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Tungsten Discs?

Discussion in 'Ask The Pros' started by Pete Buckler, Dec 3, 2019.

  1. Pete Buckler

    Pete Buckler Pack Champion

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    Last year I picked up a couple of flat top tungsten discs with a slot cut for the axles. I used them last year with pretty good success. They weigh 3.15 oz each and are 1” in diameter and a half inch tall. I’m curious how they would compare to the cubes and/or tungsten bars regarding speed, etc. Does anyone have experience with these? Would I be better off with something different?
     

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  2. Charles Studer

    Charles Studer League Racer Pro Racer

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    I will be running a tungsten dome in my unlimited for finals at Npw this week. I will probably get Alot of sideway looks....but in my opinion if you can place your weight proper and ballast it well with the difference science says it should be competitive. I have also ran the skull in BASX mini but my drill was poor so it never hit potential. For speed proven 1/4" body with 12 cubes behind the axle is the gold standard.
     
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  3. Charles Studer

    Charles Studer League Racer Pro Racer

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    COmmon guys please dont laugh....
     

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  4. Brian Stanley

    Brian Stanley Workshop Leader Pro Racer

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    You should paint it to look like R2D2!
     
  5. DerbyDoctor

    DerbyDoctor Pack Champion

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    We used the the slotted dome style weight for the first two years of scout races. Both similar body styles (fastest car on youtube or ‘spoon body’ as my son calls it) and both did extremely well in scout races. From applying what I learned here, we gained a car length in speed from the first to second year. This past year we switched to 1/4” car with cubes and applied the same techniques, wheelbase, wheels, axles, etc. as the year before and gained another entire car length over the previous year with some tuning. So a car can be competitive in many scout packs using that disc but a cube car definitely has the advantage.
     
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  6. Brian Stanley

    Brian Stanley Workshop Leader Pro Racer

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    I think the real advantage with the cubes over the disc is flexibility. The cubes give much more options for moving the weight around and trying things, whereas with the disc you're limited to where you put your hole. You can find speed moving the weights side to side, it is much easier to do this with the cubes.
     
  7. Pete Buckler

    Pete Buckler Pack Champion

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    I figured as much with regard to speed gains with weight distribution and being able to build a 1/4” car. I’ve got to buy weights for a new car so I’ll go with cubes and maybe a bar. Then I will be able to test the cubes vs the discs.
     
  8. DerbyDad4Hire

    DerbyDad4Hire Administrator Staff Member 25+ Pro Race Wins! National Champion

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    The cubes hands down if you want top speed.
     
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  9. Prozach2

    Prozach2 District Champion

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    I did the disks last year and cubes this year. The cubes allow you to put more weight further back, and give you more flexibility. The disks are so much easier though. For someone with my lack of wood working skills, creating weight pockets was no joke!
     
  10. Pete Buckler

    Pete Buckler Pack Champion

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    My kids and I ended up building two cars with discs and a ladder car with cubes. All were BSA wheels and axles and drilled with the SBE. Then prepped with dd4h axle and wheel products. Now we just need to race them and see...I’ll post the results.
     
  11. Prozach2

    Prozach2 District Champion

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    I did discs last year and a ladder with cubes this year. The one with discs placed first in the district and second in the counsel. I haven't raced the two side by side, but I believe the one with discs from last year was much faster. I believe the reason for this was the one with discs had the COG a little farther up the car which gave it more stability. I don't think that there's any question that a ladder with cubes has more potential, but you have to know what you're doing when you are fine tuning the car. I do not, so on it's test run yesterday, it bounced around pretty bad. The district race is today. Hopefully, it does enough to qualify for the counsel race. If so, I'll put some extra time into tuning it.
     
  12. Prozach2

    Prozach2 District Champion

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    The results are in. In 2019, we built a car using three 1/4" tungsten cylinders behind the rear axle and one 3 oz tungsten disc in front of the axle. It had an average time of 3.231.

    This year, we did two cars that were both ladder bodies with 1/4" tungsten cubes. We had two rows of six cubes behind the rear axle, one row of six cubes in front of the rear axle and one row of 5 cubes in front of that. We used a silver bullet extreme to drill the axle holes. Last year we just drilled them by hand. Based on what I know about Pinewood derby cars, this years cars should've been much faster than last year. They weren't. They averaged 3.237 and 3.275. On the same track, despite all of the "improvements", last year's car was faster.

    It could've been any number of things, but I'm sticking with my theory stated above. The 1/4" cubes allow you to put substantially more weight farther back on the car. They also allow you more flexibility when you're fine tuning your car. If you have a track, tuning table, or some other way to properly tune the car, this can be a big advantage. However, if you don't know how to properly tune the car, you're going to do more harm than good by putting too much weight in the back.
     
