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Thread: Slot Car Racer Today

  1. #3136
    Join Date
    Feb 2005
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    Chesapeake, Va.
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    804
    Gearbear
    I"m using .540 arms also. The tip to tip gap has very little to do with the arm diameter at least in my case since I use wedges to install the magnets. I use wedges to retain the maximum amount of magnet material and since the magnets have a different thickness, even from the same manufacture, I sometimes have to hone the magnets to get the air gap I want. Then again in the case of the T-5 magnets I'm using some hit the air gap I wanted for my GP12 .518 arms and some ended up with more of an air gap than I needed. I saved those setups to try with my B-Prod PS arms that were giving me the push start problem since those arms were .540 and the natural hole that the full thickness magnet gave me was almost .550. I usually run an air gap of .560 with my .540 arms. Therefore I only had to remove .010 of magnet material to get the air gap I needed.
    Quote Originally Posted by GearBear View Post
    Fred,

    On your motors, are you using .518" diameter arms or .540" diameter arms? I'm pretty sure that George is using .540" diameter arms. That might explain the difference in the magnet tip dimensions.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  2. #3137
    Join Date
    Feb 2005
    Location
    Chesapeake, Va.
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    804
    tnttires
    You are absolutely right when you say that the air gaps you have have no effect on the .518 arms no matter what the timing. The reason the PS Contenders have the problem is because the arm stack width is wider that any of your GP12 arms. I also have PS and Koford .518 arms and none of them give me any problems in setups where the north to south tip to tip gap is less than .305. That is because the stacks of the GP12 arms cannot span the distance between the tips, they always settle either towards the north or south magnet and never perfectly between both tips. Due to the width of the PS Contender stack it can settle between both tips and that causes the dead short that forces the motor to be push started.
    I wasn't refering to the X12 arm thet George put in the push start can as an eye opener. I was refering to the switch from the Cahozza can to the PS can when he cured the push start using the same arm. George stated that the tip to tip gap was wider in the PS can and that confirms my theory that a wider tip to tip gap will cure the problem.
    Quote Originally Posted by tnttires View Post
    How did that confirm anything he put another arm in the setup with the push start and it worked fine. The arm that needed to be push started in another setup and it worked fine..
    I have 8 Cahoza setups 7 with Koford M607 .450 long and 1 with Camen .450 long magnets. Each 1 has the tips between .269 and .272, not one has ever had a push start during breakin.
    I use Pro Slot Copper Hardware on both P/S and Cahoza endbells. 4 have Koford GP-12 and 4 have P/S GP-12 arms all with the timing is between 38 and 45 degrees. 515 to .518 diameter with .530 to .533 ag still no push start.
    I do have 1 K arm that developed a short after about 200 laps and now requires a push start and it is a full 1/10 slower than it was initially. I have tried it in 3 setups same problem in all.
    So this arm doesn't get to play anymore.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  3. #3138
    Join Date
    Feb 2005
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    Chesapeake, Va.
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    804
    Mic Byrd
    It really doesn't matter if your using flat tip or bevel tip magnets. The tip to tip measurement is made between the north and south tips and is unaffected by what tip configuration you use. On a beveled tip magnet the measurement would naturally occur between leading and following edges of the bevel tips the first and last portions of the magnet to act upon the arm. It would be awful hard to get an accurate tip measurement of the inside edge of the bevel tips and besides that gap would actually be smaller than the gaps of flat tip magnets.
    Quote Originally Posted by Mic Byrd View Post
    with a tip gap of .385 they could be beveled tip t2 mags
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  4. #3139
    Join Date
    Feb 2005
    Location
    Chesapeake, Va.
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    804
    Just so everyone will understand this a litte more clearly and I hope I don't confuse anyone. I use a math ratio formula to show the necessary tip to tip width. I use known measurements that work (my BOW motor) to find the gap that will work with the PS Contender arm. Here's the formula I use and how I use it.

    A= Gap in setup that works with Bow arm
    B= Bow arm stack width
    C= The PS Contender arm stack width
    X= the necessary tip to tip gap to cure the push start problem

    The ratio reads like this; A:B::C:X ... It says A is to B as C is to X. Here is a problem using numbers that are not the actual measurements but just shown so you can see a correct result.

    .275 : .312 :: .325 : X Multiply .312x.325 and you get 101.400. Now divide 101.400 by .275 and you get .368 which is X and the gap that will work in this case. Remember this is not actual gap and stack measurements just a way to show you how to get the answer to this problem. You will have to use your actual A,B, and C measurements to find X and the correct gap needed to cure the push start problem. If you don't have a motor that is working correctly to make these comparisons then I'll make mine available when I'm sure they work. I also believe a .540 arm will have to be compared to a .540 arm. I don't think a comparison can be made to a .518 arm. Although you can try if you want to.

    Keep in mind that there may also be an underlying measurement we haven't included in this problem. While all arms are 360 degrees (a circle) in diameter the width of the stacks use different amounts of that 360 degrees. The BOW stacks less then the PS stacks. The gaps between the stacks are also different. The BOW gaps are wider than the gaps in the PS arm. I still feel that if the tip to tip gaps are increased to the width the ratio problem says, the problem will be cured. I'm going to try out this theory next week.
    Last edited by Fast Freddie; 09-22-2012 at 09:49 AM.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  5. #3140
    Join Date
    Aug 2010
    Location
    Arizona
    Posts
    621
    I usually tip 20%....

  6. #3141
    Join Date
    Aug 2010
    Location
    Arizona
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    A= Gap in setup that works with Bow arm......this is the air gap in can or distance between magnets?
    B= Bow arm stack width .....this is the diameter of the stck?
    C= The PS Contender arm stack width ........

