# Stumped With This MagnaTraction



## gonegonzo (Jan 18, 2006)

Ok , I'm not the best pancake mechanic around but I can make them run thru trial and error at times . Now I have a MagnaTraction chassis that is giving me fits . It used to be one of my hot cars but thru splitting hairs , trying to get better and smother performance I've got it wayyyyyyy out of whack .

It ran well with an Super G+ stell guide pin , slip ons on the rear and o rings up front but on occassion just jumped and jerked but not constant . So , I swithed to silicone over sponge in the rear . That didn't work and it's still the same and maybe even worse . 

I checked the guide pin and it has good bottom clearance . The shoes look good as far as spring tension and overall condition goes . I checked the chassis bottom and see no rub marks . I see ample clearence under the chassis when holding it up to a light . 

Now it seems like it needs weight added like the 1/24th scale cars do for handling . Could the problem be the traction magnets ? By feel they seem OK but how do you test them to be certain ? 

The car is fast but the handling has me baffled .

Thx , Gonzo


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## WooffWooff (Dec 23, 2009)

*Jump'n & jerk'n AFX/MT.....*

Man that's hard to diagnois, but there's bound to be a simple fix. Are you sure the car rolls perfectly smooth (press'n on hubs can oh-so-ever slightly bend an axle, and collisions with heavy cars or the floor can mess-up a front). That would make it hop and not handle turns at high speed, but jump'n and jerk'n sounds a little different than a bent axle. Maybe the pick-up shoes aren't dialed-in good'n flat? Anyways-Good luck with the AFX/MT...........wooff


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## twolff (May 11, 2007)

Have you run it w/o a body? The inconsistency in the problem indicate that you might be getting some body/tire or body/gear interference.


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## SuperFist (Aug 7, 2005)

It's probably the pick up shoes, because that's the root of all evil.

But check your cluster gear and pinion gear mesh.
Those are the parts that have failed on most of my MT cars.

__________________


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## bearsox (Apr 22, 2006)

Hey Gonzo ,
 I wonder if it could be in part due to a tiny roll in the car. Bear with me on this.... if your going into or out of a turn braking rolls the car forward a tiny bit. Moving thru the curves rolls the car a tiny bit. Coming out of curves and getting on the throttle moves it again a tiny bit. Each thing moves the car in a different direction be it forward , back or sideways. So when you check clearance at a time when the cars is not moving and flat no problem is seen as the chassis never shifts. My thought would be to take laps with a note pad or good memory at hand and keep track of where all the problems occur and when etc. If for example it's as you just enter a turn i would deduce roll forward so look at guide and both shoes. So swap the guide for another metal and or original pin and note. If that don't do it swap shoes for a non restricted set etc. Anyway you can figure the possible offending area of car possibly by this method then narrow what to look at. In a curve look at right or left side , out of curve and on throttle tires and axles expressly rear . The key would be where things go wrong as that would be the clue i think. Hope this helps you out .

Bear :wave:


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## gonegonzo (Jan 18, 2006)

I'll go thru it all again after hearing this input . I don't think the axles are bent as it feels smooth running it on the track surface . I mounted my rears with a press and was particularlly careful of getting them strait . However , things do happen and I will check it again .

I did run it without a body and it didn't make a difference . Actually it runs better with the body on .

I thought too that it might be the pickup shoes . However , they do present a good pattern of wear . What do you mean by less restrictive shoes ?

I will go back to the original guide pin . I was going to that but became frustrated and had to walk away . Ever been there ? 

I see what you mean about roll . It never occurred to me about that . I presume your speeking of the roll created by the back lash in the gears etc . ? Now that you mention it the deslotting happens when throttling up out of the bends . The hopping and jerking is present when running a long straitaway at full speed which makes me think tires . However on those long straits it goes like this : smoothhhhh / jerk jerk hop / smopthhhh / jerk jerk hop . By then I'm at the end of the strait going into the bend and when throttling up to come out , the car spinns out . The tires are clean as well .

The orings are new , the rears tires are new and I did lightly sand the sheen off of them after mounting . When sanding , they seemed to be running true .

Like I said before , I've done somthing here as the car was tolerable before . I was just going for that fine tune and munked somthing up .

Thx , Gonzo


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## Grampa Ho (Feb 25, 2009)

I have found that the springs under the shoes in the cup can become weak and not exhert the pressure needed upon acceleration resulting in the shoe losing contact with a force necesary to maintain an even speed.
As for the jumping out part, the same can be said that the contact is good at that point and your machine just torques out.
Try a stiffer spring on it and see if that works and a higher ohm controller will help smooth exit speeds.
Thats what I know and now you know, ya know?


