🌞 New Stock Frame Design 🌞

[dlang]

@bar

Let’s move on from issue #3 for a minute and talk about issues #1 and #2

agreed

@bar

What are everyone’s ideas on how to do the lower arms that the bungee’s attach to? Is there a way to do it which also adds support to the plywood without causing an obstacle for the sled?

There are three choices with this

1. a bar in front of the legs that supports the workpiece/wasteboard/etc
2. a bar behind the legs that attaches the legs to each other, but provides no support for the workpiece/wasteboard/etc
3. a bar between the legs that supports things in the forward/backwards direction and can be flush with the bottom of the workpiece to allow fixed/sliding/rotating/removable tabs to be attached to it that will stick forward to support the workpiece/wasteboard/etc

The stock design was #1

The example I’ve been posting is #3

I think either one can work well, and there are advantages to each

the picture above is for #2

I don’t think it works well at all, You need something else to keep the plywood from warping, and it’s in the wrong place to support tabs

[madgrizzle]

The nice thing about the string is that if you bump it, it stays put. Not sure exactly what @blurfl you are describing, but it sounds like it just hangs… like a pendulum. I’d be worried that I’d keep bumping it.

[blurfl]

I looked at that, but the beam is several inches out in front of the workarea, so the cord would chafe against the top edge.

[dlang]

@gthiesfeld

Could the counterweights fall from the center of the top beam behind the Maslow? I don’t know if the angles work out, but it would be less cord to run.

I think it should be able to happen, the distance down to the bottom rail is about 5 ft, the distance from the motor to the center is about 5 ft

[dlang]

@blurfl

I looked at that, but the beam is several inches out in front of the workarea, so the cord would chafe against the top edge.

mount a short 2x4 in the center of the top beam and run the line back that way ???

[blurfl]

I’ve done this (though my chain still runs vertically), the weights hang below the motors which are back behind the bottom of the slanted workarea.

[blurfl]

@dlang

mount a short 2x4 in the center of the top beam and run the line back that way

Would need fairleads to lead the cord ‘around the bend’…

[dlang]

how much weight is needed? could we use fishing line and the associate guides?

[blurfl]

@dlang

how much weight is needed

I used 3 pound weights but a bit less (2?)would be better. Weights can be as simple as rocks in a sock. I tried fishing line but it is harder to work with. I settled on sash cord, about the same size as ‘stretchy string’ and easier to knot and hang on to when fussing with the chains.
Doing the calibration steps involves a lot of fussing with the chains, any new lashup should be put through all the measurement steps by multiple testers to evaluate how hard it is to handle the chain and keep it from kinking, bending or fouling. Fussing with chains happens more often than you imagine.

[dlang]

I was thinking that with only 4-5 ft of line in the top it would be easy to disconnect the hook from the chain and let the weight drop down to almost hit the ground it never goes slack and so never tangles

[gthiesfeld]

I’ve seen diy panel saws that use 2 liter bottles filled with water for counterweights. A full one liter bottle would be 2.2 lbs.

[rjon17469]

@bar

Here’s an outside the box idea…what if we don’t need lower arms?

We’ve got this beautiful new beam across the top, what if we used it instead? It keeps everything in plane and I think it’s tidier.

@dlang

So the chain comes off the outside bottom of the sprocket instead of the top inside?

That will change the math

This would change the math, but it’s not difficult to account for.

If this is something you guys want to pursue, I could modify the code to include a toggle switch for chains attaching to the sled from the top/bottom of the sprocket, and update the kinematics accordingly (at least for the triangular kinematics).

[dlang]

I think we do want to be able to change the chain wrap direction. It is such a cleanup.

Calibration will need to change to account for this as the initial motor measurement should still be across the top

[rjon17469]

There are several components of the calibration process as a whole that would need to be considered, as well as any implications for the quadrilateral kinematics. I can offer assistance, but don’t think I would be able to do the whole thing.

[dlang]

I would say ignore quad kinematics. Anyone modifying things enough to use this should be running triangular kinematics

[dlang]

I’m thinking that you do the chain measurements, then disconnect the chain and position the motors to straight up. Remount each chain the new way and feed it out (I would do half motor distance + wrap instead of a fixed amount) hook up the sled and finish the calibration

[dlang]

If we have the center crossmember in the right place, I’m very tempted to pull the kickers back so they can’t interfere and always have tabs/boards that stick out from the bottom of the crossmember.

It’s a slight extra step to mount them, but the result doesn’t have anything that will get in the way of the sled

[dlang]

@bar

Do other people have issues with the sled running into the bottom bar? If it’s just me I’m happy to go back to it and just modify mine

that thickness material and wasteboard do you commonly use?

[dlang]

circleing back to issue #3 (the top beam support)

here is the problem I’m worried about (exagerated to show the problem)

If the hole is not straight in the leg, it’s impossible to fix without replacing the leg
If the hole is not at exactly the correct height (in the leg or the top beam), you can’t adjust anything
The slop in the hole will let things sag, and tightening the bolt will not
straighten things out

it does keep the top beam (the front grey block) parallel to the wood.

with the crossed bars on the right, there is the possibility of tipping the top beam, but with the side and end of the wood being the factory cut ends, you can line them up pretty straight by putting a block of wood against the edge/end and making sure both pieces are solidly against it, and repeat on the other side.

you can apply glue, put a clamp across the two, and loosen the clamp just a bit to let you adjust them. Then tighten the clamp, check again, and then put a couple of screws through both to hold it while the glue dries and remove the clamp

If you do make a mistake, and don’t catch it until the glue dries, you can cut off the short horizontal part and try again with a new one (on the other side of the leg, but even stacked against the remains of an earlier try), you only loose a short piece of wood.

With the assembly process I define, everything (except the rear legs) is measured from the top of the front legs, using spacers so that it’s exactly repeatable from one side to the other (even if things are cut) unevenly

[Bee]

Technically you get 2 shots. You could flip the leg if you mess up the first time.

Just saying

Thank you