Derby Talk

So I hit a somewhat sobering milestone today ... for the first time I decided to teardown an old car to retrieve the tungsten cubes to reuse this year. Besides being emotionally tough (there was a lot of work in that car!), I couldn't believe how tough it was to get the cubes out. I basically had to chip away with a hammer and screwdriver, and break em apart with pliers etc.

Anyways, I now have a bunch of cubes with dried epoxy all over them. Whats the best way to get that off? I'm planning to just take a dremel with a grinder on them, but is there some other better way?

I cannot say becuase I have not yet tried to re-use tungsten and I dont think I plan to. My cubes are epoxied in there real, real well. When I build my next car and my sons builds his we will use aluminum tape to hold in the tungsten to the bottom of the car so it will be easy to remove.

I wonder if a good solvent would work good to break up and seperate the epoxy. Maybee give them a good soak in some nasty chemicals.

You could take a propane torch to it to burn off the epoxy. A quick Google search informed me that the melting point of tungsten is over 6000 degrees F. I would think that epoxy would burn off well before that.

I usually used a knife to scrape it off or pliers or flush cut wire cutters to pinch it off.

A little bit of effort, but has worked well enough for me over the years.

Sporty

The melting point of pure tungsten is over 6,000 degrees, but most tungsten sold for pinewood derby weight is "sintered", meaning it is pressed from powder, and is not totally pure. So, the melting point is much lower (not sure of the temperature).

Epoxy melts at a fairly low temperature, but it will still be sticky

Heat should be fine and that is what my plan is for next time. Just be sure to avoid the fumes. You will not get them hot enough to melt.

My first teardown consisted of two pair of pliers and a knife to scrape them clean.

Off topic, I know, but for weights formerly secured with either CA glue (Super Glue or Krazy Glue), or Bondo, a nice soak in acetone cleans 'em right up for us.

Thanks for the advice folks. Looks like there's no magical elixir here.

I had to go on a business trip, so I dropped the cubes in a jar of acetone while I'm away.

In general, I'm regretting doing this. The time I've spent and the destruction I've rendered is not worth saving $18 bucks.

LightninBoy wrote:Thanks for the advice folks. Looks like there's no magical elixir here.

I had to go on a business trip, so I dropped the cubes in a jar of acetone while I'm away.

In general, I'm regretting doing this. The time I've spent and the destruction I've rendered is not worth saving $18 bucks.

I don't think the acetone is going to work. It's the wrong solvent for epoxy. Heat is good at loosening epoxy. When I use the 1" rounds, I just take my soldering pencil and hold it against the tungsten until it heats up a little, then I scrape away with the xacto knife until the epoxy gets cold again, then I repeat. Since you are dealing with cubes, I would go to Home Depot or another big box hardware store and get a "heat lamp." This is one of those big, red lightbulbs that you see over top of food at buffets to keep it warm. Screw it into a workbench light and stick the tungsten/epoxy mix under it. Once the metal absorbs enough heat to get hot, start scraping off the epoxy. Repeat once the metal gets cool.

Just make sure you don't leave the heat lamp unattended. You don't want to burn down your house.

Paul

Doesnt really help in this situation, but we have been alternating cubes and a canopy. If you think you want to save some money and reuse, the 3.5oz canopy is awesome. We are not going to the professional races, but have not found a difference in using one or the other. Last year, my 2 sons made one of each and spent about the same amount of time (I helped the bear some, while the BS mainly did it on his own with my guidance. The younger boy used the canopy (4th time we have used it). Since the boy scout was not in cs anymore, he built it for a different race that my step mom entered them in for a charity race at their work.

Neither one lost a race (except against each other once) and it came down to a roll off. They both won in lane one (with the other in lane 2), and then tied on the 3rd race (down to the .001) and had to do a 4th run as they were that close.

I am sure that the cubes may help out if you are very serious, but for a simple to use (and reuse) I highly suggest the canopy.

