Custom main tabletop?

[rayjack]

I must be honest. I was going to post a sarcastic reply to this thread, along the lines of "do you guys ever actually get time to make something on your SS" , but then I looked at the PDF drawings and spotted the brilliant under-table dust collector system, and now I'm all fired up with enthusiasm because my main complaint with my 510 is the amount of deposited and airborne dust which is not collected by the inbuilt system. I have amended the upper guard, inserting a takeoff tube for a secondary exhaust, but there is still a lot of extraneous dust. I'm off now to experiment. Perhaps after that I'll have time to make another rocking horse!:)

Ray

[riot_nrrd]

Something like this would probably work - you'll still need to space the eyelets on the table so that they are equidistant from the center of balance - otherwise, the table will lift from from the lower-weight corner first.

Another thought (unrelated to the hoist) - you may want to add some additional outside supports between the table and the floor. I'm going to guess adding this table will make the Shopsmith somewhat top-heavy, and given its size, it may act as a lever and cause the whole thing to flip over if you put too much pressure on the outfeed. If you have a roller stand or two, you could probalby just set them up under the table to keep that from happening.

RiotNrrd

[wood4fun]

Thanks for the pic riot_nrrd!

Something like this would probably work - you'll still need to space the eyelets on the table so that they are equidistant from the center of balance - otherwise, the table will lift from from the lower-weight corner first.

Now I see what you mean. It's simple (just one rope) but gets 2-to-1 leverage and lets the table hang where it wants to without wanting to twist or rock (thus the point about eyelet location vs. center of mass).

Another thought (unrelated to the hoist) - you may want to add some additional outside supports between the table and the floor. I'm going to guess adding this table will make the Shopsmith somewhat top-heavy, and given its size, it may act as a lever and cause the whole thing to flip over if you put too much pressure on the outfeed. If you have a roller stand or two, you could probalby just set them up under the table to keep that from happening.

This is the much debated issue about outfeed affecting Shopsmith stability and how to get stability without needing to adjust every time you change table height slightly. People have suggested adjustable legs on the outfeed, as you have, or adding weight low on the Shopsmith itself (e.g., sandbags down near the casters to increase stability.

The custom table will raise the center of mass, and throw it back a bit, but the majority of its weight is within the Mark V footprint or symmetrically in front & back of the Shopsmith driveshaft axis. The bottom layer of plywood is routed out wherever there's not much strength needed -- like lightening holes -- so the outfeed hinterlands only have lower-layer wood around the miter channels. (See attached drawing)

Since the incra miter channels are 1/2" high, the lower layer is needed below them, and to the sides a bit, to provide structural continuity to the table. Incra sells, as part of their "Build It" kit, their "Build It Slots" which are like a T-track but provide metal beneath them (as a lower layer) to structurally connect the top-layer panels. If they made a similar miter channel that would probably be a better option than the miter channels with wood beneath them, since they have a metal lower layer that's thinner than wood of comparable strength. Anyone have any experience on building with these? Is there a way to use their Build It Slots as a miter channel for their Miter Sliders?

Has anyone tried adding weight to the Shopsmith to increase stability backward? Any lessons learned? Based on the physics of it, it would seem that the more weight, and the lower you put it, the better. Also, since the outfeed is 2x the infeed, it would make sense to put the weight toward the front -- e.g., over the front casters. Any first-hand experience out there? I think I'll clamp a 2x4 to my 500 table, 2' extending beyond the blade in outfeed and 1' in infeed, and see how much weight it takes to lift the front or back casters off the ground.

-w4f

[wood4fun]

riot_nrrd,

I'm going to guess adding this table will make the Shopsmith somewhat top-heavy, and given its size, it may act as a lever and cause the whole thing to flip over if you put too much pressure on the outfeed.

