low RPMs but did not stop the engine from achieving top RPM when full throttle was applied. This is a good test result as it will work as planned. To complete this phase of the project I built a pulley guard to fit over the drive belt. The future benefit of the drive pulleys will be seen if I have to change drive ratios. It will be easy to change these pulleys to different diameters after the engine is installed.
The next step is to lay out the GRV-1’s dimensions. I wanted to make the kart as small as I could while maximizing engine mounting space. I also wanted to make the kart so it would fit into a pickup truck for transporting. The wheel base that I came up with was 46” axle to axle by 42” wide with an overall length of 80”. I purchased some 15x6x6 knobby tires and rims which helped me to visualize the overall dimensions of the kart.
By placing the GR-5 over the rear axle I can easily connect the jackshaft to the wheel axle with a roller chain and clutch. I used my floor jack to position the engine over the wheels for measurement. Having my preliminary measurements down I can go buy steel to start the framework with. I hope the price of steel has not climbed :0)
