Hello brand new here.

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
Sleestak
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Re: Hello brand new here.

Post by Sleestak » Fri Jan 11, 2019 11:09 am

Speedster I have no idea what your talking about. Is this guy a bit?

There must be one step that shaves off the most inches off the finish line.

Anyone else other than speedster?

Thanks for your help speedster. I do not want to purchase any of your items nor mail you a check for any items you are pushing. Please stop emailing me. Thank you.



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Darin McGrew
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Re: Hello brand new here.

Post by Darin McGrew » Fri Jan 11, 2019 11:22 am

Sleestak wrote:
Fri Jan 11, 2019 5:43 am
My question is.......should I use oil at a derby most every other car is full of graphite? I hear mixing the 2 is a big no no. I except the track to have some dust on it.
Thinking outside the box, what would happen if you provided Krytox (or some other derby-appropriate oil) at your group's workshops, and encouraged everyone to use it instead of graphite?
Sleestak wrote:
Fri Jan 11, 2019 9:58 am
Question. What is the single ONE most thing a guy can do that affects the speed of the car?
Your car's performance is not determined by the thing you do best. It is determined by the thing(s) you do worst. A derby car starts with a certain amount of potential energy at the starting gate. By the end of the race, some of that potential energy has been converted into kinetic energy (forward motion) and the rest has been wasted (friction, heat, etc.). It's like trying to carry water in a bucket with holes in it. The water is going to leak out of the biggest holes faster, so you need to patch them first.

Anyway, when I give my intro talk at the beginning of derby season, I tell the kids that the most important things they can do are
  • straight wheels and axles (use the drill press before cutting the block),
  • polish and lubricate the axles, and
  • add weight to bring the car up to the 5-ounce limit.



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Re: Hello brand new here.

Post by Speedster » Fri Jan 11, 2019 11:26 am

OK Tim. Will Do. I wish you the Very Best.
Bill



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Re: Hello brand new here.

Post by Vitamin K » Fri Jan 11, 2019 11:52 am

Here's my takes:
1. Rules state oil is allowed. My question is should I use oil on a track where most of the other cars will be using graphite? If the car makes several runs I dont want graphite dust getting in my oil
tires. Should I just use graphite?
My kids have run oil at Derbies full of graphite-running cars. Never had a problem with the bores getting dirty. If I were running multiple races (e.g., pack level, then districts), I might consider cleaning the bores between races, but I might not (I am lazy).

If you can run oil, definitely run oil. It will almost always be faster. Learn good bore prep and find a good sealant to use in combo with the oil. I recommend Max-Pro Heavy Duty Silicone spray, as it is non-toxic, locally available (for some) and can be used on both the axles and in the wheel bores.
Which front tire should be in the air? Having only 3 touch the track is allowed but need the 4th tire on the car. By doing this you lower the opposite side tire only with a toothpick? The back tires need no toothpicks?
It doesn't matter which front wheel you use. You don't need to mess with toothpicks. If you're using axle holes, drill the raised wheel hole a little higher. If you're using slots, use a saw blade to make the raised wheel slot a little deeper. Or just put enough bend in the raised wheel axle to lift it up. Don't overthink it. :)
With all the talk and effort to remove friction I'm stumped why one would want the cars tires to grind against the rail the whole way down to reduce wobble. And does one always want this or does it depend on the type of track? I need alot of work understanding this. To ride a rail do the front tires slant away from the car from the top of the tire like in a V pattern if looking from the front of the car? Or just 1 tire? What about the back? The opposite like an u side down V paterern if viewed from the rear.
It is impossible to run a car down the track without incurring friction losses due to the wheels touching the guidestrip. A properly aligned rail-guided car lets you do it on YOUR terms, not on the terms of random contact. The rear wheels contacting the rail are going to suck the most speed from the car, and a properly aligned rail-guided car keeps the rears off of the rail.

Also, if you have enough positive camber on your DFW (non-raised front wheel), the it will roll down the rail rather than slide against it.
Question. What is the single ONE most thing a guy can do that affects the speed of the car?

