Associated Factory Team TC5, Brushless, LiPo, Li-ion Nanophosphate, Tips and Tricks
08-20-2007, 06:29 PM
#106
Jon-You are welcome
First track Test
93F air temp 136 F track temp Traction medium to poor. Some dust
Gearing 10.87:1 or 87/16. LRP Sphere Comp TC edition. LRP X11 3.5.
I put a few laps on the TC5. I measured the speed on our straight with Radar and it was 48 mph. This is quite satisfying and is 3 mph faster than the last TC I ran on the track with a 10 x 1 brushed motor. After 10 laps the motor temp was already 167 F so I may have to gear it a little slower. I'll bring a timer to run it 5.5 minutes on the next session so I will know a little better if it will make the 5 minute mark without a themal shutdown.
Reading the Tire
When you run rubber tires on asphalt you can get a lot of information by looking at the tire tread after a run or even after just a few laps. If it is smooth but has little rubber marbles sprinkled over the surface it is a little too soff. If it has a torn ledge near the center where it looks like the tread has been ripped out it is too soft. Smooth with marbles was the condition of my tires today. Traction was just fair. I had RP30's on the car because it had rained and was cooler Saturday morning. I had RP 40's in the bag which I intended to run today, but forgot to install. If the tire is just right it develops tiny ripples lined up with the circumference. Traction is super. You can feel these ripples as you run your thumb accross the tread. You can see them especially well just after you wet the tire with traction compound. If the tire is too hard it will scuff smooth and there will be no marbles apparent. The car will slide around too much.
In the pic you can see the ripples on the inner and outer portion of the tire. You can see a smooth scuffed section from the middle toward the outside. I had good traction so this was an OK wear pattern.
First track Test
93F air temp 136 F track temp Traction medium to poor. Some dust
Gearing 10.87:1 or 87/16. LRP Sphere Comp TC edition. LRP X11 3.5.
I put a few laps on the TC5. I measured the speed on our straight with Radar and it was 48 mph. This is quite satisfying and is 3 mph faster than the last TC I ran on the track with a 10 x 1 brushed motor. After 10 laps the motor temp was already 167 F so I may have to gear it a little slower. I'll bring a timer to run it 5.5 minutes on the next session so I will know a little better if it will make the 5 minute mark without a themal shutdown.
Reading the Tire
When you run rubber tires on asphalt you can get a lot of information by looking at the tire tread after a run or even after just a few laps. If it is smooth but has little rubber marbles sprinkled over the surface it is a little too soff. If it has a torn ledge near the center where it looks like the tread has been ripped out it is too soft. Smooth with marbles was the condition of my tires today. Traction was just fair. I had RP30's on the car because it had rained and was cooler Saturday morning. I had RP 40's in the bag which I intended to run today, but forgot to install. If the tire is just right it develops tiny ripples lined up with the circumference. Traction is super. You can feel these ripples as you run your thumb accross the tread. You can see them especially well just after you wet the tire with traction compound. If the tire is too hard it will scuff smooth and there will be no marbles apparent. The car will slide around too much.
In the pic you can see the ripples on the inner and outer portion of the tire. You can see a smooth scuffed section from the middle toward the outside. I had good traction so this was an OK wear pattern.
Last edited by John Stranahan; 08-23-2007 at 06:42 AM.
08-20-2007, 06:41 PM
#107
Hera are a couple other issues that I tuned on.
Rear end was loose.
Roll Stiffness Change
I am running a ball diff. This makes the tuning straight forward. You cannot prevent the lateral weight transfer, but you can apportion a little more of it to the front to kill some traction up there. You do this by increasing the roll stiffness of the front or decreasing the roll stiffness at the rear. When the car rolls in the corner, the stiffer end will take a set first. More of the lateral weight transfer will happen on the stiffer end and it will do so faster. This will kill some traction there. You can increase stiffness with heavier springs, adding a sway bar, or raising the roll center. Heavy shock oil will increase the stiffness early in the corner.
I made the rear end less stiff by moving the top shock mount one hole inward.
Droop Adjustment
The tires were not sliding smoothly. They would stick then slip in tiny steps. (note that this was mostly from using too soft of a tire). I made a correction to my droop to taughten the car up a little bit. I removed a full turn of droop from the front end and 1/2 turn from the rear end. This turned out to be a little too much. The car was sliding well now but a little too much so.
