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: Engine thermodynamics|
I think that people are reluctant to comment on your assumptions because the expansion of steam in actual steam engines is very complicated. This Indicator LinK compares the actual indicator diagram from tests with theoretical values for saturated and superheated steam. You may find this study helpful for making assumptions.
|Thread: Model Turbines|
My new collet set arrived, so I finished more machining of the Drag Turbine 3 Housing. The housing was designed so that all the critical machining could be done without removing the casting from the 4 jaw chuck. This keeps all the bores as concentric and the faces as perpendicular to the centerline of the housing as possible. After I reamed the bore for the ball bearings, I inserted one of the ball bearings and checked the fit. It was a very tight locational fit that required a light push to insert or remove the ball bearing. After all the other machining of the faces and bores, I placed the rotor in the housing to see what the clearance of the outer face of the rotor was to the outer face of the housing. With the inner face of the rotor against the inner face of the housing, the clearance was less than 0.003” (0.08mm). A 0.003” feeler gage would not slide into the gap but a 0.002” feeler gage would slide in. This is very close to the 0.002” (0.05mm) total clearance I was hoping to get. While the housing is still in the 4 jaw chuck, I added shims between the ball bearings extended inner race and face of the rotor hub. I then pushed the assembly into the housing. With five 0.001” (0.025mm) shims, the inside face of the rotor cleared the inside face of the housing and the rotor would spin a few times when flicked with a finger. When I measured the clearance of the outer face of the rotor to the outer face of the housing, a 0.002” feeler gage could not be inserted. The following picture shows the rotor in the housing when the last measurements were made. I am very pleased with the results of the machining of the critical surfaces. It is a testament to the quality of the Unimat 3 and the EMCO accessories.
|Thread: Unimat 3 collet holder|
I received the collet set and it looks very nice. I don't have any dial calipers so I checked the runout as described below that was copied from an Email sent to a friend. The picture below was sent in the Email.
'The collet set actually got here on Friday even going thru the bad weather. The attached picture shows the setup I used to check the runout. I checked the runout by turning down a rod held in my 3 jaw chuck until it's surface was concentric with the lathe centerline. I then attached the new collet chuck to the machined portion of the rod. Next I mounted a face plate to the tail stock and moved the faceplate until it made first light contact with the collet chucks mounting face. The collet chucks mounting face protrudes about 0.4mm from the end of the chucks body. When I found the largest feeler gage that could be inserted in that gap, a feeler gage 0.025mm larger would not go in the gap at any rotation of the 3 jaw chuck. Also the force needed to slide the feeler gage seemed the same at any rotation of the 3 jaw chuck. I also shined a light on the opposite side of the tailstock at the contact edge of the collet chuck mounting face that was in light contact with the faceplate of the tailstock. No light was visible in any rotation of the 3 jaw chuck. I think the collet chuck and collets will be fine for my needs. The larger tommy bars he included in the set were welcomed by my arthritic hands. I am very pleased with this collet set'.
Thanks again for all your help,
This You Tube Video selling a EMCO Compact 5 and accessories shows the version of the EMCO 200 050 collet attachment that I believe I am purchasing. You can see from the video much clearer than from the Compact 5 Link I showed in the last post, how much different this version of the collet chuck looks than what was previously shown in this thread.
The seller had two collet sets. One was for the Compact 5 head stock and one was for the milling spindle. The one I purchased was the one for the milling spindle. With the M14x1 threads it will fit my headstock, tailstock, and milling attachment. Some of the pictures I found of the Compact 5 collet chuck for the milling spindle looked different than what was shown in the collet set. I found this Compact 5 Link that showed an accessory collet holder that looks like the one I purchased, so apparently the collet holder changed over the years.
Thanks for the feedback,
br thought his collet set was not the best for me based on our communications, so I searched for another collet set. This time I looked for something sold in the USA since the overseas shipping takes so long. I found on Ebay the collet set shown below. When I asked the seller if the parts were made by EMCO, he sent me the following response:
|Thread: Model Turbines|
The following picture shows the changes to the blades of Drag Rotor 3 in revison 2. I am trying to optimize Drag Rotor 3 based on everything I learn before making a casting. The following changes were made to revision 1. I made the slope from the bottom of the blades to the top of the blades similar to the contoured blades in the last post. The intent of this was to bias the flow direction toward the top of the blades to help start the circulation. I also recessed the front edge of the blades 0.010” back from the front of the rotor so that the major portion of the front could be cleaned up before any contact with the blades. I added a chamfer at the outer edge of the back face of the rotor to give a clearance for the point of the cutting tool when turning the housing bore. I shorted the length of the boss used for adding the metal during casting to reduce the amount of material required. All these changes were made to hopefully improve the performance, make the machining easier, and reduce the cost. Unless I find any further improvements after finishing the machining on the existing castings, this is what I plan to order next from Shapeways.
