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.
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.
It may seem like a small bite but step two actually requires some machining and tweaking to get correct. In this step I am going to add the auger to the pipe assembly I have already built. To do this I need to support the auger with bearings so the shaft will be cantilevered in the pipe. The auger should not touch the pipe and needs to be centered in the pipe, at least within a reasonable distance. To do this I cut some 1 x 2 square tubing and then drilled holes on the Bridgeport using the Digital Readout to measure the distance so that the bearings would fit perfectly. These particular bearings are an oil impregnated bronze bushing in a pillow block configuration. The pillow block configuration is aluminum which makes machining the pillow block easy. Here’s a picture of the key way which I machined into a piece of 1″ cold rolled. If you have the choice cold rolled is much easier to work with then hot rolled for shafts. Of course this is really not shaft stock it is round stock but it works just fine and is inexpensive.
After welding the auger onto the shaft I do the calculations to center the shaft in the pipe. To make the shaft centered I have to mill some of the pillow block bearing, as you can see in the picture I had to use a circular shim to get the auger centered in the pipe.
Finally after some adjustment you can see the end result of the auger centered in the feed pipe.
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.
The plasma cutter is working in the CNC mode! I have successfully cut parts that meet dimensions and are usable. I made the plates that mate with the casters for the bottom of the machine this morning. I have them welded on and working. It was a treat bolting them together with no alignment issues without spending the time to make them on the Bridgeport.
The CNC is not finished, I have to mount the cable tracks, as well as extend some of the stepper motor wires to allow the full movement of the machine. Before I move on I want to put a coat of paint on the steel parts to make it look finished and professional. But an important milestone has been reached. This machine will allow me to make parts designed on the computer as well as improve the quality of the chip boiler parts significantly. This week I intend to finish the CNC and rebuild the hoppers support wheels. More pictures when I finish the CNC.
I have been following the pre buy prices of oil for a while now. For those of you unfamiliar with the term “pre buy”. It is what is sounds like, the price of the oil you will have delivered is prepaid by you and you and your supplier determine how many gallons you should buy. If you over buy you can usually take the remaining gallons you bought in a final delivery and store that amount in your own tank for next year. If you can’t hold that much you get a refund, but my supplier would not hold that price for anything longer than one season. If I under bought they usually would allow me the pre buy price on additional gallons if I used their estimate of how many gallons to buy.
Below is a .pdf chart of the pre buy prices by year. Note the chart also has a straight line regression trendline based on the existing data. The line is extrapolated out and predicts what the coming years prices may become. Note also that for a period of years the trendline and the prices were relatively accurate and tight to the trendline. I think as time goes on the market may become more volatile. The world market for oil is currently in the dollar currency. This may also add to the price fluctuations as the dollar currency may become volatile as well as the oil market’s geopolitical issues may also add to the fluctuation. Makes me want to get off the merry go round. Note clicking on the link should bring up the chart as a pdf file. Bear with me as a I try different ways to express things in wordpress. Suggestions are welcome.
To increase the combustion efficiency a second fan was added. The smoke coming from the boiler was very thick at times and really needed more oxygen. So a second fan was added, to help add more air and help keep the chip feed area cool. The parts slip together and allow a quick look down into the burner area. This allows you to be able to visually check on the feeding, and the fire by simply lifting the fan. So far I am happy with the change and the biggest difference is the ability to see the feed rate appropriateness. Already I want to change the program to allow smaller bites less often because the fuel is backing up the feed pipe. Because of computer issues, the laptop I was using wouldn’t recognize the USB port the Arduino is plugged into more than one or two uploads, I am attempting to switch computers. The 2nd computer at my disposal is running Windows 7. Not nearly as easy to use as XP Pro that I am used to using in opinion.
So, I am having difficulty communicating with the Arduino. I may have to go back to the first computer. Ain’t computers grand? I am a lot happier with a welder and plasma cutter. My weight this morning was 193.8, down 1.9 lbs. Probably water weight although I have stopped drinking beer for a little while. Ham sandwich in every bottle so a friend once told me.