LightninBoy wrote:Thanks for the advice folks. Looks like there's no magical elixir here.

I had to go on a business trip, so I dropped the cubes in a jar of acetone while I'm away.

In general, I'm regretting doing this. The time I've spent and the destruction I've rendered is not worth saving $18 bucks.

I would agree with you. In the past, we used tungsten powder from MaxV to fill our weight pockets when we made thicker wedge/modified wedge cars because it was effective, cheap and non-toxic, but last year we moved to tungsten cubes and canopies with the intention of reusing them. Because I have a lot of kids (6 boys will have gone through Cubs when we're done and I'll likely have grandkids by then), we intentionally designed our cars so that we could remove the tungsten easily. I use metal tape to secure the weight in the pocket and removed it when we were done. For the canopies, I used CA glue to glue it to the top, but used a slightly over-sized hole for the stem and only glued the underside surface of the canopy to the body. It was secure enough for our races, but came off with a razor blade shimmed in between the body and the underside of the canopy that I worked around the diameter of the canopy. A single-edged razor blade held in a pair of vice grips was used to scrape off the rest of the CA glue and it's ready for next race season.

Rukkian wrote:I am sure that the cubes may help out if you are very serious, but for a simple to use (and reuse) I highly suggest the canopy.

I would also agree with this, as our fastest car last season used a canopy. The only issue is that it's obvious when you remove it, and I save all of my boy's cars so they can have them when they're older. With the cubes, I can remove them and it makes no visual impact on the cars.

We use CA glue, to get the cubes back out, pound the body against something solid like metal. The shock will crack the glue and eventually the cubes will come out. I've only broken on car getting them out this way. One of my first attempts.

It might work with epoxy as well. To get it off the cubes I use acetone. Then scrap with a knife to get the tuff stuff off.

psycaz wrote:We use CA glue, to get the cubes back out, pound the body against something solid like metal. The shock will crack the glue and eventually the cubes will come out. I've only broken on car getting them out this way. One of my first attempts.

It might work with epoxy as well. To get it off the cubes I use acetone. Then scrap with a knife to get the tuff stuff off.

I used to work in composites (fiberglass, kevlar, carbon fiber), and two part epoxy is going to hold fast where CA glue fails due to the molecular bonding. If it's polyester resin, you might have a shot, but I'd still bet you'd break the wood body before you broke the resin. YMMV

TXDerbyDad wrote:

psycaz wrote:We use CA glue, to get the cubes back out, pound the body against something solid like metal. The shock will crack the glue and eventually the cubes will come out. I've only broken on car getting them out this way. One of my first attempts.

It might work with epoxy as well. To get it off the cubes I use acetone. Then scrap with a knife to get the tuff stuff off.

I used to work in composites (fiberglass, kevlar, carbon fiber), and two part epoxy is going to hold fast where CA glue fails due to the molecular bonding. If it's polyester resin, you might have a shot, but I'd still bet you'd break the wood body before you broke the resin. YMMV

I think your really hoping to break the bond to the wood, not so much the cubes themselves to start. Can't hurt to try. You're going to break the car apart anyways to get the cubes out.

Epoxy starts in a liquid state as it is mixed,
the substance temperature heats up until it starts to cool to harden..
You can remove it by getting it back to a liquid..or at least -gel -like state so that you can scrape it.
Heat from heat lamp or heat gun..and scraper while in gel like state.
or hitting it with a hammer and chiping the epoxy off while the epoxy is in a dry state.

Acetone will only soak into wooden surfaces when dilling with epoxy on plastic, marble, cement
vinyl, or metal, any chemical will interact with the top of the sufface..
But it does not penetrate down into the layers like it can with wood.
So FS, makes a good point if the tungsten is still epoxyed into the car.

The tungsten cubes were broken out of the car with the epoxy intact on the cubes.
I'd try freezing the epoxy with a spray refrigerant intell the epoxy..crystals and brakes off.