No, we've already been through the "Rob's Knob" discussion, let's not rehash that...

because the screws I have don't screw into the handle so they just float in the holes

Re-check his attached picture.

Tell us details about your custom rotary control

Oops, sorry, missed this one previously.

It's made of alumin(i)um stock, turned to a slight taper (sligthly wider at the base), slightly concave top. I made it as a proof of concept before talking to a friend about making one in stainless (my small lathe doesn't much like stainless...) The final one will have grabby nothes milled or ground into the circumference/edge of front surface - with this one I almost always have to grip it to turn it.

The one thing I don't like is the hole for the grub screw... Unsightly it is...
Anyone with any good ideas about other ways of securing the knob to the D-shaped axle? On this one there's a 6mm hole for the axle from the rear and a 2.5mm hole threaded to M3 from the side. When installing I make sure the grub screw goes against the flat of the 'D'.

/Michael

/Michael

"Anyone with any good ideas about other ways of securing the knob to the D-shaped axle?"

how about blue loctite

ways of securing the knob to the D-shaped axle

Didn't notice this when you posted initially. Are you saying that your unit has its knob attached to an axle that is not wholly cylindrical? That it has a flat face molded out of the curved surface, so that it's capital-D-shaped?

If so, my unit's not like that. I have a solid cylinder that the knob fits on. Maybe this was changed between Mk2 and Mk2a, as there was a problem with the original knobs slipping on the axle. I and (I assume) many others had to have new knobs shipped out. They fixed the problem by using a small rubbery O-ring in the new knob to grab the axle.

So either whoever needs to watch out and make sure that any newly fabricated knobs will fit on both axles, if there are two, or maybe the O-ring is your answer.

You're right. The MkIIa does have a flat on the shaft for just the reason you suggest. I'm not sure whether later MkIIs have it as well though. I got mine in October 2000 and mine doesn't have the flat. This is something I'll have to keep in mind if my custom Fascias, Buttons & Knobs ever get into production.

The interesting thing is that I just got the rotary on my Mk2 replaced (it wasn't working properly), and the new one is also fully cylindrical. While I suppose it's possible that they wanted to keep the ``correct'' thing on my Mk2, it might also be possible that it's more random than that.

Hmmm... very interesting...
Maybe they've got some of those left in stock which they want to get rid of first, or as you say they might just want to keep everything to original spec.

It's not random at all - the Mk.2 has a round shaft and the Mk.2A has a keyed shaft. The same components are used in servicing.

Rob

If you're finding it hard to access the screws for the display board, there always another solution available. YMMV of course.


Bruno

how about blue loctite

Hmmmm, the fit isn't very tight to begin with (empeg guys, is the axle spec'ed as x.y mm or 1/x inch?) with a 6 mm hole, and 5.5 was too small. How hard does blue loctite get - it might be a case of too loose a fit to make loctite work unless it hardens fully. And I would prefer to be able to remove the knob without destroying the rotary encoder...

I've been toying with the idea of making a small spring, shaped like a 'b' but with taller vertical top and without the lower part of the vertical. The vertical part would press-fit into a radially milled recess at the back of the knob and the bent part would occupy the space of the 'missing' part of the axle, inside the hole. See attachment. Spring is dark blue, D-shaped part of axle is red.

Comments?

/Michael

I believe blue is the removable kind I don't know how hard it would be to remove from an application like this. I use it on screws in rc cars to keep them from vibrating out but they are still removable. red is almost impossible to remove. they have several different kinds if you look at a loctite package they have them all listed

how about blue loctite

Very dangerous. If the knob is attached to the shaft too securely, you will break the fill nipple on the VFD when you try to remove the knob.

There is an empeg owner in Menlo Park, California who can personally attest to this. :-(

tanstaafl.

thats why I suggested the blue it's not supposed to be permanant. but your probably right anyway

can you put the grub screw back far enough so it is covered by the face panel

How would you then get at it?

is it possible to make a keyway? have a hole the size of the shaft and an overlapping (pref square) for a square section key to slot into.

have a hole the size of the shaft and an overlapping (pref square) for a square section key to slot into

Could you sketch that? I can't visualize it...

As to putting the grub screw further back: could be done, but would require drilling a small hole through the fascia, probably from below, so that you could get the allen wrench in to the grub screw.

/Michael

Not being near a good computer for a little while, I'll try to invoke yur imagination.

