Globe transmission with other motor(s)

[billbo911]

Forgive me if this has been addressed elsewhere. Searching did not seem to address my exact question(s). If this has been addressed, please point me in the right direction.

With the huge delay in getting P60 transmissions from Banebots, we are looking elsewhere for a rugged solution for transmissions to use on a roller claw.
There are a couple options already posted, but many of these alternatives seem to all have issues with reliability. Stripped gears seem to be the biggest culprit. Here is an example. (http://www.chiefdelphi.com/forums/showthread.php?t=91419)

With that lead in, here is what we would like to do. We have several Globe motors from previous years. The motors may not be legal this year, but I believe the transmissions are. Additionally, the transmissions seem to be quite robust. If we can interface a 395/540/550 to the traansmission, I think we will have a nice solution.

Here is the issue we need to overcome: The pinion that is currently on the globe motor has an ID that is noticeably larger than the shaft on the three motors listed.

Option 1) Make a sleeve to go between the motor shaft and the pinion.
Option 2) Locate a pinion that will fit, or can be drilled to fit, the motor shaft and drive the transmission.

Has anyone successfully performed either of these options?
If not, what other options might we have to solve this problem?

[Dad1279]

What target rpm are you shooting for?

We geared up a window motor with a belt. Simple, reliable, easy to mount to flat side of our gripper.

[billbo911]

What target rpm are you shooting for?

We geared up a window motor with a belt. Simple, reliable, easy to mount to flat side of our gripper.

Definitely an alternative we are considering. We will be using two, so weight is now becoming an issue.

[Dad1279]

Definitely an alternative we are considering. We will be using two, so weight is now becoming an issue.

Does your design need 2 motors? We change direction for the lower roller by crossing a belt. Can also be done with gears.

Back to your original q., If you have the machining capabilities, I would make a sleeve for the pinion. I don't think globe pinions will be easy to find.

Off hand I don't know what material the pinions are, but if they are brass of steel, you could probably have the center holes brazed/welded closed, and re-drill.

The best solution really depends on the machining capabilities of your team.

[billbo911]

Does your design need 2 motors? We change direction for the lower roller by crossing a belt. Can also be done with gears.

Back to your original q., If you have the machining capabilities, I would make a sleeve for the pinion. I don't think globe pinions will be easy to find.

Off hand I don't know what material the pinions are, but if they are brass of steel, you could probably have the center holes brazed/welded closed, and re-drill.

The best solution really depends on the machining capabilities of your team.

Our desire is to have two motors so that we can re-align a tube if it is not tilted the way we would want it.

We can definitely make a sleeve for the motor shaft, I just wasn't sure if that would be a good solution. I calculated the max torque and we should be well under .25 ft lbs at the motor shaft with a RS540 and under .4 ft lbs with a RS550. I just want to make sure we don't have a failure at that point because of a sleeve design. I guess with enough of an interference fit, we should be good.

[clayman]

Although we only had it on our robot for three matches, our roller claw worked without a hitch using the 395 and Black and Decker electric screwdriver combination.

[billbo911]

Although we only had it on our robot for three matches, our roller claw worked without a hitch using the 395 and Black and Decker electric screwdriver combination.

This is good to know. I never have heard if the BD's were solid or weak.

So, why only three matches?

[ratdude747]

This is good to know. I never have heard if the BD's were solid of weak.

So, why only three matches?

i can attest that the cheapo 18v firestorm trannies are so-so at best. if you are going to use drill trannies, go dewalt.

[clayman]

This is good to know. I never have heard if the BD's were solid or weak.

So, why only three matches?

I was troubleshooting the type of belting I was using for the majority of my free time at the Detroit regional at Wayne, and the roller claw was only ready to put on for the last three matches. Lesson learned: never buy thick, pre-sized belts.

As far as the sturdiness, I only had issues when I put the motor into a situation that I couldn't turn by hand easily, in which case the gears in the box would pop out of place (they can easily be put back). I mounted it with a couple of screws through the casing and electrical tape onto an long angle bracket I made. As far as the drive connection, I hammered a regular locking screwdriver bit into one of our rollers (1/4" hole), the hex of the screwdriver bit holds it in place. The roller-screwdriver bit combo then just clicks into the BD.

As you can guess, this was a lot of trial and error.

[billbo911]

OK, I may have found a solution.
Today I finished a mash-up of a RS-395 and a Globe transmission. It actually fits together fairly well, but I did use a lathe to trim down the motor mounting plate.

It runs quite smoothly. I also see no reason that a RS-540 or RS-550, and maybe even a RS-775, couldn't be mated up as well.

I will post up pictures tomorrow.

