New BSA Wheel and Axle??

General topics of interest to racers and race coordinators alike.
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priority
Master Pine Head
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Re: New BSA Wheel and Axle??

Post by priority »

Pinewood Daddy wrote:COME ON!!! Someone produce some wheels!!! We have to know what the real differences are, not theoretical.
I made a few phone calls today; calls to Scout Shops in my area are a bit entertaining..."Are you serious?". It turns out that the new wheels are scarcer than hen's teeth. The best bet for someone to get their hands on a set is to go to Scout Shops in Minnesota and sort through their stock with a scale.

With respect to theoretical versus empirical data, take a look at Doc Jobe's Pushing the Speed Limit Lecture....
http://www.pinewoodderbyphysics.com/pdf ... e%2020.pdf ... and decide for yourself how trustworthy Newtonian mechanics are at predicting a PWD car's performance.

In the same vein, I appreciate Stan's "optimism" that there will be some detrimental effects of the 2009 wheel design. However, I have recently run way too many simulations varying the radius of the wheel and estimating the reduction in the effect of friction with a smaller bore to no avail. Yep, they can help narrow the performance gap, but not enough to overcome the lower MOI. I don't think my efforts are making me jump to conclusions, but I am past of the point of starting to loose faith.

Call me crazy...you won't be the first, or, for that matter, the last.
Last edited by priority on Thu May 28, 2009 8:21 pm, edited 1 time in total.
priority
Master Pine Head
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Re: New BSA Wheel and Axle??

Post by priority »

sporty wrote:...

how recessed is the wheel bore whole on the outside of the wheel ?
....
Sporty
Perhaps someone out there in DT land has access to Alicona software. The sell some high $$$ software that can take two 2D pictures from different angles and render a 3D model. With this and bit of math, the depth of the recess could be determined.
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gpraceman
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Re: New BSA Wheel and Axle??

Post by gpraceman »

priority wrote:I made a few phone calls today; calls to Scout Shops in my area are a bit entertaining..."Are you serious?". It turns out that the new wheels are scarcer than hen's teeth.
Many people may not realize that the new wheels are any different. They pretty much look the same from the outside. Even the inside changes may not be as obvious as it is to most of us here. So, maybe they are more common than it seems. BSA has kept their retail outlets in the dark, so many of the scout shops have no clue, as you have seen, that there are new wheels and axles out.
priority wrote:The best bet for someone to get their hands on a set is to go to Scout Shops in Minnesota and sort through their stock with a scale.
With the newer tube packaging for the wheel/axle sets, I wonder if you can just do a visual inspection of the hubs. You can also look for the registered trademark symbol ® on the outer sidewall (older wheels have the TM symbol).
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Re: New BSA Wheel and Axle??

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I contacted the National Office earlier this week and received the following response today:
In January 2009 We made an in line change in regards to our PWD wheels. We introduced 4 new colors and changed the packaging.

There were no modification changes made to our wheels.

These are the same quality wheels that we have been producing and are exclusive to Boy Scouts of America.
This response came from the Derby Product Manager.
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sporty
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Re: New BSA Wheel and Axle??

Post by sporty »

Thats interesting as the release of the colored wheels was in December.

seems there is some confusion with who knows what.

Sporty
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Re: New BSA Wheel and Axle??

Post by gpraceman »

12yearsrunning wrote:I contacted the National Office earlier this week and received the following response today:
In January 2009 We made an in line change in regards to our PWD wheels. We introduced 4 new colors and changed the packaging.

There were no modification changes made to our wheels.

These are the same quality wheels that we have been producing and are exclusive to Boy Scouts of America.
This response came from the Derby Product Manager.
Maybe you can send him the photos posted here and see what he has to say. To me, it really seems like a lack of communication issue within the BSA.
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Darin McGrew
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Re: New BSA Wheel and Axle??

Post by Darin McGrew »

FWIW, when CSB changed its wheels about 20 years ago, we just issued the leftover old wheels to the adults in our all-comers class. Of course, we didn't have a regional derby to worry about, and we didn't have anyone obtaining different (yet still official) kits from other sources.

As a BSA outsider, it sounds like they changed the trademark symbol, which was supposed to be a trivial cosmetic change, and in the process they changed the shape and weight of the finished wheels. Since it wasn't a planned change to the wheel specs, the non-pineheads in the organization will find out about the change from the pineheads, since pineheads are the ones who will notice and care about the change.
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Re: New BSA Wheel and Axle??

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gpraceman wrote: Many people may not realize that the new wheels are any different. ....
I believe you could be on to something. I may try to visit the closest Scout Shop and engage in proper scientific investigation test out your hypothesis if time permits in the next few days.

And...no peanut gallery comments from you fellow pineheads who may feel the urge to lampoon me for suggesting there may be something more important in life than PWD and that I should be able to set my "priorities" (a pun on my DT name -- get it?) so that I KNOW I will have time to visit the Scout Shop this weekend!
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Re: New BSA Wheel and Axle??

Post by Rod Turnbull »

Darin McGrew wrote:As a BSA outsider, it sounds like they changed the trademark symbol, which was supposed to be a trivial cosmetic change, and in the process they changed the shape and weight of the finished wheels.
I like this theory... now lets add to it: lets made the die slightly larger so in 5 or 10 years we can just retool it to freshen it up and get another 5 or so years out of it... that would account for the slight difference in size. :scratching:
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Re: New BSA Wheel and Axle??

