I've been playing with JLTO quite extensively for the last several weeks. I have matched magnets, restricted pickup shoe travel, ground tires, replaced the rear axles with wider (~1 5/16) drill rod axles, and cobbled up an inexpensive wide and weighted independent front end using stock tjet hubs, a drill rod axle and brass weights.

I've been able to consistently get vastly improved performance.

After those repairs, the weakest remaining link I found on the JLTO chassis is the combination of the driven gear on the top plate and cluster gear shaft and cluster gear (the portion of the gearing that transfers power from the top plate to the crown gear on the axle). There's a tremendous amount of slop in that section of the gearing. Aside from simply replacing that portion of the gear train with Aurora parts, has anyone figured out a fix for this?

Thanks
Mike

Mike-
You have done far more than I have with the JLTO chassis. I can't help you with the gearing, but I do have a couple of questions.
How well does restricting pick up shoe travel work and how do you do that?
Secondly, I have toyed with weighting the front end, but it always makes the rear end a little squirrelly. I am assuming the tires that you ground down, give enough traction to offset the weight in front? I have tried the brass front end kits, but I get the same problem.
Jim

I use the weighted front ends front from JW's (http://www.csonline.net/vwalters/) with great success. Blueprinting the chassis never hurts and with many has helped immensely. Pick-up shoe adjustments, both travel and contact are critical ones, especially with both types of JL cars. If I recall correctly, for the original Magnatractions, a replacement shaft for the cluster gears was available which was like a screw where one could adjust the amount of play in the gear. Something like this is what is needed here. To help clean up the sloppy wobbly idler gear I have found sleeving the post on which it turns with brass tubing to work quite well. The idler gear itself will need to be sized for clearance on the new sleeve. I've tinkered with a few other ideas but left them at that since I have gotten more into magnet cars. If there seems to be an interest I my just get back down into the dungeon and see what I can come up with!

JW's sells screws to replace the cluster gear shaft on the M/T's-X/T's. They are four for a dollar, the part number is X15.

Bob Weichbrodt
"Rawafx"
A and H Hobbies
Clemmons, NC

mking, nothing short of replacement with brass gearing seems to do the job completely. It may help a bit to lower the top gear so the shaft protrudes a bit more on top and the gear has less vertical slop. I've tried the same thing with the arm pinion to bring it more inline with the idler gear. The more inline you can get the top gears the better off you'll be.

Blueprinting the chassis never hurts and with many has helped immensely
I understand blueprinting with respect to spec built automobile and other engines but what exactly does "blueprinting" mean for a slot car chassis like the JL variety? What reference specifications do you use for establishing the proper tolerances? What parameters are being blueprinted?

Restricting pickup shoe travel does several things.

First, JLTO have pickup shoes springs that are too strong. Sure you can remove a coil, but thats a pain.

By restricting the pickup shoe travel, even strong springs will not push the car out of the slot.

the next thing restricting pickup shoe travel does is to help increase cornering speed.

basically, with unrestricted shoe travel, as a car corners and starts to deslot, the pickup shoes extend and keep the shoe in contact with the rails, letting the car power itself out of the slot. restricting pickup shoe travel means that as the nose of the car lifts up (and the pin moves up and out of the slot), the pickup shoes lose contact with the rail. this slow the car down, causing the nose to drop. properly setup, you can actually hear this working. as the car goes into a curve, you can hear the motor stop, and sometimes you can hear the car drop back into the slot.

i use heat shrink tubing. i try to get the pickup shoes just level with, or a little bit lower than, the bottom edge of the tires. some people actually bend the pickup shoes, but thats permanent, and the heat shrink tubing can be removed. once in a while the heat shrink tubing does work its way loose, but its easy enough to replace. one disadvantage is that the the hanger needs to be bent forward a bit so the tubing can clear the chassis, and on some bodies the hanger then rubs against the body. i have had to dremel several willys bodies to provide clearance. now that i think of it, i could also have dremeled the chassis.

Secondly, I have toyed with weighting the front end, but it always makes the rear end a little squirrelly. I am assuming the tires that you ground down, give enough traction to offset the weight in front? I have tried the brass front end kits, but I get the same problem.