For now, here are some specs:
With RS-395 132RPM 7.8lb ft max torque.
With RS-540 143RPM 18.5lb ft max torque.
With RS-550 164RPM 32lb ft max torque.

These values are based on the following:
117:1 reduction.
76% Efficiency.
Max Torque Spec. 12.5lb ft. (This is an odd spec because from the same sheet, the factory motor produces 16.6lb ft :cool: )

BTW, I forgot to mention, with the RS-395, this mash-up saves 130 grams compared to a window motor. You gain 45 RPM and maintain the same torque!

[Don Wright]

Avoid the 775's...

[Kevin Sevcik]

Ahhh, too late for suggestions, then. Still, I suspect you've discovered that a press fit is easily enough to hold your pinion in place. I was going to suggest you make it easier on yourself and get the pinion nice and hot with a torch before you press it, but you've apparently managed.

Other option is hunting up the gear, as you've said. The tricky part is determining whether it's inch or metric, not finding the DP or a supplier. Suppliers are easy: SDP-SI (http://sdp-si.com) or WM Berg (http://wmberg.com)

[Brandon Holley]

Avoid the 775's...

...at all costs...

[billbo911]

Avoid the 775's...

...at all costs...

Agreed!

[MrForbes]

775 motors would be good candidates for students to disassemble to see how motors work inside. Make sure they destroy them in the process.

[billbo911]

As promised, here is a breakdown of what was done to mash-up an RS-395 and a "Globe Motor" transmission.

The first steps are fairly self explanatory, and I don't have pictures of those steps.

Start by knocking the three roll pins in to release the transmission from the motor. Once the pins are in, just wiggle the two halves apart. For now, set the transmission aside, preferably with the output shaft down so the gears don't fall out.

At this point, you need to remove the pinion from the motor shaft. I settled for the double screwdriver prying method. This will most likely kill the motor for any future use. But once you remove the motor mounting plate, you will realize the motor mounting plate is an integral part of the motor too. So, that motor was going to be useless anyway.

Once you have the pinion off, remove the two torx head screws. The right tool is best, but careful use of an allen wrench will do the trick.

OK, now turn the mounting plate over and remove the retaining clip that is holding the bushing into the plate. It pops right out with just a little tug from some needle nose pliers.

Now the real fun begins. It's time to decide if you need to turn down the back side of the mounting plate or not. It will all depend on the length of the mounting screws you choose to use and how long the motor shaft is.
I chose to turn the plate down so the entire back was on the same plane as the outer rim.

http://billbo911.smugmug.com/Hobbies/2011/2011-03-2415-50-5085/1227688391_JQ8Vn-L.jpg

The next step will also be based on how far you turned down the back of the plate. If the center section of the motor prevents the motor from mounting flat against the plate, you may need to drill the plate out to allow it to fit correctly.

While you are drilling the plate, add two holes for your mounting screws.

http://billbo911.smugmug.com/Hobbies/2011/2011-03-2415-50-17588/1227689176_yEKMJ-L.jpg

OK, go ahead and mount the motor on the plate, I know you want to.

Also, take note of the difference in diameter of the motor shaft and the pinion's ID. You will most likely need to make a sleeve to mate the two together.

Start by turning a piece that is .002" larger than the ID of the pinion. Now press the pinion onto that piece. Press it in until the shaft is flush with the surface of the pinion. Cut the other end of the shaft so it extends about .050" out of the pinion. Now you will need to drill out the center of the shaft to about .002" smaller than the motor shaft. (These press fitting measurements work well with 6061 aluminum and the RS-395 motor, YMMV.)

Now line up the motor and the pinion. Make sure everything is square, don't forget to press against the back of the shaft, not just the motor. Press the pinion on until the face of the pinion away from the motor is approximately .375" from the flat surface of the motor mounting plate.

http://billbo911.smugmug.com/Hobbies/2011/2011-03-2415-50-30976/1227688804_KvSse-L.jpg

OK, align the holes in the transmission to the holes in the mounting plate and wiggle the two together. Once it is together, knock the roll pins back into the holes and make them flush with the outer surface. It should now look something like this.

http://billbo911.smugmug.com/Hobbies/2011/2011-03-2415-45-06805/1227689758_YXmmp-L.jpg

The best part of this is that the transmission is bullet proof. This rig is 130 grams lighter than a window motor. It gives you the same torque and 45 RPM more, too.

[JesseK]

/favorited

[PAR_WIG1350]

775 motors would be good candidates for students to disassemble to see how motors work inside. Make sure they destroy them in the process.

