Dismiss Notice
Welcome to
Pinewood Derby Online, a forum for questions and discussions about everyone's favorite gravity powered racers!
CLICK HERE to register as a member today for full access to the forum, it's fast, simple, and absolutely free!

Looking for advice/guidance

Discussion in 'Ask The Pros' started by Brian Stanley, Mar 8, 2019.

  1. Brian Stanley

    Brian Stanley Pinewood Ninja

    Messages:
    47
    Likes Received:
    24
    Trophy Points:
    8
    Gender:
    Male
    Location:
    Charlotte, NC
    Hi folks, wish I had stumbled upon you a couple of months ago!

    I could use some guidance/advice.

    My son and I built our first car and raced it this past weekend. We won his den and I believe we were on our way to winning the whole pack when disaster hit and the car jumped the track twice, sustaining damage to one of the wheel hubs, the crew chief (me) didn’t pack any spares (lesson learned). The track was about as smooth as a country dirt road. I was able to repair it, but the car was not near as fast afterwards. We wound up finishing 6th in the pack.

    We’re going on to the district and I want to make some adjustments to the car based on what I’ve read here the last few days, and want to make sure I’m heading down the right road.

    Here are the particulars on the car:

    • 3 wheel, rail rider. Front right is the dominant wheel
    • COG/balance point is at .75” in front of the rear axle.
    • Extended wheelbase, 5 5/8
    • Axle holes drilled straight with Derby Worx Pro Body Tool
    • The rail riding offset (curve) is about 1.5” per 4’
    • Stock Wheels and Axles
    • Rear axles are 1.5 degrees and wheels towed out slightly
    • Wheels bores and hubs polished with Derby Dust bore polishing kit (includes burnishing the bore with graphite)
    • Wheel treads polished with 1000 to 5000 paper and then burnished with graphite (this may have been a mistake)
    • Wheel gap established with the Derby Dust gap tool
    • Axles polished with 800 - 5000 paper and finished with Derby Dust axle polish
    • Below are photos of the weight, which is (not sure I’m using the correct terms here): DFW: 20.27g DRW: 53g NDRW: 71.91g

    The car was quite fast (comparatively speaking), we won all of our heats by a healthy margin until the crash. The race was elimination, no timer so I don't know how fast it was. However, the car was fishtailing (or snaking?) all the way down the track. I don’t think this is going to cut it at the district.

    My original hypothesis was that the car was tail heavy, and this along with the graphite burnished wheel treads is what was making it swerve. Now, after reading here in the forums for the last few days I’m not so sure.

    Here are my questions:
    1. Should I move the weights to the dominant side of the car, to better balance side to side?
    2. Does the fore /aft balance look good? Or should I attempt to change it?
    3. The graphite burnished treads on the wheels sure look good, but could that slickness be contributing to the fishtail? Should I clean the graphite off the treads?
    4. Should I get rid of the tow out in the rear wheels?
    5. Should I have the car turn into the rail more aggressively (maybe 5" to 6" per 4')?
    6. Should I shorten the gap between the wheels and the body (I used a gap tool, but it looks like a lot)?
    7. Should I pull the axles and Pledge them? They are being held in with CA but I can debond it.
    C1.jpg

    c2.jpg

    I do have access to a track (not the final race track) for testing, though it is not convenient to get to so I won’t be able to do a ton of testing and tuning.

    Any advice is greatly appreciated.

    By the way my son and I's main hobby is building and flying model airplanes, so this has been pretty fun as well!

    Thanks,

    Brian
     
  2. derby freak

    derby freak National Contender Pro Racer

    Messages:
    504
    Likes Received:
    20
    Trophy Points:
    18
    questions.....
    1:) you want to have the same or the most weight on the dominate side of your car that way your car doesn't try to rock toward your non dominate side. Maybe try to smooth the tungsten putty out a lil to make it more flat to make sure it doesn't drag on the center rail anywhere or put it in the gap that is open at the rear of the car.
    2:) as long as you have a 3/4 to 1/2 cog on a smooth track you should be good
    3:)clean all the graphite off the tread of the wheels and use some 1500 grit sandpaper to get off the dirt and debris that may be imbedded in the tread surfaces...the non dominate run surface on the rear looks pretty rough in the pic..but yea I don't put anything on the tread surface of my wheels
    4:)you want about a 3 degree cant on your rears but no tow
    5:)you want about 2-3" of drift in 4ft or 4-6" of drift over 8ft
    6:)about the thickness of a credit card should be fine on the wheel gap
    7:)no just add more graphite

    hope this helps
     
  3. Chief

    Chief PWD Royalty

    Messages:
    1,522
    Likes Received:
    94
    Trophy Points:
    48
    +1
    By my calcuations the car is 145.18 grams? If so, thats too heavy...143 grams = 5oz. Not sure but from the photos it looks like you do not have enough steer on the front if there is any. By the looks of it, I would put the steer at 4 inches but if you have a way to test it, I would do that for sure!!
     
  4. DuckOfAllTrades

    DuckOfAllTrades League Racer

    Messages:
    311
    Likes Received:
    88
    Trophy Points:
    28
    Gender:
    Male
    Location:
    Greensboro
    Sounds like you and I have the same luck! My son’s cars have broke after being among the best the past two years! Never jumped the track, but they were dropped. You’ll kill it at districts. You are in the right place.
     
  5. B_Regal Racing

    B_Regal Racing PWD Royalty Pro Racer

    Messages:
    1,493
    Likes Received:
    246
    Trophy Points:
    63
    From the pictures, it looks like the car is steering away from the rail. I typically have my cars steer into the rail...
     
