So here is my personal problem: I would like a setup witch a pretty high gear ratio, big motor, rather small hanger and 100-120mm wheels.
That is kinda hard to achieve, as the limitations by the hanger width prohibiting large motors, wheel diameter too large to outward mount the motors and, wheel diameter too small for proper ground clearence when using a gear drive.
I have seen the 90° bevel gear drive, but it isn’t produced anymore. But it got me thinking…
It started as an idea of an attachment, that would allow a motor to be mounted at a 90° angle onto any motor mount (as it uses the same mounting holes as 63xx motors). There would just be two identical 90° bevel gears inside (and some bearings), so the ratio would be 1:1.
As I was looking through the parts available online, I found that such bevel gears are available with an 8mm keyway shaft bore, so I think it would be prettu easy to “just CNC” a case and go from there.
But what I also found are 1:2 bevel gears, which would be awesome for me personally, as I am never after high speeds, but high torque and this would double any gear ratio of drive setups.
I know this comes with extra weight (+ lever arm!), complexity and moving parts (and thus potential failure points and reduced efficiency). But I personally believe that would be well worth it.
To be clear – your idea is a gear drive that attached to standard motor mounts, so you would then use belts to connect the wheel? Or possibly attach this to an existing gear drive, for gear to gear action
I would say at first, just use the largest wheel pulley that is practical to you and increase motor current until you have the desired torque, see if it works for you without the motor overheating, if it doesn’t, then that idea sounds cool. But simplest way would be to use a bigger motor that will be able to work with the low gear ratio without overheating
The issue is though:
Larger motors need more space on a hanger. Sure, I would get a larger hanger, but that comes witch trade offs I might not want to make.
A universal 90° 1:2 “gear mount” solves both the issue of hanger space and increasing gearing.
It will also put the motor a lot further away from the hanger than it would typically be. The further away from the hanger it gets, the worse it will be affected by vibrations and jolts. Also putting a lot more strain on your mounts and trucks.
Yeah, the lever arm is a good bit langer, there is no arguing about that.
Is that an issue though? (i have zero experience with the stability of hangers and motor mounts)
if you reverse mount the thing, you could maybe mount the motors at 90°, so the don’t go along the line of the motor mounts but up and forward. This would help A LITTLE, but your point still stands of course.
Idk when you started this hobby, but it wasnt long ago that this wasnt the case. The lever arm of a motor on a mount should not be disregarded, its HUGE. Your hangar attachment system has to basically hold a really heavy hammer at like 40deg by just the end of the handle while it gets jolted around by the road.
All that to say, make sure your hangar attachment point is strong enough. It took multiple big vendors multiple tries to get it right.
Don’t underestimate this problem, it took years for the industry to solve it. If you think it might be strong enough, it’s way too weak. If you think it’s strong enough, it’s not. If you think it’s overkill, then it might be enough — if you connect both mounts together.
Dont give up! I really like the idea of a two-stage gear reduction. Right now you can’t do a good 2in1 board with gear drives. Either the gear ratio sucks for AT or there’s no clearance on 'thanes
If you can achieve 5:1 in a gearbox with the same ground clearance as the BN1 drives you’d have a hit product
The point about gear reduction was actually a secondary one tbh.
It was much more about mounting the motor at 90° onto ANY motor mount/gear drive, thus allowing large motors on small hangers. The gear reduction is just icing on the top, really… I keep pondering if I could somehow position the motors with such an attachment (or something similar). Maybe something that still turns the motor 90° but actually offsets it so it is parallel to the motor mount, just a little further up to clear the hanger? That is a lot of extra material and complexity though for not really a lot gained. Plus I’d run into isses with deck clearence, especcially when cornerning. Hmph, tough nut. Thought I was onto something here
Keep in mind every stage of gearing is going to lose you like 2-5% in efficiency or even more if you don’t design it well and maintain proper lubrication.
That is why it is often much better to jump in a single stage when possible. Bevel gears are not at all simple to design and a compact solution is likely to sound like a small blender. You also need to keep in mind there will be thrust loading added into the system and most motors don’t have bearings designed to handle much thrust.
With parallel gearing and especially with belts the alignment and spacing is more forgiving. With these gears it is very critical to assemble everything square and with the right offsets in several dimensions. Tolerance for alignment and assembly can be quite tricky.
