Plastic Hay Filter & Blower Redesign

I’ve been working on a replacement hay filter. To see the reason, check out the previous topic I posted, “Hay filter warning”.

My post at the time:

I’ve ordered two of these 15 gallon drums:

I plan to stack them up and weld them together. Adding fittings will be a challenge, but not impossible. Plastic welding is actually quite easy. Here’s the kit I got:

Plastic welding can be useful on other areas of the gasifier, I’m pretty sure. For instance, instead of taping over those wiring holes on the blowers, I plan to weld them shut, and redrill smaller holes if needed.

I’ve received the barrels. They drop shipped from the manufacturer, so there was a significant delay. Cost was $45 each with $20 shipping for the pair, total of $110. Plus a free pig hat.

Here’s how they look compared to the existing filter, and the plan is to stack them up and weld together, making one tall skinny drum. Size seems to be a nearly perfect match for what’s there now.

Next step was to cut down the barrel and weld up the two. I measured my hay filter height at 40", so took off 3" from the lower drum. I’ll have a spare lid.

Welding was easy and fun. It’s something like using a hot glue gun, at the same time as trying to spread stiff butter on bread. Once things warm up it behaves more like thick honey - very sticky and slow.

The plastic is LDPE, or Low Density Polyethylene. When it melts it has a paraffin type odor, not offensive. Still do it outside, plastic fumes are noxious.

The kit I bought came with some clear PE rods, so I used those for filler. The tip on the plastic welder has a feed tube for rods, so you can insert it and melt as it feeds onto the weld area. This is known as a speed welding tip.

It’s quite amazing how strong the welds are!

So, the next question is - will it hold water. I did test this out, and it was perfect. The plastic barrels were 3/16" thick, and I had plenty of material to fuse together. On thinner plastic like milk jugs I have had issues trying to seal them, but this worked no problem. Not a drop leaked. I inverted the container, the lid leaked a bit until I really tightened it down. This is an advantage of the bolt rings I think.

I did have a pinhole leak right from the factory though, down at the bottom. The mold halves were slightly misaligned on this drum, and they apparently grind the edges somewhat to remove the flash. In one spot that produced a thin place. No problem, I just melted it back together. Leak gone!

Video of the welding and water testing: Plastic Hay Filter Part 1 - YouTube

In response to Bill Schiller,

Do you mind showing us a picture of your plastic welder? Does it use heated air? That’s the kind I have but wondering if there is a better model out there.”

Mine is an airless welder, it was a full kit, $160 on Amazon. I think both air and airless are useful for different things, but I do like the ability to fuse parent materials without needing filler rod - I don’t think air welders can do that. The heat can be applied in a more focused area with the airless as well.

I’ve started using a heat gun (hair dryer on steroids) to pre-warm the plastic, it did a great job and the plastic stayed workable a bit longer. You can sort of use it to erase fine sanding marks too. It brings back the gloss in the plastic.

Thanks Chris.
I have the one with air and wasn’t satisfied with it’s performance. It’s quite possible I wasn’t doing it correctly. I am interested in finding an airless welder. Something like when they butt weld underground piping together.
Speaking of which, did you check out those types of companies for their cutoffs? It may be a cheaper alternative (possibly free) and readily available. You would also know that it can be welded air tight and various diameters.

Looking good Chris .Looking forward to seeing it installed on the truck .

Thanks Johnny! Will be finishing it very soon. Today I’m working on my hopper thermocouple instead.

Yes Bill I looked at the large plastic pipe, but had a couple issues - 1. I still need a lid. 2. large pipe is generally very heavy (and expensive to buy).

The kit I got isn’t cheap but I recommend it. The instructions are good, and you get some filler rods to start you out. Plus a very nice temperature controller and two tips.

Looking good Chris. Another cutting edge chapter in gasification. I looked at all the pictures, but didn’t see the pig hat ???

Just watched the video and am impressed. I like that much better than mine. Those barrels are coming together nicely. It’s a great way to reduce added weight. Great job

Hi Chris;
Yes, that plastic welding is awesome but you have to practice and get a feel for it. I have an air welder that hooks to my compressor and you can adjust the heat and air. At first I had trouble with it and the rods they shipped that were suppose to work according to them, did not. I found out that if I use a scrap of the original parent plastic it worked. Also I use the air to get it hot and soft and then I use the side of the nozzle tip to spread and fill and this worked awesome. It did not work well until I started using the side of the nozzle to spread. Keep up the fine work. Dan

Hey Bill; Heat and soften with hot air and use the side of the nozzle tip to spread and fill. I think you will find this works alot better than just air. Dan

Chris, I know we talked some on the phone the other day. What is the thickness of the plastic on those drums ?? Things perform different under pressure than under suction. I have learned the hard way. The drums are designed to store liquid or whatever but under positive pressure and not negative. Here is an example of one of my “boo boos”
Stuart Perkins who got us together in Kansas was riding with me when this garbage can collapsed. The lid sucked down and plugged off the inlet pipe and my engine collapsed it. I think you also bring your raw gas up to the top of the filter and then pull off the bottom so you can examine the soot build up on the top of the filter. Add some castlations to that pipe so if the plastic lid gets sucked down it will not close off the system … Maybe this is not a problem but I just thought I’d pipe in here. Also, keep an eye on the sides too as they may flex and weaken the welds or leak through there. Put a wrap of duct tape on the seam and aluminum tape over it to keep the UV off of it … Mike

Oh, Here is a picture of it after I finally took it off the truck. I probably drove it over 1000 miles while it was crushed
… M

what about static? if not grounded could it build up too much and go boom? or is the gas too wet to let that happen. i know a shop vac hose will build a huge static charge.
fill it with plastic balls and if it does hold alot of static would the soot stick to the balls? the balls would also keep it from collapsing if it was full to the top.
my first job they had large air scrubbers full of plastic balls with water spray bars washing them down they were at least 10’ by 10’ and they had 3 of them all made from CPVC they removed acid vapor from the air

You may be on to something. Electrostatic Precipitators use this concept for microfiltration with low pressure drop.

Solved the bulkhead issue. Curved bulkhead fittings are very hard to find. Flat ones leak on curved surfaces.

There is a thing called a Uni-Seal, designed for exactly this purpose. It’s basically a large rubber grommet which forms a seal against the curve and the pipe. Very popular with hyrdoponics folks, so I know they will hold water. It will also eliminate the LDPE to PVC transition problem. (can’t be welded).

I ordered these fittings from here, at $2.90 ea:

Nice find Chris , I think those will work perfectly with the plastic barrels .It may even be possible to use those with the metal ones ,maybe.

Hope that works for you, (and all of us). It should provide a little flex too. I didn’t see a pressure/vacuum rating.??

There is only ONE way to find out what works or doesn’t work ! Even when I blow something up I still have fun figuring out what happened … Mad Professor Mike … Keep on diggin … I think the weirdest comment I got was while Wayne was sleeping in my car in front of the courthouse in Green County, WI and the Register of Deeds thought I was Joking about Wayne driving up from Alabama on wood (875 miles) She alluded we were like Fred Flinstone with our feet out the bottom of our cars. Fortunately a friend of hers set up a CNC machine and was going to make GEK types and she looked at my pictures … Just share what you find out … M