The attached figure shows the contoured blading that gave the best efficiency of the long blading discussed in the last post. The tests with the Chevron blading (Figure 2(e) in the last post) showed a maximum efficiency of 43% with blade angles of 45 degree. The maximum efficiency for 90 degree blades from these same tests was 40%. This confirmed Balje’s findings that the optimum efficiency was with blade angles from 40 to 45 degree, but had much less difference in efficiency with 90 degree blades as shown in the following table.
The collet set I ordered finally arrived. The runout of the collet holder was so bad I had to request a refund. I got a full refund from the seller and found another Ebay seller located in the USA that had a collet set with a genuine EMCO collet holder. I ordered that collet set and it should arrive within a week. When it arrives, I will finally be able to start the machining on the Drag Turbine 3 housing.
In the meantime, I found another article ‘A STUDY OF THE PERIPHERAL COMPRESSOR’ by Phillip Cates issued August 26, 1966 at this link Peripheral Compressor. Since this study deals with gases rather than liquids, it might be a better example of what to expect with semi-circular blades. The following figures copied from page 4 of this study shows the type of blading that was reviewed. Page 37 described what was found from the analysis and testing of a pump with the type of blades shown in Figure 2(b). The maximum overall efficiency for this type of blading was given as 46% when tested with a liquid. Page 111 showed the dimensions for a contoured blading that gave the best efficiency of any of the long blading shown in Figure 2(a). The maximum efficiency was given as 41% from testing with air. Tests with pumps typically show higher efficiency than tests using gases, but the half-torus blading appears to be quite effective.
One of my tool suppliers in the USA, McMaster-Carr, has drill point counter sinks that have drill points as small as 0.010" (0.25mm). These are what I use to drill holes this small.
|Thread: Collet runout. Is this normal|
I was luckier than you. I bought my collet set on Ebay and several people suggested that I request a refund. Ebay's refund policy is well thought out with protections for the buyers and sellers. I followed their instructions exactly, and although the seller did everything he could to avoid giving a refund, Ebay forced him to give a full refund. I hope that you can find a way to repair the collet holder. My runout was even worse than you got and one of the things I found that may apply to your collet holder, was the bore of the mounting hole of my collet holder had quite a bit of clearance with the lathe shaft it mounted on. Any machining done to correct the runout would not have worked without adding a sleeve and making a tight clearance fit between the chuck and lathe mount shaft.
Hope this helps,
|Thread: Unimat 3 collet holder|
Thanks to all of you that got me to request a refund. Ebay has a well thought out refund procedure that protects the buyer and seller. I followed their guidelines exactly as they instructed. The seller did everything he could to avoid giving me a refund but Ebay's rules forced him to give me a full refund. When he refused to send a return shipment label required by their rules, Ebay did not require me to send back the collet set. I lost a lot of time waiting for the collet set and getting the return, but thanks to all of you, it has not cost me any money.
Thanks again to all of you,
Thanks Bill, John, and Hollowpoint. I put in a request at Ebay to return the collet set. When I hear from the seller, I will let you know what he has agreed to. Ebay has a resolution policy that they will help if the seller and buyer can't come to an agreement.
Edited By Turbine Guy on 17/02/2021 19:40:25
Thanks for responding. All the accessories I have for my Unimat 3 that were made by EMCO have been outstanding, so I don't think you need to check the runout. EMCO's drill chuck for the Unimat 3 has better runout than some of the low cost collet holders. That is why I have been able to get by without a collet set.
The Ebay seller for the collet set I bought is jolgr3162 and has 99% positive feedback. He stated that the manufacturer was JJG Turning Milling Devices. All the parts came in sealed wrappers that had never been opened so I felt the seller was not at fault. I was unable to contact JJG Turning Milling Devices and don't know if they exist anymore.
