New builder needing help

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
Singledad2019
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New builder needing help

Post by Singledad2019 » Mon Nov 18, 2019 6:22 pm

We build a 3.5 ounce car that ran better than any of our 5 ounce cars. All the car had good alignment and weight place. The 3.5 ounce car had 1 ounce behind rear wheels - stock location, and 1/2 ounce right behind the 1 inch point in front of the axle. There is 5 inch between the wheels. All of them where wedge cars with weight removed from front. It blows my mind. I'll take pic tonight.
https://m.facebook.com/story.php?story_ ... 7244613760
Last edited by Singledad2019 on Tue Nov 19, 2019 11:26 am, edited 1 time in total.



Speedster
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Re: New builder needing help

Post by Speedster » Tue Nov 19, 2019 10:51 am

Welcome to Derbytalk, Singledad2019
I'm looking forward to seeing a picture of the car and hearing from you.
We all know we can't break the Laws of Physics and speed is all about Physics. With that wheelbase I'm wondering if you are racing scouts? I would recommend you buy Troy Thorne's 2013 book, Build a Winning Pinewood Derby Car. It can be purchased from Fox Chapel Publishing.

I surely am eager to hear from you and I suspect so are a lot of other folks on Derbytalk. We're here to help.



Singledad2019
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Re: New builder needing help

Post by Singledad2019 » Tue Nov 19, 2019 11:30 am

https://m.facebook.com/story.php?story_ ... 7244613760
This the track that it ran on. That is a different car in video



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Re: New builder needing help

Post by Speedster » Tue Nov 19, 2019 2:40 pm

Does the track have a timer that shows Elapsed Time?

Just for fun, put two 1/2 ounce tungsten plates directly behind the rear axle slot and one 1/2 ounce tungsten plate in front of the rear axle slot. Keep the balance point close to 1" in front of the rear axle slot. Race it first against another car the way it is and then race it again against the same car after you add the weight. What happens?

Tell us exactly what you did in building that car.
I see it has an extended wheelbase.
3 wheeler?
Railriding?
Cant on rears?
Cant on DOM? (Dominant front wheel)
Novus 2 for bore Polish?
Stock wheels?
Stock BSA axles?
Graphite only?
Oil only?
If railriding, does it drift 2" in 4' to start?
Do you cover all the holes with Packing tape or some other product?
Do you buy wheels from a vendor so you get (almost) round ones?

What did I forget?



Singledad2019
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Re: New builder needing help

Post by Singledad2019 » Wed Nov 20, 2019 2:03 am

It is a scout car. I guess I'm trying to make sense of all this. This is only the 3rd car we are building. My son first car got build though a workshop our pack does. Basically, they told us what to bring. When we got there, a gentleman was assigned to help us build the car. They had all the tools and stuff already set up. I did most of the work, but my son did get to do some of it. We build a wedge car with axle slightly back from the orginal spot - in rear. The front was slightly ahead of the orginal spot. The car had 2 ounces behind the rear axle - four 1/2 screw in weights. Right behind 1 inch in front of the axle was 1 ounce of weight - two 1/2 ounce screw in weights. That year, they allowed one wheel up. So we (or I) would get to use all the tools, they made us curve the sides of it. We drilled holes into the front of the car, where similar to the ones in pic, and then top and bottom where covered with thin wood strip. It ran 24th in a field of 56 at the scout race. They claimed we only ran 138 scale miles per hour.
The next year we build a very similar car at the house. I was told we ran poorly due to the curved sides. We build the 2nd car with straight sides. Basically, I got the pre cut wedge body from the scout store and weights from a local hobby shop. We used the wheels and axles that the scout store sells. They changed the one wheel up rule, so we never got to run the car. I couldn't get all 4 tires to touch to save my life. I asked for help, and no was willing to help me get them to touch.
I found the track on craigslist for $160. It is 32 foot wood track. I have a timer for it. However, it will not work with any of the program we tried to use. So basically I only get to know first, second, third, and fourth. We want to really get back to the basics of building these cars. Apparently, everyone agrees that you should try to eliminate as much weight from the front as possible. We used just a regular cordless drill to make the holes. The block was weighted before we drilled it. I want to say the was only .30 ounce difference. We already had those weights here at the house, so we just tossed them on.
I heard you are supposed to run cars together on track during testing to get accurate data. We decided to run the 2 cars we had already build. It beat the first car we build ( we call it green wheels) by atleast 2 car lengths. The 2nd car ( we call it white wheels) we build by 1/2 a car lenght. I was completely shocked that this happened. I had a 1/2 bar right behind the one inch point in front of the axle, and one ounce behind the rear axle.
Adding weight to the behind the axle did seem to speed it up much. When I taped on a one ounce pinecar bar just behind the inch point in front of the axle, it seemed to be much faster. This also confused. As I always heard bulk of weight in back.



