STRV.-103C

Specifications:

Scale 1/18

Drivetrain: 2 XL motors

Steering: L motor

Transmission selector: Servo motor

Suspension adjustment: XL motor

Dozer blade: M motor

Power supply: AA battery box

Suspension: Torsion bar

The Stridsvagn-103 (STRV.-103 for short) has always been a model that I have aspired to build.

It offers many unique challenges and mechanical functions not commonly found on other vehicles. My model pays homage to Sariel's S Tank 2, one of many models that Inspired me to build my own RC vehicles. Until now I hadn't attempted to replicate the complexity of the vehicle, as it adds lots of auxiliary systems, such as the adjustable suspension. The concept of this vehicle may seem rather simple, as it lacks a turret, though the low height of the hull roof condenses most of the equipment of the vehicle into the lower hull's internal space. This leads to many challenges with the operation of the suspension, as the vehicle lacks the turret, and the main cannon is solidly affixed to the hull of the vehicle. To elevate or depress the main gun, the whole vehicle is required to articulate it's suspension to change the angle of the gun. This function was somewhat difficult to replicate, as the real vehicle uses a hydraulic system to do this rather than a mechanical solution such as the one I used.

To retain the functionality of the suspension and provide the operation of the ability to adjust the angle of the suspension was solved by using a 1:3 reduction between the sets of front and rear torsion bars, this allowed the suspension to remain flat to some extent and the hull changed position depending on the angle of the swing arms.

One of the primary purposes of the design for the Strv.-103 was for it to be a defensive vehicle, thus the tank is equipped with a deployable dozer blade for entrenching the vehicle to form defensive berms. On the real tank, this process is done manually, though with my model, I decided to motorize this function. The blade can be deployed and it locks in place due to the geometry of the linkage.

The design of my model isn't entirely perfect though, I encountered lots of issues with the drivetrain, and the hull tilting mechanism. Unfortunately college was approaching fast, so I didn't have much time to try and rectify the issues. In hindsight, I should omit the steering mechanism, as the large amount of gears operating in a small space adds lots of unneeded friction and more potential problems. One of my solutions was to add an additional XL motor to the drivetrain, this just resulted in breaking knob gears apart, as the main drivetrain's internals are thoroughly reinforced. Though the main issue that was occurring was the 12z gears slipping where they meshed with the differentials, and the 12z direction inverter mounted above left differential. I couldn't find a better solution for reinforcement in the space provided, and I didn't want to compromise the exterior of the model. The L motor for steering is underpowered because of the large amount of friction exerted by the worm gear, this leads to it stalling, I noticed this issue with the IS-7, though It didn't seem as prominent, maybe from use the internals of the transmission and steering gear began to wear down from the usage in the at model. The Suspension caused more issues with the worm gears, this resulted in lots of broken and twisted teeth on 8z gears, I solved this issue by doubling up the worm gears and 8z gears, and powering the whole setup with an XL motor. 

some of the broken parts from this model.

I am very proud of the aesthetics of this model, the exterior captures the detail of the real vehicle to the best of my extent. I spent lots of time focusing on the angles and the textures that break up the rather flat surfaces of this vehicle. one of the more rewarding parts was the fuel tanks on the vehicle, both the side skirts and the rear fuel tanks are a combination of SNOT work that creates a rather detailed component that was rather difficult to achieve with regular techniques. Most of the panels of this vehicle came together with very small gaps, something that required a lot of thought to avoid gaping holes in the side of the vehicle.

Overall I am pleased with the exterior of the model, the functionality could be greatly improved I guess I may have asked for too much complexity in a small space. That being so, I think the current version of the steering mechanism needs some major revisions to improve its durability and functionality before It can be mounted in another model.

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