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Old 11-02-2009, 03:55 PM   #61
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Hi John,

What I'd like too know is how could i improve rear traction on my car???
when i turn it rotates around like Im doing a Hand brake turn.
is fine when you know its gonna do it but can be fairly unpredictable at times.

Rob.
You might reduce the rear droop and see if this helps. I had a similar problem on carpet and was transferring too much weight forward.
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Old 11-03-2009, 05:37 PM   #62
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Track Session 84 F air temp 104 F track temp.
This, I think, was the best session yet. The XXX-S handled beautifully on all parts of the layout. I got no spins in 3 packs. Cornering speed was improved for two reasons, more flex in the frame, and improved tire condition with a slightly less powerful motor (1/2 wind less). I Immediately had a good wear pattern on the tires. Punch is improved slightly out of the corners, mid straight speed is slightly less. I tapped a few flappers as the goal today was to run the tightest lines on the parts of the course that have been changed.
We had white stripes, rubber tapered curbing about 1 inch high (10 inch wide) and then flappers. The curbing was removed so the visual cue is identical but the car can now just skim the flapper and be completely inside the white line. I took some time to get used to this.

Here is a pic of the layout. The section on the far right has been changed on each flapper. I worked on this and the 4.0 motor helped to cut tight lines. Coming out of turn 4 to hard acceleration has been ticklish before. I had some rear end wiggle. There is some ripple in the pavement there. Nothing but smooth acceleration today. The far right hand end (in the pic after turn 6) of the track looks short but is really as long as most indoor tracks straights. It is 78 feet curb to curb. I use a lot of power there. The car had a tendency to spin late in the arc. None today. The better tire condition has really hooked up the car. Takeoff 36R tires with Traction Action. LRP 4.0 X12 geared 90/24. Motor temp 161F at 6 minutes. I tried 90/25 and had less grip, less punch out of the corners, and lower motor temp. It was not hooked up well with the higher gear.
First pic is looking from the far left side of this diagram.
Second pic is looking left from the drivers stand toward the right of this diagram.
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LOSI XXX-S, Tips and Tricks, Open Mod, etc-2b-mikes-gulf-coast-raceway-road-track.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-2010-ifmar-world-1-10-sedan-layout-mikes-006.jpg  
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Old 11-03-2009, 08:21 PM   #63
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Default Front spool?

I re-read the thread, it sounds like you are using a spool but I did not see that stated specifically. Just to be clear, you are recommending a spool for open outdoor asphalt tracks?

Not to create more work but at some point one of those LOSI setup sheets might make it easier for people to match your setup.

Thanks for your posts please keep up the good work.
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Old 11-03-2009, 09:43 PM   #64
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My setup is posted Here

imjohnah-thanks for the interest.
I am using a locked diff on this track. I added that to the setup. There are several hairpins which I believe are best run with some brakes. Most of the other guys eventually add the locked front diff as well.

I am getting very good results with the spool pulley for the JRXS. It does not seem to require constant tightening like the sandpaper disks and standard pulley. You should check the tightness before each session, though, as it is still plastic and will compress a little with constant pressure.
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Old 11-04-2009, 03:12 AM   #65
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Thanks guys-The low-low roll center blocks are installed. I had to make some mods up front. There is a lip on the edge of the frame that needs to be sanded off or it will limit down travel of the arm. The nub on the droop screw up front is completely removed. The droop tab must be narrowed so the bumper will go on and not restrict down travel of the arm. Some short droop screws need to be installed front and back. This is the same setup I used to run outdoors on the XXXS years ago.
Hi, cant see you mention droop setup anywhere, and are you here saying to cut off the tabs under the droop screws? how do you set droop and what do you run?

ps loving this stuff
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Old 11-04-2009, 05:16 AM   #66
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Default Long Wires

Hi John.
I think I read earlier in the thread that you believe long wires between the ESC and motor help keep things cool? How much have you noticed this? I would have thought the insulation would limit the ability of the wire to radiate heat.
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Old 11-04-2009, 06:30 AM   #67
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Hi John,

have you had any timed laps as yet?
If so how does your XXX-s compare too your old TC5 or too the times posted by other drivers etc on the same track?

Is the XXX-S competative with the other brand of cars etc?

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Old 11-04-2009, 07:29 AM   #68
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Hi, cant see you mention droop setup anywhere, and are you here saying to cut off the tabs under the droop screws? how do you set droop and what do you run?

ps loving this stuff
I've been told by the old school guys the tabs for the droop screws flex and result in droop not remaining consistent. To get around this we use internal spacers to get us in the ballpark and fine tune with the shock end. The reason this works follows: Droop screws limit the down travel of the arms (effect weight transfer front to rear also part of roll). When the droop screws are removed, the shocks limit the distance the arms can travel down, so changing the length of the shock can be used to adjust droop. Just my 2 cents. It took me a while to wrap my head around the concept of droop.
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Old 11-04-2009, 09:45 AM   #69
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Thanks for the posts all.

My droop is set so the springs don't get loose on full droop. This is what I usually do when there is only medium or less grip. I will add this to the setup.

Droop can be set with spacers between the shock piston and the bottom of the shock. I am not so sure that soft droop setting are bad. I like the fact that when the car rolls enough to contact a droop screw, it is a cushioned contact that won't disrupt traction. Crashes and time will change the droop settings, though. If this is the case internal shock spacers may be desired and that trick part about adjusting the shock rod end up and down on the shaft. Thanks C&B RC.

What droop does is make minor changes to the roll stiffness. As I take away droop the roll stiffness of that end increases. (Weight transfer is little affected by roll or pitch)

I had to modify the droop screw boss up front to get sufficient clearance but I did manage to get a small 3/16 inch droop screw in the modified piece and am able to adjust droop with it. At the back I only need to use a shorter allen screw. I might post a pic later today.

I have no lap times. The track has been changed so they would be irrelevent anyway. I am able to note how I do against other cars that are fast but not with the latest depowered setup. I may make a gain over the TC5.

The handling and cornering were exceptional yesterday, better than the TC5. Hopefully this will lead to a mistake free main.

I still don't know if I am on the correct belt. I am running black. I like the noise free braking, but I think it may be at the expense of some high speed friction. I will try the green sometime, but not this week. There is a 3 day race this weekend, I may participate.

Long wires-They do not provide a lot of cooling due to the insulation but they do keep the solder joints a little cooler. They also restrict amp draw a little which is helpful with a 3.5. We had some trouble with these 3.5s popping solder joints at 2-3 minutes. Even with 600F 2% silver solder. It helps to have good connectors (no banana plugs). There are some split cylindrical connectors that wedge in place, they seem to be OK also. Motor and speed control cooling with fans also helps. The wires provide some surface area to radiate heat and cool by convection from the air.

I have had no breakage while driving the car. On the first day a speed control failed at speed and the car drove itself straight into the boards. Broke one RTR c hub (caster block). I have tapped all manner of flappers and boards.
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Old 11-04-2009, 10:05 AM   #70
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John

I noticed on your setup you are runnnig 0* of castor... can you comment on that or offer some opinions on castor?

thanks!
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Old 11-04-2009, 10:15 AM   #71
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I normally like 4 degrees of caster. I saw no 4 degree caster blocks for sale for the XXX-S. On trying the car as is, I liked the increased turn in. The car steers harder right at the begining of the turn and starts the cornering. The car has little tendency to toss the rear out when it's doing this so it is a go.

I added two degrees caster with kickup session before last. There was no improvement to be noticed mid corner where caster should help cornering the most.

So for this car I like 0 caster. It drives great. On the TC5 and most of my cars, I have 4 degrees caster installed but maybe I should try 0 on the TC5.
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Old 11-04-2009, 01:04 PM   #72
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Originally Posted by John Stranahan View Post
I normally like 4 degrees of castor. I saw no 4 degree caster blocks for sale for the XXX-S. On trying the car as is, I liked the increased turn in. The car steers harder right at the begining of the turn and starts the cornering. The car has little tendency to toss the rear out when it's doing this so it is a go.

