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Old 10-10-2017, 10:21 PM
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TriHonu TriHonu is offline
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Default Oh what we do for storage...

This is a little different fabrication and welding story.

We had a hail storm that damaged the west sides of my two canvas top storage sheds (20x12x8.5 feet). [Pic 1] The company no longer makes this model. The competitor’s models are much lighter/cheaper and reviews on them are bad. Covers rarely last more than two winters.

I saw an ad on CraigsList that offered the material from a decommissioned inflatable sports dome for free. I spent a day and a half salvaging 3 pieces big enough to make replacement covers (finished size is 26 x 22). The first thing I found when I showed up was all the easy to get material was gone. The next thing I found out was that dome was lined, and the liner was welded every 4 ft. It had been raining so the material had water on top, and water between the layers. It also had netting secured to the inner surface.

I measured out and cut the first piece and quickly found out I was not man enough to move it by myself. So I got it flipped over and had to cut the inner liner out of it. It was all I could do to get the outer layer rolled up and loaded in my truck.

I went back the next day and got two more pieces and a few smaller (12x10) pieces.

About 15 years back I bought a roofing membrane welder at a construction auction. [Pic 2] I bought it for the 75’ 240v extension cord. Nobody, including myself knew what the machine was. It needed the guide handle and a silicone tire. I dug it out and cleaned it up and made sure it was working.

A service center on the other side of the city installed a new tire for $95. He also verified the material and provided the weld parameters (heat, air flow and travel speed) so I could fine tune the weld settings. [Pic 3] The machine blows hot air between the sheets melting the PVC coating and then the presser tire rolls over the melted zone fusing it together. [Pic 4-5] PVC welds around 650-700 degrees F with the welder traveling at about 7 feet per min on this 30mil material.

So I ran a few welds and performed the destruction tests to insure the welds were fused properly. Tearing the two sheets apart should separate the vinyl coating from the woven base sheet leaving the two vinyl layers fused together. The welds were not perfect, but damn good with the exception of a bubble here and there in the middle of the weld.
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Old 10-10-2017, 10:23 PM
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Next was drawing a pattern and getting the first one cut out. [Pic 6] Off to the drive way to clean it inside and out with a floor buffer. [Pic 7] I was told the material had to be clean, no dirt and no residue in the weld zone. Just before welding, the seams have to be rubbed down with Acetone and left to flash off.

I’ll tell you it takes far longer to clean a seam (both adjoining surfaces) than it does to preheat the welder (5 min) and weld 23 feet (about 3.5 minutes).

Each cover has 6 welds. Two sides get hems that each get 21 grommets. [Pic 8-9] The other two edges get a hem to make a 6 in wide pocket that a rope passes through. Then just above the grommets, a skirt is welded to the outside cover that hangs down to the ground. Each skirt is about 18” wide. I used an existing lap weld for the bottom edge. It is 4 layers thick, so I dug out my cobbler’s skiver/cutter to trim the skirts (about 200 feet). [Pic 10]
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Last edited by TriHonu; 10-10-2017 at 10:32 PM.
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Old 10-10-2017, 10:26 PM
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You can see the how well the acetone cleaned the outer-side. [Pic 11]. Again I used a bunch of weights to hold the sheets in position. [Pic 12] I slide them out of the way with my foot as I walk the welder down the seam.

Once the cover is welded up [Pic 12] the heavy work starts again. The cover I replaced is a lot lighter than this material. I can fold the old cover in to a 2’x3’ pile and tuck in under my arm and walk off. The new cover is much heavier. I had to stop and rest the legs twice dragging it about 300 feet across the yard. If that wasn’t bad enough, wrestling it up and over the frame was a 2 hour event. I tied three ropes to one edge and threw them over the frame. Keeping them snubbed off, I just kept working some slack up and keeping the ropes snubbed up.

I installed the first cover and made sure my pattern was correct and that it fit properly before I started over and made the second cover. [Pic 14]
All and all I have about 40 hours and $150 in the project to include getting the material, fixing the welder and making the covers.

With any luck, these should last at least 15-20 years. I got 14 years out of the cover on the first shed I purchased.

