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Rail runner without narrowing body

Discussion in 'Building tips' started by TexasTaxi, Mar 11, 2020.

  1. TexasTaxi

    TexasTaxi Pinewood Ninja

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    How much bend do you have to put in the DFW axle in order to not have to narrow the body?
     
  2. Thinkin'Bout Racin

    Thinkin'Bout Racin National Contender

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    The two are unrelated. The bend allows changing/adjusting the amount of steer along with lifting the NDFW. Narrowing the front is to help keep the DRW off of the rail.

    Clear as mud?

    Upon edit:
    I went back and re-read the title. What are you trying to accomplish? And what are the rules?
     
    Last edited: Mar 11, 2020
  3. TexasTaxi

    TexasTaxi Pinewood Ninja

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    I'll have to go back through a bunch of posts, but I did read that someone didn't narrow the front of the car because the bend in the axle pushed the edge of the wheel in far enough that the rears would clear.

    I'm trying to keep the edge of the body straight ... for both aesthetics and in preparation for fenders.

    Our rules are pretty open except you have to use the box parts and can not narrow the wheel.
     
  4. 3phase

    3phase Council Champion

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    I don't think you can avoid narrowing the front. Some races just narrow it at the wheels , because of the fenders.
     
  5. TexasTaxi

    TexasTaxi Pinewood Ninja

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    I'm a mechanical designer, by day ... pinewood enthusiast by night! ;)

    Here's a drawing to prove my theory. (everything is to exact scale, except maybe the inner hub)
    Yellow is a BestTrack section.
    Blue is the car body.
    Green are rear wheels at 3 degrees.
    White are front wheels ... left raised and right axle bent 9 degrees.
    The car's body stays centered on the track.
    RR.JPG
     
  6. Thinkin'Bout Racin

    Thinkin'Bout Racin National Contender

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    Interesting ...

    I am not a pro, but here is my 2 cents;

    I think you might be missing a few real world things. Theory is always great, but it still needs to be tested under real world conditions. You have the DFW angled at 9 degrees ...correct? If I am understanding your drawing correctly, you have zero toe-in on the DFW. When you put in steer, you will loose some of that angle, thus changing that distance. Also, the wheel bore to the axle diameter has clearance. Your drawing does not appear to have compensated for that. Again, you will change that distance because of this clearance. Something else to consider, how much of a bend can you actually get thru a bore without causing damage? Again, this will change the distance.

    I like to slow roll a car on the flat section of the track once the steer has been set to about 4". I observe the rears and their relationship to the center rails. This gives me a real world test of how the car will ride while traversing the track. Of course, the distance of the rear wheels will change when the steer is adjusted, but only slightly.
     
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  7. TexasTaxi

    TexasTaxi Pinewood Ninja

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    You could actually get away with a 6 degree bent axle if you put the body upside down and drilled the DFW hole 3 degrees up, instead of straight in. I'm pretty sure a 6 degree bend will go through the wheel.
     
  8. Racing358t

    Racing358t Rail Runner Pro Race Winner Pro Racer

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    Assuming all the wheels are the same the amount of bend of the front axle and hub length play direct rolls in how much the body needs to be narrowed in the front so as to keep the car centered.

    As far as how much needed to raise the non dominant wheel of the track. I would guestimate that to be around 3 or 4 degrees to safely have enough to take up all the slop and still raise it off the track.

    Scott
     
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  9. Brian Stanley

    Brian Stanley Council Champion Pro Racer

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    You have to be careful bending/canting the front wheel too much, especially in Scouts. With an aggressive bend there is very little room between the front wheels for the center rail to ride. You get a person staging the cars who's not paying attention (or doesn't know) and the lifted wheel will be riding down the center rail. On this years car we created a relief for the NDFW rear hub to rest in, and had a good bend in the steer wheel, wasn't much clearance at all for the front rail. Luckily I was the stager for the race, so all was good!
     
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  10. Jupiter 2.9

    Jupiter 2.9 Workshop Leader Pro Racer

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    My guess,
    Take the 1/16 off the DFW side, The block was 1 3/4 " to start with, the hub add 1/16 back. The center rail is only 1 5/8.
    keep the bend around 4 or 5 deg. it's easier to tune with lower bends "to much bend & you can't find that sweet spot",
    It also keeps the nose down.
    If you add fenders you still gain aero by taking the face of the wheel out of play, narrowed or not.
    If you need 4 wheels touching you can still bend NDF axle "if needed".

    Just look at the car on the top of the home page.
    You have the room, just don't go crazy with it.

    Good Luck
     
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  11. B_Regal Racing

    B_Regal Racing PWD Royalty Pro Racer

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    For me, cars that are tight against the rail are fastest (at least in league racing). That is, I might 1/8 to 1/4 of play from the rail to the NDFW with the FDW on the rail. For narrowing the front end, I do as 385 said, which is narrowing the FDW side with respect to the bend. I also narrow the NDFW as well. If the car has fenders, I narrow the NDFW side less than if the car did not have fenders. That is because the NDFW is negatively canted on cars without fenders.
     
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  12. Roadrunner

    Roadrunner Pinewood Ninja

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    Trying to revive an old thread. I am hoping someone here can clarify this a bit for me. It is my understanding that some positive cant is desirable to aid steering - the hub riding on the body will be more effective than if it were on a negative cant riding out to the end of the axle. But why use angles as large as 9 deg? Is this only to raise the ndfw? Why not just drill ndfw higher?
     
  13. Brian Stanley

    Brian Stanley Council Champion Pro Racer

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    The more bend in the axle the more the DFW is rolling on the rail rather than sliding/rubbing. I find the severely bent axles a bear to tune as the slightest of turns can throw the steer way off. Of course I'm really slow, so maybe I'm not the best person to listen to!
     
  14. Roadrunner

    Roadrunner Pinewood Ninja

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    Thanks. That makes sense. Is it only due to tuning issues that guys use less severe cant angles?
     
  15. B_Regal Racing

    B_Regal Racing PWD Royalty Pro Racer

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    Not exactly. The bend is also used for tuning. It controls the height of the nose of the car...
     
  16. Roadrunner

    Roadrunner Pinewood Ninja

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    ... Which has a direct impact on the rear axles re: toe in, out or neutral. I get that it’s all connected. If you’re using a severe dfw angle, would you drill dfw higher in order to maintain a level car? And are those decorative tread bumps required in BASX, or can they be removed. I imagine that they could touch the track if angle is large enough. Thanks for your reply.
     
  17. Charles Studer

    Charles Studer League Racer Pro Racer

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    2 ¢......
    Have you ever put a 9° .093 axle through a stock wheel.....
    The tune on a 9° dfw IS on paper the best....in my reality....hell No.
    Check the drill to level the body or tiny low nose .....
    Different degree bends can adjust the nose for good and bad
    Focus on getting a great plumb, level, square drill and perfect axle, wheel prep till you are running strong. Then dance with theory.....or suffer the curse of the Cherokee.
     
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  18. Charles Studer

    Charles Studer League Racer Pro Racer

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    Oh and narrow your nose. Just enough
     
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  19. Roadrunner

    Roadrunner Pinewood Ninja

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    Yeah, I know I’m probably overthinking everything . I’m very new to this. Never tried league racing. I want to understand not only what to do, but also why ( more important to me ). I was thinking that if I drilled dfw at an angle, I wouldn’t need much bend on the axle for tuning. Reasonable assumption?
     
  20. DerbyDad4Hire

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

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    Yes
     
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