this post was submitted on 02 Dec 2023
712 points (93.0% liked)
Technology
59452 readers
3811 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
I considered that but couldn't make any conclusions. The driveshaft and sun gear are not added to the unsprung. I'd guess only half the weight of planets and carriers is added. It definitely adds the weight of the ring gear to the unsprung mass.
I'm also curious how this affects rotational mass. So while every component spinning with the wheel from tire to motor shaft has rotational inertia, small-diameter components such as drive shafts have relatively little rotational inertia. Wheels and even brake discs have a lot more. I don't have numbers obviously but I'm curious if the rotational mass of the ring gear ends up being detrimental compared to a heavier-weight lower-inertia cv setup.
Isn't the ring gear the wheel body (or whatever it's called), that is, even a fixed axle would have weight there, the gearteeth even provide stiffness. CV joints also contain unsprung mass, I'd say there might be a bit of a difference but nothing drastic. With modern fancy biomimetic wheel body geometries and everything you'll probably definitely be lighter than 80s steel rims. What happened to spoked wheels, anyway.
The CV only contributes half it's mass to unsprung weight, and this system still requires a drive shaft and either a CV or u-joint. But with more mass at the hub.
Typical hubs are still lighter than this, because this setup still requires the hub structure, it's just adding gearing out there.
Half of the hub is unsprung, the transition between sprung and unsprung is at those fancy articulating planetary gears. The drive shaft is definitely sprung, it and the motor is completely static relative to the battery and everything.