soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 21, 2008 15:39:59 GMT -6
Well, my two sons and I had our first Pinewood Derby last weekend and..I am hooked. We did okay for our first time: my 6yr old came in 1st in his Tiger Den ( 8th overall, time: 4.078s), my 9 yr old won a design award ( 18th overall, 4.102s) and I placed in a Big Dogs race for Dads (4.051s).
There were 4 cars at the event between 3.92-3.98s, separating themselves from everyone else. It was an aluminum 42' Bestrack incline with a 35' straight. Our Pack has very restrictive rules: no oil, no axle polishing (deburr only), no tapers on axle heads, no nickel plated axles, no wheel hub rounding (deburr only), no tread deviations like H or V grooves (we can remove the mold nub in the tread). We can polish wheel bores and we can use anything for weights.
1. Under these restrictions, what are the top 3 things I can do for speed?
2. I found some information supplied by Dr. John Jobe. Very interesting. I am an engineer (but not a mech) and it all seems very good but alot of it seems to be opposite from what I hear and read regarding speed tips. Does anyone have an opinion on Dr. Jobe and his 20+ lecture series?
3. I have read that it is a must to put graphite on the tread area and I have read this is a big no-no. Any opinions?
My goal is make PWD cars, under our restrictions, with times of 3.5s. The track record is 3.90. I look forward to joining this board and increasing my knowledge and sharing knowledge. I am going to post some pictures of our cars for all to see.
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Post by Parrot Racing on Mar 21, 2008 16:30:18 GMT -6
Personally I would not put graphite on the tread, you don't want the wheel to slide you want it to roll. Trust these guys on the boards, there are no faster builders, published or not. Just my opinion, I read just about every single post when I first started and the info is invaluable and you will soon figure out what works best for you, hope you send some cars in for league racing.
Enrico
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Sappington R
Head in the Pine
"The Sappster" 10oz
Posts: 210
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Post by Sappington R on Mar 21, 2008 17:23:10 GMT -6
Hey there soobeesu. I'll give you my three top and something to ponder: 1. If allowed, extend the wb to the max & raise a front wheel. 2. Get your C.O.G. to less than 1" 3. Ride the Rail & Narrow your Front WB If possible, reply in a post with a written copy of your pack rules. Let's compare them to your district. They better be the same. The whole thing seems fishy to me. Never have I seen that you can't polish the axles. I don't know to much about Jobe other than it's very mathematical and scientific- which is fine for many. I personally gravitate more to the art of building rather than the science. Just my opinion. As an engineer, you already have a leg up on me. What's your opinion of all the technical data? Would love to hear more from you + let's see those rules
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soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 21, 2008 17:41:13 GMT -6
Parrot Racing - thanks for the "no graphite " on the treads tip. In the bood I bought at the Cub Scout store, it shows pictures of how to put graphite on the treads so you can understand my confusionn..
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soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 21, 2008 17:43:27 GMT -6
Sappington R- thank you for your reply. Keeping line with our restrictive rules, we must use the standard wheel base but the location of the wheels is of our choice. when you say C.O. G to less than 1", what does that mean? Same for Ride the Rail and Narrow my front WB..what does that mean? I will post our Pack rules...
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Post by Parrot Racing on Mar 21, 2008 17:59:44 GMT -6
Soobeesu, no problem. I am sure some racers do graphite the tread, but if you look at the pictures of the cars on the league boards, you can see the wheels are mostly black. When you put graphite on them they will turn a silver-gray color.
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soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 21, 2008 18:23:53 GMT -6
Parrot - thanks. As I said, I am new but I am hooked...but is also looks as thought I need to type a bit slower! Promise, my spelling will improve!. Any thoughts on Dr. Jobes lectures and his virtual racing software. Being an engineer, I am technically oriented but understand that PWD, like many things, has a fine art aspect that is valuable and essential to making speedy cars...
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Post by DerbyDoc.com on Mar 21, 2008 20:00:00 GMT -6
Log into the wirl race on saturday night. A lot of tips can come from the live chat, and you can ask questions (and be answered) directly. It starts around 7 pm eastern. You just need to go to wirlracing.com, and create a kyte acct. There will be a live chat room on the homepage. If you have yahoo messenger, then PM me your username and Ill add you to the list for voice chat too. Good luck, Tory
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Post by Parrot Racing on Mar 21, 2008 20:06:35 GMT -6
Soobeesu, check your pm's
Enrico
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soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 21, 2008 21:03:14 GMT -6
Parrot - what are "pm's"?
