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Discussion Starter #1
I have three JL X-Tractions from the very first release. I have the cars running great except for one problem. There are a few curves on my track where the cars appear to get "stuck" right in the middle of the track piece (not in the joints). As the car starts to drift, it will suddenly stop in place with the rear wheels spinning. I haven't drifted out far enough to lose contact with the rails.

As I look at the bottom of these release one chassis, I believe the problem must be a clearance issue. It appears that the chassis under the outside of the rear magnets may be the lowest hanging part of the chassis and I'm thinking this area may be hitting the rails when the car drifts, lifting the (stock size) rear wheels off the track. This only seems to occur on some curves and I'm guessing these may be the curves with the highest rails. although they may only be higher by thousandths of an inch.

Has anyone seen this or a similar problem before?

Thanks...Joe
 

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Try swapping the newer, larger stepped pick-up shoes onto those chassis and the problem should go away. The skinnier shoes from the original releases can be good for "lowering" cars that may otherwise want to roll over in the curves but the problem you're reporting can arise.
 

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LED Burner Outer
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I agree. I had more than a few chassis that would bind on a few curves, and I think the skinny ski shoes were the culprit. To find out for sure, swap shoes with a wider ski shoe'd car and see if the problem moves to the new car, and the car with the curve problem gets better.
 

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Discussion Starter #4
Thanks for the replies guys.

I don't understand why changing out the shoes will alleviate this problem. You both seem to have had success in swapping out the shoes, so there must be something to it. What shoes are considered "larger shoes"? I tried swapping in a pair of Aurora long step shoes but that seemed to have no effect.

It certainly seems as if the bottom of the chassis is hitting the track (probably just the rail). I have already replaced the front tires with slightly larger O-Rings and there is not a lot of room in the rear wheel well to allow for a much larger tire. I'm guessing there are only two solutions. Either (a) file down the offending rails or (b) sand down the bottom of the chassis. It certainly looks like there is almost no space between the bottom of the chassis and the track. In fact, a piece of paper slipped under the car while it's on the track will contact the bottom of the chassis.

Thanks...Joe
 

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I'm guessing you're running on a routed track. The problem with the thin ski shoes is actually in the slot. Routed slots are wider than plastic track slots. It not by much, but it's enough to have the the ski shoe slide off the rail then get wedged which stops your car and make it spin its wheels.

The wider AW shoes will not slide off the rails in the turns an tada, no stopping, wedging and wheel spinning.

Also, if you didn't already do this, give your ski shoes a step, between 1/4 to 1/3 the length of the shoe. This will leave less shoe surface to get stuck on the rail.
 

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Here's a link to a pic of the latest chassis with the bigger shoes... http://stores.budshocars.com/-strse-1109/1-AUTO-WORLD-/Detail.bok

These shoes don't seem to bind on the rails in the turns as much as the skinny ones from the first X-Traction release.

I suppose if your rail is high enough, it could still bind though.

Which guide are you using in the slot -- the "pin" or the "rudder"? I'm wondering if one side allows the chassis to sink deeper into the slot with that first release.
 

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LED Burner Outer
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You know, one other thought occurred to me. If the rear axle holes are either sloppy or miss drilled, it could drop the back of the chassis down enough to catch on a rail. If the wider shoes aren't the solution, maybe try swapping out that chassis and put it on something that will accommodate larger rear tires and see if that solves the issue. The rail height on my old L&J track was abnormally high causing all kinds of problems with any magnet cars (they'd stick where they sat until the trigger was pretty well bottomed out, causing the car to promptly fly off the first curve it encountered). Needless to say, most of my Xtractions went bye bye since they were unusable. A few of the handful that did manage to make some laps did bind in certain corners, and for the most part it was because of the skinny ski shoes binding up. A switch to wider shoes did cure the curve bind. I wish the other problem could have been an easy fix.
 

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Model Murdering
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Just guessen'

Keep in mind that the pick ups become part of the chassis when coil bound.

It should be noted that the AFX shoe design limits travel at the hanger window, when compared to most all previous slot car ski type shoe designs. It was the beginning of dropping the CG that was the fashion of the time.

As JoeD points out, porked axleholes, improperly sized axles, tire profile, and excessive rail height contribute both individual or isolated quirks...

...and ALSO conspire to produce "difficult to diagnose effects" when in combination.

Basically it's a high center effect. At the point the shoes get packed up against the chassis and coil bind, increased or weirded out rail height pushes the chassis up off the track surface. Tractive effort goes with it, so spin offs or burn outs ensue. Remember that the chassis may already be sagged closer to the rail because the bores are wallowed or oversize. Consider it a preload and therefore additional shoe travel that is already used up.

