Help with last minute paint/hub contact area problem.

[twojakes]

I'd be happy to hear thoughts on how to solve this (almost last minute) snafu. Our race is this Saturday. My son's car is painted with Krylon/Krylon clear coat.

After finishing with dry slide decals/clear coat, we pulled out the nails we had in place to keep paint out during the finishing process (we used the Pro Body Tool to drill the holes). When my son pulled out one of the back nails, it split the paint job and the paint on the lower half of the axle hole came off with the nail! I tried to gently sand with 1200 grit paper, and this only made things WORSE by roughing up the existing paint (I was hoping to smooth it).

Right now, the bottom half of the axle hole is exposed wood/primer and the top half is roughed up paint. I thought the 1200 grit would be gentle enough but boy was I wrong! I've never seen paint act like this, it's almost as if it's melting when I try to sand it at all - even with a fine grade paper.

Does anyone think taking it to wood with primer will cause the axle hole to swell? Any thoughts on how to fix this problem?

"Help Me Obi-Wan Kenobi, You're My Only Hope."
.

[kayjon]

The paint may be "gumming" up when you try to sand it because it is not completely dry, wet sanding may help and will help keep the heat down.
Without seeing what happened one thing you may be able to try is to repair the area with 5 minute epoxy.
What I would do is scuff the damaged area to give it some tooth and slightly install a polished nail or drill bit on the smooth side
Then mix a small amount of epoxy and pool it around the hole with a toothpick , it should flow out pretty smooth.
Then before the epoxy completely dry's, slowly give the axle /drill bit a twist and remove it leaving the epoxy on the side of your car.
Finally when the epoxy is fully cured I would then take my super fine sandpaper and polish the repaired area leaving the very slight mound of epoxy.
Lastly try you best to align the car so that the inner hub doesn't rub the body anyway

Good luck...Maybe try on a piece of scarp wood first

[twojakes]

Kayjon:

Thanks for your help. You were right that even though the Krylon can says "dries in 1 hour", and we were working on the car 12 hours after the last application, the paint was not dried. When I went back to it this morning, it took to sanding much better the gummyness was gone. Still not perfect, but no where near the level of roughness I initially saw.

Thanks! TJs

BTW - How could I align the car so one of the rear hubs stays off the paint but still goes straight? Holes are pre-drilled with a pro-body tool. Thanks again!

[Teeeman]

Last resort might be to chemically (solvent) remove the paint completely in the affected area (areas?) and polish/sand the wood.


Just for the problems you ran into, we were very careful not to get any paint on the virgin wood where we put our axle holes.


It is a topic of debate on here (I think) whether sanded/polished/graphited raw wood is a better surface than similarly prepared paint coatings.

We took the safe bet and stayed away from painting around the hole itself.


Hope it does clear up for you one way or another... this is a gut-wrencher from what I read... you'll get it right by the weekend, chin up!


-Terry


Meant to add the "dries in 1 hour" probably is for a low humidity high temp environment and a micro-layer of paint... ?
But so long as they aren't specific they can put it on the can and help sell the paint...

co-worker a few years ago claimed he had worked as an engineer with vacuum cleaner design a few years prior and one of the ways the makers would up the power on their advertisements was to submerge the electric motors in some form of cooling bath (he claimed liquid Nitrogen, but he was often full of wild info that forced me to take him only 1/2 serious...)...

[Pinewood Daddy]

Just for the problems you ran into, we were very careful not to get any paint on the virgin wood where we put our axle holes.

It is a topic of debate on here (I think) whether sanded/polished/graphited raw wood is a better surface than similarly prepared paint coatings.

We took the safe bet and stayed away from painting around the hole itself.

I applied green masking tape to mylar and punched out 1/4" diameter "dots". I peeled the tape off of the mylar and applied them concentric to the axle hole. The dots were removed a few minutes after painting. Then the sand/polish/graphite method was used.

[Mike Doyle]

Since our Pack requires the use of the original slots, we go a step further and tape off the slots and the body where the wheel hub makes contact. I like the 3M green masking tape for this, we cut it into 1/4" strips that cover the slot and wrap around the sides forming 1/4" squares at their ends.

