# Ohm an Assembled 440-X2 Chassis



## Grandcheapskate (Jan 5, 2006)

Hi Guys,
Is it possible to get the Ohm reading on a 440-X2 armature in a fully assembled chassis? You can see a bit of the comm at the front of the armature in a little window from both the top and bottom of the chassis. I put one of the leads through the top window and one through the bottom window. I'm guessing this connects me to two different poles.
Because Mattel is now producing battery powered sets, the new Mattel 440-X2 battery powered chassis look exactly like the 440-X2s designed for electric racing. The only way to tell them apart is by getting the Ohm reading of the armature.
Am I correct in assuming that Tyco and Mattel chassis designed for electric power packs should Ohm at about 7 and the new batery powered chassis should Ohm at around 4?
We had a little discussion about the differences in the chassis at the Parsippany show. It seems the battery powered chassis will be faster if there are sufficient amps to drive it. Without enough amps, the chassis could overheat.
At this weekend's show, someone was asking me if the battery chassis would be legal to race in the 440-X2 class. I have no idea. For those who race these chassis, do you allow the battery powered chassis or is that now a new class?

Thanks...Joe


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## GoodwrenchIntim (Feb 22, 2005)

I think all mattel arms are now around the 4 ohm, an in most places that race "stock" cars, the arm is NOT legal ohms to low


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## SwamperGene (Dec 1, 2003)

Anyone got a good pic of a 4-ohm? I heard there was a difference in the comm retainer.


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## SwamperGene (Dec 1, 2003)

Grandcheapskate said:


> For those who race these chassis, do you allow the battery powered chassis or is that now a new class?
> 
> Thanks...Joe


Personally, I wouldn't allow the arms or the odd traction mag, which is easy to spot with the help of a normal x2 traction mag. :thumbsup:


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## Grandcheapskate (Jan 5, 2006)

The Battery powered chassis are designed to run at 6 volts - 4 D batteries at 1.5v a piece. I assume the Tyco 440-X2 was designed to run around 16 volts, which is the rating of a wall wart. Therefore, I would assume there is a difference in the armature between the two chassis. I'd like to be able to tell them apart. I'm guessing the two chassis would have different Ohm readings. Yes? No? Otherwise, how do you tell them apart?

Thanks...Joe


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## SwamperGene (Dec 1, 2003)

Grandcheapskate said:


> The Battery powered chassis are designed to run at 6 volts - 4 D batteries at 1.5v a piece. I assume the Tyco 440-X2 was designed to run around 16 volts, which is the rating of a wall wart. Therefore, I would assume there is a difference in the armature between the two chassis. I'd like to be able to tell them apart. I'm guessing the two chassis would have different Ohm readings. Yes? No? Otherwise, how do you tell them apart?
> 
> Thanks...Joe


Actually Joe, we overpower them already. Their 170-wind 19awg can motor (That is a typical "Tyco" arm to us) is rated at---------



















4.5 -9 volts. :freak:


Also, there is a fairly decent chance they are not Mabuchi arms...in which case there would likely be a physical difference.


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## GoodwrenchIntim (Feb 22, 2005)

the com retainer is pink an white normal tyco is all white


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## blubyu (May 4, 2008)

The new Arm's have a Red plastic com,& the retainer ring is still white. Also there is one small hole on each com plate in the center right by the retaining ring,about .030 dia. The hard one to tech is the new G3 arm which I hear is the same color as all the other "stock Red wire arm's" but ohms out a 3ohms. Hope this helps any Tech inspectors out there.


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## GoodwrenchIntim (Feb 22, 2005)

timing also looks to be slightly retarded by a couple degrees, Left is normal tyco arm, right in the mags in the 4 ohm


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## blubyu (May 4, 2008)

GOOD PIC GoodwrenchIntim. They are more of an orange/red plastic.


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## SwamperGene (Dec 1, 2003)

There ya go Joe, tech issue solved.

Good pic Kevin. :thumbsup:


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## LDThomas (Nov 30, 1999)

*Can it be...*

Hey SG, did you really mean to say 19 awg? 39awg sounds a bit closer to me...


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## SwamperGene (Dec 1, 2003)

LDThomas said:


> Hey SG, did you really mean to say 19 awg? 39awg sounds a bit closer to me...


 
Yeah, my bad. I glanced at .9 instead of .009 in the chart :freak:


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## AfxToo (Aug 29, 2003)

> Is it possible to get the Ohm reading on a 440-X2 armature in a fully assembled chassis?


