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Old 11-30-2009, 09:40 PM   #136
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pejota-a touch of kickup is the operative word. I did try both 2 and 4 degrees of kickup with no caster and then again with caster. On the corner that I wanted more corner exit acceleration the kickup failed to perform as the track is a bit bumpy there. Basically corner exit noise was increased. I do see the value of a little bit of kickup on a smooth tracks.
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Old 11-30-2009, 10:15 PM   #137
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OK ive read almost everything here lol But i am new to the road scene. im not sure what motor set-up ill be running yet but can anyone tell me where to start with this thing for EVERYTHING including springs, shock oil, caster, camber, ride height, droop, toe, etc, etc. any help would be great please PM the details or where i can find out more info.

Thanks Tony
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Old 11-30-2009, 11:14 PM   #138
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http://www.bfastrc.com/

team bfast diff products can be found here

I found them too be really smooth and last alot longer than the standard losi diff set up for myself (when ordering you will need to order the kit for the losi xxx4 they are the same as the xxxs diffs)

hope this helps

By the way that sounds like you got a good run out of those diffs (30 runs) in mod. most of the mod guy that i watch do diffs after every run and here they only run five min races none of these guy's run losi's tho

Rob
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Last edited by paraletic; 12-01-2009 at 02:27 AM. Reason: extra info
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Old 12-01-2009, 02:27 AM   #139
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For those that are curious too. Ther newer big lipo's fit in the xxxs with very little Dremeling. Just a couple tabs that the sub c's aligned in and thats it.

These are SMC 5200 40c's and also fitted a 50c.



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Old 12-01-2009, 09:37 AM   #140
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Thanks for the post guys. I will check out that diff link. The XXX-S will certainly hold the largest of LiPo 2s batteries. Nothing in the way vertically. Thanks for the pic. Look at all those red bits.

Paralectic-The Bfast products look good. That Losi thrust bearing has carbide balls, though. I don't know yet whether it is readily available, as the quantity available went to 0 after my order. I actually ordered 2 and received only one. It is often thought most of the roughness in a diff is located in the thrust bearing as it is undersized compared to the diff and has a very similar function and load while the diff is undergoing diff action.

Rebuilding the diff every heat was the Norm at the Gulf Coast race, for the other cars. in spite of that, many times, the rear diffs failed. I suspect they are not using enough tension and going for silky smooth. My car is setup to run well with a tighter diff needed for a 3.5 motor.

Tony- Here is my setup for outdoor asphalt in this thread. Go with stiffer springs and add swaybars for carpet.
LOSI XXX-S, Tips and Tricks, Open Mod, etc

Here is a related post on Setting Up a used XXX-S Car in this thread.
LOSI XXX-S, Tips and Tricks, Open Mod, etc

Additionally guys put links to team drivers setups early in the thread.
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Old 12-01-2009, 11:13 AM   #141
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More on weight reduction by PM
That bottom cover is an integral part of the center box tube frame. I have run without it, but the car did not handle predicatbly. Too much torsional stiffness was lost. (substitute for thin lexan).
I have a CRC black diamond speed control coming. This should put me at a good weight. Thanks for the tips. I like the shock towers in graphite but I never break this molded flexible one. I have resisted putting on the sway bars and have cut the little balls off in the past. I think I will make weight and be able to run medium bars when the speed control weight is reduced. I am close now.
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Old 12-01-2009, 11:32 AM   #142
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Default 13.5 gearing

Roughly,

What gear ratio do you recommend for
13.5 brushless on outdoor large open layout parking lot asphalt
Novak site list the following

13.5 turn 4.5 gear ratio recommended
118 48 = 4.50 [64 pitch]
108 44 = 4.49 [64 pitch]
90 36 = 4.58

3.5 turn 10.5 recommended
which would be 90/15 = 10.98 or 90/16 10.29

you reccomend a much higher gearing
90/22 which is 7.32 than Novak
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Old 12-01-2009, 12:39 PM   #143
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Imjonah- I can answer part of this on the 3.5 Our straight is in effect 240 feet long. Thats about 3 indoor track straights worth. My car is hitting near 60 mph. My gearing is part of a package. I have an internally fan cooled 3.5 with an auxilliary external fan. I have a fan cooled Tekin RX8 speed control, and the thunder power 40 C battery. Change any of the three and you can no longer attain this gearing and amp draw for six minutes. An older LRP TC edition would do it regularly for 5 minutes. A GTB has to be geared more conservatively to keep from thermalling. I would not put a 3.5 on it. Novak does have a new speed control recently released. I have lowered the gear only slightly to 21/88 to get better corner exit acceleration at the expense of some straight line speed.

