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Old 05-05-2010, 07:58 AM   #286
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Originally Posted by John Stranahan View Post
Droop
I have been happily running 2 mm of droop front and back without checking it much. Easiest way to check is measure the ride height. Lift the chassis corner until the wheel is about to lift. Measure the ride height. The difference is the droop. I reduced droop to 1.5 in the back. Here is what happened on the track. The car became a little more responsive but slightly loose. It skidded more easily. The worst that happened was on brakes coming into the hairpins. The whole car now shuddered. This was visible on the bottom sides of the car which developed huge ripples. I suspect the rear tires were now leaving the ground and hitting the top of ripples in the asphalt which happen to be located in the braking area. Anyway, I plan to go back to 2 mm where the car was happier.
I used to have a problem like that when the Schumacher Mi2 first came out and we still raced on slippy floor with minispikes. I could barely get near 2mm of rear droop on a droop guage and the rear of the car was always loose and it was a pig to drive, yet backing off the shock ball end a couple of turns and I could get it down to 1mm rear droop and the car was dynamite. Despite all of the setup books saying its just for controlling weight transfer to the front, in this case it did help with side grip as well when the car was rotating. I'm sure you can find a fancier way of explaining it John Since then I've always been a fan of using droop to setup the car, such a small change but it makes a bigger difference than alot of other items.
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Old 05-12-2010, 08:49 PM   #287
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Conrad-Thanks for the post.

Just in is my new X12 17.5 stock motor. I read the recommended overall ratio is 4.0 so maybe my work with the big pinion is already needed. That puts me in the 40-41 tooth range. I am prepared with smaller spurs as the track is short.

Here is a little video clip of a couple of my competitors running mod TC on the big outdoor track at Mikes-HobbyShop.com which is my primary track.

I took some HD video of Frank and Johnny sparring. There were two lead changes. Pretty exciting 3 laps. 58 seconds of video, 90 Mbytes. Now with the HD quality comes a time penalty dowloading or buffering the film. It can be played right to your HD TV if your computer is so equipped. The quality is about 10 times what is typical of RC videos. The zoom is tight, both cars are visible, after a lap or so you will get the feeling of the track, then you can play it over. The doubled frame rate keeps the cars visible on the straight and sweeper even though they are reaching 60 mph at the end of the straight. My computer plays it fine with windows media player. My wifes computer needed an upgrade of Quicktime for windows to play the HD video.

It only took 8 minutes to buffer on my computer before the video played.

www.Stranahan-rc.com/ElectricModTC.MOV


Pics, Robert Leading Frank around the hairpin right by the drivers stand
Johnny going tight around the sweeper.
Paquito really making the g's in the hairpin one lane from the drivers stand. Is that a front tire in the air or not.
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Old 05-13-2010, 05:16 AM   #288
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Hi John
giving stock class -17.5turn a go now are you? Or just doing some testing?

Be good to hear your ideas for what u do with the xxxs in this class - if anything is to be done differently to mod etc?

Which speedy will you be running with the x12 ?
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Old 05-13-2010, 10:22 AM   #289
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Paraletic-We had an invite for some 1/10 stock TC racing at another track in Houston. The class may or may not make. First pratice session is tonight. I am surprized at the gear reccomendation from LRP at 4.0. I read through you guys stock trhead and saw gears in the 5.0 range overall. I am caught short of gears in the 4.0-5.0 range. It is also interesting LRP reccomends no tinkering with the avanced turbo boost timing as features built into the X12 motor accomplish the same.
I plan to use the LRP SPX8 as it is installed in the car and will be used on the weekends. If I get complaints I have a GTB on my dyno I can use.
It is a no turbo boost track at the moment (not that I have any available).
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Old 05-13-2010, 10:36 AM   #290
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Hey John, welcome to the ....lighter side. I see you're still using 48p gears ? I can see where your mod would be necessary. On our smallish track we tend to gear in the upper 4's to 5.0 range with 17.5 non boost, non timing. On my X thats a 106t 64p spur and a 41t 64p pinion to give 4.7 fdr.
I'll be using yours and Paraletic's setups for this weekends racing. Really hoping to see a change. Much to much oversteer in recent times.
Could use your input regarding shock oil. I was thinking of trying 35w. As you know the stock xxxs setup uses 30w. We're on a untreated concrete, smooth surface (natural concrete with no major dips or rough sections). Technical designs usually with only 1 main straight of approx. 80ft. VTA using 25.5. As I said, I'm using most of your basic setup advice. MF low blocks back/front, OR back/front (per paraletic but will change if needed), ball diff in front/back, 4 castor and 2.5 toe in rear. I've changed to the xxxs shocks instead of the JRXS shocks. shock position all the way in (to start).Wheelbase forward in front. Out back is middle plus a small shim at rear to take out slop (will change to full forward if needed). Rear camber link is on inside hole on hub. Hub mounted to outer hole on A arm. Front diff tight,rear diff looser.
Thought I'd give you as much info as possible. Thanks

