Here is a list of all the postings Turbine Guy has made in our forums. Click on a thread name to jump to the thread.
|Thread: Model Turbines|
When setting up the indexer as shown in the picture of the last post, it is very important that the face of the rotor is parallel with the direction of movement of the cross slide. This will keep the sides of the pockets parallel to the rotor faces. After I have the indexer carefully squared up and bolted firmly to the mounting plate, I adjust the rough position of the end mill. I set up the end mill to a position that when it is fully retracted, it’s end will be slightly above the rotor. I then lock the milling attachment in position and make all the changes of rotor position with the carriage using the cross slide and long slide. I set the position of the long slide first. I move it to position that the end mill is on the left side of the rotor and then extend it down far enough that it will overlap the face of the rotor for most of it’s cutting length.. I then move the long slide until the end mill contacts the rotor face and read the scale on the long feed handwheel. Next, I raise the end mill enough to clear the top of the rotor. Then I move the long slide to the left using the scale on the handwheel to move the correct distance. The distance of this move for the turbine shown in the preceding drawing is 0.092”. I then lock the carriage in that position. The next thing to do is position the end mill to where its center is close to the center of the rotor. Using the fine feed of the mill chuck, I then lower the end mill until it contacts the top of the rotor and note the reading on the scale of the fine feed. Next the rotor is moved by the cross slide far enough that the end mill can be lowered without contacting the rotor. Then using the mill chuck fine feed, the end mill is lowered to the correct distance from the top of the rotor. The distance of this move for the turbine shown in the preceding drawing is 0.057”. The mill chuck fine feed is then locked in that position. Note that the most important distance is from the center of the rotor to the bottom of the end mill (0.555). If the actual rotor OD is correct, then the 0.057 distance can be used. If not, the correct distance should be determined by subtracting the 0.555 from the actual radius of the rotor. The last thing for this setup is determining the end of travel for the cross slide. Move the cross slide until the end mill first contacts the rotor. Note the position on the cross slide handwheel and then start the motor and make the first cut the correct distance. The distance of this move for the turbine shown in the preceding drawing is 0.082”. Note the handwheel position at the end of travel. If you can’t set up a stop for the cross slide, the cross slide will have to be moved out far enough to clear the rotor and then moved back to this position for each movement of the indexer. If you can set up a stop, you still need to move the cross slide in and out, but you don’t have to keep track of the number of turns of the handwheel. These are the steps I’ve used to make three rotors using my equipment and lack of measuring devices. Hopefully, some of this discussion will be helpful.
After the rotor is machined to where the OD and thickness are slightly oversize, the bore for the rotor shaft is drilled and reamed. Next the rotor bore has a thin coating of Loctite 290 added and then the rotor pressed into position. The initial grip of Loctite 290 is relatively quick so the rotor needs to be in it’s correct position and the excess Loctite wiped off as soon as you can. The Loctite will also glue your chuck jaws to the rotor shaft if you allow it to flow onto the jaws. I allow 24 hours for curing time to get the full strength of the Loctite before facing both sides of the rotor and machining the OD to their final dimensions. The next step is machining the pockets. The photo below shows the setup I use to make the pockets. I used my rotor 1 in this photo since the larger pockets and the brass shows the pockets clearer. I will describe how I position the end mill and machine the pockets in the next post.
The following drawing shows the Turbine 3 SD rotor. I’ve made rotors out of brass and silver soldered them to the stainless steel shafts and made them out of aluminum and used a light press fit with Loctite 290. I prefer the aluminum since it is less expensive and reduces the rotating mass. I extended the shaft on both sides of the rotor to use Werner Jeggli’s method of balancing the rotors. I will explain his method in another post. I thought of adding the shaft extension after making the assembly drawing, so it doesn’t show up on it. I don’t have anything for measuring except a dial caliper with +/- 0.001 accuracy so I use precision ground shafting for the rotor shaft. I will show the setup I use for making the rotor pockets and explain the steps I use in the next post.
Most of the materials, parts, and tools needed to make Turbine 3 SD can be purchased from McMaster-Carr. The following shows McMaster-Carr part number and cost of each item. You can open McMaster-Carr using the link and type in the part number to get a picture and full description.
The following drawing is the cleaned up version of Turbine 3 SD. This turbine can be made with most materials, parts, and tools purchased from one source as will be shown in the next post. To make it the way I have, requires a mill or milling attachment and an indexer. I used the milling attachment and indexer available for my Unimat 3. All the Unimat accessories have threads that allow mounting of all the chucks so a part mounted in a chuck can be mounted on the lathe, mill, or indexer without removing it from the chuck. I was able to do all the critical machining of the parts without removing them from the chucks.
