# Problem with Aurora NOS tjet Chassis



## 82whiskey (Sep 6, 2009)

Hi all,
I bought these nos chassis with the knowledge they had an issue of some sort. It was thought to be a gearing problem as the motors strained under power. There does seem to be an issue with the gearing as the wheels do not turn very freely but I noticed on two (don't want to try any more) that when I removed the crown gear and ran the motor it still did not run as fast as expected and got hot quickly. When I pulled the motor out it looked like below.










Wondering if anyone has seen this before with new chassis. Any idea what could be causing new motors to run so hot so quickly?

Thanks, Brian


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## Marty (Oct 20, 1999)

Any binding will cause that situation. It might be as simple as cleaning and getting the 40+ year old lubricant off and re-lubed. When I first read your post I thought you might have a Model Motoring chassis. ALL of them I had did that.

Marty
Marysville, OH


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## alpink (Aug 22, 2010)

looks like you might have the red tip green wire arm there with original stock magnets. upgrade the magnets along with removing any restrictions. check brush spring tension. check ends of arms to ensure no contact with magnets or sides of chassis.


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## Boosted-Z71 (Nov 26, 2007)

You need to work your way through the top plate, chassis and gears to find the tight spots and free them up,1st make sure the arm spins free in the top plate, without the idler installed, then add the idler and test again, Sometimes the pinion gear or cluster shaft gears are pressed down too far and tightens things up. Then remove the idler & insert the top plate into the chassis, No brushes or magnets installed & check the arm again, this checks the arm hole in the chassis to see if its binding, if its free, start adding components and checking until you find the component causing the issue. 

Al is right on the stock magnets, they wont support a hotter arm very well at all, but it should run a little bit prior to getting too warm. Clean up the com plate with an eraser, and polish the brushes on some paper.

T-jets are truly a Miracle piece of machinery that possibly no one fully understands, but there are a few that get closer to the answer everyday.

Boosted


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## smalltime (Jun 3, 2006)

Also, double check the magnets to be sure they are opposing. I.E. north/south. They may have gotten switched between chassis at some point.


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## slotcarman12078 (Oct 3, 2008)

Lots of stuff to check, as mentioned above, but I'll add a couple more.. Ohm the arm and see if they are fairly even numbers. Once in a blue moon, I've run across chassis bases and top plates that didn't line up the top arm and pinion shaft holes exactly right. For a quick check, try switching top plate assemblies with bases and see if that helps. 

I do agree with Boosted, that T jets are truly a miracle of ancient technology, the likes of which sadly have been lost to the ages.. It just goes to show, the super computers ( between Aurora's engineering staff's ears ) were far superior to the modern technology we have today.


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## Bill Hall (Jan 6, 2007)

Providing the windings arent discolored by obvious overheating, as we dont have the top shot; I'd go with Joe and ohm it out first. If it passes, clean the grungous off the comm plates. As those appear to be box stock t-jet magnets, you'll need to go with the magnet upgrade and run it sans idler. Easy does it! Make sure ya remember to lube it too.

As a general rule I like to ease the comm spring pressure off on low ohm armatures and work my way carefully back. Theres no advantage to gunning the brushes down for more rpm if your gonna let all the smoke out of the wires. 

A decent green/red arm will pipe right up whether it's balanced or not and have some snarl. A well balanced green/red should be a real howler. You'll feel the difference in your hand when ya wind up the unloaded chassis. No need to pee wind it or flog it... just warm her up prudently and give it a few quick blips. If it passes, let her plug along at half throttle, check the temp; then ohm it again. If you touch the the arm pinion and smell bacon frying...it's a dud....lol! 

Based on the photo though, I dont have a good feeling. It's already set up as a nine tooth so ya cant get any easier on the gear loading. The undercut at the 12 oclock position looks shrunk and overheated which is never a good sign. If it fails the basic tests and you've exhausted all the good advice thats been offered above, it's best to reject it immediatly rather than frying the comm pit of a perfectly good chassis when the inevitable failure arrives. They dont heal themselves. I generally toss them in my core box and save them up for a guy like sgrigs who always needs usable cores for rewinding.

Good luck!


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## joegri (Feb 13, 2008)

can i jump in here!! this is what the HT is all about man!! 82 you will find yer answer in 1 tuning sesion and i,m going with what all the boys said but i,m leaning toward the boosted method!! there is a handful of what it couldbe. but the answer lies in the first 7 posts!!! i also just learned something tonite just from reading this post!! never thought that tuffy mags were,nt that good.for me i run the dash mags in my tuffys with jb,s thunder brushes. that seems to cool,em off a bit. good luck man yer on yer way to a good fast/ cool runnig chassis!! and you guys that reply .. i always learn somethin from ya thanx man


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## cwbam (Feb 8, 2010)

(I have a very dry sense of humor)
Did they ever run good?
New Chassis ? its 40 years old. 
I Spinned !!! that's a great Start!

thanx for the Idea JB's thunderbrushes! any others ? what new shoes for just cruising
and not fray racing? any wide easy running shoes (without that tweaking and sanding)


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## old blue (May 4, 2007)

Question to all: What is the significance of the red lettering in the Hong Kong sticker on the side? I know it was mentioned in a previous post.

