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gpraceman wrote:If those photos don't put it to rest, maybe this from Bill Launius at Derby Worx, ...
Randy--you sure know how to put a damper on my desires to concoct conspiracies. At least this lets Rod off the hook for any Canadian involvement (for now).
So much for my ramblings involving economics...we are now clearly in the realm of Physics! Since I am neither an Economist nor a Physicist, I don't really know where this is going!!!!
I will see what I can do to extract some measurements form the pix you posted, estimate the MOI of these new wheels, and run some simulations comparing the 2009 wheel to the 1991 wheel.
RacerX wrote:The B.S.A. dose not consider this to be a big change or improvement, just a reworking of the existing designs due to age and wear, also it is not a announced change or improvement ...
This just confirms to me that my suspicions were correct. The desk jockeys at BSA really do not know their customer base as well as they should, nor have they considered the possible impact of their changes.
With what appears to be from the pictures a inner whole on the outside of the wheel at the wheel bore area.
will we now not mushroom the axle head ? As it will be interesting to see if this will actually cause more friction ? Or will the new way to go, be coning the axle head in so the rim of the axle head only touches ?
won't really know until I too have some to look at and play around with.
Then will the local packs and council change the rules about coning ? What about that mold mark ? if there is no imperfections to remove. will the council and local pack in are area still allow trueing of the outter wheel ?
Will there be tools that are out on the market that will be effected by this new wheel and have to do a newer version of tool ? Or eliminate a tool ?
Many of us, may be left waiting for what the pack or council or district is going to do on the new wheel and how they will deal with it.
Are pack and council does not allow for coning. If they come right out of the box or wheel kit. Then certainly they are going to have to adjust there rules here. Then they have only allowed the mold mark to be removed, now if there is no mold mark. Then how will they address this ? then if they say no, then what do you do with older wheels ? do you allow both to run ? have two sets of rules for the wheels ?
This will certainly be interesting to see how this all plays out with the rules down the road.
First, a mea culpa. The wheel we currently know and love is the 1999 wheel in the argot of the most venerable Doc Jobe. The 1991 wheel was phased out in 1999. Somewhere in the midst of the heat of battle of trying to determine the veracity or fallaciousness of the new BSA wheel, a cosmic ray must have flipped a bit in my memory bank corrupting the precise data stored in the location of such valuable information. Alas, no one was fooled and I don't think any critical decisions were based on such suspicious hypothecations.
Now, on to much more important matters that will cause a unique combination of euphoria and dyspepsia in most folks skilled in the fine art of PWD racing. Yep, my economic instincts concerning the impact of the new wheel design on the moment of inertia in nonrelativistic Newtonian mechanics are well founded--even though, as mentioned previously, I am neither an Economist nor a Physicist.
Well, through the miracle of Excel along with an ability to count pixels in the pix posted by the Jeffe of DerbyTalk, along with some not so sophisticated scaling based on the brilliantly displayed readout of a set of digital calipers (no pixel counting here!), I have arrived at a very crass approximation (yes, I know it would be better to use the word crude, but, alas, I haven't typed the word crass in such a long time, that I just couldn't resist the use of a poorly chosen synonym---which brings us one of the true mysteries of English---why is there no synonym for the word synonym?) of the MOI of the 2009 wheel and compare it to the MOI of the 1999 wheel.
2009 wheel
mass 2.8g
moi 3.6g*cm^2
1999 wheel
mass 3.6g
moi 5.1g*cm^2
The listed mass is a cross-check from the MOI calculation done with graphical integration to see how well I have estimated the cross-sectional area and gives an idea of the accuracy of the MOI. Based off my pixel counting exercise, it appears that I am a bit over weight compared the PE reported weight of 2.6g which likely means my estimated MOI is a bit on the high side.
Now, with all the above caveats and mea culpas, my fellow pinewood derbians, such a difference provides quite a distinct advantage for the 2009 wheels on a 30' to 50' track.
And, as Stan has appropriately pointed out, the devil is in the details and we won't know for sure until someone gets their hands on a set of the new wheels and tests them out.
These numbers are close enough (within 10%) to Jobe's 4.7 g*cm^2 for the 1999 wheel, but don't seem to match well with Lastufka's measured MOI of 0.00006 oz in ^2. (I must need a "gravity constant" somewhere in the conversion!) It is noteworthy that the percentage change in MOI between the 1991 and 1999 wheels is much less than the change between the 1999 and 2009 wheels!
Before jumping to conclusions, though, we need to quantify the effect of reduced wheel diameter and the change in bore diameter (if any) on bore friction losses. These offset the reduced losses due to MOI reduction.
Stan
"If it's not for the boys, it's for the birds!"
priority wrote:Or a concerted conspiracy effort by Canadians to wreck havoc on American PWD racing?
gpraceman wrote:That is the most likely scenario. The ring leader is Rod Turnbull.
OK, you got me... the plot was to get you guy to sell off all your current stock piles of wheels to us in Canada at ridiculously low prices. Getting the new molding marks where not any harder than any of the other machining work that needed to be done to create the illusion of a new wheel... the tricky part was getting enough of them into circulation to get you guys to notice them.
And thanks for the nomination Bubba... Priminister Turnbull... has a nice ring to it... but no, my head might swell even bigger, at which point it would surely explode.
Last edited by Rod Turnbull on Thu May 28, 2009 10:21 am, edited 1 time in total.
Stan Pope wrote:
...
These numbers are close enough (within 10%) to Jobe's 4.7 g*cm^2 for the 1999 wheel...
Doc Jobe has an "updated" calculation of the 1999 wheel in Lecture 5 on his web site that is different from his book. It is a bit closer to my numbers.
Frankly there has been no point in keeping track of mold numbers or lists you have all published on which wheels are best than others... but I do find it interesting and a valuable resource for those who can actually use the data. It has got me wondering about the history of the wheels we use up here. Now from what I have read here there seems to be a few years that changes have been made... 85, 91, 99... and some of you have been around long enough to see the pros and cons of the changes... now if we are using a refurbished mold from BSA days gone by, which year mold are we using? Someone mentioned 91 being preferred over 99 or something like that... is there a way to tell the years apart? This would make the charts of which mold numbers are good a valuable asset to us in Canada... and might give you guys a supply of the preferred years (which might be a moot point if the new wheel end up being that much better).
Oh and did Bill call us crazies?
'also it is not a announced change or improvement as some of the crazies think it should be'
Pinewood Daddy wrote:And a slight redesign of the wheels!!
That's just crazy talk Daddy... they are still kinda round and have a hole the the general cental area... nothin's really changed man, just chill... everything will be copasetic...
how recessed is the wheel bore whole on the outside of the wheel ?
Those who have these wheels, any info to share ? Will you still be able to mushroom the head of the axle and not create a performance issue ? Or does the recess prevent from mushrooming ? As in meaning it would actually create more friction ?
Input !!!
Are there different mold numbers on the wheels ? I see (1) on the one pictured ?
With raising the axle slots / wholes. will the smaller o.d. wheel have any effect ? With less room under the car ?
It will be interesting to read the info and reports from users as they test and check them out.
how recessed is the wheel bore whole on the outside of the wheel ?
Those who have these wheels, any info to share ? Will you still be able to mushroom the head of the axle and not create a performance issue ? Or does the recess prevent from mushrooming ? As in meaning it would actually create more friction ?
Input !!!
Are there different mold numbers on the wheels ? I see (1) on the one pictured ?
With raising the axle slots / wholes. will the smaller o.d. wheel have any effect ? With less room under the car ?
It will be interesting to read the info and reports from users as they test and check them out.
