5LikesLOSI XXX-S, Tips and Tricks, Open Mod, etc
05-25-2010, 01:30 PM
#301
Evoracer-Thanks for the report. No I have not tried that change to Ackerman.
I took my car and measured the steering angle of the two wheels. I used a dial Protractor and a setup board. I set the outside wheel to 10 degrees, I measured the inside wheel. I got 12 degrees 40 minutes for the inside wheel with my stock setup. Also I am using the forward holes in the steering arm. The links are almost perfectly at 90 degrees to the car when it is going straight.
I made your recommended change. Short part of the arms forward, moved pivots of the bellcranks to the forward hole in the G+ chassis. Now, the steering links have the very slightest angle going back as they go out. I suspect little difference on the track. The inner wheel angle is 12 degrees 10 minutes. That difference of only 30 minutes is probably within the error range. That is only .5 degrees. I will try it on the track next time out.
John
I took my car and measured the steering angle of the two wheels. I used a dial Protractor and a setup board. I set the outside wheel to 10 degrees, I measured the inside wheel. I got 12 degrees 40 minutes for the inside wheel with my stock setup. Also I am using the forward holes in the steering arm. The links are almost perfectly at 90 degrees to the car when it is going straight.
I made your recommended change. Short part of the arms forward, moved pivots of the bellcranks to the forward hole in the G+ chassis. Now, the steering links have the very slightest angle going back as they go out. I suspect little difference on the track. The inner wheel angle is 12 degrees 10 minutes. That difference of only 30 minutes is probably within the error range. That is only .5 degrees. I will try it on the track next time out.
John
05-25-2010, 05:29 PM
#302
Hey John, didn't necessarily mean it as a suggestion. Actually, I'm not totally sold on the idea. The mod was noted in the Todd Hodge article of a few years back.
On my car I have the alloy steering arms so there's only 1 hole for the turnbuckle connection. I could of course change this. What i originally saw as a benefit was the reduced turnbuckle angle. As it was before, with the bellcranks in rearward hole and long end forward, the steering links (turnbuckles) were angled forward from the servo. My laymans thinking presumed this was less than efficient. After the mod, link angle was straight as can be. It's now necessary to reduce endpoint adjustment substantially as full deflection causes the wheel to contact the lower shock mount. I assume the steering is now more efficient by removing the link angle and thats why I don't need all that servo travel. I did notice the bellcranks seem a little stiffer....maybe binding a tad.
BTW, at full deflection....but just short of contact with shock mount, I noticed that both wheels seem to be at the same angle. I no longer notice the ackerman angle of what would be the inside wheel. Obviously the reduced travel negates the ackerman we're all used to seeing when the X turns. Sooooo....is this SUPPOSED to be the result of this mod ?? And if so...is there a downside to having both wheels turn at the same angle ??
On my car I have the alloy steering arms so there's only 1 hole for the turnbuckle connection. I could of course change this. What i originally saw as a benefit was the reduced turnbuckle angle. As it was before, with the bellcranks in rearward hole and long end forward, the steering links (turnbuckles) were angled forward from the servo. My laymans thinking presumed this was less than efficient. After the mod, link angle was straight as can be. It's now necessary to reduce endpoint adjustment substantially as full deflection causes the wheel to contact the lower shock mount. I assume the steering is now more efficient by removing the link angle and thats why I don't need all that servo travel. I did notice the bellcranks seem a little stiffer....maybe binding a tad.
BTW, at full deflection....but just short of contact with shock mount, I noticed that both wheels seem to be at the same angle. I no longer notice the ackerman angle of what would be the inside wheel. Obviously the reduced travel negates the ackerman we're all used to seeing when the X turns. Sooooo....is this SUPPOSED to be the result of this mod ?? And if so...is there a downside to having both wheels turn at the same angle ??
