small diameter axles vs larger?

[davet]

I understand that larger diameter axles are used in order to prevent the wheel wobbling on the axle and changing toe. If a car is running fast with stock, oblong shaped axles and stock wheels, isn't that faster than a larger (.091 or bigger) axle due to less wheel/axle contact?

[sporty]

No. Because a oblong axle. Stock size. Is still not filling the wheel bore gap. It's not resolving the gap.

It's still a .086 axle.


People use too and maybe still do. Make the wheel bore smaller.

Melted plastic. Ect. Several coats of wax.
it is harder. Much harder.

Because you have to have the tools to drill centerHole. And adding wax layers. After a few coats becomes up even .

So . That's why the larger size axle. It's easier to do.
but it's not the fastest. But because it's easier. More do it. Follow the leader.

Natural rules are a huge factore. Of what is allowed.

But a .086 axle is still that. Even if it's not true round.

[davet]

So running my stock, oblong axles as if an egg were laying on it's side helps prevent fore-aft toe changes but it's not a speed advantage having less wheel bore/axle contact? The stock axle is .091 (.092 for some) at the widest and .084 at the lowest. The weight of the car pushes the axle against the wheel so that gap is gone, leaving the .091 fore-aft just like an aftermarket .091 axle. I don't see how the round .091 is better. Why does filling the gap mean faster? What about .086 round axles? Wouldn't they be faster than .091 round axles?

[sporty]

A stock bsa axle is .086.

Are you using a awana axles ?

Or what axles are you using ?
My reply was based on stock be a scout axles. Which are .086.

Not .091 or .092.

Awana and other axles are.langer then stock be a axles.

Those larger size axles. Changes my reply. That information was left out of your initial post.

Also. Oil versus graphite would very my reply also.

Due to wax/ oil. liking a tighter fit. Where graphite a tighter fit can slow you.

[Speedster]

Hodges Hobby House. EDGEucation. "Do smaller axles really go faster?" Lecture 4. Dr. John Jobe, Author of the Big Green Book, "The Physics of the Pinewood Derby".

[davet]

Every stock BSA axle is oblong where the wheel rides. Have been for years. .091 on the high side and .084 on low side.

[sporty]

Every stock BSA axle is oblong where the wheel rides. Have been for years. .091 on the high side and .084 on low side.

All I can say. Because I have no interest to get into this as a debate.

I personally have not ever gotten a .091 reading on a stock bsa scout axle. Since I started checking them.

The largest I have ever found was .088.

As my highest number. Rotating and taking different readings.

I use to do many before and after readings to perfect my sanding / polishing to reduce as little as material as I could.


I just ran and checked 10 axles and still find the high reading of .086. .087. In the ten i checked and .084 to .085 on the small side.

My final stock bsa axle sizes . Typically after being polished was .083 to .084.

I run or try to run .094 to .0945 axles bores. After checking many wheels.

Anything is possible with axle size. But in the 200 plus axles I've checked. I have not found them in that size.

AWana axles I have and shape n race axles and in some Revell axles and a few other kits I bought and tinkered with Over the years.

Maybe derby work or max v. Or others like me who have checked a lot over the years can chime in.

See if they ever found stock BSA axles at .091.

I also do not measure on the raised crimp marks.


But to further answer the question.

On graphite. Stock axles. Stock wheels. Track and timer testing.

Rotating the axle slightly and super tuning the car. Each wheel.
this going back before we started rail riding. When we were rail running. Faster speed can be found. With super tuning.
it does take a track and timer to see and find the difference.

I always seen the difference from BSA axles not being very straight axles. As the bigger factor.
But I would not rule out the axle not being true round as being a factor in the super tuning improvement.

It was not a factor for us to focus on. Because after Sanding/ polishing. Most often .002 less was what we typically reduced.

As we got better and just took the raised numbs off. Got it to only taking .001 off. With picking through a pile of axles to find the best ones to work with.

[davet]

I don't really care either about a debate over axle size. I've got a toolbox full of .091 oblong axles. My main point is, should I use a smaller diameter axle or larger diameter axle with stock wheel bores.

[Laserman]

I don't really care either about a debate over axle size. I've got a toolbox full of .091 oblong axles. My main point is, should I use a smaller diameter axle or larger diameter axle with stock wheel bores.

Hi Davet,

Where did you get these .091" axles? Awana?

In theory, and in a perfect world... the smaller diameter wheel bore is the critical dimension. (less linear friction over the course of a run)

A smaller axle should not be helpful.

[Stan Pope]

Dave,

This from experimental results: Use the larger diameter axles. Lotsa observations, including Doc J.
(He said that the variation was within experimental error, but graphically, the trend was pretty clear and he indicated that belief!
Doc J didn't say this, but I believe it to be true: If your axle alignment is a bit off, the smaller axle allows the wheel to compensate with less axle lift. And the greater variance in Doc J's small axle tests could well have resulted from very slight deviations from perfectly aligned axles! (I didn't see any specs in his Lecture regarding alignment! )

This from my analysis: Orient the long axis of the oval shape as nearly horizontal as you can.
This is an analytic, not experimental, result based on what I think are pretty obvious factors. (1) A small dia axle will be more apt to engage bore smoothness issues than a larger axle. (2) The "attack angle" where the axle meets the bore is greater as the axle diameter decreases. This may just be a rehash of (1) ... I'm not sure. A greater attack angle would seem to approach being a "scraper" cutting away (albeit slowly) the bore lubrication.

Go fast, Dave!

[Speedster]

FWIW. Sporty stated his axles ended up .083 and .084 after sanding and polishing. An axle Made in China is .086 and .087 at the ring under the head. As every Auto Body Repairman knows, the tips of the fingers are very sensitive. That's why you see bodymen rubbing their hand over a Bondo repair. The fingers will find a Bondo line the eyes cannot see. Take a China axle and hold it between your thumb and fore finger where the wheel rides and turn it with your other hand. If there is any imperfection the tips of your fingers will tell you. Now do it with an axle Made in the U.S. If rules allow, take the China axle, polish it with Brasso and it's finished. Spend Lots of time on the wheel bores.

[davet]

I'll try to get a pic in today of my BSA axles. I've got ones already polished sitting at .090".

[sporty]

I'll try to get a pic in today of my BSA axles. I've got ones already polished sitting at .090".

I think we're all kind of wondering. If youre micrometer is reading wrong or if you got a hold of some axles that are what many scouts would like to have.

If you truly got some .091 reading. Bsa scout axles.

I'd like to get a set.

[davet]

This is the first axle I grabbed that's been rolling around in our toolbox. Here are my measurements from just behind the shallow axle groove we made. The dial was "zeroed out" prior to measuring. The caliper is accurate when checked against my pin gauges and drill bits. It's .091 where the wheel rides closer to the head. You can see by looking at my thumb in the first pic that I'm putting pressure on the caliper to make sure there was no slop. I turned the axle 90 degrees and got the smaller measurement. This is one we didn't use because we tapered the head a bit too much and the head got thin .
On the last pic you can see by the direction of the K-House groove that I'm measuring the .090 reading. These are stock axles right out of the box. This is our 4th year doing scouts and every axle we've ever bought has been this way. Some even smaller at the narrow spot but only a few times have we seen a .092 which was right under the head.