Tamiya DF02 Rear A-Arms by rcnand

Last crawled date: 3 years, 1 month ago

Rear A-Arms for a variety of Tamiya DF02 vehicles.
My first gen Gravel Hound had/has a lot of slop between the U-bar/hinge pin and the A-arm inner chassis pivot (both front and rear arms). I'm not sure how typical this is of later generation builds, but it appears to be due to an undersized u-bar/inner hinge pin. This has a nominal diameter of 2.9 mm while the typical partially threaded hinge pins used on the outer portions of the car are 3 mm (like every other Tamiya vehicle). The chassis/inner pivots match the part tightly (2.9 mm bore) but the A-arm uses the same size hole on the inside and outside (3-3.1 mm). While this may not seem like much, it translates into a good amount of slop out at the wheel. I'm not sure why it was set up this way as my other Tamiya kits that have a similar set up do not have this kind of slop.
This design is setup with 2 degrees of built-in toe-in at the outer hinge. The originals are somewhere around this (potentially 2.5 degrees). I cannot measure this exactly - so keep this in mind. If you are going to replace your arms, please print a set for this reason as you will want both sides to match. Additionally, another outer mounting shock position has been added to the arm.
Print the arm as you typically would (supports only touching build plate), ream only the outer hole with a 3 mm drill bit. If you have a 2.9 mm bit, feel free to lightly clean out the inner hole. If not, it should fit just about perfect (at least in my prints it was almost perfect with the tolerances without drilling). Tap the mounting holes with a M3 tap and use machine screws to hold the lower ends of the shock. Some light filing on the flat faces may be required if you have binding with the chassis/hub carriers.
NOTE: I may also remix this at some point to add some other shock attachments, 2.5 degree/3 degree toe-in options, and a smooth/non-webbed version. This should allow you to play around with infill percentages if you'd like to dial in different amounts of flex.