Combined FWD/REV switch plus potentiometer for mill power feed.

Hi Ed

Do a build thread. (please)

Draw up a spec before you start to build, you've not mentioned a feed override button, wish I had one.

I went the route Emgee mentioned. (switch points in direction of travel).

The no vault switch can be made with a double pole relay, when it powers up a set of contacts keep the relay energised. When power is lost the relay drops out.

Have fun!

Cheers Mike.

.

Good solution but on the Align there is no panel or support bush, the bit behind the knob is the two way lever which causes all the problems.

If you use an O ring in that application the pot just revolves either way with the lever. You have to leave an air gap but this alone won't cure the problem because of interference between the hollow lever shaft and the pot shaft.

Neither the lever or the pot can be removed without a complete strip down as the motor is to the rear of the pot / lever centreline.

The issues with the Align system clearly show how difficult it can be to stop mutual interference between concentric adjusters in a simple, affordable, device. Even for the pros. I have seen a pressure pad applied to the exposed back end of a potentiometer shaft to induce some drag to stop self adjustment under vibration. Better than nowt but not a lot. Higher quality potentiometers tend not to have exposed shaft ends which limits the applications. Suppose you could always start with a two gang potentiometer and break off the rear one to find some shaft to get hold of. Which is getting well into silly side of desperate.

As mentioned previously I gave up on a concentric system because I couldn't figure a neat, effective way of putting position detents in. Welp, 20 years too late, I think I have it. Strap a pair of long lever roller microswitches like this :- **LINK** or this :- **LINK** together with the rollers projecting through the panel. Put a pair of concentric face cams with switch on and detent recesses on the back of the lever boss. Switch on recess needs to be so deep that the roller is clear of the lever boss. Detent recess much shallower so that the microswitch button is held at full travel and bending of the lever beam produces a spring action to hold the location. Both cams have a detent for centre off position. Switch on recess on one cam matches a detent recess on the other. When moving between positions the "cams" are at full height bending the lever beams even further ensuring the switches remain off.

Or if you like nice engineering you could be inspired by this :-  http://uk.rs-online.com/web/p/microswitches/4183294/  where the plunger operates the switch via a relatively long travel spring.

Clive.

Edited By Clive Foster on 08/03/2017 14:01:05

Clickable link added.

Edited By John Stevenson on 08/03/2017 22:44:59

Hi Mike, I'll see what I can do re: a write-up. It would be nice to have a fast traverse and I think there's a way to switch between regulated voltage and full voltage, probably just a two-way selector is needed.

The wiper motor arrived today so I might pop out and check how it offers up to the machine later. Testing with just a 12V supply it seems to have quite a bit of torque.

For the hollow switch shaft, I was having ideas last night about a lever on the front panel with a short shaft passing through a bush mounted in the panel, very basic. At the back of the panel would be a machined cam plate interacting with micro switches, also mounted directly behind the panel, so all very flat in concept and sandwiching the front panel.

For the potentiometer, I could mount it on some sort of yolk framework behind the cam assembly. It's shaft could pass through the switch shaft with an air gap between the two and any interference/friction could be kept minimal by having a bearing between the two shafts at the front end, probably a flanged bearing. This would be the only point where the two shafts physically touch.

Cheers for now,
Ed.

Ed, methinks you are on the right track with the physical stuff, the fast traverse can be achieved electronically with a normally open switch ....to which you already eluded...need help,with it? Shout up.

Thank you John, very much appreciated.

Ed.

Ed

Considered a number of layouts in my efforts and would not use a yoke to mount the potentiometer. Simply screw through the panel into a relatively large diameter bushing and run the direction selector lever on that. Large bush isolates the pot knob from the lever and gives you somewhere to put an O ring for drag if need be.

Switches go outside the potentiometer so its all pretty flat. Shallowest form is to lay the micro switches flat on the front with the switch operating operating / detent notches directly on the outside of the lever boss instead of using a separate cam. Put a slot at the bottom of the cover to accommodate the direction lever swing, ± 20° should be more than adequate. Big advantage of that layout is it gives a nice surface for speed calibration dial. Direction lever and switch pack should come out rather under half inch deep depending on how thick you make the cover.

Clive.