If you haven't foung your auger yet I was fiddling with something simular a few years ago and found a place out of Nebraska that I ordered flighting from. It was suprisingly cheap. I had to give the ID of the tube it would be in and the size of the shaft I was to mount it on. Of course I ordered extra since you never know what you might want to build later!

That would be great. I was going to make it. Much better if I can buy it. Do you remember the name of the company?

My plan to make an auger was to cut circles the right diameter and put a 5/8" hole in the center and make a radial cut to the outside. Then I plan to make two dies out of aluminum with a 5/8" center hole for an alignment shaft. Put the metal circle between the dies and put it in the press to bend it to the pitch. Then weld them together and grind off the welds. Final assembly would be welding the flighting to the shaft.

Much happier if I can just buy something.

Chris

I tried that path and it didn't work well, I did some looking and I think this is the place. http://www.rfsaugerflighting.com/ Its been a few years though when I ordered it I think I had to call and it was probaly around 5$-10$ a length but don't quote me on that.

Bulk Augers

Thanks Guys, I will contact the place in Nebraska. The site shows they go down to 3". I was hoping for 2.5". It seems easy to find in 4" and up but a little more scarce in the smaller sizes. The pellet stove manufacturers seem to get small sizes but with a replacement part I am stuck with whatever length they have.

Thanks

Chris

You're very welcome, glad I could help.

Chris
Not sure if it work for your application but I've seen in hog feed systems a simple extended coil spring used inside a plastic pipe. Turn the spring the feed follows along the coils.
I used it once on a machine for filling styrofoam blocks with a peat moss mix. The blocks had tapered holes to grow tree seedlings in. Used a garage door spring that I stretched out, drove it with a dc gear head motor. You could adjust the feed to match the speed the blocks were moving through.
Lifted the material from a ground level hopper. On the feed system it pulled and lifted the pellets (which resembled wood pellets as I remember) from a big hopper bottom bin.

This idea sounds along the same lines as yours Greg.
Chicken farmers have automatic feeders for the chickens and they are done by auger. They are typically a flexible auger of some sort and usually not to big. Might be worth looking at.

All good leads. Thanks

I need good metering of the pellets but the spring still would probably work. The chicken feed augers look good but may be a problem to source in a small length. I do have minor concerns about heat affecting the spring steel used in both of these methods. One screwup with the burner and it may not be as springy.

I do think about burn back (fire traveling up the auger to the fuel supply). It would be faster with the centerless auger. I have to deal with it in a more positive manner anyway.

The chicken auger is designed to run in pvc pipe but it is unlikely to ever run enough in this application to wear out even in steel pipe. It would be straight (no bends to increase wear)

I will look at my lathe to see what the maximum pitch I can turn is. Still pursuing multiple possibilities.

Thanks for the suggestions.

Chris

I couldn't help but wonder if making some kind of rotary disk would be alot easier and cheaper than trying to make or buy an auger. I'm sure pellet stoves use the augers for a reason, probably more for better metering of variable settings than anything else, but I thought of those coin operated pellet feed dispensers you might see at a zoo. I'm sure they don't have augers in them, probably more along the lines of a rotary disk like you'd see in a gumball machine, and they seem to operate just fine. If you're going to operate on just 1 or 2 feed settings maybe this would be a better option. Just a thought (there I go, thinking again )

Keep thinking, it is a good activity.

I thought about a rotary disc for removing the ash. Also, considerong a little chain driven conveyor belt. (after a 2 hour burn I will have about a quarter pound of ash). I think the attraction of the auger is it doesn't waste a lot of space. I am replacing an oil burner in this case and therefore have some size and shape constraints. Ideally, I would like to get the burner part right inside the flash boiler (drawing coming soon). This is along the lines of fitting in a 6" cylinder. If I can't do it then the burn will be just outside and the flue gas will be blown inside the boiler. Most of the heat (80%) is generated by secondary combustion of the gas off the wood.

I have the lambda oxygen sensor and will be able to control the air to the burn pile and the post combustion air by varying the fan speeds. It makes sense to try to control the fuel delivery rate too. Then I can measure the water temperature in and out of the boiler therefore calculating the BTUs since I will know the water flow. And I can measure the air intake temperature and the flue gas temperature and therefore know how much heat is produced and how much I am capturing. Should be able to tune it to the best performance.


