64 replies to this topic

[MSwiss]

The Pro Slot 4002FK has been a great bang for your buck motor.

But has anyone else seen them, occasionally needing to be push started?

I think the situation is unique to our hardbody class, running on the (very) low amp power supplies on my flat track, but I'm still curious if anyone else has had the same problem.

[The Number of]

Noticed it two times with different cars and drivers with the wing cars we race on sundays at MMW.

[Gator Bob]

I suspect it could be magnet lock, a poor solder joint at the comm, or an 'open' pole would do it but it wouldn't 'run right' even after the push.

[Michael Rigsby]

Mike,
 
I did have one of these I was playing around with just to see what it would do and after about three fifty-lap runs it did exactly this. I had it in a Cheetah 11 chassis geared 11/36. Cleaning the comm with an old fashioned comm stick and replacing brushes after a good clean-out made no difference. Tore the motor down and though I saw nothing visible, but one of the pole ohm readings was open. I suspect there was a broken wire somewhere in the stack windings somewhere that wasn't visible, just like we used to get on Falcon 7 motors after the motor gets really hot. 

Since it was just an experiment I tossed it in the garbage. We really don't run them down here in anything since the Retro Hawk is so reliable

[Half Fast]

As Mike R said a "dead pole" is what usually causes the need for a push start. It happened to me with Group 12 motor.

 

Cheers

[MSwiss]

I suspect it could be magnet lock, a poor solder joint at the comm, or an 'open' pole would do it but it wouldn't 'run right' even after the push.

  
The motors run fine once push started.

Noticed it two times with different cars and drivers with the wing cars we race on sundays at MMW.

Bill, glad I'm not losing my mind.

How did the motors run once push started?

Coincidentally, I use to see a fair amount of the "original make-believe FK motor", the JK Hawk 6 eventually needing to be push started.

What seems to be unique to the 4002FK is that they appear to sort of want to run (the arm rocks).

In the process, they draw a zillion amps and in the case of on my flat track, all the running cars severely slow down.

[Gator Bob]

Once you get magnet lock once and hold the trigger for more than a second the wire insulation can fail. If it's enough to slow the field... Whoa, LOL.
 
Most likely where it makes the sharpest wrap on the first level... could have zapped a joint, give it one shot at re-soldering the comm tabs if there is an open pole... nothing to lose... I've saved a couple over the years in non-sealed racing.
 
Also, too much timing and overlap can cause 'rock'.

[MSwiss]

What the common denominator is between the 4002FK and the Hawk 6 is the heavy cog.

Not sure why that would promote the problem, but I don't recall ever seeing a low cog, real FK motor, exhibited this problem / needing a push start.

[Gator Bob]

It might be cumulative with the big cog, small comm, big brush, and whatever static timing is built in.

 

Those cut brushes (center cut) like you did for the Hawk 6 might solve the issue.

[Matt Sheldon]

You had me at "push start" and lost me at "cog".

[NSwanberg]

I have noticed this happening with my own PS 4002 FK powered car and a few others at Downriver Speedway. It seems to be a short term phase the motors go through as the brushes wear. Who knows what it could? My car did it for two races and then stopped doing it. It always started and ran well after a push. That motor has like fifteen 24 minute races and a two-hour enduro on it and is still capable of a podium finish at Downriver. Certainly an amazing little motor package for the bux.[/size]

[The Number of]

The ones I have seen run fine after the push.

[Big Booty]

I'm assuming the motor uses a SBFII brushes?

The brush is 3.15 mm tall. What is the diameter of the comm on these motors? Less than 5mm?? Less than 4.6mm??

I suspect that there is a lot of overlap (degrees of rotation) where one of the poles is a dead short (combination of big brush and small comm diameter). If the motor stops while in this dead short position then the vast majority of the current flowing though the motor is basically a dead short.

For tracks with "unlimited amps" the track can supply enough amps so that some flows through the other pole and that is enough to kick start the motor.

For low amp tracks as Mike has suggested there isnt enough spare amps for this to happen and the motor sits there until you push start it or the pole burns out.

[Cheater]

Rick,

The Pro Slot motor comes with Pro Slot's own Goldust brushes, I'm sure.

[Big Booty]

I've got a new set of Goldust brushes in the shed. I'll measure how tall they are but I suspect the dimensions are very similar to SBFII.  

So what is the diameter of the comm on these motors?

[Cheater]

Yes, the brush dimensions should be very close, if not exactly the same.

Am unable to answer the comm diameter question.

[Pablo]

I'm assuming the motor uses a SBFII brushes?

I don't think Pro Slot would install Koford brushes in their motors.

Rick, I'm not at home to measure, but the comms are not small, like unserviceable brush FK motors - they are in the vicinity of .200" OD
 
The intel I gathered (from unofficial sources) tells me the stock brushes are not Goldusts, but in testing the installation of Goldusts doesn't increase performance. They do, however, last longer than the stock brushes. The BFIIs probably would live longer as well.

[Bill from NH]

Pro Slot sells production brushes for about $1.50 a pair, whose spring ends have the same cross hatch marks as their Goldusts. This is the brush they use in their SpeedFX sealed 16Ds, I'm guessing they use the same brush, but shorter, in the 4002FK.

These brushes are a different color than Gold Dusts, but I forget if it's darker or lighter. Pull one out and compare it to a known Goldust. These production brushes, in a 16D, would only last a race or two, so they were quickly removed and replaced.

[John C Martin]

I took the Super Big Foots and filed them down to the bottom of the spring slot then recut the slot with an X-Acto saw blade.
Used the stock length BFB to attempt break in and got excessive heat; they're too long! Too much spring tension. So the shortening cured this..

Great little motors, much more drivable than the 4002 used in the Retro Stock Car... great with a 8/27 and.812" tire.

Comparable to a Retro Hawk, maybe a little better brake and torque, because better springs, more brush contact. Gear ratio 8/27 versus 9/27 for Retro Hawks).

Tested four in the same chassis at 8/26, took the slowest two changed to 8/27 and they all are in the 4.51 to 4.56 range. The two slowest were now the fastest. But I'm not racing them on this track or power so I'll have a choice on different track and power (Peachtree City). Da Race.

Like to see them IRRA® legal.

[Noose]

They are John for Can-Am Plus.

[John C Martin]

They are John for Can-Am Plus.

Awesome ..good choice..twiking springs and brush choice would add some fun..good move IRRA..

[MSwiss]

.twiking springs and brush choice would add some fun

I'm pretty sure you're in the minority.

Isn't twiking what Miley Cyrus does on stage?

[Pablo]

JC does it back at the hotel after a big race 

[John Streisguth]

That's twerking....

 

if you want some entertainment, google "twerking to Beethoven"  LOL

[John C Martin]

Yeah my knee twiks every step I take. Imagine the TIN MAN twerking ..that'd be me ..lol.