  7. #3142
    Join Date
    Feb 2005
    Location
    Chesapeake, Va.
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    804
    EdC
    A=The tip to tip gap of the north and south magnets. (The gap we have been talking about all along.)
    B= The width of the arm stack (web) not the diameter of the arm. Many arms have different stack widths. I have an old X12 RJR arm that's very narrow.
    C=Yep you got C right it is the Contender stack width.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  8. #3143
    Join Date
    Aug 2010
    Location
    Arizona
    Posts
    621
    FF I understood but maybe someone else didn't, maybe a diagram for some would help?

    http://www.mathworksheets4kids.com/a...-of-circle.jpg

  9. #3144
    Join Date
    Jun 2009
    Location
    New Jersey
    Posts
    1,201
    Fred
    I get everything your saying here except the gap on Beveled tip mags being smaller then flat tip mags.beveled tip have no tips to speak of so in my mind that gap will be larger then flat tip mags every time.I myself haven't had this problem and I use both PS and Bow Contender arms mostly with t-5 magnets at .560 to .565. are these new arms or have they been out for balance? in theory a well balanced arm shouldn't stop in the same spot every time to cause this problem.
    Motors By Mic B
    Balance By PoppaPower
    A Clean Slot Car is a Happy Slot Car
    Garden State ISRA Club Home of the Anaconda
    Tires by the Hermanator
    www.TheISrausa.com

  10. #3145
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    Feb 2005
    Location
    Chesapeake, Va.
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    804
    Mic
    Your right I did screw up with the bevel tipped magnets as far as the inside measurement. If you measure the tip to tip of the north and south magnets on the inside it would in fact be wider than the outer edge measurement. Technically speaking the bevel tip magnets have two distinct edges the inside edge of the bevel and the outside edge of the bevel that act on the arm at different times. The outside edge is first then the inside edge. Unless magnetic theory has the beveled edge projecting a magnetic field at the same angle as the bevel in which case the action of the magnet would occur much sooner then I thought. That would mean that the whole beveled edge of the magnet would act to push or pull the arm with a much greater amount of magnetic force then the conventional straight tip magnets.

    If you want to see what I mean by the arm settling between the magnets take a .540 Contender arm and put it in a setup with a north/south tip to tip gap of .300 or less and free wheel the arm in the setup. What you will find is that the arm will settle perfectly between the magnet tips, not always but sometimes. That is what causes the push start. By the way I run a .560 gap also.

    Why don't you measure the north/south tip to tip gap on the contender setups that do not have the push start problem. I would be intrested in knowing what the measurements are and if they are straight tip or beveled tip magnets. Thank you Fred
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  11. #3146
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    Feb 2005
    Location
    Chesapeake, Va.
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    804
    EdC
    The formula is the simplest one I could come up with. A simple ratio formula using known measurements that work to find a measurement that would be exact for the arm being used. If one works then in theory the other should also work. I also use the same ratio formula to find common tire size and gear ratio final drive numbers. Sort of like if a .8125 tire is using a 39T spur what would a .750 tire need to use. Both using the same pinion gear. The final drive ratio should be very close. It will also work with pinion and spur combinations.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  12. #3147
    Join Date
    Jan 2011
    Location
    Richmond, CA
    Posts
    1,279
    We had a really successful test day out at TNT Raceway, Modesto, Calif. The Hillclimb is really a great track to test NASCAR and we got a number of cars to run in the 4.6s and one broke into the 4.5s including the 16D motor where I regapped the magnets. The .575" airgap as recommended by The Jaybird worked very well....lots of brakes and the .560" PS arm is a good one after all. I just need to get one more arm for the Brazilian set up that was also regapped to .575". Might head up to SCR today to get one after meeting Hermanator at Starbucks.

    The Corkscrew was a blast as usual. I used it just as a shake down for the four GT12s and four LMPs ready to go. Frankie offered to turn the computer on for times, but I found it was better not to go for lap times but rather to observe how the car was running. Sometimes I think it is easy to just watch the clock and it takes away from a good analysis of how the car is going around the track. I did observe more and have some changes to make between now and the first NORCAL race in Rocklin.
    Journeyman Industrial Slotcar Worker, Teamsters Local 3299 AFL-CIO
    Now with "Improved Karma"

  13. #3148
    Join Date
    Oct 2011
    Location
    Roseville, CA
    Posts
    146
    Looks like you're gearing up to run a season in NASCAR as well, George????? 4.5's for a NASCAR there, in Modesto, is definitely a winning car. That's fast!! See ya in a couple weeks! On a completely different note.... AXLE BEARINGS. I installed a new set of bearings in a GT12. After testing Saturday, I noticed what looked to be an axle spacer floating around near the motor. I thought that was odd seeing this particular car doesn't have any spacers. After looking a bit closer, I noticed it was the piece of the bearing that covers the little balls. I'm guessing I should replace these brand new bearings yet again??? Or is it safe to continue on minus the little cover???
    Jay Herrod

  14. #3149
    Join Date
    Mar 2005
    Posts
    564
    Was it the dust shield or the retainer that spaces the balls apart? Dust shield is not a problem.... ball spacer is a big problem.
    Why do I do this to myself?

  15. #3150
    Join Date
    Oct 2011
    Location
    Roseville, CA
    Posts
    146
    Wallbasher, it appears to be the dust shield. All the balls seem to be spaced properly and stay that way as I rotate the axle. Thanks!
    Jay Herrod

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