Amphibious Tires - for 1.9" / 48mm Rims

I started this project as an addition for my XRP Offroad mod that can also be seen in the rendered picture to make it ready for the water and you're not limited to the XRP Boat Mod anymore. And in theory this would also work, but that brings me straight to the point. I couldn't test it because you need way more TPU than I imagined and sadly I currently don't own enough. :'D

But those Amphibious Tires will fit every RC default rim with the size of 1.9" / 48mm. So you're not limited to any of my models anyway. You can put them on any vehicle that uses that standard size and has enough clearance. If there's not enough space you need to extend the axis further out so they will fit.

So how do they work… the volume of water they displace will be the weight they can carry. The buoyant force of e.g. the smallest 110mm tire is e.g. about 178g. So e.g. 4 tires would support 712g. But this buoyant force would mean, that the tire would be fully submerged. Depending on your vehicle this might not be what you want. So with a load of 356g it would be half submerged. Like half of the axis would still be submerged as well. I would assume for most vehicles 25-33% would be targeted which would equal 116 to 154g for the smallest tires.

Tire Size (mm) buoyancy 1 tire (g) buoyancy 4 tires (g) tire ¼ submerged (g) tire ⅓ submerged (g)

110 178 712 178 237

120 257 1028 257 343

130 355 1421 355 474

140 475 1899 475 633

150 617 2467 617 822

160 784 3135 784 1045

You also got to consider that with the increasing tire size, also the weight of the tire increases, which already needs to be considered for the buoyancy. That depends on your filament, your slicer will help you out with that info.

If you are using it with the XRP Offroad or XRP Big Boy mod you most likely will have to aim for the 150mm tires. The chassis is quite heavy which also makes the tires heavy and the chassis also limits the tire size. So the XRP Boat Mod might be the better pick, especially if you're short on TPU as I am.

Printer Settings:

TL;DR

- Material: Flexible, e.g. TPU - Support: not needed - Walls: 5 - Bottom Shell Layers: 6 - Top Shell Layers: 6 - Infill Pattern: Octagram Spiral - Infill Density: 5 Full notes:

This tire is designed to be printed with a flexible material like TPU. It does not need any support.

Making this print watertight is the most important part. So this depends a lot on your material. I'll give you my thoughts and my settings, but they might be different for you.

I increased the wall count to 5 layers and the top and bottom shells to 6. With this structural integrity is basically taken care of. But infill does not only have the task to give structure to the printed part but also functions as support for printing. Most famous for that kind of task is Lightning infill. But when you have a look at the distribution you'll see it is not evenly spread. On our scale this might just be a theoretical issue. But I did still decide to go with the Octagram Spiral. Because it has a better weight distribution. And as mentioned it's mainly for the “inner support”, not for the integrity. So I did only go with 5%.

If you know your TPU good enough and feel save with less walls and shell layers, reduce them, every gram counts.

Additionally: In certain scenarios some other materials might also make sense. Like if it will only be used with sand and water you could also print it with non flexible materials. But with the rims having all sorts of mounts I'm not able to provide the rim along with the tire. But the licence will allow you to fiddle something together yourself.

Print List:

4x Tires

Test the Tire:

Before you assemble the wheels you should test if your print is really watertight. This does not necessarily need to be 100% water tight. Water might leak in if you keep it for days in water, but I don't think that's the scenario we're aiming for, but it's also not supposed to be a submarine and sink within 10 minutes.

If you're not satisfied or it heavily leaks you can add more walls and shell layers. But don't forget that this will also add weight and reduce the buoyant force by removing air and adding more material aka weight.

When you're happy with the result, mount the tires on the rims. :'D

Test the Vehicle:

When the wheels are attached, inspect that they have a firm sit. One lost wheel or tire might be good enough to roll over. Have a test drive on land. Test the buoyancy in shallow water. Give it a test ride.