I just did a simple experiment to test the stability. Here are the results. I clamped a 4' board to the extension table at about the right height, extending back 36" from the Shopsmith centerline (driveshaft axis). I was able to place 50 lbs. of weight (10 lb plates) centered on the 30"-behind-centerline point, which would be the table's outfeed (back) edge, before the Shopsmith was at the brink of toppling.

Then I put 40 lbs in a 5-gallon plastic bucket and suspended it from the front lower way tube. With that weight adding further stability, I was able to reach 70 lbs out on the outfeed edge.

I don't think I've ever worked with any piece of wood that weighed 20 lbs, other than maybe a full sheet of thick plywood, so even if I had a 20 lb board, and it was 8' long, and it was being ripped and just leaving the outfeed side of the blade, I think that should be roughly equivalent to a 40 lb concentrated load on the outfeed edge.

So, if my math is right, I think it should be safe from toppling the way I'd use it (your mileage may vary). I also plan to mount a couple of sandbags inside the Shopsmith gray "legs," along the front edge, just high enough over the caster foot-pedals to be out of the way. That should add some design margin.

Something like this would probably work - you'll still need to space the eyelets on the table so that they are equidistant from the center of balance - otherwise, the table will lift from from the lower-weight corner first.

I gave a little more thought to the "wooden-block hands" for mounting and dismounting the table. There's an attached pdf that shows a design for the wooden block hands. The green profile shown is a side view, showing how it engages the plywood Custom Table. I'd imagine making 2 of them out of 3/4" plywood, and attaching them to the shop wall 4" inside the left and right corners of the outfeed edge. I intend to mount a chunky knob just below each outfeed corner, to keep the Custom Table from slipping off the hands left/right. The attached pdf has 2 diagrams that illustrate the proposed design of the hands and the knobs, and how the hands engage the table and the knobs during mounting/dismounting the table.

So, does the math look right? Does it seem safe from toppling based on the experimental data? Do the hands & knobs look like a reasonable design? Is there a simpler design that would work just as well?

Thanks,
-w4f

[wood4fun]

I must be honest. I was going to post a sarcastic reply to this thread, along the lines of "do you guys ever actually get time to make something on your SS" , but then I looked at the PDF drawings and spotted the brilliant under-table dust collector system, and now I'm all fired up with enthusiasm because my main complaint with my 510 is the amount of deposited and airborne dust which is not collected by the inbuilt system. I have amended the upper guard, inserting a takeoff tube for a secondary exhaust, but there is still a lot of extraneous dust. I'm off now to experiment. Perhaps after that I'll have time to make another rocking horse!:)

Ray

Ray,
Thanks, I'm glad you think the dust-collection approach might work and might help you. My 500 doesn't collect much of the dust, and its lower saw guard is too small for the 12" disc sander.

My intent with this design was that the zero-clearance saw-blade slots together with a tight simple box-in-box design and a 2.5" shop-vac hose connector would get a lot more of the fine dust at the point it's generated. Since this Custom Table doesn't have to tilt, I don't have to get around the trunion, or make the top box pivot, so it's a lot simper design challenge than the Shopsmith designers have had to battle. Actually, the dust collection for this Custom Table only has to deal with attachment to the underside of the table and accomodation of the drive shaft, as the table is moved up/down.

So, I'm intending to use those inexpensive ceramic disc magnets embedded in the top surface of the inner box-in-box, and probably in the lips supporting the zero-clearance inserts for the 2 saw slots. A flat sheet metal frame attached to the bottom of the supporting lip might also work.

I've also tried to include the disc sander in the dust-collection strategy, so the box-in-box and the table-saw zero-clearance slots are both big enough for the 12" disc. One operation that people do with the disc sander that won't work with the zero-clearance slots is advancing the quill toward the workpiece to sand it and then back off. I suppose I could use an insert that's more like a dado-insert, with a wide long gap, though that would make the dust-collection less effective since the wider gap will decrease the local velocity of the dust-collecting air. It's a trade off. Maybe I could use the rip-fence miter channel and make a trivial disc-sanding sled that's just a board with a miter slider beneath it, and a hold-down clamp, so that sled would advance toward and back away easily from the sanding disc.

