LB3200 Blade Motor Brush Replacement

[jzawacki]

Ok, I put some info on my Lawnbott Wiki (feel free to create an account and add info if you like) about replacing the brushes for the blade motors..

Blade Motor Brush Replacement

[prb238]

jzawacki - I've seen documentation that recommends that motor brushes get replaced every year.  Are you doing it that often?  And are you getting the brushes from Vishal?  How easy is it to replace them?

prb238

[jzawacki]

This will be my first time to replace them.. and it's only because it started making noise.. Looks like I caught it just in time!  After "extending" the brush a little more, my bot is back up and running without issues.  Now, you have to order them through a reseller such as Paradise Robotics, but KA doesn't stock them, so be prepared for a 2 week wait from Italy.

In the article, I mention there are two options.  Just the brushes and a "brush replacement kit".  If you buy the brush replacement kit that I was told doesn't require soldering, I'm assuming it is the complete end cap for the motor, including the encoder board, as everything is soldered to it.  I can't wait to get a hold of this kit, as it would give me an "extra" encoder to RE.  So, in "kit" form, anyone can replace them.. and it will take you longer to take the motor out than to replace the end cap, as it literally only takes a minute and is very easy to do.

If you go with the "brushes only" way, it'll be a little more involved, as the brushes are crimped to the power wires.  The design obviously didn't include brush replacement or these would be attached with screws.  So, you'll have to cut the power wires and solder or re-crimp the power wires to the new brushes.  In either case, it should be a pretty easy job depending on your skill level.

I'd say "kit" is a skill level of 1 (for anyone) and the brush kit, if you have electronics/soldering skills, a level 2 (beginner).

If you look at the pictures, you'll see the end cap and what I believe will be the "kit" form.  I should have taken pictures of the underside of the brush PCB so you could see the crimped wires.. I'll add them (and probably step by step instructions) when I do the real replacement.

BTW, I'm going to see if I can do some modding as well.. if you look at the specs of the motor.. it's really nothing special.  You can find way better motors for a fraction of the cost.. I just need to RE the encoder.  So, we'll see.

[Jerry]

It is great that they are offering replacement brushes to customers. I have never replaced brushes or gears in any motors before but as long as it is not a  long complicated process(I did not figure it could be) I wouldn’t mind either option of replacing parts on the motors myself or paying paradise robotics to do it. Of coarse the more options available to the customer the better. I was wandering if you could list the price of the brushes and brush replacement kit and list the prices of the planetary gears and brushes for the wheel motors if you happen to know them? It would be nice for people to have  an idea of how much it would cost to rebuild all three of there motors every two years or so like mentioned before as preventive maintenance.

[jzawacki]

I was hesitant to mention that.. the "brushes only" is $15 and the "brush kit" is $50.  Though, I would expect me to be able to cross reference the "brush only" kit and find a compatible replacement for less.  Also, keep in mind, if someone else is doing the work, you have to pay for shipping in both directions, which is just wasted fees.

Now, for the gears, I would suggest you just tear down the gearboxes, clean, and then repack with grease.  I just did both of my motors and the metal planetary gears seemed to be holding up just fine after two years of use, but keep in mind, my bot only has 500 hours of total use.

[RoyMercer]

When the brushes are changed, it's important to inspect the commutators. Not treating the commutators and only replacing the brushes will decrease the life of the armature. In some cases it will be detrimental.  Especially on variable load motors like these blade motors where commutator threading is common. The bearings need checked. Faulty (they are too small to start with) bearings can gauld the motor shaft destroying it and put a lot of stress on the entire armature and brushes. Not properly removing or installing the bearings can also gauld the shaft. 

I would never recommend these motors have only the brushes changed. Both springs and brush holder should be replaced every time the brushes are replaced. Just the heat alone will change brush spring tension. The brush holders are very thin. It does not take much for these holders to shift shape and cause friction on a brush.

[jzawacki]

Does that mean you used the replacement "kit"?  Does it include the encoder as I expect?

[RoyMercer]

Mine did not come with the hall effect board. It came with new brushes attached to a new brush board and springs. However it is my understanding you can purchase the same thing with the board for around the cost you posted.

[jzawacki]

So, you purchased the $15 kit that required soldering and received this board: Picture

[AGR]

When the brushes are changed, it's important to inspect the commutators. Not treating the commutators and only replacing the brushes will decrease the life of the armature. In some cases it will be detrimental.  Especially on variable load motors like these blade motors where commutator threading is common. The bearings need checked. Faulty (they are too small to start with) bearings can gauld the motor shaft destroying it and put a lot of stress on the entire armature and brushes. Not properly removing or installing the bearings can also gauld the shaft. 

I would never recommend these motors have only the brushes changed. Both springs and brush holder should be replaced every time the brushes are replaced. Just the heat alone will change brush spring tension. The brush holders are very thin. It does not take much for these holders to shift shape and cause friction on a brush.

Roy: What is a commutator, and what does it mean to 'treat ' them? Can the bearings be re-greased or replaced?
If you need to replace both the brushes and springs, does that mean the $50 kit is the way to go? Would that be the same on the wheel brushes too then I assume?

[AGR]

BTW, I'm going to see if I can do some modding as well.. if you look at the specs of the motor.. it's really nothing special.  You can find way better motors for a fraction of the cost.. I just need to RE the encoder.  So, we'll see.

jzawacki: did you ever find the better motors for less cost?

[jzawacki]

AGR: Yes, but I'm still waiting on my parts.  I'm beginning to get the feeling they are holding out till the motor burns up so they can sell me a new blade motor.. I didn't want to spend the $50 on a test motor until I had the parts to make it work with the bot.. but I'm guessing I'll have to use my old parts when the motor does burn up.  It'll be a retrofit, as the new motor is quite a bit smaller.  I'll have to make adapters for the motor mount, blade mount, and encoder mount.

[RoyMercer]

Yes, the what is in your photo is what I received. It is my understanding the $50 kit is for the Fise brand motors. What ever it is, it will not come with bearings. Most of the bearings need to be pulled with a bearing puller and properly pressed on. It is my opinion that the replacement motors are only lasting 500 hours because they are used motors that someone has only changed the brushes.

Treating the commutators means turning them on a metal lathes taking off a few thousands of an inch or the least amount required to have a perfect surface.

Paradise was working on offering blade motor rebuilds as a service but I  don't know where they are with that at this time.

Brush type motors in a variable load application such as these blade motors is not the right kind of motor to be using for several reasons. Even a brand new motor like this is not going to last more than 2-4000 hours and in some cases less. However Simply changing the brushes is only going to give about a 1/3rd the life you will get out of a proper rebuild.