View Full Version : AndyMark Nano Break In
We'll have 4 AndyMark Nanos on our robot this year for the Mechanum drive system. We've learned from experience it's important to break in transmissions on the bench before putting them on the robot and were planning on doing the same with the Nanos. When we did this, though, we're finding a huge range in current draw between Nanos (4 and a spare) with two drawing 11 amps just sitting on the bench, two drawing 6 and one drawing 3 amps!
We haven't run them for the hour or so we typically would but the 11 amp ones get too hot to hold after five minutes. We'd have to run them in bursts to break in. We've looked all through them and can't see anything obviously wrong.
What we've done to the transmissions getting them ready is installed a Nylon spacer on the last stage to keep the axle from sliding back and forth (screwing up the encoder) and switched to the AndyMark aluminum gear in the first stage for weight. The nylon washer has been checked and isn't too tight. All of the transmission have been heavily lubed with SuperLube synthetic grease.
Has anyone else seen similar results? Any ideas of what to try or should we just keep running them and hope they wear in?
Daniel_LaFleur
04-02-2010, 13:17
We found a whole lot of slop in the Nanos we got. We sent a video to AndyMark and then took the nanos apart and added a spacer (fender washer) to the output shaft to take up the slop. Seems to have worked for us, although we'll be fully testing this on Saturday.
Which versions of the NANO are you seeing issues with? Is this ont he keyed shaft version or the hex shaft version or both?
Thanks,
Rob
There is one non-sealed bearing in the Nano. If it is not in the right place it will interfere with the fit of the motor. If you look at where the motor mounts that is where that bearing should be. You may have swapped the two bearings when you installed the aluminum gear.
We found a whole lot of slop in the Nanos we got. We sent a video to AndyMark and then took the nanos apart and added a spacer (fender washer) to the output shaft to take up the slop. Seems to have worked for us, although we'll be fully testing this on Saturday.
To the inside of the casing on the output shaft, correct? We have the hex output shafts, and I'm thinking that we will wind up doing this. Finding spacers for a hex shaft is a pain; the closest one I can find is on sdp-si.com and it's $13.00 for a 3" length. We could go with oversided fender washers, but I'm afraid that they'll rub the outside of the bearing, thus making the whole thing inefficient. So Andy, when you read this, perhaps that's a viable part for next year (Aluminum spacer for 1/2" and 3/8" hex shafts, either a rod stock or individual spacers).
As for the variable burn-in issue, I would presume that it's the CIM gear that's the issue. We found that 2 of the 4 CIM pinions in this year's KOP do not mesh well with the other gears; one downright gets stuck if you let it free-roll. Thus we swapped to a previous year's pinion for the burn in. In the offseason we may experiment with fixing the gears by filing them down a hair.
If you make 10,000 parts, some of them are bound to be bad ;)
AdamHeard
04-02-2010, 13:41
To the inside of the casing on the output shaft, correct? We have the hex output shafts, and I'm thinking that we will wind up doing this. Finding spacers for a hex shaft is a pain; the closest one I can find is on sdp-si.com and it's $13.00 for a 3" length. We could go with oversided fender washers, but I'm afraid that they'll rub the outside of the bearing, thus making the whole thing inefficient. So Andy, when you read this, perhaps that's a viable part for next year (Aluminum spacer for 1/2" and 3/8" hex shafts, either a rod stock or individual spacers).
As for the variable burn-in issue, I would presume that it's the CIM gear that's the issue. We found that 2 of the 4 CIM pinions in this year's KOP do not mesh well with the other gears; one downright gets stuck if you let it free-roll. Thus we swapped to a previous year's pinion for the burn in. In the offseason we may experiment with fixing the gears by filing them down a hair.
If you make 10,000 parts, some of them are bound to be bad ;)
why does the spacer need a hex?