One problem with some fast drying paints is the formation of a semi dry shell surrounding a gooey center. It's a battle between that ultimate glossy finish and getting the coats on too heavy.

[FRANKLIN WHALEY]

If you can't get it smooth enough before inserting the axles. Try some clear 3-M vinyl tape. Just a small piece big enough to cover the hub area and wrap a little under the bottom. You can apply lube directly to it and it's smooth as glass. Then just stick the axle right through.

[twojakes]

If you can't get it smooth enough before inserting the axles. Try some clear 3-M vinyl tape.

Franklin - thanks for responding. Do you think the tape could be considered a hub of some sort?

This years' car is really trying both of us. When my son was pulling out a front wheel to align it last night the axle hole began to crack! He wasn't being rough, but we heard a little crack, and both of us groaned. Using info from a recent thread on this problem, we glued and clamped the cracked hole, and it looked good this morning, but I gotta tell you, there's only so much you can take!

TJs.

[SpinDoctor]

If you can't get it smooth enough before inserting the axles. Try some clear 3-M vinyl tape. Just a small piece big enough to cover the hub area and wrap a little under the bottom. You can apply lube directly to it and it's smooth as glass. Then just stick the axle right through.

This wouldn't fly in our district.
I think it would violate the following rule,

4. Wheel bearings, washers, bushings or hubcaps are prohibited.

[2kids10horses]

I, too, would be worried that the tape might be considered a 'bearing or bushing' which are prohibited by our rules.

We taped off the area around the axle hole and left bare wood which we then rubbed generously with graphite.

We getting ready for council, and removed the wheels, and examined the body. Sure enough, there were signs that the wheel hubs had rubbed against the car body. Now, who knows when it happened... that is, did it happen when it was racing? Or when it was transported in the shoe box? When spinning by finger pull? Can't say.

But...

Since there was a little wear there, we decided to refresh the surfaces. We sanded off the existing graphite with 600 grit, then worked up with 800, then 1000, then 1500, then 2000 grit paper! We used the ends of the spent strips of axle polishing sandpaper that we had saved. Got that hub area really smooth!

The wear area didn't show that the graphite had worn off, but I'm sure it's smoother now than it was before.

2K10H

[Stephen's Dad]

This year Stephen tried something different. We mixed clear nail polish with moly/graphite & painted it onto the hub/body interface, then dusting more graphite on before it dries.

It was quite the messy operation.

We'll see how it works on Saturday but preliminary test results here at home are positive.

[mossk]

Last year and this year we coated the area with high gloss polyurethane then rubbed it with graphite. The problem is it takes a good 24 hours to dry but you get a hard durable surface. Maybe we could polish the areas the same we we do axles....

[HookedOnPine]

On your question of how to keep the wheel off the body, you could use Stans wax paper alignment technique and place shims under the axle to slightly raise the head of the axle. The wheels then want to ride up the axle to the head instead of toward the car body. Some people drill their holes in this fashion for the same reason. Less friction at the nail head than at the car body.

[Gameday]

This year Stephen tried something different. We mixed clear nail polish with moly/graphite & painted it onto the hub/body interface, then dusting more graphite on before it dries.

It was quite the messy operation.

We'll see how it works on Saturday but preliminary test results here at home are positive.

My son tried this, too, and I agree that it was very messy. After seeing the result I was convinced that it would only slow the car down, due to the lumpy consistency. We filed it off and ended up going with just bare wood coated with graphite.

[SpinDoctor]

I tested by spray PolyU on a pine block and dumping graphite on it.
I let it sit for 2 days. Shook off the loose stuff and it looked good. But when I rubbed it with my finger the stuff just rolled off. I was afraid that would just leave a residue which may be worse.

Now if I didn't touch it with my finder then the wheel would just touch a small area and the rest would be there and may slow flake off making it a self lubing wheel. What do you think

I go with bare wood and graphite, but I am currios if a nice hard gloss waxed finish would be better?