Or is someone wants to rank them that would be great.
Hmm, I would say:

1) Reduce friction in wheels and axles via proper polishing and lubrication
2) Properly align the car so that the wheels are all working in the same direction (possibly) using rail-guided techniques.
3) Maximize potential energy by moving the car's center-of-mass further up the hill. Obviously make sure the car weighs the full 5oz



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Re: Hello brand new here.

Post by Sleestak » Fri Jan 11, 2019 2:09 pm

Vitamin K wrote:
Fri Jan 11, 2019 11:52 am
Here's my takes:
1. Rules state oil is allowed. My question is should I use oil on a track where most of the other cars will be using graphite? If the car makes several runs I dont want graphite dust getting in my oil
tires. Should I just use graphite?
My kids have run oil at Derbies full of graphite-running cars. Never had a problem with the bores getting dirty. If I were running multiple races (e.g., pack level, then districts), I might consider cleaning the bores between races, but I might not (I am lazy).

If you can run oil, definitely run oil. It will almost always be faster. Learn good bore prep and find a good sealant to use in combo with the oil. I recommend Max-Pro Heavy Duty Silicone spray, as it is non-toxic, locally available (for some) and can be used on both the axles and in the wheel bores.
Which front tire should be in the air? Having only 3 touch the track is allowed but need the 4th tire on the car. By doing this you lower the opposite side tire only with a toothpick? The back tires need no toothpicks?
It doesn't matter which front wheel you use. You don't need to mess with toothpicks. If you're using axle holes, drill the raised wheel hole a little higher. If you're using slots, use a saw blade to make the raised wheel slot a little deeper. Or just put enough bend in the raised wheel axle to lift it up. Don't overthink it. :)
With all the talk and effort to remove friction I'm stumped why one would want the cars tires to grind against the rail the whole way down to reduce wobble. And does one always want this or does it depend on the type of track? I need alot of work understanding this. To ride a rail do the front tires slant away from the car from the top of the tire like in a V pattern if looking from the front of the car? Or just 1 tire? What about the back? The opposite like an u side down V paterern if viewed from the rear.
It is impossible to run a car down the track without incurring friction losses due to the wheels touching the guidestrip. A properly aligned rail-guided car lets you do it on YOUR terms, not on the terms of random contact. The rear wheels contacting the rail are going to suck the most speed from the car, and a properly aligned rail-guided car keeps the rears off of the rail.

Also, if you have enough positive camber on your DFW (non-raised front wheel), the it will roll down the rail rather than slide against it.
Question. What is the single ONE most thing a guy can do that affects the speed of the car?

Or is someone wants to rank them that would be great.
Hmm, I would say:

1) Reduce friction in wheels and axles via proper polishing and lubrication
2) Properly align the car so that the wheels are all working in the same direction (possibly) using rail-guided techniques.
3) Maximize potential energy by moving the car's center-of-mass further up the hill. Obviously make sure the car weighs the full 5oz
Now thats what I'm talking about Vikimin K. Ok oil it is. Ill return this graphite I bought. Tell be the greatest oil on the planet. I know there are 2 maybe 3 kinds.

As far as this silicone spray. I just spray that on the axels and somehow inside the tire hole?

Still don't understand how to make the car ride the rail by angling a tire but I have time and alot of youtube videos to watch.

I decided against the pre weighed, extended tire base, pre cut funny car from online. Today I bought the standard width non pre weighted funny car and some tungsten cylinder weights. I have the car!!! At the building clinic Ill drill them in and puddy over. My plan to get to 4.999999999999 grams is tungsten puddy and stick the tiniest pieces to the car to get to the max weight. I alao hope I can drill holes for the front tires up at the very front of the car

Question. The tungsten disk sould go under the car a inch in front of rear axel all in the exact same place as the opposite side so weight is balanced and even then puddied over and sanded? Good plan?

Were gonna win!



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Vitamin K
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Re: Hello brand new here.

Post by Vitamin K » Fri Jan 11, 2019 3:42 pm

Now thats what I'm talking about Vikimin K. Ok oil it is. Ill return this graphite I bought. Tell be the greatest oil on the planet. I know there are 2 maybe 3 kinds.
Most of the oils available are based on Krytox GPL 100. Some are just pure Krytox, others have additives to (allegedly) make them faster.

