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.
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Vitamin K
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Re: Hello brand new here.

Post by Vitamin K » Thu Mar 07, 2019 7:28 am

Sleestak wrote:
Thu Mar 07, 2019 6:06 am
Darin McGrew wrote:
Wed Mar 06, 2019 11:19 pm
My experience with Krytox is that the spin test doesn't last as long as with graphite, but on the track, under load, the cars are at least as fast as with graphite. Plus, it's a lot less messy to have Krytox at our workshops than graphite (which always left a big black mess). But I'm more experienced in organizing workshops and derbies, and in building unusual designs, than I am in building super-fast cars.
Ok this makes me feel better about my low spin tire times.
I can confirm this. Krytox performs best under load. In fact, for an unweighted car, graphite is probably faster than Krytox. It's the way it performs when under pressure that it shines.

This is why, btw, that you can build a much heavier outlaw car with Krytox than you can with graphite.



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Re: Hello brand new here.

Post by Vitamin K » Thu Mar 07, 2019 7:31 am

Sleestak wrote:
Wed Mar 06, 2019 11:06 pm
I didnt to anything to my axels as far as another lube. I had bought a can of liquid silicone with teflon and I tested it on a big nail. well 20 minute later the nail was still wet. So I didnt want to mix by derby oil with wet silicone so I just used the oil plain on the axles.
You really want something that leaves a dry coating behind. Hence my recommendation of Jig-a-Loo, Max Pro Heavy Duty Silicone or 3M Dry Type silicone. Standard "pure" silicone sprays leave a wet coat behind, and that's not what you want.



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Re: Hello brand new here.

Post by Sleestak » Fri Mar 08, 2019 9:13 pm

She won 1st place!!!!!! 4.003 avarage!!!!



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Re: Hello brand new here.

Post by Sleestak » Sat Mar 09, 2019 7:36 am

She dominated. Some wins by 8 feel. Her car seemed to pick up speed at the flat part while the others coasted slower hers keep the speed and was straight as a arrow. I have pics and videos on Facebook in anyone want to see. Private message me and we can be 2 day facebook friends.



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Re: Hello brand new here.

Post by Vitamin K » Sat Mar 09, 2019 5:20 pm

Congrats!



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Re: Hello brand new here.

Post by thekob » Mon Mar 11, 2019 7:42 am

I've read through the thread and have a couple of q's. I think I'm in a similar spot as sleestak, as we're both suffering from dismal childhood derby failures. Young KOB had his mind made up he was going to make his as thin as possible. He cut his like a plank, and added a big ole lead plate weight to the bottom. Problem was he hadn't hollowed out enough, so the weight dragged. The darn thing didn't even finish the race. My father was the cubmaster for the pack and he didn't want to help us at all because he didn't want to be the cliché scoutmaster who's kid always wins and but it's obvious it was the parent's car rather than the kids. That instilled in my two brothers and I a level of competitiveness that borders on unhealth along with a long memory, apparently.

At any rate, I'm trying to figure out what kind of lubricant to use. I think I'll do krytox if I can find a bottle around town, and I've read about prepping the axle bores and axles with silicone spray. From prior comments it looks like I don't have to be concerned with loose graphite on the track fouling up the wheels and axles detrimentally. I'm wondering what do about the side of the car where the wheel/hub might rub. I've read the comments on polishing and using nail polish to harden it. In the book we got at the scout shop that uses graphite they recommend burnishing it into the wood around the axle and really grinding it in. I was wondering, since I'm using silicone spray/krytox, if I could just put a piece of packing tape on the wood around the axle hole before inserting the axle and apply silicone spray to it for a slick surface for the wheel/hub to rub against. Any insight from the pros on this option?



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Re: Hello brand new here.

Post by Speedster » Mon Mar 11, 2019 9:34 am

thekob, Welcome to Derbytalk.

I'm sorry that is how your Father felt. I would have preferred he taught you all The Physics of the Pinewood Derby and then helped you build your car.
Please read your rules very carefully.
What's the name of the book you got at the Scout Shop? "Build a Winning Pinewood Derby Car?"
Vitamin K has talked about Oil Lube in detail. I'd listen to him if using oil.
Remember, the nail DOES NOT turn. That's all I'll say about the nail so Folks don't start hollering at me.
A nice round wheel with lots of prep will help make your car go fast.
If you are obsessed with speed, Get Rid of the Wood. A car shaped like a Hershey bar is a good way to start. Tungsten weight, put in the right place, will help your speed. Rail riding will help your speed.
Teach your scout all the science that will make a Block of Wood go down a Hill Fast. Make the building of the car a memory your Scout will Cherish forever.



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Re: Hello brand new here.