If you are wondering why I don’t just build, I’m in town and these temporary shelters are the only way to get around city ordinances. I had to get a special use permit approved to add the 24’x24’ shop addition on the garage. My garage/shop is almost the size of the house.
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Old 10-11-2017, 04:28 AM
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Talk about bringing back memories, I haven't used one of those welders for years! I used to work for a company that did rubber, plastic, tile, and metal roofing. Never got to work on a metal roof but did lots of rubber and plastic. Thats a high dollar tool right there.
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Old 10-12-2017, 01:20 PM
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Thats pretty cool. Material like that isn't cheap. Probably has a slightly higher R value too.
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  #6  
Old 10-12-2017, 09:42 PM
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Quote:
Originally Posted by gimpyrobb View Post
Talk about bringing back memories, I haven't used one of those welders for years! I used to work for a company that did rubber, plastic, tile, and metal roofing. Never got to work on a metal roof but did lots of rubber and plastic. Thats a high dollar tool right there.
The new model Leister is over $8000. You can get China models for around $1500. The new models are microprocessor controlled and can weld at much higher speeds.

My welder was about 4 years old when I bought it. I should have fixed the wheel and sold it. Now I would be lucky to get $750 for it. I got the welder and a 75 foot cord for $65. I had a thought of using the motor drive for a OA track torch but never even started that project.

When I asked the repair shop if it was worth fixing mine they offered to let me rent one of theirs. It was not worth the amount of drive-time/mileage to rent. By fixing mine, it allowed me to work on it when I had time.

I may still make one more cover. I have enough of the 30mil material and I have another spare frame. I had half a tree fall across one and bought a replacement. [Pic 15] Later I straightened and welded the damaged frame pieces and boxed it up.


Quote:
Originally Posted by Bender View Post
Thats pretty cool. Material like that isn't cheap. Probably has a slightly higher R value too.
Now that I have a working welder, I realize I should have salvaged more of that dome material. Even the smaller pieces could have been welded into larger tarps. I did salvage 9 pieces of the liner. It is 16mil thick and the pieces would weld together into a 35'x40', or I could use it for replacement end panels.

I don't know about R value, but the thing that I like is that is it's quite translucent. During the day it is like I have lights installed in there. The silver cover nearly blocked all light. It was really dark inside even with the door open.
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  #7  
Old 10-12-2017, 10:36 PM
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Danged good McGivering I'd say. Quite a money saver too. Work looks excellent too.
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Old 10-13-2017, 07:03 PM
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I never saw one of those seam welders until about 3 weeks ago. They are building a new rec center that we desperately need according to the powers that be. One of the crew was welding roof membrane seams with it. I was impressed how fast it was..
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Old 10-14-2017, 10:22 PM
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The one missing piece of information that I would like to have is a chart of welding parameters for different materials.

I have spent a lot of time searching online and have downloaded and read numerous membrane welder manuals looking for this information and none of them provided it. They all state to read the membrane manufacturers product data for the welding parameters.

The man at the service center looked at the sample piece of membrane that brought and he gave me the welding parameters. I don't know for sure, but I suspect that he just knew from experience.

I have some 16mil PVC liner material and have access to some 12mil billboard tarps that I would like to be able to weld. I'm going to call him Monday and will ask if he can provide the heat, speed and air flow settings.

I know that small changes in heat and speed in my sample welds made significant changes to the weld. The difference between scorch/burn and inadequate fusion was fairly narrow in my test welds. When you get it too hot it makes a mess. The settings the man gave me to start with were just about right on. He warned me to only change one parameter for each test weld.

I started a list of the different membranes and their melting temps. I would like to fill in start values for welding air temp and travel speed.

If I have to resort to experimenting, my plan is to set the air temp to the melting temp of the material and set the travel speed high and just keep slowing down until I get a decent weld. I know that the air temp he provided is higher than the melting temp, because when I slowed the travel speed too much it started scorching.
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Old 10-14-2017, 10:42 PM
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Wish I could help, but I have enough issues with metal welding sometimes.
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