    DerbyDoctor and Dldoug like this.
  6. Thinkin'Bout Racin

    Thinkin'Bout Racin League Racer

    Messages:
    456
    Likes Received:
    209
    Trophy Points:
    43
    Gender:
    Male
    I am not a pro, but I will add what I know. Your thoughts on 3-7 are SPOT on! Go with it!!! If you can remove the axles and pledge then great otherwise don't break the car to just add pledge.

    Your questions one and two ... you have plenty of weight on the DFW. You also have room to move weight around in back. A good Scout car can have 16 grams or less on the DFW. If this was our car, I would try to get that DFW weight down to 18 grams. 18 grams will still give you plenty of weight for steer.

    Rear/all gaps need to be tighter. Depending on axles used will dictate how much gap.

    Your wiggles are not being caused by too much weight in the rear. Possibly the alignment, wheel gap, or graphite on the treads, or a combination of these. When the car wiggled, was it only the rear? Or did the front leave the rail also?

    It was mentioned above, but it is important to have clean wheels.
     
  7. Pinewood Outlaw

    Pinewood Outlaw Workshop Leader

    Messages:
    163
    Likes Received:
    80
    Trophy Points:
    28
    Gender:
    Male
    Ditch the Derby Worx tools
     
    Dizzy and TRE like this.
  8. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,396
    Likes Received:
    288
    Trophy Points:
    83
    +1
     
    Dizzy likes this.
  9. Chief

    Chief PWD Royalty

    Messages:
    1,522
    Likes Received:
    94
    Trophy Points:
    48
    +2 and a lot more
     
    Dizzy likes this.
  10. Brian Stanley

    Brian Stanley Pinewood Ninja

    Messages:
    47
    Likes Received:
    24
    Trophy Points:
    8
    Gender:
    Male
    Location:
    Charlotte, NC
    Ok folks, we've taken your advice and reworked things a bit here!

    - Moved the weight around to balance the rear wheels
    - Shifted the weight back a bit taking some of the weight off the front wheel
    - Changed the drift to about 4" per 4 feet
    - Took the tow out of the rear wheels (as best as we could)
    - Tightened the wheel/body gap
    - Cleaned the graphite off the wheel treads
    - Pledged the axles

    After reading through here the last several days the one thing I'm concerned about is our rear axles. The holes are straight, and the axles are bent at 1.5 degrees. We tried to take the tow out as best we could. Redrilling them at the 3 degrees is not really an option at this point, not to mention I don't think there is anyway I could get them straight.

    Going to take 3-4 months break after districts but then we're going to get going building prototypes for next year!

    I really appreciate the help you guys have given us. I'm excited, already planning next year's car. I'm drooling over a SB or a Clear Jig.

    Good Racing!!

    One.jpg
    Two.jpg
     
  11. Chief

    Chief PWD Royalty

    Messages:
    1,522
    Likes Received:
    94
    Trophy Points:
    48
    How much does the car weigh?
     
  12. Brian Stanley

    Brian Stanley Pinewood Ninja

    Messages:
    47
    Likes Received:
    24
    Trophy Points:
    8
    Gender:
    Male
    Location:
    Charlotte, NC
    It's about 5.1, so a shade over. Want to come in a little heavy so I can trim putty at weigh-in. Want to get to 5.04!
     
  13. Chief

    Chief PWD Royalty

    Messages:
    1,522
    Likes Received:
    94
    Trophy Points:
    48
    Gotcha!!
     
  14. DuckOfAllTrades

    DuckOfAllTrades League Racer

    Messages:
    311
    Likes Received:
    88
    Trophy Points:
    28
    Gender:
    Male
    Location:
    Greensboro
    Seems like it would be easier to add putty than shave it?
     
  15. Mojo Racing

    Mojo Racing National Contender Pro Racer

    Messages:
    768
    Likes Received:
    270
    Trophy Points:
    63
    Location:
    Uniontown, OH
    I would rather shave it than add it.

    Depending on their scale, if your car is light, they would frown on you adding weight right there. To make the car legal, they would happily see you take weight out. It is all perception right there
     
    Charles Studer and Dizzy like this.
  16. e/o

    e/o Pinewood Ninja

    Messages:
    51
    Likes Received:
    20
    Trophy Points:
    8
    Gender:
    Male
    Location:
    Atlanta, GA
    Yep.

    At our pack, if your car weighs in at exactly 5 and you’re like “hey could I have it back to get to 5.04 to take advantage of the scale’s rounding error” I feel confident they would politely tell you to eff off.
     
  17. "The Fonze"

    "The Fonze" District Champion Pro Racer

    Messages:
    144
    Likes Received:
    99
    Trophy Points:
    28
    Gender:
    Male
    Who cars what they think. If you can add weight then add it.
     
  18. derby freak

    derby freak National Contender Pro Racer

    Messages:
    504
    Likes Received:
    20
    Trophy Points:
    18
    looks good Brian ….I hope it all works out for ya and your son gets a first place win.
     
  19. Charles Studer

    Charles Studer Workshop Leader Pro Racer

    Messages:
    163
    Likes Received:
    44
    Trophy Points:
    28
    Gender:
    Male
    Location:
    Colorado Springs
    Dont bend your rears.
     
  20. Brian Stanley

    Brian Stanley Pinewood Ninja

    Messages:
    47
    Likes Received:
    24
    Trophy Points:
    8
    Gender:
    Male
    Location:
    Charlotte, NC
    Thank you all for your help! We had the district race today, we won Tigers by a good margin, came in 5th out of 150 cars for the overall Championship.

    The car that won was practically a league car, thin, fenders, air guides on wheels etc. They don't know what's coming for them next year ;-).

    Going to take a couple of months break while I build the misses a new dining room table, then I think my son and I are diving in to another car, we're thinking BASX in the Fall. I imagine we'll get creamed, but will enjoy every minute of it!

    IMG_5856.png
     

Share This Page