ADVrider

Go Back   ADVrider > Gear > The Garage
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-09-2010, 05:23 AM   #1
DaBit OP
Gnarly Adventurer
 
Joined: Nov 2008
Location: Netherlands
Oddometer: 345
Creating custom fuel tanks from HDPE sheet

I see people creating fuel tanks from shaped/welded aluminium sheet, steel sheet, carbon/glass/aramide composite, etc.

But I don't see people creating fuel tanks from HD polyethene sheet material.

So I wonder: why not? HDPE resists petrol including the ethanol, is easy to shape, not very expensive, a little flexible so it won't dent, and it's possible to weld it using an hot-air plastic welder. Sounds like a suitable material.

What's the catch?
DaBit is offline   Reply With Quote
Old 06-09-2010, 05:38 AM   #2
D.T.
One wheel wonder...
 
D.T.'s Avatar
 
Joined: Aug 2004
Location: Moneyapolis, MN
Oddometer: 8,820
Eh?

Try welding one up and let us know the results then.

How you going to "weld up" the gas cap and filler neck?
__________________
Quote:
Originally posted by burgerking So?
Holland is about the most expensive country in Europe when it comes to bikes and fuel..Stop whining and go riding It's just money and you only live once...
D.T. is online now   Reply With Quote
Old 06-09-2010, 05:46 AM   #3
Aussie Steve
Beastly Adventurer
 
Aussie Steve's Avatar
 
Joined: Apr 2007
Location: Maitland
Oddometer: 1,384
Quote:
Originally Posted by DaBit
it's possible to weld it using an hot-air plastic welder.
Might want to check on that, last I heard whilst it is possible the welds are weak and are not recommended, especially for fuel vessels.

If theres a new process to sucessfully weld HDPE please let us know.
Aussie Steve is offline   Reply With Quote
Old 06-09-2010, 06:08 AM   #4
DaBit OP
Gnarly Adventurer
 
Joined: Nov 2008
Location: Netherlands
Oddometer: 345
Quote:
Originally Posted by D.T.
Try welding one up and let us know the results then.
Don't have a project which could use a custom fuel tank at the moment. I just had some weird ideas past night in the time slot between going to bed and actually falling asleep.

Quote:
How you going to "weld up" the gas cap and filler neck?
Just bolt a metal one in with a gasket or sealant between metal and plastic?
Or use the gas cap/filler neck from a junk PE tank. Old XR600 tanks can be found for little money, for example.

Quote:
Originally Posted by Aussie Steve
Might want to check on that, last I heard whilst it is possible the welds are weak and are not recommended, especially for fuel vessels.
OK, that might be the reason. I didn't expect those welds to be much weaker than the parent material.

A plumber friend of mine used to do a lot of PE pipe construction where they weld the pipe ends together. No problems with joint integrity according to him.

Quote:
If theres a new process to sucessfully weld HDPE please let us know.
No new process that I know of. I have seen someone doing it with a hot air gun with special nozzle and decent temperature control. The trick was to slightly melt the base material and push the filler rod in with quite a bit of force. Personally I haven't welded a single inch of plastic so I can't comment from personal experience.
DaBit is offline   Reply With Quote
Old 06-09-2010, 04:39 PM   #5
P B G
Beastly Adventurer
 
Joined: Mar 2008
Location: Greater Chicago
Oddometer: 9,935
Won't HDPE thermoform and stick to itself?

I'll check the chart at work tomorrow, I do orthotics and prosthetics, so everything we do is pulling plastic.

If you used a plug that you could disolve, you wouldn't weld the seams together, you'd dissolve the plug.
P B G is offline   Reply With Quote
Old 06-09-2010, 04:43 PM   #6
GSWayne
Old Guy nOOb
 
GSWayne's Avatar
 
Joined: Mar 2005
Location: Santa Barbara
Oddometer: 2,900
An advantage that the molded PE tanks have over welded ones is the strength from curved surfaces. By welding one from flat pieces it will not be as rigid, especially if you have any large flat surfaces that will tend to "oil can".

It might take a bit of practice welding plastic before you want to make a tank holding gallons of flammable liquid between your legs
__________________
It isn't the conditions its the decisions

Don't bring a motorcycle to a car fight
GSWayne is offline   Reply With Quote
Old 06-10-2010, 12:27 AM   #7
DaBit OP
Gnarly Adventurer
 
Joined: Nov 2008
Location: Netherlands
Oddometer: 345
Quote:
Originally Posted by P B G
Won't HDPE thermoform and stick to itself?
Not sure what you mean by 'stick to itself', but yes, HDPE is a thermoplastic. It can be formed with heat, and heat is also used to 'melt' parts together. I assume one would need to heat it to at least a buttery consistency before fusion occurs.

Quote:
If you used a plug that you could disolve, you wouldn't weld the seams together, you'd dissolve the plug.
That plug should be dissolvable, and resistant to the heat involved in molding the HDPE. An aramide/glass composite would be easier when going that route, I suppose. Except for the ethanol-related issues.