05-25-2010, 06:14 PM
#303
From what I have read (and seen with some my own chassis) there is an early and late graphite chassis
from what I can gather the early chassis had the option to move the bellcranks, but from team drivers and losi testing it was found only one position was really needed so the deleted it on the later chassis
I've found limited info on this but I hav read about it in places - could just be rumours???
Maybe someone in the know ie: an ex team driver might fill us in??
from what I can gather the early chassis had the option to move the bellcranks, but from team drivers and losi testing it was found only one position was really needed so the deleted it on the later chassis
I've found limited info on this but I hav read about it in places - could just be rumours???
Maybe someone in the know ie: an ex team driver might fill us in??
05-25-2010, 06:25 PM
#304
Pretty sure it's the other way around Rob. Before the G+, the stiffezel chassis only had the single ackerman setting. The 1st Gen G+ (the one with TL milled aft of the motor) also had 1 hole. Then the later car came with 2 holes and different milling. And yes, it would be great to get a team driver to answer. Reminds me, I think Todd Hodge still gets on here. I'll do some checking.
05-25-2010, 06:50 PM
#305
new to the game
just bought a xxs this winter put on a mamba max pro 5700kv combo and wow i love it didnt think i would, still love my 8ight but this is funner than i thought it was going to be!
05-25-2010, 07:14 PM
#306
Thanks for the posts. Tiny Turbo-Welcome aboard.
Ackerman was an improvement to steering added later in history. If the front wheels are parallel when turning then you have no Ackerman and you have reduced performance.
No need to worry about the efficiency of the links moving the wheels. There is plenty of strength and efficiency. Having the steering links perfectly perpendicular to the chassis is not neccesarily the perfect Ackerman. Just a point of interest when I compared the two positions.
In my tests so far on the bench with steering arms that have two holes. The Ackerman is almost duplicated when using front chassis holes and reversed bellcranks when using the forward holes on the steering arm. Because the servo now acts on the longer arms of the bellcrank, steering will be slowed a bit. Servo travel will need to be increased. I doubt I will tell the difference on the track as the servo is plenty fast.
The only way to tell if one is Ackerman is better is to test it.
Ackerman will have an optimum angle. In my case the inner tire is turning at a 2 degree greater angle than the outside tire at a 10 degree outside wheel angle. This may be hard to pick up by eye but extremely important on the track to get both front tires at their optimum slip angle. This slip angle will be different for the inside and the outside tires due to the width of the car and the difference in loading of the two front tires when cornering.
Track test to come.
John
Ackerman was an improvement to steering added later in history. If the front wheels are parallel when turning then you have no Ackerman and you have reduced performance.
No need to worry about the efficiency of the links moving the wheels. There is plenty of strength and efficiency. Having the steering links perfectly perpendicular to the chassis is not neccesarily the perfect Ackerman. Just a point of interest when I compared the two positions.
In my tests so far on the bench with steering arms that have two holes. The Ackerman is almost duplicated when using front chassis holes and reversed bellcranks when using the forward holes on the steering arm. Because the servo now acts on the longer arms of the bellcrank, steering will be slowed a bit. Servo travel will need to be increased. I doubt I will tell the difference on the track as the servo is plenty fast.
The only way to tell if one is Ackerman is better is to test it.
Ackerman will have an optimum angle. In my case the inner tire is turning at a 2 degree greater angle than the outside tire at a 10 degree outside wheel angle. This may be hard to pick up by eye but extremely important on the track to get both front tires at their optimum slip angle. This slip angle will be different for the inside and the outside tires due to the width of the car and the difference in loading of the two front tires when cornering.
Track test to come.
John
06-26-2010, 06:55 PM
#307
Track Test 4.5 vs 3.5
This was a combined motor and tire test as the two interact at high power. A couple of guys have run 4.5s on our track and obtained good lap times with Sorex 36 tires even in 130F track temps we are having now. I usually run a 3.5 and Sorex 40s. So the question was could I improve with a 4.5 and 36's. Normal hot practice laps for me are low 20 s to 20.0 flat with Sorex 40's and a 3.5 motor. I was able to garner a few 19.6 s with sweep tires and the 3.5 but the sweep tires are not suited to or high speed track just yet. There may be a fix in the wings. Today I had good traction so it was a good day to test the 4.5. Here is the story of the first two packs. I would run a very good couple of laps at about lap 3. 19.7 on one, 19.6 on the second, but then lap times would increase for the rest of the pack. The tires were overheating. I was a tick slow on the straight ,but not by much, as the 4.5 was geared up sufficiently. There was a little less punch out of the corners, a little bit more rip on the middle of the short straights. The motor was easier on the tires than my 3.5 but a smoother hand than I was needed to keep them hooked up the whole pack. I tried Sorex 40's and the 4.5 and traction improved but lap times were about the same. I will race the 3.5 with Sorex 40's tomorrow.
John
This was a combined motor and tire test as the two interact at high power. A couple of guys have run 4.5s on our track and obtained good lap times with Sorex 36 tires even in 130F track temps we are having now. I usually run a 3.5 and Sorex 40s. So the question was could I improve with a 4.5 and 36's. Normal hot practice laps for me are low 20 s to 20.0 flat with Sorex 40's and a 3.5 motor. I was able to garner a few 19.6 s with sweep tires and the 3.5 but the sweep tires are not suited to or high speed track just yet. There may be a fix in the wings. Today I had good traction so it was a good day to test the 4.5. Here is the story of the first two packs. I would run a very good couple of laps at about lap 3. 19.7 on one, 19.6 on the second, but then lap times would increase for the rest of the pack. The tires were overheating. I was a tick slow on the straight ,but not by much, as the 4.5 was geared up sufficiently. There was a little less punch out of the corners, a little bit more rip on the middle of the short straights. The motor was easier on the tires than my 3.5 but a smoother hand than I was needed to keep them hooked up the whole pack. I tried Sorex 40's and the 4.5 and traction improved but lap times were about the same. I will race the 3.5 with Sorex 40's tomorrow.
John
07-02-2010, 07:17 AM
#310
Hey John, getting some chassis scrub and wondering what would be the best fix. It's confined to the outer portion of the chassis toward the rear. No significant rubbing in the middle so it appears to be roll related rather than bottoming out. Silver springs front,pink in back. Handling with 26mm treaded tires is really quite nice and the scrubbing isn't noticeable while on track. No chassis reaction or sound. Would you suggest :
1. ride height change?
2. Spring change?
3. anti roll bar added.
I lean toward the roll bars as I really like the way the car is handling. I'm trying to keep ride height around 5-6 and droop at 2-3 as per your article. It does seem very happy there. My plan is to mark the affected chassis area with a sharpie and run a single clean lap, then check for scrub.
1. ride height change?
2. Spring change?
3. anti roll bar added.
I lean toward the roll bars as I really like the way the car is handling. I'm trying to keep ride height around 5-6 and droop at 2-3 as per your article. It does seem very happy there. My plan is to mark the affected chassis area with a sharpie and run a single clean lap, then check for scrub.
07-02-2010, 09:09 AM
#311
I would first run at 6 mm, then I would add equal size sway bars front and back. The smaller the better to maintain cornering grip. If you have excess grip then use fatter sway bars. You did not mention any motor rubbing. That is where mine used to rub the track. I put a little bevel on the X12 motor after first rotating it to a good position to miss the screws.
John
John
11-13-2010, 03:20 PM
#315
About the chassis stiffzell stuff. You mentioned 4. The RTR, the original, the older graphite with the "L" logo then switched to the "X" logo. Well last year I was searching for a graphite chassis. No one had on except Stormer. I bought it. What is weird is I have never seen a solid graphite XXX-S chassis. At first I tought it was a XXX-4 but it's not. Here's a pic.
[IMG]
[/IMG]
[IMG]
[/IMG]
[IMG]
[/IMG][IMG]
[/IMG]