Playing with the CAD model a bit I can see where the spacer would be needed on the output shaft. That end of the output shaft (between the last gear and the inside of the plate) is a 1/2" hex on both versions of the output shaft.
I would imagine that a washer with a round hole would function and that you don't need to match the hex shape to get this right. I will be stopping at the hardware store tonight and hoping that our NANO order is in today :]
As far as the sticky CIM pinions I can say that we observed that on one pinion from the KOP this year. It was not very bad and wore in quickly running the transmission on a bench. I can see how a small variation here would quickly cause a problem.
Rob
Playing with the CAD model a bit I can see where the spacer would be needed on the output shaft. That end of the output shaft (between the last gear and the inside of the plate) is a 1/2" hex on both versions of the output shaft.
I would imagine that a washer with a round hole would function and that you don't need to match the hex shape to get this right. I will be stopping at the hardware store tonight and hoping that our NANO order is in today :]
As far as the sticky CIM pinions I can say that we observed that on one pinion from the KOP this year. It was not very bad and wore in quickly running the transmission on a bench. I can see how a small variation here would quickly cause a problem.
Rob
There is a large washer on that shaft that is not in the cad file. It goes between the large bearing and large output gear.
Jonathan Norris
04-02-2010, 14:03
There is one non-sealed bearing in the Nano. If it is not in the right place it will interfere with the fit of the motor. If you look at where the motor mounts that is where that bearing should be. You may have swapped the two bearings when you installed the aluminum gear.
We saw a similar issue when installing a FP planetary to the Nano, the bearing stuck out of the back plate interfering with the mount of the gearbox. How ours was assembled I don't think a CIM would have fit without taking it apart and re assembling it. Because we were are just using the AM planetary we were able to file it down a bit to fit. I'll take some pictures of our problem with them today.
Ours are the keyed shaft version of the Nano but, as was mentioned, I don't think it matters for the nylon washer. There's no way that encoder would be happy with the slop in the shaft as it comes from the factory so be sure to look at this before installing a Nano if you expect to use encoders.
We'll take a look at the bearing as IndySam mentioned and also the pinions.
How long do you folks run them for on the bench?
There is a large washer on that shaft that is not in the cad file. It goes between the large bearing and large output gear.
Thanks for the info here! I am running half blind without parts in hand yet. If this washer is in place do you know what the source of slop in this shaft is?
Thanks,
Rob
We saw a similar issue when installing a FP planetary to the Nano, the bearing stuck out of the back plate interfering with the mount of the gearbox. How ours was assembled I don't think a CIM would have fit without taking it apart and re assembling it. Because we were are just using the AM planetary we were able to file it down a bit to fit. I'll take some pictures of our problem with them today.
Some of the early shipments went out with the wrong bearing. Contact AM and they will send the correct bearing.
Thanks for the info here! I am running half blind without parts in hand yet. If this washer is in place do you know what the source of slop in this shaft is?
Thanks,
Rob
Even with the washer there is some slop.
Daniel_LaFleur
04-02-2010, 14:17
To the inside of the casing on the output shaft, correct? We have the hex output shafts, and I'm thinking that we will wind up doing this. Finding spacers for a hex shaft is a pain; the closest one I can find is on sdp-si.com and it's $13.00 for a 3" length. We could go with oversided fender washers, but I'm afraid that they'll rub the outside of the bearing, thus making the whole thing inefficient. So Andy, when you read this, perhaps that's a viable part for next year (Aluminum spacer for 1/2" and 3/8" hex shafts, either a rod stock or individual spacers).
If you make 10,000 parts, some of them are bound to be bad ;)
Inside of the output shaft ... correct.
We have the Keyed output shaft, but internally to the nano it is Hex shaft. We used just a normal (re: round ID) washer to take up the slop and it's running well (we'll do a lot more testing this weekend).
Additionally, I suggest that the nanos get lubricated and run for a time as they seem to need to break in a bit.
