Good to know, thanks! This is purely about my impatience/laziness in ordering a bunch of different sized belts. I do plan to use @solidgeek 's mount design, I haven’t seen/heard of a failure of that yet.
The teeth are 20 pitch with 20 degree pressure angle, and totally solid. I’ve had good luck with 3d printed parts if printed with thicker walls.
That’s a good point @acido about the strength of 3d printed parts. I’ll try and see if there’s a way to aggressively bench test these parts to find their torque failure point.
These are straight teeth spur gears right?
Have you looked into what type of bearings would be required? Probably thrust bearings.
I haven’t really seen thrust bearings used here on this forum. Is there a reason? I have considered it but I don’t know how they work exactly
If you don’t keep the bearings held in place they will want to run off away from the mount. Now that I think about it a thrust bearing wouldn’t be critical in this case but nonetheless a radial bearing (any wheel bearings will do) should be used. Edit: Just comes down to analyzing if the the outward force can be stopped by a bolt washer combo.
Yeah I use ball bearings, but would thrust bearings will be better in your opinion? It seems like it will be ideal from what i have read briefly, especially for helical gears
For my gears
I have a radial bearing for the wheel and middle gear. They aren’t 608 bearings and my bearing doesn’t sit on the trucks shaft.
I don’t think the axial load will be enough that thrust bearings will be impactful, plus 608 bearings are cheap.
woow great work can i get the stl files please ?
Agree Nylon is the only way to go when it comes to gears/pulleys, I printed my own motor pulley out of nylon it held up for about a month (maybe two) but started to get warped over time (never really cracked but the grub screw was held in with a locking nut and it had started to wear through the nylon so I went back to my metal one, was just for experimenting anyway). My wheel pulley I’ve been using for a good 6 months of on and off riding has been holding up fine and is made of plastic as well but I 3d printed the shape for that then made a mold with silicone (smooth-on) and then poured “industrial” strength resin in there to get a final solid part… it’s not a fast process but the result is a solid usable part.
Problems with printing nylon:
- Warps worse than ABS if not in a heated enclosure
- Is naturally lubricated so need to print slow or the teeth on the extruder will slip along instead of pushing the filament through the nozzle (something like 1/2 to 1/3 regular print speed)
- Absorbs water so you need to keep it dehydrated or spend about half a day drying it out slowly in a spare toaster oven or food dehydrator
Plus side it is insanely strong I have bashed on the parts printed with a hammer and not broken them, it is slightly compliant so it will give a bit rather than crack but it isn’t rubbery like TPU so it won’t flop around nearly as much. If you decide to go with printing nylon you can use “PVA” glue in America regular white Elmers brand glue is PVA glue and just put a drop on the build plate then spread it with water (it dissolves in water), the PVA will hold the nylon tight to the bed then the only issue is dissolving the PVA to get the part off (a challenge).
they may have an acceptable moment of resistance, but they you add wear to it… i wouldn’t want to loose breaks after 200km of riding going 30kmh…
No where in the industry are used plastic gears, especially in vehicles, and those gears found in drill are really hard core stuff that can not be compared to 3d printed parts out of “normal” materials
You can get metal gears in all sizes for a few $ each, and its not like its super hard to make a few holes anyways
https://www.gearsandsprockets.co.uk/ check this site out maybe you can find your gears
Yah actually for straight gear to gear meshing I would probably say any attempts with plastic aren’t going to be able to last in terms of wear over time. With the one I’m using on my wheel it’s only in contact with the rubber belt so I figure it’s actually less likely to tear through the belt and if I lose a tooth or two it’s not going to shear the entire thing in one go since the belt is only in contact with part of the pulley at a given time, if a belt breaks you’re in the same situation as if your gearing or any other part of the drive train fails (we need to ride cautious regardless).
Site is nice though and good point about just using metal ones and machining the holes yourself.
The motor gear on any build here is metal (from experienced builders) because it just gets eaten up by the belt, there’s plenty of posts about that The wheel drive can pass with plastic but a metal one would be better but there just isn’t a available solution to that yet (hard to get manufactured for a reasonable price)
I just dont get the obsession with 3d printed parts…
Like a guy on a lather drilled out the 4 holes needed 90 degree difference for my chain sprocket for 20$ in 10 minutes…
3D printed parts are popular due to accessibility and ease of model -> part process. If we all knew a guy in a machine shop with immediate access to a CNC machine then I’m sure people would rather have metal parts but for most of us this is out of reach or a lot more trouble than having a printer (I personally know a guy who runs a CNC shop in the area so I could actually get metal parts made but not sure what their costs are, it’s mostly a place to help get people off the street and help recently released prisoners to get a job).
Also I’m an experienced builder and I made mine out of plastic and it’s fine…
I googled lathe services in my city and found 2-3 guys went to their shop told them what i need and bam done
You dont need a cnc unless your making a big batch to sell in the future, for your personal needs it can be done by hand
try having your gears printed at Shapeways and let me know how long they last. They use sintered nylon which should last a while longer than hot deposit pla.
both the motor pulley and the wheel?
I did both at first, but wheel pulley is the only one I did out of the Task-9 plastic, the motor one was just printed from nylon and only lasted a couple of months (not trying to argue that metal will last longer). I haven’t tried making the motor pulley out of Task-9, but the stuff is pretty durable I don’t really see any wear on the teeth on the wheel pulley and been using it for quite a while (had some down time due to battery enclosure problems but back into riding a few times a week again). I’ll get some pics of the wheel pulley when I get home so can take a look for damage too.
^ can see how that one warped over the course of time (was a couple of months riding a few times a week as usual)
Added a few more pics to the custom pulleys album: