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  • SouthShoreRacing
    replied
    Experimenting is exactly that. Cheating is when you knowingly break a rule. Pushing the boundaries of the rules has always been part of the game.

    Let me know when you find a way to take a cheap scale and turn it into a reliable tech tool that gives consistent readings across many instances of that tool.

    Wrong again. That guy will still buy 500 pair or magnets or a huge number of armatures, etc. to get as close to the limit.

    Instead of *****ing about people attitudes because they aren't doing what you think they should be doing, how about you do some work and actually contribute something useful. It'd be a refreshing change.

    Leave a comment:


  • NicoRosberg.
    replied
    The problem is that is people keep dissing these meters, they won't get better, and 'experimenting' (as per the earlier comment. In reality, cheating) will continue.

    If the devices are used more, warts and all, there will be an incentive to improve them.

    Eventually the guy who buys 500 magnets looking for the magic pair will find he has wasted him time and money.

    That has to be a good thing, but it won't happen with current attitudes.
    Last edited by NicoRosberg.; 10-18-2021, 10:37 AM.

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  • SouthShoreRacing
    replied
    I agree the tools are useful for building and comparing cars, but that data doesn't work unless the same scale/tool is always used. I can tell someone my car reads 6.0 on my Doane meter, but if they measure it with their meter it more than likely will return a different reading.

    The big issue with the inconsistencies is for those racing with multiple clubs. Even if those clubs follow a national set of rules such as HOPRA or ECHORR. Those groups provide the rules, but offer nothing as to how to reliably and consistently tech against the guidelines they have set. You could end up showing up at the ECHORR Challenge or the HOPRA Nats and find out your car is out of spec even though it was within spec based upon the tools you were using. This is the same as the minor differences in tech blocks, etc. The differences from tool to tool is too big. I have yet to see any national organization put any effort into addressing this.

    Leave a comment:


  • keven
    replied
    Originally posted by Axle View Post

    Even with all that, I still think the Doane scale is useful as a building tool. Based on my own testing, the ECHORR limit of 6.5g is actually pretty high.

    I measured 4 of my SS cars on my Doane scale.

    Dash chassis / Killer Bee: 5.0
    Pro-Built RR SS/ Blue/White: 4.2
    SS1 Aurora / Killer Bee : 2.2
    SS2 Aurora / Blue/White : 3.8
    Well, maybe if u try black dragon or pepper or magic polymers with taller tires, you could get a 6.5G reading…
    that sounds fair!

    Leave a comment:


  • Axle
    replied
    Originally posted by Maddman View Post
    They type of measuring device or technology used isn't the point. The availability, accuracy and repeatability of the measuring device is. A one-off homemade device is nice but doesn't make the cut. Currently the only widely available device is the one sold by WHP. They say that they are accurate and repeatable. Real world measurements say that they are not. Given that the device is a homemade modification of an inexpensive gram scale the likelihood of multiple devices providing the same reading is laughable.
    I completely agree in principle. I picked up one of the same HF scales before I saw the Doane scale, and for the HF scale I own I'd say the repeatability and precision is very poor. At the most basic level, it has a range of 1000g and folks are asking it to accurately measure to 0.1 gram. I later bought a cheap 20g scale that reads to 0.001g, and that's probably about good enough to be useful for +/- 0.1g. This would have been a much better starting point for the Doane scale.

    The other challenge is that accurately measuring magnetic attraction is very hard. The relationship between magnetic force and distance is very non-linear, and it's very likely that the T-jet magnet strength varies quite a bit over their surface and length. Even with a prefect scale, building something that would be very repeatable from unit to unit is extremely difficult, and even just small variations in how the car is positioned on the scale can make a big difference. Also, given that the physical geometry of the magnets and rails can make such a big difference, any scale that isn't using the exact same rail material, rail spacing, and rail-car distance is may not actually represent the actual downforce on the track.

    However, I still think even with all of these issues, the Doane scale can be a useful tool. And in some specific cases, I think it could work as a tool for tech inspection.

    The key is that the racers in a club would need to have access to a single scale that is the reference tech scale. If that's possible, then folks can confirm their cars are legal before race day, and can do a rough calibration between their own scale and the reference scale. Sure, the reference can drift over time/temp/etc., but the reference scale could be paired with a dedicated reference car. I think that could be manageable. However, I do think that without access to a reference scale the Doane scale is lacking as a tech tool.

    Even with all that, I still think the Doane scale is useful as a building tool. Based on my own testing, the ECHORR limit of 6.5g is actually pretty high.

    I measured 4 of my SS cars on my Doane scale.

    Dash chassis / Killer Bee: 5.0
    Pro-Built RR SS/ Blue/White: 4.2
    SS1 Aurora / Killer Bee : 2.2
    SS2 Aurora / Blue/White : 3.8

    The two Aurora chassis are cars I built to race with the local club (when that was still a thing). Even with the Dash Killer Bee magnets, my first SS car was way off at 2.2g. The second car was closer at 3.8g, but still below the pro-built car I later picked up. And a random Dash chassis I just pulled out of the bag and put SS wheels on blows them all away.

