Eagledad Posted February 7, 2012 Share Posted February 7, 2012 >>My lab has 5 such instruments and all of them read exactly the standards accurately. Link to comment Share on other sites More sharing options...
drmbear Posted February 7, 2012 Share Posted February 7, 2012 I just say that for this race, we are using THIS scale. Doesn't matter what any other scale says. Link to comment Share on other sites More sharing options...
packsaddle Posted February 7, 2012 Share Posted February 7, 2012 drmbear, how would you respond if a parent or leader arrived with a standard and proved 'THIS scale' was inaccurate? Link to comment Share on other sites More sharing options...
DeanRx Posted February 7, 2012 Share Posted February 7, 2012 yeah Barry... I get what you're saying. It doesn't matter the diameter of the bulls-eye so long as all the shooters have the same size bulls-eye to aim at, right? There will always be discrepancies and the more accurate / sensitive the scale used, the more likely you will weigh a car the night before and have it be fine, then weigh it in the morning and have it be over due to moisture or some other issue. A few tricks that have worked for us.... I have a medical grade scale good to 0.001grams. This is a blessing and a curse. The airflow over the sclaeplate can actually affect the reading. A kid barely touching the table at the other end of check in can affect the reading, etc.... So.... we have the check in scale on its own table, we calibrate it regularly throughout weigh-in (with provided reference weigh), we make sure the bubble level is level and we recheck if it ever gets bumped. The goal is to make it as fair to every car as we can. Remember its much easier when weighing in grams to 141.75grams, than trying to hit 5.0 ounces. Spend the little extra $$ and get a scale that at least goes to a tenth of a gram! 0.1 ounce out of 5 ounces is 2% of the total car weight. 0.1grams out of 141.75grams is 0.07% of the total car weight... far, far more accurate. If your scale takes anything over 5 ounces, say 5.00001 and rounds to 5.1 (because that is its accuracy) then you have a potential varriance of up to +/- 2% of total car weight between cars that check out at the same weight !!! Get the most accurate scale you can, calibrate it, then test all the cars the same. This minimizes varriance and any other potential bias in the testing. Link to comment Share on other sites More sharing options...
frank10 Posted February 8, 2012 Author Share Posted February 8, 2012 I'm not a derby nut, but I thought it was neat that there was a way for me to know which scale would be best to use next year. And finding one that only involved going to the store and picking up a new roll of quarters seemed worth sharing. Link to comment Share on other sites More sharing options...
Jeffrey H Posted February 8, 2012 Share Posted February 8, 2012 We have one official scale...period. Our derby rules clearly state this with no exceptions. Adjustments to the weight can be made before race time. I'm grateful that I have parents that don't really care that their car does not weigh in at 5 ounces. Many are happy with 4.7, 4.8. Easy-going parents - thank goodness! The Pack winner this year was a car that weighed-in at 4.8. Weight is a factor, but it will not give the desired effect if the wheels and axles have not been prepared. I witnessed many cars that were 5.0 oz and did not fair well. PW Derby is not my favorite event - Too much planning, too much preparation, workshops, and too much hoopla for a 20-minute race. I'm always glad when it's over. If I could take it off the pack calendar I would. Link to comment Share on other sites More sharing options...
Gunny2862 Posted February 8, 2012 Share Posted February 8, 2012 At the risk of being ridiculous(maybe reDUMBculous) and having been a certified scale technician. 1) Properly certified scales, handled properly, subject to the same environmental conditions, and certified in place will read together barring scale malfunction or misplacement of the weight. So unless you can't properly certify the scales including performing ACCURATE and PRECISE calibration, there isn't a problem using multiple scales. 2) Proper certification, even of a gram scale, includes cornering. Even a scientific scale in an air box, unless otherwise directed in it's manual, should not just read correctly in the center of the weight plate(up to a certain percentage of it's capacity at which it is understood that certain tolerances apply) but at all four corners also, up to a certain percentage of the capacity of the scale where of course tolerances apply. The issue is that people who don't REALLY know anything about a scale will think that they can certify a scale. AND then people who want to get by with .000001 of a difference wouldn't pay an additional $20 each to get the local Scale company to provide a properly set -up scale and maybe even a tech to operate it for an hour or two - - and if they did would still complain that the guy didn't know what he was doing..... Derby's are crazy, accept it and move on... Link to comment Share on other sites More sharing options...