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Post by Go Bubba Go on Mar 21, 2008 22:34:25 GMT -6
Parrot - what are "pm's"? PM = Private Message After you log in with your password, look in the upper right hand corner and you will see a note along the lines of "Hey, soobeesu, you have X messages and Y are new." (If the private message from Parrot is the only one you have received so far, both X and Y will equal 1. ) Click on the part that says "X messages" and it will take you to your In box. Regards, Bubba p.s. note that when you sign in you will also see your PM information at the bottom of the index page under the "Forum Statistics" section on the right, below "Total Members" and "Newest Member".
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Post by Parrot Racing on Mar 22, 2008 0:45:58 GMT -6
Hey Bubba, you were right, only a district race here, no council or anything
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Post by Mayhem Miller on Mar 22, 2008 0:47:58 GMT -6
We graphite the tread on our wheels. My son has had pretty good luck with racing and has won 68 races in a row in the past 2 years, and has never lost a single race since starting scouting, he is the current undefeated district (no council) champion. We graphite our tread... Polish your wheels using micro-gloss and polish the snot out of em with hobby lube. The theory of the wheels sliding down the track if they are too slick in my experience is not accurate, if your wheels are sliding instead of spinning you have some major problems with axle to wheel bore friction. Also, under that theory, you would rather want your wheels sliding down the track instead of trying to force the wheels to turn. Now, the only possible problem that will arise from the wheels sliding is if the rear wheels tend to go into a "death wobble", or anotherwords slide side to side. Not having the wheels polished with graphite may help reduce this, but if your car has the death wobbles, its not going to be a fast car anyway and you need to work on the alignment to get it to run straight. Polish your wheels completely inside and out with hobby lube, its the fastest way down the track.
I would also agree that a 3 wheel rail rider is your best bet. Also, if your rules dont forbid it, cut 1/2 inch off the the back of the car and glue it to the front. This will allow you to move your center of gravity back another 1/2 inch, every little bit helps...
Also, make sure you have your axles tilted upwards slightly (about .002 to .003), this will allow the wheel to ride on the axle head instead of wood portion of the car.
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soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 22, 2008 1:10:50 GMT -6
Miller - thanks for the info. We can cut up the car and glue it back together anyway we want to. I did so on my car. I glued pieces onto the side so that the wheels were in a wheel well. Does this cut down on the drag/friction on the wheels? It seemed to also give the car side to side stability.
We need 4 wheels on the gound...no 3-wheelers allowed.
How do I post some pics of our cars on this website?
I've learned more today than I have in all the time I spent researching...thanks!
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Sappington R
Head in the Pine
"The Sappster" 10oz
Posts: 210
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Post by Sappington R on Mar 22, 2008 9:40:54 GMT -6
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Post by Gravity Steve on Mar 22, 2008 10:52:40 GMT -6
Parrot - thanks. As I said, I am new but I am hooked...but is also looks as thought I need to type a bit slower! Promise, my spelling will improve!. Any thoughts on Dr. Jobes lectures and his virtual racing software. Being an engineer, I am technically oriented but understand that PWD, like many things, has a fine art aspect that is valuable and essential to making speedy cars... Soobeesu, I've looked through Dr. Jobe's lectures and they seem pretty much spot-on. (Physicist here- but I design and build mechanical things, like tools). Is there anything specific that looks fishy? I haven't tried out the race software. I do get slightly different results for the wheel's moment of inertia computation, but then I don't have the same level of granularity in the spreadsheet I developed- it's more of a bulk solution.
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Post by Parrot Racing on Mar 22, 2008 17:08:56 GMT -6
We graphite the tread on our wheels. My son has had pretty good luck with racing and has won 68 races in a row in the past 2 years, and has never lost a single race since starting scouting, he is the current undefeated district (no council) champion. We graphite our tread... Polish your wheels using micro-gloss and polish the snot out of em with hobby lube. The theory of the wheels sliding down the track if they are too slick in my experience is not accurate, if your wheels are sliding instead of spinning you have some major problems with axle to wheel bore friction. Also, under that theory, you would rather want your wheels sliding down the track instead of trying to force the wheels to turn. Now, the only possible problem that will arise from the wheels sliding is if the rear wheels tend to go into a "death wobble", or anotherwords slide side to side. Not having the wheels polished with graphite may help reduce this, but if your car has the death wobbles, its not going to be a fast car anyway and you need to work on the alignment to get it to run straight. Polish your wheels completely inside and out with hobby lube, its the fastest way down the track. I would also agree that a 3 wheel rail rider is your best bet. Also, if your rules dont forbid it, cut 1/2 inch off the the back of the car and glue it to the front. This will allow you to move your center of gravity back another 1/2 inch, every little bit helps... Also, make sure you have your axles tilted upwards slightly (about .002 to .003), this will allow the wheel to ride on the axle head instead of wood portion of the car. Wheel will slide to some extent, whether you think that is good or not is personal opinion. The main purpose of angling the axles or "canting" is to have the wheels ride on the inner edge, reducing friction. Getting the wheels to run out to the head can be achieved without having to insert the axles on an angle.