Post by Vitamin K » Mon Mar 11, 2019 11:11 am

thekob wrote:
Mon Mar 11, 2019 7:42 am
I've read through the thread and have a couple of q's. I think I'm in a similar spot as sleestak, as we're both suffering from dismal childhood derby failures. Young KOB had his mind made up he was going to make his as thin as possible. He cut his like a plank, and added a big ole lead plate weight to the bottom. Problem was he hadn't hollowed out enough, so the weight dragged. The darn thing didn't even finish the race. My father was the cubmaster for the pack and he didn't want to help us at all because he didn't want to be the cliché scoutmaster who's kid always wins and but it's obvious it was the parent's car rather than the kids. That instilled in my two brothers and I a level of competitiveness that borders on unhealth along with a long memory, apparently.

At any rate, I'm trying to figure out what kind of lubricant to use. I think I'll do krytox if I can find a bottle around town, and I've read about prepping the axle bores and axles with silicone spray. From prior comments it looks like I don't have to be concerned with loose graphite on the track fouling up the wheels and axles detrimentally. I'm wondering what do about the side of the car where the wheel/hub might rub. I've read the comments on polishing and using nail polish to harden it. In the book we got at the scout shop that uses graphite they recommend burnishing it into the wood around the axle and really grinding it in. I was wondering, since I'm using silicone spray/krytox, if I could just put a piece of packing tape on the wood around the axle hole before inserting the axle and apply silicone spray to it for a slick surface for the wheel/hub to rub against. Any insight from the pros on this option?
The only "local" source of Krytox that I can think of would be a Scout Store, where they sell it (overprice, IMO). Otherwise I'd just order from Maximum Velocity, or Ebay or some other vendor.

For "slickening" up the body where the hub is going to contact, I would recommend a few coats of CA glue polished to a nice finish. Obviously you don't want to get the CA glue anywhere near your polished wheels or axles until it cures, lest the fumes damage your interface.



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Re: Hello brand new here.

Post by thekob » Tue Mar 12, 2019 3:41 pm

Speedster wrote:
Mon Mar 11, 2019 9:34 am
thekob, Welcome to Derbytalk.

I'm sorry that is how your Father felt. I would have preferred he taught you all The Physics of the Pinewood Derby and then helped you build your car.
Please read your rules very carefully.
What's the name of the book you got at the Scout Shop? "Build a Winning Pinewood Derby Car?"
Vitamin K has talked about Oil Lube in detail. I'd listen to him if using oil.
Remember, the nail DOES NOT turn. That's all I'll say about the nail so Folks don't start hollering at me.
A nice round wheel with lots of prep will help make your car go fast.
If you are obsessed with speed, Get Rid of the Wood. A car shaped like a Hershey bar is a good way to start. Tungsten weight, put in the right place, will help your speed. Rail riding will help your speed.
Teach your scout all the science that will make a Block of Wood go down a Hill Fast. Make the building of the car a memory your Scout will Cherish forever.
Strange thing about our rules...it says dry lube only but then the guy at the scout shop said krytox is a dry lube because it's such a thing as film. Same guy also talked me out of getting the $42 wheel mandrel (overpriced I know, but that and the krytox are the only things I can't get at Hobby Lobby w a 40% off coupon) because the "wheels are much better nowadays". I'll probably buy one or build one for next year though.

At any rate, our rules in general are kinda poorly written. Regarding axles for example, the ones that come with the kit must be used. "They may be polished or lubricated". Does that mean they can't be canted, that they can't be polished AND lubricated? Also it says the wheels that came with the kit must be used. Does that mean we can't use the pink ones my kid picked out from the scout shop? I got about a million questions, lol. Hopefully I'll be able to ask em all tonight...

We're planning on rail riding, three wheels down, etc. I've already filed the axles to take the burrs off and polished them, then straightened them in that jig that you hammer, and canted the nail head. I tried polishing the wheel axles with plastic polish and Tamiya swabs but the mediums were only big enough to do the outside and inside hub. I got the small swabs today, so hopefully those'll fit. Any idea how long to polish them for? I was getting nervous going beyond a five count for the outside and inside hub. I'll see tonight if I can grind the inside hub to a cone or if I have to leave it flat.



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Re: Hello brand new here.

Post by thekob » Tue Mar 12, 2019 3:53 pm

Vitamin K wrote:
Mon Mar 11, 2019 11:11 am
The only "local" source of Krytox that I can think of would be a Scout Store, where they sell it (overprice, IMO). Otherwise I'd just order from Maximum Velocity, or Ebay or some other vendor.

