Project Rex - Developer Page - Not a complete or finalized model

Read Carefully! Read Carefully! Read Carefully! Read Carefully!

Updated May 26-2025

Important!!  If you  downloaded the front axle upper and lower diff before May 10- 2025 The triangle is on the wrong side. The parts will work you just need to put the ring gear on the opposite side as the video tells you to. Files downloaded May 10 and newer are correct. 

Update May 23-2025 - G10Stop Fixed hole depth to frame - Works properly with M3 x 16mm

Update May 22-2025 - J03OuterWheel was upside down. Flipped over for printing.

Update May 21-2025 The Front hubs are too thick for the axle shaft. This causes the M4 lock nut to come loose. The hub has been updated to allow the nylon in the nut to engage the thread better.

Update May 19-2025 - At the end of the gear box video it tells you to use 8mm screws on the OptRXCover, They need to be 6mm or less to prevent damage to wires. Video will be updated. Warning is in the Frame combine video. 

Update May 16-2025 - A10TieRod2x was wrong length. Updated. 

Update May 14-2025 - E02FrameRear and E03FrameRear -The hole for the pivot is not big enough for the head of the bolt. The file has been updated. If using the old file you will need to use a longer M5 screw than listed in the video. 

*New- If you are building the this model and would like to receive updates and early warnings of mistakes by direct message. please message me and I will message you if any problems arise. If not please make sure to read the above updates regularly.

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Project Rex Developers page: This is a resource page for people that wish to build rear truck sections such as beds, campers and other accessories for Project Rex. Most of the chassis parts will be here allowing some to get a head start on the Rollback build. The Generic frame is not part of the rollback build. (early builders see finalized folder list below) Rex is a very modular build. The frame comes in sections that can be swapped out. The front section is currently designed for a Peterbilt 352 flat faced tilt cab without sleeper. Future cab options will have new front frames spaced to work with current and future rear frame sections. The intent is to be able to combine any front section with any back section. The next option to be released by Black crow, after the rollback, will be a fifth wheel for future trailers options. The first trailer planned will be some type of flat bed for heavy excavation equipment. 

Build information:

1. The frame is reinforced with square 10mm by 10mm carbon fiber rods. The rods slide in the frame and is trapped once assembled. The rods are 440mm long and can be purchased in packs of four. The overall length of the cavity for the carbon fiber rod should be 445mm. The front frame section takes 115mm of the rod.
2. The stacks and ESC take up space between the cab and bed option. The bed can and should sit 22mm forward of the split between the front frame and mid frame. (or 27mm from center of front mount holes to farthest point forward) If stacks are removed you can use space 57mm forward of the split between front and mid frame, however the ESC on the Peterbilt 352 non sleeper version does take up some space in that area and will have to be worked around if extending to the 57mm mark. 
3. Bolt Pattern: From farthest forward point with stacks to center of forward screw hole 27mm - next screw hole 120mm back - next screw hole 120mm back -next screw hole 120mm back. Center to center Left to Right 144mm 
4. STEP files are available to build create your own frame. 
5. 5mm power shaft goes from front to back. The axles can be placed almost anywhere. 
6. Two shocks on each wheel. Each shock can have the option of three spring stiffnesses. I would start with silver (mid tension)  
7. All frame sections should be printed upright. If any part is printed flat the carbon rod will not fit or line up. 

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Measurements:

Back of cab width 264mm, 

Rollback outer width 296mm.

Length of frame behind stacks with proper stack spacing = 392mm (Frame does not extend past rear tires)

Top of frame to the ground with shocks not compressed 140mm. Compressed 105mm 

Height of fifth wheel upper flat surface is 23mm above frame or 163mm above ground with shocks not compressed. Compressed 128mm. Uses 8mm bolt as upper hitch. Fifth wheel plate thickness is 11mm.

If the suspension is fully compressed with 137mm tires,  tires are 20mm above the top of the frame. 

The rear axles are 152mm apart

The center of the middle axle is 168.5mm back from the front of the mid frame. 

If you need more measurement ask me. 