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## WooffWooff (Dec 23, 2009)

*It might be.......*

...the idler gear being too loose and jump'n around, may even be hitting the gearplate clamp. AFX/MT chassis are plentiful so if it's still a mystery, just chunk-it and start fresh..........wooff


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## bearsox (Apr 22, 2006)

gonegonzo said:


> However on those long straits it goes like this : smoothhhhh / jerk jerk hop / smopthhhh / jerk jerk hop .
> Thx , Gonzo


Does this happen on ALL straights or just a certain one ?

Bear :wave:


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## Rolls (Jan 1, 2010)

If it was "a little rough, a little rough, a little rough" before the hop-jerk, I'd be inclined to look first to tire and axle true-ness. But if its very smooth, very smooth, very smooth, before the hop-jerk; that would steer me to the pickup springs (too much or uneven tension) or a subtle, but troublesome bend or tilt in the shoes. 

Is it possible the new o-rings up front could've lowered the front end just a bit, changing the shoe and shoe spring set-up? Maybe worse if the new rears are just hair bigger diameter?

Next, I'd look for some weird gear binding, maybe in the crown gear, because it could get out of whack during tire/wheel changes. 

Just my thoughts. Hope it helps. I know it's frustrating when a good car turns bad mysteriously. (edit: I see several more good ideas came in while I was typing)


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## TheRockinator (May 16, 2007)

*Go Back*

You seem to know what you've done to the car since it was "tolerable" So undo all those things and see if the new problems still exist. If it still runs bad then you know something changed with the car because of the tweaking. If it's back to normal then it's the parts you used. My bet is it's the rear wheels. Even with a press they can be a bit crooked. If the wheels themselves are out of round the the hopping at speed would be almost expected. My 2nd thing to look at would be the armature shaft. If it's bent or if the gear is too far up so the armature floats too much you could have smoothness issues. If there is too much play in the arm to gear distance your gear could end up lifting out of the ideal contact with the idler or even cause binding along the entire gear chain.

Later The owner of the world's fastest Non Mag AFX with a neo dot traction magnet (unofficial)  Rockinator


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## Bill Hall (Jan 6, 2007)

Oh yeah been there many times Gonzo...set the metal pin aside and try something different.

Try the stock flag or pin.


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## Voxxer (Oct 25, 2003)

*Afx*

Hi:

One thing I noticed you stated is that it runs better with the body on. Just a thought, but you might have a bent chassis. When you put the body back on, some how it helps " unbend" the chassis. With the tires on, tap each tires to see if the chassis goes up.

Second, take out the guide pin, replace with stock and run the car without the front tires.
This should help find out if the front axle is bent and see if the problem is with the pick-up shoes.

Third what track are you running on?

Fourth, what is the o.d. of the rear tire on the rim.

Fifth, is the free rim on the front to loose, when twisting up and down on the axle

Hope this helps

Voxxer


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## smalltime (Jun 3, 2006)

Check your track, make shure you don't have a rail stickin' up on that straight.

Then check the shoes for twist, this is done by looking directly at the front of the car, and adjusting the shoes so they are flat in the left/right direction.

It sounds to me like the shoes are catching a rail.


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## old blue (May 4, 2007)

Check the muffler bearings. Common issue with my cars. Either that or the operator nut. Either way You should be fine in a week or two!!!

OB


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## gonegonzo (Jan 18, 2006)

I thought of backtracking but would still have the ruffnes .

The O rings are .010'' smaller than the stock rubber tires . 

I didn't think about the springs under the shoes . Will the new ones from AW work on Aurora ? My parts guy is out of the springs for A/FX right now .

I didn't check the arm or idler either . I will thou . Good thought .

Still working on it ,
Gonzo

I didn't consider the gear binding either . It could be loose back there . That is my next check .

The car sits level . No rise when pushing on wheels .

Yeah , this happens on all straits and deslots due to spinout on all bends . The Wiz track I'm running on is OK . It happens in all the lanes . It's deffinately the car .


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## Rolls (Jan 1, 2010)

For my cars, you're right. First thing I need to check is the nut that holds the controller.


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## AfxToo (Aug 29, 2003)

My leading suspect would be shoe springs. If you have a set of AFX power steering kit shoes on another car give them a try. The thing that the PS kit brings to the table is a lighter spring and restricted shoe travel. You can experiment with shoe restriction on the existing shoes using tape and if it works out switch over to shrink wrap for a more permanent solution. Make sure your shoes are running flat too.


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## bearsox (Apr 22, 2006)

gonegonzo said:


> I thought of backtracking but would still have the ruffnes .
> 
> The O rings are .010'' smaller than the stock rubber tires .
> 
> ...


Ok to quote Mars Blackman ( NIKE commercial ) it's gotta be the shoes ! Well caused by XXXX. As stated above you went to a .10 smaller Oring front that changed the angle of the shoe but didn't i suspect adjust the shoe . You then changed to a silly sponge set of tires and i would bet again didn't adjust the shoes. Lets for a minute say the the front got lower and the rear got higher ..... if only marginally this impacts the angle the shoe hits the track and changes how the car runs down straights, rolls in corners , and even conducts electricity. Angle to steep forward and you can lose part of contact patch and power as well as create roll in corners and catch an edge at track joints or rough patch on a straight ! Also side effects could be dropping the front nose would impact shoe spring tension and lever action the rear of car. All this would and could account for what's happening so it is a possibility. Hopes this helps .

