Post by fenwayhiggy on Feb 1, 2011 13:33:15 GMT -6
My son built an amazing car for our pack's pinewood and won, now he's qualified to go to the District, but it's an entirely different type of track. ( he averaged about 2.31 on a wooden 32 foot track )
We have a 32 foot wooden track, and a 48 foot aluminum is used for District.
His weight is centered about .85 of an inch for ward of the rear axel, which is in a stock location.
Last years car was slightly faster, averaging about 2.28, and was blown away at the district level, but had a similiar center of gravity/mass.
The runout on the 48 foot track seemed longer, which may have adversely effected his back heavy car, but I'm not sure.
Post by derbydominator on Feb 2, 2011 0:19:33 GMT -6
First of all, congratulations to you and your son for your pack win!!! Also, welcome to the forum.
I do not have any experience with a track longer than 42' so I cannot address the 48' issue. However, to help with your overall speed issue, can you give us some more information regarding your car?
3 wheels or 4 wheels touching Rail rider? axle prep method? wheel prep method? Standard or extended wheel base? Canted axles? wheel type (lightened or not)
Also what are your basic rules regarding these issues?
My initial feeling is that the same speed tips apply for a 48 ft. vs. a 40 or 42 ft. track used in the leagues. In that case, we will go as aggressive as 5/8" with a well aligned rail rider on a smooth track. 3/4" is a very common COM though and 7/8 (.875) is a very common suggestion for a non rail rider. If you are at .85 and getting blown away at districts, then you have other issues besides simple COM which brings up the above questions. What types of changes can you implement for districts?
Our District rules are pretty open to interpretation actually.
Four wheels have to be on the car, but there is nothing about all four touching the track, so I had three touching.
There is nothing in the rules regarding the bending of axels, it actually states that you can remove rough spots and burs as long as you retain the original dimensions of the axel.
Extended wheel bases are allowed, however the wheels cannot extend beyond the body of the car.
No modifications to the wheels are permitted unless there is a noticable imperfection on the wheels surface.
Before joining this forum I hadn' t even heard of 'rail riding' and everything I learned about Pinewood I figured out by losing in our first year.
The axels were prepped with by putting each in a dremel, and then using a small file to remove the burs near the head and those three small lines, then I wet sanded with 600 grit, and then used pumice to get them as polished as possible.
Wheels can't be modified, but I did pre graphite them, and spun each wheel with it's respective axel to work in the graphite.
No canted axels.
After reading through some posts, I'm pretty sure that the lack of 'alignment' didn't help me out much.
The only other prep I did to the car was setting the space between wheel and car with that plastic tool that has the measurements on it.
Post by rocketpine21 on Mar 27, 2011 18:19:41 GMT -6
Your axle prep needs to continue up to 2000 grit wet sand paper and then finish with micromesh or any other favorite finishing paper. THen polish with Mothers Billet Polish to make them shine like chrome!! Polish the bore of your wheels with a nice plastic polish. This should speed things right up, provided your alignment is good too! Good luck!
Net net, to increase your speed, you should also use Micro Gloss for the wheel bores and it will make it very smooth and eliminate rough spots. Use this on a qtip or pipe cleaner on the bore. Then use another thin/dry fine cloth to polish and clean the inside of your bore. You can also use a graphite burn method for the bores on the wheels as well when complete with micro gloss. Take a pipe cleaner and cover with hob e lube and generously apply to bore for about 20 seconds, then repeat. Once complete on Tires, can you lightly sand the outside letters depending upon what track your on. Polishing and burnishing the bore and lighltly sanding the wheels should help you pull some speed from your car.
Now you should have a glass like bore with grahphite burnished into the walls, no imperfections etc. Axles- use 400, 600, 800 grit, then move up to 1200, 1350 to aroud 1500/2000 or even 12,000 for the top sanders. (wet/sand grit of course then use an axle polish and many folks on this site can guide you on their best choices. Monkey dust, axle polishing kits, mothers, brassos, ec, ec. Some of these state they go as low as 1-2 Microns and even have particles of .05. For the polish use cloth strips covered in the polish on each axle for 10 seconds. If you want to go again you can, then complete this for all axles. Be sure to rub the cloth vigirously on the axle sections that will matter. Then soak these in 91% alcohol for 1/2 hour or so. Clean off axles fine glass cloth and dry and set aside. Make sure you dont overdue reducing axle diameter as if you increase bore size or reduce axle diameter, you will now have a sloppy area full of inefficiences and friction. Next step is to graphiting these all together. In an attempt to help your speed, these two items above may help if you have time prior to districts to get this all completed. This post is older so its most likely too late for considering my thoughts. But others here have provided you good advice no question!
Additionally, I agree that other factors may be coming into play here. If you say your getting lost in the pack a bit, would love to know what else you feel you may have left on the track? Would like to understand your CM, Weight used, did you move any back of block to front.
How was your Com?- seems .85 Weight? how much? Did you cant? doesn't appear that you can. Wheel spacing? Alignmnent- ? RR and passed skid test? Did you move slots or move .3 from back to front to allow for stabiliy? How was your body work = especially around wheel hubs. Did wheel run on axle heads?
We also have had to go from shorter to longer track and the keys to holding the speed- (considering that competitors had similar weight, CM, 3 wheeler, RR etc), is that axle/wheel prep, lube and alignment were key to holding the speed longer. Again, not sure how much time you and your son have prior to districts and after hearing some ideas to increase speed, you can perhaps attempt a couple here. Regardless, there may be some good advice you and your son can leverage for next years car. Good luck, but please let us know how it goes?
I would really like to understand a bit more about the questions I posed above as this will give a more complete understanding of your car.
Lastly, and FYI- my son will be using 3.75 oz tungsten at 1/2 CM on a 49 foot supertrack. Again the key to this longer track is axle/wheel prep, alignment and lubrication to carry the cars speed to the end. The longer the track the more it exposes what it not perfect in the car.