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Coupling misaligned shafts
This is related to my dynamometer thread. We didn't find anything, so
I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Coupling misaligned shafts
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Coupling misaligned shafts
"Tim Wescott" wrote in message ... This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com ================================================== ==== You'll probably need to be closer than 5 degrees, as Lloyd said, but two simple couplings are the Lovejoy that he mentioned, and the Oldham coupling. The Oldham allows quite a bit of shaft misalignment, but *not* angular misalignment. You might get away with a rag joint -- a steering-column coupling. Ed |
Coupling misaligned shafts
On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott
wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. ============= Lovejoy http://www.use-enco.com/CGI/INSRIT?P...FSxo7AodjjsAqw cnc zero backlash coupler http://www.tpa-us.com/shaft-coupling...FXNo7AodKRwAKw What have you considered for the absorber? electric motor/generator? http://freeideas.bizhat.com/drives/feedback/index.htm hydraulic pump? http://www.micropump.com/pump_overview.aspx magnetic clutch with scale and tach? http://www.youngssurplus.com/clutches.htm -- Unka' George "Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants, but debt is the money of slaves" -Norm Franz, "Money and Wealth in the New Millenium" |
Coupling misaligned shafts
On Tue, 08 Jul 2014 16:31:25 -0500, F. George McDuffee wrote:
On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. ============= Lovejoy http://www.use-enco.com/CGI/INSRIT?P...Didit-_-SEM-_- GglProd-_- GglProd&003=18299132&010=990-4046&gclid=CJPGvbjRtr8CFSxo7AodjjsAqw cnc zero backlash coupler http://www.tpa-us.com/shaft-couplings.html? gclid=CLbY26zTtr8CFXNo7AodKRwAKw What have you considered for the absorber? electric motor/generator? http://freeideas.bizhat.com/drives/feedback/index.htm hydraulic pump? http://www.micropump.com/pump_overview.aspx magnetic clutch with scale and tach? http://www.youngssurplus.com/clutches.htm I'm probably going to use a motor. I need to drive as well as absorb. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Coupling misaligned shafts
On Tue, 08 Jul 2014 16:09:12 -0500, Lloyd E. Sponenburgh wrote:
Tim Wescott fired this volley in news:4o- : So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? Tim, This sounds like it might be a bit out of your ken. First, a five or ten degree mis-alignment between shafts almost demands a CV joint, and they're not 100% efficient except when running perfectly axially. If you can't joggle things to be within a degree or two, you're just not going to get what you want, unless you belt drive the sucker. Put a sheave on the driving element, and a sheave on the torque sensor, and do it that way. Otherwise, a simple, cheap coupling for minor misalignments is called a "Lovejoy Coupling". It transmits torque effectively with only minor heat losses and also cushions any shocks in the train. Lloyd Better than five degrees could be done, but with more fiddlin' and fussin'. This doesn't have to be small for it's strength, so something outside the usual machine design box may do. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Coupling misaligned shafts
On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote:
This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. And, if this sounds interesting and you're within driving distance from Portland, Oregon, send me an email -- I can do all the work myself, but farming it out may be better for my customer, if you've got the right skill set. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Coupling misaligned shafts
"Tim Wescott" wrote in message
... This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com http://www.lovejoy-inc.com/products/...couplings.aspx |
Coupling misaligned shafts
On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott
wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. #2 is called a belt. |
Coupling misaligned shafts
On Tue, 08 Jul 2014 16:23:45 -0500, Ralph
wrote: On 7/8/2014 4:09 PM, Lloyd E. Sponenburgh wrote: Tim Wescott fired this volley in news:4o- : So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? Tim, This sounds like it might be a bit out of your ken. First, a five or ten degree mis-alignment between shafts almost demands a CV joint, and they're not 100% efficient except when running perfectly axially. If you can't joggle things to be within a degree or two, you're just not going to get what you want, unless you belt drive the sucker. Put a sheave on the driving element, and a sheave on the torque sensor, and do it that way. Otherwise, a simple, cheap coupling for minor misalignments is called a "Lovejoy Coupling". It transmits torque effectively with only minor heat losses and also cushions any shocks in the train. Lloyd Belts would have more heat loss than a coupler. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com A timing belt drive is extremely efficient |