I personally have only ever used the plain Krytox that Max-V sells: https://www.maximum-velocity.com/product/krytox-100/

The "new hotness" for the league racers is this oil blend that Derby Evolution sells: https://www.derbyevolution.com/BB-Extre ... BB-Ext.htm
As far as this silicone spray. I just spray that on the axels and somehow inside the tire hole?
What I do is:
- Polish the axles (plenty of info out there on this)
- Polish the wheel bores (also plenty of info available: I use novus #2 and a tamiya swab)
- Put the axles in something to hold them with the heads up (like, a chunk of wood with a few holes in it), spray the axles well with the Max-Pro, making sure to get under the heads of the axles. Put the axles into a dust-free container to sit for about 15 minutes (or more).
- Get a tamiya swab or a foam applicator that will fit into the bore. Put it into a little plastic container and spray it heavily with the Max Pro. Wait 15 minutes for any propellant to evaporate and then use the coated swab to coat the inside of the wheel bores. Put them someplace dust-free for at least 30 minutes to let the silicone dry.
- When you're ready to put the axles in the wheels, put a tiny drop of oil on each axle. Turn the axle to coat, make sure that it gets under the head of the axle too. Use a tiny strip of paper to wick off any excess oil and then put the axle in the wheel and give it a spin. Mount it in the car.
Still don't understand how to make the car ride the rail by angling a tire but I have time and alot of youtube videos to watch.
This can be a little tricky to grasp. I tried to write up a document a while back outlining the theory behind rail riding: https://docs.google.com/document/d/1af1 ... sp=sharing
I decided against the pre weighed, extended tire base, pre cut funny car from online. Today I bought the standard width non pre weighted funny car and some tungsten cylinder weights. I have the car!!! At the building clinic Ill drill them in and puddy over. My plan to get to 4.999999999999 grams is tungsten puddy and stick the tiniest pieces to the car to get to the max weight. I alao hope I can drill holes for the front tires up at the very front of the car
Tungsten putty is the easiest way to assure you're as close to weight as possible. Get the car within .1 of an ounce to max weight and fill the rest in with putty. Then you can just add or remove it as needed at weigh-in.
Question. The tungsten disk sould go under the car a inch in front of rear axel all in the exact same place as the opposite side so weight is balanced and even then puddied over and sanded? Good plan?
I would just put the weight evenly spaced between both rear wheels. Some people bias the weight a little towards the DFW side, but that's probably not worth bothering with.

Best of luck!



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Re: Hello brand new here.

Post by Darin McGrew » Fri Jan 11, 2019 6:57 pm

Sleestak wrote:
Fri Jan 11, 2019 2:09 pm
Still don't understand how to make the car ride the rail by angling a tire but I have time and alot of youtube videos to watch.
Here's one that I like, because it does a good job of explaining the science behind everything:
EASY Pinewood Derby Car WINS using Science!!!

The rail riding explanation starts at about 10:50.

Vitamin K wrote:
Fri Jan 11, 2019 3:42 pm
Tungsten putty is the easiest way to assure you're as close to weight as possible. Get the car within .1 of an ounce to max weight and fill the rest in with putty. Then you can just add or remove it as needed at weigh-in.
This is an important point. Don't try to show up at the derby with a car that weighs 5.00000 ounces. Don't try to show up with a car that weighs 4.99999 ounces either. Plan to adjust the car's weight at the weigh-in.

I've heard of derbies that don't allow you to add weight at the weigh-in; you're only allowed to remove excess weight. In that case, I'd build a car that weighs 4.9 ounces, and then add at least 0.2 ounces of easily removed weight. Tungsten putty works, obviously. But so do tiny screws (about the size of a single BB).

At our derbies, we generally use pennies and BBs to add the last little bit of weight.

Edit to add: I've seen too many overweight cars damaged because there was no easy way to remove weight, so they went under the drill to drill out excess weight.



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Re: Hello brand new here.

