pic: Shifting Module for Drivetrain Concept

[crazyStone]

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[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.

[crazyStone]

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.

Mainly out of boredom, and in a pursuit to create something that was smaller and cheaper and possibly lighter than a AndyMark Supershifter. SuperShifters will probably be used due to the ease of obtaining them. This is as much design ideas, as practice CADing full assemblies from scratch. Chain drive does give the ability to alter the gear ratio as you pointed out. You also lose some efficency with running 2 CIM's on one shaft because one is always working against the other by a very small amount.

[Ether]

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.

What do you mean "working against the other" ?

[Kyle Love]

Originally Posted by Ether

What do you mean "working against the other" ?

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.

[Ether]

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.

?? If the motors are geared the same and are mechanically connected to the same shaft (as mentioned) they will be spinning at the same speed.

[Aren Siekmeier]

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?).

[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.

[lemiant]

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.

You are right. You're team is wrong. There were issues with motor going different speeds forwards and reverse back in the day, when we were using drill motors - which do have a significant bias. However that shouldn't affect your design for three reasons:

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.

[Aren Siekmeier]

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).

[lemiant]

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).

True, but that definitely doesn't apply to super shifters

[Brandon Holley]

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