Turtle Race

[pwrd by tungsten]

Here is a picture of a car I made for a turtle race. It was not slow enough...

Raw BSA wheels and axles. Under weight with a pinwheel on top...

[millettbbc]

love the rock. Never thought about using a rock for weight.

[Pinewood Daddy]

I would try a parachute or sail, something that would consistently cause drag. I made on slow car that drove all 4 wheels hard into the body. The only problem with that is the friction may not always be consistent as the wheels "burrow" into the body.

What about a electric propeller car running in reverse??

I'm thinking a well prepped car weighing about 1 ounce with a consistent amount of air drag could be adjusted to barely finish a 32 foot race. The key is good wheel & axle prep with excellent alignment to keep the car running straight with minimal rolling resistance. Then adjust the air drag to consistently just barely finish. Kind of like making a fast car in reverse!!

[pwrd by tungsten]

That would have done it. The prop looked cool but once it gets spinning it does not add much to resistance...

[drathbun]

That would have done it. The prop looked cool but once it gets spinning it does not add much to resistance...

I know this is an older topic, sorry. But I am trying to catch up on several years of missed reading. If I'm understanding this concept correctly, the goal is to have a car that finishes the race, but in the slowest possible time? And in this case, the pinwheel was designed to provide a braking effect? In that case, perhaps gluing the pinwheel so that it doesn't turn at all would have helped. It would act more like a sail in that case.

[5kidsracing]

The flapper method seems very effective for turtle cars Dave...



Except when you crash....


https://youtu.be/

[drathbun]

Those races look awesome!

[5kidsracing]

Turtle cars are different builds on many levels. There are many ways to go at it and be effective. In my case I used the flap to slow the car down which works like a charm, but then if your wheels had too much friction you wouldn't make it to the end. That car was a rialrider and used razor wheels. If I used standard BSA type wheels there was far too much friction in the wheels themselves to keep it going down the track. You also had to position the flap so that when it opened it pulled the fdw wheel into the rail. The flap had to be cut just right so that happened. I tried large flaps, small flaps, different cut flaps, etc... but it all came down to tuning and consistency.

[Duane]

If wheel mods are allowed, it would be good to put most of the car's metal weight into a pair of the BSA wheels, just inside the tread. That would divert a third or so of the car's kinetic energy into the wheels' angular momentum, where it then sustains the slowed forward motion despite air drag.

The braking is needed on the downhill, to prevent buildup of speed. Air brakes are one easy way to do that. I'm wondering if there is some mechanical way to do braking, triggered by the current slope of the track. Adjust the trigger so that the car runs normally once it gets halfway or so through the transition curve. But would be embarrassing if the car never leaves the start pin. Can the throat of the air brake be opened by the car's angle?

[5kidsracing]

If wheel mods are allowed, it would be good to put most of the car's metal weight into a pair of the BSA wheels, just inside the tread. That would divert a third or so of the car's kinetic energy into the wheels' angular momentum, where it then sustains the slowed forward motion despite air drag.

The braking is needed on the downhill, to prevent buildup of speed. Air brakes are one easy way to do that. I'm wondering if there is some mechanical way to do braking, triggered by the current slope of the track. Adjust the trigger so that the car runs normally once it gets halfway or so through the transition curve. But would be embarrassing if the car never leaves the start pin. Can the throat of the air brake be opened by the car's angle?

Great idea! and that was my thoughts on my first attempt also... I machined the ID of BSA wheels and placed tungsten rings in the wheels. This concept worked very well, but it wasn't slower than my flapper car.

As far as mechanical breaks that is also a good idea... Some other racers used their flappers not only to catch the air and slow the car, but as the flapper rose up the rear of the flapper had extensions that contacted the rear wheels. This mechanically pushed on the rear wheels like brakes. This concept worked well.

With the flapper concept it was all about when the flapper came up and came down. Changing the amount the flapper could rise up, by use of a hard stop, you can control how quick it came down. A larger flapper would come up earlier, but also create the largest jolt when it hit the hard stop.

I had a version where I counterbalanced the flapper such that when you tilted the car and placed it on the starting gate the flapper would rise up about half way. This made the flapper come up way earlier which was good, but because of the counterweight the flapper was not stable and bounced up and down as it went down the track.

Weight placement was tricky as well.... You had to have enough weight on the fdw to keep the front end down, but a little too much and the car slowed way too quickly and didn't make the end. This was because the car was a railrunner and more weight on the fdw made more friction against the center rail.

[drathbun]

It almost sounds like this concept (turtle cars) is harder than fast cars! Anyone can make a slow car, but making a slow car that will finish the race has to present some interesting challenges. I'm definitely going to suggest this as an option for our outlaw race next year.

[5kidsracing]

It almost sounds like this concept (turtle cars) is harder than fast cars! Anyone can make a slow car, but making a slow car that will finish the race has to present some interesting challenges. I'm definitely going to suggest this as an option for our outlaw race next year.

It was definatley harder! I think for a Scout race if you made it for "single slowest run" and not "average" it would be a ton of fun and it could be anybody's race. It wasn't too hard to get a car to go slow and have a perfect slow time once in awhile. A perfect slow time would be 9.999 on most timers. It was hard to do it 3, 6, or whatever times in a row and get the high average. With this race you could have a scout car that is a non railrunner that bounces back and forth all the way down be the winner!

[rpcarpe]

I've considered these as well... I like the Fast Race for the kids, but IMO a Turtle Race is perfect for adults.
That way the greater effort hopefully goes into the Cub cars, and the adults racers don't outshine the real stars of the event.

[whodathunkit]

I've considered these as well... I like the Fast Race for the kids, but IMO a Turtle Race is perfect for adults.
That way the greater effort hopefully goes into the Cub cars, and the adults racers don't outshine the real stars of the event.