While I'm a bit concerned as to the quality of the stuff we've recieved from AndyMark, their customer service has been top notch. My biggist concern is for the rookie and less mentored teams that may not understand how the slop can cause all sorts of failure modes.
sanddrag
04-02-2010, 14:23
I've done break-in on a number of FRC gearboxes over the years, and let me tell you, it makes a big difference. When running properly, a typical gearbox like the Nano should draw between 2.3 to 2.8 Amps per CIM with no load, from a 12 Volt supply.
Yours are drawing too much. You have something binding.
One year, I had a tight running gearbox, and no way to remachine the plates to increase center distance, and no lapping compound available. I took a bottle of car polish and poured it right in the meshing gears. A few cycles of this, and 20 minutes later, and a bunch of cleanup, and it ran like butter and current draw was less than half of what it started at.
For those of you designing your own gearboxes, make sure to use precision ground bearings. I've seen teams build gearboxes with non-precision general purpose bearings, that just aren't rated for the loads or speed they see, and they fail. I've even seen sloppiness in brand new bearings cause a gearbox to bind enough to nearly stall a CIM.
This is an excellent thread with good information. Thanks for contributing!
As far as "how long to run a gearbox in?" I would say the conditions listed bt Sanddrag for current draw are good. We have typically run KOP Toughboxes for 15 to 25 minutes before getting to those current levels. be sure to monitor motor heat and listen for odd noises that could indicate an assembly problem. Monitoring your current draw with a benchtop power supply is very helpful.
Good luck!
Rob
dyanoshak
04-02-2010, 15:10
Monitoring your current draw with a benchtop power supply is very helpful.
Using a Black Jaguar and BDC-COMM can make breaking-in a gearbox quite easy.
Set your motor to run at a specific voltage in voltage mode, or a specific speed in speed mode (with an encoder), and then monitor the motor current values it spits out. Just like on TV, set it, and forget it! (but not really, be safe and keep an eye on things)
-David
Jonathan Norris
04-02-2010, 17:09
here are some photos I've taken of the two issues discussed about the Nano gearboxes. First is our issue with the bearing sticking out and getting in the way of the motor mount, we were able to fix this easily. The second picture shows the slack in the gearbox with the big washer that comes installed.
http://twitpic.com/11e1jk
http://twitpic.com/11e1o6
CraigHickman
04-02-2010, 17:12
I've done break-in on a number of FRC gearboxes over the years, and let me tell you, it makes a big difference. When running properly, a typical gearbox like the Nano should draw between 2.3 to 2.8 Amps per CIM with no load, from a 12 Volt supply.
Yours are drawing too much. You have something binding.
One year, I had a tight running gearbox, and no way to remachine the plates to increase center distance, and no lapping compound available. I took a bottle of car polish and poured it right in the meshing gears. A few cycles of this, and 20 minutes later, and a bunch of cleanup, and it ran like butter and current draw was less than half of what it started at.
For those of you designing your own gearboxes, make sure to use precision ground bearings. I've seen teams build gearboxes with non-precision general purpose bearings, that just aren't rated for the loads or speed they see, and they fail. I've even seen sloppiness in brand new bearings cause a gearbox to bind enough to nearly stall a CIM.
Do you break your gearbox in with any sort of lubrication or abrasives? We usually just dump a glob of lithium grease onto the gears during break in, but I'm curious as to how others go about this process.
here are some photos I've taken of the two issues discussed about the Nano gearboxes. First is our issue with the bearing sticking out and getting in the way of the motor mount, we were able to fix this easily. The second picture shows the slack in the gearbox with the big washer that comes installed.
Jonathan,
You say you fixed the bearing pushing out easily...was with the AM trnasmission I could see how you might make room. How do us CIM folks do it though?
