Auto reverse mechanism

[Brian Rupnow]

Stuart--I am aware of the tumbler gears in a lathe, but I want my mechanism to be self reversing.

[Brian Rupnow]

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

[Brian Rupnow]

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

[Brian Rupnow]

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.

[steamboatmodel]

As a child a chum of mines dad had a small steam locomotive that ran on a straight length of track. there were three stations one at each end and one in the middle. the engine would slowdown then stop at the end stations, then reverse.  After every five trips down it would stop at the middle station, where he had a water tower that you could fill the tender. It was all steam powered and tripped by pegs set between the rails. We moved before I got old enough to really understand how it all worked.
Regards,
Gerald.

[Jasonb]

Brian, if you want the tumbler to move then you could use a belt wrapped round the tumbler shaft on a small pulley, a pulley at each end and one of those driven by your large pulley. There are several ways to wrap the belt and keep it in tension but below is the simple principal.

[Brian Rupnow]

Thank you Jason.

[zeeprogrammer]

Just popping in to say I'm watching. Looks to be interesting and I can see a lot of applications. 

[Brian Rupnow]

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.

[Brian Rupnow]

Hi Zee---Glad you're watching. I'm not sure if this is going to work or not, but it's interesting. The animation I posted looks good, but we all know that just because you can do something on a computer don't necessarily make it so.---Brian

[Brian Rupnow]

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.

[10KPete]

Interesting!! A very nice do nothing machine... I love it!

Oh, I think you'll find that the o-ring isn't stretchy enough for that application... ????

Pete

[Brian Rupnow]

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.

[Brian Rupnow]

Once again the machining Gods seem to have smiled on me. There are 25 spaces between the teeth on these gears. When I finally crank the rotary table around to that 26th position and don't hear any metal being cut, it gives me a great feeling of relief.

[Brian Rupnow]

I've reached my limit of fun for today. Three brass gears are finished, and the one larger gear I am making from 1018 steel. The blank is all finished, and tomorrow I will cut the teeth on it. And yes, I have decided that it needs a toggle to keep the teeth on the gears engaged with the rack. I will put some cad models of the toggle up tomorrow.