Generally speaking: grooved or not for oil? Graphite?

[TimInOhio]

Generally speaking, and with all things being equal, and with wheels that are essentially BSA stock, would grooved or non-grooved axles be faster for graphite? If we get lucky and get the graphite-only restriction lifted for next year, would grooved or non-grooved axles be faster for oil?

Thanks.

[FatSebastian]

Generally speaking...

Tim, we had come to believe that the conventional wisdom was that no grooves are preferred with graphite. The explanation seemed that there was a potential to over-lubricate by trapping excess graphite in the grooves, taking more runs to get up to maximum speed. We have very little practical experience with liquids, but thought that grooves are okay liquid lubes.

Hopefully some others will better experience in this area will chime in.

[TimInOhio]

Generally speaking...

Tim, we had come to believe that the conventional wisdom was that no grooves are preferred with graphite. The explanation seemed that there was a potential to over-lubricate by trapping excess graphite in the grooves, taking more runs to get up to maximum speed. We have very little practical experience with liquids, but thought that grooves are okay liquid lubes.

Hopefully some others will better experience in this area will chime in.

Thank you for the reply, FS.

[sporty]

K,

Now in my own experience, I have not really seen any real gains over grooved axles with graphite.

But I have seen gains with larger grooved axles with graphite.

meaning stock grooved axles, I have not. But others may have.

The larger grooved axles with graphite I have.

And yes, grooved axles with oil, is always better over non grooved.

Sporty

[FatSebastian]

But I have seen gains with larger grooved axles with graphite. meaning stock grooved axles, I have not.

Presumably this means an "oversized" axle having a larger diameter than stock (rather than grooves that are extra wide).

So does the benefit come from the groove, or the larger diameter? That is, with graphite, is an grooved oversized axle an improvement over an un-grooved oversized axle?

[xanthrum]

Just my opinion... our cars have progressively gotten faster and faster each year - the cars that took first and second place in the adult division at the Mid America Pinewood Derby - As well as the cars that took first and second place in the qualified scout division and the fifth place car in the kids division - all were running on grooved axles with graphite. They are much faster than any cars that we have build using non-grooved axles. Many factors contribute to a fast car but an excellent axle is very important... I would be willing to say that the fastest cars in the thousands that I see every year... all are running grooved axles... and with oil a grooved axles is preferred, but more importantly the process in polishing the inner bore the outer hub, inner hub... we use a very unique process with graphite and burnish the graphite into legends or red rocket - after we use novus 2 & 3 - we also use a combination of several different types of graphite... it is messy job but when done right the wheels / axles combination are smoking fast. I should also mention the process in polishing the axle is very important... all of these processes are as important if not more so than if the axles has grooves or not.

Hope that helps a little
Greg

[Speedster]

Thank you, Greg. I was wondering if your cars had grooved axles. I think many of the DT cars that finished in the top 12 of the Adult graphite only Division were running grooved axles. Our 2 cars both had grooved axles with a combination of .093 and .091. That just happened to be the set up that gave us the fastest speed on my wood track. We prepped our wheels as Greg described. Whether grooved axles help or hurt speed perhaps we'll never know. As long as the winners are using grooved axles I've decided not to chase them with straight axles. I think this "Flux-Capacitor" thing will make axles obsolete anyway.
Greg, Thanks again.

Cheers,
Bill

[TimInOhio]

K,

Now in my own experience, I have not really seen any real gains over grooved axles with graphite.

But I have seen gains with larger grooved axles with graphite.

meaning stock grooved axles, I have not. But others may have.

The larger grooved axles with graphite I have.

And yes, grooved axles with oil, is always better over non grooved.

Sporty

I apologize for the delay, Sporty, as I have been busy helping my pack kick off the Cub Scouting year - but thanks for the reply.