Chris

Maybe so, but it makes my head hurt and always scares my wife



Yes, it does make sense, you'll never know if you've got too many options, but very aware of too few.

Chris, You have another source for pellet stove parts. Check out Quadrafire. I know they have a tremendous ignitor. Only bad thing is that no matter what brand you would choose to buy from, new stuff for them are expensive. I would look at buying a used unit. That way you would have all the parts that you would need, including control boxes. One other thing, the reason pellet stoves get their efficiency, is the fact they use a combustion blower, This actually creates a negative pressure in the burn area. Also, it allows the pellets to be burnt more completely. My suggestion would be to marry the 2 units. Remove the convection section and associated blower and replace it with the coolant coiils and make sure it is sealed.

Thanks for the input. I'm afreaid very little for a conventional pellet stove will work in this application. There are lots of options for the ignitor $5.50 and up igniter on ebay . I will probably go with one with a hot air jet. The ceramic elements are in the $50 area but it will be safe from the fire and the ash because I can mount it a few inches away from the burn pile. I have to stay with my custom controller to incorporate the oxygen sensor which will monitor the burn. The fans will be controlled based on the temperature and the oxygen level in the flue gases. One fan will inject air into the burn pile from the bottom. The other fan will mix air into the wood gas coming off the burn. That is where 80% of the heat is. I have to keep the flue gas temperature below 1100. Above that temperature the particles become sticky and collect on the inside of the boiler.

I spent some time today working on the drawings for this. It's going slow as I am learning (using) a new cadd system and I'm not yet very familiar with it.


Chris

I was helping a neighbour re-rig the counterweights on his dock today and we were looking for pieces of chain near his shed. I stumbled over this piece of steel, which he kindly gave me.



I need a couple of augers to handle the pellets for this project and had looked at buying or building. This is easy. The piece is about 3" in diameter and 57" long with one bend. The bend can be fixed or cut out. I will need two augers, one longer one to pull from the bottom of the pellet hopper and a shorter one to feed the firebox. You generally put an interuption between the two as a fire break, to prevent a fire from traveling up the auger to the fuel supply.



It is very solid. I will clean it up with a wire wheel and then look at what I can find in high temperature low friction coatings.

I now have all the parts for the Lamba (Oxygen) sensor circuit, but haven't had time to work on it.

Chris

Chris, have you thought of a weighted door at the end of your feed screw to prevent follow back of the flame into your screw? You could have a cam that would bump the door to make sure it opens once every revolution of the screw.
If I have your design correct in my mind the screw would be inclined, so a finger (cam) on the end of the screws shaft could open the door to allow the pellets to escape as the leading edge of the flight turned past the opening.
Dan.

I've looked at a few ways to do it. The simplest is to have the feed from the first auger incline upwards and drop the pellets down a vertical tube into the second auger. That breaks the continuous path of pellets between the flame and the hopper. One design I looked at had a cam operated device in the vertical section to provide further isolation. Couldn't seee inside to see exactly what it was.

What you have suggested would work at the top of the verical section. It wouldn't need the cam as the pellets would force the door open. If I monitor the temperature in the vertical tube I could detect a fire. Reversing the auger in the event of high temperature would pull the pellets back and let the door close cutting off the fuel supply.

I like it. It's simple. Still there is the risk of one pellet getting caught and holding the door open.

I had been thinking along the lines of those rotating doors they use to keep heat in/out at department stores. Turn it sideways and put it in the vertical tube a bit like a water wheel. It would tranfer the pellets from the top of the tube to the bottom. Still the problem of a pellet getting stuck unless you only turn it when there are no pellets falling.

Maybe a trap door in the middle of the vertical tube (the tube could be square, maybe 2.5"). Stop the auger. Open the trap door with a solenoid or a cam. Pellets fall through, door closes and the auger starts again. Keep it clean inside so the pellets don't catch on any part of the open door.

I know it may seem like overkill but I want this thing to run safely and reliably.

Chris

Using the auger to push up the pellets is the way most all pellt stoves work, for the exact reason you stated. Is the 1100 degrees before or after the heat transfer section? Also as far as safety, most pellet stoves use snap switches inline to guard against overheat situations.

The 1100 degrees is just coming off the flame. If it is above that the particles get sticky and collect on the inside of the boiler. Most of the combustion will be inside the boiler. I will try to get some drawings done soon.

Chris