Bear :wave:


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## joegri (Feb 13, 2008)

i,m with grampa ho if you swap out the old springs for new ones maybe even new shoes too it might behave like it should. worth a shot. but please report back what the mystery prob is . i like to know.


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## Voxxer (Oct 25, 2003)

*Brush Springs*

Hi:

Have you looked at your brush springs. After checking and removing the top gear plate several times, you might have compacted the brush springs. Also, if your complate is tilted, it will only hit the brushes on the down side. Since the brushes are not hitting the com at all times this might cause the start and stop of the car.

Also, ream out the brush holes, the brushes might be catching on the rims and not " floating" in the hole.

If the brushes are not touching the com and not even, the will be spinning in the hole and touch the com only in the high places, thus start and stopping.

Gears:

With the front of the car pointing towards you, spin the right rear wheel ( using your right hand ) away from you slowly. If the gears binds or stop, you have a gear train problem. If this happens, check the rear gear to see if it tips up to one side when it stops or binds. If yes, the rear gear is to loose and needs to tightned. NOTE: this also can be caused by the arm shaft holes on the top plate and chassis being to big, thus you will see the pinion gear tilt to one side.

Second, same position, place your left thumb, with little presure, on the pinion gear and spin the gear right wheel TOWARDS you. While spinning the wheel, listen and feel, if the axle gear and rear gear are skipping.

If so, your axle gear needs to be schimmed over from the chassis wall towards the axle gear.

Voxxer


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## joegri (Feb 13, 2008)

voxxer very good info. in the near past i did,nt pay any attention to gear trains untill i read fray tuning 3 or so times. i get it a lil bit and some recent builds have come out better cause of reading,and also watching this(tuning)section. and rolls thats funny man!! that will be the first thing i check tonite when i go down to the cave!


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## Voxxer (Oct 25, 2003)

*Afx*



Voxxer said:


> Hi:
> 
> Have you looked at your brush springs. After checking and removing the top gear plate several times, you might have compacted the brush springs. Also, if your complate is tilted, it will only hit the brushes on the down side. Since the brushes are not hitting the com at all times this might cause the start and stop of the car.
> 
> ...


Amendment:

Second part - when using little pressure to hold the pinion and rolling the right rear wheel, when car is facing you:

Addition - Gently pull the right wheel to the right, or from the chassis, so that the axle gear is at it's most distance from the cluster gear. This will give you a reading if the gears are not meshing and skipping.

Voxxer


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## gonegonzo (Jan 18, 2006)

I'm getting a lot of good info here . Thx guys for the replies . Tonight I'm working on the car again and hope to conclude the problem . 

I'll keep you all informed and let you know how it turned out .

Gonzo


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## Gary#8 (Dec 14, 2004)

The spinning out might be getting on the throttle to soon. Slot cars have a locked (posi traction) rear end and will spin out if given to much throttle comming out of a corner. Try waiting till rear of car is on straight before throttling wide open. Jerking sounds like pick up shoes or springs as said earlier. Could be shoe hanging up on side of rail in corner. If you have another similar car that runs good try switching the springs and shoes from that one. And again lets us know what worked.


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## gonegonzo (Jan 18, 2006)

Okkkkkkkkkkkkkkk , I checked the rear gear cluster and pinion . They were loose but not dramatically loose . I tightened it up and the car ran a lot smoother but still did a jerk once in a while .

Then I went back to my original rear tires . It became worse again . Took them back off , threw them away and installed another new set of tires . The car smoothed out and is running fine . I then threw the first set of new tires away and out of my box .

It still slides out once in a while but I'm sure that I'm overdriving it trying to make friends with it.

Durring this course of chaos , I dismantled the entire car one part ata time to try and catch the problem . Now , it's pretty much an all new component equiped car but the results are very rewarding .

I thank each and everyone of you for your tips and suggestions on this .

Thx Gonzo


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## Pete McKay (Dec 20, 2006)

Pfister valve, gotta be.


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## noddaz (Aug 6, 1999)

*Shoot. I missed the whole thread...*

But glad you have it fixed.
I was going to suggest that the tires were to small in the front allowing the shoes to bottom out on the front spring perch...
The 2nd thing I was going to suggest was to pull the magnets and brushes (and brush springs), re-assemble the chassis with out them and push it around to see if it smooth with out binding.
While you are pushing the chassis around "vroom, vromm" sounds are optional.


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## SuperFist (Aug 7, 2005)

Pete McKay said:


> Pfister valve, gotta be.


Obviously I know how to repair those.

__________________


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