On some cars too much weight on the front end does seem to make the rear end squirrely. Better and smaller diamter tires on the rear can offset this.

When I started learning about Fray style cars, I was surprised that SMALLER tires are better. Think of all those kids in the 60s and 70s hacking away at wheel wells to add larger tires! Yes taller tires can add top end speed, but the loss of handling generally outweighs the benefit. Fray rears are as low as 340 (i think weird jack stock silicones are 390 or so). Smaller rear tires substantially improve handling, and can help tame a squirelly rear end.

JW fronts can be up to 4.0 grams, i have been using brass weights that add 1.4 grams to the front axle. That has been working well for me, and the weights are fairly inexpensive (brass wheel collars for planes or RC cars, 12 for $4). You have to replace the front axle, but i bought ALOT of 1/16 drill rod. My axles arent as precisely cut as JW or Wizzard axles (i use a dremel and my eyeballs), but they work just fine. The stock JLTO axles are actually pretty good, its just the axles holes (especially the rears) are oversized and the axle has too much slop, which can show up as wheel hop.

I understand blueprinting with respect to spec built automobile and other engines but what exactly does "blueprinting" mean for a slot car chassis like the JL variety? What reference specifications do you use for establishing the proper tolerances? What parameters are being blueprinted?

In a nut shell, basic "blueprinting" for an HO (pancake) comes down to:

1. Aligning holes such as axle and armature holes and reaming them to an equal size with the desired amount of clearance for the axle. If axle holes need to go to a larger diameter leaving too much clearance then the axle dia. will need to be increased or holes sleeved. Chassis where the armature holes are to large can be salvaged by sleeving also. Many groups do not allow such a modification thus the chassis can only be used as a runner.

2. Checking chassis alignment and making adjustments as necessary. A chassis that has a tweak that cannot be corrected by hand may level out by boiling it on a jig. The fitment of the gear plate is to be included into this process.

3. Checking all rivets on chassis and tightening them as necessary. Also at this time check fitment and alignment of the pick-up shoe hangers and adjust as necessary.

I use scotch tape to restrict the shoes......just try not to touch the sticky side as much as possible, and clean hands helps, too. It holds and works nicely, and is easy to remove if you make a mistake, or if the tape gets old and needs replaced.

mking,

If it's not too much trouble, I would like to see a photo of how the shrink tubing looks on the pickup shoes.

i am not sure how much you will be able to see, my digitial camera is not great with closeups

Mike-
Pretty clean work on the shring tubing. Thanks for all of the tips. I wouldn't mind seeing some pics of the sleeving process for armature holes.
Jim

Actually thats someone else who has played with sleeving, I simply havent found the right sized brass tubing to make sleeves. What I do is to replace the stock axles (about 0.0595) with a larger size axles (1/16, about 0.0625). Usually the new axles fits very well, occasionally one of the axle holes is a tad small. I have a 0.063 reamer to open up the hole. Sometimes I chuck one of the 0.0625 axles in a dremel and enlarge the hole that way (by letting the new axle spin in the axle holes for a minute or so).

You can see the larger axles on the bottom view picture. The lap times show a 6.88 second lap for the chassis in the pic. The 8.5 sec lap is for a JLTO that ran well out of the box, no tuning except oil and slip on silicones. The 7.9 lap was for a chassis that has restricted pick up shoes, matched magnets, oil and silicone tires. The 6.88 chassis had the axles replaced, front weights, matched magnets, balanced arm, o-ring fronts and low profile rears.

Mike- Thanks for all pics. This has been an extremely informative thread! The lap times really stress the point.

Jim

Mike, what's the width on that car? It looks enormously wide.

just a tad over 1 5/16, so it will not fit through a tech block (basically because i got sloppy cutting my own axles, and didnt bother to trim the axles to 1 5/16). since its just me on my home track, i was not too concerned about the chassis being "legal".

my track is routed, with plenty of lane spacing, so even "wide" cars can pass side by side.

Thanks for the pics MKING!