Non-tungsten, non-toxic car

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DCDAD
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Non-tungsten, non-toxic car

Post by DCDAD » Fri Apr 12, 2019 10:47 am

Thought I'd share a rough concept car that could be built by a cub scout that doesn't have $20 to burn on 4oz of tungsten and who also would like to avoid exposure to lead. Depending on the pack, some boys might really appreciate the option to build on a budget.

The car uses pennies for weight, which offer the best weight to value ratio of any US coin, and are conveniently .75 inches in diameter. Other US coins are odd sizes, probably related to the historical value of silver. Pennies also come in two different flavors, pre-1982 and 1982-. They are the same size, but the earlier coins are almost 25% heavier, being mostly copper as opposed to the later coins which are mostly zinc. About 30 pennies will fit across the 1.75'' pinewood body and will weight between 2.6 and 3.2oz depending on the mix of pre-'82 pennies included. BTW, there are still plenty of pre-82 pennies in circulation - a random sampling from my sofa turned up 6 among 32 pennies. :)

Anyway, the rough cut body below weighs 37g, but as the saying goes, "still has enough wood in it to build a sailboat". I think it would be pretty easy to get the body weight down <25g with two weight pockets for pennies so that cog can be tuned and, with proper axle and wheel prep + alignment, build a car that would be competitive in many packs. The only "extra" tool needed is a 3/4'' drill bit which is very common size and easily borrowed or purchased.
https://drive.google.com/file/d/0B_gLcb ... VdVRB/view



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Re: Non-tungsten, non-toxic car

Post by Speedster » Fri Apr 12, 2019 11:41 am

Hi there, DCDAD, Welcome to Derbytalk.
I'd like to offer my Penny build.

Use the long end for the front and drill a 3/4" hole behind the rear axle slot 1 1/2" deep as close to the bottom of the car that is safe. Drill a second hole as close to the rear axle slot and as close to the bottom 1" deep. Cut out a simple wedge without damaging the holes. Insert 20 pennies in rear hole and 13 pennies in front hole. Seal them up. Sand away the wood over the pennies. No part of the car will be higher then 7/8". You can drill out bottom wood if you like but it's not really necessary. This set up will give you a COG of 1" in front of the rear axle slot and a weight very close to 141.75 grams. If you're a little over there's some wood you can drill out.

That would be a Fun race. Everyone build a Penny car.



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Re: Non-tungsten, non-toxic car

Post by DCDAD » Fri Apr 12, 2019 12:04 pm

Excellent! Although the local pack runs the derby near Presidents' day weekend, so I would leave Mr. Lincoln visible.



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Re: Non-tungsten, non-toxic car

Post by Speedster » Fri Apr 12, 2019 1:11 pm

Good Idea. One of those bright, shiney new ones.



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Re: Non-tungsten, non-toxic car

Post by Darin McGrew » Fri Apr 12, 2019 1:19 pm

DCDAD wrote:
Fri Apr 12, 2019 10:47 am
BTW, there are still plenty of pre-82 pennies in circulation - a random sampling from my sofa turned up 6 among 32 pennies. :)
Another BTW, those pre-82 pennies work better in souvenir penny presses than the modern pennies that are copper-plated zinc.

But yes, pennies are easy to use, easy to find, inexpensive, and non-toxic, which makes them a pretty good weight for derby cars.



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Re: Non-tungsten, non-toxic car

Post by Eagle » Fri Apr 12, 2019 4:56 pm

I wonder how many roles of pennies it would take to come up to weight on a Big Rig. Might be kind of cool to make them the cargo. Maybe a logging truck.



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Re: Non-tungsten, non-toxic car

Post by DCDAD » Fri Apr 12, 2019 5:26 pm

Or maybe a brinks armored car...