Would this be a reasonable way to collect dust from the saw blade and the sander? Do I need to move the shop-vac port to the out-feed face of the outer box, so the saw blade or disc sander shovel the dust right into the port? (would that work better?)

And no, for the time being, I'm spending a lot more time on my computer than on my Shopsmith:o , but I'd rather design several times and order parts once, rather than build a $200 table and then think of all the design changes that would have made it a lot more useful, safe, convenient, etc., or worse yet, find some major gotcha that makes the design a non-starter. So, for now, my shop is uncharacteristically dust/chip free.

Hopefully, we'll get the kinks out of this table design, get the parts, build it and get back to making real things!

Thanks,
-w4f

[riot_nrrd]

The "hands" sound like a great idea. You know, instead of building them, I think you could just use off-the-shelf ladder hangers (basically, a large heavy-gauge L bracket with a slight lip on the end). Bolt them to the studs like you would for a long extension ladder, and they shold work just fine.

As far as checking your math, unfortunately, math is not my forte - so I don't have a good way to do that. But some thoughts:

1.) It sounds like your experiment did not account for the wieght of the table itself. You may want to get an estimate of how much the tabletop itself will weigh.

2.) Rather than adding weight to the Shopsmith - you might consider adding stabilizers to the Shopsmith base? Not sure how often you move it around, but, maybe you could build some brackets with some t-nuts and some knobs, so you can add/remove them easily? So something like the attached.

RiotNrrd

[wood4fun]

RiotNrrd,

1.) It sounds like your experiment did not account for the wieght of the table itself. You may want to get an estimate of how much the tabletop itself will weigh.

Good point. I just did a quick analysis of the total weight of the Custom Table. According to this web site, a ball-park weight for a 4x8 sheet of 1/2" plywood should be about 46 lbs. Given the geometry of the Custom Table, it should therefore weigh roughly 37 lbs.

Also, given the table's geometry (the shape of its different top layer and bottom), its center of mass should be about 4" behind the Shopsmith's drive-shaft axis (within its footprint), so it should add to the stability of the Shopsmith. (until you start piling weight on it, outside of the Shopsmith's footprint, e.g., in the 2' deep outfeed area).

See the attached diagram of where the table's center of mass will be.

2.) Rather than adding weight to the Shopsmith - you might consider adding stabilizers to the Shopsmith base? Not sure how often you move it around, but, maybe you could build some brackets with some t-nuts and some knobs, so you can add/remove them easily? So something like the attached.

Thanks for the picture...I agree that expanding the footprint is better than adding weight. I'm not crazy about the front part of the bar (potential tripping hazard) but I do like the rear portion of the stabilizer bar. If that went out even one foot behind the Shopsmith, it would greatly enhance the Shopsmith's stability against toppling backward.

So how does the mechanism attach to the Shopsmith gray base? In your diagram, you have a knob, the stabilizer bar, then two blocks, with a captive T-nut. Is the rightmost block in your picture acting like a C-clamp gripping the Shopsmith base with a diagonal slot that the base fits in? Does the threaded rod form the c-clamp screw? Would that be a strong enough grip to withstand the torque on the stabilizer bar as the outfeed table gets loaded up? Would it need to have a hole thru the base's gray metal, or a dimple there to grab onto?

Thanks,
-w4f

[dusty]

riotnrrd and wood4fun,

What program(s) are you using to do your drawings?

[wood4fun]

What program(s) are you using to do your drawings?

Powerpoint. Excel for last pdf center of mass calc & picture.

[riot_nrrd]

PowerPoint here too. So no, nothing fancy or exceedingly cool. :-)

FYI, I use Visio often to do plans. Not the best tool, but better than PowerPoint. But I understand SketchUp is supposed to be pretty good... maybe I'll need to play with that.

RiotNrrd