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Old 01-16-2003, 01:38 AM   #1
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Default Trinity P2k2Pro ARM- pls help!

Hi all,

I got a question re Trinity P2k2 Pro arm.

The original arm came with my P2k2 Pro motor has balancing holes on it.

I just purchased 2 spare arms pt no.2129 P2k2 Pro arm, and both of them has no balancing holes on them.

I also checked a new in bag non-pro P2k2 arm and has balancing holes drilled!!!

I have 2 Fantom P2K2 and one has holes and one hasn't!!!

now I am confused as I thought all P2K2 pro has balancing holes as they are pro versions and they do not get epoxy balancing?

can anyone help so I can swap ot it they bagged them wrong at factory???

Thanks!
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Old 01-16-2003, 05:25 AM   #2
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It could be that some of the arms didn't need any balancing????

I'm surprised trinity sell pro and non-pro arms - an arm should be an arm - both types should be balanced.

Oh, and stock motor arms won't have epoxy balancing.
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Old 01-16-2003, 10:21 AM   #3
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If the Fanto arm doesn't have any balancing holes then you should be ok, I believe Fantom checks the balance on every arm they sell...... BTW: never buy a pro arm, just relathe it yourself and save the $$$$..... Most Trinity Pro arms need a pass or two on the lathe anyhow......
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Old 01-16-2003, 10:37 AM   #4
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Default Good timing for this subject

Last night I decided to check the balance of my Monster Stock Arm that also had no balance holes. Though this motor has made decent power it always felt like it had too much vibration. I used a modified magnetic prop balancer to check the arm and it was WAY off. I corrected the unbalance and am getting ready to test on my Dyno to see if there was any improvement.
I find it hard to believe that ANY armature would NOT need some kind of balancing, especially a machine wound like all Stock arms are. I will post later after testing if the rebalancing has helped the power output on this motor.
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Old 01-16-2003, 10:59 AM   #5
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you can not find the balance of an arm by just using a prop balancer you need to balance the arm dynamically so you find the balance on all axis'. you need a special device to do this. i would leave it up to the pros
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Old 01-16-2003, 11:14 AM   #6
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Default Checking armature balance

spaz456;

And what axis would you be referring to? An Armature rotates inside the Motor can. This is the only axis you are concerned with, rotational balance.
The Motor builders may use a special machine to check balance and drill the balancing holes, but I guarantee that the end result is the same. A magnetic prop balancer floats the shaft between two strong magnets. The heavy side falls to the bottom, drill to remove weight or epoxy to add weight. Sounds like dynamic balancing to me.

Last edited by popsracer; 01-16-2003 at 11:17 AM.
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Old 01-16-2003, 11:18 AM   #7
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you want to check the lateral balance.
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Old 01-16-2003, 11:29 AM   #8
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Default Lateral balance?

Lateral means side to side, front to back. I can see the benefit to balancing this way, but there is no way for the average person to do this at home.
Besides, I'm talking about a severely out of balance arm that should only improve by correcting the inbalance. And no where did I suggest that anyone else try this themselves. I have the baseline Dyno data for this Motor on my PC and will make another run today on my Dyno to see if the re-balancing made any difference good or bad.
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Old 01-16-2003, 11:48 AM   #9
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yes i was just trying to make the point that you cannot balance this way so you would probaly be better of just buying another arm, because you will need to know where to drill the holes to balance it laterally. but its always worth a try.
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Old 01-16-2003, 12:33 PM   #10
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I work with electronic balancers in my job and I know you cant do as acurate of a job with the prop balancer... BUT... if it has a noticable heavy side on the prop balancer I guarantee it is out of balance and balancing it on the prop balancer will make it much better.
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Old 01-16-2003, 12:35 PM   #11
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Default I love technical discussions !!!

especially ones I know something about...LOL
Pops- ave you ever ran a automotive tire balancer? Because a electric motor armature baancer works much in the same way. As the tire goes thru it's cycle of "throttling up and decellerating" the machine takes very precise measuremnents. once it has completed it's cycle the mahne then tells you where its unbalanced, top to bottom (as your straight on at the tire) and front to rear. It also tells you how much weight to add.

If you donot balance it properly front to rear you might as well not even balance it at all.... It may be fractionally better than it was before, but is still severally unballanced.

Is it possible to get an arm completely ballanced without adding/subtracting weight, even a machine wound one?? YES, but it would be a very rare occurance...... BTW: I had a wheel/tire on my truck once that was completely ballanced w/o adding anything and I had ran it on a balancer myself so I know it was......
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Old 01-16-2003, 12:53 PM   #12
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Thanks for the replys so far...

I just find it weird that all the 4 Pro Arms I looked at all of them have no balancing holes and the 3 non-pro arms have been drilled! but then arms in P2k2 Pro has all been drilled!

I have checked with Fantom and the F404 has not been re-balanced and the F404L has been re-balanced. The 2 Fantoms I have are F404 but one has the holes drilled and the other not.

I can agree that for some freak coincidence that an arm can be balanced but 4 out ot 4??? Not likely plus the fact that 3 out of3 non pro arms has hols!!!

anyone got a non-pro P2k2? hows the arm inside? drilled?
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Old 01-16-2003, 02:09 PM   #13
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IMHO an undrilled stock arm would be suspect for balance. The chances of a machine wound arm being anywhere near balanced are pretty slim.

Popsracer is correct in saying that you can check the balance using a prop balancer. Spaz456 is correct that if it isn't balanced there is nothing you can do about it.

According to Big Jim any full service machine shop can balance it for you. I live a short distance from Big Jim and just let him do it for me. In general, most arms are poorly balanced.

BTW Big Jim has an interesting balance test you can do right out of the box... hold it between your teeth while its running. A REALLY well balanced motor is easy to detect... you can actually hold it with your teeth while its running. You'll let go of the unbalanced ones really quick.
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Old 01-16-2003, 07:29 PM   #14
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Default Honest Reply

Well guys;

Bad news. The rebalanced armature WAS much smoother with less vibration, BUT because of the material removed from the laminations the power was way down on my Dyno.
Oh well, it was an experiment and no big loss. What it did do is make me think that having an armature with NO balancing holes may actually make more power as long as it is in reasonable balance to start. (the next test)
This may be why Hand wound Mod Arms are EPOXY balanced, to keep the magnetic field as strong as possible.

dalem;

Interesting idea, but i wonder what they would charge. I don't trust the big "T" to rebalance my arms if they are that far off in the first place.

sonneteer;

I have two P2k2's, one Pro, one not and both arms had balance holes. I could never get them to run very well in my car so i switched to the the Monster Stock. After Dynoing all these motors, the P2K2's were WAY down on power compared to the MS and the MS has 5,000 more RPM. Just luck of the draw i guess.
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Old 01-16-2003, 10:03 PM   #15
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Just to throw a monkey wrench in the works - y'all do realize that balancing the arm yourself is not ROAR legal. . . Removing or adding any material to any part of the arm besides the commutator is specifically against the rules. . .

Now, that being said, I don't really know why or agree with it since you can purchase balanced arms (mostly balanced) and what does it really do? make the motor more efficient? ya.

Anyway, a couple of questions -

1- if you look at epoxy balanced mod arms, they put epoxy at the "front" and at the "rear" - what does that do and how do they tell which "end" to put it?

2- if I can get RPMs, that's good to me - I usually run Pro10 and we don't need as much torque as a sedan. We weigh only 40oz so we don't have as much weight as y'all do. How much of an improvement did you find, Pops?
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