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Re: Non-tungsten, non-toxic car

Post by Vitamin K » Sun Apr 14, 2019 2:47 pm

Maybe slightly more expensive, but you can also use nickels if you have a forstner bit and a drill press. :)



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Re: Non-tungsten, non-toxic car

Post by DCDAD » Mon Apr 15, 2019 7:11 am

Vitamin K wrote:
Sun Apr 14, 2019 2:47 pm
Maybe slightly more expensive, but you can also use nickels if you have a forstner bit and a drill press. :)
Yeah, but nickels, at .835, are an odd size - in between 53/64 and 27/32. Pennies are a nice, even .75 :)



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Re: Non-tungsten, non-toxic car

Post by whodathunkit » Mon Apr 15, 2019 6:49 pm

Eagle wrote:
Fri Apr 12, 2019 4:56 pm
I wonder how many roles of pennies it would take to come up to weight on a Big Rig. Might be kind of cool to make them the cargo. Maybe a logging truck.
Today's penny weighs 2.5 grams .. 100 of them = 250 grams .. or = to 8.81 ounce 11.3 pennies per ounce.
50 pennies per a roll.. 6 rolls of pennies would be 250 pennies at 26.43 ounce.


What type of automobile can be spelled the same forwards & backwards?

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Re: Non-tungsten, non-toxic car

Post by Speedster » Tue Apr 16, 2019 5:22 am

I realize it's a typo because the answer is correct. 6 rolls of pennies would be 300 pennies.

I know I'm Off Topic again but this is Derbytalk and I have learned so much the past 7 years from Derbytalk. Regarding trucks, I owe a lot to Whoda.
My opinion only, pennies are not dense enough and would make a very poor choice for a truck. Any weight that is put in front of the rear axle puts more weight on the dfw and that's not good. My opinion only.



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Re: Non-tungsten, non-toxic car

Post by Eagle » Tue Apr 16, 2019 12:51 pm

Speedster: Pretty sure whodathunkit, being the super cool guy that he is, was just answering my question.

I've gotta say $3.00 wouldn't even cover the shipping for the weight. So, there is some appeal there.

But, your statement "Any weight that is put in front of the rear axle puts more weight on the dfw and that's not good" has me questioning:

where do you place your rear axle?

How tall is your rig at the rear axle?

At what point is giving up all the aero to get the weight behind the rear axle counter productive?

Do I need to build another rig?

I'm not as quick building as whoda, so these tips will likely have to be applied to next years build(s).



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Re: Non-tungsten, non-toxic car

Post by Speedster » Tue Apr 16, 2019 2:43 pm

I was referring to the line - 6 rolls of pennies would be 250 pennies.

I'll try to answer you as best I can at this stage of my education. I'm looking forward to starting another Topic hopefully in June.

Rear axle is 1 5/8" from rear of truck. Bottom of board is angled as much as I could to clear the curve of the best track.
Height at rear is 1 1/2". That area holds 6 - 2 ounce blocks (12 ounces). no weight added in front of rear axle. Truck weighs 8 ounces without added weight. Presently 20 ounces and there will be one more plate added that will weigh about 2 ounces.
Aerodynamics is not very important. What the Aerodynamics weighs is what is important. Because of the minimum length (17") you are going to have a lot of weight in front (probably). No matter how you try to tune the truck if the front is heavy (7 ounces) the Dfw is going to go into the rail hard. I will learn more this summer and am eagerly looking forward to it.

No, don't build another rig. Whatever happens it will be a very educational experience. Whatever you do make certain your front and rear wheels are close enough to the ends of the truck so the truck clears the Best track curve without hitting it.
See you at the races.



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Re: Non-tungsten, non-toxic car

Post by Eagle » Tue Apr 16, 2019 3:08 pm

I don't have a track or a piece of curve to check. So, It's all guess work on my end. Thanks for the follow up.

2 oz tungsten blocks. Where did you find those? What are they like 1" cubes ?



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Re: Non-tungsten, non-toxic car

Post by Speedster » Tue Apr 16, 2019 5:45 pm

I originally got these from Maximum Velocity but they do not show them anymore. You can get them from Derby Evolution. I should have called them "bars".
They measure 1/4" x 1/2" by 1 1/2". They do not reach my rear axle by 1/8". Originally I needed to move the rear axle forward to get what I needed. Fortunately the very rear of the truck clears the curve.
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