# Auto reverse mechanism



## Brian Rupnow (Aug 5, 2017)

I am getting a yen to machine something, but not an engine. I am somewhat intrigued by mechanisms that have an "automatic reverse" function to them. Not just a simple function like reversing gears, but more like something that moves along a short track, stops at the end of travel, then reverses movement and moves back to the original starting point and then repeats. The power source for this would be one of my many small engines. I have googled "reversing mechanisms" and there is a great array of articles posted about this. Of course, I want it to be something with a considerable "WOW" factor to it. I have the capacity to make spur gears here, but not internal gears nor funky gears like you see on a mangle.(Which is super neat.) The biggest problem I see to a mechanism like this is that when it gets to the "turnover" point, if it has to shift a lever to go into reverse it will probably just "hang up". The actual mechanism which moves something along can be a threaded rod with a threaded follower that reverses rotation, or a rack/pinion drive, even possibly a flat belt drive that shifts from a clockwise rotating pulley to a counter-clockwise rotating pulley. The big deal is that it has to do this without human intervention. I don't have the capacity to make a double reverse thread like you see on "level-wind" fishing reels. My tools are strictly limited to a manual lathe and a manual mill and a full set of 24 pitch gear cutters. I will have no problem designing whatever it is that I do, it's more the fact that I have to figure out exactly what I want to do. This is a wide open game, so if you have a good suggestion or a link to this type of mechanism working, by all means go ahead and tell me about it.---Brian


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## vidio1 (Aug 5, 2017)

http://507movements.com/

Maybe something in there will strike your fancy.


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## Brian Rupnow (Aug 5, 2017)

vidio1 said:


> http://507movements.com/
> 
> Maybe something in there will strike your fancy.


I have the paper version of that book, and I haven't seen anything in it that does what I want.--Brian


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## nautilus29 (Aug 5, 2017)

Would something like this be what your looking for?  If the pictures don't show you how it works I'll try to explain.


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## Brian Rupnow (Aug 5, 2017)

Nautilus29--I see that it is a double roller chain with a slider block attached to one of the links.--Tell me more please.


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## nautilus29 (Aug 5, 2017)

In the second picture down you can see that the slider block had a bearing bolted into the end of it.  You can see that the bearing is inside of a vertical slot of another block(I'll call this the arm).  In the first and 3rd pictures you can see that the arm is sitting freely on a shaft and able to move back and fourth on that shaft. 

So what is happening is the slot allows the bearing(attached to the slider block) to move up and down as it swings round the chain, but it does not allow side to side movement.  Let's say that the chain moves clockwise.  When the slider block is on the top of the chain it pulls the arm towards the front of the picture sliding on the shaft.  Then as the slider block rotates around the gear to the bottom of the chain the bearing is allowed to move down in the slot and then pull the arm back towards the top of the picture.  This action will happen over and over again with the chain only ever rotating in one direction, but the arm pivoting back and forth on the shaft as it follows the bearing. 

Let me know if I didn't explain it very well.  I can take more pictures if needed.


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## nautilus29 (Aug 5, 2017)

Front view of the arm.  As you can see there are 2 rails for it to slide along.


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## Brian Rupnow (Aug 6, 2017)

Nautilis--thank you. I can see now how that works.--Brian


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## Brian Rupnow (Aug 6, 2017)

This is a rough idea of how a spring loaded toggle would work. The tension spring will always try and make the toggle rest either as shown, or rotated to be against the other stop, with a small dead spot when the toggle is perfectly vertical between the two positions. Any force applied in direction A would make the toggle swing up to the dead spot (vertical) and then a bit more force will make it snap over to the second position. This "swing" of the toggle would have to be used to move a set of tumbler gears into position to reverse the mechanism. It's not a great drawing, but I think it shows what I'm thinking of.---Brian
http://imageshack.com/a/img923/3755/hu0oJO.jpg


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## canadianhorsepower (Aug 6, 2017)

Hi Brian 
this call and known as "an over center spring" every mechanical 
relays use this set up
cheers


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## TonyM (Aug 7, 2017)

A level wind mechanism like this http://www.amacoil.com/articles01.html uses a rolling ring on a plain shaft.


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## TonyM (Aug 7, 2017)

Here is an interesting one. 
http://www.douglas-self.com/MUSEUM/POWER/gear/gear.htm


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## TonyM (Aug 7, 2017)

There are a few ideas on this site  too.http://kmoddl.library.cornell.edu/model.php?m=589


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## Crisptrans (Aug 7, 2017)

Brian, How about a small friction drive transmission. Small roller driving a disc, depending on which side of the axle the drive tire is on controls direction. Wouldn't take much to shift back and forth and the amount of travel also adjusts your speed. Further from the axle= lower gear ratio.


