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Pinewood derby cars

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Project by tynewman posted 04-01-2022 03:18 AM 487 views 0 times favorited 12 comments Add to Favorites Watch

We have a pinewood derby coming up and I wanted to see what I could do with the new CNC. Mostly I made then for other adult leaders that aren’t racing, but couldn’t resist cutting out a couple for my kids too. Don’t now that they will be the fastest, but should turn some heads.

-- Ty





12 comments so far

View Underdog's profile

Underdog

1917 posts in 3526 days


#1 posted 04-01-2022 10:52 AM

Oh those are fun!
Where did you get your models?

-- Jim, Georgia, USA

View Eric's profile

Eric

5695 posts in 1363 days


#2 posted 04-01-2022 11:24 AM

Some slick designs. Without the wheels they might not be the fastest.
Well done.

-- Eric, building the dream. the "Loft"

View DanHalka's profile

DanHalka

24 posts in 97 days


#3 posted 04-01-2022 01:15 PM

man, computer assist must make for some competitive derby meets, these days. great looking bodywork! remember, put the weight in the bottom back!

View tynewman's profile

tynewman

240 posts in 1202 days


#4 posted 04-01-2022 02:37 PM

I got the models from thingiverse.
Then I go to this website.
https://fenrus75.github.io/FenrusCNCtools/javascript/stl2png.html
It converts the stl into a grayscale image that Carbide Create pro can use to carve the cars.
To get all the angles I pull it into sketch up, turn it, then re-save it. A lot of trial and error to figure out carving from multiple directions.

-- Ty

View LittleBlackDuck's profile

LittleBlackDuck

9454 posts in 2311 days


#5 posted 04-01-2022 08:27 PM

They’ve come up quite well… shame you haven done some ”wheelies”.


I got the models from thingiverse.
Then I go to this website.
https://fenrus75.github.io/FenrusCNCtools/javascript/stl2png.html
It converts the stl into a grayscale image that Carbide Create pro can use to carve the cars.
To get all the angles I pull it into sketch up, turn it, then re-save it. A lot of trial and error to figure out carving from multiple directions.

- tynewman


People tend to forget the effort required to get a CNC to generate more than sawdust. Most people thing you just push a button and out pops a wonderful creation.
Even if you plagiarise the basic design, there can be significant effort required to fine tune it… just like the traditionalists can do a ”dovetail” or do a Dovetail!

-- If your first cut is too short... Take the second cut from the longer end... LBD

View tynewman's profile

tynewman

240 posts in 1202 days


#6 posted 04-01-2022 08:54 PM

Definitely! Each of these cars will have more time put into them the the ones the kids are making. The tool makes a difference in the final product, but its a lot of work to get them to that point

-- Ty

View Woodmaster1's profile

Woodmaster1

1987 posts in 4077 days


#7 posted 04-04-2022 11:16 PM

When I taught high school engineering design one of my projects was a 3D printed derby car. They had design a compartment with a hatch they could open and put weights in. You wouldn’t believe some of designs. Awesome job on th cnc cars.

View Dark_Lightning's profile

Dark_Lightning

5113 posts in 4599 days


#8 posted 04-05-2022 02:31 AM


man, computer assist must make for some competitive derby meets, these days. great looking bodywork! remember, put the weight in the bottom back!

- DanHalka


The weight should be as high as possible in the vehicle. From top to bottom, depending on the height, it’s good for a millisecond or two. On a fast track, 8 msec is a little over a car length, so it pays to place the weight properly.

In the article you linked, he talks about having the weight to one side, but what he doesn’t say is that it should be opposite the front wheel that is mounted so that it doesn’t touch the track. There is less rolling resistance and one less wheel’s worth of friction at the axle.

-- Steven.......Random Orbital Nailer

View tynewman's profile

tynewman

240 posts in 1202 days


#9 posted 04-06-2022 12:38 PM

I love all the strategy talk. When my boys where in cub scouts I did all the research and we… they took first place every year. This time we are doing it with all the youth in our church, both boys and girls 12-18. We will still be polishing axels, but we are trying to have more fun.

-- Ty

View Dark_Lightning's profile

Dark_Lightning

5113 posts in 4599 days


#10 posted 04-06-2022 03:02 PM

Those are some nice cars! I though about building a fat-fender Ford style, but never got around to it.

Heh, our company had a pinewood derby as a fundraiser for cancer. We got kits and were allowed to modify as desired, using only kit parts. I had access to a mill and lathe, so I machined the wheels for minimum moment of inertia. I knew to keep one wheel off the ground, but hadn’t learned about rail riding until later. I took first place, and there was some grumbling about cheating, but the guy running it pointed out that it had all the kit parts, so was not cheating. My car is the yellow one in the middle, with .080” thick wheels and 10 holes per wheel. Second place is the near car, also with machined wheels. It was entered by a guy who worked in one of the machine shops. I won by 6 milliseconds.

-- Steven.......Random Orbital Nailer

View awsum55's profile

awsum55

1315 posts in 1999 days


#11 posted 04-07-2022 05:26 PM

Pinewood Derby was some of the most fun I had with my son. We won something every year and one year we won everything possible. Sorry, I know I’m bragging, but I can’t help it.

-- "The Answer Is Blowin'n In The Wind" John D, OP, KS

View Dark_Lightning's profile

Dark_Lightning

5113 posts in 4599 days


#12 posted 04-07-2022 05:51 PM

Funny story- Me eldest son when he was a Wolf Cub Scout, built a PWD car unassisted by me. Paintbrush into the ferrule on the body, etc. Grandma helped him lop off some of the wood. No axle polishing, even. One of his den buddies’ dad made a car where he worked. I don’t know what all he did for speed, but it was painted and polished and looked like a block of obsidian. That car beat my son’s car by about a centimeter. The kid just stood there picking his nose, as he had had nothing to do with it. My son was jumping out of his skin, practically, over second place. One thing I’ve found over the years is that some are just fast out of the box.

-- Steven.......Random Orbital Nailer

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