[TimInOhio]

Just my opinion... our cars have progressively gotten faster and faster each year - the cars that took first and second place in the adult division at the Mid America Pinewood Derby - As well as the cars that took first and second place in the qualified scout division and the fifth place car in the kids division - all were running on grooved axles with graphite. They are much faster than any cars that we have build using non-grooved axles. Many factors contribute to a fast car but an excellent axle is very important... I would be willing to say that the fastest cars in the thousands that I see every year... all are running grooved axles... and with oil a grooved axles is preferred, but more importantly the process in polishing the inner bore the outer hub, inner hub... we use a very unique process with graphite and burnish the graphite into legends or red rocket - after we use novus 2 & 3 - we also use a combination of several different types of graphite... it is messy job but when done right the wheels / axles combination are smoking fast. I should also mention the process in polishing the axle is very important... all of these processes are as important if not more so than if the axles has grooves or not.

Hope that helps a little
Greg

Thanks for the reply, Greg!

[TimInOhio]

So it appears that the general consensus is, that will all other things being equal, a grooved axle is the way to go when using oil. Now, is the grooved axle better than the non-grooved axle because the contact patch is so much smaller, or because the groove allows "extra" oil to cling to the axle there, or a combination of the two?

Thanks.

[TXDerbyDad]

I think a lot of people are quoting this test: http://www.stanpope.net/pwfrictn.htm

But I could swear that MaxV did an article on this in the last year comparing BSA Speed Axles, BSA Grooved Speed Axles, Oversize Super Speed Axes and Oversize Grooved Super Speed Axles. Found it!

http://www.maximum-velocity.com/pinewoo ... imes-v8i6/

Basically:
Large diameter axles are better overall than stock diameter axles, but...
Grooved large diameter axles with Krytox 100 oil were the same as non-grooved.
Grooved large diameter axles with graphite showed non-grooved had a slight advantage.

With regular diameter axles, grooved was superior for both oil and graphite over regular; significantly so for graphite.

[xanthrum]

Wheel Spin Test - Does Not Equate to fastest car and times... I can assure you that grooved axels are faster. I would encourage you to look at the grooved axels that are available at Derby Evolution - they are a fantastic product. Just to clarify why speed and fast times do not corelate to wheel spins... a lighter wheel will spin far less time than a heavier wheel but a lighter wheel will out perform a heavier wheel.

[Stan Pope]

Wheel Spin Test - Does Not Equate to fastest car and times... I can assure you that grooved axels are faster. I would encourage you to look at the grooved axels that are available at Derby Evolution - they are a fantastic product. Just to clarify why speed and fast times do not corelate to wheel spins... a lighter wheel will spin far less time than a heavier wheel but a lighter wheel will out perform a heavier wheel.

The reason you cite is why such tests should be done with wheels of comparable weight and rotational inertia! I'll leave detailing the less obvious reasons as a "discovery opportunity" for the time being, but think about "stiction vs. friction" and "bearing weight".

[xanthrum]

In plain english a properly prepped oil wheel will out perform a graphite prep all day long -- but an oil prepped wheel - will not spin anything like a properly prepped graphite wheel. I am trying to relay on the notion that a spin test does not equate to speed. There are so many other factors that are so much more critical to a cars performance - begining with proper set up - if the rules allow rail-riding - placement of weight - the prep process and all the attention to a million other contributor factors that make a car fast.... Additionally a grooved axle will outperform in application... maybe not in theory but in application.

[FatSebastian]

I think a lot of people are quoting this test: http://www.stanpope.net/pwfrictn.htm But I could swear that MaxV did an http://www.maximum-velocity.com/pinewoo ... imes-v8i6/article on this...

MaxV's graphical presentation of results is described as:

Each wheel-axle combination was given several "break-in" spins, and was then given ten timed spins. The high and low times were removed, and then the times were combined and averaged.

Some results may be within the bounds of experimental uncertainty; if so, it would not be possible to draw a conclusion as to which is better from the experiment. Rather than calculating averages with extreme values removed, it would have been better to have also provided standard deviation, etc. (like Bob Barga's results), to get a sense of the spread of the experimental outcomes and to supply a confidence interval (error bars) on the plotted values.

Also, while there is some question about the timing precision with such an experiment, hopefully this effect lessens with increasing trials.

Without providing details that might disrupt Stan's "discovery opportunity", I will at least admit that I think such cautious experimentation provides valuable insights.