Kyosho Ultima ST -R/EVO style steering linkages with ball bearings

thingiverse

This is a Kyosho Ultima ST Racing Sports GP steering linkage, modeled after Type-R and EVO versions. The stock part lacks bearings, with plastic resting on metal shafts, leading to quick wear and unwanted play in the steering. Replacing these parts can be challenging due to their unavailability. To address this issue, I've created a custom combination of parts that closely emulate Type-R and EVO linkages while still utilizing the stock servo saver spring. This eliminates the need for an expensive metal spring-loaded adjustable servo saver, which can be difficult to find. The design is reinforced but preserves the original steering geometry. Stock rear wheel hub bearings are used due to their widespread availability, but smaller bearings required by Type-R and EVO models may be harder to source. A potential weakness lies in the small tabs that fit into slots on the stock servo saver plastic spring. I have a plan to reinforce this area, though an estimated completion time has not been set. An update has been made to the left upper servo link, which now includes a reinforced tab design. This mod adds a 1mm diameter and 10mm long hole to support a 1x10mm metal shaft, enhancing stability in this region. The modified arm is available as a separate STL file for those who want to upgrade. For individuals without access to hard 1mm pins, they can drill the holes to 2mm and use stock wheel shaft pins instead. A plastic servo saver spring has been added to the design files for users without the stock part. Printing this with at least 0.3mm layer height and maximum temperature settings from their filament manufacturer is recommended. Play around with infill levels to achieve the correct spring effect, as results may vary depending on the filament used. The package also includes a "Racing Sports" style connection beam that installs between linkages but has been modified for bearings. Using ball joints instead of this part is advised due to design limitations. I printed these parts using CF/PETG filament and took pictures with red PETG prints, which require minimal supports. These components mount perfectly on stock Racing Sports GP chassis plates and Type-R and EVO versions, eliminating play in the steering if 5mm center shafts are in reasonable condition. If these shafts are worn, buying two 5mm HSS drill bits and using the smooth part to make new shafts is a viable option. The steering linkage shaft length is exactly 30mm, so cut the bits to this length with an angle grinder or metal cutting tool. This method works well for stock Racing Sports versions of the car since they lack threads for screws. A note has been added about potential clearance issues with some ball joints and original design files. An updated version (6.4) addresses this issue by increasing the design to accommodate newer style balljoints without hitting the upper arms' ball cup. An upgraded steering arm design (version 6.4) has been uploaded, which should clear longer balljoints without hitting the upper arms' ball cup. Users can still use previous version servo saver springs and upper arms without upgrading them. Support pins have been added to lower right steering arms, allowing users to reinforce the servo saver spring tab area with a 1mm x 5mm metal pin.