How to Mod the Green CHM

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Re: How to Mod the Green CHM

Postby jbizub5192 » January 23rd, 2012, 1:23 am

Hmm. Mine doesnt stop the brushes at all, it keeps moving but every so often (about every 3-5 secs) I will hear clunk. But I dont hear the brushes reverse at all.
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Re: How to Mod the Green CHM

Postby Gordon » January 23rd, 2012, 5:11 pm

jbizub5192 wrote:Hmm. Mine doesnt stop the brushes at all, ... every so often (about every 3-5 secs) I will hear clunk. But I dont hear the brushes reverse at all.
Please describe differences in the sounds of what we should hear between main brushes turning in their normal direction vs. their reverse direction.
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Re: How to Mod the Green CHM

Postby jbizub5192 » January 23rd, 2012, 6:01 pm

Sorry I should have made that clearer. I dont know what it sounds like in reverse but Im almost positive i would hear a difference in sound. Plus there is no pause at all that would indicate it is turning a different direction. Also I get the clunking noise about every 1-2 sec not 3-5. It doesnt do it all the time, sometimes it will do it during a sharp turn or going straight but not all the time. This is my second time using the bot with the mod and it does seem to be much better then yesterday. Its probably about 60% of the time not making the clunk noise. It does not stall ether. Thanks again for the help
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Re: How to Mod the Green CHM

Postby jbizub5192 » January 23rd, 2012, 6:30 pm

I also did the diagnostic test and ran the brush test and and I was able to have it stopped on the carpet with the brushes turning without any clunking noise. I even pushed down on the bot a good amount before I could hear the motor strain and then shut off. So im wondering if its something with the brush deck adjustment cabe/wire?
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Re: How to Mod the Green CHM

Postby Gordon » January 23rd, 2012, 6:36 pm

jbizub5192 wrote:... I dont know what it sounds like in reverse but Im almost positive i would hear a difference in sound.
Yes, it is natural that there will be some changes to the sound of a reversed motor & gear-train, however, I am almost positive that very few people on earth would be capable of confirming that a 500's brush-deck had reversed its brushes' rotation -- just by listening!
Plus there is no pause at all that would indicate it is turning a different direction.
The only pause occurs just before you hear the "clack". There will be a forward direction clack after the motor winds up the vertical cable and slams the deck against the CHM-frame's upper travel stops. At that point the robot switches the motor into reverse, which allows the motor to rapidly unwind itself from the high-limit, to send down the deck to crash into the deck's lower travel limit.
Also I get the clunking noise about every 1-2 sec not 3-5. It doesnt do it all the time, sometimes it will do it during a sharp turn or going straight but not all the time.
Results like that suggest you are operating Roomba in a borderline high region of motor current while it endures no floor sweeping loading. Make it do a bit of real work and current rises too high (evidenced by the deck motor winding up its cable), causing the robot to object!
This is my second time using the bot with the mod and it does seem to be much better then yesterday. ...
Don't expect this condition to heal itself. IMO, you have installed ball-bearings with too much radial preload applied to them. They are just as likely to wear out prematurely as to wear in to a happy life. Plan on examining the press fits that you applied to BBrgs' inner and outer races. If any are more than a few ten-thousandths of an inch, it would be prudent to re-fit them.

During that re-work operation, you should also verify that as you finger rotate the mounted gear train you sense no appreciable variation in applied torque as each of the two BBrg-fitted gears rotate through one revolution.
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Re: How to Mod the Green CHM

Postby Gordon » January 23rd, 2012, 6:49 pm

jbizub5192 wrote:... So im wondering if its something with the brush deck adjustment cabe/wire?
At this instant I am fairly certain your CHM-fault is due to a cockpit problem.

For example: Are you aware that a Roomba operating in its BiT-Mode is doing so with almost all of its safety features shut off, or diverted to supporting testing rather than to protecting the robot?
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Re: How to Mod the Green CHM

Postby jbizub5192 » January 23rd, 2012, 8:34 pm

Thanks for all the info! Im pretty sure I would hear it because i am very sensitive to sounds and could pick up the slightest noise or change in noise. I just ran it for over a hour and the clunking noise was on and off like I said. But with the clunking noise happening every 1-2 seconds could it really do that for over a hour? I would be shocked if the pause is so silent. Also the roomba constantly is moving, it never randomly pauses while moving. If i under stood you correctly you think the bearings are pressed in to tight? The first time i ran the bot after the mod it was much harder to turn the brushes so i then disassembled the gearbox again and made the holes purposely bigger to the point where i had to add some epoxy. This way i know they wouldn't be in to tight. But unfortunately that didn't help much, it still made the clunking noises but not as bad. I did notice though that bearings I revived from vic were a little rough and stiff as soon received them in the mail. Could the bearings be partly at fault? Thanks again for all the help I really appreciate it.
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Re: How to Mod the Green CHM

Postby vic7767 » January 23rd, 2012, 9:12 pm

Send me an email and I'll send you a replacement bearing set. The sealed ball bearings that I offer are not difficult to turn by hand. Most owners that attempt the ball bearing mod don't have the equipment to evaluate their work when the mod is complete. Basically the mod should not increase the power requirements needed to spin the brushes and gear assembly above .5 amps. At 14 volts dc the motor should spin the brushes (no load) at .30 to .45 amps. You begin getting into the clicking option when the power requirements go above .65 to .75 amps.
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Re: How to Mod the Green CHM

Postby Gordon » January 23rd, 2012, 10:23 pm

jbizub5192 wrote:...If i under stood you correctly you think the bearings are pressed in to tight? ... so i then disassembled the gearbox again and made the holes purposely bigger to the point where i had to add some epoxy. This way i know they wouldn't be in to tight. ...
Did you forget to attend to the bearings' inner races? They can also be stretched out of shape by excessive mismatch of diameters.

