I know it’s early on the calendar but my focus is starting to shift back to my heating hobby. After two years of experimenting I have a proven performer with both the mechanical unit and the software I used last winter. I could change nothing and go through the winter fairly smoothly but there is always room for more improvement. So this is my plan: 1) Build a new unit very similar to the proven unit I have been using but with greater feed range capability to allow the unit to feed wood chips as well as pellets. By building a complete new unit I can always roll up the proven unit after the experiment is over and the data collected and resume heating without a hiccup. 2) Make slight modifications to the boiler to allow a larger interface plate between the feed unit and the boiler. This will allow a greater range of experimentation with burner designs. 3) Continue making small experimental changes to the working pellet unit such as a vibrator for ash removal, different burner designs, different draft designs. 4) Continue to make changes and improvements to the software. To start I would like three modes of operation. Continuous, run for some amount of time, and run until a set time. I changed the software to run to a set time by calendar date last spring but it was built into the software by date not menu or button choice. I would like to have the option of running for a few hours for both experimentation and also to occasionally heat hot water and be able to choose these options by menu. This fall I am sure I would like the unit to be able to take the chill off and then shut down. 5) Build a chip dryer. This is going to get to be a priority , I know the days are getting a little shorter and it is amazing how much less solar there is in the fall. Time to giddy up on that one.
I know I have to prioritize the work, and work as time and cash flow allows. But I think the first step will be to make a new interface plate and boiler opening. This will allow standardization for the next design and this work can be done while there is no particular need for heat. I went dumpster diving the other day and got a great new electrical box, so I guess I can get going on the that part of the new burner feed. I like free stuff. I may hit that dumpster again soon.
In the mean time it is still summer and there is still sailing weather.
At this point the boiler has been working for a day and based on last years experience I see no reason why I would need to shut down for a week. Yesterday we brought two tons of pellets into the shop knowing snow and rain mix was in the forecast. Yesterday was a pleasant 40°F day with full sunshine a great day to move a little fuel. I believe we are on a two bag a day pace so with luck I won’t have to worry about moving pellets again until nearly February. We have chairs set up by the boiler and it is a pleasant place to sit and talk in lieu of sitting in front of a woodstove.
So..what’s next on the list. 1) Software improvements, to be able to adapt to pellets or chips will take a more dynamic software approach. The software should be able to adapt automatically to varying energy densities. 2) Faster and easier maintenance. More over center latches to be able to easily take apart the chimney for cleaning and a removable top to the boiler to easily clean the tank tubes. 3) Testing with various materials, chips being at the top of the list. 4) Building a chip dryer. 5) Adding more sensors, I am definitely going to add a fire eye to confirm fire. I would like to monitor the temperature of the feed motor and the fan motor. It would be helpful to add a relay for the fan motor so that is controlled by the Arduino. 6) I have tried the self start but it is not in the software yet, that would be a great leap forward especially for March and April when daytime heat is often not required but nighttime heat and hot water are needed. Automatic starting would be great and would save a lot of fuel. 7) Improving the CNC Plasma cutter, there is still some chatter in the Y axis and if I can fix that, it would be great and would probably speed the CNC up significantly cutting down on the dross or slag produced when it is cutting. Cutting down on the slag is a major priority since it is time consuming to grind this off and I am sure part of the development will include trying different burner designs. 8) Taking a Design of Experiments statistical approach to the burner design to optimize for efficiency. I gave myself a pretty good list back in September and I have whittled it down to completion so I know it is all possible and fun, I just need to get started. Tomorrow probably, today I am just going to sit by the fire and enjoy a Sunday.
I often have to cut multiple parts, so when I do, I take the opportunity to experiment a bit. In this series of cuts I changed the amperage of the Plasma cutter, a Hypertherm 45. Hypertherm plasma cutters are American made, designed and built, only about a 45 minute drive away from me. I still haven’t gotten my free T shirt for buying and registering the machine but I guess that’s another story… anyway, amazingly enough there really is not a lot of difference in the dross or slag between the three different amp settings I tried. I’ll keep experimenting to try to optimize the cut quality and speed of the CNC machine, plasma cutter combination.
The auger pipe connects the burn plate which attaches to the boiler and forms the interface between the auger feed and the boiler/burner units. I took a piece of 6″ pipe and welded it to the boiler plate and this attaches the plate to the auger feed via screws that tighten. With this assembly I can detach the auger and hopper and test a different burner simply by loosening 6 screws. Modular design for ease of design changes and maintenance.