Imagine a round hole. now imagine a smaller square hole as well but slightly off-set to the round one. The spindel sits in the round hole and the 'key' (square section rod) sits on the flat of the spindle and into the square hole. The problem is getting the tolerances right and a key the right size. But hey, if you're manufacturing stuff anyway....

put on the knob and then the face

I'll try to invoke yur imagination

Ah, OK, I think I get it... See attached pic. Getting the tolerances correct for a fit that would be able to be hand assenbled and disassembled without hurting the rotary encoder or other components is, I fear, out of my league...

So I'd still need a way to make sure the knob doesn't fall off the axle...
Then I think I might as well just make a section replacing the cut away material of the D section so that the axle is round again (attached with superglue or some sort of permanent LocTite) and go at it with a groove for an O-ring in the knob hole. That we'd probably be able to make work w/o too much trouble, as we're both used to working on/with paintball gear.

/Michael

> put on the knob and then the face

Except that the colour/color panel should be put on first as the knob's hole is too small to allow the head of the knob through.

Man, people are making a huge deal out of something so easy to fix/hide. Unless I'm missing something very subtle that differs in the way this new knob is supposed to work.

The fascia currently fits over the knob. It currently covers up a portion of the knob. Put a hole for a set screw as far back and as small as possible so it is completely hidden when the fascia is put on.

What else would work... A small piece of rubber placed on the flat part of the stalk creating a firm grip when the knob is attached. Likewise, a small flat piece of metal, no wider than the diameter of the stalk, bent into a V shape and placed with one of its sides attached to the stalk (open end toward empeg). Then slide the knob on for a firm fit (if the V piece was made properly - you could also slot a little into the back of the knob after it's been turned (on the lathe, not by hand on the stalk :)

There are also other ways of making the knob - in multiple pieces for instance. Though it would be a little more work to have it all fit together nicely.

Oh, and there's always looking at other metal knobs out there on other products to see how they do it. :)

Bruno

I see two problems. One is how to get the knob to attach to the keyed shaft. The second is how to get it to also attach to the non-keyed shaft.

I don't know how the current knob is attached to the keyed shaft, but it's attached to the non-keyed shaft by means of an O-ring, as I've mentioned before. More specifically, one puts this O-ring into the knob, where it just barely fits. There is a shelf inside the knob's hole on which it rests, but the shaft extends past it into a smaller hole that keeps it level, while the O-ring is sized just right so that it presses against both the knob and shaft, keeping it from moving in and out without significant effort. I don't see why the same system can't be used for the new knob. You'd need to make sure the shelf was rounded so that the shaft wouldn't catch on it when applying the knob, but little beyond that need be changed from the plastic version.

I haven't seen a keyed shaft, but I assume that it's not keyed along its entire length. There ought to be a point at which it becomes a solid cylinder again. So why not make a patch to fill out the key so that it becomes a full cylinder again? It could conceivably be made out of aluminum as well, but it might make more sense to make it out of hard rubber or plastic instead. It might be a little tricky holding the patch while pushing the knob on, but, once the knob's applied, the same pressure holding it on should hold the patch on as well.

This all assumes that the keyed shaft is of the same diameter as the non-keyed shaft, but an O-ring with a different internal diameter should be able to fix that problem as well. In addition, the O-rings and small patches should be cheap, at least in comparison to the knob itself.

...as the knob's hole is too small to allow the head of the knob through.

Couldn't you make the hole bigger?

tanstaafl.

is there enough material to put a decent thread for a grub screw?

Couldn't you make the hole bigger?

IIRC it's been mentioned that enlargeninig the hole might allow unwanted
noise (electric) to leak out. Don't know if that would be an issue if the knob is metal instead of plastic as the original. And I don't recall seeing many trouble reports from people using DarkStorms uncoated fascias (myself included, on the MkI)

And yes the front (but not the fascia) can go over the knob, so you can put the grub screw further back. [dopeslap] x 80
I'll make another grub screw hole in my prototype knob tomorrow and report back...

/Michael

is there enough material to put a decent thread for a grub screw?

It's not like you need something huge to provide enormous forces, and there's definately enough material for an M3 thread - slightly smaller than 1/8" (same as the allen head screws keeping the front and fascia on) Even in alumin(i)um there's no problem and stainless is far stronger.

/Michael