I'm slowly expanding my JLTO collection and in trying to get them to look nice and run well I find two issues consistently slow my progress...

1. In my opinion, the weakest link on the JLTO chassis is the cantilevered brush "spring" configuration. Anything that causes one of those to be distorted or to provide unequal tension seems to result in the dreaded motor squeal. Some new cars squeal right out of the package and those inevitably have brushes sitting at different levels. Has anyone discovered tricks for dealing with this? I bought a bag of bare chassis and swap to a new one that looks to have well balanced brush springs if I get a car with motor squeal. It works and is economical but it would be nice to be able to actually fix the bad ones. Any suggestions? I have read great things about JB Thunder Brushes. Would using those widen the tolerance on the brush spring positions? Are the NOS Aurora TJet chassis sold from various sources less likely to have a problem with this issue or do they have the same thin strip material bent into a v?

2. I really like the look of the RRR wheels and in most cases they press on straight and run smoothly even though the tires are just so-so with too many having nicks that may sometimes catch on rails. In another thread concerning RRR wheel/tire sets, a few of you indicated that you were able to "tune" them and get a smoother ride. Outside of carefully prying them off and remounting, what are you doing?

In my opinion, the weakest link on the JLTO chassis is the cantilevered brush "spring" configuration.
I totally agree. This is a design flaw inherited from the Aurora TJet and original AFX design (Yes, Aurora shipped plenty of flawed products too.) There's not a lot of margin for error and quite a few of the JL TJets seem to be plagued with problems in this area. One of the brush springs on the JLs is too long and it's hard to get the dang thing centered. The notched & domed brushes make the problem worse because the brush spring notch has to be perfectly centered and level in the hole. Over the course of the JL releases they did try to do a better job of getting the brush springs configured better from the factory but without fixing the root cause it's never perfect. They also kept changing the size of the brush holes: in R1 they were too tight for JBs but a couple of releases later the holes became so large the stock brushes seem to be swimming in the brush holes. They did the best job with R6 and R7. The R6 and later are the best JL chassis from a brush hole fit perspective. Couple an earlier bad brush spring chassis with a wobbly off center mounted JL arm and a bent axle or two and you have the makings of one low down slot canine. Woof woof.

JBs or Wizzard aftermarket flat brushes do work well in the JL TJets. But properly setup stock brushes work very well too. I use the JBs or Wizzards (or even NOS Aurora) in cases where I just can't get the stock notched brushes to fit right and the chassis is otherwise good. Some are concerned by the fact that flat brushes can spin in the holes. (JBs seem to like to spin even more.) Allegedly, you can etch a fine line or X in the bottom of a flat brush with an XActo blade to stop the spinning.

The TJet brush spring design should have been avoided by JL in favor of something better, like the Magnatraction setup or brush cups.

Yep, there are QC issues with the JL cars......no doubt.

My cars "squeal" when th armature shaft hole in the bottom of the chassis is bone dry, the car also slows noticably when it squeals. A teeny tiny drop of oil cures the squeal, and the slowness.

The cars I have seem to "growl" in a very un-intimidating way when the arm is wobbly or the comm is warped. I'm experimenting now with straightening the arm and flattening the comm plate. So far, not much difference in performance.....Only a sample of one at the moment. I have some that are really bad, so there's not much to lose by experimenting.....But, one of my fastest JL cars has a very warped comm plate, so it may be a futile effort.

All pancake cars squeal when the bottom hole is dry. Don't let it squeal for long or the hole will enlarge. That particular hole needs to be lubed with a heavier lubricant than the rest of the friction points on a pancake car. The trick is to find a lube that will flow into the hole and coat the armature shaft but not thin enough to wick into the motor and get on the commutator plate and brushes or drip out the bottom. The white lithium grease that comes buttered all over new JL chassis is not too bad for the bottom hole but it is too heavy for the rest of the chassis. The original red racing oil works well for the bottom hole too. There are some lubricants that flow on thin but the thin part quickly evaporates and leaves a film that clings to the surface. I've heard that STP, Slick50, and automatic transmission fluid (ATF) all work well for the bottom hole. Even petroleum jelly and lithium grease are probably better than thin oil in the bottom hole. Whatever you use, always oil sparingly.

The growling is a sure sign of something out of round. Another source of roughness in the JL slot cars is poor gear mesh on the top gears on the gearplate. Look at the mesh of the three top gears from the side. The arm pinion is usually much higher than the idler gear and cluster gear. In some cases the cluster gear flops around like a warped LP and rubs against the chassis clip. There are a couple of things you could try. At the very least the arm shaft should be flush with the top of the arm pinion gear. Many are not. I actually prefer to have the arm shaft protruding through the gear a bit. Compare the gap under the arm pinion between a stock JL TJet/XT and an Aurora TJet/AFX. The JL gear is set way too high. If you can, insert a feeler guage or shim that of the proper thickness under the arm gear and then press the gear on until it is flush with the shim. Keeping the idler gear from flopping around makes a big difference in smoothness. Keep in mind that raising the arm will lighten the brush tension so you may have to readjust it after the fix.