:eek: I feel like I missed something. Any explanation (videos preferred if epic failure is involved) for such resentment towards the RS-775 (which I have just decided to rename the RS-sev sev)?

[Doug G]

:eek: I feel like I missed something. Any explanation (videos preferred if epic failure is involved) for such resentment towards the RS-775 (which I have just decided to rename the RS-sev sev)?

Many folks are finding the rs775s case shorted. You must check em out thoroughly, burn them in, before using them.

@Bill, great job! I saw some other teams at sac doing the same thing. We too are using rs 550s and p60, 64:1 gearboxes on our roller claw and haven't noticed any problems. When did your original gearboxes start showing wear and tear?

[MrForbes]

Somewhere on CD there's a long thread about the problem with "case shorts" on the RS-775 motors. I disassembled a motor that showed about an ohm resistance between the case and the terminals. The problem that I found was that the insulation on the armature failed and allowed the winding to short to the armature. This is an unacceptable condition in a motor, and many teams have found that their motor(s) are shorted this way. Banebots has not offered to replace them.

[PAR_WIG1350]

The case short issue is definitely annoying, but it is no reason to completely avoid the sevsev. It is still the second most powerful motor we can use.

[MrForbes]

If your robot design needs them, then go for it. We figured out how to do what we needed with window motors. No hassle at all.

[PAR_WIG1350]

Somewhere on CD there's a long thread about the problem with "case shorts" on the RS-775 motors. I disassembled a motor that showed about an ohm resistance between the case and the terminals. The problem that I found was that the insulation on the armature failed and allowed the winding to short to the armature. This is an unacceptable condition in a motor, and many teams have found that their motor(s) are shorted this way. Banebots has not offered to replace them.

Wait, FAILED? As in NOT a factory defect? If a motor is not shorted out now, assuming the possibility of developing a short is a significant issue, what are the chances of it shorting out during the season?

[MrForbes]

The motor I took apart was shorted right out of the box. We never applied power to it, aside from an ohm meter.

Read the thread, see what you think. Check the resistance of your motors after using them for a while.

http://www.chiefdelphi.com/forums/showthread.php?t=91733

[PAR_WIG1350]

The motor I took apart was shorted right out of the box. We never applied power to it, aside from an ohm meter.

Read the thread, see what you think. Check the resistance of your motors after using them for a while.

http://www.chiefdelphi.com/forums/showthread.php?t=91733

Thanks, I know that and they have already been checked, only one bad one:) . I just wanted to make sure they would stay the way they are.

[billbo911]

Many folks are finding the rs775s case shorted. You must check em out thoroughly, burn them in, before using them.

@Bill, great job! I saw some other teams at sac doing the same thing. We too are using rs 550s and p60, 64:1 gearboxes on our roller claw and haven't noticed any problems. When did your original gearboxes start showing wear and tear?

Doug,
The RS-395 and Globe transmission actually an experiment. We wanted to test it out to see if it would be a workable alternative for a roller claw we are building to take to St. Louis. As it turns out, it is .25 inches too long. Instead we will be direct driving rollers with window motors on "Claw 2.0".

We got burned by Banebots not delivering on time. Then after hearing about the failures the P60 is experiencing, we wanted to avoid them like the plague. With the minimal load a roller claw sees, the RS550 P60 combo should be fine. But, if it would be used in a heavier load situation, then the P60 is out and the Globe is in.

This bad-boy may not see any use from us this year, but it's good to have as an alternative in the future.

[s_forbes]

Very nice modification! It's great to see a planetary gearbox alternative that a lot of veteran teams already have laying around.

Seems a little blurry to me on the rules though this year... Is this considered modification of a COTS item? I didn't think that anyone sold these motor/gearboxes anymore.

R29 is a neat rule this year that allows use of past robot components and COTS items that aren't sold anymore, but gives the impression that you can't modify them if you intend to use them on your robot.

COTS items from ROBOTS entered in previous FIRST competitions or COTS items that are no longer commercially available may be used under the following conditions:
A. The item must be functionally equivalent to the original condition as delivered from the VENDOR (e.g. a part that has non-functional label markings added would be permitted, but a part that has device-specific mounting holes added would be prohibited), and
B. The item must satisfy ALL applicable 2011 FRC materials/parts use rules.

[Mike Betts]

Very nice modification! It's great to see a planetary gearbox alternative that a lot of veteran teams already have laying around.

Seems a little blurry to me on the rules though this year... Is this considered modification of a COTS item? I didn't think that anyone sold these motor/gearboxes anymore.

R29 is a neat rule this year that allows use of past robot components and COTS items that aren't sold anymore, but gives the impression that you can't modify them if you intend to use them on your robot.

