We're already building. Help with some decisions?

[GrantnHayden]

We're in mid-Michigan, and this is my first post. I have read MANY topics here over the past few months and have gotten great info.

My son, Grant and I have started a few body designs for the upcoming Pinewood Derby. He took 5th as a Tiger with 'Blue Car' and last year he was very fortunate to take 1st in his Pack and then took 2nd amongst Wolves at Districts. In fact, his car the 'Fluke' (named afterwards!) beat a fellow Wolf's car (once in three heats) that ended up taking Grand Champ!

I'd post a picture of Fluke, but I have to figure that out another day.

Fluke was a bright yellow three wheeler with unmatched wheels of many molds. The body was an inch tall wedge with beveled sides and rear end. We used two 3/8 x ~3" zinc bolt shafts for weight to 142g. They were inserted from the rear just above the axles and stuck out the back 1/4" like tailpipes. COM was approximately 1.5" in front of the rear axle with elongated wheelbase. Alignment was very good except I discovered afterward that the rear driver side axle was toed in slightly (could have been the diff that cost us District Champ). Axles were sanded with 600 grit then with pumice and the head was beveled. Wheels were properly sanded at the hub, tread and inside edge. We did not have a test track. Oh, and we used Hob-E-Lube.

So, this year I am looking to build a test track and I am researching cheap timers. I am hopelessly pineheaded now! We'll use Tungsten rod this time around to push COM rearward, which I found can be cut with a hacksaw and jigsaw. We have new matched sets of #2, 4, 5, 10, 12 and 18 wheels from last year's stock purchased recently. We will be sanding the axles with successive grits from 600 to 3000. I may start with 400 and jump to 1200 on up and test. I weighed about 40 kits and found a body that weighed only 81g! HEL will most likely be our lube.

I like the BSA endorsed book by David Meade called 'Pinewood Derby Speed Secrets' and will be following that closely. So this leaves the questions I have been wondering about and need advice on.

1) I like the idea of a Fast-Start device like the bent paper clip mounted to the front extending up to 2" giving a quicker start. I need to see if it is legal here but is it a sound idea? Shall I wait until after the rules are published to bring it up? Last year's rules did not specifically exclude such a mod.

2) What is the best method to check rear axle alignment?

3) If we use the better wheel molds is the Pro-Wheel Shaver XL really needed? I will be getting an axle press.

4) I was lured into buying WS2 (Tungsten Disulfide) off Ebay and apparently it is not a good lube alone. Does anyone know the ratio of Moly to Graphite in HEL? I am too curious not to experiment with a mix of WS2 and Tube-O-Lube or other fine graphite.

I know this is a LONG post. Please forgive. Better now when it's slow I'm thinking. Thanks.

[gpraceman]

Welcome to DerbyTalk. I'll touch on a few of your questions.

I like the BSA endorsed book by David Meade called 'Pinewood Derby Speed Secrets' and will be following that closely. So this leaves the questions I have been wondering about and need advice on.

You do have to be careful. Some of his tips are not allowed by most race rules. It seems that the BSA gave their endorsement without reading the book. Always check your rules to make sure you will be legal.

1) I like the idea of a Fast-Start device like the bent paper clip mounted to the front extending up to 2" giving a quicker start. I need to see if it is legal here but is it a sound idea? Shall I wait until after the rules are published to bring it up? Last year's rules did not specifically exclude such a mod.

Do you mean a so called "cheater bar"? Most tracks have a gate that is spring loaded to open, so the gate moves away from the cars before they have a chance to start rolling. That trick only helps if the gate is held closed by a spring or rubber band and it takes wrist action to open the gate. Then it only helps if the start gate operator is being slow.

3) If we use the better wheel molds is the Pro-Wheel Shaver XL really needed?

It does help to get wheels from the "better" mold numbers, but there is a lot of variation in the manufacturing process regardless of mold cavity, so some prep is still needed. Some wheels more than others.

[Pinewood Daddy]

I like the BSA endorsed book by David Meade called 'Pinewood Derby Speed Secrets' and will be following that closely. So this leaves the questions I have been wondering about and need advice on.

2) What is the best method to check rear axle alignment?

3) If we use the better wheel molds is the Pro-Wheel Shaver XL really needed? I will be getting an axle press.

4) I was lured into buying WS2 (Tungsten Disulfide) off Ebay and apparently it is not a good lube alone.

We use Stan's method for alignment. http://members.aol.com/standcmr/lbw4c.htm#e I still have thoughts that this was created to torture newbies!! Try it and you'll wonder too!!

Wheels will alway be out of round and tapered to some degree. Truing the OD to the bore is the only way to get good wheels. We inspect ours and select the one with the least amount of runout before truing them.

We used Doc Jobe's method of polishing and lubing last year and smoked everything, including anything else we've built. http://www.pinewoodderbyphysics.com/lectures.shtml The only problem is the lube doesn't last long. The key is "less is more". Previously we would load up the wheel bores and spin it in. 2 years ago I noticed the cars got got slower after a few races and found the graphite was caked into the bore, slowing them down.