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## Brian Rupnow (Aug 7, 2017)

I like this mechanism
[ame]https://www.youtube.com/watch?v=Bxtthb_6bO8[/ame]


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## Brian Rupnow (Aug 7, 2017)

Trying google photos
https://lh3.googleusercontent.com/9...Ic4KPpvYfoWa6y5xE5wN01oo_fkJE0=w1588-h1009-no


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## Brian Rupnow (Aug 7, 2017)

http://imageshack.com/a/img924/2116/rElEUl.jpg


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## Brian Rupnow (Aug 7, 2017)

This is what my gear cluster would look like, using gears that I can cut. 1.042" p.d. and 1.5" p.d. the rack can be purchased from McMaster Carr.
http://imageshack.com/a/img923/3594/in0cAs.jpg


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## Brian Rupnow (Aug 7, 2017)

Okay!!--I followed George's instructions, and it worked. The design isn't finished yet, but it's getting close. I would prefer to have the rack setting still and the pulley and gears moving back and forth, but that means I would require some kind of tensioning device on the drive to the large pulley.


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## bruedney (Aug 8, 2017)

Tried Brian's google post using IMG tags instead of URL ones

Nope that didn't work - how do you delete a post?

Bruce


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## Brian Rupnow (Aug 8, 2017)

This will be my travelling carriage. Three of the gears are the same, so they can all be cut at once, then parted off to length. The blue ball bearings attached to the carriage plate will run in grooves in the stationary rack support plate to give guidance and stability.


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## Brian Rupnow (Aug 8, 2017)

Here we have the full set up. The jackshaft at the bottom is centered between the two endplates, and the drive belt to the top pulley from the bottom is a 0.100" diameter rubber o-ring.  The jackshaft pulley is actually a double pulley, with the larger diameter hooked up to one of my engines via a second rubber o-ring which is not shown. As the moving gear cluster goes from right to left or vice-versa, the rubber drive belt stretches to accommodate it. The grey colored horizontal bar has a groove milled in each side to accommodate the blue roller bearings on each side of the "traveller" to keep everything aligned.


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## Brian Rupnow (Aug 11, 2017)

So, here we have the beginning of the old "cut three gears at once" trick. Outer diameter of gears and outer diameter of hubs have been turned, and reamed to 0.352" diameter center hole, all in the same set-up. (It was going to be a 5/16" center hole, but  discovered that I didn't have a 5/16" reamer at the very last minute, so I went up one size to 11/32" which I do have.) This method will let me cut the teeth on all 3 gears at once, then part them off in the lathe. Of course it also gives me the opportunity to screw up all three gears at the same time, so I'll try not to do that.


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## Brian Rupnow (Aug 13, 2017)

We have a finished and fully operational gear cluster. This didn't go quite as smoothly as I would have hoped. The chuck on my rotary table is attached with bolts in T slots, but no centering spigot. Sometimes, (I expect for sins I have committed in the distant past) the damned chuck moves a bit off center. It's not visible, but you can end up with slightly off-center gears. The pitch circle ends up being shifted very slightly from the bore. This of course results in gears that mesh very good on one side of their rotation, and are very very tight on the other side of their rotation. However, with a bit of fettling and cursing, everything now meshes very well, and I've done enough work for today.


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## Brian Rupnow (Aug 13, 2017)

Since I don't have room for a spring tension toggle device directly below the actuator arm because of the shaft running thru, then I will put a compression spring acting on it from above. This will serve as my toggle device.


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## Brian Rupnow (Aug 14, 2017)

After I got home from my "away office" this evening. I whittled out the "Pivot anchor plate". Got all of the holes drilled and reamed, and the profile roughed out. I will pick up the four ball bearings tomorrow.


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## Cogsy (Aug 15, 2017)

Just for a bit of reference for you Brian, I stumbled across a reversing mechanism the other day which was 2 straight gear racks facing each other, with a decent sized gear between them. The gear only had enough teeth around part of its circumference that it engaged with one rack at a time. As its rotation disengaged one rack it would engage with the other and thereby generate reverse motion. Probably only good for a relatively small back and forth oscillation or the gear diameter would get too large, but was interesting to see a simple continuous auto reverse that may come in handy one day.


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## TonyM (Aug 15, 2017)

That would also work with a small gear pivoting about its axis and moving from one rack to the other so the racks would not be governed by the size of the gear.