Steve,

It must be in an unmodified form before kickoff (it can not have been modified in a previous season). However, I believe that modification during the season is permitted under <R29>...

JMHO,

Mike

[Tristan Lall]

Very nice modification! It's great to see a planetary gearbox alternative that a lot of veteran teams already have laying around.

Seems a little blurry to me on the rules though this year... Is this considered modification of a COTS item? I didn't think that anyone sold these motor/gearboxes anymore.

R29 is a neat rule this year that allows use of past robot components and COTS items that aren't sold anymore, but gives the impression that you can't modify them if you intend to use them on your robot.Good catch on the rule question. I think you're right; if not commercially-available any longer, <R29A> says they must be unmodified—which they aren't—and <R29B> says they must obey other rules—of which the motor rules <R46> and <R47> seem to be pertinent. (There is some question about whether modifying a motor such that it is incapable of being used as a motor renders it permissible for use this season.)

I'm not sure what the GDC was intending with this rule. Is there something special about formerly-COTS parts that necessitates their being left unmodified? Perhaps a concern that teams would re-use particular fabricated items from old robots? (Not that I think this rule would be the logical response to that; I'm just speculating.)

[Brandon Holley]

Thanks, I know that and they have already been checked, only one bad one:) . I just wanted to make sure they would stay the way they are.

We installed 775s that did not show any issues right out of the box and after running them for a short while, the short presented itself. I would not feel comfortable with 775s on my robot at all. At any point the short can occur and cause huge potential issues.

We use 2 servos to release our minibot. One to release the deployment system and one to actually launch the minibot. The 775s would cause grounding issues throughout the entire robot because they were directly interfaced to the frame. We tried completely isolating the motor and gearbox from the frame by adding thin electrical tape in between and also switching to plastic screws, but this did not work. The pinion is still directly connected to the frame through the other gears.

When we would run our elevator at full speed it would cause the servos to move around as if they were getting a dirty signal. If we ran our elevator full speed from ground to top peg it would drift the servos enough to release our deployment system. Needless to say this is an extremely frustrating problem.

We are removing the 775s from our robot for Boston. It's simply too big of a risk/headache to continue using them.

Your mileage may vary however.

-Brando


/sorry for thread jack

[billbo911]

Very nice modification! It's great to see a planetary gearbox alternative that a lot of veteran teams already have laying around.

Seems a little blurry to me on the rules though this year... Is this considered modification of a COTS item? I didn't think that anyone sold these motor/gearboxes anymore.

R29 is a neat rule this year that allows use of past robot components and COTS items that aren't sold anymore, but gives the impression that you can't modify them if you intend to use them on your robot.

Steve,

It must be in an unmodified form before kickoff (it can not have been modified in a previous season). However, I believe that modification during the season is permitted under <R29>...

JMHO,

Mike

Good catch on the rule question. I think you're right; if not commercially-available any longer, <R29A> says they must be unmodified—which they aren't—and <R29B> says they must obey other rules—of which the motor rules <R46> and <R47> seem to be pertinent. (There is some question about whether modifying a motor such that it is incapable of being used as a motor renders it permissible for use this season.)

I'm not sure what the GDC was intending with this rule. Is there something special about formerly-COTS parts that necessitates their being left unmodified? Perhaps a concern that teams would re-use particular fabricated items from old robots? (Not that I think this rule would be the logical response to that; I'm just speculating.)

These are all really good points. The one thing that makes this mash-up questionable to me in light of these rules is the interface plate.

On the Globe motor/transmission these two items are actually one. The plate is both the motor end plate and the motor mount to the transmission. I think, or should I say I know, that this is a gray area and would definitely take a ruling from the GDC to see if it is legal or not. For us this year, it is not an issue as we will not be using it. That said, I'll post the question to the GDC today and see if they can make the answer clear according to this years rules.

[PAR_WIG1350]

If a 775 were completely isolated from the frame, how much will a case short effect motor performance if left alone (as in not 'zapped' to 'clear debris')?

I wish I had the chance to gain more experience with the globe motor. I've only heard good things about it. The 775, on the other hand...

[billbo911]

Just as a follow up on this thread:

I asked the GDC via the Q&A site about the legality of this combination. Unfortunately, the Q&A closed right after I posted the question and never received a response.

We brought this motor and transmission with us to St. Louis. When I found an inspector that had a few free minutes, I showed him the motor and asked him if he believed it would be legal to use.

We bantered back and forth a bit, I told him of all my concerns and where I thought it might be illegal. He was able to convince me that as long as it was unmodified prior to the season and had been a KOP item in the past, then it was legal!

Good to know.