1/24 3D Printed Sprint Cars

[Halfj-7]

Thought I'd share my Dad and my winter project. Dad picked up two different styles of 3D printed sprints from a really talented dude named Woodguy over on Shapeways. We went with H&R Jackrabbit 14K motors, 9/27 gearing, H&R guides and learned how to make my own tires cast from model car "modifieds" tires on H&R or Pro-Track wheels.







Close ups of the two bodies styles that were available at the time







Running them at 12V and doing 3.1 second avg lap on my 4-lane 7' x 16' routed oval Long Creek Speedway. They shine on the inside lane, and you real have to "handle" them on the outside lane. I recently started to switch from silicone to Urethane tires and I don't have alot of rubberlaid down yet. Fairly stable cars, but when they crash, its pretty realistic...
More pics to come

[Halfj-7]

Underneath pics







Close up of driver. Just enough detail to suit me. The bodies could use more sanding to get the roughness out but with 16 cars and we really wanted to get racing...its good enough.



And this crash started somewhere on the back stretch

[slothead]

Your track surface looks similar to my oval - Masonite, also known as hardboard. Silicone tires work best for me, and the wide silicone over foam Daytona Stockers from Pro Track provide amazing traction.



These are 1/24th scale wheels and tires from Professor Motor's website.

Anyone know if these 3D cars are available in 1/32 scale?

Slothead

[tjettom]

Say there, Great set up...very inspiring. I have had my eye on those Woodguy printed sprint cars too! Say...are you running your motors in reverse for traction/handling purposes? I'm just curious I suppose? Slothead... Yes,I do believe (without checking though) they offer some in 1/32 scale. They sell em on Shapeways...
Regards,
Tom

[oldspark]

Those are super nice with plenty of detail for me also, buy the time you purchase all the parts they are not all that cheap (is anything anymore). You have a real nice field of cars there.

[HomeRacingWorld]

This is pretty impressive. No...VERY impressive work.

You have a great field of cars. Congratulations on the project. I really like how you chose a milder, more realistic speed motor. Too many times all I see are 40K or above with foams and spray glue commercial style.

Good to see it home racing style! :music-rockout:

[Halfj-7]

We picked the lowest rpm H&R motor last year for my dads old jalopy cars on good ol H&R adjustable chassis so picked those again. And plenty peppy at 12V. I tried something a little different with the tires by barely sanding them on the tire razor, just enough to contact patch left and keep some of the tread for looks. It lets them slip around just enough. I found that i can tune the slower cars with another trip thru the razor to get lap times closer to the faster cars.

[HomeRacingWorld]

Well nice work. I am stealing a photo if it’s ok sir?

[tjettom]

Say...I'll ask again...why are you running your motors in reverse? for traction/handling purposes?
Tom

[TuscoTodd]

That is one cool looking field of fun!

[Jesla]

[slothead]

Regarding running the motors in 'reverse', I guess he means that in the setup used for these cars, if you look at the motor from the pinion gear end, it has to turn counter clockwise for the car to go forward. While I must admit I never paid much attention to this, if you look at (most?) inline chassis cars from the rear the crown gear is on the right rear tire side of the rear axle, meaning the motor turns clockwise to make the car go forward.

It never really occurred to me that there's a difference between an electric motor turning clockwise or counter clockwise. If I bought or built a car that went backwards when put on the track I'd just reverse the wires at the guide.

Slothead

[chappyman66]

"Forward and reverse" are sort of a misnomer with electric motors. They run in both directions depending on the polarity of the leads.

It is true that some motors run faster in one direction than the other. Typically this is the result of the commutator being twisted in one direction relative to the windings of the motor. Theoretically if the comm is perfectly centered between the windings and all windings are equal, there shouldn't be any difference. This rarely happens though.

It should also be pointed out that "can drive" vs "end bell drive" may refer to forward and reverse. In this case, I would suspect that the motors are mounted in the can drive orientation simply because that's the easiest hole to design for a 3D printed motor mount. The D shaped hole for most end bells is slightly more difficult to design although it's not really a problem. The smaller can drive hole also allows the mounting plate to be stronger (smaller hole = more material remaining).
Very frankly....kudos to the designer for printing a function car. That's cool all by itself.

Not to mention being able to directly scale it down to 1/32 if desired.

I am impressed.

[tjettom]

The motor as well as most all slot car motors have timed commutators to help with higher rpm. With running them backwards they are running significantly retarded thus being slow. On a neutral timed motor there would be no difference but on most slot car motors not so.

[Halfj-7]

Well to be totally honest here, I really dont know enough to pay much attention to which side the gear is on. I know when I built the first one, I had a brass chassis sprint car I bought on the work bench to compare wheel spacing and stance. Imagine I copied which side the spur was on too.
I thought ya meant why did I put the motor in upside down.
Thanks for the discussions above, I learnt something new today.