Internal fan cooled rotors are now available installed from Speed Passion and now from Tekin with an optional rotor. If the "black diamond" speed control from CRC works out this will provide a lighter alternative for the future. Costs should come down.

Someone please help with 13.5 gearing.
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Old 12-01-2009, 01:25 PM   #144
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[QUOTE=John Stranahan;6663787]
I have a CRC black diamond speed control coming. QUOTE]

Wha?> Your putting a $400 ESc in a $100 TC?

Let us know how it runs!! Look foward to hearing that.
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Old 12-01-2009, 01:30 PM   #145
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it also depends on what speedy you are running as the new timing advance speedies require a different ratio too work propperly
Also some motors work diff than others an reguire a diff ratio some hav more low down torque an no rpm An others are made too rev so even tho two brand motors are the same number of winds they may react diff
it can come down too testing for ratio select a safe gearin then do a few laps to get feel of speed etc then temp motor n speedy an adjust gearing according that's what i do


Quote:
Originally Posted by imjonah View Post
Roughly,

What gear ratio do you recommend for
13.5 brushless on outdoor large open layout parking lot asphalt
Novak site list the following

13.5 turn 4.5 gear ratio recommended
118 48 = 4.50 [64 pitch]
108 44 = 4.49 [64 pitch]
90 36 = 4.58

3.5 turn 10.5 recommended
which would be 90/15 = 10.98 or 90/16 10.29

you reccomend a much higher gearing
90/22 which is 7.32 than Novak
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Losi XXX-CR....................Losi Mini Baja.....................Losi XX-4 W/E
ASSociated RC12L4
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Old 12-01-2009, 01:34 PM   #146
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Quote:
Originally Posted by imjonah View Post
Roughly,

What gear ratio do you recommend for
13.5 brushless on outdoor large open layout parking lot asphalt
Novak site list the following

13.5 turn 4.5 gear ratio recommended
118 48 = 4.50 [64 pitch]
108 44 = 4.49 [64 pitch]
90 36 = 4.58

3.5 turn 10.5 recommended
which would be 90/15 = 10.98 or 90/16 10.29

you reccomend a much higher gearing
90/22 which is 7.32 than Novak

I ran 4.12 FDR (108/48) on 150ft long track. with a Sphere TC

with a Tekin RS , 5.02 fdr 118/43
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Old 12-02-2009, 11:57 AM   #147
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The Losi XXX-S, as my vote for the best mod TC ever, certainly is worthy of the finest electronics. I am happy when they just don't catch fire and burn the car up.

Ackerman
With the change to the latest edition of the graphite chassis and graphite hubs, I now have some adjustments to Ackerman. In photo one you can see an extra ball stud mounted rear on the steering arm. You may be able to just see and extra set of mounting holes to move the inner steering link position forward by moving the bell cranks.

In photo two you can see a schematic of Ackerman. The car needs to steer the inside wheel at a tighter radius than the outside wheel. Ackerman accomplishes this. The basic Ackerman is built in to the angle at which the steering arms leave the kingpin. The basic Ackerman or perfect Ackerman is achieved by a steering link setup like on the TC3 where the steering links move at exactly right angles to the chassis.
By adjusting this steering link angle forward or backward we reduce Ackerman.

I measured the Ackerman on the Losi. See photo three. With steering links forward, I put the outside wheel in a turn at 20 degrees this time with an angle attachment on a standard combination square, previously with a Dial protractor shown in the photo. The inside wheel moved 27 degrees.

With the links on the rear most holes in the steering arm the steering links are now angled back. We lose some Ackerman. This time a 20 degree outside wheel angle produced a 25.5 Degree inside wheel angle. We lost 1.5 degrees of Ackerman.

Road test to come.

From what I understand on the Losi XXX-S original EA3 plastic "Stiffzell" model, team drivers were given prototypes with adjustable Ackerman. Each drive selected the same Ackerman which exist now in the plastic car and base setting of the Graphite car. Fortunately you guys are spared having to fool with this setting, but, if your car is the latest edition graphite models and is adjustable you might as well try one of the Ackerman settings for a short time.

moving the links back and bell cranks forward would give the maximum reduction in Ackerman.

I would like to tell you that I have made great gains adjusting Ackerman. But I have not. The stock setting is usually the best for me.
Attached Thumbnails
LOSI XXX-S, Tips and Tricks, Open Mod, etc-ackerman-001.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-schematic-ackerman.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-ackerman-measuring-b-s-dial-protractor-resized.jpg  
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Old 12-02-2009, 12:22 PM   #148
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Excuse my ignorance regarding Ackerman, but i've always had trouble understanding it...

