Boiling parts

[Effigy3]

So my son broke the left front lower A-arm racing last weekend. I ordered up replacement parts and decided to boil the new ones. I'm going to do this to the A-arms on my TRF 201 some time this month before I start racing when the track opens next month. Who knows how long the new A-arms have been sitting on a shelf and I know that my 201 has sat on the shelf for almost a year waiting for the track to open. There's a good chance that the plastic has dried out a bit! I broke the handle on the lid of our rice cooker last week. The new one arrived yesterday and I thought, "Wow, this thing could be perfect for boiling parts!"

It took a little while for the water to actually boil. Certainly longer than a pot on the stove but no more than 10 minutes.

The vegetable steaming tray was the perfect place to set the parts. I just ensured the water level was sufficient to cover the parts once placed in the tray.

I put the lid on and let them boil for 3 minutes.

I let them dry on the dish rack until they were room temperature. Now the nylon based plastic is as strong as possible. Hopefully my little man won't break them any time soon!

[Terz1]

I've never heard of this before. Sorry if it's common practice (I must have been under a rock). So boiling plastic somehow re-hydrates them and they are less prone to cracking. Is that right?

[waterbok]

Hmm tried that to remove tires from rims, but that didn't went well.

This approach is new to me too, probably depends on the kind of plastic used.

More details would be interesting.

[Frog Jumper]

I've never heard of this before. Sorry if it's common practice (I must have been under a rock). So boiling plastic somehow re-hydrates them and they are less prone to cracking. Is that right?

I've heard of boiling parts to help remove old dried up grease and dirt, but never to rejuvenate nylon??? I'd like to hear more about this!

Terry

[bjorklo]

I did read a place that it would help to boil the parts to get the re hydrated, but i can't remember where i read it, hmmm.

[Frog Jumper]

http://www.plasticstoday.com/articles/materials-analyst-part-85-fixing-brittle-nylon-product-water

[speedy_w_beans]

I boiled the front arms on my TRF801XT because it was common knowledge the stock arms were a little brittle and prone to cracking. This was before the Performance Package arms came available. During the injection molding process the plastic cools at different rates in the mold and there are some inherent stresses in the parts as a result. You can see this most readily in plastic chassis tubs where they have tweak or warp to them. The idea behind boiling parts is to soften the plastic slightly and relieve some of the inherent stress so the part can handle more mechanical loading. This works for some plastics better than others as different formulations have different glass transition temperatures.

I also used a heat gun on my TB04 chassis because it was pretty badly warped. I clamped it to a known flat surface with some C-clamps and small blocks of wood, then went back and forth over the chassis a while to get it to conform to the surface. It took most of the tweak out of it.

On the TRF201 one suggestion is to try the front arms from the DN01 Zahhak. These should be made of slightly softer and more resilient plastic. Usually the carbon-reinforced stuff is used for the racing kits because the parts are more rigid, leading to more consistent handling. The lower-level glass-reinforced parts won't perform the same, but they should flex a little more and take the abuse better. This isn't as weird as it might sound - guys running TB EVO 6 chassis are cracking the kit front uprights which are made of carbon-reinforced plastic. Some of them have found using softer uprights from a TA05 gives them better durability without sacrificing much performance.

Even on the DB01 chassis there are some high-traction arms available, and there is a special set of front high-traction arms that are a step softer so they don't fracture so easily.

Anyhow, boiling may or may not work depending on the plastic formulation. Beyond that, substituting parts that are softer can help with durability.

[markbt73]

There was one car (Royal Ripper I think) that recommended boiling the nylon parts before assembly. I imagine that a lot of people skipped that step, because Rippers had a reputation for being fragile...

I would be careful with some plastic parts, though; if they can't take the heat, you'll warp them. Probably best to test on a broken or worn-out part first.

[Effigy3]

Here's a good article on this practice. I only do it for suspension arms, bumpers, skid plates and shock towers but only if the parts are nylon based plastic.

[Effigy3]

http://www.plasticstoday.com/articles/materials-analyst-part-85-fixing-brittle-nylon-product-water

That is a GREAT article and more information about nylon plastic that I ever wanted to know. I appreciate the link Frog Jumper. Thank you.

[Frog Jumper]

That is a GREAT article and more information about nylon plastic that I ever wanted to know. I appreciate the link Frog Jumper. Thank you.

Googlez found it... I saw an article from an RC MB, but I figured "professionals" would know... And even after 2 years of college chemistry (albeit 20+ years ago), that doc is a hard read...

But here's the meat:

Processors and end users who use nylon have become very familiar with the effects that water absorption has on that material. In applications where high loads are generated, such as in snapfit assemblies, nylon that is still close to its dry-as-molded state may exhibit brittle failure, and we have learned that this failure mode can be mitigated by conditioning the parts to bring them up to their equilibrium moisture content. This frequently solves problems with the assembly process.

The moisture conditioning process takes many forms. Some simply pour a prescribed amount of water into molded parts contained in a moisture-proof package such as a polybag. Others prefer placing saturated paper towels into the package with the nylon parts and allowing the water to migrate out of the paper and into the nylon. Some go as far as boiling the parts. This not only increases the moisture uptake rate, but also ensures that the moisture is absorbed more uniformly throughout the wall of the part.

While rapid moisture conditioning is a legitimate method for improving the impact resistance of nylon products, there should be concerns with using it indiscriminately. A nylon product may be temporarily brittle while it comes to equilibrium with the atmosphere. But it may also be brittle because the material has been degraded during the molding process. In such situations, the brittle condition is not simply a temporary symptom of low moisture content, but rather is a permanent condition brought about by reduced molecular weight.

The problem is that this shortcoming can be covered up by pumping large amounts of moisture into the polymer. Under such conditions, the polymer becomes sufficiently flexible so that it no longer appears to be brittle. But a moisturizing process that is performed rapidly often introduces more moisture into the polymer than it can retain in the long term. If this happens, then when the excess moisture comes back out of the polymer, the brittle condition can return, usually after the part has gone into the application.

[Frog Jumper]

Also, this answers my question about why the vintage CRP parts that I dyed are more flexible after I boiled them in dye-water...

Terry

[Saito2]

Along with markbt73, I also remember Royal recommended boiling parts from both their Ripper (or Rip-off as we called it) and their later Crusher monster truck.