Be sure you perform the electrical check that vic defined for you before tasking Roomba to power your ailing CHM.
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Re: How to Mod the Green CHM

Postby jbizub5192 » January 23rd, 2012, 11:21 pm

Thanks vic7767! I will definitely be making future purchases from your store! Your the best.. I unfortunately dont have any way two test it. My 14 volt drill battery just died recently and would have been perfect for testing along with my multimeter. I then upgraded to 18v drill. I might have a 14volt power supply though. What should the max amp output be? I dont want to fry the motor. Yep I did the inner races also. I wish it was that easy though lol. Thanks again for everyones help!

Moderator note: Deleted email address, vic7767 has it.
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Re: How to Mod the Green CHM

Postby vic7767 » January 23rd, 2012, 11:33 pm

Sometimes the USPS is unkind to the bearing sets thanks to the machinery used. I would not go above 1 amp in testing the brush motor.
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Re: How to Mod the Green CHM

Postby jbizub5192 » January 23rd, 2012, 11:40 pm

Yea thats defiantly a good point about the machinery. Ok ill stay below 1amp. Thanks
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Re: How to Mod the Green CHM

Postby mfortuna » January 24th, 2012, 12:16 am

You should not publically display your email address. Spammers could find it and target you. I recommend using a PM to send information like an email address.
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Re: How to Mod the Green CHM

Postby jbizub5192 » January 24th, 2012, 1:23 am

I completely forgot about that! thanks
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Re: How to Mod the Green CHM

Postby victor560 » January 25th, 2012, 11:22 am

I keep hearing the question
why doesn't Irobot put sealed bearings in the CHM.

the obvious answer is that it costs more.
now you have to take another couple of steps
before it makes sense.

sealed bearings fail for the very same reason
the original plastic shield/bearing fails.
lack of proper attention to the brushes.

both will fail if one does not maintain the area involved.
So...
which is cheaper to replace under a warranty?

Roomba needs to declare the cleaning head a user servicable part.
It wouldn't hurt to lower the price a bit also.

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Re: How to Mod the Green CHM

Postby vic7767 » January 25th, 2012, 1:53 pm

It IS a user serviceable Module and is replaceable. While the Roomba is under warranty it is free to the owner. This question has been asked for over 7 years.
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Re: How to Mod the Green CHM

Postby TechGuy » January 25th, 2012, 1:55 pm

victor560 wrote:both will fail if one does not maintain the area involved.
So...
which is cheaper to replace under a warranty?

:agree: Ball bearings mod does not solve all the CHM problem. With the mod, it is easy to maintain by replacing the failed ball bearings without cleaning the gears in the CHM.

Roomba needs to declare the cleaning head a user servicable part.
It wouldn't hurt to lower the price a bit also.

For the 500 and 700 series Roomba, the CHM is an user replaceable part.
Charging battery directly: 400 Series, 500 Series,.H-Bridge Repair How to Desolder
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Re: How to Mod the Green CHM

Postby victor560 » January 25th, 2012, 3:18 pm

Hi techguy,
From what I have heard from a few people,
is that If they have to pick up a phillips head screw driver
then a tech/repair person is involved...
user servicable is pop the filter out and replace.
I know it is all of 8 screws to replace.

vic7767
believe me when I state I know the question
has been looked over quite a while.

I am an inveterate tinkerer and people bring things to me to repair.
I discovered you about a week after my first 530 arrived
.... gick... 4 or so years ago.
in the time since, I have repaired and cleaned some roombas.
I do not see roombas from people who can pick up a screw driver
and know what it is.

maybe the solution is to have Irobot build the
"we let the engineer's loose" edition.

In the time while we await that happy event,
I want you to know that I have tried the sealed bearings
and I think them worth doing.

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Re: How to Mod the Green CHM

Postby TechGuy » January 25th, 2012, 5:22 pm

victor560 wrote:Hi techguy,
From what I have heard from a few people,
is that If they have to pick up a phillips head screw driver
then a tech/repair person is involved...
user servicable is pop the filter out and replace.
I know it is all of 8 screws to replace.
victor560


Yes, almost - the total should be 9 screws.
1 - side brush screw
4 - bottom plate screws
4 - CHM screws.

No tech/repair is required. Buy a new CHM from iRobot or eBay and replace it yourself.
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Re: How to Mod the Green CHM

Postby vic7767 » January 25th, 2012, 5:26 pm

victor560, welcome to the tinker/mod forum. The present 500, 600, and now 700 Roombas are an engineers dream to me. They are modular and not extremely difficult to tear down and repair.

The monster on the horizon to me is the Neato. That robot in its present state is engineer unfriendly (IMO). And I'm looking forward to better designs.
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