I attached the hopper plate first because this determines the wheel height required. I slotted the holes in the saddle plates so that there is about 3/8″, or about a centimeter of adjustment up or down adjustment. Then after careful alignment I assembled the entire assembly with clamps and threaded rods. I did cut and weld in some cross pieces with gussets
This will make maintenance of the boiler, ash removal, scraping of the burner holes, boiler tube cleaning very easy by simply rolling the auger/hopper assembly out of the way.
In this step I mount the auger drive motor, it has a built in right angle drive and speed reducer which adds torque. The motor comes complete ready for wiring and mounting using four screws. Again I drew up the parts in SketchUp and then cut them out on the CNC plasma cutter, it was almost too easy. The further I get down this path the more I take advantage of the CNC’s capabilities. Note the rounded corners, I also added an extra hole on top of the motor mount plate to make adding a wire routing clip easier in the future. I remade the worm drive plate to improve some of the adjustment capabilities and added at the same time some decoration, rounded corners and used less material.
I used a Lovejoy type shaft connector to connect the motor to the worm shaft with a Buna-N spider in between to minimize any vibration or backlash to the motor, although with the worm and worm gear combination there should be none.
This step was made simple by the use of the CNC plasma cutter to make a part which I then bent up on both ends using my homemade brake. But first let’s revisit the old configuration for comparison.
I had to rob the motor and some parts from this transmission so it is in disarray but you get the idea of the complexity. It requires four sprockets, two chains, a motor and two chain tensioners. Here is a picture of the newly implemented and untested solution for mounting the worm and worm gear.
The CNC made it easy to slot the holes for adjustment, so the vertical adjustment comes from the plate to plate mounting screws, and the bearing mounting holes are slotted to get correct in and out adjustment to the keyed worm. After cutting the part and mounting it I decided what to change in the next iteration. I modified the part to round all the corners so that there are no sharp edges and extended the plate to pick up a second set of holes so the plates are attached with four screws instead of two. I think this part is perfectly functional so I won’t implement the changes but at least the SketchUp drawing has been updated.
After last winter’s experience, I decided to start from scratch on the auger/hopper assembly. I varied the height several times through different burner designs. Now it looks like it was modified once too many times. The other main reason to rebuild the hopper assembly is the difficulty removing the burner from the boiler because it must stay balanced. I don’t remember exactly my thoughts at that point, I probably just had two wheels around the shop and was in a hurry.
So this fall I am rebuilding the hopper with a different auger drive system, and additional wheels and supports to make it much more robust and simple. The foundation of improvement in the new assembly is the ability to draw the parts in SketchUp as well as cut the parts with the CNC. Here’s a view of the cut out parts.
The parts laid out I call the saddle, angle iron, and side alignment plate.
The parts below are the angle iron plate with the side alignment plate. The angle iron plate is tabbed to fit into the slots of the side alignment plate, this way the parts are self aligning and jigging. Adding strength and ease of assembly. This makes the welding so much easier.
Finally here is the assembly on the welding table ready to weld, note the threaded rod, which also aids in the rigidity and ease of adjustment to make sure all the pieces are square and parallel prior to welding.
And finally the partially finished welded assembly, this assembly will be the foundation to cantilever the auger in the feed pipe as well as support the auger drive motor and gears.
The CAD designed parts combined with the CNC, combined with self jigging design for success make a nice finished assembly with light material for cost savings combined with good strength.
Notice the title didn’t say completely finished since the last few steps are to improve the acme screw feed as well as add a water table, ventilation system and wire up a better connector for the torch control. But the paint looks great and the electrical components in a box is great. The part you see cut is intended to be the plate that is the interface between the boiler and the burner. I call it the burn plate. It will go into the opening in the boiler, the holes in the very bottom will allow a resistance heater to light the biomass either pellets or chips, the holes above are for draft. The large hole in the top center is for the auger feed and the remaining holes are on the left, a fire detector sensor and a hole to be tapped for attaching the sensor. The two holes in the upper right are intended to be the swivel point and observation port to observe the flame. I drew the part that you see pictured up in Google Sketch Up. What really impressed me about Sheetcam is that the piece to swing and hide the flame in the observation port was made at the same time from the scrap that was cut out of the auger hole. Sheetcam automatically figured out the hole in this swinging part should be cut as a hole with the offset of the kerf to be on the inside of the hole, then cut the remaining profile as a outside kerf, then cut the auger hole as an inside hole. This was all done in the correct order automatically. Cool! Sheetcam is a great program.