For "slickening" up the body where the hub is going to contact, I would recommend a few coats of CA glue polished to a nice finish. Obviously you don't want to get the CA glue anywhere near your polished wheels or axles until it cures, lest the fumes damage your interface.
Yup I got it at the scout store...$21.99 for that tiny bottle. They were also selling a wheel mandrel (drill bit that spins the wheel) for $7.99. I got one at Hobby Lobby for $3.99 minus the 40% off coupon. The scout shop guy talked me out of getting that tool that shaves down the high spots on the wheel as well....it was $42 and I'm not sure it was legal to do anyhow. I figure I'll get one for next year at some point instead. I had to get the krytox since I have to turn in the car on Friday at the latest....oh well, it should last me a couple years if I keep the cap on.

What process should I follow for hardening around the wheels? I'd assume I shouldn't paint it at all, but any suggestions for procedure re:sanding? I figure I don't want to take too much off. Also any idea on how long to wait between "coats" of CA? Also, how do you polish it, with an emery board or 2000/2500 grit sandpaper? Would you apply krytox to it afterwards? Also, it seems that for those that go with graphite they use it everyfreakingwhere....on the axle, burnish it into the sides of the tires, into the car body, maybe a bit behind the ears and some tossed over the right shoulder for luck too! Is there any advantage of putting krytox on the CA (or I might use nail polish to save myself another trip to the store) after it cures and is hard?



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Re: Hello brand new here.

Post by thekob » Tue Mar 12, 2019 4:25 pm

Oh, btw the book I referenced was "Building the fastest pinewood derby car" by Troy Thorne.



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Re: Hello brand new here.

Post by Speedster » Tue Mar 12, 2019 4:42 pm

Congratulations. That's a Great book.

The Pro Wheel shaver costs $42.95 but it requires another tool called the Pro Hub tool that cost an additional $10.95. My personal choice is to buy 3 sets of the Preferred numbered wheels
(2, 8, 15) and that will automatically give you 4 sets if you are allowed to run on 3 wheels. They usually are .003 or less out of round. It's hard to make a wheel perfectly round, even for the vendors. However, when you get down below .003 you've got a fairly good wheel. I ordered wheels from 4 different vendors a few years ago and none of them were perfectly round. I received a set of wheels from Derby Worx from when I raced in the Mid America in 2013. All 4 of the wheels were perfectly round on Knotts Concentricity gauge. That was amazing. I still have them.



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Re: Hello brand new here.

Post by thekob » Tue Mar 12, 2019 7:33 pm

Speedster wrote:
Tue Mar 12, 2019 4:42 pm
Congratulations. That's a Great book.

The Pro Wheel shaver costs $42.95 but it requires another tool called the Pro Hub tool that cost an additional $10.95. My personal choice is to buy 3 sets of the Preferred numbered wheels
(2, 8, 15) and that will automatically give you 4 sets if you are allowed to run on 3 wheels. They usually are .003 or less out of round. It's hard to make a wheel perfectly round, even for the vendors. However, when you get down below .003 you've got a fairly good wheel. I ordered wheels from 4 different vendors a few years ago and none of them were perfectly round. I received a set of wheels from Derby Worx from when I raced in the Mid America in 2013. All 4 of the wheels were perfectly round on Knotts Concentricity gauge. That was amazing. I still have them.
Cool deal! Our rules state "the wheels supplied with the kit must be used." We had already purchased a set of pink ones that my daughter picked out from the scout shop. Same logos and markings as the one in the kit, just pink instead of black. I asked if we could use them, and got an overwhelming "Nope!". Kinda nuts, and it sucked having to break the news to the kid. What kind of rainbow derby car has black wheels instead of pink anyways? SMH.

At any rate, that's one that I'll be looking to change for next year. This year she'll race with the black ones and switch em out for the pink ones to display in her room.

After the derby im planning to build or buy a concentricity gauge along with a wheel shaving tool. I just sanded them this year with a wheel mandrel in a drill and then polished with meguiars headlight polish. I already have the "wheel trueing" hub tool for the inner hubs...I didn't even think about getting the one for the outer hubs.



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Re: Hello brand new here.

Post by Speedster » Tue Mar 12, 2019 8:13 pm

I learn something new everyday. I've never heard of anyone not allowing a regulation BSA wheel made in the USA to not be allowed. I wonder what the reason could possibly be?



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Re: Hello brand new here.

Post by thekob » Wed Mar 13, 2019 6:37 am

Speedster wrote:
Tue Mar 12, 2019 8:13 pm
I learn something new everyday. I've never heard of anyone not allowing a regulation BSA wheel made in the USA to not be allowed. I wonder what the reason could possibly be?
My best guess is just there may not have been a lot of thought put into the rules, or perhaps they just hadn't considered the possibility. The rule for the axles, wheels and car body all state something similar ("must use what comes with the kit) and I guess for the other two it makes sense.

Of course during check in yesterday despite the fairly strict rules the only thing they checked was the weight. Since it's an early check-in I'd want to check at least the ground clearance and width between the tires too...you'd think that'd be simple to do with a block of wood to set the car on. Ah well, something I can suggest for next year I suppose.



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