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Choosing roller diam size and effects from choice!

Discussion in 'General' started by Philip Henzig, Dec 31, 2018.

  1. Philip Henzig

    Philip Henzig Screw

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    Hi I have looked all over online and can't seem to find info on why one would choose a given roller size. if the overall diamensions (car width) within the track is the same what effect does the roller diam have on the cars speed or performance?
     
  2. ltr74

    ltr74 FRP Popsicle

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    I have not tested this yet, but everyone says:

    Smaller diameter rollers should go through corners faster while larger diameter are more stable.
    Plastic ringed rollers have less grip on the walls so they are faster than metal rollers
    Larger diameter rollers go through digital turns easier.
     
  3. Philip Henzig

    Philip Henzig Screw

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    Thanks Lock Nut So I would suppose the reason for this would be contact area, as the smaller dia roller would have less contact area then the large roller right?
     
  4. SignOfZeta

    SignOfZeta Spacer

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    It’s not the contact area that maters is the distance between roller centerlines.

    Imaging you have a hallway to run blindly down and your aid is a pole with wheels (rollers) at each end. If the wheels are smaller and the pole wider you’d feel more stable than if the pole was more narrow and the wheels larger.

    The walls of the track have more leverage over the car when the rollers are smaller and the roller centerlines (the effective width of the car itself) are wider. When the wheels are bigger and the car narrower the car will move faster through it, especially in the straights. It’s also spinning slower which means less friction from the bearing. Smaller dia rollers however are more stable, especially in the corners.

    There may also be other considerations. For example if you are running stock bumpers you need 19mm just to reach the max width. With wider parts though you can use smaller rollers.

    The rubber/plastic/metal thing is all about friction. The more there is the more stable the car is but the speed will be reduced everywhere. All metal is lowest, then the beveled plastic, then round plastic, then rubber.
     
  5. Philip Henzig

    Philip Henzig Screw

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    SignofZeta Thank you for the detailed explaination! The reason I asked this is because I bought the Evo 1 Ms chassis and it came with the white nylon 9mm rollers. I built the kit and thought as I was building it those little rollers won't be as good as the 17 mm blue plastic tipped metal ball bearing rollers I just bought so I installed them in the correct location according to the manuel with the kit. The car was terrible it fell off every where. SO I then installed the 9mm white rollers that came with the kit and adjusted the bumpers for the correct mounting position according to manuel and all of a sudden the car handels great and dosn't come off at all. so thank you for explaining this as I was very puzzeled.
     
  6. ltr74

    ltr74 FRP Popsicle

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    The problem was probably that by using plastic ringed rollers in the front, there was less grip from the rollers for it to stay in the track. It was also likely that the 17mm rollers were faster but changing to the non-ball bearing rollers slowed your car enough that it would stay in.

    Every single thing I have read says smaller rollers of the same type are faster but less stable. Up until this year most racers were running 19mm in open/tamiya class to keep that stability. It's just in the past year that we have seen the switch to the supposedly faster 13mm rollers. I am hoping I can actually test this when I get back from vacation.
     
  7. tarutaru

    tarutaru Screw

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    Most typical setup that I've seen are 2 x 12-13mm on front, 4x 19mm on back, or 2 x 19mm on front, and 4x 19mm on back. I've also seen some with 2 x 12-13 mm front and 4x 13mm on back.

    17mm is rarely used, Ive only seen them run on top of 19mm as tilt guard or sometimes as roller assist on some variations of the pivot bumpers.
     
  8. Philip Henzig

    Philip Henzig Screw

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    Thanks Tarutaru, Ok now because I'm new to this hobby I would have to ask the obvious question If a wide car and 19mm rollers are the hot setup why does Tamiya not make wide bumpered cars OR large rollers included in the kits as stock?
     
  9. Roscoe_tm10

    Roscoe_tm10 Spacer

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    I'm gonna make a new videos which will cover most of the basic stuff. Meanwhile, you can watch this old video to get the basic idea:


    Watch my other videos for more information, tips & trick, tutorials in Mini 4WD Hobby.

     
    Crazy_bikerdude, Aaron and yao wei like this.
  10. Philip Henzig

    Philip Henzig Screw

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    Thank you Roscoe!
     
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  11. Crazy_bikerdude

    Crazy_bikerdude Box Kit

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    Great video Roscoe!
     
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