When testing the machine for the first time this weekend, I noticed that the sled would tilt toward vertical when the weights were below the bottom edge of the work surface. I understand that the CG of the sled is well below the point of support.
I simply stood up and kept my finger on the top of the sled to keep it in contact with the plywood. This was fine for my first cut, but got tiring after four hours of cutting. I need a more permanent solution. I’ve thought of adding an apron to the bottom and possibly the sides of the frame.
Does anyone else have a similar issue as this? How do others keep this from happening?
Yes, the top of the sled tilts away from the work surface and toward the user. Again, this is only at the bottom of the work surface when most of the sled is hanging off the plywood.
This is expected, the fix for this is to add something to the machine so that
the sled is supported.
this is the ‘skirt’ that you see people talking about.
what I think the best thing to do is to make a L-shaped piece the width of the
frame and put slots in it so that you can adjust it in and out to exactly match
the thickness of your workpiece + sacraficial board.
This can then support the sled so you can go to the bottom of the workpiece.
Yes!
This the temporary sled. Make the final one and if you hold your sled by the chains, you want it slightly tilted forward top to go parallel to the sheet. (my personal theory and backed by 1)
If your final sled will tilt backwards (towards you from the top) add spacers to bring the ring higher.
Thank you both, I do have plans to cut the final sled tonight. I have a partial sheet of plywood just for this purpose. I’ll post the “skirt” / “apron” idea I have in the community garden when I work it out.
umm, I think we are talking about different things. I think you are talking about the CG in the Z direction (the height of the mounting)
we are taking the CG in the XY plane, the bricks on the bottom of the sled mean that the CG is well below the bit, and when you run the sled off the bottom of the workpiece, the CG goes below the workpiece, and that causes the sled to tilt.
so the fix isn’t to mess with the chain mountings, but rather to add a skirt or other support for the sled so that it remains supported.
Just a crazy idea, but what about pouring a ring of concrete and mounting it to the sled. Calculate the ring so that it weighs the same as the two bricks. I have some concrete in airtight containers that I could try this weekend. Maybe embed a few carriage bolts for mounting or 1/2" PVC to use the carriage bolts that came in the kit.
I’d, of course, cut the forms with the Maslow just because I can.
correct, i’m off the path there.
To high mounts do create an increased tilt of the top sled towards the sheet at the top.
Les tilt at the bottom.
Triangular sleds should be balanced at the centre of the sheet to reduce top friction at the top and bottom friction down (tilts). Skirts can prevent tilts, yes.
We had that idea and tried and and found it was the wrong thing to do.
We found that you actually want the CG below the bit in the XY axis, otherwise
the motor torque will spin the sled until it hits a limit on the chains/mounts
and then twist a little more (impacting accuracy by making the chain no longer
pointing directly at the bit)
so whatever weight is needed should be on the bottom half of the sled like the
bricks are.
I did notice that the sled did try to always stay oriented the same direction. With the little friction between sled/plywood and the shop vac hose dragging, it stayed the same nearly all the time.