    This is very informative. The Doane scale makes it clear that I should do the work to find a much better set of magnets. If I showed up with a car that read even 5.5 on my scale, I'd probably have a better car. And even with the expected variation between any random Doane scale I'm not too likely to go above the 6.5g on the reference tech scale. But I could also bring a set that read 5.0 on my scale, just in case.

    As I said before, it will be interesting to see if that rule turns out to be manageable and stick around. It seems like it could work, if folks want to make it work.

    Leave a comment:


  • Maddman
    replied
    I am not opposed to downforce checking. I think it is reasonable that any "meter" needs to be available to all so that they can build a car at home and know it will be legal when they show up for the race. I have very little confidence in any of the readily available devices. Obviously a one off "homemade" device doesn't make the cut.

    It sounds like more testing is required before this "meter" can be used a accurate measurement device. Any measurement device must be available to all interested parties at a reasonable price. And multiple measurement devices need to provide readings within a known tolerance. This tolerance is then incorporated into the rule.

    Sounds like the rule makers need to go back to the drawing board and figure this out.

    Last edited by Maddman; 10-18-2021, 07:43 AM.

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  • SouthShoreRacing
    replied
    Originally posted by NicoRosberg. View Post

    How much difference, in percentage terms?
    I'm not sure what you are trying to get at. May share that so people know what you are trying to get at. I don't know we didn't calculate it as it. We were at a race and had the four scales side by side and measured a few cars. They were in-line cars for our Spec Racer class. A couple of the scales were within a 3 or 4 grams. The others were more than 10 grams off from what I recall. It was a race day so we weren't going to spend a lot of time on experimentation of this. We did not test any other type of cars, so we don't know if the variance is linear or not. The bottom line is the scales in their current form do not meet the requirements to be promoted as standardization tool.

    Leave a comment:


  • RichD
    replied
    A person could compare the readings taken of his own cars with the club scale VS the readings of the same cars taken with his home scale. If the readings were not the same a fudge factor could be applied. The bar on my homemade scale can be shimmed to raise or lower it, the scales that my 1/32nd club used were the same. The scales were kept in sync by using a calibration magnet.
    As far as the scales themselves go they only resolve 0.1 gram. If a car reads 28.3 grams the true reading could also be 28.2 grams or 28.4 grams. I designed a scale that gives bigger numbers so that small errors would be less significant. The scale that I use can be calibrated and I do have a certified calibration weight for it.

    Leave a comment:


  • NicoRosberg.
    replied
    People will want to build legal cars at home.

    How can they do that if their scales don't read the same as the house ones?

    It would be like having a 33.33mm width rule, but your calipers read different to the ones that would be used for tech on race day.

    Leave a comment:


  • Eric Peterson
    replied
    Why wouldn't the house scale be accepted? Reason #21 why I didn't win the race, the Downforce scale isn't the same as mine. Really?
    These type of rule discussions turn people off from organized racing.
    Dom saw that back 20 posts ago I think.

    Leave a comment:


  • NicoRosberg.
    replied
    Originally posted by SouthShoreRacing View Post
    We have had 4 scales side by side and they all read different for the same the car.
    How much difference, in percentage terms?

    Leave a comment:


  • Maddman
    replied

    Ohms Law states that the current between two points is directly proportinal to the voltage across the two points. The usual mathematical equation that describes this relationship is I=V/R. Where I is the current through the conductor in amperes, V is the voltage measured across the conductor in volts, and R is the resistance in ohms. There are national and world standards for I, V and R. Your DMM is not one of those standards.

    Previous posts in this thread have indicated that different WHP downforce measuring devices have provided different readings for the same car. That's enough for me. I don't have such a device. However, considering the materials used in the measurement device and the way is was manufactured it is more than reasonable to expect inconsistent readings from device to device.

    Perhaps those orgs who have adopted a downforce measuring device have their own data that they can share on how they determined the accuracy of the device and the value of downforce listed in their rules.

    My thoughts are that the goal of some posters is to divert, deflect and confuse. That is not my intent.

    Leave a comment:


  • RichD
    replied
    How about Ohm's Law?

    Leave a comment:


  • NicoRosberg.
    replied
    Lawn?

    What do you mean?
    Last edited by NicoRosberg.; 10-17-2021, 01:41 PM.

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  • smalltime
    replied
    Originally posted by NicoRosberg. View Post

    What are the numbers?
    Wow.
    Way to give a homework assignment to an Electrical engineer.......don't you have a lawn to care for?
    Last edited by smalltime; 10-17-2021, 01:39 PM. Reason: spelling, what else

    Leave a comment:

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