Regulating T-Jet Downforce

[SouthShoreRacing]

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.

[Maddman]

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.

[Axle]

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.

[keven]

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!

[SouthShoreRacing]

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.

[NicoRosberg.]

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.

[SouthShoreRacing]

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.

[model murdering]

Dom,

How about adopting a simple "lift pin" test and going racing, while you wait for NASA to re-invent the wheel; and measure every pair of blue n whiteys on the planet.

Bill

[Dyno Dom]

Thanks for all the great info. I have a Lucky Bob lift pin which states for T-Jets, we will have to play with that for comparison to more current manufacturer's mags. As SSR suggests, we do plan to use a single scale at race site and for comparison I know my scale measures 2.2g higher which gives me a # for limit.

[BIG E]

Hi Ernie, many of the guys are returning from the pandemic, and they are Fast. Yes, some have stretched the rules during the lax period, let's call it experimenting, but we're attempting to straighten that out. I hope all is well and to see you soon.

Yes, Dom, I know. "Experimenting"... guys like Junior Johnson, Ray Evernham, and Gary Nelson were professionals at the black art. Gary Nelson became NASCAR's policeman and keeper of the building where all the confiscated "experimental" pieces are stored! Hope to see you soon. -- Ernie

[NicoRosberg.]

Experimenting is exactly that. Cheating is when you knowingly break a rule. .

It is quite clear what Big E and Dom are talking about, hence ''experimenting'' - the Quotation marks being key.

[BIG E]

Dom, let's forget this 4 page mess and talk about it on race night. It will be made plain and simple -- certain types of magnets will be allowed, anything else is NOT allowed. If these guys can't get that though their heads, then F them and I'll just have to outdrive 'em! I HATE all this bickering about how much money we can throw at these cars. You know as well as I do that some of these idiots just won't give it a break -- soon they will start in about the tech procedure, and it goes on and on...
See ya soon -- Ernie

[NicoRosberg.]

Surely you won't have to outdrive them, if they try and start with magnets that are not allowed, turf 'em.

[Dyno Dom]

Ernie, At this past Wed, race nite I was presented the subject without having to bring it up. I did question the validity of 3.1 on the club scale and was told it was picked thru evaluation within the span of cars and the # was not at the highest level but somewhere close. The rules do state ANY AW/JL or Dash Blue/White motor mags but apparently some want the 3.1 as a limit to any club racers who might possess a good crop of "legal" Blue/White mags.

[slotn77]

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.

That’s the hope anyway. The bottom line is that there is simply too much disparity between Killer Bee magnets. And having to buy 500 in hopes of getting to where you need to be competitively is silly. I don’t do the Fray anymore because of the magnet situation (and the fact that they permit non-commercially available tires). These two rule missteps have created a situation where only a handful of drivers are truly competing on the same playing field.

My track has a 7.0g limit rule using the house VRP MDM. If your car exceeds that, you just put larger tires on until you don’t. We now mostly run the new OS3 TFX platform. With Black Dragon magnets, this car is hoot to drive. And, of the many we’ve tested, they are all very comparable in terms of downforce. No Dash magnets allowed.