Steam Beetle

Warning.... lots of pics, video at the bottom!


Engine/Boiler: Cheddar Pegasus, 4 cylinder double acting engine, with water feed pump, yarrow style boiler, gas attenuater, igniter, and PM research steam whistle
Propane /Butane Mix
Chassis: Tamiya High-Lift, 4x4 with 3 speed transmission, locked diffs, full ball bearings
Wheels: RC4WD narrow bead locks

Body: Aluminum frame & aluminum sheet metal
R/C: Spektrum DX6, 7.2V Nimh, 7 futaba servos, headlights
Run time: 30 mins
20 lb. (empty)

The Build:

The Chassis
I'm a huge fan of Tamiya, everything Tamiya is subject to careful consideration for a steam conversion ( this is the 8th one so far ). I've been thinking about this High-Lift steam conversion for quite some time, and finally devoted my best running steam plant to the project. The reasons for using the High-Lift as a steam project, are because it has a nice location for a motor, strong frame, nice stiff leaf spring, and 3 speed tranny.

Mounting the steam engine and boiler on the Tamiya High-Lift Chassis

Parts disassembled

3 Speed Tranny

Steam conversion
The Cheddar Pegasus is a marine plant, so the engine is made to fit propeller shafts. Adapting it for this project required the engine to adapt to a much smaller pinion shaft. Luckily the High-Lift chassis had just enough room in the front (which later became the back) to fit the 4 cylinder engine.  The boiler was mounted as centered to the chassis as possible to spread out the distribution of the weight to the four wheels.

The super heavy weight fight
Although it looked like one of the simpler projects, it turned out to be quite a nightmare solving all sorts of issue while converting it to steam. In the end it ran better than I could have hoped for, but it was not an easy road. Tamiya designed the High-Lift for the light weight of  electric rigs. The single biggest problem was the weight of the steam parts, the Steam Beetle weighs in at 20 lb. empty with no water.

The first issue with the weight started in the wheels and tires. I replaced the stock tires and wheels to 2.2, but immediately encountered flat tires, especially when crawling. The stock foam can not support the weight, and the tires basically were always compressed, with the rim of the wheels grounded. This also made it impossible to turn at all.  I found the foam solution by replacing the tire foams with extra large pool noodles. These have the correct outer diameter, and only required the inner hole to be trimmed to fit the rims. RC4WD provided me with a set of really sweet bead locks, and these really helped in holding the foam and tire in place, bolts to both sides of the rims. These aluminum wheels are really nicely machined, and fit perfectly.

2.2 rims with foam. The foam did not support the 20 lb weight of the steam beetle.

RC4WD bead locks with pool noodle as foam. These rims are beautifully machined aluminum, and bolted on both sides.

Final wheels works perfectly.

Second issue was the suspension.... when you turn, it leans, and stays leaned. I had similar issues with my steam rover, but at least that one had 6 wheels and shocks to spread out the load. Luckily this was easily solved by using the maximum amount of leafs supplied in the High-Lift kit. And lastly, the weight really gave the servos a hard time when it came to steering. I had doubled up the servos with 2 high torque futabas, initially for 4 wheel steering. However, the wheels just wouldn't budge under the load. I then locked the back wheels, and linked the servos together to just steer the front. I also had to, for the first time, rely on 7.2v battery to power the servos.... all 7 of them.

Doubled up the steering servos with 2 futaba s3305 high torque servos

To further improve the performance to the chassis, I upgraded all of the bearings to ball bearings. This made a pretty noticeable difference. I just wished that I had put in the ball bearings during the initial build of the chassis, as replacing them meant disassembling just about everything! I also locked the front and rear differentials, since this thing won't be breaking any land speed records..... although I am pretty sure that it's the fastest R/C steam beetle on the planet.

The Air Steam Bug
After getting these issues worked out, it's time to take just a steam 4x4 and add some character to it. Once again I turn to nature for the best designs. I decided a beetle would be suitable for a crawler, and immediately went for my favorite bug,  the Japanese rhino beetle (Allomyrhina dichotomus). First step is to switch the front and rear ends of the high lift, because I really wanted to have the engine exposed in the back, and not hidden in the head. Part of the appeal of SteamPunk is the visibility of the mechanics, and I rather not cover it all up. After laying out the aluminum frame, I realized that it looked very familiar. After some surfing, I found that an old anime show called Time Bokan, has a beetle vehicle called Mechabuton, it has wings that can open, as well as an engine in the back! I have vague memories of the show....  must have stored it away as a kid, and filed it under: "make one of these when you grow up"

Allomyrhina dichotomus

Time Bokan Mechabuton

Start of the aluminum frame

Aluminum sheet metal body

The aluminum frame were bought at a local hardware store, they come in variety of thickness and lengths. Aluminum is light, easy to drill, cut, and bend, great stuff to work with.  The aluminum sheet metal was then applied by nuts and bolts. Hinges were used for the head - as to get to fueling the gas tank, water reservoir, and igniter. hinges were also added for the wing shells- to get to the condenser and rc gear.

Radio Control
I got all geeked out and used 2.4 GHz DSM spread spectrum this time, and used the Spektrum DX6. After using up the joysticks, I had 2 extra channels left, might as well add servos to the wing shells. Adding the servos to the wings were more challenging than I had anticipated, there isn't much room for servos. After some hair pulling, I realized that servos can be mounted to the inside of the shells themselves, rather than to the frame to control the shells.


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