Build Thread: High Rider VW Beetle / Comical Bug / CAD design.

[Wheel_Nut 322]

This build is a sequel to my previous 2WD Truck using a Lunchbox gearbox.   The new project follows the same lines, but uses a Mantaray rear gearbox instead!   Its designed using Autodesk Fusion 360 CAD, whereas the earlier project was designed on paper.   The wheelbase is shorter at 243mm.  I tried to improve some weakness such as the steering linkage and get a bit more suspension travel.

The body is Tamiya 11825147 VW Beetle body from M02L and possibly others.   Wheels and tyres are from Tamiya Comical Buggy.

 

The design is completed and I have most of the parts.   I have a Mantaray rear gearbox that I've been keeping from another project.   Its still going to take several weeks until I start the actual build.

You are welcome to make any comments, no matter how harsh!

 

[Wheel_Nut 322]

This video shows the chassis design.

 

 

 

This video shows the fitment of the VW body and suspension movement.

 

[Mad Ax 9310]

Wow - that's some very impressive CAD work!

I use Fusion 360 for my parts but I literally just take manual measurements from the donor parts and design just that one part in CAD - my attempts to measure and replicate existing parts in CAD have resulted in complete disasters  

[Re-Bugged 10112]

Looking forward to this 👍🏻

[KEV THE REV 2310]

I like it already !!

[Wheel_Nut 322]

23 hours ago, Mad Ax said:

Wow - that's some very impressive CAD work!

I use Fusion 360 for my parts but I literally just take manual measurements from the donor parts and design just that one part in CAD - my attempts to measure and replicate existing parts in CAD have resulted in complete disasters  

That would be great to replicate parts.   The issue I have is that printed parts are unlikely to match the strength and quality of Tamiya ABS injection moldings.  Unless there is somewhere I can get the parts professionally made from ABS.

Is the difficulty mainly about creating the correct 3D design?  Otherwise are there manufacturing issues to be concerned about?

[Mad Ax 9310]

On 9/26/2020 at 9:10 AM, Wheel_Nut said:

Is the difficulty mainly about creating the correct 3D design?  Otherwise are there manufacturing issues to be concerned about?

The difficult for me is measuring accurately.  Just last week I was trying to replace the curve of a Blackfoot arch by splitting it down into straight lines joined by points (which I marked on the body), then measuring those points against each other and against the origin (which I chose as the line between the lowest of the front of the arch and the lowest point of the rear of the arch).  In theory I should have ended up with the middle of the arch being 35mm from the origin, but with constraints added as measured for all my other points, the highest I could drag the arch middle was just over 31mm.  The only tools I have for measuring are a digital caliper set, a steel ruler and a triangular protractor.  I guess I'm not able to measure such small parts with the accuracy required.

I don't "replicate" parts as just - I just measure them so my bolt-on parts can me made to the correct dimensions.  But as described above, my measurements are never accurate enough.

My point is that you seem to have replicated the entire DF01 rear gearbox housing (and other parts) in CAD - assuming you didn't acquire those models already made, that's a very impressive feat of measurement, in my view  

[ThunderDragonCy 7876]

Echo comments above, that is some fantastic CAD work, and the beetle looks great with the comical wheels at that scale. Interested to know why you've chosen a 4 link beam front axle?

[Wheel_Nut 322]

23 hours ago, Mad Ax said:

I don't "replicate" parts as just - I just measure them so my bolt-on parts can me made to the correct dimensions.  But as described above, my measurements are never accurate enough.

My point is that you seem to have replicated the entire DF01 rear gearbox housing (and other parts) in CAD - assuming you didn't acquire those models already made, that's a very impressive feat of measurement, in my view  

In this case I'm also not replicating parts.   For my chassis design it is just a CAD "component" that is created to look like a gearbox and have the mounting screws in the correct location.   It wasn't really necessary for me to create a CAD model of the entire TA01 gearbox.   I did it partly so I could create a realistic looking image on the CAD screen.   Of probably greater benefit, it helped me practice CAD "extrude" functions such as Cut / Join / Intersect operations, and also make design revisions using "timeline" functions in Fusion 360.

If I want to actually make a 3D printed gearbox there are many details that need to be checked and added.  Its almost certain that some of the detail dimensions will have errors, but hopefully it will not affect my chassis design.   The stock TA01 gearbox comes in 3 pieces, as it has a top cover and rear cover.   My CAD model has gearbox and top cover in one CAD "Component" but even still it has many simplifications compared to the actual mouldings.   I have attached the 3-view of the sketches I created in CAD for anyone how cares to see them.   From these drawings all of the 3D features were created using extrude functions in around 10 steps.

[Wheel_Nut 322]

19 hours ago, ThunderDragonCy said:

Echo comments above, that is some fantastic CAD work, and the beetle looks great with the comical wheels at that scale. Interested to know why you've chosen a 4 link beam front axle?

Thanks for the kind comments.  Good question about the reason for 4 link beam axle!   The main reason I chose it is because its very simple to make, and it has a high proportion of parts than I can make myself from metal extrusions and FR4 fiberglass sheet.   I also believe it will serve well for this design without major issues.   I actually like the panhard-rod used to locate the front axle because it determines the height of the suspension roll-centre at a well fixed location.  

There are some disadvantages for the rigid beam axle compared to a double wishbone setup, such as limited suspension travel and increased unsprung weight.  If getting really technical, there is potentially some gyroscopic reaction force when left and right wheels are coupled on the same rigid axle.  Let me know if there is something I have missed, or other reasons why I should consider a different approach.