a rogue method?
JasonB | 21/08/2021 07:09:46 |
![]() 25215 forum posts 3105 photos 1 articles | Posted by brian jones 11 on 21/08/2021 06:57:11:
Rack and pinion or worm gear, both have been shown to work to an extent. But how are you cutting the rack with a tap? Unless very short. |
brian jones 11 | 21/08/2021 07:35:01 |
347 forum posts 62 photos | Well isnt the worm gear an endless rack? Get creative, how about a spiral rack Spur gear with round contour at edges, eg more tooth contact in the mesh I am envisaging herringbone gear set , ie two spurs, one reversed against the other - no backlash Waiting on mtl to start my modelling After all who would ever dream up a pair of oval gears https://www.radartutorial.eu/17.bauteile/bt08.en.html |
John Haine | 21/08/2021 11:21:01 |
5563 forum posts 322 photos | By herringbone, do you mean helical? Why would that eliminate backlash? |
Michael Gilligan | 21/08/2021 12:08:30 |
![]() 23121 forum posts 1360 photos | Posted by John Haine on 21/08/2021 11:21:01:
By herringbone, do you mean helical? . I had presumed that Brian meant what he wrote … but I could be wrong (it’s happened plenty of times before) MichaelG. . https://en.wikipedia.org/wiki/Herringbone_gear Edited By Michael Gilligan on 21/08/2021 12:09:51 |
brian jones 11 | 21/08/2021 12:12:22 |
347 forum posts 62 photos | Posted by John Haine on 21/08/2021 11:21:01:
By herringbone, do you mean helical? Why would that eliminate backlash? Sometimes I want to give up https://en.wikipedia.org/wiki/Herringbone_gear |
John Haine | 21/08/2021 12:56:07 |
5563 forum posts 322 photos | Yes, I know what they are thank you! It's just that though they have the great advantage of being quiet (as a derivative of a helical) and (unlike a helical) not creating a thrust force along the shaft axis, they do not have zero backlash. And making them is difficult. You could I suppose make two helical of opposite hands and mount on the same shaft, but how would you make those with a tap to mate with another similar pair? Or maybe you don't mean herringbone but just have two straight gears with some angular offset to take up the backlash. Whatever, I wait with interest to see the results. |
John P | 21/08/2021 13:13:22 |
451 forum posts 268 photos | Couple of videos for herringbone fans. Don't blink for the second one. https://www.youtube.com/watch?v=DFEN9_t150c John |
Martin Kyte | 21/08/2021 13:13:49 |
![]() 3445 forum posts 62 photos | The Anderton boat lift used 'herringbone' gears. Big ones. They were cast and then run in pairs in a sand bath to bed them in to my knowledge. regards Martin |
brian jones 11 | 21/08/2021 13:13:51 |
347 forum posts 62 photos | I have a cunning plan I am making up gear blanks using hard wax. I will set up a jig so i can rotate the tap by hand and closely observe what is happening I will also look at some 3d dynamic modelling s/w i used many years ago (my brian hurts already) Well it beats lock down dunnit |
JasonB | 21/08/2021 13:14:42 |
![]() 25215 forum posts 3105 photos 1 articles | Maybe he also has got a left hand tap |
brian jones 11 | 21/08/2021 13:15:57 |
347 forum posts 62 photos | Pay attention at the back Or maybe you don't mean herringbone but just have two straight gears with some angular offset to take up the backlash. |
Martin Kyte | 21/08/2021 13:16:04 |
![]() 3445 forum posts 62 photos | Posted by brian jones 11 on 21/08/2021 13:13:51:
Well it beats lock down dunnit Does someone want to tell him he can come out now :O) Martin |
brian jones 11 | 21/08/2021 13:27:05 |
347 forum posts 62 photos | Now I thought you could do something like that The Anderton boat lift used 'herringbone' gears. Big ones. They were cast and then run in pairs in a sand bath to bed them in to my knowledge. https://www.alamy.com/anderton-boat-lift-is-a-two-caisson-lift-lock-near-the-village-of-anderton-cheshire-in-north-west-england-image236836670.html that should keep the back seat modellers quiet for a while BTW have you all spotted the deliberate design error |
brian jones 11 | 21/08/2021 13:38:48 |
347 forum posts 62 photos | Posted by John P on 21/08/2021 13:13:22:
Couple of videos for herringbone fans. Don't blink for the second one. https://www.youtube.com/watch?v=DFEN9_t150c John see what you can do with a big enough tap https://www.youtube.com/watch?v=mtV8Zu5EtUE |
John P | 21/08/2021 14:02:59 |
451 forum posts 268 photos | The hand of the tap or hob would have no influence on the
John |
Martin Connelly | 21/08/2021 15:16:25 |
![]() 2549 forum posts 235 photos | I presume, Brian, that you are thinking along this line. However these are straight spur gears not helical or herringbone. The problem is that, as pointed out, for a herringbone effect you either need a matching left hand tap or else you need to have a large angular change in the relative position of the tap to the blank. Simply flipping a gear 180° will not change the angle of the teeth to give you a herringbone gear. The introduction of this angular relationship will change the tooth form produced quite substantially. Buy Anti-Backlash Spur Gears | Accu | 500,000+ Components | Accu® Martin C |
JasonB | 21/08/2021 16:27:40 |
![]() 25215 forum posts 3105 photos 1 articles | Thanks John P, a bit like screw cutting away from the chuck, something has to be reversed |
Martin Kyte | 21/08/2021 17:39:23 |
![]() 3445 forum posts 62 photos | OK say the tap/hob has a 6 degree helix angle. In order to cut a straight spur gear you angle the tap/hob at 6 degrees to the blank.( Or the blank to the tap/hob). If you increase the angle you get a helical gear of one hand and if you decrease it you get one of the opposite hand. regards Martin |
Martin Connelly | 21/08/2021 18:35:23 |
![]() 2549 forum posts 235 photos | Changing the angle of the tap changes the pitch produced so they may be of opposite hand but they will have different pitches. Martin C |
Martin Kyte | 21/08/2021 19:18:51 |
![]() 3445 forum posts 62 photos | No the pitch is set by the TPI of the tap. The approach angle of the cutting edge is set by the skew angle. regards Martin |
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