Tuning JLTOs



I thought I would share my recent experiences tuning a JLTO, from out of the box to a Fray style racer.



The track: 4x8 4 lane routed track with Magnatech braid instead of rail (Thundertrack).

Timing: diodes with Greg Braun’s software



The Car: JLTO chassis (grey, not the black R1 chassis). No body, pick up shoe glued in for testing.



Out of the box. Could not make a single lap without de-slotting. Rear axles holes particularly sloppy; lots of rear wheel hop.




Restricted pickup shoe travel with heat shrink tubing. Been using 5/64 tubing but recently switched to 1/16. The 5/64 size slips on and then must be heated to stay in place, the 1/16 can be forced onto the shoe, and stays in place without needing to be shrunk. Put o-rings on stock hubs, really lowering the front end (about 0.320). Best lap time: 8.3 seconds. Still hard to control.

oops! the heat shrink tubing is 1/16, not the 1/8 i first reported


Replaced stock rear tires with Weird Jack’s tuffy silicons (from a bag of rejects). Best lap time: 7.2 seconds. 15.3% improvement over Step #2.




Replace rear axle with a 1 5/16 wide drill rod axle; wire size 50 (that’s 0.070; a big step up from stock axles, which are about 0.062). I buy drill rod in various sizes, and cut axles with a cutoff disk and a dremel. I use whatever size I need to eliminate all slop. Usually that means I need to enlarge one or more of the rear axle holes. I do this by chucking the right size axle into another dremel (I have several dremels to avoid having to keep replacing bits) and running the axle into the axle holes. If the hole really needs to be opened up, I use some Simi chrome or rubbing compound. This is the hardest part of my tuning, as you want the axle to just fit. No slop, but no grab either. A good fitting axle will really reduce friction. It usually takes me about 10-15 minutes for this step, stopping frequently to avoid over boring the axle holes. 0.0625 axels (1/16 drill rod) will work with stock hubs (pressed on with a wheel press). If I use a larger axles, I either use different hubs, or I ream out the hole in the stock hub (I have had good luck using the axle chucked into the dremel; with the wheel holder removed from my wheel press, the JLTO hub fits in the opening in the wheel press, and I can use the wheel press to hold the hub while I ream it, letting me ream a reasonably straight hole). Then I use black max (rubberized superglue) to secure the hubs to the axle. Just a note, the replacement axle is smooth, and I usually have no trouble with the crown gear spinning. The replacement axles are larger than the stock axle, and the crown gear holds fine to the larger smooth axle (the stock axles have splines). I have screwed up a chassis enlarging the rear axle holes, but if I do I can usually just use the next larger size axle material. Then I use a wire brush (in another dremel of course!) to buff the gears, with the brushes and magnets removed, and the gear plate in place (with the gear clamp on, to keep the middle gear from shooting off to parts unknown). I am careful not to remove too much material from the plastic gears. Some people use Simi chrome for this step, I have found the wire brush works well, and is a lot less messy. After this step, the best lap time was 6.77 seconds, and the chassis was A LOT more predictable to drive. That’s a 22.5% improvement over Step 2, and a 6.35% improvement over Step 3 (diminishing returns!).




Added Fray style independent fronts (wider; 1 5/16 and weighted). I used home made fronts, you can buy them for $6-8. Mine cost about $2.25; 1/16 hollow brass tubing ($0.60 for 12 inches at hobby stores), standard flat head sewing pins ($1.50 per hundred at Walmart), stock chrome TJET hubs from

WOW! Thanks for the DETAILED report! I'm getting to like JLTOs (and AWTOs) more and more myself...

(oh, and I just got a Bag-o-Rejects from Weird Jack this week. Phenomenal deal on bulk tires...)

--rick

mking- Thanks for the detailed report. I never would have guessed that the axle slop was as large of a contributor to the performance. The stats really help lay out the advantages of each step.

Can you give a little more detail regarding the gear polishing with the wire dremel? Are you trying reduce weight on top, or get in the teeth and de - burr the gears? How do you do this evenly? Do the gears free spin as the dremel runs and is that how you keep the work uniform?

Jim

Jim

Hi

The purpose of using the wire brush on the gears is simply to de-burr the gears and get better mesh of the gear train.

with the wire brush running at low speed, i lightly press the wire brush against the crown gear (the one on the axle) without the gear plate in place. i do this for a few seconds, just long enough to get the rear axle spinning, and to lightly deburr the crown gear. if you watch, you can actually see the color of the crown gear changing.

then I move to the gear plate and repeat that on the small gear under the gear plate that engages the crown gear.

then i assemble the chassis (without magents and brushes)

then i lightly press the wire brush against the pinion gear. if you position the brush properly the gear train will spin. i spend more time on the pinion gear than i do the plastic gears. moving the wire brush around will cause the pinion gear to stop and reverse directions, smoothing out the gears in each direction.

then i move the wire brush to the interface between the pinion (brass) gear and the middle gear (idler). if you poistion the wire brush correctly the gear train will spin (once you get the hang of it, you can move the wire brush from one gear to the next without the gear train stopping). again, if you watch the idler gear you can see a color change as you deburr the gear. i am careful not to go overboard on the plastic gears. then i move to the interface between the idler gear and the last gear on the top of the gearplate, again being careful not to be overly agreesinve on the plastic gears.

before i start i oil under the pinion gear, so oil moves into the bore in the gearplate for the armature, letting the armature and pinion spin freely.

without the magnets and brushes in, you can get a really good idea how much or little friction there is in the gear train.

mike

Posted by mking:

then i lightly press the wire brush against the pinion gear. if you position the brush properly the gear train will spin. i spend more time on the pinion gear than i do the plastic gears. moving the wire brush around will cause the pinion gear to stop and reverse directions, smoothing out the gears in each direction.