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soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 22, 2008 23:34:28 GMT -6
Well, I tuned in a bit for the races tonight. I like it. I will enter a car in the near future to see how poor of a carmaker I am and then go from there. My only concern with the Jobe information is that in my experiences with processes, there is a need for fundamental understanding fo what is happening. Scientists usually create a vast array of factors that are supposed to influence an outcome. In reality, there are always a critical few, and all the others are part of the noise of the system. As the variation of the critical few are reduced, other factors start to crop up as being more important than they were in the past.
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Post by Gravity Steve on Mar 23, 2008 19:44:43 GMT -6
Well, I tuned in a bit for the races tonight. I like it. I will enter a car in the near future to see how poor of a car maker I am and then go from there. My only concern with the Jobe information is that in my experiences with processes, there is a need for fundamental understanding for what is happening. Scientists usually create a vast array of factors that are supposed to influence an outcome. In reality, there are always a critical few, and all the others are part of the noise of the system. As the variation of the critical few are reduced, other factors start to crop up as being more important than they were in the past. I feel your pain! There's a lot of misinformation and hyperbole out there. For instance, I have looked at probably every effect to be encountered in terms of what affects the final speed and time, and seen a large variation in what people say about them. I expect that some of them say it to lay people off the trail, but some of what I have seen is pretty good. There really is no reason that the sport can't be analyzed. But then, the "art" still comes into play, depending on the kind of track- long, short, whatever. That can still be analyzed. I'm working on it, but I just started. I have a spreadsheet (top secret <.< >.>) that has 10 worksheets on different effects. Some are of minimal contribution, but how are you to be sure until you do the work? Agreed, this is a physical system with few variables, and will yield to the probing mind with the tools necessary...but do remember that a lot of people have done that homework, and now it's down to milliseconds for the advantage, once you are past the vagaries of a particular track. Edit to add: Only psuedo-scientists who are posers pull that "too many variables" trick- not blaming you, just saying I see that all the time, some smart guy throws out some tecnical terms, and everybody ducks. There is little in the world these days that is that far out of the common understanding. You just have to dig in and ask the right questions.
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soobeesu
Pine Head
MicNic's Garage
Posts: 36
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Post by soobeesu on Mar 24, 2008 11:10:50 GMT -6
As promised, attached are the Derby rules for our pack. My questions revolve around wheel and axles alteration:
1. Wheels can be deburred but inner rim cannot have material removed. I would like to thinkI can use the shaver to eliminate the small ridge.
2. Wheels can be deburred, like the modl nub on the tread. I would like to think I could use the shaver to remove the mold nub in the tread. The rules say no lathe, but as I asked our Pack folks, they are tyring to prevent against wheels turned on a large industrial lather where someone might put in an H-groove or create a V-groove. I think I can use the shaver as a deburr tool and then some sandpaper on top of this...
3. Axles deburr only. I would thinkI could use some sandpaper after a metal file deburr to remove the fine burrs. No "polishing" is allowed. I could go down to 1000 grit?
I used the shaver on some old wheels last night. Nice tool! The wheels were great.