  13. Loud2ns

    Loud2ns Rail Runner

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    The fastest car this year was only 6 thousandths slower? Car 2 was a bit off pace. How did they handle going down the track? Wiggles? If you have a scale how much weight on the dfw? I wouldn't bail yet.
     
  14. Prozach2

    Prozach2 District Champion

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    The two cars this year placed 1st and 2nd in his pack. We couldn't have been happier about that.

    The 2nd place car was significantly slower b/c we put zero time into prepping the wheels or axles. That being said, we didn't put any time into the wheels or axles last year. So, a comparison of the slower car vs. last year's car is probably a better example when comparing the weight distribution of the two.

    I think the cars were slower b/c of the wiggles. Next go round, we still plan on doing the ladder body w/ the tungsten cubes. We'll probably check the balance of the wheels with three scales, bend the front axle, and try to tune it to run the rail.
     
  15. Thinkin'Bout Racin

    Thinkin'Bout Racin National Contender

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    I think I grasp what you are doing and will make a couple of observations. Were the cars the same W/B length each year? You stated that this year's cars wiggled ... if that is true, each time the rear wheels touched the guide rails, it cost you about a hundredth. So if it touched 3 times, it cost you about 0.030. Keep that in mind as you read the rest of this.

    If you are using stock wheels, they can vary so much that a direct comparison would be difficult. The amount of both lateral and radial run out can/will affect results.

    How much steer are you using? I always recommend at least 5" over 4' for a beginner Scout car. Quite often it may take 6"-7" to get rid of the wiggles especially if there are other cars around you that are unstable.

    How much wheel gap? This is another area that often creates issues for those starting to learn how to tune.

    What are the weights of your three wheels that touch? That information can answer a lot of questions.

    I agree that your first tungsten cube car can be a challenge. Especially if you don't have a tuning board or a speed square table. HOWEVER don't give up on it as it has great potential!
     
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  16. Prozach2

    Prozach2 District Champion

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    I'm watching a blurry video of one of the heats from the fastest car from this year. I'd estimate that it bounced 4 or 5 times.

    The W/B length was the same on all 3 cars. 5/8 from the back and 1 inch from the front I think. I used the widest wheel base on the SBE.

    Last year's car and the slowest car this year had completely unmodified stock wheels.

    I haven't checked or adjusted the steer on any of these cars. Frankly, I'm not even sure how to do this. I think that I'm supposed to put a bent axle in the FDW with a groove in it, and adjust it until I get the desired amount of steer.

    I saw online that I can order an 8' by 2' piece of glass for $40. I believe that's the same dimension as the tuning template that 5kids racing posted online. I'm looking around for some materials, and hope to build a tuning board with that.

    My fastest car from this year had a wheel gap issue on the FDW. I couldn't push the axle in all the way. I think saw dust built up in the hole as my son was trying to sand off 1/16 of an inch. I couldn't get the axle out, and I was scared we would damage the car by trying. It wasn't very far out, but it was definitely farther out than it should've been. On all of the other cars, the wheel was as close as I could get it without it touching. I didn't measure. just eye balled it.

    At what point in the process do you drill your axle holes? This year, we made the holes for the ladder and the weight pockets. Then we put weights in the pockets, without glueing them, and put it in the jig. After we drilled the axle holes, we cut the block into a thin wedge, and sanded 1/16 off the front on the side of the FDW.

    I don't know the weight on the wheels. I'm going to need to buy some more scales. Let me know if you have a scale recommendation.

    Thanks a lot for your help.
     
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  17. Thinkin'Bout Racin

    Thinkin'Bout Racin National Contender

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    You definitely need to bend the DFW axle and turn it to adjust steer. There is lots of information here, just do a search on how to set your steer. Without adjusting steer and keeping the car running straight, you really did not get nearly as much of the benefit of your cube car as you could. A tuning board of some sort is a requirement! Some have even used a coffee table lifted on one end. A laminated shelf board will also suffice if you don't have something better.

    DD4H sells an inexpensive gap tool. It is made of plastic, so you won't scratch the inner hubs while checking gap. This is really helpful when first learning how to gap wheels. Later on you will get to know the feel of how to gap, but most can benefit from a tool like this when starting out

    Weights on each wheel will tell a lot.

    There are a number of opinions on when to drill your axle holes. Some do it before anything else. Then they check the drill. If it is not good, they start over. Others like to do the weight pockets first and let the wood "relax" before drilling. Their thought is that the wood has now taken any "set" if it is going to. Therefore the drill will stay stable. I personally think both can and do work. I believe that it may also depend on if you are painting, cutting the body all the way thru, covering with wood, or vinyl, or other build considerations. These things all can affect how the wood and therefore how the drill turns out.

    For clarification, I am not a Pro. However I do have a solid understanding of what is happening.
     
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  18. Loud2ns

    Loud2ns Rail Runner

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    You are getting great advice from TBR.
    If you can get some wheels prepped and the wiggles out you'll have a hotrod!
     

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