OzVMX Forum
Clubroom => Tech Talk => Topic started by: crash n bern on March 31, 2008, 01:21:13 pm
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I'm doing up an ATK at the moment and I needed a rear guard/taillight extender. I found one in my stash but it had a piece out of the side with a split up to the light and one mounting arm was broken off. New ones are led, fit modern narrow guards and are about $70. So I walked around with it in my hand for a about half an hour scratching my head. I wished I put as much time into thinking about pressing out the steering stem before I started to press it the wrong way. But I'll leave that one for the "stupid things I've done" forum.
I have no idea how plastic welding is done, but figured it can't be too hard. So I grabbed an old 25 watt soldering iron with a stuffed tip and started stitch welding the crack together. Hey presto it worked well. So I got an old broken chain guard and cut all the missing pieces I needed and proceeded to weld them all into place. Then I melted some scrap pieces to fill all the low spots. Heated it all up with a heat gun and used a small cold chisel to trowel it all smooth. Then hit it with the sander, and bingo just like a bought one. Wow I can plastic weld better than I can steel weld. Next time I would probably use a 40 watt iron with a large tip as the 25 watt was a little low on heat. So now I'm on the hunt for broken plastics.
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spot on champ!
i've done a similar thing with the soldering iron mysef on the odd occasion.
the only thing i'd recommend along with all you've done is to make sure you've got good ventilation when doing this as the plastic fumes are crap! i usually sit my fan nearby on a low speed.
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I'm doing up an ATK at the moment and I needed a rear guard/taillight extender. I found one in my stash but it had a piece out of the side with a split up to the light and one mounting arm was broken off. New ones are led, fit modern narrow guards and are about $70. So I walked around with it in my hand for a about half an hour scratching my head. I wished I put as much time into thinking about pressing out the steering stem before I started to press it the wrong way. But I'll leave that one for the "stupid things I've done" forum.
I have no idea how plastic welding is done, but figured it can't be too hard. So I grabbed an old 25 watt soldering iron with a stuffed tip and started stitch welding the crack together. Hey presto it worked well. So I got an old broken chain guard and cut all the missing pieces I needed and proceeded to weld them all into place. Then I melted some scrap pieces to fill all the low spots. Heated it all up with a heat gun and used a small cold chisel to trowel it all smooth. Then hit it with the sander, and bingo just like a bought one. Wow I can plastic weld better than I can steel weld. Next time I would probably use a 40 watt iron with a large tip as the 25 watt was a little low on heat. So now I'm on the hunt for broken plastics.
hey crash n bern
you rekon this is repairable, as in welding?
(http://i354.photobucket.com/albums/r418/therealtoecutter/broeken%20side%20cover_zpsmvrmvkfh.jpg) (http://s354.photobucket.com/user/therealtoecutter/media/broeken%20side%20cover_zpsmvrmvkfh.jpg.html)
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Why not mic? If you can find some more of the same plastic to use as as filler.
Ive been stuffing around with various methods recently (heat gun, soldering gun with plastic welding tip etc) and I think I am making progress. Big issue is finding filler material that is identical to the original.
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As with metal welding, heat is the tool and the enemy.Plastic molecules change when heated and its properties are altered. You will always have a weak spot along the crack no matter what you do. Reinforcing the weld with a patch behind the crack will help but dont expect it to be a forever repair.Some plastics weld easier than others and some just wont weld.
I tried a few parts and i just wasnt happy with the need to redo the job after vibration and normal wear and tear took their toll so i welded and filled my broken plastics and used them as plugs for moulds. Fibreglass replicas are cheap and plentiful now.
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This book is pretty good
http://www.urethanesupply.com/book.php
http://www.amazon.com/How-Repair-Plastic-Bodywork-Money-Saving/dp/1884313809