RS-395 safe loading

[R.C.]

Originally Posted by sanddrag

We ran our swerve steering on 550s through 49:1 Versaplanetaries and then to an 84:24 reduction for a total reduction of 171.5:1 and they got REALLY burning hot. It was kind of surprising and somewhat concerning. It may be due in part to inefficiencies in the Versaplanetaries. I think the frequent direction reversals and PID position holding are also a contributing factor.

David,

Thats odd, we used a BAG with a 75:1 total reduction (way less than you guys). Ours remained cool after 30 minutes of driving. We really like using the BAG's on steering this year, especially since they can handle the heat.

[Aren_Hill]

The 2012 Neutrino CIM in wheel swerve was steered using banebot 395 motors, didn't have any problems. I don't remember the final gear ratio off the top of my head.

-Aren

[Gdeaver]

The JVN calculator may not be good for steering calculations on co-axial steering. The use of miter gears cause an additional load on the steering motor. If the top pulley turns clockwise, there is a counter clock wise torque on the wheel cage that the steering system must overcome. The more load put on the driven wheels, the greater this forces is. During hard accelerations and intense robot to robots interaction this force can be quite large. I have no idea how to set up an equation for it. Our team has never quantified it. We could have used the new current measuring capability of the PDM. We need to look at this current draw because if we have a more normal FRC game next year we will have to worry about total current draw and power management. In 2014 our current logs showed that there were a few matches the Roborio would have entered brown out.

[Andrew Schreiber]

Having never built a swerve I can only relay what information has been given to me by those who have. John Novak (16) remarked that they wished they could use the 395 without it using their allotment of BB motors (this was prior to 2015 motor rules) His reasoning was that they have had issues with starting off in a direction other than where their wheels are currently pointing due to current draw. (4x 550s and 4x Cims starting up at once is a fair bit of current draw) and by switching to smaller motors their current draw would be lower. Based on this being John, I assume he realizes the tradeoffs with that.

My theory on why 16 could get away with it is less based on mechanical construction and more based on software and driving style. A lot of swerves operate as swerves all the time (rapid direction changes) but 16's swerves are typically driven more like 254 drives their tank drives (long smooth arcs) This is, obviously, less rough on the steering motors than rapidly changing directions all the time. This theory is backed up by the behavior of 91 (16's rookie team) at Ozark Mountain Brawl in 2014. The drivers had minimal drive practice and tended to rely on frequent direction changes. Their motors were hotter and, in their last elims match, they managed to pop the main breaker on the bot.

Of course, John, JT, of Jeff would know more than I would.

[billbo911]

This will be slightly off topic as we didn't use 395's for steering, but to rotate our turret. We did this in both 2009 and 2012. We used the same approach both times with great success.

The basic configuration was a 395 driving a planetary transmission removed from a Globe motor. Globe motors were no longer legal for use and we had dozens of them sitting around.

Here is a little pictorial of how we interfaced them.




Notice the small aluminum sleeve between the motor shaft and the sun gear. That was the trickiest part to make. So, as you can imagine, these were quite simple to create.



Globe transmissions are approximately 90:1 reduction. These assemblies never even got warm after running tests and calibrations for hours.