hankster
02-01-2005, 12:17 AM
Big Jim Greenemeyer gives you detailed tips & tricks to use when aligning the brush hoods on your motor.
Ask Big Jim.
1. Make sure your test brushes are the almost exact size of your race brushes. I used new #766's to test for the #767's I was eventually going to use in the motor. There is only .001" difference is size between the two. With me being a little sloppy in "sighting" down the test brush on the wear mark plus this amount of difference in size, caused one hood on a P2K2 I was doing to be off. The size of the brush determins how much it will shift in the hood. A smaller brush will shift more. A larger one, less.
2. I use a brass brush I bought at a welding supply store to lightly go over the wear mark on the test brush. This blends it in and makes the face solid again so you can see a new wear mark. You can use the same brushes over and over this way. However, eventually, the face will become so distorted from so many wear marks that it will cause the brush to shift differently on the comm than a new brush. As a motor guy who goes through a lot of brushes, this is not a problem, usually. But I found this out when I was trying to be cheap and using the same pair over and over for many motors. I could have just put those brushes in a new motor before they got so distorted and then used an new pair for testing again.
3. Make sure your test brushes have the same radius on the face as your race brushes, or close, Using Reedy #766's for test brushes with a wide radius won't work well if your race brushes are Trinity #4499's with a real tight radius.
I remember someone on the discussion boards saying they used a brush with a flat radius for testing. Well, there's two problems with that. First, the comms reaction to a flat faced brush is different that it would be on a brush with the right radius, causing it shift a more or less amount in the hood. Second, the only brush I know of with a flat face are the large copper shunt brushes that come with a new "non-pro" stock motor. They are so large they don't shift near as much as the better compound brands. This could cause your readings to be way off.
This is important. When the brushes are aligned properly on the comm, there is no blackened area on the trailing edge of the brush. The brush wears cleanly and evenly.
4. Make sure the hood screws are tight each time you check alignment. To facilitate doing aligning quickly, I sometimes leave the hood screws looser than I should. Then when I put the motor on the T30 to run for a few seconds to check alignment, just the weight of the alligator clips and the vibration of motor causes the hoods to shift slightly (and unnoticably) from where I had them. If this happens once or twice in aligning a particular motor, it really screws you up.
5. It's not a good idea to use "used" brushes for testing alignment. Unless that worn radius is pretty much in the center, it will throw off the amount the brush shifts and your readings will be off.
6. You can size the hoods around your alignment bar by squeezing gently with a pair of wide jawed pliers against the sides of the bar. However, I don't advise doing this to Epic motors because the brush dampener is on the top of the hood. It gets bent too in the sizing process. If this type of dampener is not able to move around and center itself with the brush, it could cause a brush to hang. Reedy Yokomo's and some other motors made by Sagami have a lower plate that contains the dampener. Since the dampener is completely separte from the hood, you can resize all you want without effecting it.
7. When re-sizing, don't make the fit too tight. Remember, different metals expand at different rates. When the motor gets hot and this happens, the brushes expand more than the hoods because they're hotter. If things are too tight in there, you could hang a brush.
8. And lastly, The alignment will change as the brush wears because it's not supported as well by the hoods. The more the brush sticks up in the hoods, the better it's supported. The better it's supported the less it shifts. This is the reason there is so much brush shifting on an MVP. There is a large distance between the hoods and the comm.
For years, I have said that I wish the spring post had a slot in the top so the post could be loosened and retightened while the motor is running. Using the arcing to test alignment is pretty much fool-proof. Well, not really because fools are so ingenuis. I sometimes do this to my personal motors but not for production. I don't think the r/c community is really ready to see slots cut with a Dremel in the spring posts on a new motor.
If someone is reading this and you have no idea what we are talking about, these tips are used in the procedure of aligning the brush hoods of your motor properly for maximum performance. For the full procedure, you can buy Big Jim's R/C Motor Black Book (http://www.hobbyshopper.com).