The greater difference in degrees of Ackerman affects steering how?

In your example you reduced the difference in degrees by 1.5 degrees, what will that do?

And when people say increase or decrease Ackerman, do they mean increase or decrease the difference in degrees? Or do they mean increase or decrease the effect on steering?
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Old 12-02-2009, 05:54 PM   #149
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Pejota-
The wheel on the inside of the curve must follow a shorter race line and be steered to a smaller radius curve. The difference in the steering angle of the inside tire vs the outside tire is the Ackerman. I did not find a common way to express Ackerman values. When the difference in angle is greater, I will call it more Ackerman. When the difference in angle is less I will call it less Ackerman. Both the adjustments on my Losi will go to less Ackerman in two stages.

Ackerman Track Test 40F
Well it was quite a decision what tires to put on. The 36's were too soft at 66 F with the 3.5 motor geared 7.6 overall. I left on the 40's for this test. Certainly they were a bit hard for 3 laps, but then they settled in to low-medium traction. We had a hard rain the day before so I could expect this or slightly better. With the lessened Ackerman (rear hole on the two hole steering arm). I had less steering traction. My race line on the hairpins was going wide of the black groove. I added 5% more throw with the EPA setting. That may have been all the way to lock. I had just enough steering now to stay in the black but wider than my normal turn. The car was more stable as now it pushed a little more. Inner wheel chatter on the hairpins was eliminated. The chicane was handled well. All in all I thought I was slower than possible.

I put the links back forward on the steering arms. This reset Ackerman to full. I got my steering traction back. I could now hit my corner marks closely, Turn and stay in the middle of the black groove where there is the best traction, accelerate sooner out of the corner. I thought I was much faster this way. Ron, an experienced observer did not. Corner speed at the Apex was certainly higher with less steering, but I don't think it compensated for the large extra distance that needed to be covered in the turns.

Now I put on the 36's and the car was very well behaved. I probably could have run CS 32's.

So what to use Ackerman reduction for? Well any time you have too much steering traction. If traction roll is possible you can try it. If the car is feeling too grippy on carpet and losing too much momentum in the turns try it. There are other ways to attack this same problem so don't feel left out in an RTR car. These other methods include: adding a front sway bar, increasing front shock oil viscosity, decreasing shock piston hole size (all with standard front Ball diff). The Steering blocks or hubs of course can be purchased separately to make the RTR car adjustable in Ackerman.

Ackerman can be determined Geometrically. It goes something like this. You draw a line through the rear wheel centers extending to the inside of the corner. You can set the outside wheel to say 20 degrees steering angle and extend the line to meet the first line (on the inside of the corner). The proper angle for the inside wheel is when its line meets the other two. This might be considered the theoretical Ackerman, but because there is a slip angle between the tire and road and the outside tire bears much more weight from weight transfer and thus has a different slip angle, the theoretical Ackerman may not be the best.

I took measurements just to know and be able to tell exactly what is going on with the steering angles. Ackerman is not something you would normally measure.
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Old 12-03-2009, 11:19 AM   #150
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Think of Ackerman this way:

1. You know that your inside tire turns a tighter circle than your outer tire (just a smaller diameter circle)

2. This means that it needs MORE steering angle than the outside tire. This difference is Ackerman.

How does it affect?

Well, if you have LESS Ackerman, your inside tire will try to push the car OUT since it is steering a wider circle than it wants (picture it - less Ackerman means the inside tire is steering closer to the same as the outside, so a wider circle than it should). You will feel like you have to fight the car to get it to steer.

If you have MORE Ackerman, your inside tire will want to PULL the car IN since it is steering a tighter circle than the desired turn (again picture it - more Ackerman means the inside tire is steering a tighter turn than it should). You will have a very twitchy car.

Ackerman isn't really something to adjust - you want to find the angle whereby both tires can run the ideal diameter. It IS something to recognize, though.

I was handed a car, a while back, that felt unpredictable. Going perfectly straight, it was great. At high speed turns (where the outside was highly loaded and the inside was not) it was somewhat okay, but felt on a knife-edge. As it slowed down (inside got some load) it would GRAB like a MUTHA and I felt like I had to fight it. . . Turns out the steering rack had a ton of spacers on it and the Ackerman was way over. . . something like 3-4 degrees over what it should have been. . . fixed that and it was predictable again.
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