Society of Robots - Robot Forum

Mechanics and Construction => Mechanics and Construction => Topic started by: Jak24 on May 07, 2010, 10:26:14 AM

Title: planetery and spur gears
Post by: Jak24 on May 07, 2010, 10:26:14 AM

HI guys !

I hear that planetary is better then spur gearboxes but why?? (planetary also cost much more)

Thanks

Regards

Jak24

Title: Re: planetery and spur gears
Post by: Admin on May 07, 2010, 08:07:35 PM

Being better is a relative thing - better for what?

The advantage of planetary gears is that it has a much higher gear ratio than typical gear setups.

But planetary setups use spur gears, so your question is a bit odd ;)

Title: Re: planetery and spur gears
Post by: Jak24 on May 08, 2010, 12:49:49 AM

HI!

Well i looking at these gearboxes for my motors :
http://shop.maxonmotor.com/ishop/article/article/110453.xml (http://shop.maxonmotor.com/ishop/article/article/110453.xml)
and this
http://shop.maxonmotor.com/ishop/article/article/143974.xml (http://shop.maxonmotor.com/ishop/article/article/143974.xml)
but one costs 100 dollars the other one cost 50 .... and there isn't that much difference....
any suggestions are welcome as to witch one i should i buy?

Regards

Jak24

Title: Re: planetery and spur gears
Post by: Admin on May 08, 2010, 12:53:43 AM

The more expensive one allows 3x the torque, definitely a big difference ;)

Title: Re: planetery and spur gears
Post by: Jak24 on May 08, 2010, 01:19:00 AM

HI

thanks for info .....the reason i wanted to get the spur cause it looked easier to mount on the other hand a planetary looked harder to mount ...any suggestions about mounting? thanks

Regards

Jak24

Title: Re: planetery and spur gears
Post by: Admin on May 08, 2010, 02:28:08 AM

I always use CAD to plan out how I mount things . . .

Title: Re: planetery and spur gears
Post by: Jak24 on May 08, 2010, 02:43:23 AM

HI

Thanks ....but if you see any thing that i could use for mounting please inform me !
Regards

Jak24

Title: Re: planetery and spur gears
Post by: antom on May 18, 2010, 09:55:44 PM

A planetary gearbox uses multiple spur gears to achieve1 stage of gear reduction, hence the higher torque ratings.
A spur gearbox would have only 2 mating gears per stage. Each stage usually 6:1 or less.
So basically just follow the specs. of the mfg.

Title: Re: planetery and spur gears
Post by: Ro-Bot-X on May 19, 2010, 05:13:53 AM

Motor mounts: http://www.robotmarketplace.com/products/motor_mounts.html (http://www.robotmarketplace.com/products/motor_mounts.html)

Title: Re: planetery and spur gears
Post by: Brandon121233 on May 25, 2010, 01:15:39 PM

Also planetary gears are in my experience generally a lot nosier than their spur gear counterparts. I started with planetary on my robot and switched to spur simply because I didn't want it to sound like my cordless drill was roaming around the house.

Title: Re: planetery and spur gears
Post by: Admin on May 25, 2010, 07:56:24 PM

Quote from: Brandon121233 on May 25, 2010, 01:15:39 PM

Also planetary gears are in my experience generally a lot nosier than their spur gear counterparts. I started with planetary on my robot and switched to spur simply because I didn't want it to sound like my cordless drill was roaming around the house.

The noise comes from having more gears (more contact points). Planetary gear boxes use only spur gears.

Noise is also a sign of poorly designed gears, causing low(er) efficiency.

Title: Re: planetery and spur gears
Post by: Brandon121233 on May 25, 2010, 08:32:11 PM

lets just put it this way, any planetary gearbox that is affordable for the average hobbyist is generally going to be louder than its equivalent spur gearbox. Also correct me if Im wrong but generally planetary gears have a bit of slop added in otherwise they would get locked up on them selves. Anyway helical gears are way better but not sure how many small scale motors would use them.