Remember, aligning the brush hoods so the comm wears in the center of each brush is the single most important thing you can do to enhance a new stock motor's performance.
Ask Big Jim.
1. Make sure your test brushes are the almost exact size of your race brushes. I used new #766's to test for the #767's I was eventually going to use in the motor. There is only .001" difference is size between the two. With me being a little sloppy in "sighting" down the test brush on the wear mark plus this amount of difference in size, caused one hood on a P2K2 I was doing to be off. The size of the brush determins how much it will shift in the hood. A smaller brush will shift more. A larger one, less.
2. I use a brass brush I bought at a welding supply store to lightly go over the wear mark on the test brush. This blends it in and makes the face solid again so you can see a new wear mark. You can use the same brushes over and over this way. However, eventually, the face will become so distorted from so many wear marks that it will cause the brush to shift differently on the comm than a new brush. As a motor guy who goes through a lot of brushes, this is not a problem, usually. But I found this out when I was trying to be cheap and using the same pair over and over for many motors. I could have just put those brushes in a new motor before they got so distorted and then used an new pair for testing again.
3. Make sure your test brushes have the same radius on the face as your race brushes, or close, Using Reedy #766's for test brushes with a wide radius won't work well if your race brushes are Trinity #4499's with a real tight radius.
I remember someone on the discussion boards saying they used a brush with a flat radius for testing. Well, there's two problems with that. First, the comms reaction to a flat faced brush is different that it would be on a brush with the right radius, causing it shift a more or less amount in the hood. Second, the only brush I know of with a flat face are the large copper shunt brushes that come with a new "non-pro" stock motor. They are so large they don't shift near as much as the better compound brands. This could cause your readings to be way off.
This is important. When the brushes are aligned properly on the comm, there is no blackened area on the trailing edge of the brush. The brush wears cleanly and evenly.
4. Make sure the hood screws are tight each time you check alignment. To facilitate doing aligning quickly, I sometimes leave the hood screws looser than I should. Then when I put the motor on the T30 to run for a few seconds to check alignment, just the weight of the alligator clips and the vibration of motor causes the hoods to shift slightly (and unnoticably) from where I had them. If this happens once or twice in aligning a particular motor, it really screws you up.
5. It's not a good idea to use "used" brushes for testing alignment. Unless that worn radius is pretty much in the center, it will throw off the amount the brush shifts and your readings will be off.
6. You can size the hoods around your alignment bar by squeezing gently with a pair of wide jawed pliers against the sides of the bar. However, I don't advise doing this to Epic motors because the brush dampener is on the top of the hood. It gets bent too in the sizing process. If this type of dampener is not able to move around and center itself with the brush, it could cause a brush to hang. Reedy Yokomo's and some other motors made by Sagami have a lower plate that contains the dampener. Since the dampener is completely separte from the hood, you can resize all you want without effecting it.
7. When re-sizing, don't make the fit too tight. Remember, different metals expand at different rates. When the motor gets hot and this happens, the brushes expand more than the hoods because they're hotter. If things are too tight in there, you could hang a brush.
8. And lastly, The alignment will change as the brush wears because it's not supported as well by the hoods. The more the brush sticks up in the hoods, the better it's supported. The better it's supported the less it shifts. This is the reason there is so much brush shifting on an MVP. There is a large distance between the hoods and the comm.
For years, I have said that I wish the spring post had a slot in the top so the post could be loosened and retightened while the motor is running. Using the arcing to test alignment is pretty much fool-proof. Well, not really because fools are so ingenuis. I sometimes do this to my personal motors but not for production. I don't think the r/c community is really ready to see slots cut with a Dremel in the spring posts on a new motor.
If someone is reading this and you have no idea what we are talking about, these tips are used in the procedure of aligning the brush hoods of your motor properly for maximum performance. For the full procedure, you can buy Big Jim's R/C Motor Black Book (http://www.hobbyshopper.com).
Remember, aligning the brush hoods so the comm wears in the center of each brush is the single most important thing you can do to enhance a new stock motor's performance.