Thanks,
Old Blue


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## wheelszk (Jul 8, 2006)

old blue said:


> Question to all: What is the significance of the red lettering in the Hong Kong sticker on the side? I know it was mentioned in a previous post.
> 
> Thanks,
> Old Blue


That should be a wild ones chassis. They had the red sticker.


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## alpink (Aug 22, 2010)

I heard wheelszk is a 'wild one' ! "Wild Bill" !


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## wheelszk (Jul 8, 2006)

Thanks Al


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## 82whiskey (Sep 6, 2009)

Hey all,

Thanks for all the great advise! Been so busy I haven't had a chance to get back to them but I do have one other question. I'm using a variable voltage power supply to test them and I'm wondering what voltage I should be at?

I know the old tjets run fast at 20 - 22 but I understand the motors will run hotter. I was testing at about 16 volts.

Thanks, Brian


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## Boosted-Z71 (Nov 26, 2007)

I run all my t-jets at 18-19 volts, No particular reason other than they seem to run good at that voltage, Usually a heat issue is caused by friction, too much brush tension or weak magnets with a hot arm setup.

Boosted


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## nasty23 (Sep 15, 2010)

*newb question here*

not to sound dumb or anything but when u guys say *(nos)* what does that mean?:freak:


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## alpink (Aug 22, 2010)

New
Old
Stock
an item that is very old but never used and probably still in it's original packaging.

or 
Nitros0xide
depending on the rest of the sentence.


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## nasty23 (Sep 15, 2010)

thank u alpink, i feel soo stupid sometimes:thumbsup:


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## alpink (Aug 22, 2010)

nasty, not at all. I too had to ask what it meant once. the only stupid question is the one not asked. keep a good attitude and answer when you can and we shall all get along just fine. al


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## nasty23 (Sep 15, 2010)

alpink said:


> nasty, not at all. I too had to ask what it meant once. the only stupid question is the one not asked. keep a good attitude and answer when you can and we shall all get along just fine. al


thanks alot


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## slotking (May 27, 2008)

one of the basic questions asked was to ohm the arm. Did you do that?
what did it ohm?

binding: take the mags out and put the gear plate back on and feel if spins free

magnets : is there pull? it looks like stock mags and they run from 100 to 700 gauss, if you have weak ones, it will heat up and be slow.

the arm looks to either 6+/-ohms or 14+/-ohms which will strain with weak mags.


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## joegri (Feb 13, 2008)

slot king says it all.. if its not binding and the ohms are ok its the mags i know its a lot to diegest but it can only be 1 let us all know what it is the HO world is watchin no pressure man


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## 82whiskey (Sep 6, 2009)

I planned on do it the other night and I couldn't find my freaking meter!:freak:

I definitely plan on finding it this weekend and using all the great advise I've received to try to figure out what is going on with these puppies.

Thanks all, Brian



slotking said:


> one of the basic questions asked was to ohm the arm. Did you do that?
> what did it ohm?
> 
> binding: take the mags out and put the gear plate back on and feel if spins free
> ...


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## 82whiskey (Sep 6, 2009)

Hey all,

Just wondering what magnets you all would suggest? Not really trying to hop these up, just make then run well.

Thanks again, Brian


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## Boosted-Z71 (Nov 26, 2007)

JL stock mags work great with Aurora arms, also Dash magnets, or if you want a screamer a set of Nacho polymers are the hot ticket

Boosted


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## nosubfor#3sr (Nov 14, 2009)

If you have a green wire red tip arm that should be a tuff ones arm. If it is a tuff ones then it should ohm between 5.5 -6.00 ohms. A tuff ones arm with weak stock magnets will run slow. Try swapping stronger magnets first. If there is a noticeible difference then you are on the road to success. If it runs better but still hot then go after the friction aspect. Warped chassis, warped gear plate.,gears pressed on to tight, bent arm shaft,bent pinion gear shaft, gear plate clamp to tight, center idler gear to large and so on all cause friction.


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## slotking (May 27, 2008)

stronger aurora mags are red/white blue/yellow(super II), 
the JL/AW mags may fit right or stretch the chassis so they are sometime sanded down a hair.


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