Coupling misaligned shafts
On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott
wrote: snip The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). /snip ===================== This simply adds another spec/requirement. You will have to have some way to rigidly mount the test assembly. This seems to indicate that either the test assembly mount and/or the absorber mount must be adjustible in the XYZ directions and rotations about the X and Y axis. Then you will need a gage set-up to align the two shafts. There are a ton of videos on YouTube on shaft alignment heres one to start https://www.youtube.com/watch?v=9JCbdDNyUPQ A sleeve with reamed holes [several diameters deep] for the shafts may be accurate enough. If not, here are some URLs that may give you some ideas [most likely you already have the drop indicators] or align off the couplings if you use flange gear type couplings with external driving bands.. http://www.google.com/search?q=dial+...w=1207&bih=523 http://www.mitchellinstrument.com/me...arter-kit.html http://www.solarstop.net/mrshims/shaftalignment.asp http://www.skf.com/group/products/ma...a11/index.html http://www.skf.com/group/products/ma...a20/index.html http://www.google.com/url?sa=t&rct=j...,d.aWw&cad=rja -- Unka' George "Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants, but debt is the money of slaves" -Norm Franz, "Money and Wealth in the New Millenium" |
Coupling misaligned shafts
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Coupling misaligned shafts
On Tue, 08 Jul 2014 20:26:30 -0400, clare wrote:
On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. #2 is called a belt. Not if I can't easily mount it concentric to the axis of rotation. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Coupling misaligned shafts
On Tue, 08 Jul 2014 19:52:15 -0500, Tim Wescott
wrote: On Tue, 08 Jul 2014 20:26:30 -0400, clare wrote: On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. #2 is called a belt. Not if I can't easily mount it concentric to the axis of rotation. you will also hace considerable side loading which may be important, whch will be avoided with a shaft coupling. -- Unka' George "Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants, but debt is the money of slaves" -Norm Franz, "Money and Wealth in the New Millenium" |
Coupling misaligned shafts
On Tue, 08 Jul 2014 19:52:15 -0500, Tim Wescott
wrote: On Tue, 08 Jul 2014 20:26:30 -0400, clare wrote: On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. #2 is called a belt. Not if I can't easily mount it concentric to the axis of rotation. OK, spill the beans--- What is the application??? Picture or diagram, or at least a good description?? How about a hunk of hose the right size to fit the shaft, and a couple of hose clamps. Braided hose if required. Even steel braid. You are only talking 80RPM from what I remember - and what torque, again??? And I'm assuming you mean parallel to the axis of rotation. |
Coupling misaligned shafts
On Tue, 08 Jul 2014 19:32:41 -0500, F. George McDuffee
wrote: On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote: snip The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). /snip ===================== This simply adds another spec/requirement. You will have to have some way to rigidly mount the test assembly. This seems to indicate that either the test assembly mount and/or the absorber mount must be adjustible in the XYZ directions and rotations about the X and Y axis. Then you will need a gage set-up to align the two shafts. There are a ton of videos on YouTube on shaft alignment heres one to start https://www.youtube.com/watch?v=9JCbdDNyUPQ A sleeve with reamed holes [several diameters deep] for the shafts may be accurate enough. If not, here are some URLs that may give you some ideas [most likely you already have the drop indicators] or align off the couplings if you use flange gear type couplings with external driving bands.. http://www.google.com/search?q=dial+...w=1207&bih=523 http://www.mitchellinstrument.com/me...arter-kit.html http://www.solarstop.net/mrshims/shaftalignment.asp http://www.skf.com/group/products/ma...a11/index.html http://www.skf.com/group/products/ma...a20/index.html http://www.google.com/url?sa=t&rct=j...,d.aWw&cad=rja Haw about a prony brake that fits right on the shaft of the motor?? Again, we really need a picture, or at least a better description of what you are working on. |
Coupling misaligned shafts
On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott
wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. "Helical coupler" is what you are looking for. http://www.rocomcorp.com/ etc etc What size shafts are you going to be using? I have a drawer full of all different sizes. Let me know and I can find something for you. Gunner -- "Living in the United States now is like being a Tampon. We're in a great place, just at a bad time." |
Coupling misaligned shafts
On Tue, 08 Jul 2014 22:38:27 -0400, clare wrote:
