Plastic welding on LPR/MPR nose cones

[brewster_rockit]

Hello all,

I did a quick search and didn't see much on the forum regarding the topic of plastic welding. So I thought I'd share my ongoing experiment. The subject of my current project is the nose cone from an Estes Leviathan (also found in the Doorknob, Big Daddy, Pro Patriot and many other memorable kits.) At the end of 2019 the Leviathan went ballistic into the ground after the ejection charge didn't fire on an Aerotech G76. The nose cone was a few inches deep in the dirt; the rocket was mostly shattered between the nose cone shoulder and the coupler just ahead of the motor mount.

Most builders would opt to simply purchase a new nose cone after experiencing a "prang" of this nature, or perhaps 3D print a new cone. However, I saw this as an opportunity to practice my budding interest in welding plastic with what's essentially a soldering iron (the basic Harbor Freight plastic welder.) No guarantees that the completed cone will be very strong, but I'll be a better welder when the project is done.

If there's any interest, I'll try to get some pics up tomorrow!

 

[Hobie1dog]

I bought a Harbor Freight plastic welder and never did use it, good luck with it and definitely post up pictures

 

[brewster_rockit]

Some good results from the time I spent with the plastic welder today. First I'll explain my method for welding the broken plastic.

1) Sand away any paint on the surfaces to be welded (admittedly I did a rush job on this today.)

2) Work outside and wear a mask! The fumes are nasty.

3) If any parts are warped, try using a hair dryer on high to get them hot, and bend them back into shape before plastic welding.

4) I heated the welder up for five minutes before doing any welding.

5) Once the welder was hot, I held the two parts together and worked the welder perpendicularly to the crack I was trying to fix. If one side is higher, start on the high side! Move quickly, don't dwell in one location, and get the tip off the plastic if it looks like it's tacked down. You can get the welder tip fairly close to your fingers before the plastic becomes too hot to touch. Wear sturdy gloves just to be safe. Once the two parts are well-tacked together, I lightly run the welder tip along the crack to smooth the weld.

The Leviathan nose cone started looking like this:


Now it looks like this:





There are still some cracks that need to be filled (are Estes nose cones made from ABS? if so, I can get some ABS welding rod.) The surface isn't pretty, but plastic welds always get sanded down and smoothed out if you want them to look good! I might 3D print a coupler to go inside the nose cone shoulder and hold the two major pieces together; that'll give it strength on the inside. I'll even use ABS for the 3D print, maybe I can weld on the surface of the joined parts over the 3D printed coupler.

As a bonus, I found the tailcone from a BT-80 Estes V-2 that was destroyed by E9 CATO around 2015 and got some practice on it.

Before:



After:



Next steps? Try to sand the external welds smooth, get some ABS welding rod to try melting over the wider cracks, maybe 3D print some ABS parts to reinforce the cone from the inside!

 

[rocket_troy]

There are still some cracks that need to be filled (are Estes nose cones made from ABS? if so, I can get some ABS welding rod.)

I'm guessing they're polypropylene from reading this thread:

https://www.rocketryforum.com/threads/for-nose-cone-manufacturer-s-why-polypropylene.165863/
TP

 

[brewster_rockit]

I'm guessing they're polypropylene from reading this thread:

https://www.rocketryforum.com/threads/for-nose-cone-manufacturer-s-why-polypropylene.165863/
TP

It sounds logical that MPR/HPR cones would be made from polypropylene. However, I suspect the Estes blow-molded cones are made from polystyrene. This is based off Apogee Components stating their own blow-molded cones are made from styrene, plus my recollection of an Estes blow-molded cone that reacted to testors liquid cement (Which claims to also work on ABS and plexiglass in addition to Polystyrene.)

If the Estes cones are indeed polystyrene, I should be able to use plastic model sprues as welding sticks. I detect another experiment coming on!