Question about reshaping plastic

[YellowJacket!]

I'm going to get things painted soon and have a spare front fender to put on my bike.  The problem is that it has a slight twist in it from front to rear.  Its not very noticible but its enough to rub on my tire.  If I put it on a flat surface, the twist is about 1/3 of an inch.

What is the best way to untwist it and straighten it out?

I tried taping it tightly to a flat board for a couple months.  I even put a shim under the opposite side to help it along.  While somewhat improved, it still rubs.

Any suggestions?

Thanks,

David

[ps2/bikevision]

dave you where on the right track with staping it down. but you missed one thing. plastic doesent like to bend to a new shape without heat. its like steaming a piece of wood before you bend it. get a heat gun, or the wifes blow dryer. heat it up a little at a time. dont melt it just enough that it will feel a little soft. then once its in the shape you want you have to let it cool slow or it will crack.

[Sable]

Did you try to put some heat to it? I know that sometimes, a little heat (like holding under hot water from a faucet may do the trick), or if you have a heat gun (wife's hair dryer) may work too. Just be careful, don't want to overheat it.
I have never tried this, but I used the hot water from the sink to bend a PVC pipe when I installed a garbage disposer a few months ago.

~John

[YellowJacket!]

Thanks guys for the tip.  I figured thats what I'd have to do but wanted to be absolutely sure.  Now, I have to figure out a heat gun source.  After toasting my wifes hair dryer while drying the tank. I have been banned from her side of the vanity.  :o :o :o :o

David

[xdaboatmanx]

Boil it.   hot water will soften plastic.  find a huge pot for it and boil away.  watch it the whole time or it will shape into the pot. once it is soft and flexy, hold it by hand till it looks right. next just run it under water to cool it into place.
   raw heat will make it brittle and it will crack in time. boiling will not cook out the oil in the plastic.   it worked out good on side cover on mine. it was twisted so bad that the bottom pin didnt hit the bike.
Boat

[kiawrench]

dave tn -- i had same problem on my front when i got this bike--
  i used two stage heat ,, i mounted the fender, and used tape (nylon filament type packing tape and some small rags to lock the fender into correct position.

then i applied a regular bath towel to the fender. i wet the towel with boiling water in five minute intervals for about a half hour, then removed towel and used a wagner heat gun to tweak the support arms just a bit .
allow it to sit for about an hour to cool, then you can remove the rags and tape, fender should be fixed .

heat guns and hair driers are great, we used them in the dealership to remove small scratches that some mechanics just cant miss leaving when doing interior work
ust heat genlty, allow to cool the scratch retracts into the surrounding area and the "grain " still shows. then just wipe down with silicone spray to revive the shine .

[supervision]

  Maybe you could secure it to a straight surface then pour a tea pot of hot water over it, let it cool and check the results.  Have you taken the metal mount piece away from it too see if it is bent?  ( I don't know how easy that is )

[Coil Coyle]

Thanks guys for the tip.  I figured thats what I'd have to do but wanted to be absolutely sure.  Now, I have to figure out a heat gun source.  After toasting my wifes hair dryer while drying the tank. I have been banned from her side of the vanity.  :o :o :o :o

David

Dave, Most likely you melted a heat fuse when you restricted the airfloe from her dryer. It is in the barrel near the outlet of the air and looks like a resistor. An Electronics parts house will have one for less than a buck.

$0.02
;)
Coil

[kiawrench]

dave ---
     go to Lucky, have him get you a wagner paint stripper gun (19-25 dollars)- it has two heat settings, and is a lot cheaper than a regular "snap -on " heat gun for automotive use. and it will last a lot longer than snap on too!

   you could let wife use it for her hair, but i bet she will ban you from the house for life-- it will set her hair on fire .

if lucky's store doesnt have those, you can get them at walmart

[YellowJacket!]

dave ---
     go to Lucky, have him get you a wagner paint stripper gun (19-25 dollars)- it has two heat settings, and is a lot cheaper than a regular "snap -on " heat gun for automotive use. and it will last a lot longer than snap on too!

   you could let wife use it for her hair, but i bet she will ban you from the house for life-- it will set her hair on fire .

if lucky's store doesnt have those, you can get them at walmart

Hey Lucky, Got any of those?

SV, I checked the metal piece and it looked ok.  Its rivited into palce and I'm too afraid of damaging the fender to remove it.
If I can straighten out this one, its actually on better shape overall than the one on my bike.

David

Thanks everyone for the ideas.

[Lucky]

yup, we got 'em (minus my employee discount)  ;D

http://www.acehardware.com/product/index.jsp?productId=1310859&cp=2568447.2625445.1260562&sr=1

[h2olawyer]

I found a dual temp heat gun @ Harbor Freight for around $20.  Came with lots of various scraping and air diverting tools / attachments.  Works well - but it is made in China . . .

H₂O

[MotorPlow]

Thanks guys for the tip.  I figured thats what I'd have to do but wanted to be absolutely sure.  Now, I have to figure out a heat gun source.  After toasting my wifes hair dryer while drying the tank. I have been banned from her side of the vanity.  :o :o :o :o

David

HMMM, Burgers like heat too.... Burgers cook on a grill... You can also cook on a stove... the stove has an oven.... The fender will fit in the oven... What temp to set it too?...

[YellowJacket!]

HMMMM, burgers cook on grill, David gets distracted by 2 more Visions in driveway, burgers get burned.  Vicki cooks new burgers.
Fender cooks on grill to get reshaped, David gets distracted (new girl next door sunbathing), fender catches fire and melts, Vicki laughs.   ;D

David

[reckon]

Boil it.   hot water will soften plastic.  find a huge pot for it and boil away.  watch it the whole time or it will shape into the pot. once it is soft and flexy, hold it by hand till it looks right. next just run it under water to cool it into place.
   raw heat will make it brittle and it will crack in time. boiling will not cook out the oil in the plastic.   it worked out good on side cover on mine. it was twisted so bad that the bottom pin didnt hit the bike.
Boat

how long for an al dente fender?    do you salt the water first?   :D

the hair dryer is a safer bet, all you need to do is get it to about 140-150 degrees and it will take whatever shape you twist it to,....it'll need about a full minute to cool enough to hold the set,...let it cool naturally, DO NOT FORCE COOL IT WITH ANYTHING, or it can re-warp to the original set, or worse

a third of an inch isn't much so no need to overheat it

[MotorPlow]

HMMMM, burgers cook on grill, David gets distracted by 2 more Visions in driveway, burgers get burned.  Vicki cooks new burgers.
Fender cooks on grill to get reshaped, David gets distracted (new girl next door sunbathing), fender catches fire and melts, Vicki laughs.   ;D

David

LMAO!