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🌞 New Stock Frame Design 🌞


#763

so going through things, 14.5 degree tilt will work with 32 inch kickers that will be touching the ground (and with the top tip of the kicker flush with the back of the legs)

adding 8 inches to the kickers will mean shortening the diagonals by 8 inches (or using an additional stick)


#764

I’m sorry to be so late on this. I’ve been trying to follow but I started too late. I’ll try to come up with some ideas to help out. What are the set parameters that have to be met? Total size, how far apart are the motors, how far do the motors need to be above the plywood, how far out. What is the required tilt of the front and back?


#765
  1. We want to cut 4x8 plywood

  2. We want to be able to fit through a door

  3. We want to be able to build it without a temporary frame

  4. We need to be able to work with the pre-purchased/cut 11’ lengths of chain, which limits the top beam to 10’ (a few inches wider than the first version). A 12’ top beam would have advantages, but it’s not clear how many people would want to use the wider frame, even if the chain length wasn’t an issue

  5. the motors should be ~18" above the work area, a little less is ok, but it means people building heavier sleds may run into problems.

  6. the question of tilt is not fully settled, 10 degrees and 15 degrees are in the ballpark, get too close to vertical and the sled has trouble driving the bit into the wood, too far from vertical and gravity provides too much friction and too little movement for the sled.

  7. the motors must be held very rigid with respect to each other.

  8. we are working with a 9" radius sled, so to cut t the bottom of the workpiece, you need room for the sled to remain clear of the floor (this current design gives you 10.5" here, not much, but we’re tight on top in being clear of doors)

beyond this, it needs to be simple to build, and hold itself (and the workpiece) up


#766

@madgrizzle don’t start coloring step 5, depending on what angle we want the machine, it will affect what parts we have available to use as spacers.


#767

minor change we could make.

we could eliminate the two lower blocks and put the kickers in their place (moving the spacer blocks from the top of the rear legs to the joint between the rear legs and the kickers, but we would now have to worry about getting those blocks at the right angles)

it is worth the effort to eliminate two blocks?


#768

here is the simplified version tilted back to 14.5 degrees (without the long diagonals) and the cutlist

This lowers the upper crossmember to make it so that the verticals and a long diagonal fit in an 8’ stick, but it also means that step 5 is now simple (take two short crossmembers, put them above the kicker, and then put the block for the upper crossmember above these boards)

I would not make this foldable, you want to anchor that lower crossmember solidly against the sides.

I see a way to make the front legs taller to support the bolted blocks approach.


#769

it should be just as easy to add the bracket as to add bolts, both are commonly available parts, nothing custom


#770

Oooo @dlang I see the inclusion of metric units - thank you that takes a load off my mind for my Maslow build.


#771

in all cases round to a convenient 5 or 10mm

the kickers, beam supports, and legs all want really good square ends, unless you have a miter saw, use the factory ends of the boards (they aren’t as good as a good, clean, fresh square cut, but they are far more likely to be square than anything you do with hand-held tools)


#772

Finally caught up =) Thanks for all the hard work and collaborative designing. I don’t have anything constructive to add that hasn’t already been mentioned so I’m just here to supply encouragement.


#773

David,

I love this summary Post! Great work.

Thank you


#774

I am liking this design a lot. Are we at a point where I should do a test build of the whole thing to give feedback on the build process?

What is the total screw count for the design as it stands?


#775

the full build (all optional wood pieces) looks like about 90 screws total (from a quick count)

leaving out the rear crosspiece and verticals would save 6

leaving out the top crossmember (and second set of diagonals) would save another 20 (I think having these makes it much easier to square up, as well as much stronger)

If you can wait until tomorrow, I can update my instructions and diagrams tonight. It till take more time that I can do at work.

which angle do you want, 10 degrees or 15 degrees? can you do a test today with your existing frame and see which you like better?


#776

@dlang I have concerns rounding will cause dimensional variations between builds. From experience a cut of 3048mm is easy to achieve with a tape measure. I do not recommend rounding metric values but instead mirror the proposed imperial dimensions.


#777

Yes, I can absolutely wait until tomorrow.

I vote we stick with 15 degrees unless we can find conclusive evidence that 10 is better.

I actually re-built my frame using all glue and screw joints yesterday to begin testing :grin:

I thought the glue and screw technique was a little harder to put together than with the bolts, but glue and screw required fewer tools (the bolts would require that everyone have an imperial socket set because we can’t get metric bolts in time).

My biggest concern was that rotating the top bar would make it weaker, and so I did some testing running the machine from the very bottom to the very top while filming the end of the beam next to a tape-measure. I didn’t see any overall flexing, but it is a little springy, while it was rock solid in the other orientation. My supports are 22 inches from the end of the beam, so reducing that to 12 should help significantly. Here’s a video of the end of the beam sped up 15x to make the movements more obvious:


#778

Based on my extremely inaccurate method of staring at the video, I saw maybe 1/32 of an inch of deflection there. Not very much. It would be interesting to see if moving the legs closer to the motor arms helps at all though!


#779

Perhaps a highly complicated supporting gusset is in order here to help prevent the frame from bending?


#780

I did enjoy watching the video.


#781

Giving the angles involved here I can’t think of a simple way to make that out of wood. You could likely get some strength by taking some lumber and adding a support on the back 90* out. If it’s really needed then it might be a good place for a turnbuckle but it wouldn’t be as cheap.


#782

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