My goal when I started this thread was to come up with a turbine design that could be made by modelers with small lathes and require no more equipment than is necessary to make a small steam engine. My goal was also to come up with a turbine design that matched the performance of the available model steam engines. I purchased three model steam engines shown in the photo and ran tests of them in the Testing Models thread The following table shows the comparison of the last tests with my Turbine 3 SD and the Saito T-1 that had the best performance of the three purchased steam engines. Turbine 3 SD met all my goals, at least, for running on air with my airbrush compressor. The Testing Models link shows the updates to the drawings of Turbine 3 SD to show the last changes made to the rotor and assembly. The updated drawings show all the changes including those to correct mistakes or needed for other concepts no longer used. I will make new drawings showing the turbine design cleaned up and representing what worked the best from all my testing.
Edited By Turbine Guy on 24/11/2020 12:54:39
|Thread: Good idea for a scratch built engine|
I watched all three videos and enjoyed every minute. Thanks for sharing this. Your friend is amazing.
|Thread: Steam engine from scrap metal|
I wouldn't hesitate to use carbon steel parts. If you wipe them over with a oily cloth like Nigel suggested or spray them with WD40 like I do after each run, they can be rust free for quite a long time. The following photo is my Chiltern steam engine that hasn't been run for months. The base plate, crankshaft, bottom cover plates, columns, slider tube, and fasteners are all unpainted carbon steel. The plate the engine is mounted on is stainless steel. I originally planned on painting most of the carbon steel parts, but Chiltern did such a nice job on the finish, I liked the appearance of them unpainted.
I agree with all of JasonB's comments. Unless you plan to operate your steam engine at a high speed (which I suggest you don't do), a small piston valve will work fine. To prevent getting yourself in a bind, I suggest you look at some of the drawings available in ME like the Example Drawing. This will give you an idea of the proportions of the parts, how they fit together, and examples of methods for making difficult parts. In this example, a method of making the double throw crank shaft is about as simple as I have seen. I will leave suggestions for machining up to others on this website that have far more skill and experience.
Good luck with your engine,
|Thread: Testing Models|
I updated the table shown in the post of 12/07/2020 to include the tests of the Saito T-1 steam engine. I added a disclaimer to the notes included with the chart that the test power shown for speeds below 1,000 rpm may not be valid. The performance given by APC for their propellers is not shown for speeds below 1,000 rpm but since the power coefficient increases at lower speeds due to the Reynolds number effects, the test power shown should be conservative for the lower speeds.
|Thread: Steam engine from scrap metal|
Thanks for adding the photos and drawings from an album. I can see them now. My computer is quite old and I may not have the apps needed to view them the way you originally posted them. I agree with Jason B that your valve diameter is quite a bit larger than optimum. The two steam engines I own with piston valves are a Chiltern and a Saito. The Chiltern has a 14mm piston diameter, a 7mm valve diameter, and relies on a close fit for sealing. The Saito has a 8.8mm piston diameter, a 3.8mm valve diameter, and relies on a close fit for sealing. Both of these engines have relatively low leakage from the valves.
I can't find any way to view your photos or sketches. If you can make the photos and sketches into JPG files and add them in your album. You can add them to a post by clicking on the camera icon and selecting the file you want to show. They will appear like the following example.
|Thread: Testing Models|
The following table shows the groove dimensions for the 2-115 size O-ring you will need for your 22mm bore. The amount of leakage with the floating O-ring is more than offset with the reduction in friction. You can also use packing in the groove if you want to try that. The pest performing packing I have tried was suggested by Thor. I spun Teflon tape into a thread and wound it into the O-ring groove as tight as I could. When you add oil the small spaces in the packing absorbs some of the oil and it wicks out while running. The wicking of the oil and the lubricity of Teflon reduces the friction considerably.
The following was copied from the Parker Metric O-ring catalog. It explains the concept of the floating O-ring. In the next post I will show a copy of the table that gives the groove dimensions for the metric floating O-rings.
I will try to answer the questions from your last two posts partially copied below.
I was interested in a comment in the thread that the turbine jets go "sonic" at 25 psi. It is important to show the pressure as absolute (psia) or gage (psig) and the gas (steam, air, etc.). The critical pressure ratios are 0.528 for air, 0.547 for superheated steam, and 0.577 for saturated steam. For air with the exit pressure being atmospheric (14.7 psia), the inlet pressure would have to be 14.7/0.577= 25.5 psia = 10.8 psig to go sonic.
