Hi all! I was in the process of upgrading my Lowrider v2 with some stiffness upgrades when I now saw that v4 is out. Super exciting! I’d like to make the upgrade, but have some questions:
I saw that V4 now uses 1" EMT (so 1" ID and slightly bigger OD), as compared to v2 when we had to order 1" OD stainless steel tubes. If I keep the same tubing for the gantry I’m guessing I’ll need to modify the printed files accordingly, is this correct?
I happened to come upon some 4040 aluminum extrusion for cheap. Would it be worth it to replace my 1" OD stainless steel tubing (1/8" wall I believe) with this? Would it be more rigid? I’m comfortable modifying the files to run along the new square profile if necessary, but I’m unsure if it’s even an upgrade on stiffness or not.
Are there any other considerations I’ll need to make for the upgrade? (i.e. I know I’ll need a ton of new screws, nuts, and other similar hardware). Are the leadscrews compatible?
Congrats to Ryan on the V4 release, the machine looks better than ever!
Ryan’s an engineer, and I am not. So this is in the FWIW category.
Engineers such as Ryan seem to have a sense, and I think it’s warranted, that cylindrical shapes, or dome (half sphere) shapes, are stronger than a flat shape. It’s why large heavy architectural things and engineering things are often designed as either half-cylinder or half sphere. I could be wrong, but I think cylindrical tubing is stronger (more rigid) than a flat bar of the same thickness and same overall area.
Round tubes are roughly 25-30% lighter, if I remember correctly. This probably drives a lot of the “let’s use round tube” decisions in lots of things.
Generally speaking, I think round is better for short distances, square for longer distances
Everything is a tradeoff. Weight, Strength, durability, etc.
I would assume Ryan’s decision to use Round tube is a bit of a mixture of weight, durability, ease of sourcing affordable material, and ease of designing around the shape.
There are almost certainly better and/or stronger things that are reasonable, but not all of them can be found for $10 down the street at a local store.
Without checking, I would assume 4040 extrusion is as strong as EMT by itself.
But when you add in the entire assembly with the strut plates, I would guess you are not going to gain that much by redesigning it for 4040, and you have do a lot of design/test/design/test iterations to get it right on your own, perhaps in hopes of only a marginal gain, but at the risk of making it worse than the stock design.
Early on, I asked the same question: Is my 1" (25.4mm) OD stainless steel as rigid, less rigid, etc compared to normal steel at 1" EMT’s 29.5 mm OD. The replies I got from the engineering minds was that the larger plain steel EMT is more rigid than the smaller stainless steel. My understanding is that all other things being equal (ID and OD, i.e same size and same wall thickness, i.e. if the stainless steel were the same size as the EMT) the stainless would have an advantage. But not enough to make up for the size difference.
Here’s one idea for using your 1" OD stainless tubes: make a LowRider 3, and install a plasma torch on it. I made a plasma based LR3, and its driven by an old laptop running Linux CNC (with QTPlasmaC user interface).
Thanks for all the great replies and discussion! At the end of the day I think I’ll just go with the recommended 1" emt. As others said, it’s not spendy and any effort to redesign things around the other options may just make it worse.
This got me wondering, so I went in search of some deflection calculators for both materials. Can’t speak the the accuracy of either one, but oddly enough with a 56” span and a 10lb point load in the center, both materials calc’d out the the same .0421” of deflection.
The tubing and a single stick of extrusion appear comparable.
We don’t mill things with single sticks, though. Most extrusion based machines and fixtures use brackets or fasteners and you then have the question of the joint mechanical properties and also the build/assembly fixturing and assembly skill.
So it isn’t a given at all what wins.
As a silly contrast, consider a really well built LR4 using recommended materials against a shoddily built and loosely assembled extrusion machine. The LR4 would likely walk all over the crappily built machine.
Perfect vs perfect, then it gets more blurry and you have to ask what they cost, how they hold up, etc.
LowRiders are superbly optimized to provide exceptional milling capabilities using affordable, locally sourcable materials and leveraging a lot of the users’ skills and existing machines.
There’s nothing wrong with making a reinterpretation of the basic design using other framing systems- but it’s no given that it will be “better” depending on how you rate the various qualities of the machine, the build experience, and the community.
Well, I wasn’t trying to make any implications, but thanks. I was just trying to confirm that I understood the basic data point correctly.
Intuitively, there is a lot of empty space in the outer “skin” of extrusion, and that’s always seemed like a source of weakness to me. If course, it makes up for that in how easy it is to assemble a system vs 3d printed plastic connectors for tube.
Almost all the work is done in the skin, for mechanical loads and even in the electrical realm for wires. Beyond that, it’s just extra mass, and extra mass can hurt the system.
