How so?
2 Likes
idk prints with perfect circles sideways never go great for me
2 Likes
Maybe try “fine” prints, the more layers, the less overhang, the cleaner the circle.
2 Likes
But I think print orientation is key here to solve this blowout problem
1 Like
Here you can see the print orientation of the hooks being tested changed the strength dramatically.
2 Likes
right I have watched many of those videos, I’m concerned how the strength varying throughout the wheels rotation could cause failure.
1 Like
Wouldn’t the rotational load be held together more or less by the tube and tire? It’s only outward forces on the lip that have nothing supporting them.
Either way, only one way to find out if it would work.
2 Likes
For a flat print maybe a multi-process print, starting a few layers below the stress point I would make it all top or bottom layers, this is a complete solid layer, different from 100% infill, at least on simplify3d anyhow. When I tried 100% infill it was still lines/grid of some sort just really tightly layed, with it set to say 20 bottom layers they are all completely solid and biaxle like layers.
1 Like
Here’s the reason why I changed from M4x40 bolt to a M5x60 bolt.
Any area that extends beyond the head or the nut of the bolt is “un-supported” by the bolt, aka all the
structural strength there is purely provided by the 3d-print. This is very un-ideal as the lips of the rim are most stressed area.
The longer M5x60 is going to be able to support clamping the two halves together better as it reaches further towards the outside, aka there’s less of an “overhang” that is not supported by the bolt . Plus, there’s the added benefit of slightly larger nut and head of the bolt, so the area it’s able to distribute the clamping force to the 3d-print is larger.
4 Likes
I have also found this to be the case, and have been able to make some extremely durable parts by using solid “bottom layers” all the way through the part, and 0% infill layers.
1 Like
Here’s the old and new versions side-by-side. I still need to print another new unit so I can get both back wheels mounted.
5 Likes
Make it so you bolt trhough, and fixing the outer lips like that
2 Likes
How about washers on the bolts that will cover to the edge of the lip?
1 Like
I suppose that’ll be the next step, if this iteration still doesn’t hold up.
1 Like
So this is where I’m at currently. After doing some test riding with the 10" wheelbarrow tires, they just are too unbalanced and start to vibrate/oscillate/resonate so nasty at 30kmh/18mph that they just ain’t worth it, so I’m in the process of switching back to the safe&sound off-road 8" tires and making custom rims for them, so I can get the bigger bearings on there.
Figured out also a good way to do faster test prints for prototype pieces. Print them with the full bearing pockets so you can mount them on the axles, but with only a section of the outer edge.
as an added bonus you get a good look at the cross-section
I then out of boredom went to aliexpress to check if I could find any good 10" tires and order a set of 4 of these 10x2.50 scooter tires. They don’t exactly have an off-road thread profile, but might be good for summer use, but will probably also test them out this winter.
4 Likes
Things have been rolling forward in the background with the rims, but I just didn’t feel that there were enough to post updates about, I’ve been keeping silent.
Anyways, the rims for the 8" tires have been working great and since the first version with the big 6301 bearings. I later did a little testing with the rolling friction of the bearings themselves between the 6301 (12x37x12) and the more common MBS sized 6001 (12x28x8) and figured out that I can get a bit more range with the 6001s as they roll a bit better, although that might also partially be because the SKF 6301s that I used were of the model 6301-2RSH, the ‘H’ at the end standing for “heavy duty”-seals, which I suspect might increase the rolling resistance a little bit for the better sealing seals.
I also have this freak unit, which was the first one I printed for the 6001 bearings. It has the smaller 6001 bearing, but I forgot to shrink the size of the center section, which is still sized for the 6301, but has the 6001 pocket size, so it looks a bit… big.
I also did a little precursory test for widening the rims, based on the talk on this thread:
I just added a little extra spacer bit between the front and back side of the rim (printed in yellow), just to see how the tire behaved when pumped up, but haven’t actually ridden on them. It also causes the valve stem hole to get more offset. I think I would have added a bigger spacer, but I didn’t have any longer 5M bolts, so they were the limiting factor how much I could actually add spacing.
Now we finally get to the more recent… bigger things… Rims for 10 Inch tires. The tires are from aliexpress:
I had originally prototyped the barrel of the rim with 10 bolts, but it was a bit too dense/busy, so I decided to go for 8 bolts instead and 4 spoke design.
I am currently happy with the design and I am going to need to order more filament to print them for all 4 corners.
Slightly improved design, which was optimized for printing.
9 Likes
Do you have any alignment issues? How’s the durability on the pulleys? Are they well balanced?
I kinda dropped my project as I bought some bergs, but I’m looking to get into designing a new set with some ideas I had recently.
1 Like
I actually did have, but I figured out a procedure on how to align them properly. I have them pretty bang on at them moment. I can go into this a bit further with pictures and explanation, if you’re interested.
I have metal pulleys on the motors and I print the wheel pulleys with PETG. PLA has too low glass transition temperature and softens much faster and wears away much more quickly, but after I get the PETG pulleys run in and the teeth deform a little bit to better fit the belt, they are usually good for few thousand kilometers, so I don’t really fret about them.
I believe the current PETG gears have around 1000 km on them and no significant teeth deformation, but they are big at 50+ teeth, so the load is distributed along more teeth. I remember on my first boards that I ran Thanes on, even the PETG gears with around 25 teeth didn’t last that long in comparison. The side of the pulley is a bit scuffed, as I might gotten something stuck between the pulley and motor mounts and it grounded on the pulley.
No noticeable vibrations until around 43km/h, so not great, not terrible. There is option to do some extra balancing options, but haven’t bothered. The 10 inch wheels clearly free roll to a certain position, indicating a heavy point, but the outer diameter is at least very uniform. Once I get them on all 4 corners and I get some testing done, I’ll see if I need to figure out a method to balance them.
3 Likes
Looking great dude, where’s the models/STLs? 
I’ve got some ideas about 3d printed hubs and gears, I think I’ve an unconventional approach that would be extremely durable, based on some work I’ve been doing with FDM printed parts for metal working machinery. Would love to try them out using your models if you’re willing to share. I’m not that hot with cad yet.
1 Like
Which rim models are you interested in?
4 Likes