A few of us were sitting around a table in the shop the other night discussing the pros and cons of open and closed gearboxes.
This was brought up during a challenge for a small group of students to redesign a transmission for the 2012 robot. We have done both in the past, but what are the experiences of other teams?
We have run custom (not as aesthetically appealing as other teams have) open transmissions; and have used more than our fair share of COTS transmissions, which are typically enclosed. We have always had success with both. What are your experiences?
What lessons have you learned that can be shared with others?
Note: This is not meant to be a standard vs custom thread, but focused on open vs closed designs
“Junk” gets all up in them too easy. There really isn’t much of a gain by having them open. If your worried about the weight, just put something thin around them.
Haven’t had much “junk” get in our gearboxes and we leave them open. But I do agree, you can wrap some thin polycarbonate around them.
Most teams have issues with grease getting everywhere. The last two years we switched to a DuPont Dry Grease which has fixed that issue. For a direct drive WCD setup, its a whole lot easier to run open gearboxes too.
Why we do it:
-Lighter
-Less parts
-Internals are Visible
-Easy maintenance (Dog shifters, Chain etc…)
-Easier to teach new kids (not really a design decision just a benefit)
This. In my experience, unless grease splatter is a major concern, open is almost always better, mostly because of weight. For example, running a Toughbox with delrin spacers instead of the usual aluminium enclosure saves over half a pound per robot. We ran them that way, and aside from a little grease getting thrown around, they ran like champs.
You may be a little too worried about stuff getting in the gearbox, and not considering the maintenance and weight benefits. I personally have never seen a gearbox fail from foreign material inside. Usually, binding that you might think was caused by stuff getting caught in the gears is caused by improper grease use.
dust covers are always a good idea. nothing sucks more than losing because of something stupid like your robot sucking up some kind of debris (carpet fuzz, screw, other stuff) and jamming the gearbox which takes out 1/2 your drive
Also keep in mind safety issues… An open gear box makes it a lot easier for someone to lose a finger! This can often be taken care of with appropriate warning tape and proper safety procedures, but you want to make sure your safe with an open gear box design.
We covered our supershifters with metal flashing this season. Weighs next to nothing but next year we’d probably use thin lexan so we can see into the gearbox.
We had Gearbox shields on the bottom of our gearbox for the first time last year. We did this because we were running worm gears and had to keep them free of debris, else lose more efficiency. The shield was made out of 1/32 aluminum and was very light.
We’re doing so again on a new gearbox, this time it’s less of an afterthought.
Historically we have machined new sideplates for the AM supershifter or Gen 1 although we have also added provisions for a third motor in some seasons. Per my understanding Andymark’s fully covered gearboxes are more for legality and increased functionality in a greater number situations. (they can’t get fingers sucked into them, they can be safely run on a table, and more easily interfaced to a great number of designs, etc.) Custom sideplates eliminate alot of functionality that while important for mass production/consumption may not be important in your design. This is traded off in favor of things like reduced weight, better packaging, more favorable gear ratios, etc which most teams find desirable.
In any case, we cover our otherwise open gearboxes with thin polycarb which seems to work well.
Gears produce metal dust and that dust can find it’s way into speed controllers and other electronics. If you don’t place covers then insure that there is some distance between the transmissions and electricals.
Not the cheapest, but it sealed well, lite weight, conformed to the surface, looks shiny, trims to edge very well, and very durable. One roll will last you for a long time.