Thumper 4WS Rear steer Mod 1:8 scale Rock Crawler by Black Crow

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Dec 10-2023 Thumper axles have been updated for strength.  The assembly videos for the old axles are still available in the description of the new video. The old axles have been moved to the retired parts page. 

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 Four Wheel Steer Intro Video

  Four wheel steering adds a new twist to Thumper. This new capability is very handy while rock crawling. The turning radius isn't cut in half, it is cut to 1/6th the normal radius. I am sure math is involved or maybe it's magic? Let's just say the difference in the turning radius is extreme.  

  Keep in mind, tight turns on sticky surfaces with locked differentials can be awkward. Not a problem though, it just jostles around a bit fighting over witch tire is going to slip to balance things out. … And you can turn the 4WS off with the touch of a button. I released several videos of the yellow Jeep with the 4WS turned off because I was not ready to reveal the new option. No problem on dirt or rough slippery surfaces. This is a rock crawler so … um? … yeah!

  This mod has all the parts to convert Thumper to a 4WS (four wheel steer) model rock crawler. The tailgate (battery box) will need to be replaced along with several other parts. 

Four Wheel Steer, How do I build this? 

1. If you Have already built the Thumper model and you want to convert it to 4WS start with the teardown video then go to the 6-C video then the AWS assembly video. 
2. If you are starting from scratch, You have not started any Thumper model yet. Go to the main Thumper page and choose the 4WS options in the assembly videos. https://www.printables.com/model/323433-thumper-18-scale-rc-cj7-rock-crawler-by-blackcrow-  You will have to eventually come back here to download the 4WS parts
3. If you got part way through and decided to go 4WS. The 4WS options start in Video 5. If you have past that point, go to the tear down video, then go back to Video 5 and choose the 4WS options. 

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Parts: ( Part needed in addition to the parts listed in the Thumper page)

links are US Amazon affiliate.  

2x- 10x15x4 bearings https://amzn.to/4cPEnfx 

2x-  5x11x4 bearings https://amzn.to/3VTBK68 

Steering servo https://amzn.to/4cVPt2r  

Servo Extension https://amzn.to/4bqoMC1 

SCX10 front Axles https://amzn.to/3PXuBOA 

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If you already Have the 2WS model built start with the teardown video. This video shows you what you need to remove before adding the 4WS parts

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Rear Steer Axle Build

4WS assembly video

Update Dec 10-2023 Switched axles to the heavy duty Morrigan style axles. Old axle parts have been moved to the retired parts page. Links to the old assembly videos are in the description of the new axle videos. 

Update Dec 10- 2023 Fixed steering tie rod. The old rod was a prototype and did not allow full movement. uploaded by mistake

Update Mar 2-2025 311SpindleLeft, 312SpindleRight Raised tie rod mount to clear axle center. 

Update April 7 2025 308AxleHoRearSteerL, 310AxleHoRearSteerR.  Added reinforcement holes.