Auto reverse mechanism

[Brian Rupnow]

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

[Gas_mantle]

Brian,

I used to be a collector of Meccano and some guys in that field of interest created allsorts of peculiar mechanisms, if you type 'Meccano mechanisms' in youtube you may find something of interest.

You'd be surprised what kind of interesting ideas you can get from trolling through some of the more ambitious Meccano models :-)

Peter

[Brian Rupnow]

Yes Peter, I have had a look at Meccano mechanisms, and although they are very clever, I haven't seen exactly what I'm after.---Brian

[John Hill]

Brian, I am confident you could make the double reverse thread with your mill provided you have a collection of gear wheels such as a lathe change wheel set and a means to mount your workpiece between centres horizontally on your mill table.  The job requires you to gear the work piece to rotate very slowly driven from your mill table feed.


Here is what I did..http://madmodder.net/index.php/topic,11137.msg129456.html#msg129456

As you can see I used a rotary table and chuck to hold the workpiece but I am sure there are other ways including two centres with a gear on the workpiece.

John

[Brian Rupnow]

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

[BillTodd]

These sorts of things?

[Brian Rupnow]

Yes Bill, that kind of thing. However, as I said in my initial post, I don't have cnc equipment, nor the ability to cut anything other than external spur gears.

[sbwhart]

Made something like that when I was an apprentice form memory it was a square form thread left and right hand so you ended up with a diamond shaped thread.

They also used a similar thing on the UK 30mm Rarden cannon to load the ammo the gunner fed a clip of ammo to the feed tray and wound a handle clock wise it fed the ammo across the tray picked the first round up fed it into the chamber and then the loader returned to the start position, again the screw had a left and right hand thread the left hand had courser pitch so that it returned quicker.

https://en.wikipedia.org/wiki/RARDEN

Stew

[BillTodd]

Yes Bill, that kind of thing. However, as I said in my initial post, I don't have cnc equipment, nor the ability to cut anything other than external spur gears.

that resersing gear could be fabricated from easily cut geared parts i.e. the semi circular ends coild bemade from half a spur gear the circular rack made with a rotary table (angled appropriately)  .if the tooth clearance is generous enough , it should mesh well enough for. demo.

the real one looks makeable
http://douglas-self.com/MUSEUM/POWER/gear/gear.htm

[Brian Rupnow]

I like this mechanism
<a href="https://www.youtube.com/watch?v=Bxtthb_6bO8" target="_blank">http://www.youtube.com/watch?v=Bxtthb_6bO8</a>

[ShopShoe]

Brian,

I think that one has the visually intersting appeal that you desire, particularly if the gears are easily visible to the observer.

ShopShoe

[Brian Rupnow]

Yes, I would have the gears visible. I can make the gears. I can buy a 20" long rack from McMaster Carr. I think I like this one, and reverse should be simplified by running the toggle into a fixed stop to shift it.

[Stuart]

Brian
You have been standing with that in front of you for quite a while ,
Apart from the rack its the banjo reverse on your lathe to reverse the lead screw

[Jasonb]

Brian
You have been standing with that in front of you for quite a while ,
Apart from the rack its the banjo reverse on your lathe to reverse the lead screw

not on our far eastern machines

[Stuart]

opps though Brian was from the USA and only used American iron 

but I did have a typo I meant to say tumbler reverse

but you live and learn as I use British iron its the norm for me