26-08-2011 13:03

AustinSchuh

Re: pic: Shifting Module for Drivetrain Concept

Ok, I'm going to bite. Any reason why you aren't using the gears out of AndyMark's gearboxes and saving all that machining? They have some pretty nice ratios. You can make custom side plates, use the final chain reduction to get any speed you want at the wheels, etc.

26-08-2011 13:33

crazyStone

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by AustinSchuh Ok, I'm going to bite. Any reason why you aren't using the gears out of AndyMark's gearboxes and saving all that machining? They have some pretty nice ratios. You can make custom side plates, use the final chain reduction to get any speed you want at the wheels, etc.

26-08-2011 13:45

Ether

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by crazyStone You also lose some efficiency with running 2 CIM's on one shaft because one is always working against the other by a very small amount.

26-08-2011 14:06

Kyle Love

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by Ether What do you mean "working against the other" ?

26-08-2011 14:22

Ether

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by Kyle Love When you run a two motor set up as mentioned, one motor will be running in reverse of the other, causing an efficiency loss and one motor spinning a bit slower then the other.

26-08-2011 14:38

Aren Siekmeier

Re: pic: Shifting Module for Drivetrain Concept

They will absolutely be running at the same speed (at least I hope so ) but they may be at different points on their performance curves, if these curves vary based on direction. This means you aren't necessarily at the peak power of each motor (not necessarily affecting efficiency...). However, the directional bias of a CIM is certainly small enough to disregard (if it exists?).

26-08-2011 17:00

crazyStone

Re: pic: Shifting Module for Drivetrain Concept

I thought the same thing that they should be the same speed, I was just told by some members of my team that the difference in preformance is great enough between 2 cims that a noticeable amount of preformance is lost when they are linked together. I find that hard to believe, but thats why this has 4 seperate transmissions to appease that belief. The pros of simply using a Supershifter will be raised. Yes the motors are being coded to run at the same speed, it is merely electrical differences within the construction of the motors that will create slight variations. Thats my understanding at least. However I am much more mechanically inclined as opposed to electrical/pneumatics, so I could be totally wrong.

26-08-2011 17:27

lemiant

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by crazyStone I thought the same thing that they should be the same speed, I was just told by some members of my team that the difference in preformance is great enough between 2 cims that a noticeable amount of preformance is lost when they are linked together. I find that hard to believe, but thats why this has 4 seperate transmissions to appease that belief. The pros of simply using a Supershifter will be raised. Yes the motors are being coded to run at the same speed, it is merely electrical differences within the construction of the motors that will create slight variations. Thats my understanding at least. However I am much more mechanically inclined as opposed to electrical/pneumatics, so I could be totally wrong.

1. CIMs do not have a measurable bias
2. The suggestion that the motors would 'fight' is wrong. They will settle into different points on their performance curve, with one doing more work, but they are still working together
3. Motors in the same gearbox are going the SAME direction.

27-08-2011 01:02

Aren Siekmeier

Re: pic: Shifting Module for Drivetrain Concept

And besides, even with separate transmissions and all, you still have both wheels on the ground that have the same constraint on them: they must spin at the same speed. The only thing separate transmissions accomplishes is the possibility of independent motion of the wheels, which would only shred your treads unless you had mechanum.

Motors in the same gearbox are USUALLY going the same direction just because of how they are usually geared together, but it is possible to have them switched, by putting them on opposite ends of a shaft or by having an even number of gears between. In fact, one widespread instance of counter-rotating motors this year was minibots. The wheels obviously had to spin at the same speeds, just in different directions (or the motors were often on different sides of the wheels, if the wheels were both on the same side).

27-08-2011 01:04

lemiant

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by compwiztobe Motors in the same gearbox are USUALLY going the same direction just because of how they are usually geared together, but it is possible to have them switched, by putting them on opposite ends of a shaft or by having an even number of gears between. In fact, one widespread instance of counter-rotating motors this year was minibots. The wheels obviously had to spin at the same speeds, just in different directions (or the motors were often on different sides of the wheels, if the wheels were both on the same side).

28-08-2011 21:03

Kyle Love

Re: pic: Shifting Module for Drivetrain Concept

AH, got my motor types wrong...whoops.

28-08-2011 21:13

Aren Siekmeier

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by lemiant True, but that definitely doesn't apply to super shifters

28-08-2011 22:24

Hawiian Cadder

Re: pic: Shifting Module for Drivetrain Concept

Unless your wheels are scrubbing, the motors are "fighting" each other just as much. If we assume the wheels, gears, and chain runs are all exactly the same then the motors, even if though they are in different gearboxes will be spinning the same speed, unless your robot is sliding.

28-08-2011 23:17

lemiant

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by compwiztobe I'm confused. What doesn't apply to super shifters?

28-08-2011 23:19

Aren Siekmeier

Re: pic: Shifting Module for Drivetrain Concept

Quote:

Originally Posted by lemiant In that post I am referring to special cases that have the motors in one transmissions spinning opposite directions. They exist, but aren't really relevant because he will be using supershifters. And supershifters do spin the motors the same direction.

29-08-2011 09:27

Brandon Holley

Re: pic: Shifting Module for Drivetrain Concept

This is a good start! I do have a few questions for you though:

-The initial stage of gearing has a relatively small face width. Did you do any calculations to determine those gears were effectively wide enough? Also, where were you going to purchase these gears from?

-Please correct me if I'm wrong, but it looks like you are going to be using a piece of alumnium channel as the gearbox housing. Using a housing like that has its pros and cons, one of the cons being unable to "open" the gearbox up. If you look at how the bearings are pressed into your housing, I think you will see there may be some issue. It will be extremely difficult, if not impossible to press bearings like that into a closed gearbox. Is this something you considered?

-The Bimba cylinder appears to be directly mounted to the dog gear. I'm sure you are familiar with AM style shifting gearboxes (as this is where that dog gear is from). Use those shifting components as a guideline for your design. That design has worked well for a long time now because it is a very rugged and robust design.


Keep working at it!

-Brando