So the idea has come up more than once of reworking the v-wheels away from Delrin towards metal. There are several concerns:
~The available steel wheels have dimensions that vary from the Delrin wheel, which would require reworking the plate
~The steel wheels could potentially wear down the soft-anodized aluminum slide
~Brass alloy could be an excellent candidate, but is costly by comparison
Initially I came at the problem with the intent of duplicating the wheels that come with the kit. The pursuit was given up at, first, when I came up with the idea of a better replacement spacer. It's a definite improvement. However, the light on the horizon is finishing up a real, metal alternative to the supplied part in order to further firm up the entire build. With 16 points of contact, there is an undeniable improvement to be had. After some posts regarding the topic of the merits of the reworked spacers, the idea of metal wheels surfaced again. This time, something workable emerged.
A Fix
Trying to make the original wheel requires a multistep process on the ShapeOko, or some serious undercutting. A metal lathe would likely be the best option. Something else was needed for this to be a 2.5D part.
First there is the matter of the metal. With copper costing what it does, an aluminum that is similar to the composition of the slide seems a good choice.
Next is the matter of design. Instead of going extreme on the undercutting, I realized the whole idea of the sandwiching the wheel between the bearings could, itself, be reworked to make the wheel the bread. If we reuse the bearings they can be put right next to each other. The cream on top of my redesign, is both how and how well it keeps the bearings together.
The Details
By using two differing stock thicknesses, I've put together a solution. The mock ups are below. First, note that there are spurs on the inside of new wheels. These are slightly undersized and slightly inward sloping to create a secure fit from under to oversized bearings. The cut away material allows for slight deformation of the spurs which facilitates the snug fit.
The opening in thicker stock is actually deeper than the bearing itself. This allows one bearing to be completely sunk into that half of the wheel, and the remaining stock that extends above the bearing creates a space for the second bearing to register into. This creates a system that works to keep both bearings extremely aligned and centered with one another.
The shorter half is drilled though the edge and the taller half is drilled and tapped to allow #00 bolts to keep the halves together, clamping the bearings in between. The lip that retains the bearing closest to the plate should require no other changes to the setup. The design offsets the centerline of the "V" by only about a quarter millimeter, well within the allowance of the ShapeOko's plates.
Action
So the stock and the appropriate mill are on there way. Reusing the current bearings will ease cost. My design is very good, but will likely need some light tweaking as projects tend to. I expect to have things nailed down by the end of November. I'm really very excited about how this will play out and expect the results to be excellent. So who else would be interested?
As an FYI, here's the wheel that doesn't fit.
http://store.makerslide.com/index.php?m ... ucts_id=75
For your engineering pleasure:
Components

Components: Isometric

Assembly: Solid bearings, transparent wheels show bearings' hairline meeting one-half millimeter below the gap in the "V"

Assembly: Isometric with solid bearings and transparent wheels showing detail of the spurs

Glamor shot: showing the full assembly and the M5 socket screw head.

Concerns
Two things I have a care about. First, the four bolts holding things together will be #00-90 as mentioned. These are 1.19 mm in diameter for the major dimension. The minor is just under 1 mm. Four of these will be able to produce about 120 pounds of force between the two halves without worry about them deforming. I think that should be plenty, but additional bolts is a consideration. Fasteners with a larger diameter are out since they would interfere with the positive "V" that comprises the rail.
As for the inner lip nearest the plate. It should clear the plate, but a second washer may be needed if the current washer is undersized. This would move the centerline of the "V" out by about 3/4 of a millimeter--a change that should not be a problem for the supplied plates.
Please post your interest and thoughts below. I'm very interested to hear what people think about this solution.
Best,
EJ