Post by Sleestak » Fri Jan 11, 2019 9:51 pm

Thank you both that was alot of typing and it is appreciated. I read every word atleast 2 times.



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Re: Hello brand new here.

Post by Sleestak » Fri Jan 11, 2019 10:31 pm

I would just put the weight evenly spaced between both rear wheels. Some people bias the weight a little towards the DFW side, but that's probably not worth bothering with

Sorry to question every little thing. Right between the wheels is the axel slot so cant be drilling holes here. You dont mean drill into the top or the car?



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Re: Hello brand new here.

Post by Speedster » Sat Jan 12, 2019 6:29 am

Since speed is your only object, and if the shape of the car is designed only for speed, if you use the proper shaped weight, such as tungsten 3/8" x 1/2" cylinders, you will be drilling into the side of the car. Use a 25/64" drill bit because a 3/8" cylinder will not go into a 3/8" hole. Do not drill all the way through and you will then need to seal only one hole. That will give you 1 and 1/2 ounce behind the rear axle slot. To easily get 2 ounces behind the rear axle slot you can buy a 1/2 ounce plate that is fairly thin and put it on the top of the car all the way to the back. If you remove a little wood at the top of the car you will not change the shape of the car. You should be able to get a balance point of 3/4" in front of the rear axle slot with this set up. This is safe for all tracks. If you can't get this balance point, drill or carve wood out of the bottom of the car. At some point you should be able to get a 3/4" COM. If the car is so thin you need more weight use a 3/8" lead rod or a 3/8" rod they call Tundra and Tundra is not Toxic. Tundra rod has the same density of lead and can be cut or drilled very easily. Since you are not allowed to drill out lead at your race, Tundra would be the weight of choice.

There is a tool sold at Hobby Lobby that will allow you to raise a hole for a 3 wheeler in less then 2 seconds. Nothin else is necessary.

If you will send me your mailing address as I asked you, I will send you Jay Wiles writing on Rail Riding and also Troy Thorne's book, Build a Winning Pinewood Derby Car. As before, No Charge. Troy Thornes book has an excellent explanation and also pictures showing how to set up a car for rail riding. You and your daughter will both enjoy meeting Dash Derby, his little sister Dottie, and his friends, Max Design and Professor Speed. They will be your tour guides through the process of building a derby car.

I'm on your side, Racer Sleestak. Let me help you. You already know these other guys are smart so you can easily check on me to learn if I'm telling the truth. When building a car for speed, we're all going to tell you the same thing because we are required to follow the Laws of Physics. Once you know the Basics it is then time to FINE TUNE everything.
Please Send me your mailing address.
Best
Bill



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Re: Hello brand new here.

Post by Sleestak » Sat Jan 12, 2019 9:17 am

I found a great youtube video last night. Is this guy any of you. Broke down everything very easy. Link:


https://youtu.be/OlglNeY222c

As far as adding weight. This is a 5 year old girl's car so as well as winning it needs to be cute. I dont want to drill into the top or side and destroy the shape of th funny car. The weights are going to have to go on the bottom on the car in front of and behind the rear axil.

Question....also this guy in the video drilled many holes in the bottom of his car to make lighter. Who recomends this? It will make it lighter but will also be ugly and add more air drag?

Speedster..of course I wont drill all the way thru the car. Lol



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Re: Hello brand new here.

Post by Speedster » Sat Jan 12, 2019 10:57 am

Drilling in the side of the car will not affect the looks. There will be about 1/8" of the hole left showing after the holes are filled with 3 - 3/8" x 1/2" tungsten cylinders from Maximum Velocity. 1/2" Cylinder lengths vary and some are a bit longer and they are a nuisance. Bondo is best to seal the hole because of its adhesion but wood filler might be successful also. I have sealed hundreds of holes with Bondo (Walmart) and it will get spongy in less then 2 minutes. When it gets spongy take a razor blade, cut off excess, you're done. The holes will be close to the bottom of the car if drilled properly. Much of all 3 holes will be covered by the rear wheel. Paint the car and no one will know how you weighted the car. Normally one hole behind the rear axle slot and two holes in front of the rear axle slot when using round weight. Bondo smells when drying so don't do this in the house. I can do 4 cars at one time so things move fast at Workshops. The front most hole will probably take a very small piece of Tundra. Cut a piece of 3/8" wood dowel to fill the hole to the proper amount and seal it.