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## Brian Rupnow (Aug 16, 2017)

Today we have the four bearing mount shaft made and pressed into the aluminum backplate, with the bearings Loctited to the shafts. Why does one bearing have a blue grease seal while the other three are black? Beats me--Must be something to do with "diversity".


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## Brian Rupnow (Aug 18, 2017)

In the final phase of completing the gear cluster and "toggle" device, I decided it would be wise to make the compression of the toggle spring adjustable.


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## Brian Rupnow (Aug 18, 2017)

I've been a busy little beaver. The 6" diameter pulley is finished, and the toggle is finished. The toggle seems to work very well, and definitely will "kick" the gear mechanism down into position as soon as it is "over-centered" in either direction. Hopefully, tomorrow I will get the slotted track machined and attach the rack to it.---Brian


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## Brian Rupnow (Aug 19, 2017)

Today I have the first trial assembly of all the important pieces. Everything fits and clears properly, but I'm not getting enough "kick" from the toggle to shift things cleanly. I may mill some material away below the rack to let the rack set a little farther away from the gear cluster. This will allow for more movement when the gear cluster shifts position, and the toggle should have more movement so should be more effective.


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## Brian Rupnow (Aug 20, 2017)

Well, I'm finished enough to begin having doubts about whether it will work or not. It works when I turn the pulley by hand and use my other hand at the end of stroke to help flip the toggle over. However, as I expected, the problem is going to be getting that toggle to flip over nicely and consistently. I've spent enough of this weekend working to get it done to this stage. I will play with it in the coming week to see if I can get the toggle to work better.


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## Brian Rupnow (Aug 20, 2017)

After playing with this thing for an hour after supper, it has loosened up considerably. I have come to the conclusion that I need a stronger spring and more hysteresis in my toggle. I'm sure that a lot of you old guys could use a bit more "hysteresis in your toggle", but that's not what I'm talking about. I can buy a stronger spring sometime this week, and I think that if I lower the rack by milling away about 0.100" of material below the rack, that will increase the "hysteresis". (Let the toggle move more between full left and full right position.)


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## TonyM (Aug 21, 2017)

Hi Brian. 

I worked on chain driven self reversing mechanisms in my dim and distant past. The only problem they ever had was hang up at the point of changeover. There were usually two reasons for this. First caused by the driving gear disengaging before the toggle was fully over-centre. The second by the reverse gear engaging before the driving gear was fully disengaged. If this is not happening, then before you remove any material from below the rack, you may want to try lowering the strikers so that there is more movement of the toggle for less movement of the driving gear. It looks like you could clamp on some temporary strikers much lower down. The lower the better.


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## Brian Rupnow (Aug 23, 2017)

Thank you for the suggestion Tony. I'm kind of hung up on this mechanism at the moment, and I've been busy with other stuff. I just spent today driving 390 kilometers  to see my mother and take her a birthday cake and celebrate her 97th birthday. I will probably get back to this sometime in the next week or two.---Brian


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## bazmak (Aug 23, 2017)

Happy birthday to your Mum with many more


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## Brian Rupnow (Aug 23, 2017)

Thank you Baz. She has been a great mother. My wife and I and my mothers younger sister (who is eighty eight) had a little birthday party at the retirement home where she now lives. I thought that putting 97 candles on the birthday cake might have set off all the sprinklers, so we only put 7 candles on the cake. For many, many years when I was a boy, my mother had a pen pal named Ruby Walmsly in Australia. They corresponded for many years, and my mother was always happy to receive mail from her "Friend in Australia". When I was about 10 years old Mrs. Walmsly sent my mother a small wooden boomerang souvenir of Australia about 10" long to hang on the wall. It was quite pretty, and had a kangaroo painted on it. After seeing it hanging there for about 6 months, and reading about the "bushmen" of Australia, I sneaked it off the wall when my mother wasn't looking, took it outside, and threw it as hard as I could. I fully expected it to return to me.---But sadly, although I looked for it for weeks, it was never seen again. I always thought afterwards that the damned thing must have flown back to Australia. I had a lot of difficulty explaining this to my mother-----Brian


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## Cogsy (Aug 23, 2017)

And another Happy Birthday to your Mum from me as well.



Brian Rupnow said:


> But sadly, although I looked for it for weeks, it was never seen again.


 
This made me smile. There is certainly a knack to throwing a boomerang, and if you did it correctly (which you may have accidentally done) and if it was a properly built boomerang (not just a pretty bent stick) then it would likely have traced a figure 8 path in the air, with the cross-over point of the 8 right where you threw it from. In reality, the throw has to be absolutely perfect for this to happen but it wouldn't have taken much for the boomerang to have landed behind you - possibly explaining why you never found it...


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