Last edited by Evoracer; 05-13-2010 at 11:31 AM.
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Old 05-13-2010, 08:34 PM   #291
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Evo-thanks for the post. Setup looks good. I use 35 weight oil but I bevel the top of the piston holes a little to ease the uptravel. 30 weight is good without doing so. What you want is your car to be planted over the bumps instead of skipping over the tops of the bumps. You will have more forward traction this way.


Track Test, Stock, small circuit
We had our first session on the small track with stock motors. They had a a problem with the sugar application. The weather was very damp almost condensing. The sugar never dried. Grip would be good for a while and then the tires would load up with sugar. The main competition today was 1/12 scale sedans, a few 1/18th sedans and a 1/12 pan car. I just happened to be hooked up better than the lighter cars. I probably made 100 passes tonight. The car handled well, I had good control and could pass without contact.
The second and third time out, I changed to the sweep exp 36. After a cleaning the second time out with the sweeps, I actually had pretty good traction. The car was scraping away about 1/3 of the sugar from the tires width in the corners. I was lapping cars about every four laps or so. I could run almost forever. I ended up with a gear of 5.12 overall. It seemed to reach top speed in 10-12 feet, but this is what this small layout needed. Motor temp 109F
Maybe more 1/10's will show next time.
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Old 05-14-2010, 08:38 AM   #292
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Originally Posted by Evoracer View Post
... MF low blocks back/front, OR back/front (per paraletic but will change if needed), ball diff in front/back, 4 castor and 2.5 toe in rear. I've changed to the xxxs shocks instead of the JRXS shocks. shock position all the way in (to start).Wheelbase forward in front. Out back is middle plus a small shim at rear to take out slop (will change to full forward if needed). Rear camber link is on inside hole on hub. Hub mounted to outer hole on A arm. Front diff tight,rear diff looser....
Evo, what springs are springs are you running with the above setup?
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Old 05-14-2010, 09:57 AM   #293
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Thanks John, we'll see how she goes on Sunday.
Erik, I posted on the stock thread before coming to this one. I see you're running almost identical setup. Trying Blue springs all 4 corners to start and before I change them I'll look at pivot block changes, wheelbase, and shock position. Those are the ones that vary between John's suggestions and Paraletic's. All depends on what I see over the first few laps. Tires are new so I'll give her a few laps to stretch her legs and scrub the tires in.
Just a note, I mentioned I got hold of a MF motor mount. I've set the motor slightly higher than could be done with the stock mount. I was getting some scraping on the outer part of the motor. Glad I found it.
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Old 05-14-2010, 11:07 AM   #294
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Just so you know, losi also made atleast 2 different motor mounting discs
one allows the motor to sit low on the chassis (still easily avail new) and the other sits the motor slightly higher - I have two like this

looking at the discs I can't see why, with a vice and a good small needle file and dremel aswell you couldn't slot the standard disc and allow you to move the motor higher

I mite look at doing this next week to a spare motor disc I have, just to try
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Old 05-14-2010, 11:34 AM   #295
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Originally Posted by paraletic View Post
Just so you know, losi also made atleast 2 different motor mounting discs
one allows the motor to sit low on the chassis (still easily avail new) and the other sits the motor slightly higher - I have two like this

looking at the discs I can't see why, with a vice and a good small needle file and dremel aswell you couldn't slot the standard disc and allow you to move the motor higher

I mite look at doing this next week to a spare motor disc I have, just to try
Rob, this has been mentioned before but I've never actually seen the 2 distinct mounts aside from the stock one and this MF one. Can you post a pic on the stock thread sometime ? Maybe you already have and if so, send me a link. I do have 2 stock mounts which are definitely a different color (1 silver and 1 more of a bronze or goldish ). I thought they might end up different when I first saw them but turns out they're the same. And yes, doing the mod to a stock one would be pretty straightforward. Nice that I don't need to though.
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Old 05-16-2010, 02:37 AM   #296
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here is a pic of the mounts side by side
LOSI XXX-S, Tips and Tricks, Open Mod, etc-photo1.jpg
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Old 05-24-2010, 09:44 AM   #297
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Re-Mounts-I prefer to remove metal from the motor can rather than raise the entire motor up for clearance. On the LRP, select motor mounting holes so a section of the can between the screws that secure the end bells onto the motor is down. Now bevel the motor to match the chassis bottom which is angled for roll clearance. See the fourth pic. Note this was done before I new to select better motor mounting holes to get the long motor screws out of the way.