Basementdweller Posted February 8, 2012 Share Posted February 8, 2012 20 minutes is all wow that is sad. Ours went significantly longer than that.....we used perfect n and every boy raced every lane twice. After that the sibs and adults raced.....then we had grudge matches..... those who were tired, bored left after the main feature finished......It went on for another two hours......... We had Mario kart races and brackets, wii projector......We built car stands......we made pinewood necker slides...... We had lunch....... It was a blast. Link to comment Share on other sites More sharing options...
packsaddle Posted February 9, 2012 Share Posted February 9, 2012 I agree basementdweller, our derby would start at 0900 and go until 1500, in separate age classes plus an overall race. Dens would cook hotdogs and families would bring desserts. The Boy Scouts would attend as finish line judges and even if they weren't racing themselves, the cubs watched the others in a carnival atmosphere. It was ALWAYS one of the annual highlights that started around Halloween and culminated in the derby around this time. Interesting, they weren't all that enthusiastic about going to the district derby, at least not compared to the pack derby. I mean EVERYONE would have fun, siblings, parents included. I'd get reports back from parents about how the boys had talked for hours after about how they planned to improve their cars the next year... PWD was just fine. Edit: Gunny, we contract with one of your counterparts to do regular servicing and calibrations. The electronic ones are usually kind of boring but it is fascinating to see someone working on one of the old Mettlers with the glass knife edges, etc. I even have one of the really old museum pieces with the glass box, chains, and pans. Reliable even when the power is off...nice.(This message has been edited by packsaddle) Link to comment Share on other sites More sharing options...
Scoutfish Posted February 9, 2012 Share Posted February 9, 2012 WEll, we tell everybody that :"Tis is the official scale. We do not care if you weighed your car at NASA before the race...this IS the offical scale. Period. " And every now and then a parent will say our scale might be +/- "X" number of grams, etc... WE say : "OKay, but it's off that much for EVERYBODY ! Everybody still gets judged on the same scale of scale! WE bring our scale out at both PWD workshops and at the track test run day that we have a week before PWD. WE also tell everybody to stay off the table. Do not lean against, bump or touch the scale table. And I don't know about anybody else's scale, but I can just breath on ours and watch it change by at least 2.2 ounces. Link to comment Share on other sites More sharing options...
qwazse Posted February 9, 2012 Share Posted February 9, 2012 whatever you do at weigh in, encourage your boys to build solid cars that they can maintain and repair for years. Our boyscouts have a no-holes-barred PWD where they pull their old cars off the shelf. If it can make it down the track, it can race. modifications include duct-taping wrenches and soup cans to the cars. however, modest weight adjustment with a properly placed propeller seems to work best! Link to comment Share on other sites More sharing options...
John-in-KC Posted February 9, 2012 Share Posted February 9, 2012 Pack, Supply Corporation? Common Sense? No, the weights I referred to were commercially available. Link to comment Share on other sites More sharing options...
packsaddle Posted February 9, 2012 Share Posted February 9, 2012 John, not sure what you're asking but I don't remember the name of the contractor. I have two sets of standards: one made by Troemner and one by Ohaus. Both Class 1. As I remember I paid about $800 for the oldest set about 25 years ago. The most recent set was much more expensive - inflation I suppose. Time didn't change their mass though, lol...that dastardly uniformitarianism thing again. (This message has been edited by packsaddle) Link to comment Share on other sites More sharing options...
shortridge Posted February 9, 2012 Share Posted February 9, 2012 Of course, it doesn't work that weigh! Scoutfish, you're getting sent to the pits for that groaner. Link to comment Share on other sites More sharing options...
Scoutfish Posted February 10, 2012 Share Posted February 10, 2012 You saying I was weigh out of line? Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now