Monster Tarmo Part Version 0.5

Motivation

The original Tarmo is a racer.  Most enthusiast will use it to see how fast it can go.  I would like to turn the Tarmo 5 into an off-roader.  It should be able to ride over grass.  It should be a bit of a dirt car, and a bit of a crawler.  

Updates

Mar 17: 

• The 3:1 gear was corrected.
• C06 was corrected

Description

The Monster Tarmo project makes the Tarmo capable of Monster Truck/Crawler/Dirt car play.  

The main engineering change is the upgrade of the gearbox that reduces the ratio from the original stock 5:1 ratio to 12:1 ratio.  The upgrade allows for bigger tires tested up to 150mm.  

The car still goes plenty fast with the new gear, but it exchanges speed for torque.  This means the car now has smoother traction around big rocks, grass or slipper surfaces. 

Print Instruction

Follow the original Tarmo  5 Guide for instruction on printing the parts.   Ideally, build the full Tarmo and play with it for a while, that should help you troubleshoot if you have any issues if the issue is due to Tarmo 5's stock design, or if it is because of this mod.  If you have issues you can reach me here on the comments or at the Tarmo5 sub-reddit. 

https://www.reddit.com/r/EngineeringNS/

Additional to that, part B2 needs a print pause so you can add the nuts midprint.  This will ensures the gears keep tight and you don't begging to lose gear grip after hours of use.  Remember to test the nuts and orientation of the nut before inserting otherwise the print could be ruined.  I think I added 0.2 mm play to allow the nut to more a little if the tread does not start to grip. 

Non Printed Parts

Optional parts:

150mm Tires https://www.amazon.com/dp/B0B882C6CH?ref=ppx_yo2ov_dt_b_fed_asin_title

The butt of the car will be heavier so the original build suspension may not be enough.  I got these:

https://www.amazon.com/dp/B0BVRCYY78?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

But I think they are overkill.  Please note in the comments if you find a sturdy shock that is not too stiff for the added weight. 

Additional Notes

The car I use to test and play with the gear box uses CV joints from this remix:  https://www.printables.com/model/516804-tarmo-5-remix-by-tridense 

I highly recommend them because they have thicker CV cages and they are printed in TPU.  The original build CV's broke a lot, but these killed the problem. 

I have not use B03, B12 and B13 from this post.  I am using the stock parts and they work fine. 

Issues

Noisy.  The new gear will be noisy, but should be a fun noise.   I do plan to test Herring bone in the short term future.

Weight.  You will want to rethink suspension.  The shocks I noted above are too strong.  So something between those and the stock shocks. 

I am still working on improving the torque dampeners.  They may slip out without getting damaged if the torque is too high. 

Future Work

This is version 0.5.  It will be version 1.0 once I design the front gear box following a similar gear box pattern as the rear.  An there is 2.0 version road-map :-) 

A new Gear box is added to step down the grear ratio.  That allows for bigger tires.  The Testing model has 150mm crawler tires.  The gear ratio is 1:12