Post by Bones »

Just an FYI. Glenn Jewkes has gotten and tested the new wheels. For those who are interested take a look.
http://pddr.proboards.com/index.cgi?boa ... 098&page=1" target="_blank
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Re: New BSA Wheel and Axle??

Post by sporty »

I took a look and it's good post with good information.

Sporty
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Stan Pope
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Re: New BSA Wheel and Axle??

Post by Stan Pope »

The test is helpful and seems well structured to avoid extraneous variables, but falls short of giving really useful information for many on this board.

First, the track used is not the typical Cub Scout track. As described it the Cub Scout Leader's How To Book, the racing distance is approximately 28 feet has a gradual change in slope. The observed time differences are probably less on the shorter "Cub Scout" track.

Secondly, comparing "out of the box" wheels tells us little about how they would perform if they were "dressed" in the way that most of us would, especially since it was noted that the new wheels are "cleaner" (lower run-out, etc.) out of the box. How much of the 0.014 sec reduction is attributable to lower inertia and how much to lower run-out and other quality issues? (Each gets some credit I suspect.)

The test does tell us that the new wheels "out of the box" are probably inferior to well prepared old wheels but superior to old wheels "out of the box."

Now, can someone derive times for these test runs if they had run on a 32' Piantedosi with all three (or four) functional wheels swapped out? With wheels well prepped with less than 10% mass removal?
Stan
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sporty
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Re: New BSA Wheel and Axle??

Post by sporty »

I gather and get a real feeling. That this new wheel, is going to give the regular scout. Who does not do much prep work to the wheels, if any. A muche better wheel with less chance of having the old wheel typical imperfection wheels, due to mold mark, wobble and ect.


Naturally I would also think that if the new wheel was well prepped. I see no reason for it not to perform better than the old wheels.


Now The old wheels, with all the prep work done to them will likely be just as fast. But the average scout does not, repeat does not do much to the wheels.

Since most packs will now face rule changes, atleast ours for sure.

Depending on what the rules are going to say. It could very easily make a much more level playing field.


Certainly can not imagine why it would not be a plus / plus for everyone. Who wants to buy a ton of wheels to go through them to find a few good sets ?

I hope that the new wheels would be good enough to reduce or eliminate this.

Sporty
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Post by priority »

Bones wrote:Just an FYI. Glenn Jewkes has gotten and tested the new wheels. For those who are interested take a look.
http://pddr.proboards.com/index.cgi?boa ... 098&page=1" target="_blank
Unfortunately, some of Mr. Jewkes' assumptions violate the known laws of physics (and integral calculus and solid geometry and ...)

Let's start with the assertion that most of the weight reduction is from the smaller hub. Well, from solid geometry (or integral calculus for those that prefer highfalutin' methods), the mass of a hollow cylinder of polystyrene is the density of polystyrene times the volume of the hollow cylinder (rho*V in short). A little time with calipers and some math and we find the ENTIRE HUB OF THE 1999 WHEEL WEIGHS 0.324 grams. In other words, if your remove the entire hub completely, the 1999 wheel will weigh 3.3grams!!!! Now we know that some of the hub has been left on the 2009 wheel, so I took a few liberties with a cross sectional drawing and measurements from the earlier pictures and found the new hub weighs around 0.15 grams. So the reduced hub accounts for a weight reduction of around 0.17grams. The impact on MOI is approximately 0.014 g*cm^2 so Jewkes is correct that this is not much of a change.

Let's move on to the assertion that the rim being thinned by about 0.018 thinner and does not significantly affect the moment of inertia or the weight. First rho * V (mass of the reduced wheel rim) of the 1999 wheel is about 2.0 grams!!! Taking off 0.02 inches off the inside of the rim reduces the weight by 0.25 grams!!! That is almost as much as eliminating the center hub altogether. The effect on the MOI is about 0.4 g *cm^2 (about 3x that of the reduced hub) assuming all the mass reduction comes from the inside of the rim. The reason for the large change in MOI is due to an r^3 term in the calculation of the MOI, so mass farther away from the center of rotation is MUCH more important in addition to the volume swept by the rotation of a thin strip with relatively larger radius. (NB-I used 0.02 inches so that it is easy for others to check my assertions using Doc Jobe's lectures.)

So, let's take Mr. Jewkes at face value. The hub reduction in weight is about 0.17g plus the reduction in weight reduction by a thinner rim of about 0.25g is 0.42g. Where is the the other ~0.6 grams of weight reduction? Something is missing, perhaps in the sidewalls, or perhaps in the measurements. Based on my estimates earlier in this thread, my guess is a bit of both.

What have we learned? The MOI of the new 2009 wheel HAS to be MUCH lower than the 1999 wheel! There is simply no way to reduce the weight of the 1999 wheel by 1g without this being true!!!!!
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Re: New BSA Wheel and Axle??

Post by Stan Pope »

Jewkes OFF FORUM wrote:most of the weight has been removed at the hub and where it has the official BSA made in USA markings.

the rim part of the wheel is bout .018 thinner...
PRIORITY wrote:Let's start with the assertion that most of the weight reduction is from the smaller hub.
His original text appears to account for the weight you cant find. I've changed it to bold face to help identify it in his text.

Please tone it down a bit!
Stan
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