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Re: New builder needing help

Post by Speedster » Wed Nov 20, 2019 4:06 pm

It surprises me you' re allowed to have an extended wheel base but they put the "4 on the ground" rule back. That's disappointing.
Please check your email



Singledad2019
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Re: New builder needing help

Post by Singledad2019 » Wed Nov 20, 2019 6:44 pm

My understanding of it was that they had been having too many "shabby" cars in their events, and this was their way of getting rid of the entry level builder. They where disappointed that people where coming with pre cut or what they call store buy cars. They want to keep their average car speed number up, and times ran between first and last place. The pack leader owns the track, and he rents it out. I guess he wants numbers he can brag about. His kids do get to run in the events for a spot. Which I think isn't right. They have better access and knowledge of the track then we do.



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Re: New builder needing help

Post by whodathunkit » Wed Nov 20, 2019 7:17 pm

Noted: your car has what looks to be the newer style electric blue wheels on it

If your last 2 test cars had the older black style wheels on them..
I wounder if the newer style wheels had anything to do with the improved times you were seeing out of the car as well.. as far as better wheel molds go.

Less weight is less friction as well.


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

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Re: New builder needing help

Post by Speedster » Wed Nov 20, 2019 9:15 pm

Could you please get us a copy of your rules?



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Re: New builder needing help

Post by Loud2ns » Wed Nov 20, 2019 9:34 pm


Singledad2019 wrote:My understanding of it was that they had been having too many "shabby" cars in their events, and this was their way of getting rid of the entry level builder. They where disappointed that people where coming with pre cut or what they call store buy cars. They want to keep their average car speed number up, and times ran between first and last place. The pack leader owns the track, and he rents it out. I guess he wants numbers he can brag about. His kids do get to run in the events for a spot. Which I think isn't right. They have better access and knowledge of the track then we do.
I would be learning all I could to help my kids dominate. A place that I've directed poeple to for studying is 5kidsracing site(https://5kidsracing.webs.com/cubscoutbuildtips.htm).
A couple of things on your car: you need to bring it up to 5 oz......anything less is leaving speed on the table. Leaving 1.5 oz off is alot of horsepower lost.
I would recomend covering the holes with clear packing tape(unless your scout insist on keeping them open). All those holes are like little wind drags.


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Singledad2019
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Re: New builder needing help

Post by Singledad2019 » Wed Nov 20, 2019 9:38 pm

I'm still waiting on new rules for this year. I ended up putting a slug style weight 1/2 ounce and two .20 weights 1 inch in front of rear axle. Front had roughly 1.4 ounce on it. I ended a slug style 1/2 ounce weight behind rear axle. It is noticable quicker. I'm going to start looking for issue with the other cars. Wish I could figure out how to hook timer up to computer to get real numbers. Do you think the holes should be covered?



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Re: New builder needing help

Post by Loud2ns » Wed Nov 20, 2019 11:00 pm

I think it would help some. I wouldn't force my kid to cover them if they didn't want to, however I would recomend it. I like the look of see through, yet I cover my voids. Here are a couple of pics of my fastest car.ImageImage

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Singledad2019
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Re: New builder needing help

Post by Singledad2019 » Thu Nov 21, 2019 2:27 am

That car looks amazing! This weekend we are going to build one with hole like that. I would think the one large hole works better than all the small holes. To make it a apples to apples comparison, we are going to use the wedge style body. I figure we will make 2 cars this weekend. One that is just the weights - non altered front and one with a one large hole. We'll all weight them the same, and see what happens. I'm all about find out what is going to work best.



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Re: New builder needing help

Post by Speedster » Thu Nov 21, 2019 12:48 pm

Loud2ns, what type and shape weight will you use to weight the car, how much weight behind the rear axle slot, and what COM are you striving for?



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Re: New builder needing help

Post by Loud2ns » Thu Nov 21, 2019 3:51 pm


Singledad2019 wrote:That car looks amazing! This weekend we are going to build one with hole like that. I would think the one large hole works better than all the small holes. To make it a apples to apples comparison, we are going to use the wedge style body. I figure we will make 2 cars this weekend. One that is just the weights - non altered front and one with a one large hole. We'll all weight them the same, and see what happens. I'm all about find out what is going to work best.
Thanks for the compliment. Keep in mind that this is one of my pro cars. I would never have my kids build one like that because it's too fragile(just wanted to illustrate covering the voids). The advantage to having the smaller (covered) holes verses one big hole is that you maintain the rigidity in the car which is good for speed and possible rough handling! What kind of weights are you using? If you are going to build new cars this weekend you should try following a 5kids layout. imo

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