3D-print at low costs - this time a Pitbull

After my long adventure with Mallory - wich isn't completely over yet - I need something different. A job for a mechanical engineer, something technical even. Something I can build by myself without help of a hired artist. A machine. A vehicle. A reminder of the good times I once had in Entropia Universe. A Pitbull!

(image by Kpeters)

From the said good times I have a lot of 3d-grabs from the game, allmost all vehicles. Even a Pitbull:

In front of it the sexy arse of sister Kristin

I have a saying: "The first thing an engineer does, is drawing a centerline." Meaning, to name the purpose, define the dimensions and the functionality. Let's start with this new project and see where it ends.

 

Basic thoughts:

1. I cannot use the grabbed model for prints. Printed it'll look crappy. It's not waterproof, the tires have 16 edges instead of being circular and miss the profile of the tires. The good appereance ingame is done by textures and the render engine. A RL 3d-print will show merciless all the rough details. Furthermore the technical details of the chassis are a phantasy product. Not functional in real life. No true steering for example, no cushioning. Additional no hatches. Does anyone know how the driver and the gunner reach their places?
Conclusion:
I have to build my own 3d-model using the grabbed model as raw blueprint!

2. Functional or static model?
Definitely functional! Steering, cushioning, hatches etc.

3. Dimensions
When I import the grabbed model into Rhino3D Kristin is 2mm high wich corresponds to her "real" body. We both were 2m tall ingame. I assume MA built the Universe in 1:1. So I know the dimensions of the Pitbull. L x W x H: 9,8m x 6,9m x 4,5m. A bit too large for printing it. So wich scale? There is a wide range of common scales, starting at 1: "a few hundred" for giant battleships and ending at 1:12 for highly detailed cars. Since my collection of car models is in the popular 1:43 scale I thought it would be a good choice. This would lead to a model of ~225mm length. The diameter of the tires would be ~52mm. Regarding all the small parts wich are required for realistic steering and cushioning it seems to be okay. Old Kristin would be 46,5mm tall. If it's too small I will switch to 1:25 wich is a common scale for trucks and military vehicles of all kind. This model would have a length of nearly 400mm.
Well, 1:43 is it!

4. Outside only or interior too?
Interior means a lot of additional work! Seats, consoles, functional hatches, transparent windows ... not to speak about colouring all this inner areas! Hard to decide. Alas, when I was young I built some Revell models of american trucks (1:25). They had functional doors, transparent windows and detailed interior. Even my 1:43 diecast-models nowadays have interior, transparent windows and sometimes functional doors.
Okay, I will run the full program!

5. How to assemble the model?
Since we can expect a lot of small movable parts I will try something new: screw the model together. Probably complemented by snappers and glue. A new area for me, that's for sure. But I think of heated screws to form the screw thread and countersunk head screws for positioning a part to each other. Additional this method would enable me to disassemble the model easily. As for instance to replace a part or do the paint job for the interior.
Basic assembly concept: screwable!

6. Electric motors and remote control?
Well, such things call for a very special design. I think this would require way more thoughts and knowledge than I am willing to put into this project. My main goal is to print my own 3d-models.
The challenge is big enough without remote control!

7. Finish
The model should look like the original vehicle ingame. Something like the not coloured version.
Painted like the original!

That's the plan. So far. I've learned from former attempts that the plan may change according learning processes or some adversities. But as mentioned above: I need a centerline to start at.

 

The basis of everything is the chassis. So I will start with the wheels and try to add all movable parts for steering and cushioning.

This part will need a lot of tests and will probably become the main part of the project at all.

 

I made one wheel:

As suspected, the space in the rim is very small:

At the front wheels this is the place for the wheelmount, the steering axis and the ends of both wishbones. So many small parts! The steering axis should be close to the red arrows in the middle. That's too small!
Now I must rethink the scaling. Probably I should switch to 1:25.

Parallel I have to check if such flat tires will work printed with flexible material. I would really love it to have rubber tires!

 

Lesson 1:
Okay, 1:25 than. Wheels will have a diameter of 90 mm and a width of 52 mm. Pretty huge:

Currently printing the second half of the tire. The first one is promising.

 

Hehe! Exactly this is the benefit of the ability to use a CAD-software, isn't it?
(Just a small remark to push you a bit )

 

Lesson 2:
I made some coding at the second half of the tire

2 mm high. This is not enough for such very flexible parts. Hopefully the glue will solve this problem. But I will enlarge it for the next tires. Or better seperate the road tread from the shoulders.

 

Cool! But first I have to find a way to make one. I'm at a very early stadium.

 

Lesson 3:
Glue is really no option for flexible PLA-parts:

The glued tire broke immediately when I touched it.

But I am at the right course:



Additional the axle is to fat for the hole in the rim. In this case 0,2 mm air space wasn't enough. I will find out how much I need or use a metal pipe ... dunno yet.
Another task is the tire. Either I find a way to print it as one part or use a strong mechanical connection. No clue what to do atm.

But in generally I know that I finally will have rubber tires one day. That's enough for today. Several other major jobs sit in the row. Since I have a lot of space in the rim now, I will deal with the undercarriage next days.

 

Well, let's start with the steering. As mentioned already, this Pitbull is a fantasy item. Hard to make a functional version of it. But okay, it's a challenge! What do we have? The given geometry of the wheels:

The maximum steer angle at the Pitbull is something like 20°:

The pivot point of the course of a vehicle is the center of the rear axle(s). Wich leads to this:

The designer of this vehicle consumed harder drugs than canabis I guess
This was a theoretical contemplation so far. In truth the pivot point of the controlled wheel isn't in its center. It will look more like this:

Fortunately it doesn't matter much:

1° difference only. But additional there will be another limitation resulting from the vertical spring travel. Since I want to be at the safe side I will limit the steer angle to 15°.

 

All in all I will leave the original model at several points. As mentioned above, such things don't work in RL:

The 7 seats (6 passengers and 1 driver) float somewhere in the air, the hatch at the back isn't a seperate part, no hatches for driver and gunner to enter their position and so on.
But I will keep the original appeareance and dimensions. Old Kristin would be 80 mm tall. Hmm ... good enough for a raw model of an Entropia Universe character. And since I got Poser 10 I'm able to make figures sitting in a seat or whatever. I will put it to the list.

 

Harrrr! Another thread http://www.entropiaplanets.com/threads/cute-girl-is-desperete-for-peds.21817/ reminds me to another project from the past. Breezehome in Whiterun from Skyrim:

LOL! Me and Kristin wearing Entropia Universe outfit in front of the first home you can get in Skyrim. Crazy! I should keep this in mind ... don't want to run 3 projects parallel.

 

First attempt for the left front wheel:

In my CAD it works properly
Now I have to find a way to print all the parts.

 

I brooded over a good connection for all the small movable parts. Fortunately I own a small treasurebox and found something promising in it:

These little bolts are used for shelfs. Crazy, but it seems they are made especially to solve my problem:

Perfect!

 

Okay, I will fit it to the original model.


I think I can use some spiralsprings from ballpens for the spring struts.

 

Many test-prints! But slowly it becomes real:

Best part is: This time I can do everything by myself!

Aaaaaaaand: lots of cool stuff at Amazon for shelfs: