# T-Jet Mean Green Armature Performance?



## cody6268 (Oct 31, 2013)

I've been considering changing my stock armature of my Auto World Thunderjet Ultra G out for an Aurora AFX Mean Green armature. Would there be any performance increase? 

Is there any way to pop out the armature without a gear puller? Or should I just splurge and get one?


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## brownie374 (Nov 21, 2007)

Probably will be close in performance.


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## Boosted-Z71 (Nov 26, 2007)

I think the mean green will have a bit more torque, especially if it is one that ohms out in the 5.8 range, they are monsters for a "stock" arm. If you static balance & flatten the com plate on the JL arm you will see a significant improvement. Also many JL cars need the springs adjusted for optimal performance. Have you tried an aftermarket set of brushes, JB, Wizzard etc, they will give a JL a kick in the pants as well. You really need a gear puller and press to do the swap right, I have seen it done with a screwdriver and hammer. 

Boosted


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## old blue (May 4, 2007)

...."and torque is important for pulling those HO scale stumps" !!!!!!



To quote a thread from long ago.
Old Blue


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## leonus (Dec 17, 2013)

The right tools are important if you want to do any job right...


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## Rich Dumas (Sep 3, 2008)

The performance of mean green armatures can vary a lot, a really good one will be faster than a regular 14-15 ohm Johnny Lightning/Auto World arm. Go for a pinion gear puller if you expect to work on these cars very much


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## Serge (Jan 4, 2014)

*A parallel*

First of all, having the the right tools is never a bad thing unless you neglected to pay the mortgage with the money.

I race with FRHO and we have a race class called GT. It is essentially a Fray style car with any chassis, gear or armature combination. That means you can run a JL/Playing Mantis/AW chassis with a three lam 14 tooth set up; or an Aurora two lam 9/12 tooth combo and anything in between. Currently the mean green 12 tooth on a classic Aurora chassis appears to be the best. I personally run the latter with a rivet chassis. 

This might help with your Ultra G adventure. Good luck
S


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## Boosted-Z71 (Nov 26, 2007)

old blue said:


> ...."and torque is important for pulling those HO scale stumps" !!!!!!


And getting off corners faster than the other guy

Boosted


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## cody6268 (Oct 31, 2013)

Rich Dumas said:


> The performance of mean green armatures can vary a lot, a really good one will be faster than a regular 14-15 ohm Johnny Lightning/Auto World arm. Go for a pinion gear puller if you expect to work on these cars very much


What would be a good one that didn't cost a whole lot?


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## Boosted-Z71 (Nov 26, 2007)

Spend the money on a good puller /press, RTHO makes killer tools, there a little more than some others but the quality is great, and you will wind up with many less gears & arm shafts damaged

Boosted


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## Serge (Jan 4, 2014)

*addendum*

the mean green, that I referred to, was blueprinted and balanced by "Bear" Obermeyer, before he died. It started out with a perfect com plate and a 0 delta between poles. Great mean greens are more common than you might think.
S


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## Boosted-Z71 (Nov 26, 2007)

Mean Greens that ohm at 6.1 to 6.2+ on all poles are very common, most are electrically balanced between poles, I have a few 5.7 ohm MG's, they are harder to come by and with the right magnets in the car you can tell the difference from the 6.0+ MG's. The drag Buick I built for Sgrig's contest on here was a 5.8 ohm MG, in identical test chassis it was 2+ car lengths ahead of the 6.0 MG in less than 4 running feet & held that lead through my 16 ft straight. 

Your exactly correct, an arm that has been balanced, shaft set perpendicular, polished and the com plate flattened to less than .0005, will make a huge difference on performance. 

I have heard others speak good about Bears armatures, If I am not mistaken he sold items on ebay & I think I have some of his "Fray" arms, they run well too. 

Boosted


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## rholmesr (Oct 8, 2010)

I think in most cases swapping a 'stock' mean grean for a 'stock' AW or JL arm will result in a performance improvement. Quite possibly a huge improvement. 

There may be circumstances that would not show an improvement when making the change - 1) if the AW arm you have is really an exceptional one (i.e. naturally balanced and the comm is not shaped like a potato chip) or 2) the mean green arm you pick to use is way out of balance or has uncommonly poor comm geometry or 3) there is something else about the car that is preventing it from running fast such as bad pickup shoe setup or out of round wheels, etc.

And like others have discussed, if you have the mg arm balanced and trued it will really kick butt.

The right tool for the job makes the job _a lot_ easier. I have no affiliation with RTHO but he makes great t-jet tools. The RTHO RT-550 gear removal tool is the bees knees but costs $60. I do a lot of t-jet work so mine gets used all the time and is worth it's weight in gold. re-iinstall gears with RTHO RT-600 gear press.

If you don't have that kind of cash but want to get something going a simpler puller like the RTHO RT-300 works okay (lots of guys make similar pullers and maybe a little cheaper still) - but it tends to booger-up the gear a little bit that may require a little touchup work to un-ding the teeth. Only try and pry off a gear with a screwdriver or equal as a last resort as it will bend the gear and might bend the arm shaft too which would render it useless. If you don't have a gear press you will have to use a less expensive method like tapping gear back on with a tack hammer or a small vise - either of which is a good way to get a cocked gear or dinged arm shaft if you goof it up - Go slow and good luck!


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## leonus (Dec 17, 2013)

Not trying to hijack the thread, but how does one go about " flattening a com plate"??


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## Boosted-Z71 (Nov 26, 2007)

Flattening the com plate assures that the plate is running flat against the brushes and no wobble or run-out on the plate. Scale Engineering – TGT-1, makes T-Jet Comm Plate Run-out Indicator tool that you put the armature in and then by a dial indicator you check the flatness of the com plate. 

As for adjusting you have to carefully adjust the plate by prying it according to the reading on the gauge to get it to .001 flatness, checked around 6 or so spots on the face of the com plate.

I use .0005 as my goal for the flatness. After you get it moved on the mounting tabs and flat as well as truly perpendicular to the arm shaft, you apply a light dab of epoxy or nail polish on the under side of the com plate at the mounting tab, keep it small as this also works on the balance aspect of the arm as well. 

Some guys also glue the com plate to the windings, several ways of securing the plate once you get it flat. I like gluing on the tabs as it is still possible to tweak them once the epoxy starts to setup. 

Boosted


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## Rich Dumas (Sep 3, 2008)

If the commutator plate is tilted you can straighten it using the method that has been posted, however some comm plates are warped. If the plate is only slightly warped you can fix that using a special sanding tool. If the warp is bad enough using the tool would go right through the comm before you got it flat. Save armatures like that for shelf queens.


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