On Tue, 08 Jul 2014 19:52:15 -0500, Tim Wescott wrote: On Tue, 08 Jul 2014 20:26:30 -0400, clare wrote: On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. #2 is called a belt. Not if I can't easily mount it concentric to the axis of rotation. OK, spill the beans--- What is the application??? Picture or diagram, or at least a good description?? How about a hunk of hose the right size to fit the shaft, and a couple of hose clamps. Braided hose if required. Even steel braid. You are only talking 80RPM from what I remember - and what torque, again??? And I'm assuming you mean parallel to the axis of rotation. It's for a customer, so I have to be all secretive. Which is a pain, I know. Things could, in theory, be mounted dead center on a shaft on the device under test, but doing so would require some disassembly and reassembly to do the test. I'll go there if I must, but I'd much rather have something that'll work anywhere, anytime. 50 newton-meters, whatever that works out to in 'merican units. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
Coupling misaligned shafts
"Tim Wescott" wrote in message ... This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Perhaps a roller chain coupling would be suitable if the angular misalignment is not severe. -- Regards, Chas. (To email me, replace "xxx" with letters tango papa golf.) |
Coupling misaligned shafts
On Tuesday, July 8, 2014 8:50:31 PM UTC, Tim Wescott wrote:
The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). Tim Wescott Wescott Design Services http://www.wescottdesign.com This is just a wild idea, but how about a hydraulic pump driving a hydraulic motor. They could be sized so there is a speed up of the RPM's. It would solve all the alignment problems. Or just a hydraulic pump with a needle valve as the load. Use a optical tachometer from China to get the RPM and a pressure transducer on each side of the pump to get the torque. Dan |
Coupling misaligned shafts
On Tuesday, July 8, 2014 4:50:31 PM UTC-4, Tim Wescott wrote:
This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. Hi Tim, I didn't chase down all the links others posted, so perhaps it's already been mentioned, but I used a bellows shaft coupler. (not cheap) Link to the first hit on google. http://www.rw-america.com/products/bellows_couplings/ George H. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Coupling misaligned shafts
Tim Wescott wrote:
This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. How about directly coupling the unit to the shaft? If that isn't possible how about a sprocket and chain? The problem with any types of angles in the connection is that it will screw with your measurements. -- Steve W. |
Coupling misaligned shafts
On Tue, 08 Jul 2014 23:09:12 -0500, Tim Wescott
wrote: On Tue, 08 Jul 2014 22:38:27 -0400, clare wrote: On Tue, 08 Jul 2014 19:52:15 -0500, Tim Wescott wrote: On Tue, 08 Jul 2014 20:26:30 -0400, clare wrote: On Tue, 08 Jul 2014 15:50:31 -0500, Tim Wescott wrote: This is related to my dynamometer thread. We didn't find anything, so I'm working on plan B, which is to roll my own. The thing would need to work with an existing piece of equipment, which has no solid external reference points to provide for good alignment to the shaft on the device under test (or, for that matter, a really easy way to get centered onto a shaft). I'm visualizing getting something that can locate things to within an inch, and within five or ten degrees, then having one of two things: 1: A foot-long shaft with U-joints (probably CV) at each end, to couple the dynamometer to the device under test, or 2: A much shorter mechanical gizmo, which is currently labeled in my mental sketches as the "magic coupler". The important thing in all of this blathering is that when all is said and done the coupling needs to transmit torque accurately -- it can't just be efficient, it has to not have any severe differential gearing effects that would mess up torque readings. So, do you think #1 would work? Is there a name for #2, and could I count on it, or should I just stick with #1? As suggested by my foot-long shaft idea, space is not a huge issue, particularly if the thing can be stowed away compactly when not in use. #2 is called a belt. Not if I can't easily mount it concentric to the axis of rotation. OK, spill the beans--- What is the application??? Picture or diagram, or at least a good description?? How about a hunk of hose the right size to fit the shaft, and a couple of hose clamps. Braided hose if required. Even steel braid. You are only talking 80RPM from what I remember - and what torque, again??? And I'm assuming you mean parallel to the axis of rotation. It's for a customer, so I have to be all secretive. Which is a pain, I know. Things could, in theory, be mounted dead center on a shaft on the device under test, but doing so would require some disassembly and reassembly to do the test. I'll go there if I must, but I'd much rather have something that'll work anywhere, anytime. 50 newton-meters, whatever that works out to in 'merican units. about 35 ft lbs., at 80 RPM that's only half a HP. I'd say just pull the motor and test it. Save you a lot of work in the long term. |
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