In the rush to complete our shooter, our team made a mistake calculating gear ratios, and we discovered that we needed a 1:1 gearbox for our 775. We took one apart and ground off the teeth on the ring gear then carefully glued together the four gears on the gearbox. We left the teeth that would mesh with the gear on the motor’s output shaft unglued. After running these motors we discovered that they heated up too much due to what we guessed was the shaft slipping in the bearing. Then, because we didn’t use high temperature grease, the grease would slow down/stop the motor if it was cold. We have another one with different lubrication that doesn’t slow down, but the gearbox gets really hot. Does anybody know a better way to do this or a solution to the 1:1 problem? Also, I recall seeing a post about doing this on CD before, but I haven’t been able to find it by searching.
Is there any way you could modify your mounting to use a versaplanetary from vex pro? They are very easy to convert to 1:1
Buried deep in this thread (I’m guessing 80+ posts in) is a discussion about the heat generated by planetary gearboxes.
I was thinking about using a different gearbox or just a shaft coupler, but our current design is tight on space(we have a CNC’d mounting bracket which is build into the rest of the shooter frame) and doesn’t let us switch gears/motor/gearbox without some redesign, and we’re already using most of our withholding allowance on our 30 pt climber so a new setup isn’t really possible for us.
This may be a stupid question, but is it okay to just run the motor even if it heats up too much? We’ve used a modified one on our practice bot today, and no problems showed up after 1hr+ of shooting discs.
You realize the VersaPlanetary is only 0.125" wider than a P60, right? And probably the same length, or a little bit longer. I don’t think it’ll be nearly as difficult as you think to swap in a versaplanetary instead of your P60.
We’ve already considered the versaplanetary, and while it is only slightly bigger, it is too big to fit into our motor mount. It’s mounted between two important structural pieces that hold the shooter together which is a horrible design by us. We have a huge chunk of aluminum with a hole cut the size of the motor, and two pieces of box tubing which help keep it from wobbling that would prevent a different sized gearbox from fitting. Our current plan is to take off the transmission, and replace it with a shaft coupler if we really need to. If we find that running our “modified” transmissions doesn’t have a problem with hi-temp grease, we’ll just use that. Since my last post, I’ve found out that our team has actually done this modification before successfully and used it on a very good competition robot. The successful transmission is lost now, but the planetary gears were welded together, and the bearing was replaced with a high quality one. If we need to, we’ll bring hi-temp grease and a new bearing to the competition and fix it there.
If you are only needing 1:1, then there is plenty of meat in the input and output stages to mill down to the same size as the P60. The ring gear drove the width of the VP. We tried to get down to the same size as the P60, but the number of ring gear teeth is sort of a magic number for planetaries as you can get 3, 4, 5, 6, 7, 8, 9, and 10 to 1 ratios with the exact same ring gear so we made the size trade-off.
Of course, for your situation, the 1:1 will work if you mill the sides down.
Paul
We haven’t even looked at the versa planetary gearbox yet, so if it can be modified easily, we will modify it to fit.