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-   -   CIM direct drive (http://www.chiefdelphi.com/forums/showthread.php?t=67668)

gburlison 14-05-2008 21:42
Re: CIM direct drive
 
McMaster sells metric broaches and metric drill bits. Start with a sprocket that is undersized and enlarge the bore with the metric drill and then broach with the 2mm broach. Not sure how many sprockets you will find with a bore of 8mm (5/16") or less.

RyanN 14-05-2008 21:58
Re: CIM direct drive
 
In the past we've directly put a sprocket on a CIM, but it went to a larger sprocket that went into our custom 2 speed transmission. We never really had trouble with the setup, but the more chains you get, the more master links that can fall out... (IRI 2006 right before alliance picking). AndyMark products are nice and reliable, but they are a bit expensive ($88 for the toughbox that shipped in the KOP). Banebots are still pretty expensive... the cheapest is $83. I'm not sure of your ability to build your own parts with a mill or CNC mill, but custom is probably the cheapest way to go, but also the most time consuming. Chain's are probably the easiest way to go, but their reliability becomes the issue. Gears are the hardest way to go, but their reliability is among the best.

Keep in mind that from 2003 to 2006 we used chains in our custom transmissions and had very little problems, but the problems we had were with the chain derailing or the master links falling out. The chain never broke and we used #25 chain. You may also look into regular bicycle chain as it is easy to find and fairly cheap. We've been looking into bicycle chain as an option next year because we are stretching the limits of the #25 chain as far as the forces we apply to it. Luckily with our 4 CIM drive this year, we had no drive train issues at all (knocks on wood for IRI)

s_forbes 14-05-2008 23:00
Re: CIM direct drive
 
Quote:
Originally Posted by squirrel (Post 748191)
Did you grind flats on the motor shafts, for the set screws to seat against?
I think a modification to the motor shafts is illegal dad... gosh, read the manual! :)

RyanN 14-05-2008 23:05
Re: CIM direct drive
 
Quote:
Originally Posted by s_forbes (Post 748264)
I think a modification to the motor shafts is illegal dad... gosh, read the manual! :)
Actually, modifying the shaft is not illegal.

Quote:
<R61> So that the maximum power level of every ROBOT is the same, motors used on the ROBOT shall not be modified in any way, except as follows:
  • The mounting brackets and/or output shaft/interface of the motors may be modified to facilitate the physical connection of the motor to the ROBOT and actuated part.
  • The gearboxes for the Fisher-Price and Globe motors are not considered “integral” and may be separated from the motors.
  • The electrical input leads on the motors may be trimmed to length as necessary.
The intent is to allow teams to modify mounting tabs and the like, not to gain a weight reduction by potentially compromising the structural integrity of any motor. The integral mechanical and
electrical system of the motor is not to be modified. Note that FIRST will not provide
replacements for modified parts.

Manoel 15-05-2008 00:19
Re: CIM direct drive
 
Quote:
Originally Posted by Cory (Post 748159)
we had a heck of a time keeping our pinions in place this year. Due to having 2 gears on one CIM shaft we had no room to use retaining clips like we usually do and we had to rely on a setscrew to keep the gear from moving. Even with 2 set screws 90* from each other the gears would slide out and eventually maul themselves on the adjacent gear. We had to resort to green loctiting them, which didn't work well either when we didn't let it set for 24 hours.

Furthermore the only way to release the loctite is heat. I melted a bit off one of our Delrin sideplates the other day trying to break a stubborn one free.

We hate setscrews and figured this was probably one application where they might be OK. Lesson learned-never again will we rely on them.
We've had problems using M3 setscrews to hold a gear to the CIM shaft (mainly because the small allen key prevented us from tightening the screw properly) but switching to M4 setscrews completely solved our problem (both last year with a high torque, two-speed gearbox and this year with a single, high speed gearbox).

Doug G 15-05-2008 00:49
Re: CIM direct drive
 
We have used 5/16" bored gears/spockets and a 3/32 keyway. With a little filing, they fit right on the 8mm CIM shaft and then get a piece of 3/32 key and file it to fit. We've made 3 types of transmissions this way and also used this method for our ball shooter in 2006 which used #25 sprockets mounted on the CIM shaft. Never had a failure... yet.

Cory 15-05-2008 02:00
Re: CIM direct drive
 
Quote:
Originally Posted by Manoel (Post 748282)
We've had problems using M3 setscrews to hold a gear to the CIM shaft (mainly because the small allen key prevented us from tightening the screw properly) but switching to M4 setscrews completely solved our problem (both last year with a high torque, two-speed gearbox and this year with a single, high speed gearbox).
We had one gear with a 4-40 and one with a 6-32. Both performed equally poorly.

Brandon Holley 15-05-2008 08:51
Re: CIM direct drive
 
Quote:
Originally Posted by Cory (Post 748159)
we had a heck of a time keeping our pinions in place this year. Due to having 2 gears on one CIM shaft we had no room to use retaining clips like we usually do and we had to rely on a setscrew to keep the gear from moving. Even with 2 set screws 90* from each other the gears would slide out and eventually maul themselves on the adjacent gear. We had to resort to green loctiting them, which didn't work well either when we didn't let it set for 24 hours.

Furthermore the only way to release the loctite is heat. I melted a bit off one of our Delrin sideplates the other day trying to break a stubborn one free.

We hate setscrews and figured this was probably one application where they might be OK. Lesson learned-never again will we rely on them.
We ran into a similar problem in our 3 motor gearbox. Because we did not have enough clearance to extend the shaft to add a retaining ring we had to resort to some old school methods....superglue works wonders sometimes. It is by no means the most elegant solution, but we did not need a set screw, retaining ring, or anything but superglue to hold the pinions on the CIM motors and AM FP planetaries. You don't need heat to remove them either (although I'm sure a little heat wouldn't hurt), a quick pop with a screwdriver or chisel will break the superglue and the pinion will come right off.

Manoel 15-05-2008 22:30
Re: CIM direct drive
 
Quote:
Originally Posted by Cory (Post 748291)
We had one gear with a 4-40 and one with a 6-32. Both performed equally poorly.
I forgot to mention that the hole was collinear with the keyway such that the setscrew had a flat surface to press against.

Did you guys do it different?


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