I added two degrees caster with kickup session before last. There was no improvement to be noticed mid corner where caster should help cornering the most.

So for this car I like 0 caster. It drives great. On the TC5 and most of my cars, I have 4 degrees caster installed but maybe I should try 0 on the TC5.
hi john just letting you know i recently found out that the castor blocks on the XXX-S are the same as the Jrx s and they come in 0,2,4,6,8 Degrees
hope this helps
Rob
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Old 11-04-2009, 06:20 PM   #73
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Rob-Thanks. It is nice to have a more recent car for crash parts. I may try a set of 4 degree blocks later on then.

Track Test, 81F air temp, 104F track temp.
Phil treated the track with a little sugar water today to tone down the dust. Traction was medium. A joy really. I was able to put that tooth back on the pinion and ran a 26\90. My speed on the straight was excellent. My motor temp went up 10 degrees showing that I was putting down the power. All I needed was that little bit more traction. I did some tire test. I put the RP36's that were reserved for racing duty on with Traction action. I got very good performance. The wear pattern is shown at bottom left. Notice the miniature tread that forms when the tire really hooks up. You can't see this well outside, but you can feel it as a roughness with your fingers. I also had some Sorex 36's mounted on the stock Losi wheels. These squealed the entire time and were scuffed smooth giving me slightly less bite.

I was able to run the car against some competition today. Ron brought a TC3 we had been having trouble tuning to the new track. It no doubt had the best speed on the straight with the very low friction driveline and a 3.5 motor. My XXX-s did well against it as well as a 4.5 equipped T2. I am happy again with the black belt. I put brand new Sorex 40R tires that are also reserved for race duty on for a quick test. The car and tires were just outstanding. Best results yet. Great punch, good cornering, excellent top speed.

Interestingly we made progress on the TC3 by removing the corner braces and then chopping away parts of the frame that helped to make it stiff. A T2 that is doing quite well is the fiberglass model chassis that is relatively limber as well.

I made a mistake on the chicane early in the straight at about 45 mph and hit the inside bumper loud and hard trying to pass Ron late in the straight. I broke both arms on the near side. I think any electric car would have broken. Easy fix. No other damage or misalignment.

The second pic is a top view of the mods that need to be made to install the low roll center kit. Basically you need to make room for the very low hinge pin. the bumper boss with the red tipped screw must be beveled. A little farther forward and to the left you can see the tab on the arm that the droop screw must bear on. It is very low on the car now. Most of the top of the boss for the droop screw must be removed and then the boss that remains must be narrowed.
I was able to tighten the plastic diff pulley 1/4 turn today.

The president of Serpent and the Serpent team were at hand late this afternoon inspecting the track for our Grand Prix race this weekend and then the eventual IFMAR worlds.
Attached Thumbnails
LOSI XXX-S, Tips and Tricks, Open Mod, etc-tread-pattern-takeoff-rp-36r-005.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-xxx-s-low-roll-center-mods-002.jpg  
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Old 11-04-2009, 08:47 PM   #74
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Losi XXX-S at 51.8 ounces. 1469g

Requirements of the car are slightly different with a 4.0 instead of 3.5 motor. I no longer worry about overheated solder connections. I can stand a little more punch. I removed a fistful of 12 gauge wire. I removed the battery strap and replaced it with tape like I use on the oval car. Weight is now down to a svelte 51.8 ounces or 1469 grams. Side to side balance is excellent. We have adopted weight limits from the International Indoor champs for rubber tires at 1425 g. I am reasonably close enough now that I can't use excessive weight as an excuse. I should even note an improvement tomorrow in the punch department. I soldered the fan leads to the Tekin solder tubes to tidy things up a little.
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Old 11-04-2009, 09:14 PM   #75
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Hey John

are you still running the xxxs rtr body?
If so I found them too be around 30 grams heavier than a protoform body
must be due too thicker plastic
I'd say a light weight protoform body would be even lighter again
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