On some JL chassis I've found that running a brass idler gear makes the whole thing smoother, but a bit noiser. The gear mesh between a brass idler and a plastic cluster top gear is a bit looser than I'd like but it sometimes tames an otherwise twitchy JL. You'll notice a big difference in the braking/coast with a brass idler. Finding small hole brass idler gears is a bit of a challenge. Aurora must have started shipping them at some point because I have several from my original HO collection.

Another thing to try is putting a spacer under the idler gear to try to split the difference between the height of the arm pinion and the height of the top cluster gear. Sometimes just flipping the idler gear over so the flat side is down helps.

on my dragstrip i replaced the brushes with tjet springs shoot it up with oil or vasline the car run smooth and quick just cant revierse the armature i even try rolled up aluminfoil it work too

I'm finding that a tiny amount of vaseline on the tip of a toothpick applied to the arm shaft hole seems to keep the shaft lubricated without messing up the brushes or the track. That eliminates some squeals and improves performance on some cars that haven't had maintenance in awhile.

I also experimented with BSRT copper ski shoes and they help smooth the ride on some of the twitchier JLTOs, so they're good to have around. It's as if the juice gets to the motor more smoothly. Oddly, they actually reduce the acceleration and increase the overall lap times on cars that already perform well with the stock shoes. I didn't expect that. I'm just guessing that they must have more resistance but a smoother contact. I thought that copper would have less resistance. Another day and more to learn...

TK Solver,

My guess is they do two things, one restrict the travel of the pickup shoes. Look with the car in your hand look and see how much of the pickup shoe is below the front wheel, then compare it to a stock set of pickups. Two lay flatter on the track

Roger Corrie

My guess is that the ski shoes reduce shoe tension on a car that otherwise has about the right amount of spring for the stock shoes. As an experiment try stretching the pickup shoe springs (or use slightly longer or heavier ones) on a car with ski shoes and see if you get some of that horsepower back. Limiting shoe travel is typically done in conjunction with increasing shoe tension by using longer or thicker springs, unless of course the stock springs already provide too much tension and need to be managed through limiting shoe travel.

Shoe tension is a major contributor to power on all slot cars, magnet or gravity traction. The tradeoff is handling, where too much tension reduces handling. Limiting shoe travel mitigates some of the handling tradeoffs.

Thanks for the ideas, AfxToo. The BSRT copper shoes have a much longer stepped portion in contact with the rails. I'm sure that reduces the tension, making them deflect more easily. I consider shoe tension as more of a "stage 2" refinement with stage 1 getting squealing cars to run smoothly. Other stage 2 refinements include loosening the rear body screw and using silicone tires.

There seem to be two classes of squealers -- ones that consistently squeal and ones that intermittently run a few feet and squeal for an instant. Consistent squealers generally have a problem with the bare chassis (brush springs and holes and arm shaft hole) as whenever I swap that the problem goes away. The intermittent "missing" is more puzzling to me. Could it be something to do with wobbly non-centered armature assemblies causing the interface with with the brushes to periodically go "out of phase"? I have spare arm plates I am experimenting with but the results haven't been consistent. Maybe wobbly arms are just more common.

If all this is obvious to you T-Jet Ph.d.s out there, I hope you're enjoying a few good chuckles at my expense. Meanwhile, I'm enjoying the undergraduate experience.

With all the goofy classes offered at various universities these days it seems to me that someone could easily collect enough material for a course in "Slot Car Physics and Design". Could be pretty popular...

Interesting. Squealing is typically an under oiling problem. I'll assume you are oiling the top hole where the arm shaft goes through the gearplate, under the arm pinion. The wobbling arms may be scrubbing the petroleum jelly off the lower arm shaft and bearing surface. The ideal oil would flow into the hole and coat the entire bearing surface with a resilient film that doesn't drip out the bottom or migrate up into the commutator. A few people have come up "secret" lube mixtures that go on like a liquid but quickly dry to a thin film that lasts better than other standard lubricants.

Here's what I do. I like to slightly chamfer the bottom hole inside the motor. I just use a small phillips screwdriver and spin it a few times in the hole to form a slight bevel on the top edge of the hole. You don't want to ream the hole, just bevel the uppermost part! That's why I use a phillips screwdriver and not a cutting/reaming tool. This does two beneficial things: 1) it helps hold the oil a little longer because oil flows more slowly at an angle instead of vertically and 2) it provides a small oil filled cavity where the arm shaft can't scrub the oil off the bearing surface. If the chamfering process produces a slight lip at the edge of the hole - all the better, it provides an added barrier for oil getting onto the commutator.