Quote:
Originally Posted by GSWayne
An advantage that the molded PE tanks have over welded ones is the strength from curved surfaces. By welding one from flat pieces it will not be as rigid
True, but a tank made of sheet metal or any other material with large flat surfaces suffers from the same issue. This is easily solved by either shaping the HDPE sheet or adding reinforcements.

Quote:
It might take a bit of practice welding plastic before you want to make a tank holding gallons of flammable liquid between your legs
Again, no difference between HDPE and any other construction method :)
DaBit is offline   Reply With Quote
Old 06-10-2010, 03:59 PM   #8
P B G
Beastly Adventurer
 
Joined: Mar 2008
Location: Greater Chicago
Oddometer: 9,935
Quote:
Originally Posted by DaBit
Not sure what you mean by 'stick to itself', but yes, HDPE is a thermoplastic. It can be formed with heat, and heat is also used to 'melt' parts together. I assume one would need to heat it to at least a buttery consistency before fusion occurs.
Simply that if you take two hot peices of plastic, and stick them together they fuse.

It leaves a seam, but that seam can be ground flat, like a weld.

So if you had a plug you could dissolve, perhaps foam, you could vacuum the tank over a positive, using the tank bung as the vac. port perhaps? Or you could use the future location of a tank drain. although perhaps some variety of blow molding into a negative would be better, as the texture of the mold would remain on the surface.
P B G is offline   Reply With Quote
Old 06-11-2010, 06:46 AM   #9
Wreckchecker
Ungeneer to broked stuff.
 
Joined: Dec 2008
Location: Damascus, MD
Oddometer: 2,139
Not only could be done, but has been many times for the desert sleds. It's custom and will cost $$$.

Typically, the sheet is heated (about 385f) and pulled down over a pre-heated plug, baffles are added internally for support and slosh prevention, then the bottom is welded in place.

Plastic welders will work, but plastic as a material does not weld at all like metal. Especially if you want a seam that is at least as strong as the parent material that it is joining. The trick for a good plastic weld is that you actually have to stir the plastic together.

Watching a guy who is a good plastic welder is artwork in motion!

For the welding itself, you might check out smaller plastic firms that make chemical storage tanks for lawn care, farm, and chemical companies.

Don't forget to test it with a 4-5 psi positive pressure test. Do it with the tank filled with water unless you like shrapnel wounds!

Sounds simple enough, right?
Wreckchecker is offline   Reply With Quote
Old 06-20-2010, 02:08 PM   #10
Chronus24
Space cowboy
 
Chronus24's Avatar
 
Joined: Jul 2006
Location: Florida
Oddometer: 137
HDPE is really hard to weld. The strongest joint you can make with it is with a epoxy called poly-weld. That is specially made for HDPE and you need to use a torch on the edges before you weld to prepare the plastic to "accept" the epoxy.

I have also been looking into making a tank out of HDPE. I have been thinking about thermoforming shells and then bonding them to a flat inner plate.

Do a youtube search for welding or bonding HDPE and you'll see that its really tough to bond. Probably for the same chemistry that keeps gasoline from breaking it down, most glues and bonding techniques don't work.

I have also thought about making a pinched seam with a sealer and numerous rivets. I think blowmolding a single piece is ultimately the best bet, the mold would be difficult but that would be all you'd really need to make.
__________________
"Death is a very dull, dreary affair, and my advice to you is to have nothing whatsoever to do with it."
-W. Somerset Maugham

"Here we are, trapped in the amber of the moment. There is no why."
-Kurt Vonnegut
Chronus24 is offline   Reply With Quote
Old 10-27-2013, 08:48 PM   #11
Tylenol
Gnarly Adventurer
 
Tylenol's Avatar
 
Joined: Aug 2013
Location: Bridgetown Nova Scotia
Oddometer: 105
And good source of HDPE are those cutting Boards you can get from the hard ware store if you don't have a place to get it by the sheet/roll or what not.
I have been thinking about this as well, I have a steel tank but it is really rusty and the fuel is starting to turn brown so I was thinking of using the metal tank as a mold and with a heat gun maybe heat mold a few cutting Boards to the tank shape and seal the seams, or weld them some how.

Has anyone here molded HDPE to a pre-existing form?
__________________
"We don't stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw
Tylenol is offline   Reply With Quote
Old 10-28-2013, 01:45 AM   #12
DaBit OP
Gnarly Adventurer
 
Joined: Nov 2008
Location: Netherlands
Oddometer: 345
I did. Try to heat it even, and it will eventually almost drape itself around the form. It does shrink and deform during cooldown though.

Also, I found that welding HDPE using hot air and the 'pendulum-technique' is fairly easy. Slighly harder to weld than polycarbonate, but not much.

I did not yet create a fuel tank out of it yet.
DaBit is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 05:40 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014