[GrantnHayden]

Randy -

Yes I have heard it called a 'cheater bar' here. We have a starting gate that is hand/operator actuated with the typical aluminum round rod dropping down. They pull back from underneath the gate to drop the rods and allow the cars to roll down the track. I think we have a longer 40 some foot long track, high quality with aluminum lanes.

If I understand what you are saying about the cheater bar, it will only give us significant improvement if the start gate operator releases the gate slower than normal. I am thinking then that introducing something like this could actually gain us and the Pack more negative attention than it is worth, considering we have never seen a cheater bar used in the Pack or at Districts. It could be disqualified on the spot at Districts correct?

[gpraceman]

If I understand what you are saying about the cheater bar, it will only give us significant improvement if the start gate operator releases the gate slower than normal.

That is correct. If the gate is opened slow enough, the cars will start rolling but will be restricted by the pins. Cars that contact the start pin higher up will be able to move farther than those with low noses, due to the angular movement of the pin. They get a bit of a head start. If the pins drop straight down, it would not matter at all, but I have not seen a gate like that.

I am thinking then that introducing something like this could actually gain us and the Pack more negative attention than it is worth, considering we have never seen a cheater bar used in the Pack or at Districts. It could be disqualified on the spot at Districts correct?

Some people may frown on it, due to the "cheater bar" nick name, but I don't recall seeing a set of rules that prohibit having one. If you prohibit cheater bars, then you'd have to prohibit all cars with high noses, which would greatly limit design creativity.

[GrantnHayden]

Daddy -

Thanks for the referrals. I am familiar with Stan's sound practices. He is omnipresent here - aren't you Stan?!

I think I'll just run the car backwards to align the rear wheels.

We will be lubing similar to Doc Jobe as well, it seems you are saying that you may use less dry lube this year or change to another lube, huh?

I was swayed by their Debunking of the 'three wheeler' principle that we used last year. That makes me wonder if I should put all four wheels on the track this year. BUT it worries me to change too many things since we did so well last year! Do most racers do the three wheeler mod?

Todd Lee

Grant is 8
Hayden is 2

[Pinewood Daddy]

Daddy -

Thanks for the referrals. I am familiar with Stan's sound practices. He is omnipresent here - aren't you Stan?!

I think I'll just run the car backwards to align the rear wheels.

We will be lubing similar to Doc Jobe as well, it seems you are saying that you may use less dry lube this year or change to another lube, huh?

I was swayed by their Debunking of the 'three wheeler' principle that we used last year. That makes me wonder if I should put all four wheels on the track this year. BUT it worries me to change too many things since we did so well last year! Do most racers do the three wheeler mod?

Use Stan's method for checking alignment. Use the Florian Alignment Calculator. You can use whatever method you like to when it comes to adjusting the alignment. We've had some success with the bent axle method, it's easier, but it's not as precise.

We used Doc Jobes SuperZ graphite with his polishing methods with great results. Unfortunately the 1 molecule thick application only last 6 to 8 races before requiring re-application which then means you have to redo the alignment. Our cars slowed in the District finals race last year.

Who "Debunked" 3 wheelers??!! I've had good results with a few 3 wheelers I've built. Our District rules require 4 wheels on the floor. I do the alignment so the left front wheel bears no weight. If your rule allow it, then do it!

Last season there was alot of discussion about using positive camber (axles tilted up) of about 2 to 3 degrees. This changes how the wheel bore contacts the axle shaft, extreme angling will cause the wheel to ride on the inside edge. The wheel also rubs on the smooth axle head instead of the body. The force pushing the wheel onto the axle head can be reduced by angling the axle forward.

Last years car could have been a "fluke" as you've named it. Our cars did fantastic at the Pack race (old wooden track) but so so at the District race (new aluminum track). There are too many variables out of your control to guarantee how you'll do on any track. We sure found that out! There's plenty of reading to do here to see what other people have had success with. With the right tools and methods they can help you improve your times. Like you said, making too many changes at a time can possibly reverse the success you had last year, but using proven methods and procedures can't hurt to try.

[GrantnHayden]

Daddy -

The URL you gave me for Doc Jobe, 'pinewoodderbyphysics' had Lecture #11 - Debunking Another Friction Myth that shot the wheels out from under the Three-Wheeler modification.

[Pinewood Daddy]

Daddy -

The URL you gave me for Doc Jobe, 'pinewoodderbyphysics' had Lecture #11 - Debunking Another Friction Myth that shot the wheels out from under the Three-Wheeler modification.

3 wheeling is more effective when combined with Rail Riding. I'm sure you've read a few threads about that! Keeping the raised wheel lightly on the rail can increase the speed of the car significantly. The advantage is the car isn't losing speed due to bouncing back and forth of off the rail as it rolls down the track.

I align for 2" of drift over 4 feet. The drift should be smooth not abrupt. Watch the movement of the wheels on the axles as you roll the car down a slight incline (Stan's method). If a wheel dives in or out that will take a couple of feet before the pull of the wheel affects the roll of the car.

