PS4002FK experiences

[swiss]

Yes, of course, but only more of a problem because of the heavy cog.

The JK Hawk 6 had the same problem.

I cut the brushes on this motor, but by the uneven arc of the well used stock brushes, I must not of not tried to align the hoods while I had the brushes out.

I'm going to go to a new motor with short height/width SBF II brushes and see if I can find the fixture I made years ago to align the hoods on these type of motors.

[steve37]

The mags coming loose is a common problem down here in NZ but minor just re crimp the tabs a spot of glue and your good to go, overall they seem to perform as well as a good Falcon 7 but not as the Hawk 7 or Evil 9.
It does however perform more consistent until something else appears out there to compete with it then its the best of the worse, you do get variations in performances from motor to motor but they are still a cheap chang made unit don't expect too much.

[swiss]

Steve,
Do you ever have ones that need a push?

[Zippity]

Swiss,

My Club races these motors in two classes - LMP in CTF chassis and F1 in the JK/Indy chassis. (These classes are also run in our 1/24 Scale Nationals)

I am not aware of anyone having experienced the "push-to-go" phenomenon

[JayGee]

Mike

I have one that has to be push started occasionally. Coincidentally, it's the only PS4002 of any kind that I didn't replace the stock brushes before running. I did check for gunk in the com slots and made sure the brushes were not hanging up before installing the motor in my car.

It ran fine through several minutes of motor testing, then began to act up during practice for its first race. When I got back home I cycled it on-off power about 25 times with a bench-top power supply...worked like a champ. I was beginning to think I had problems with braid since I didn't check for track clearance that day and was riding pretty low in front. After reading that I'm not the only one experiencing this...now I'm not so sure.

- Jeff

[swodem]

...none of mine have been affected but I have seen two-or-three at our track that are afflicted

[Fast Freddie]

The push start problem is easily fixed. While Mike prefers to remove material from both sides of the brushes I prefer the single side approach. Then install the brush with the side that has material removed as the trailing edge of the brush. You keep all the timing and cure the push start problem. The amount of material you have to remove depends on the timing and how well you have aligned the brush hoods, but mainly the timing. Just make sure you remove an equal amount of material from both brushes. I only remove material from the first 1/3 of the brush that way the brush stays square in the hoods. I cured the push start problem in my PS Contender motors and as an added benefit the reduced overlap reduced motor heat. It worked for me try it and see if it works for you. But wait there's more


I noticed the recommended gear ratio for these motors is 3.25-3.50 and the roll out is 4.25-4.50. Am I missing something when the F-Wing guys are running gear ratios at 2.75 with roll outs ratios of 3.55 and less. No wonder they slow down after 2min. I'll bet they get awful warm. I know the chassis only weigh 65gr. or less but when you don't need to lift that kind of heat can soften just about any kind of Super Glue. I understand these are torque motors with big air gaps and strong magnets but they do spin up very nicely, at least mine do.

[swiss]

I'm glad to see it's happening to others.

Not to wish ill will on them, but to quit wasting my time worrying if it's some condition peculiar to my tracks that causes it.

Anyway, I found the fixture I made about 10 years ago to align hoods on assembled motors, along with the stuff to shorten the brush length.

I also did some quick tooling to precisely trim the brush height.

Despite not being anxious to get back into the "screwing around with motors" business, hopefully I can get this problem to go away.

[JayGee]

Since I've not had the push-to-start issue with the $13.00 out-of-the-bag 4002S motors, I'm wondering what the difference is between the 4002S and 4002FK that could be causing the problems. Are the com sizes different? Is the armature timing different?

Mike, I couldn't tell from your comments is if you still had the problem after you removed material from both sides of the brush. Fast Freddie, if you're removing the material from just one side of the brush, can someone help me understand why that isn't changing the timing. In my mind, you'd need to trim both sides symetrically.

Has anyone tried vertical brushes to see if that cures the problem? May not be expressly legal since it requires a brush hood change...but I'd rather lobby a rule change in our local area than have to trim brushes.

- Jeff

[Fast Freddie]

Well after not having anything bad to say about this motor, except it has a seal, I have found a problem I can't correct properly without taking the motor apart. I only have 4 of these motors and the other 3 seem fine but one has the magnets positioned so far toward the can bushing that the arm is riding on the bushing and the brushes have almost topped the comm. I know it's only a $13 motor but in this condition it's useless. The problem arose during break in when I noticed the rpms were not smooth throughout the mid to upper range. This one bites the dust.

[skigolfmike]

Knock the magnets loose, re-position and CA? Or, for $14, get another one.

[swiss]

Jeff,
Yes, I cut the brushes.

The problem didn't occur until they got short.

I thought I grabbed a motor that the hoods were somewhat aligned, but taking them out last night, I found out how bad they were.

As far as vertical hoods, I don't think there is any that would bolt right on.

Even if there is, you would also have to install new $4.00 brushes anyway.

[La Cucaracha]

Never had a push start issue with this motor.

I usually just use the stock brushes, break in on power supply, solder can bushing and go.

Don`t put too much oil on the endbell to keep the comm clean.

Great speed and brakes for such a low cost motor.

My favorite motor right now.

[Fast Freddie]

Jay Gee the timing doesn't change because the leading edge of the brushes haven't changed position. By placing the cut edge of the brush as the trailing edge all your doing is reducing the overlap. the length of time that both brushes are in contact with the same comm. segment. I realized what was happening to my PS Contender motors about 4 years ago. When the arm would stop occasionally one of the arm legs would be exactly between the north and south magnet tips. When this happened both brushes would be making contact with the same comm. segment, a dead short. I didn't have this problem with my BOW arms, it was a difference in the width of the stack legs that caused the problem. At first I did what Mike suggested and removed material from both sides of the brush and it cured the push start problem but it reduced the timing. I then decided to just cut the brush on one side enough to cure the push start problem and by installing them as the trailing edge I kept all the timing. You can reduce the timing using the cut side of the brush as the leading edge but the only way to increase the timing is by rotating the comm., rotating the endbell, or rotating the endbell hardware.

I have tried vertical brushes on my Contenders and it does cure the push start but it also retards the timing. Jay Gee the farther the arm leg travels into the magnet field before the comm. makes contact with the brush the more retarded the timing. That's why removing material from both sides of the brush retards the timing. By using the cut side as the trailing edge and leaving the leading edge stock the comm. makes contact with the brush as if it was a stock brush. The comm. segment just clears the brush a little earlier than stock and no matter where the arm stops the brushes will never be making contact with the same comm. segment and no more push starts.

[JayGee]

Dan got back to me right away with a response when I contacted him regarding this issue. Rather than paraphrase, I'll just quote him directly,

"Jeff, the little I've heaed of this is due to the brushes overlapping on the small com as the brushes wear. The best thing about this motor is you can replace the brushes as needed and the are inexpensive. I've seen a couple with misaligned hardware and a brush worn at an angle shorting another segment. You could try narrowing the brushes a few thousands on each side to fix the problem as they wear.

Dan"

Sounds reasonable to me and Fast Freddie's approach makes sense as well.

- Jeff