R/C Tank Combat

Tank #T081

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Type: Strv 103 Armament: 105mm
Built: October 2011 Armor: 100mm
Builder: Mike Mangus Rating: 40/4
Status: Operational Battles: 3
Owner: Mike Mangus Points Earned: 3,750
Call Sign: Unknown Points Given: 2,000
  • Rocking suspension
  • 12v starter motors
  • LiFEPo4 batteries

  • Click Photo For Enlargement (334 Kb)
    The Stridsvagn 103 (Strv 103), or S-Tank ("Stridsvagn" being the Swedish word for Tank, literally "fighting carriage"), was a Swedish post-war main battle tank. It was known for its unconventional turret-less design with a fixed gun traversed by engaging the tracks and elevated by adjusting the hull suspension. The S-Tank was developed in the 1950s and was the first main battle tank to use a turbine engine. The result was a very low-profile design with an emphasis on defense and heightened crew protection level. S-Tanks formed a major portion of the Swedish armored forces from the 1960s to part of the 1990s

    The Strv 103 was one of two designs I looked at after deciding to build a tank in early 2009. I eventually decided on the Merkava IV instead of the S-tank because at the time I thought the S-tank was at too much of a disadvantage. Little did I know that would change a few years later.

    With the recent trend to go with smaller tanks, I re-looked at the Strv 103 and decided that in 36" scale, the design would be lightweight, use smaller less expensive parts, easier to transport, harder to hit than the huge 1:6th scale Merkava, and just too cool looking not to build.

    All good builds start with a set of plans...or in this case, a set of line drawings downloaded from The-BluePrints.com and resized to a 36" hull length.


    Click Photo For Enlargement (386 Kb)

    Click Photo For Enlargement (282 Kb)
    Not many pictures of the basic hull being built.

    The motors are 12v geared starter motors for small ATVs. I stumbled across these on eBay while searching for right angle drills. Although I had not the foggiest idea of the rpm, I figured since they were geared it couldn't be too high.

    The price was right too. Each motor cost 19.99 for a total cost of 39.98. With shipping, the motors cost less than a used Dewalt 18v right angle drill.

    Just call it the Beetle! Heh.

    The suspension is based on the successful torsion wire suspension used on SV015. Some modifications to the original suspension were made to implement a rocking suspension like the full size tank. Yes, this model will elevate it's gun like the big one!

    The two center axles rock together like a floating beam type axles found on the Sherman tank.


    Click Photo For Enlargement (281 Kb)

    Click Photo For Enlargement (328 Kb)
    Sitting on its road wheels, the Strv is almost starting to look like a tank instead of a demented wooden insect.

    The center rod linkage ties the front and rear pivoting axles together. A rather large yet strong linear actuator moves the pivoting axles to tilt the hull forward or back. This layout with the actuator in back proved to take up too much space in the rear of the hull where the rear axle tension device has yet to go.

    Note the two rods sticking up along the inner hull wall. Those are the arms for the center suspension axles. They are tied together with a cable swag. The rods can move independently inside the floating link to prevent binding when the center axles rock back and forth. The center axles are still independently sprung due to the torsion rod design.

    After taking a day and a half break to think about the actuator position, I finally went with what is in the picture. The actuator is mounted alongside the center link rod. A robust 5/16" bolt connects the actuator to the clevis.

    Also, the rear axle and simple metal tension device is installed. Hopefully I learned my lesson with SV015's belt tensioning failures and built something that will hold us here.


    Click Photo For Enlargement (322 Kb)

    Click Photo For Enlargement (582 Kb)
    Another view of the suspension linkage setup. The center pivoting coupler was made from 5/8" round steel. Each torsion rod is clamped into the coupler with two 1/4"-20 set screws. There will be a lot of torsional stress put on that point of the suspension.

    The battery cells are 20ah, 3.2v Lithium Iron Phosphate cells. Here, they are serving as weight to counterbalance the motors in front of the hull. The tank will get four cells for a total of 12.6 nominal volts. These cells will not be used. Instead, a set of larger 40ah cells is earmarked for the tank. Total battery weight is a mere 16lbs for a 40ah, 12v battery.

    The actuator can move 102 lbs and can statically hold 500 lbs. More than robust enough for this tank.

    Also note the box over the center rods on the side of the hull. It is for protection of the rods and electrical equipment inside the tank as well as limiting the fore and aft travel of the center axles.


    Click Photo For Enlargement (293 Kb)

    Click Photo For Enlargement (291 Kb)
    The upper wooden hull is a mix of 3/16" framework and track tunnel pieces as well as 1/8" oak door skin for the outer armor plates. It is starting to look pretty cool.

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