Using the Shopbot to create a C02 Dragster

[khuffman]

Hi,
I am just learning how to use the shopbot and was wondering if anyone out there has tried to use the shopbot to create a CO2 dragster (like a shell car)?

[Brady Watson]

Kora,
I'm sure that you could make a dragster on the Bot if you have a drawing. Links to CO2 dragsters in question would be helpful.

-B

[jseiler]

I bet its something like this...

http://www.science-of-speed.com/building.asp?id=33

Looks like a fairly tough project for someone just learning. Got any 3d design experience, Kora?

[bryan]

This project really makes me feel old, as I remember bandsawing and a lot of hand sanding back in 8th grade shop class some 32 years ago, man what I could have done with my bot;-) I may not have won the race but my car would have been hot.

[wiese]

If you have Rhinoceros, you may want to check out this tutorial. http://www2.rhino3d.com/resources/display.asp?language=en&listing=728

[khuffman]

Thanks to all!
John, yes you are in the right place, this link in particular will get you a specific example of a shell car.
http://science-of-speed.com/building.asp?id=215 I have also attached the file that I created using VCarve Pro. I would appreciate any specific siggestions you might have as to different approaches to try. For this file, I am using a 1/4" end mill and each vector is a speparate shopbot cutting path. Is there a way to combine several saved toolpaths into one shopbot file.




Dragster file

3670 (45.1 k)

[ryan_slaback]

Kora, You can combine the toolpaths into one file so long as they use the same bit. When saving the toolpaths in VCarve there is a box that you can check that says combine toolpaths into one file or something like that.

Also, make sure you drill the axle holes before you machine the car. There is no way whatsoever that you will accurately drill the holes after the shell has been created.

I would not cut your file as you have it toolpathed currently. The first cuts that I saw appear to be cut on vectors and go multiple depths working from the outside in. The problem with this is that when you get to the center cuts the wood won't be strong enough (especially since it is balsa) and will break due to the side force of the cutting bit. Instead you should program it to cut as a series of pockets. That will cut one depth from outside to inside and then go a bit deeper from outside to inside until it is at your final depth. It also will make it take a whole lot less toolpaths.

I also noticed from the looks of things, you are planning on putting the rear wheels on the outside of the car. If you sand them down a bit to the minimum width, they will fit on the inside of the car with just enough body left to hold the axle and just enough space between them to run the string through. Makes it that much more aerodynamic.

P.S. If you ever race against one of my students, I didn't tell you anything.

[khuffman]

Ryan,
Thanks for the input. I will keep it "Top Secret." We are in WY, so the chances are probably slim that we would face each other
.
I attached a picture of the "prototype" I used basswood. I am not sure what you mean in terms of cutting pockets. Also, all wheels will be inside, or at least that is the overall intent.



3671

[ryan_slaback]

Kora,
What I meant by pockets is that rather than cutting lots of single cuts around and around deeper and deeper and then moving in a bit and doing the same thing the way yours cut, it would cut the whole area and then go down and cut the whole area and go down etc...

However, if you already cut a prototype of it and nothing broke out I guess you can disregard that bit of advice.

[khuffman]

Ryan,
I appreciate your input as this took awhile. I will try it and let you know how it turns out. Thanks again, Kora

[wendell]

We've cut some cars but have always struggled with fixtures. A friend of mine in Ohio had a fixture sold with another CNC (Techno I think?) that I'd planned to copy but I relocated to Georgia and never followed up.
We did cut parts of cars but never really did any 3d work. We own Solid Works and plan to do cars soon. I'll try to send a picture of how we approached the project soon.

[khuffman]

Hi Wendell,
I am curious to know if you have done any of the Solid Works C02 cars that you referenced above? I have kind of looked into the F1 in schools challenge and it seems as a practical application of the shopbot in a school although may be very difficult with my current level of skills and abilities!

[matt_zawlocki]

We will be making the conversion from AutoCAD LT to Solidworks next school year. Did any of these projects turn out? We have a lot of car blanks in storage and this looks like a cool idea.

Matt

[khuffman]

Matt,
I am no further than what is posted here. Kinda had to walk away for awhile. Have you pursued anything yet?