Quote:
Originally Posted by Fe_Will
General points:
1. Use the same pitch and pressure angle of gears through out (this prevents the chance of to dissimilar gears contacting)
2. The key is proper mesh to transfer motion, too much or little mesh can cause gear damage or inefficient transfer.
3. Avoid pairing gears made of different materials; the harder gear will wear out the softer more rapidly than two gears of the same material.
About "Mash" transmissions:
Yes, they require less machining but the act of moving a cluster of gears (or an entire shaft) linearly is the greatest challenge in my experience. If you were planning to servo shift then “mashing” is not for you… the force required is too great for the servo to do the job. Also, there are several older threads (2003-04 vintage) that discuss the trade offs of beveling the gears vs. a right angled gear.
About Dog shifting:
The dog and its corresponding surfaces are the most difficult parts of this transmission to craft. The dog and mating gears should be made of a hard material (they will take the most abuse). Several designs that I have seen were shifted by servos and just as many that were shifted by pneumatics.
In conclusion:
It’s a trade-off between servo shift and difficult machining vs. less machining and a tricky linear pneumatic shift, IMHO.
Good luck.
On a side note:
Seriously, what poor play from a team with experience with shifting transmissions to just go buy an off the shelf component, we in the FIRST community should be supporting each other’s learning…not …. (My grandmother would be ashamed if I finished this sentence in public.)
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Thanks so much, thats an excellent conglomeration of information, and you;re right we're trying to build our own to learn, not just to have a two speed on the robot.
Quote:
Originally Posted by Andy Baker
This is exactly the reason why we sell individual components of our Shifter transmissions. Teams can buy the hard-to-machine parts from us, with a significantly lower total price, after they design their custom transmission.
For instance, the Dog Gear, Large Output Gear, and Small Output Gear are very difficult to machine precisely. If I were to design a custom shifter, I would start with these three parts as COTS items and then design custom from there.
Good luck with your transmission.
Sincerely,
Andy Baker
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This is something i hadn;t even thought about, but will definitely bring up at the next meeting. I like this option because its gives us flexibility in our own design, but we aren;t constrained by our equipments potential. thanks!
Quote:
Originally Posted by ewrado
its realy good you can go slow on turns and then go fast when you need to
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Precisely. this is why we think this year is the best year to try one out, because that ability we believe will be key.
To everyone who responded, thanks so much for your input, you did make a differnece. expect to see 422 with a shiny 2 speed this year! We'll be at VCU and nat's.