soobeesu
Revised 1/8/2007 Highlight denotes Rule updates from 2006 for the 2007 Racing Season Unit Participants and General Ground Rules All cars must be accompanied by the registered Cub Scout who made the car. Cubmasters are not required to collect winning cars after pack races. This annual race is open to the 1st place finishers from each age group (Tiger, Wolf, Bear, and combined Webelos) plus one at-large entrant or up to five total entrants at the discretion of the unit Pinewood Derby Race committee from each Cub Scout Pack registered in the Williamson Road District. The first entrants group is suggested, as there will be awards given out by age category as outlined below in the Awards section. All rulings by the Race Marshal(s) are final. The race will hold to the following procedure: First a qualifying round will take place with all age groups and cars combined. Then, from the total field, the top 12 qualifiers will be selected to advance to a championship round. During the qualifying round, each car will race once in each lane for a total of three races. The average of the times from those races will be used to determine the rankings. In the championship round, the cars will again race one time in each lane for a total of three races. The average times will again determine the rankings. The derby car must be constructed using the official B.S.A. Grand Prix Pinewood Derby Kit during the current 2006/2007 Scouting year. If a car becomes damaged or is causing disruptions in the race and causes two re-runs total, it will be removed from the current heat. If the car can be repaired in a reasonable amount of time {3-5 minutes}, such repairs can be made in the Repairs Area. If the car can re-enter the race, it will be re-inspected and placed in the last of the qualifying heats. If not, the car will be disqualified. An Adult Race will be held at the conclusion of the boy’s event which will be open to any parent or leader. There is a registration fee of $10 for this race. There will be a run-off scenario identical to that of the boy’s races. Adults must build their own cars and their cars must meet all of the same specifications as the boy’s cars. Adult cars will be placed in their own pit area. Length, Width and Clearance The maximum length shall not exceed 7 inches. The maximum width, including wheels & axels, shall not exceed 2 ¾ inches. The wheelbase (the distance between the centers of the front & rear axels) must equal 4 ¼ inches with a tolerance of +/- 1/8”. NOTE: You are not required to use the slots provided for wheel axels. The minimum width between the wheels must be 1 ¾ inches so that the car can clear the guide rail strip on a standard Pinewood Derby Track. The minimum clearance between the bottom of the car and the center track rail shall be 3/8 of an inch so that the car can clear the guide rail strip on a standard Pinewood Derby Track. Weight, Design and Appearance Cars may not weigh more than 5.00 ounces or 141.75 grams. Cars exceeding the weight limit may be brought into regulation in the Pit Area. The reading on the scale by the Race Marshall is final. Details such as steering wheel, driver, spoiler, etc. are permissible, so long as there are no loose materials. If loose materials exist, they must be fastened securely in the repair area or removed from the car before being permitted to race. All cars must be designed so that the entire car and wheels rest behind the starting peg. No pointed front ends that extend beyond the starting peg will be allowed. Cars with wet paint will also not be allowed. Wheels, Axels and Lubrication ONLY Official B.S.A. Grand Prix Pinewood Derby kit body, wheels and axels may be used. Axels, the nail, and the wheels may be de-burred ONLY. Any additional alteration to the wheels or axels will disqualify the car. This includes, but is not limited to, beveling, tapering, thin sanding, wafering, lathe turning or removing plastic from the inner wheel, the imaginary rim. Official wheels and axels will be on hand for purchase for car adjustments in the Pit Area. Wheel bearings, bushings, washers and hubcaps are prohibited. The car shall not ride on any spring. All cars must be freewheeling, with no starting or propulsion device. No lubrication oil of any kind may be used. Axels may be lubricated with powered graphite only. No lubrication will be allowed after the car passes inspection. ALL FOUR wheels of the car must rest entirely on the track. No camber (tilting of the wheel axles to force the car to run on the inner or outer edge of the wheel) or lifting of one wheel off the track is allowed. Registration and Inspection All cars will be registered at check-in and given a race number, via a small sticker placed so that it is clearly visible on the top of the car. All cars must pass a pre-race inspection before competition. If a car does not pass inspection {too long, too heavy, altered wheels, etc.} the ‘driver’ will have an opportunity to bring the car into compliance in the Pit Area. If the car cannot be brought into compliance before race time, it will not be allowed to race. No car may be altered after it has passed inspection, and as such it will impounded and placed into the pit area by race officials. Cars damaged during a race or removed because of disruptions to the race will be allowed to be repaired at the discretion of the Race Marshall(s) and will be subject to re-inspection before being allowed to continue racing. Awards and Recognition Each participating Scout will receive a limited edition patch. Each Scout will only be eligible to receive only one award during the racing or judging competitions. If a Scout wins an age group and also wins an overall award, they will receive the overall award as the higher recognition and their age group award will be presented to the next eligible Scout. Trophies will be awarded for the 1st, 2nd, and 3rd place finishers of the each age group (Tiger, Wolf, Bear, and Combined Webelos) as well as the 1st, 2nd, and 3rd place finishers in the entire district. There will also be additional award categories judged by the race officials for style, creativity, etc. For the adult race, the 1st through 3rd place winners will receive gift certificates good at the Arnot Mall Scout Shop. Award denominations will be $25, $20, $15. All adult participants will also receive a participation patch. Conduct of Parent’s, Siblings and Scouts The most important value of the District Pinewood Derby is the participation of the parent and son in building the car, along with good sportsmanship and learning how to follow rules. Parents are responsible for their younger children at all times. Running about the gym and under the bleachers is not allowed. Food and Drink are not allowed in the gym – PERIOD! Un-Scout-like behavior by Scouts, leaders, parents or guests will be grounds for expulsion from the competition and/or building.
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