I call it sledding, because it's not unlike sledding down suicide hill and hitting a patch of exposed pavement. Yer gliding along and then ....scchhhhhhhhh! In the straights you'll see the car bog down, but it'll usually grind it's way across the offending stretch. In the corners the tail gets light, so unless you have enough momentum to slide through the offending stretch you'll stall. It also makes a unique sound thats easier to pick up in the straights.

Bottom line is that as slotters we try to squeeze tolerances. In doing so we often exceed the minimum requirement for operational clearances.

I'm not surprised at all Joe. It happens to me all the time when lowering and modifying my drop axle customs. Ya may have to moosh the rail down, or remove some meat at the bottom of the hanger window, or hike your tires, super glue your axle holes smaller, or over size your axles.

Unfortunatly the chassis in question was a sloppy affair. I'd take the body off, remove the guts; then poke my finger in the comm pit and push the chassis through the offending stretches. All the while keeping my good eye on the hanger windows. If the effect is in play you will see the hanger's window sill clearance vanish, as well as a change in the feel in your finger tips...and or an auditory change in the sound of the shoes as they bind against the chassi bottom.

Under ideal conditions your shoes should operate with the chassis hanger tit in the middle of the window so they can fully compensate for the varying demands of rail height. Where we really get into trouble is expecting narrow shoe travel windows to operate correctly on a sagged chassis when the rail height exceeds the travel tolerance of the pick ups.

Dunno if this is gonna help....but it do happen here.
 

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Discussion Starter #9
Hi Guys,
I am going to try a few of the suggestions you've offered, especially putting on larger tires (with no body). However, I did take a good look at the car as it gets stuck.

It looks like the shoes are not binding on the rails. I have had that happen before and you can not only see the shoes leaning against the sides of the rail, but can feel them release when you pick the car up.

It also looks like the shoe hanger "tit" (as Mr. Hall so elequently titled it) is in the middle of the shoe window with plenty of room left either up or down. This doesn't mean I am not getting coil bind, but it does seem to eliminate the issue of not enough room left in the window.

But as I said earlier, if I put a thin piece of paper on the track and then put the chassis on the paper, sliding out the paper makes the chassis move. The paper is only under the part of the chassis from (about) the oil hole to the rear magnet, so it's not getting hung up on the shoes. With so little room under the chassis, it's no wonder it bottoms out.

I am running on Mattel plastic track and using the pin side of the guide.

Thanks...Joe
 

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Model Murdering
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I'll also add...

...that just because the hanger window is used up doesnt necessarily mean that shoe is coil bound. You can have one or the other. Either scenario makes the chassis and the shoe one with each other.

Joe, did ya measure the OD of the tires? Are they the stock AW issue? Weird Jacks? er what? Shrinkage certainly isnt out of the question.

Ya may also look at blocking the bottom of the offender chassis'. Somewhere in "Shoe's" stuff there's a tute with the 411 on that.
 

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You may want to try leveling the bottom of the chassis. Check this how-to. It's basic stuff, but will give you some ideas on smoothing the chassis' bottom side. It covers the pick up shoe adjustments mentioned here also.

Tuning the Pancake Pt II

-Paul
 

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Discussion Starter #12 (Edited)
You may want to try leveling the bottom of the chassis. Check this how-to. It's basic stuff, but will give you some ideas on smoothing the chassis' bottom side. It covers the pick up shoe adjustments mentioned here also.

Tuning the Pancake Pt II

-Paul
Bill,
The cars are using the stock JL tires (remember, these are release 1 JL chassis) and looks like they are 437 OD. I want to try a larger OD tire. I may have to do that with the body(s) off as there isn't a lot of wheel well room.

Paul,
An excellent tutorial - really excellent. While I would prefer not to sand the bottom of the chassis, that may end up being the solution if I cannot get a larger OD tire to fit under the body (without modification).

All,
Looks like something I have discovered is the problem appears to occur more frequently when the rear of the car drifts off onto another piece of track (for a four laner). For example, let's say I have 9" and 12" curves nested and I am on the "outside" lane of the 9" curve. When my car drifts, at least one of the rear tires swings over to the 12" curve. Because there is so little clearance under the chassis, if the 12" curve piece is any lower than the 9" piece (or there is the slightest gap between the pieces), the car bottoms out. I was able to (somewhat) verify this by slightly propping up the 12" curve and the cars no longer got hung up on that particular piece of track. The height difference appears to be very very slight, but it may be the reason the cars get hung up on certain curves. Of course larger tires would alleviate this condition.

This could also be verified by seeing if the car gets hung up on curves where the rear tires stay on the same piece of track, like when you drift from the inside lane.

Thanks...Joe
 
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