Bolt Pattern: From farthest forward point with stacks to center of forward screw hole 27mm - next screw hole 120mm back - next screw hole 120mm back -next screw hole 120mm back. Center to center Left to Right 144mm 

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Early builders / Product Testers: 

You can get an early start on the 352 Peterbilt Rollback build. If you are someone that likes to wait six months for the bugs to get worked out, this is not for you. As an early builder please let me know if you find any problems. Your help is appreciated. A list of finalized parts and videos will be listed below. (Generic Rear Frame is not used on rollback) I will start with the axles and work towards a fully functional chassis for the rollback version 

Finalized Parts: Parts without a letter/number prefix, (example “ E02”) are not finalized

Rear Axle - Assembly Video - Published April 27- 2025

Mid Axle - Assembly Video - Published May 3 - 2025

Front Axle - Assembly Video - Published May 11 2025

Gear Box 352 4:1  - Assembly Video - Published May 11 2025

352 Peterbilt non sleeper  Front Frame - Assembly Video Published May 13 2025

Rollback Rear Frame - Assembly Video - published May 14 2025

Rollback Bed - Assembly Video - Published May 18 2025

Rollback Combine Bed, Front Frame and Rear Frame - Assembly - Published  May 19 2025

Rollback Setup - Assembly Video - Published May 23 2025

Working on Cab Videos - Expected full release June 7-2025

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Parts (Amazon Affiliate) Count not complete 

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Axles and Gear Box: 

HSP Diff - (one per axle) - https://amzn.to/4mpYzJG 

Rear Axles only - Drive stub axle cup- https://amzn.to/3XM10up 

Rear Axles only - Dog bone Rear 77mm - https://amzn.to/43g51M5 

Dog bone Front Only- https://amzn.to/3D6OHCR 

Axle Pins - (need 2 pins per axle) - https://amzn.to/3SHFxkf 

Belts GT2 6mm x 110mm - (One belt per axle) https://amzn.to/42Yprso 

Belt GT2 6mm x 120mm - (need one for gearbox) https://amzn.to/4lJMuib 

GT2 ( need four Gt2 20T and four Gt2 40t) - https://amzn.to/3QFnY3o 

Bearings- (Need 36 count) 3x6x2.5 bearings - https://amzn.to/3UczOEz 

Bearings- (Need at least 10) 10x15x4 (6700-2RS) - https://amzn.to/4cPEnfx 

Bearings- (Need at least 24) 5x11x4  (MR115-2RS) - https://amzn.to/3VTBK68 

Shocks 80mm Must be this style - https://amzn.to/42TnkFk 

5mm rod - No drilling - I am favoring 150mm rods at this point - https://amzn.to/42TUc1V 

5mm Universal joint- https://amzn.to/4iV4KCs 

137mm (need 6 tires) - https://amzn.to/3vFPl6J 

Steering Servo - https://amzn.to/43nyCTL 

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Frame:

10 x 10 Carbon fiber rod 440mm long  https://amzn.to/42OqLNj 

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Rollback:

T8 Lead Screw 300mm https://amzn.to/4j6PXES 

T8 Collar (need 2 pcs.) https://amzn.to/3FaeE5m 

1/8 inch Collar (need 1 pcs.) https://amzn.to/3YHdlBG 

Bearing 8x16x5 (need 6pcs.)  https://amzn.to/3F0im1w

Servo Winch https://amzn.to/3YOTDnE 

TRX4m motor and transmission - https://amzn.to/4mnVDNF 

TRX4m ESC - https://amzn.to/3F0CFfl 

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352 Peterbilt Cab: 

Tie Rods- (need 2 ends) https://amzn.to/4gVJ75m

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Power: 

Motor - 4250 800kv https://amzn.to/4df2PHL 

ESC- Quicrun WP 10BL120 G2 https://amzn.to/4jSVpwh 

Battery- 3S Hard Case 138 x 47 x 37 https://amzn.to/3zDhmgW 

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Assembly Videos: 

Rollback Rear Axle

Mid Axle or Common Axle 

Front Axle

Rex 352 4:1 Gear Box Assembly 

Front Frame Assembly

Rex Bed Assembly 

Rex Rollback Rear Frame Assembly 

Rex Rollback Combine Bed, Front Frame and Rear Frame 

Finish Rollback