A friend and excellent engineer visited over the weekend and between us we decided to improve the burner a little. The first change we decided to make was to add some insulation. I measured the temperature around the outside of the boiler with a non contact thermometer at approx. 350°F in the area of the firebox. The mounting plate that holds the burner was approaching that temperature as well. The air box was lower but still this is an excessive temperature. The Auger pipe was solid from the hopper to the burner unit and since I have both 4″ pipe and 4″ tube we decided to make a thermal break in the auger feed for additional safety. The 4″ pipe even though it is surrounded by the air box eventually gets warm and since the feed auger has a fair amount of room between the auger and the pipe there is a certain amount of fuel that remains in the pipe and at shut down this can smolder. So to remove this problem and make the unit more safe a redesign was initiated. Adding insulation between the air chamber and the burner with the addition of a thermal break prompted us to take the unit apart, check it over and see how everything was faring as well as make improvements. But of course after the burner and hopper were cut apart and on the bench more improvements were noted. Most of the improvements now fall into minor design for manufacturing type areas, maybe a little less welding and a little more tabbed nut and bolt assembly so minor changes can be made more quickly. Of course being able to pull the auger feed away from the burner assembly without unbolting anything will be a big change and improvement. I am going to make the air box bolt on as well. Should be reassembled for another test on Wednesday.
Of course it wouldn’t be a weekend if we didn’t play with the software. We added a For loop to the thermistor function to improve the accuracy. I added an array to smooth the results using a moving average. But most importantly we found the lingering problem with the LCD characters being garbled. It was a wiring issue. Now fixed it has run 24hours without a problem and I am confident it will stay fixed now. The next step will be to add a capacitor if the problem resumes. I am quite confident it will not be a problem however since it looks more solid even. There is less flickering and more solid character display. So all in all a fun and productive weekend.
The Arduino thermostat/circulator controller has now been tested and works, I bought an Adafruit DS1307 RTC and am now displaying the time on a 20x4LCD display. The relay board has been hooked up and now turns the circulator on or off according the time and temperature. The circulator pumps hot water from the boiler through the second coil in the solar thermal storage tank to supplement any heat that may be required due to an inadequate solar collection day. While the electronics now work nicely, the next step will be do put all the components in a neat case so that the project can be finished and mounted. Let me know if you would like a copy of the code or have any questions.
I harvested potatoes last weekend with the girls and the floor was covered. I had to clean up so I could work without stepping on vegetables. So that was job one on Sat morning, get more liquor boxes and get things cleaned. Finally finished that with help from the girls on Sunday morning. It snowed over the weekend so Sunday was spent plowing and going to a party at a friend’s house. On Saturday, with help from my 11 year old helper,I did get one half of the circulation loop for the heating of the solar tank installed.
Today’s goal is to finish installing the loop and run stub piping through the wall to where the chip boiler will be installed. I want to install the loop in the solar water tank to allow for more energy storage. This will allow more flexibility when the microcomputer is deciding where to put the heat from the chip boiler. Finishing the loop will also allow the Arduino Uno to be the thermostat controller hooked to the Boiler Boss. With a thermistor and LCD added to a relay board the Arduino can be the thermostat to run the zone. It seems to me this would be a great way to test the Arduino since all that can happen if the thermostat fails to work is a cold shower. Of course this assumes that the solar loop didn’t heat the water sufficiently and the solar can still heat the water hot enough for a shower on a good sunny day.
The boiler boss is one central control unit that contains all the relays for the zones. This box controls all the circulator pumps and the new circulator pump needs to be wired into this and the Arduino wired in as a thermostat.
So this weeks goals are simple: 1) Finish the solar hot water tank loop, wire it in and test with an Arduino controlling the zone, acting as the thermostat. 2) Apply the sealant to the chip boiler and test for leaks. 3) Work on the Chimney penetration through the rear wall of the shop for the chip boiler. This will be a straight 4″ pipe out since there is forced draft.
I got some good comments from a friend concerned with the temperature of the return water so I got a fresh battery for my non contact thermometer and took some temperature measurements of the zone water at the point leaving the circulator and just above the return manifold so here they are: 113 out and 98/99 back, not a lot of difference. The outside temp is approx. 30 (all temps F).
I am having a difficult time removing the end plug for the upper manifold, this is a 3/4″ black iron plug, I am thinking of using heat, any other suggestions, I am trying this plug with a 24″ pipe wrench, I am afraid if I try to use a cheater I will break something.