X-ray challenge

We had another big Nitro race sponsored by X-ray at Mikes-HobbyShop.com home of the 2010 Nitro Sedan Worlds which will be held in July. It included a 13.5 super stock electric class and a mod electric class, both with a JACO blue control tire. We new from the previous experience that the tire was inadequate for mod with track temps in the 140 F range. All of our cars handled horribly. All had huge amounts of off throttle oversteer. If you look at the pics of the tire you will see the classic signs of a tire that is too soft. Mainly you will note if you look close, tiny almost spherical rubber marbles spread across the tread. The white particles are dirt and sand that was accumulated through a short trip in the pits after the race. You can see the rubber marbles accumulated on the purple tape across the battery end that is securing the balancing wires. The tread is also worn smooth across. There is just a hint of a good wear pattern near the edge of the rear tire in the third photo. Ripples lined up with the circumference.

So what to do. Well one of the reliable tuning method when running a locked diff is add more rear toe. I was using 2.5 degree. From a previous car on this track, I found that about 2.75 degree per side is the upper limit. At 3.0 degrees the car is getting lose again. In other words there seems to be an optimum rear toe that when exceeded causes reduced traction to the rear end in cornering. I elongated the holes in the rear pivot block toward the outside. I put in two strips of .010 metal shim on the inside of the hole. I drove in a 1/8 inch shaft with a small hammer to form the shim. I reinstalled and measured toe with an Integy camber gauge. I was right at 2.75 degree. The car was remarkably improved but not cured. Nobody's car was really cured as the tire was coming apart. Our laps were 1.4 seconds slower than typical with what should have been awesome traction. I had complained about the tire selection well before the race, but nothing was done. Next time I will complain more vigorously. There is no need to detune the mod class this way. It was very frustrating for all the mod drivers. One even went home (and one refused to sign up) it was so bad, after shelling out the big bucks for the race.

Results
Qualifying was a bit on the rough side. Some new drivers were fighting for position even though my car was several seconds ahead of theirs on individual clocks. I would get the inside by their mistake and they would smash me into the boards on corner exit. I got second in each qualifier won the third, qualified 2 cnd overall and finished second in the uneventful main. I was effectively tied for fast lap in the first qualifier only .003 seconds back. Not bad for an old fart with an old design chassis.

Prerace check
Oiled both motor bearings.
Checked outdrives for wear, all OK.
Checked diff for smoothness and tension. Hold left front and left rear wheel still (locked diff) try to turn right rear wheel. It should not slip easy.
Check belt tension (OK, black belt)
check each out drive axle pivot pin holes for wear. Replaced right front steel drive axle. Holes were very elongated.
check each outer hub bearing for brinnelling. Replaced 3 bearings. I had serviced the fourth recently. Sorry you have to take them out to check with a pencil.
Check screws holding the caster blocks onto the hub. all OK. I use loctite sparingly on these screws to lock the screw to the inside of the little flanged bushings in the caster blocks. This works really well.

No breakage in the race. Finished all four qualifiers and main with no issues except the tires sucked.
john
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LOSI XXX-S, Tips and Tricks, Open Mod, etc-x-ray-challenge-2010-crew.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-jaco-blues-after-race-001.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-jaco-blues-after-race-002.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-losi-xxx-s-motor-mod-002.jpg  
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Last edited by John Stranahan; 05-24-2010 at 04:48 PM.
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Old 05-24-2010, 02:13 PM   #298
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That begs the question then, what would have been a good tire? I've see that type of wear here in Florida in RCGT. The HPI X-Patterns on Florida asphalt throw off rubber like it's their job.
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Old 05-24-2010, 04:26 PM   #299
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Sorex R40 or Takeoff RP 40. Jayco does list an Orange tire which is harder, but I found none for sale. Sorex R36s were 1.0 seconds faster in one racers quick test.
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Old 05-24-2010, 05:53 PM   #300
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John, have to re-visit an old subject...Ackerman. Recently made HUGE strides by changing setups using some of your suggestions. 1 that wasn't yours was moving the steering arms to the forward position and "flipping' them(shorter part forward) to adjust the ackerman dictated by the forward arm position and the use of rear pivot mounts in the front of the car. Have you tried this ??
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