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Carrera Mercedes 300 SLR

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  • Carrera Mercedes 300 SLR

    I won this not too long ago and thought I’d share what I’ve done to it.

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    My first concern was the sloppy guide flag. I slightly opened the hole in the chassis for the guide post using a 5/32” bit. I then chucked a length of 5/32” brass tubing into the drill press and reduced the O.D. until it fit.

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    The guide flag had the typical split top that slightly bulges out. I had to sand the shaft to fit, and pretty much removed the “bulb” at the top.

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    The sanding turned out to be easier than I thought. And the result is a nice fit with no slop!

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    I like to have the front tires just off the track. But if you look at the front bushings you’ll see they allow the axle to float so that the front tires can rest on the track and ride up or down as-needed.

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    To eliminate that “feature”, I added some small shims that the axle rides on, which pushes that axle pretty much to the top of the allowed travel.

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    I then tried a few different thickness washers on the guide flag beneath the chassis.

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    Then used some thick paper as a 0.01” gauge to confirm I had the track clearance I wanted:

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    Checking for body clearance I did find that the front tires where hitting something. I very lightly sanded the wheel-wells, but that didn’t solve the problem. So I put the front tires on my Razor tire truer and slightly sanded until there was no more rubbing.

    I like to have just a bit of body float. I primarily do this because I don’t want the body to twist the chassis if the screws are tightened. While most of my cars are loose, I find a few that do seem easier to drive when the body is tight.

    So I got out my Dremel, a Model #2 which my mom bought for me back in the ‘60s!

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    I first ground off the collars around the mounting posts:

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    I started trimming the outside edges of the chassis, then did a test fit. This revealed a significant issue. The front lip of the chassis actually slides underneath the front valance, and it’s under tension. I did a lot of trimming on the front of chassis, which helped, but didn’t eliminate the issue. And I got nervous about making that section too weak. Then it hit me, why not slightly low the body? So I slowly trimmed the front mounting post, then did a test fit, and kept repeating until there was the slightest gap between the chassis and the valance (tested using a piece of paper). As a consequence I did have to slightly sand the front tires again. The last step I took was to open the body mounting screw holes using a 7/64” bit.

    I also removed the reversing switch, it’s just one more possible point of failure. It also very slightly increases the amount of resistance between the flag and the motor, resulting is slightly larger voltage drop. It’s probably insignificant, but small advantages eventually add-up.

    Rear tires were replaced with an old pair of Jel Claws. They are super soft, and were a bit difficult to true, but they work much better than the stock tires.

    I’ve got a 44’ Carrera track, but over time I’ve removed the magnets from probably half my cars. So far I’ve left this one in, but slid it all the way to the front, which also raises it a bit. Then to reduce the magnet strength even more, I cut a square from a refrigerator magnet and placed it over Carrera’s magnet. I also did this partly for looks, the stock magnet was pretty bad.

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    All in all a great way to spend a weekend!

    Attached Files

  • #2
    Good job Ron. All good advice. For me anyway I found that the front sliding mag did very little for keeping the car on the track. It did help in keeping guide flag in the slot though. I've always liked that car. Beautiful lines.
    Saginaw Valley Raceway
    Only Rule: Just enjoy who you are racing with.


    • SlotCat
      SlotCat commented
      Editing a comment
      Yes, great job and a beautiful car!

  • #3
    Nice writeup and pictures. I never thought of putting brass tubing in the drill press and sanding to reduce the diameter. Sometimes I overlook the obvious. That's a good tip.


    • Kevan
      Kevan commented
      Editing a comment
      Or open the hole up to suit

  • #4
    Got a side and front picture of the car sitting on track after mods?


    • #5
      Hi SlotCat, here are a few shots:

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      • #6
        Thanks, looks great and stance is perfect, love the oldies! Glad to see it's gets played with too!