Alas, I don’t think that’s an option, at least not in and of itself. His belts are still on top of the table, which in my case would mean, on top of my superstrut. The opening for the superstrut is facing outward to the side, and so the placement I’m pondering is to keep the stepper motor in the same orientation, but move it outward and downward. It may or may not be a “feasible” thing, but I’m just exploring it in the hope I can find an approach that not too “un-elegant.”
Hmm, and here I thought I cracked the code. 
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OK, so here is what I am planning at this point. This involves a cut MDF plate (a secondary Y plate) that is spaced off from, yet also attached to, an existing, stock YZ plate, using spacers (or perhaps coupler nuts), and to that secondary Y plate, a custom new remix of the original LR3 Y mount will be inserted, positioning both the endstop switch and the long belt in a new position, with the belt being hidden and protected inside the super strut.
In my desire to keep the placement tight, due to a necessity, the new Y mount does need a little bit of supports during printing. I am using support blockers to minimize the amount of supports. It’s adding only a very few minutes extra print time.
Four of the existing screw holes on the stock YZ plate will be used as anchor points to attach the new secondary plate.
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Curious to see how this turns out. Thanks for sharing your thinking and journey @DougJoseph.
Is it worth using this opportunity to also reduce impact of belt slack? Would be especially helpful for longer table lengths. Previously seen one piece of belt glued to a substrate, then another belt piece fastened such that it mostly meshes with the fixed belt, except for the small portion of idler tensioned belt that wraps around teethed pulley driven by (typically) y-axis steppers?
Good luck!
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Hey, I’m trying to grasp what you are saying.
My design has belt tensioner adjustment on both ends of the long belt. By turning a screw on either end, the belt’s tension would be adjusted.
Is this what you are referring to? If not, can you explain a bit more?
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Sure thing, check out 3 Tube Gantry LR3 Build: An Idiots Tale - #39 by azab2c
Looks like some folks (@claytonisbob, @tgm022861, maybe others?) experimented with using a glued/adhered ‘fixed belt’ for the tensioned belt to be meshed with. Goal being to reduce effect of belt slack, especially for longer belt runs. No idea what difference this’ll make to performance? Was considering positioning belt teeth facing/oriented same as today, somehow housing/protecting using cheap shallow L or C channel profiles available from big box store, but honestly haven’t spent much time thinking through this one.
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My machine has one 6’ belt (X-axis) and two 10’ belts (Y-axis).
If I move my spindle to the midpoint of the gantry I have even belt tension on both sides of the spindle. However, when I move the spindle to 1/4 the span of the gantry the tension on the longer belt length decreases while the tension on the shorter belt length increases.
The effect is more dramatic for moving the gantry along the Y-axis.
By capturing the belt in a rail the tension remains even across the full length.
My rail is not a length of belt adhered to something. The meshed profiles are not precise enough. My rail is like the teeth of a belt pulley arranged in a linear fashion for a precise fit.
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So, the images / plan I showed above, are for the “near side” long belt, (Y for most LR3’s), but I’m also looking into a plan for the far side as well (the side with the conduit guide).
I just took a look at my far side arrangement, and it’s going to be (arguably) easier on that side, or at least more direct. A modified YZ plate and modified mount could do it, strongly, with no need of a secondary plate like on the near side.
I‘d fear that the whole construction was going to be ripped apart when one driver fails or skeps are skipped and the gantry twists. Now it does not matter much, but if the parts are constrained, they could snap, couldn‘t they?
I’m going to be making this mod pretty rigid. I suppose anything is possible, but I’m expecting no issues.
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I should mention, I did not have any 1/2" MDF, only some 3/4", and so I decided to make the secondary Y plate out of 1/2" plywood (the hard strong stuff).
Doug,
I love the idea as it means the Y steppers and belts are not removed from the rail.
What we do need is a quick-release from the Y-Z plate and a way to make sure the Y steppers don’t fall off the rail when they are disconnected from the Y-Z plate.
You do fantastic designs; I hope you can make this work!! I want to put it on my LR3, which already has a set of rails with your parts. One of the concerns I have is ensuring the Y belts/stops are not changed much when I remove the machine from the work surface.