[blcrow33]

Pinewood Daddy,
I thought when rail riding, the raised wheel should not hit the rail because it would take more energy to get that wheel spinning? You want the wheel that is touching the ground to ride on the rail.

[Pinewood Daddy]

Pinewood Daddy,
I thought when rail riding, the raised wheel should not hit the rail because it would take more energy to get that wheel spinning? You want the wheel that is touching the ground to ride on the rail.

DAMN!! Your right!! I haven't thought about PWD in a few months. Yes, we lift the left wheel and drift left. I think I remember a discussion of riding the lifted wheel. I think if the non-rotating wheel was to catch on a lane guide track joint it would cause more speed loss than if the rotating wheel caught it. If that makes sense, I'm not awake yet (4 hours sleep).

[Dice]

GrantnHayden, 3 wheelers are faster. Lecture 11 was debunking a friction myth. Most pinewood speed books state that raising a wheel decreases friction by 25% when it really decreases rotational energy by 25%. It's easier
to start 3 wheels rolling than 4.

Good luck at the races.

Dice

[Go Bubba Go]

We're in mid-Michigan, and this is my first post.

Congrats on the first post, and welcome aboard!!!

I have read MANY topics here over the past few months and have gotten great info.

Us, too! Although my boys really get their info second hand (Dad reads and digests, then teaches them "hands on" style).

My son, Grant and I have started a few body designs for the upcoming Pinewood Derby.

Starting early, and with several designs... Great!!!

I'd post a picture of Fluke, but I have to figure that out another day.

Check out the Stupid question - How do I post pictures? post. I believe that closed the final gaps for us (FYI we do use Photobucket for our pics).

So, this year I am looking to build a test track and I am researching cheap timers. I am hopelessly pineheaded now!

You're not alone, by any means. Have you and the boys shared the "Down and Derby" movie yet? Get the Scouting edition - great interview with Don Murphy.

I like the BSA endorsed book by David Meade called 'Pinewood Derby Speed Secrets' and will be following that closely.

Rules of BSA races are established locally and vary widely. Hopefully your Pack rules are at least in agreement with your District and/or Council race rules. There will likely be some suggestions in his book that might fall outside your rules (we can't raise a front wheel or cone wheel hubs, etc.) and others that are within your rules (we can use a Quick Start bar and do use his axle bend method for alignment).

1) I like the idea of a Fast-Start device like the bent paper clip mounted to the front extending up to 2" giving a quicker start. I need to see if it is legal here but is it a sound idea? Shall I wait until after the rules are published to bring it up? Last year's rules did not specifically exclude such a mod.

Find out who your local rules "official" (typically the PWD Chairman) is and address your questions to him. Better to address the questions early than have controversy at check-in time. Also, weighing in before the rules are published for this year gives you the opportunity to argue for any revisions you would like to see.

2) What is the best method to check rear axle alignment?

Check out the alignment section of Stan's On-line book Learn to Build A Winner. This info is also found (on license, I believe) in MaxV's "Speed to the Finish" book. (We like MaxV's book and video - I recommend you pick up a copy of his VHS while he still has them, he is closing them out and hasn't published a DVD version yet).

3) If we use the better wheel molds is the Pro-Wheel Shaver XL really needed? I will be getting an axle press.

Your tread surfaces will still need some work to, at a minimum, remove the mold marks (see Meade's book on this). Our local rules are pretty strict and do not allow any lathing, but you can "lightly sand" just enough to get rid of the mold marks / imperfections. Regarding the Derby Worx Axle Press - nice tool!

4) I was lured into buying WS2 (Tungsten Disulfide) off Ebay and apparently it is not a good lube alone. Does anyone know the ratio of Moly to Graphite in HEL? I am too curious not to experiment with a mix of WS2 and Tube-O-Lube or other fine graphite.

Not really my topic. We have recently been using Tube-O-Lube.

I know this is a LONG post. Please forgive. Better now when it's slow I'm thinking. Thanks.

Slow = opportunity for undivided attention from some of the hardcore pineheads. Good time to ask long questions.

[DerbyChamp]

gpraceman wrote:

You do have to be careful. Some of his tips are not allowed by most race rules. It seems that the BSA gave their endorsement without reading the book

Hi folks, this is David Meade. I just want to be sure everyone understands the the BSA did go over my book with a fine tooth comb before they gave their endorsement. In fact, before the book went to print they gave us a rather lengthy list of corrections and changes they wanted to have made.

As for the issue of rules vs. methods discussed in the book... we all know that the rules for any given race are established by the local race committee. There are many BSA races held every year, which allow every method described in my book. There are also races which have a much more restrictive set of rules. In the book I specifically instruct the reader to find out what their local rules are going to be and then use only those methods which are legal given those rules.

The intent of the book is to provide a complete building guide which teaches principles and incourages good sportsmanship.

Best Regards and Happy Racing,

DerbyChamp

[derby doc]

David Meade, Your book is excellent. Like you said, BSA races are held locally across the country and the rules vary from pack to pack. It would be very hard and restrictive to limit the book to the most restrictive rules out there. A+ on the book