Yes, drill out the bottom if it is necessary to add weight. Cutting through the air is not all that important. You want a light car in the front so you can add more weight in the back. The car will only travel about 11 MPH and that is not enough speed to affect the car that much. Where the car will balance is far more important. Cover the bottom with Packing Tape.

The video is EXCELLENT ! I disagree with him on the amount of Camber and importance of wheel bore treatment but that falls in the FINE TUNING category. He did a Great job.
I'm going to watch it again.



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Re: Hello brand new here.

Post by Darin McGrew » Sat Jan 12, 2019 5:20 pm

Sleestak wrote:
Sat Jan 12, 2019 9:17 am
Question....also this guy in the video drilled many holes in the bottom of his car to make lighter. Who recomends this? It will make it lighter but will also be ugly and add more air drag?
I haven't seen anyone hollow out the wooden block by drilling holes like that video shows, but I have seen people hollow out the wooden block. The basic idea is that you want to remove as much wood as possible, so that you can add as much weight as possible. That concentrates the weight in one place, reducing the car's rotational inertia, and makes it easier to control where the car's center of mass is located.

But the way I've usually seen hollowed out blocks is a technique I've heard called "ladder cars". Basically, you start by cutting a thin slab from the bottom of the block, keeping enough wood to support the axle slots. Here's a view from the bottom:

Code: Select all

  -------------------
  |  :          :   |
  |  :          :   |
  -------------------
Then remove all the wood in the middle, leaving two "chopsticks" of wood along the side, and two "ladder rungs" of wood where the axle slots go:

Code: Select all

  ===================
    |:|        |:|
    |:|        |:|
  ===================
You can add weight by glueing it to the wood near the rear axle location. If you want it to look cuter, then you can cover the top with veneer, or tape, or something else extremely light. Some speed-oriented cars run just like that though.



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Re: Hello brand new here.

Post by whodathunkit » Sat Jan 12, 2019 5:25 pm

:welcome:
Wood is weight but its not the right type of weight needed to make a fast car!
Ballast weight is the much better weight choice because as Darin points out
it's the motor to start pushing the car down the slope and to give it the push that is needed to carry it through the flat portion of the track.
So the more wood weight you can remove from the car body the more room you'll have for that bigger ballast weight motor.

If you want a fast car it must be bare bones and very light weight on the wood side of things.
So that's why in the video your seeing the all the holes drilled and or the large openings to remove the unwanted wood weight in the car body.
Sure it's not the best for looks.. but it will beat you if your not packing all the ballast weight needed to drive your car home to the finish line.

What Darin and Speedster both are trying to point out here about the coverings for the openings with tapes and or veneers.. this will help with Drag.
To touch a little more on what Darin is trying to share with you about the light weight ladder type car body's and the covering's for these car types .
Check out some of the ladder type car body's made by Lightnin Boy found on this topic:
http://www.derbytalk.com/viewtopic.php?t=7767


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

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Re: Hello brand new here.

Post by Speedster » Sun Jan 13, 2019 7:27 am

Howdy, Team Sleestak.
Would you please send me a picture of the car, either to Derbytalk or my email. You will notice in the video most of the wood that could be removed, has been removed, and he could only get a 1" COM. Science will allow me to do something a little different and yet the car will look exactly the same. Here's what I'm planning and I'm going to build a car. I will start with a simple wedge like the one in the video . From experience I won't need to drill holes in the bottom of the car. A 1/2" tungsten plate will be fitted on top the car at the very back that will give the car 2 ounces behind the rear axle slot. Now for design. I will cut the design out of Balsa wood and fit it to the top of the car. All cracks will be sealed with Glazing putty and under Primer Surfacer the car will look like one piece. No holes in the bottom of the car and it will have a 3/4" COM.

More talk about wheels, axles, oil, later.



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