That's how I break in my cars before running, Mike. I use a 9V battery to run a chassis for around 10 minutes, then I turn the battery around to reverse the polarity, and run the chassis for another 10 minutes. After that break-in period, along with the neccessary tweaks, TO's run nice.

Would a fibre wheel work,Dremel has a fibre wheel that looks almost identical to their wire wheel.
I don't run these cars,but would or could a fibre wheel do the same thing with-out being quite as aggresive

hi

i dont think a fiber wheel woulld be very effecvtive. you need to remove some material to deburr the gears and enhance gear mesh. i may be overstating the danger of removing too much material from the plastic gears using a wire wheel/wire brush, as it hasnt happened to me yet. i just think its possible and i watch out for it

mike

Mike - Thanks for the added detail on deburring. I had been sanding the gears but never got into the teeth of them. I am anxious to give this a try!

Thanks

Jim

i agree a well tuned JLTO is alot of fun

have you ever replaced a JLTO axle? if not, send me your address and i will send you a few axles in various sizes

mike

Thanks for the offer, Mike. I only replaced axles that were bent, and I use another JLTO or an Aurora TO axle to replace it.

hi dlw

i urge you to try a larger axle. i actually like the JLTO axles (never found a bent one); what i dont like is the JLTO axle bores. there is too much slop, leading to some wobble/wheel hop. it sounds like you can replace an axle just fine, let me send you some slightly larger axles (i bought way tooooo much axle material; it was cheap and i had to pay fixed shipping so i figured i would buy extra). a JLTO with no rear axle wobble is very smooth running. the wobble i am talking about can be seen underneath the chassis. grap both rear wheels, and wiggle the rear wheels side to side. on most JLTO, you get wobble, because at least one of the axle bores is way too big. swithcing axles can eliminate the wobble

mike

Cool, thanks Mike.

You refer to axle bores. Do you mean the holes the axle goes through, or the knurled ends of an axle where the rims are pressed onto?

by axle bores i am refererring to the holes in the chassis the axle passes through.

the front holes are fine, but the rear holes are often too large for the axles, so the axles kind of flop around

Thanks for the info mike...
Have you ever tried axle bushings on a JLTO?
Scott

hi scott

i never found any material suitable for bushings. i supposed brass tubing would work, but never actually worked out what size i would need.

i saw you post on the fray board. are you going in 2007?

mike

hi scott

i saw you post on the fray board. are you going in 2007?

mike

Not me...
Those guys are much too serious about racing... :lol:
(Not that there is anything wrong with that...)

Scott

Where do you buy the drillblanks and what size to start with? Thanks

hi

id go for 1/16 (0.0625) and wire size 52 (0.0635) to start with.

drill rod is not really all that hard (it is metal stock in rod form that is used to make drill bits. the drill bits/drill rod are VERY hard b/c it is heat treated, but drill rod has not yet been heat treated. after heat treating drill rod is called a drill blank). but for a slot car axle, unless your in a magnet car class, drill rod is fine.

it cuts easy with a dremel and cut off disk. it is often sold in 3 foot lengths.

i have found that i need to drill out the bores of the stock hubs to make sure they do not split when you mount them on a thicker axle (in fact, i found about 20% of stock JLTO hubs were already splitting on the STOCK axle, i wonder if AW hubs are better).

http://www.wthutch.com/catalog/

on page 8, note 1/16 x 36" blanks (Annealed M2 Blanks) are $5.74. thats enough for 19 or more axles.

on page 10, note the air hardening drill rod, 1/16 x 36", is only $1.32! whiles its not particulalrly hard, its plenty strong enough for a Tjet axle.

on page 11, wire size 52 x 36" rod is $1.29 wire size 52 is about 0.063, a tad bigger than 1/16. you may want to experiment with wire sizes 51 and 53, but i found wire size 51 a bit too big.

Since shipping is going be $6-8 anyway, buy several of the cheaper 36 inch rods.


you can also buy "piano wire" in 1/16 size from most hobby shops. i think the piano wire bends a bit easier than drill rod, and it is also not as polished.

hi

id go for 1/16 (0.0625) and wire size 52 (0.0635) to start with.


http://www.wthutch.com/catalog/

on page 8, note 1/16 x 36" blanks (Annealed M2 Blanks) are $5.74. thats enough for 19 or more axles.

on page 10, note the air hardening drill rod, 1/16 x 36", is only $1.32! whiles its not particulalrly hard, its plenty strong enough for a Tjet axle.

on page 11, wire size 52 x 36" rod is $1.29 wire size 52 is about 0.063, a tad bigger than 1/16. you may want to experiment with wire sizes 51 and 53, but i found wire size 51 a bit too big.



A couple questions.
It appears from the above description that drill rods are strong enough for T-Jets and AFX/X-Traction. Is there really any need to spend the extra money for drill blanks?
What is the difference between air hardening drill rods (page 10) and oil harding drill rods (page 11)?

Thanks...Joe

hi

sorry for any confusion, i share a computer and didnt realize my original post was under tiaragam

anyway, i have used both the oil hardened and air hardened drill rod and cant tell any difference

and for a Tjet axle/JLTO axle, i think the drill rod is plenty hard, and see no real benefit to paying more for drill blanks. i have not yet bent a drill rod axle, and havent gotten any feedback from fun-jet users that their rear axles have bent.

i know i have made plenty of wall shots w/o a bent drill rod axle yet. could happen, just hasnt happened yet :)

Thanks Mike...this is all good stuff.

Joe