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Hi everyone! I just wanted to share a project I have been working on to update the ORV chassis for the Monster Beetle. I have been out of the hobby for a long time, but have always had this project in the back of my mind. The two main goals are to get the most out of the suspension travel and to handle the power of a brushless setup. Although the majority of the chassis parts are replaced, keeping the following recognizable features were a priority.

  • Rear trailing arms and axle boots
  • ORV gearbox
  • Front swing arm brackets
  • Front suspension trailing links
  • Original wheelbase (almost, but not quite)
  • Rear cantilever shocks (failed)
  • Original track width

Maintaining the original wheelbase was not possible because of the reoriented battery, resulting in a 6% (15mm) increase. Designing a robust rear cantilever shock setup has also been challenging as the additional links and pivot point introduce significant weight and potential points of failure. Unfortunately this is something I have had to compromise on for now, however the "we have BBX at home" rear suspension has been working reliably with upright shocks.

Here are some photos from various early stages of development. Several parts are still in the mail, but I will continue to update as kinks are worked out!

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Wow, that's great work!  I love how you've remade the entire chassis but kept all the design cues.

What material is it made from?

This is the sort of modern update I love and just the sort of attention the ORV chassis needs.

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great project. been fun watching your process on Instagram. 

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6 hours ago, Mad Ax said:

Wow, that's great work!  I love how you've remade the entire chassis but kept all the design cues.

What material is it made from?

This is the sort of modern update I love and just the sort of attention the ORV chassis needs.

Thank you! I used to scrutinize all the little design details as a little kid, and really wanted to keep as many as possible. The prints are all done in PLA-CF right now, but I would eventually like to print the final version in PA12. The layer adhesion with PLA isn't as strong as I'd like, so print orientation has had a big impact on the durability of parts.

 

1 hour ago, ADRay1000 said:

great project. been fun watching your process on Instagram. 

It's andyray998! Thank you! Looking forward to seeing that Mini come together.

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You maybe could strink the wheelbase back if you lay the servo at the bottom of the chassi, tilt the battery to go over it and if necessary adding a shelf at the back for the RX and ESC, its a redesign but might be worth it if you feel the longer wheelbase is offputting.

Love seeing stuff like this!

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Hah, we totally think alike! :D

I explored this concept while considering an aluminum pan chassis, to which all the bulkheads would be mounted. I ended up scrapping the idea because the angled battery and RX/ESC tray would raise the center of gravity and keep much of the weight shifted to the rear. There is also the matter of getting the battery in/out without impacting anything else. I also looked into keeping all the electronics on the pan, and mounting the battery above it, but this solution had an overall higher center of gravity as well. Another possibility was to rotate the battery 90 degrees, but that would require mounting it much further forward to clear the rear swing arm pivots. Finally, a non-printable pan chassis would mean additional cost for this build. The last option I explored was to have the servo, RX and ESC on a tray above the battery, and make the battery accessible from below the chassis (with a cover plate). This might have worked, but I was pretty set on keeping the Frog skid plate as it is one of my favorite original Tamiya parts on the ORV.

Here is a quick mockup with a 3S LiPo, and a standard Futaba servo sitting flat on the bottom of the chassis (there isn't room for the servo saver or steering linkages in this drawing):

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At the end of the day, I felt that accepting this small increase in the wheelbase was a reasonable compromise. The upside is that even with a 3S setup, wheelies are very controllable and body roll is about the same a stock. Here are a few common references for 15mm:

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