I received the collet set that I ordered on Ebay. The runout was very bad so I looked for help to see if anyone else had this problem and what they did to fix it. I found the following thread Collet Runout that gave suggestions for correcting problems with collet holders. After trying some of the suggestions, I came to the conclusion that fixing the collet chuck is beyond my skill and equipment capabilities. After seeing the size of the ER-25 collet set, I agree with Emgee that an ER-16 collet set would be more appropriate for the Unimat 3.
I sent you a PM that I am interested in purchasing the E16 collet set if it is still available.
Thanks for your help,
Edited By Turbine Guy on 17/02/2021 13:12:41
|Thread: Jacobs Chuck run out|
I would expect much better run out. The EMCO drill chuck that I ordered with my Unimat 3 lathe several years ago has very little run out. I don't have a dial indicator to measure the run out, but I just used a 0.1245/0.1247 reamer held in this chuck to bore a hole for a 0.1250/0.1248 precision ground shaft and got the light press fit I hoped for. I recently purchased a drill chuck from LittleMachineShop.com and it appears to be almost as good. I think if you find the right source you should be able to get a much better drill chuck.
Hope this helps,
|Thread: Collet runout. Is this normal|
I just received a collet set that was sold in Ebay for use with Umimat 3 &4 lathes and was listed as made by JJG Turning Mlling Devices. I quoted this post by JasonB because I read it before my collet set arrived, and despite his excellent instructions, I had the same problems with runout as JDS. The collets and collet chuck were still in sealed bags so I don't believe they were ever used. I followed JasonB's instructions for putting the collets in the chuck and tried different sizes at the upper limit and lower limit printed on the collets. I also tried tightening them as much as I could using the bar and wrench included in the kit. In all cases I tried, the runout was worse than what I would get using my EMCO drill chuck and an additional drill chuck made by another unknown manufacturer. I mentioned the manufacturers name to caution anyone from purchasing a collet set shown as being made by them. I hope this helps someone from making the same costly mistake.
|Thread: Model Turbines|
The following figures and table are copied from ‘A modified theory for the flow mechanism in regenerative flow pump’ by J. W. Song, A Engeda, and M. K. Chung from the proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2003 found at this Link. The best efficiency for the radial blades like used in Dr. Balje’s reports is shown in Fig. 8 Test 2. The best efficiency for the semi-circle blade like my Drag Turbine 3, is shown in Fig.10. Table 1 gives the dimensions of these pumps. Rtip is the radius to the tip of the blade or channel, Rhub is the radius to the hub of the blade or channel, Ac is the area of flow channels, Bb, is the effective width of the blade channel, β is the blade angle, Zb is the number of blades, and C is the clearance. Q/Qs is the ratio of the flow to the solid rotation flow. You can see from the figures that the peak efficiency of the semi-circle blades is slightly higher, but the estimated performance of the radial blades is much closer to the test values.
Edited By Turbine Guy on 10/02/2021 18:47:16
I read through the section on Drag Turbines again in ‘A Study of High Energy Level, Low Power Output Turbines’ done for the Office of Naval Research in 1957. This study concluded that the increased drag on the rotor was due to the corkscrew rotation of the flow into the bottom of the blades and out of the top of the blades into the flow channel as discussed in the 09/12/2020 post in this thread. This study also stated that the drag coefficients were independent of the rotor speed that had been confirmed with tests of the stall torque. I designed Drag Turbine 3 based on the concept used by Spencer in their Vortex Regenerative Blowers as shown in the 09/12/2020 post and below. I thought that the Spencer concept would increase the rotation of the gas due to the flow being guided back into the flow channel by a radius rather than being discharged onto a flat surface like shown for the two-sided impeller. The two-sided impeller was the type used in the study and the drag coefficients were developed for. If the corkscrew rotation of the flow is what causes the higher rotor drag coefficient and the rotor drag coefficient is independent of rotor speed, the corkscrew flow must be established even with the rotor stationary. Comparing the one-sided and two-sided impellers, I can see that any flow from the stationary channel that enters the two-sided impeller is guided towards the OD of the impeller. This would start the flow moving in a corkscrew direction even with the impeller stationary. For the one-sided impeller, any flow from the stationary channel that enters the impeller is guided toward the center of the blades when the impeller is stationary. I assumed that the centrifugal force would start the flow moving out the outer part of the blade when the rotor got to the higher speeds and provide the necessary circulation. In the next post I will show a source with test results for these two concepts.
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