Mike
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My current concept for its quick disconnect is perhaps not what you are thinking of. This current plan would have a secondary Y plate with the Y drive mount and it would be rigidly attached to the main YZ plate. To disconnect, which I would very seldom need to do, loosen the tensioner screw, pop the belt out of the tensioner (near end, Y-min, presumably) and slide the gantry out by sliding the new Y drive out of the end of the superstrut. That’s a little more involved than the current plan, but I would prefer it. With the belt hidden away and protected, I would almost never need to disconnect it.
If I’m successful, probably you are someone will take it to the next level in ways I’m not thinking of yet.
Well, I’ll be moving the rails fore and aft on the sides of the worktable and would like them to always be keyed to the stop blocks. I have plans to put alignment pins into the sides of the worktable to resister the rails when I do change their position.
Mike
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Some additional bits of info on this as I’ve worked through it.
New Y Drive orientation - direction change
Since the Y motor gets rotated so it’s facing the opposite direction, its wiring had to be reversed where it connects to the mainboard (in my case an SKR Pro 1.2), or else it would be moving in the wrong direction. Easy change.
New Y Drive Motor Mount
This image with labels, shows info on my new remix of the Y drive motor mount, revised so its “business end” is only approximately 20 mm tall, including any protruding hardware, which is crucial because my superstrut’s slot opening is only 21 mm tall.
This pic shows that the M5 x 20mm tapered bore screws do not protrude. No extra stick out was key.
This is another view of the “business end” of my new remix of the Y drive motor mount, showing that the tapered head screws are almost flush due to the counter bore allowance of the holes in the design. The part’s height here is crucial.
Stand-offs: switched to printed (sourcing issue workaround)
I could not seem to source coupling nuts (hex bar) at the right length and thread size, so I designed printed standoffs that have nut capture slots for M5 nylock nuts, and used two nuts and two M5 screws per stand-off (coming from “outside” on both sides) to secure the secondary Y plate to the stock YZ plate. They are oriented for printing so that maximum strength is in the direction where it’s needed.
This view is while the LowRider is “flipped over” somewhat, looking at the bottom of it so to speak. All the standoffs are installed on stock YZ plate, and the secondary Y plate is installed onto them. There are four of them.
Making use of zip tie port on new Y drive motor mount.
As of now I have the system setup and working. I’m tweaking the belt tension system so it’s homing end stop is located square to the other side, which is not being modified in this way, as I only need the belt out of the way on this loading side of the table, and doing this mod on both Y sides would mean the gantry could only be removed and reinstalled by “sliding” it out of the ends of the superstruts. As it is I can insert the mod’d side into the superstrut and then lower the other onto the Y rail.
More soon.
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Nice work and well thought out.
I think it would be a great mod for the people that have to load from the side, like you said.
Love to see a video of the finished product or mostly finished product…
I really need to up my CAD game after looking at this. SIGH.
Also that table design in the cad models looks remarkably like a Palk table…
I’m pleased to say it’s working great, and I’m working on some video footage to illustrate.
Yep, I used the Paulk workbench torsion box as my inspiration, and designed and made two long torsion boxes, as well as a sturdy rolling cart base, and that’s what I use for my big router-based LR3.
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I decided to create an “adjustable endstop” version of the end cap-tensioner set for this mod.
Getting “square” can always be done with Marlin M666, but this allows a tangible, old school physical correction path as well. Also, whereas Marlin M666 can only adjust in one direction so to speak (inward from the farthest out end stop), thus “losing” the travel distance needed for the correction, this physical method allows adjusting outward (if the adjustable side is too far in) thus “gaining” the travel distance instead of losing it.
It’s designed to use two M3 screws, washers, and nylock nuts, to allow the end stop “slider” to be adjusted.
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Doug this is fantastic.
I’ve started to work on an LR2 to LR3 upgrade and one of the things I was concerned about was losing that extra workbench the LR2 provided. Just thinking about the change made me aware of how much I use it.
Your solution looks perfect and it resolves a small issue I had with the exposed belt design: every visitor to my workroom has had to hear me say “Oh, uh, don’t lean on those please”
Thanks for doing this and sharing your knowledge!
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