Pinewoodderby Physics did a huge experiment and scientifically proved that grooved axles were slower than solid axles. In theory and track testing, the higher psi between the grooved wheel/axle interface caused more drag than the solid axles lower psi interface setup. I can see the theory where a rotating object would roll faster with more ball bearings compared to fewer because of lower psi across the axle. While I know everyone is winning with grooved axles, has anyone tested the theory? Perhaps chanting with grooved axles combined have a synergistic effect. Your thoughts.
To Grove or Not To Groove
- Thread starter Falcon777
- Start date
The reason we can come to different conclusions is that "synergy" is not easily discovered. So I may have a set way of prepping my axles. If I test many different axles with my prep, I come to conclude a non-grooved axle is best. A different racer has a different axle & wheel prep and he finds a grooved works better. In today's races, the grooved is winning- BUT yes, with a different prep, the straight axle might come back in front. One theory is that we want close to perfection on the part that touches the bore and it is easier to get two smaller surfaces perfect than the entire length.
It might change dramatically with the magic bore process used. For example: we like to change the properties of the plastic with some way to harden the inside so we do not get so much "plastic deformation". I have tried unsuccessfully to bond a ceramic coating to the inside of the wheel, but who knows what can happen down the road?
It might change dramatically with the magic bore process used. For example: we like to change the properties of the plastic with some way to harden the inside so we do not get so much "plastic deformation". I have tried unsuccessfully to bond a ceramic coating to the inside of the wheel, but who knows what can happen down the road?
Excellent assessment! As a professional pilot both in the military and civil world, while a design looks good on paper, the synergies of design can combine where dynamic flutter takes over and planes can depart controlled flight in milliseconds. While modern computers today can predict much of this, it is still a crap shoot when any new design takes flight. We then must not discount straight axle design but see how they perform as technology evolves. So the next advance will be hardening the inner hub!
The way I see it is taking imperfection out of the equation. Less of the rotten wheel bores making contact and having a chance of the imperfections slowing it down. Might be way off but that is the redneck version.
I read that write up, and the flaw I saw was he just used the same method of prep no matter what component he changed.
I think the point of the grooves or any other different or "newer" type of prep is that it might allow you to change something else in conjunction
with it to get a speed increase. But alone, they might not get an increase. Hence, the term "synergy".
I'm by no means an expert and even I immediately noticed a flaw in his methodology while reading it.
I think the point of the grooves or any other different or "newer" type of prep is that it might allow you to change something else in conjunction
with it to get a speed increase. But alone, they might not get an increase. Hence, the term "synergy".
I'm by no means an expert and even I immediately noticed a flaw in his methodology while reading it.
DerbyDad4Hire said:
+1 I have changed my opinion on alot of things since I started league racing, but I have always said what John says above... less the redneck thing.
I am by far the least expert here but in my experiences at work as an industrial mechanic I find it out a lot the what looks good on paper does not always work in real life. I will continue to use the grooved axles. I hate those dang engineers who always over think things and make things more complicated than they need to be.
Some BSA packs do not allow the use of grooved axles in thier derbys. However, you can polish and even tap the wheel bore. Did anyone ever mill the inside of the wheel bore to mirror image having a grooved axle? I think that would actually be legal and the end result MAY duplicate the advantage of a grooved axle. Maybe. Oh boy, would need to test that one out!
I think there was a guy on Ebay selling wheels like that a couple years ago... You would have the same effect whether you groove the axle or the bore, but grooving the bore is much harder and I am sure there aren't very many people that could do it.
5k You think the groove holds extra lube in reserve? Having a hard time wrapping my head around the whole grooved thing. lol
I mean on a canted wheel with and axle of smaller dimension than the wheel bore size there is only two contact points of wheel to
axle, right?
I mean on a canted wheel with and axle of smaller dimension than the wheel bore size there is only two contact points of wheel to
axle, right?
Ok this is a good straight bore with an ungrooved axle at a 3 degree cant.. I think that in this situation an ungrooved or grooved axle will perform very well. The bore is perfectly straight with no imperfections. The axle rides all the way across the wheel bore evenly and the car is stable. (disregard the out of scale drawing and the wheel not really matching a BSA wheel)
Now this is a uneven wheel bore (way out of scale) and an ungrooved axle. The axle will ride on the highest 2 points as the wheel rotates and it may not be the same all the way around the bore of the wheel. If there is a high point in the center of the wheel you are really screwed because the wheel has a very short bore length that the wheel rides on and it will be very unstable.
This is an uneven bore but now with a grooved axle. The grooved axle will miss all the problems in the middle and only have to deal with the problems out at the ends of the bore. even if there are some problems out there you will have a much more stable wheel because the length of the bore is long.
Ok, now for reality.... Your bore won't be as bad as I have shown in the drawings, but the grooved axle may turn a substandard bore polish job into a fast car because you never touch 80% of the bore. So like John said you take a lot of the imperfections out of the equation. Now that being said I think there is a place for straight axles. Materials are different, lubes are different, everybody's wheel bores are polished different, etc..
I don't believe grooves hold extra lube and if it did I wouldn't use them... You don't want extra graphite or oil dropping down into the wheel bore during the race.
I don't believe grooves hold extra lube and if it did I wouldn't use them... You don't want extra graphite or oil dropping down into the wheel bore during the race.
Nice drawing, and I totally get what your saying. With that said, when I pick the car up of the table the rear wheels cant even more toward the car, more neg. cant, which would suggest that with the car weight off the wheel bore now rests on top of and in line with the axle. Conversly, with the car in the running position, on the track, with the weight applied, the inside bottom of the wheel bore is touching the bottom of the axle and the outside wheel bore is touching the top of the axle. Unlike your pic which shows the bottom of the axle paralleling the wheel bore perfectly. See what i'm sayin' ?
I see what you are saying and I have seen people say that before, but I don't believe that's how a car runs down the track/images/boards/smilies/smile.gif
Unless your axle head is tapered really, really, really extreme or if you canted your rears like 8 degrees instead of the standard cant around 3 degrees then your bore will always ride flat on the axle shaft. Your wheel won't ride up the tapered axle head unless it is flying through the air after being ejected from the track.
Unless your axle head is tapered really, really, really extreme or if you canted your rears like 8 degrees instead of the standard cant around 3 degrees then your bore will always ride flat on the axle shaft. Your wheel won't ride up the tapered axle head unless it is flying through the air after being ejected from the track.