AdamHeard
04-02-2010, 19:14
Does anyone know a good way to get current draw using a voltmeter and ohms law?
sanddrag
04-02-2010, 20:59
Do you break your gearbox in with any sort of lubrication or abrasives? We usually just dump a glob of lithium grease onto the gears during break in, but I'm curious as to how others go about this process. Grease is to prevent wear. During break in, you want to wear the gears into each other, not to prevent it. An abrasive compound is usually used for this. I would not grease the gears if the intent is to wear them in. However, once worn in, I would recommend always keeping the gears greased to prevent further wear.
For 968, we have not had to do any specific break-in procedure on our gearboxes in recent years, since we add a couple thousandths extra center-to-center distance.
DonRotolo
04-02-2010, 22:20
Does anyone know a good way to get current draw using a voltmeter and ohms law?
Yes, of course. I=V/R, right?
So, carefully measure the Resistance of a piece of wire (I think #10 is 0.1 Ohms per foot, but check me on that. Measure several feet, accurately, being sure to subtract the resistance of the test probes). Now you know R
Measure Voltage across R while the motor is running, and do the math to solve for I (in Amperes)
Note that even a small error in R can lead to large errors in I, but this is also good for relative measurements (as in "it's drawing half the current it was drawing before")
We use a clamp on ammeter when just running DC off a battery. We also use a current shunt such as this one: http://www.powerwerx.com/tools-meters/current-shunt-resistors-100-amp-max.html It's just a calibrated resistor. You then put your voltmeter across it and measure millivolts ...1 mv per amp.
Al Skierkiewicz posted something a while back about using something like 1 ft of #10 wire also dropping 1 mv per amp. Of course it's not as accurate as a calibrated current shunt (above) but it would certainly be fine for breaking in motors. You just measure the voltage across that length of wire in series with the motor wires.
samir13k
04-02-2010, 22:34
Jonathan,
You say you fixed the bearing pushing out easily...was with the AM trnasmission I could see how you might make room. How do us CIM folks do it though?
If you contact Andymark, you should be able to get the replacement bearings that mount flush... another possibility is to grind down the corner of the motor a bit (but i dont reccomend this method, it may classify as modifying the motor.) Number one quick fix i recommend is just to put a washer between the cim and the nano. it should fix the problem
If you contact Andymark, you should be able to get the replacement bearings that mount flush... another possibility is to grind down the corner of the motor a bit (but i dont reccomend this method, it may classify as modifying the motor.) Number one quick fix i recommend is just to put a washer between the cim and the nano. it should fix the problem
Samir is correct, contact AM for the correct bearing. Temporarily you can use washers but I wouldn't' do that in competition.
The Nano we just recieved actually had interferance between the internal hex of the output shaft and the first stage gear. They were literally hitting each other and locking up. We had to remove the output shaft and sand off the corners of the hex to free it up. Make sure you don't have this problem, although I'm sure you would know it if you did. Is it noisey? (Noisier than usual that is.)
You are all correct. Andy Baker suspects that what's happening is the thicker shielded bearing (a FR6ZZ) when clamped down by the bolts holding it in for that axle, is causing things to bind internally and the current to go through the roof. The thinner unshielded bearing, a FR6 (http://store.andymark.biz/am-0027.html) is what's needed.
Just a quick update on two observations after receiving our NANOs over the weekend.
First, we used a 5/8" retaining ring to fill the "wiggle" on the last stage output shaft. It slipped right over the hex shaft and was the perfect thickness to reduce the wiggle but still be free of binding.
Second, we noticed that there is also a little slop in the first 50 tooth input gear that the CIM pinion mates with. This was causing the gear to contact the two washers on the CIM shaft for positioning the pinion. This caused significant binding and may be the cause of the high current draw that some people have observed. The solution was to assemble the CIM pinion with only one washer behind it.
After assembly we ran in for 15 minutes and the gearbox was humming along with the CIM only drawing 2.4 amps!
We are direct driving our kicker off of the NANO and have made many kicks so far with no signs of wear or tear. The thing works beautifully!
Rob
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