For simplicity I am thinking of using O-rings for piston seals. To keep friction down I understand they would be fitted loosely. I imaging they should only just touch the cylinder walls with no perceptible compression. Is that right? I tried both floating and light compression of the O-rings. The floating type as described in the follwoing link worked best. Floating O-ring
I am using pistons as valves instead of the usual flat plate so that I can do it easily on the lathe. Can I use rings on these valve pistons too or will they get torn up by the ports? Both of my steam engines that use piston valves rely on a close fit and have very low leakage. Whatever gain you get with seals will probably be offset by the extra friction.
My radiator man found that it had 5 O-rings from China that had gone soft and gummy, completely flattened. But why did it pass pressure tests? If the pressure is enough to move the O-ring, it will press against the sealing surfaces and stop the leakage.
The engineering Co A&G Price Foundry I was talking about had a license to male Doble steam buses for Auckland City. Would they have been turbines? I think the only steam buses tried in California were the Lear turbine. There were other competitors and might have been tried.
Edited By Turbine Guy on 18/11/2020 14:30:33
I’m glad you found this thread interesting. Those of us that go so deeply into the details, are a very small minority. I followed your link and found your discussion of the Hero turbine very enlightening. What you found in trying to find the best compromise between leakage and friction will be your biggest challenge with the piston seals. I have discussed in this thread tests of several small steam engines with different piston seals you might find useful. Most of these tests were with air since it was much easier to setup, eliminated the effect of moisture content, and the output of my airbrush compressor was more consistent. If you run on air and lubricate the engine by putting a few drops of oil into the inlet before starting your test, you can only run a short time before the oil escapes. Packing that absorbs the oil will extend the useable run time. My tests with steam and the displacement lubricators indicated that they work for much longer run times. I look forward to what you find in your testing of the piston seals.
Keep up the good work,
The following drawing shows the Turbine 3 rotor modified to side discharge (SD) by removing one row of pockets.
The following drawing shows the dimensions of the nozzle and rotor in turbine 3 to change to side discharge (SD). This drawing also shows the position of the parts that gave the best performance. The position of the new nozzle was the result of trying to add other nozzles that failed by the drill drifting or breaking. This was about the only space left. Ideally the nozzle would be placed at the top of the turbine so that condensed steam would not collect around the nozzle. The next post will show the changes of the rotor to make it side discharge.
I have been running my Turbine 3 SD on air trying different combinations of shims on the rotor and clearance between the collar and the outer ball bearing. The best combination was with 7 shims on the rotor and 0.004” spacing between the collar and outer ball bearing. With this combination, I got the highest speed running on air with my EP 2508 propeller of any of my turbines. The speed obtained was 25,000 rpm. The post of 29/07/2020 in this thread showed the results for the test of the Saito T-1 steam engine running on air. The Saito T-1 had the best performance of all my small steam engines running on air or steam. The following chart shows a comparison of Turbine 3 SD and the Saito T-1 steam engine running on my airbrush compressor. Since Turbine 3 SD has turned out to be my best performing turbine and I have only showed the modifications to make the side discharge (SD) in the Model Turbines thread, I will show these changes in the next posts. The post of 27/09/2020 in Model Turbines is the start of the discussion of the change to side discharge.
In a conversation with Mike Tilby, the subject came up about my first turbine project. I helped in the design of a turbine for Lear Motor Corporation. This turbine originally was intended to run on an organic fluid to keep the speed of the turbine lower. None of the efforts to keep the organic fluid from breaking down in the boiler worked, so eventually the design was changed to running on steam. Lear found people talented enough to design and make the bearings, seals, and gears operate at 60,000 rpm. I left Lear Motor Corporation before the turbine was ever tried in a vehicle. I was too young at the time to realize the importance of keeping records of my early projects so I don’t have any of the test results I was involved with in the development of the turbine. In trying to find out the actual output of the turbine, I found the articles shown in the following Lear Bus Link. The articles included in this link have enough information to evaluate the maximum performance of this turbine. I thought I would compare this turbines performance with that of one of Abner Doble’s steam engines that was probably one of the best ever put in a car. I got the test results of the Doble Model E engine from the book ‘Doble Steam Cars, Buses, Lorries, (trucks) and Railcars’ by J. N. Walton. The following table gives the results of this comparison. The Doble test was run June 16, 1928, so even though this engine was made 44 years before the Lear turbine, it had higher efficiency. Neither of my sources told what accessories were included in the tests, so the comparison might be slightly unfair. The water pump alone is a fair amount of power for these mass flows and pressures. I know this is a testing models thread, but I thought some of you might find this interesting.
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