Bill Dunlap Posted April 26, 2023 Author Share Posted April 26, 2023 12 minutes ago, Louis Luu said: I think Bill is shooting for a Toroidal Contra Blade? That could work. It even has an option for CW vs CCW blades which is what I need. The price is very reasonable, too. I'll get specs here soon. I'm about ready to mount a motor with enclosed gear train (containing grease) on a test bed. I'll like make a couple of prop type blades on this one just for testing while I wait for toroidal one to get printed. Cheers, Bill Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 26, 2023 Share Posted April 26, 2023 1 minute ago, Bill Dunlap said: That could work. It even has an option for CW vs CCW blades which is what I need. The price is very reasonable, too. I'll get specs here soon. I'm about ready to mount a motor with enclosed gear train (containing grease) on a test bed. I'll like make a couple of prop type blades on this one just for testing while I wait for toroidal one to get printed. Cheers, Bill I say we get it printed in plastic first....that will be dirt cheap. Once you are happy, we can get them printed in aluminum for lightweight and strength. Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted April 26, 2023 Author Share Posted April 26, 2023 👍 Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted April 26, 2023 Author Share Posted April 26, 2023 OK, Louis, I don't understand all the parameters that are required, so maybe you can help here. #Blades 2 Height .250 (6.25mm) Blade length or radius 100mm for 8 inch width blade total. Blade width Not sure. Isn't it determined by the pitch? Blade thickness . (same as height?) Maybe this is the thickness of the wing. 4mm is OK Blade offset thickness What is this? Blade twist. 15? No idea what to choose here. So one at 15 and one at -15. Blade offset Is this hub thickness? Safe blade direction No idea....... Hub diameter. Same as blade offset? I need a hub at about .750 diameter. Hub screw diameter. Is this set screw? #8 would do. One blade will mount on a .250 shaft (CW) and the other on a .500 shaft. (CCW) Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 26, 2023 Share Posted April 26, 2023 2 hours ago, Bill Dunlap said: OK, Louis, I don't understand all the parameters that are required, so maybe you can help here. #Blades 2 Height .250 (6.25mm) Blade length or radius 100mm for 8 inch width blade total. Blade width Not sure. Isn't it determined by the pitch? Blade thickness . (same as height?) Maybe this is the thickness of the wing. 4mm is OK Blade offset thickness What is this? Blade twist. 15? No idea what to choose here. So one at 15 and one at -15. Blade offset Is this hub thickness? Safe blade direction No idea....... Hub diameter. Same as blade offset? I need a hub at about .750 diameter. Hub screw diameter. Is this set screw? #8 would do. One blade will mount on a .250 shaft (CW) and the other on a .500 shaft. (CCW) Just got home. I'll take a look at it later on tonight. Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted April 27, 2023 Author Share Posted April 27, 2023 Now that it's become clear that we are dealing with just a variation in a concept thought out decades ago (MIT didn't invent anything here) I've been thinking more about it and doing more research. One thing that has my curiosity piqued is that with any new submarine that has recently been released, the props are always either shrouded, or the photos are blurred. I definitely want to see those designs. The main thing with subs is that they need to be absolutely silent in operation. There are probably a dozen or more designs you can see that are not secret anymore. That means they've come up with something better. Cheers, Bill. Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 27, 2023 Share Posted April 27, 2023 (edited) I set the blade thickness to 2mm and the width to 30mm across.....40 would have too much overlap. The pitch is 15 degrees. The overall blade size is 8 inch per your instruction. I prefer to put a single hole in it and let you enlarge it....don't really know which is CW or CWW (Unless you can tell me which ones are which)? Also, you stated 6.25mm....I think you meant 6.35mm for the height? I made it 6.35mm. Let me know if this is acceptable and I will smooth out the surface. Edited April 27, 2023 by Louis Luu Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted April 27, 2023 Author Share Posted April 27, 2023 Louis, Can you make it a 3 wing blade, and widen the wings like the original drawing? Cheers, Bill Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 27, 2023 Share Posted April 27, 2023 30 minutes ago, Bill Dunlap said: Louis, Can you make it a 3 wing blade, and widen the wings like the original drawing? Cheers, Bill I'll do it when I get home. I say we keep this one and test it out along with a 3 blade. Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted April 27, 2023 Author Share Posted April 27, 2023 Sure why not? I've finished one blade of the contra-rotating test bed, with enclosed gear train, so I'll post something on that maybe later today or tomorrow. Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 28, 2023 Share Posted April 28, 2023 Width is 40mm...the rest of the parameters are the same. Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted April 28, 2023 Author Share Posted April 28, 2023 Yeah, that's what I'm talking about. Made some progress today while stuck indoors with crappy weather.(been like this for a couple months) Well, now I know how to do it. Just need improvements. Cheers, Bill 1 Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 28, 2023 Share Posted April 28, 2023 I'll order the toroidal blade and send them your way. Would love to see the gear box when you take it off. I have my own ideas but want to see what you came up with. Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 28, 2023 Share Posted April 28, 2023 Done. Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted April 29, 2023 Author Share Posted April 29, 2023 Louis, here's a visual breakdown of the gearbox. Bear in mind that I would probably include either sealed miniature ball bearings or oilite bushings for the two outer gears for durability. For a test bed I didn't bother. The intermediate gear is adjusted for fit by washers behind it and also the shaft is located in a slotted hole for fore and aft adjustments. The output gears is fitted by means of a washer between it and the front cover. All gears are only located on one side, the outer sides of each of them. They are otherwise free to float. I suspect the noise problem with this gear train is down to the intermediate gear, which is aluminum and may be of a different specification than the brass gears. (I'm no gearologist) So, I've ordered a new pair to prove one way or the other. 1 Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 29, 2023 Share Posted April 29, 2023 I'll go ahead and place your order this weekend. Please let me know if your new gear setup reduces the noise. I'm still undecided to go with plastic or steel. Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted April 29, 2023 Share Posted April 29, 2023 Order placed for 4 blades. 2x2 Toroidal; 2x3 Toroidal. There was another type of plastic I wanted to tested but don't know the strength....supposed to look like wood grains with different options for wood color. I'll try it out on one of my other projects. Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 4, 2023 Author Share Posted May 4, 2023 My latest attempt to work out the bugs of the contra-rotating blade gear drive was to build a friction drive and test it. See pic. Note the use of thrust bearings to isolate the output drive hub. This hub has the hardest life because the bearing speed it rides on experiences twice the rpm of the armature shaft. Ideally, it would ride only on bearings like this in order to be durable. That would require me to have a lathe unless I can think of a way to do it with simple tools. I think that would reduce noise to zero. Right now there is a little rattle, mainly due to looser tolerancing. Without a machine shop, I can only get it close. Onwards and upwards. Cheers, Bill 1 Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 4, 2023 Author Share Posted May 4, 2023 Oh, I forgot. I tried new gears in the gearbox and it made no difference at all. So, plan B. Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 9, 2023 Author Share Posted May 9, 2023 I figured out how to do this and address all the issues I've encountered while doing this. First is a short video showing the current friction drive where the reverse output shaft rides directly on the armature shaft and with the bearing experiencing twice the motor speed. Brass on steel is an adequate bearing surface, but it requires lubrication which I need to avoid since it's a friction drive. So, I sourced miniature sealed bearings of an appropriate size and modified the output driven bobbin to accept them. Now there is no need for any lubrication as the driven discs ride on oilite bearings. It is maintenance free and almost silent. The second part of the video demonstrates this. This is definitely the way to go. Cheers, Bill ContraRotatingDesignMod.mp4 1 Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted May 9, 2023 Share Posted May 9, 2023 (edited) I took your previous idea and used bearing system as well. Only problem, I don't know how to extend the rod. Can an existing rod be brazed onto the motor shaft? I will go with nylon bevel gear. The shaft will ride on ball bearing. Edited May 9, 2023 by Louis Luu Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 9, 2023 Author Share Posted May 9, 2023 I did extend the armature shaft on this motor. I center drilled the shaft, tapped it to 8-32 and used a piece of the same diameter brass. It's not meant to be production quality.... Those motors are available with several different armature shafts. One is very long and threaded on the end. That's the one I used for this project, but shortened the shaft and turned it down to 1/4" for most of it's length. Have a look on Amazon or elsewhere where they sell these motors. Cheers, Bill 1 Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted May 9, 2023 Share Posted May 9, 2023 4 minutes ago, Bill Dunlap said: I did extend the armature shaft on this motor. I center drilled the shaft, tapped it to 8-32 and used a piece of the same diameter brass. It's not meant to be production quality.... Those motors are available with several different armature shafts. One is very long and threaded on the end. That's the one I used for this project, but shortened the shaft and turned it down to 1/4" for most of it's length. Have a look on Amazon or elsewhere where they sell these motors. Cheers, Bill Thank you. Your blades should be about two more weeks....maybe shorter. I can't wait to see you put them on and see how they perform. Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted May 9, 2023 Share Posted May 9, 2023 This should do the trick. 1 Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 9, 2023 Author Share Posted May 9, 2023 That is a physically larger motor than what I used. Just so you're aware. All dimensions except shaft diameter are larger. Quote Link to comment Share on other sites More sharing options...
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