# squirely tjet lots of break?



## joegri (Feb 13, 2008)

hey tuners im sure somebody has seen this and maybe a fix.this chassis has blue/yellow mags and arm out of a magnatrack(red/copper wire. and its a tjet chassis. the symptoms are really quick acceleration when you touch the trigger and when you let off she stops on a dime! i know these are traits you want in a real car but,this 1 is almost undriveable. i have tried backing off on the brush pressure that didnt help.im liken more coast in my jets seems to get the best track times.can it bee the mags are way strong?also itgets hot easy.think ill try some wornout brushes just for laughs ive read the fray tunning i thought taking some pressure off the brushes would do the trick.i guess it falls under hot running motor. any hints ill try. if i cant cool it off im gonna break er down and start again with another chassis. thanx for reading and responding to my longwind!:freak:


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## martybauer31 (Jan 27, 2004)

Yep, my first guess would still be a LOT of brush pressure.... Try reducing the height of your brushes by sanding them down a bit with some really fine sand paper.

Also maybe try swapping out your super II mags for some weaker ones as well.


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## SuperFist (Aug 7, 2005)

Look to see if there is a spacer on the top of the armature between the arm and the deck.
Make sure there is some axial play in the arm when it's in the chassis,
without the brushes installed.

While you're at it check the cluster gear shaft is not tight,
or binding up with the deck installed without the idler gear.
And the idler gear is not tight on the post.

__________________


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## Bill Hall (Jan 6, 2007)

*Greed, Compromises, and Detonation*

Well, by their own nature stronger mags will add some brake right off the bat. The real problems start when you start cranking the comm pressure up. 

Sometimes you'll just have to decrease the pressure if your insistent on running the particular magnet set in question. The issue at hand always seems to be that your intial bench setting is a little snug AND after track test and tune you generally need to take a bit out. NORMAL! Fist makes the valid point that all other frictions should be invetigated and relieved. They should be at a bare minimum as increasing the comm pressure is the ultimate in friction loading.

Care should be taken your armature is not contacting those super twos. Verify your airgap because the super twos can be kinda clicky and mask the symptom. Not all super twos are the same. I have seen many setups that rub for one reason or another. This or that is too loose or too tight.

MATCHING the response of an armature to the chosen magnet set is like shoe tuning...it appears to be a black art until you get the hang of it and finally admit to yourself that not all combinations are guaranteed to work together. For every few cars you tune up you'll detune some as well.

Like the 1:1 world, a good straight line car and a road car are two different onions


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## smalltime (Jun 3, 2006)

All god responses to the problem......but I don't know of ANY T-Jet chassis that can produce enough tension to stop an AFX arm. (if you have one, I willl pay a bunch for it)

More than likely, you have a bind somewhere. The usual suspects will show up here. gears, arm shafts, idler gear bosses all should be checked. But there is a place overlooked by the best and NEEDS to be inspected.And it matches your symptems prefectly, the cluster gear shaft.

If it is a LITTLE too long and pressed in to the hilt, it can protrude out the bottom of the crown gear box. This would not be a problem if there weren't a splined axle rotating directly under it. when you accelerate, the gear is loaded and thus rises up. As soon as you decelerate, it is slack, and contacts the SPLINED axle, thus "stopping on a dime".

An easy check is in the offing. 
turn the chassis upside-down, and while rotating the rear axle, aply a sharpy to the center portion of the splined axle. Being shure to get a complete rotation. Run the car on the track and see if there is a witness on the spline. if not, I'm a zero, if so, well...................


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## joegri (Feb 13, 2008)

ok u aint gonna believe this but,(maybe u will) i was running this chassis with a test post and seems like there was some bind on the fronts and changed out the mags to a red /white combo way better but still kinda warm . think ill stare at it then move to something else. and i want to say " thanx to all the guys " for the input. i love adjustin the lil cars to makem run better. but the best is from guys out there!!


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## NTxSlotCars (May 27, 2008)

Plenty of great advice.
I learned of something that used to make me hate tjets. If all else above fails, try this.
I don't know how fast the brake is on your car, but if you are going full blast, and let off the trigger, 
and slide the rear tires instead of coast, it could be that your magnets are mismatched. 
Meaning, one magnet is stronger than the other, an pulls the arm to one side, binding it, especially when braking. 
When you have power on, centrifugal force keeps the arm fairly centered, but when you let off, 
the electromagnetic field powered by the track stops, and one magnet or the other may pull the 
arm to one side, and bind it just enough to cause a problem.

































Hope this helps. :thumbsup:


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## martybauer31 (Jan 27, 2004)

The first 2 didn't really help me...

But those last 2 have me dialed in, thanks for clearing it up for all of us NTX!!!!!


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## joegri (Feb 13, 2008)

Wow!! you mean alls i had to do was the last schematic breakdown, then trace back to the load area hence the final stepdown transformer would relieve the build up off + neutrons. i toatly missed that. so what i did was swap mag to a lesser strength changed to a thinner guide pin and a test post that didnt bind the fronts. im such a dummy. as i was reading ntx post it had me for a second then i just started laughing my but off!!ntx that was great!!


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## SuperFist (Aug 7, 2005)

joegri said:


> ok u aint gonna believe this but,(maybe u will) i was running this chassis with a test post
> and seems like there was some bind on the fronts...











__________________


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## A/FX Nut (May 28, 2004)

joegri said:


> hey tuners im sure somebody has seen this and maybe a fix.this chassis has blue/yellow mags and arm out of a magnatrack(red/copper wire. and its a tjet chassis. the symptoms are really quick acceleration when you touch the trigger and when you let off she stops on a dime! i know these are traits you want in a real car but,this 1 is almost undriveable. i have tried backing off on the brush pressure that didnt help.im liken more coast in my jets seems to get the best track times.can it bee the mags are way strong?also itgets hot easy.think ill try some wornout brushes just for laughs ive read the fray tunning i thought taking some pressure off the brushes would do the trick.i guess it falls under hot running motor. any hints ill try. if i cant cool it off im gonna break er down and start again with another chassis. thanx for reading and responding to my longwind!:freak:



One more thing you can do is, Ohm the armature. Make sure all three windings are equal or close to it. I've had one read at 14.5, 14.6, and 34.2. That was one of my armature temperature problems I've had in the past.

Randy.


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## martybauer31 (Jan 27, 2004)

A/FX Nut said:


> One more thing you can do is, Ohm the armature. Make sure all three windings are equal or close to it. I've had one read at 14.5, 14.6, and 34.2. That was one of my armature temperature problems I've had in the past.
> 
> Randy.


Yeah, that's pretty awful.... Although the idea that some folks have that if all 3 poles aren't within .1 ohms of each other isn't really all that accurate either.

I have a couple that measure out 16.5, 17.0, 18.1 and are the best running arms I have.


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## 00'HO (Nov 19, 2004)

*Wow*

I'm with SF on this post

:freak: :drunk:










*Glad you discovered your jam up front.*

*Use an independent front end on all runners.*









*Then those cars can get out of the back row and up to the front.....*

http://www.daveshoraceway.com


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## A/FX Nut (May 28, 2004)

martybauer31 said:


> Yeah, that's pretty awful.... Although the idea that some folks have that if all 3 poles aren't within .1 ohms of each other isn't really all that accurate either.
> 
> I have a couple that measure out 16.5, 17.0, 18.1 and are the best running arms I have.


I agree with you Marty, alot of times the ones I ohm are from .1 to .6 difference from each other.
Randy.


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