How to Polish Pinewood Axles
We will discuss our thoughts on Pinewood Derby Axles Polish Level (Sorry so long! Stick with it!)
Making BSA axles into speed axles is an art and process. You have to have very specialized tooling to do it correctly as well as efficiently. Below is our unique information which many will quickly debate, but rarely will they perform our same experiments. These results are based only about 1000 unique car builds over the years . We openly share our results and processes so that you can make the exact same axles without a single purchase from our sites. Putting you in the winner’s circle is our goal.
We will discuss our thoughts on Pinewood Derby Axles Polish Level Once you have decided that you are going to prep your own axles. Pick a process that will straighten your axles and remove the manufacturing defects.
Once you have done that, then you will need to decide what level of polish to bring your axles. My first suggestion is to check your rules. Your rules will determine what you axles will need to be polished even though it does not directly say so. Polish till you can’t polish anymore is a waste of time and resources.
The official BSA pinewood derby rules do not state any limitations on lubes. Meaning the sky is the limit. HOWEVER, most packs rules address what type of lube (99% of them say dry lube only) you can use. If you do not know, please stop here, read your rules, then return back when you have the answer. This ruling will determine your axle polish level.
Our knowledge, testing, and experiments have been designed around this 99% target group. Extensive resources have been invested in determining the best possible polish level for dry lube. And here are the two correlations that we have been able to attain.
For dry-lube users, we find axles that have been polished to what we believe is the perfect level for dry lube. 3000 grit. I know it sounds silly, but this is what we discovered. This is the easiest way to explain it. Take a pencil. Try to write on a metal surface that is super shiny. See how much (graphite) sticks to the metal. Now take the same pencil and write on a surface that is a little more coarse. See how the pencil (graphite) sticks. We started from the highest level of polish we offered (60,000 grit) and worked our way down. We found that 3000 grit is that level that offers maximum speed and maximum lube retention.
Although the higher grits “sound” faster, we find that after a few races, the deviation in time increases quickly and greatly. With that said, we are a firm believer that less work is better and this eliminates the need of extra time and costs in preparing your CHAMPION.
Process considerations…. We have found that wet sanding is far better than dry sanding. We start with 400 grit and work our way up to 600,800,1000 (1200,2000). Cleaning with water (we use a turkey baster and cotton strip)between each level of polish. This part is very important as you do not want any residue left over from the previous grit on your axle when polishing to the higher levels. If you fail to clean, you will still have 400 grit on your 2000 pass and you will not be able to obtain the proper polish.
Slight pressure is used during this process with continual motion of the sand paper along the length of the axle. Holding the sandpaper is one spot will cause peaks and valleys that will be hard to eliminate. The key here is to change the surface of the metal, taking great care in not eliminating the diameter of the axle. A smaller diameter will cause erratic wheel spin.
Once you have polished your axles, the next important process is anchoring or breaking in your dry lube. I can not stress the importance of this process for dry lube. Your car must build layers upon layers of dry lube that can shed off with each race. If you simply dust your wheels and axles, then you will not have sufficient amount of layers to get you to the winner’s circle. You will notice that you might win a race or two, but fall back quickly after that.
Basically explained. The coarse surface allows the graphite to stick or bond to the surface of the metal. From there, with proper break-in technique, layers of lube can be built on top of each other to ensure a friction-free surface. Check out the coefficient of friction of metal on plastic, then check out the coefficient of friction of graphite on graphite. See which is lower which means which is faster. Give yourself the best possible chance!
With this info— axle polish and lube break-in are a paired process. If you just plan on polishing and dusting (skipping a break in) with your dry lube, then the higher grit levels will be a better solution. We have not tested how far up to polish to with just dusting as we were trying to get a car as fast as we can with dry lubes.
The next process will be choosing which lube to pair with your axle polish level.
Things to consider when choosing your lube will be:
Particle Size (mesh–large flake, super fine)
Hardness (does it easily smear, or is there a gritty feeling left)
Purity (if its not 100%, what is the filler)
Why is this an important thing to understand?
Graphite such as Derby Dust® Dry Lube is an effective lubricant due to its unique blends of plate like structures known as lamellae. These lamellas lay parallel to the direction of motion built during the “break in” process. The unique characteristics of Derby Dust® Dry Lube allow the layers or lamellas to easily shear over each other resulting in low friction. It is the Trifecta of lubes. Proper particle size, no gritty feeling, easily smears, and sticks on both prepped axles and pinewood derby wheels.
For oil lubed cars
We have found that higher the grit, the faster the car. We first take an axles through the wet sands as described about, then we buff the axles to a mirror 100,000 grit optical polish using high speed buffing machines (7000 rpm) and oil based polish pastes. Apply a light load on axles during buffing as not to “burn” the paste into forming a wax. Each stage done by a separate buffing wheel to ensure there is no cross-contamination. Again cleaning the axle between each stage. In this case it requires an alcohol rinse and scratch free cloth.
The surface tension of oil allows it so adhere to the surface of the axle. And unlike graphite, there are no layers of oil that can be stacked on top of each other. Oil is a single layer lube. There is no break-in process for oil. Inner wheel hubs will need to be free from flaws and polished to mirror finish as well. See ASSET wheel line.
**Data collected on 35 foot Besttrack with custom TimerStopper timer that measures 4 points along the track. Track is leveled with digital protractor for accurate, repeatable results. Track has not moved position for over 7 seasons.