To a course degree of accuracy, yes, at least well enough to know whether you are looking at a 6 ohm arm versus a 4 ohm arm. Here's what I did to prove the method:

1) Get a fresh 1.5V nominal AA battery. (Nothing larger!)
2) Get an ammeter and some jumpers. 
3) Set the ammeter up for 1 amp or greater current measurement, just to be safe. You should not expect to see more than 500 mA. My meter has a 10A setting.
4) Apply the AA battery power to the car at the pickups with the ammeter in series with one of the leads going to the car.
5) Hold the rear wheels of the car with your fingers and slowly turn them by hand while looking at the ammeter. Write down the largest current reading you see. (This is "I" for the formula below.)

Apply Ohm's Law to calculate the bulk resistance in the circuit with the arm locked. 

R = V/I,

where V is the battery voltage and I is the peak current you measured. This resistance includes the resistance of the brushes and all electrical connections and electrical contact surfaces. This will be good enough to tell a 6 ohm arm from a 4 ohm arm. 

I used this to measure the bulk resistance of a Tyco 440-X2 and a Life-Like T. The Tyco came out to 7.1 ohms and the Life-Like came out to 5.3 ohms. The arm resistance is probably about one ohm less than these bulk readings, with the brushes and brush-comm interface being the primary contributors to the difference. To measure the arm by itself you should remove it from the chassis unless you can decouple it from the brushes and get at the comm while it is still in the chassis.

Do not try this with higher voltage or current sources.


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## Grandcheapskate (Jan 5, 2006)

So, are we then saying that the Mattel chassis made prior to the battery era has the same color comm as Tyco chassis and therefore the same characteristics?

And all armatures with an orange/red comm constitute a battery powered chassis? And are therefore a class unto themselves? This would include the HPX2 chassis in the Charger/Superbird set.

Having just checked a couple chassis, I can't tell what color the comm is while the chassis is fully assembled. All I can see is the white retainer ring.

Does my method of putting the Ohmmeter probes through the upper and lower openings to the comm not show me a somewhat accurate reading?

Being almost completely electrically incompetant, what is meant by "retarded timing" and what effect does it have? 

Thanks...Joe


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## AfxToo (Aug 29, 2003)

> Being almost completely electrically incompetant, what is meant by "retarded timing" and what effect does it have?


Without getting too technical ... (I hope)

The comm timing determines where in the rotation of the arm the poles get energized and de-energized. Each of these energize/de-energize _cycles_ involve the reversal of current flow in the pole windings simply due to the fact that the comm and brushes form a switch. At the same time, the pole windings are coming under the influence of the motor magnets. Motor theory, backed by Lenz's Law, tells us that the simple act of moving a wire or coils of wires through a magnetic field causes current to flow, or be induced, in these same wires. So there are two things influencing the flow of current in the pole windings, the comm (switch) and the motor magnets (induction). 

Motor timing in a brushed motor involves moving the comm/brush so its switching effect takes place at a different point in the angular position of the arm relative to where the motor windings are coming under the influence of the motor magnets. Depending on where the comm switching takes place, the current induced in the pole windings by the magnets can either reduce or increase the time it takes to complete the energize/de-energize cycle. The geeky name for the cycle timing variable is armature reactance. The cycle time ultimately limits the maximum motor speed, so improving the cycle time allows the motor to reach higher rpms. This is the advanced timing case. In the retarded case, the cycle time is longer, there is more opposition to the current switching, which results in greater current flow in the motor windings. Current flow is directly proportional to torque, so the greater current flow results in more torque, but the maximum rpm that the motor can achieve is now reduced due to the longer cycle times.

So in a nutshell, motor timing is all about controlling the relationship between switching and induction.


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## GoodwrenchIntim (Feb 22, 2005)

Grandcheapskate said:


> So, are we then saying that the Mattel chassis made prior to the battery era has the same color comm as Tyco chassis and therefore the same characteristics?
> 
> And all armatures with an orange/red comm constitute a battery powered chassis? And are therefore a class unto themselves? This would include the HPX2 chassis in the Charger/Superbird set.
> 
> ...


Yes, pre mattel should be all white

Yes the battery arms have the red/orange retainer ring

If you take a flashlight an shine it through the bulkhead on the bottom of the chassis you should be able to see what color they are. They new mattel com retainer also looks to be bigger around then the tyco's

See what Afx said

Also see what Afx said, Basically retarded timing gives you more torque


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## Grandcheapskate (Jan 5, 2006)

Thanks guys....


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## blubyu (May 4, 2008)

Not ALL Red/orange coms are under the National S/S rules.....the New Mega G's motor has one and it ohms @ 6.0. but with a shorter shaft.


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