The car is a real rocket in light weigth trim. I still felt like the driveline had very high friction. The belts are properly tensioned but they are very stiff. You would squeeze the trigger gently and the car would sit and then finally spring into very fast acceleration when the motor overcame the fricition. Hopefully it will break in a little.
My high speed cornering also had the rear end a little loose. I plan to raise the rear wing to correct this.
I had one collision to the side. This popped the upper camber link and spilled the dogbone. Neither the A-arm nor caster block nor outdrive broke. That's nice. I'll see if that was an abberation. This did horribly brinnel a set of bearings. I don't know which one. Usually its the outer wheel bearing. The front end rachets now.
Rear end was loose.
Roll Stiffness Change
I am running a ball diff. This makes the tuning straight forward. You cannot prevent the lateral weight transfer, but you can apportion a little more of it to the front to kill some traction up there. You do this by increasing the roll stiffness of the front or decreasing the roll stiffness at the rear. When the car rolls in the corner, the stiffer end will take a set first. More of the lateral weight transfer will happen on the stiffer end and it will do so faster. This will kill some traction there. You can increase stiffness with heavier springs, adding a sway bar, or raising the roll center. Heavy shock oil will increase the stiffness early in the corner.
I made the rear end less stiff by moving the top shock mount one hole inward.
Droop Adjustment
The tires were not sliding smoothly. They would stick then slip in tiny steps. (note that this was mostly from using too soft of a tire). I made a correction to my droop to taughten the car up a little bit. I removed a full turn of droop from the front end and 1/2 turn from the rear end. This turned out to be a little too much. The car was sliding well now but a little too much so.
The car is a real rocket in light weigth trim. I still felt like the driveline had very high friction. The belts are properly tensioned but they are very stiff. You would squeeze the trigger gently and the car would sit and then finally spring into very fast acceleration when the motor overcame the fricition. Hopefully it will break in a little.
My high speed cornering also had the rear end a little loose. I plan to raise the rear wing to correct this.
I had one collision to the side. This popped the upper camber link and spilled the dogbone. Neither the A-arm nor caster block nor outdrive broke. That's nice. I'll see if that was an abberation. This did horribly brinnel a set of bearings. I don't know which one. Usually its the outer wheel bearing. The front end rachets now.
Last edited by John Stranahan; 08-20-2007 at 06:53 PM.
08-22-2007, 06:18 PM
#108
Track Test Track temp 126-130F
I put a couple more runs on the TC5. A couple of the guys from the shop got a few laps in with it. I tapped the boards 4 or 5 times. There were no breakages. I believe this is because the arms are made of a little softer material than previous and also those vertical inner A-arm supports, that I talked about previously, give a little in a side crash. We all noted I still had a little too much steering on the car. I did not have a spring chart at hand and the calipers helped little in the range I needed as the springs have different number of coils. Photo one is a spring chart that came with a new set of springs. I inceased the front spring from a blue 17 lb to a gold 19 lb. I will be better armed next session.
No Themalling Yet LRP Sphere TC edition
I was able to give the car a full 5.5 minute test. Motor temp was 178F Speed control was only at 140 F, probably a little hotter internally. It did not thermal. The track was 10 degrees cooler than Monday though. Things are looking good in this regard. At most I can gear down by adding a few teeth to the spur. Note that I am on the ragged edge at the motor with the car 7 ounces light.
Takeoff RP 40's
I ran the hard tires for this hot session this time. Grip was good. I need slightly more roll stiffness for a good match to the tires. The gold front spring should give me this. After 3 runs I put some traction compound on the tire just to inspect the wear pattern. I had my nice tiny ripples lined up with the circumference that I pictured previously in this thread. More tightly spaced than the photo, very even accross the whole width. I could not ask for a better tire for the condition. I ran the tires dry but have in my pit box, Paragon Traction Action which works well with rubber tires if you need a little more grip.
Some issues
If you ease up on the throttle the TC5 car slows way too fast. In some respects this is typical touring car behaviour. You overcome this by not coming off the throttle so far. On some layouts I never even go to neutral for the whole lap. Most of the belt cars I have driven you are back on the throttle a little to enter the corner and keep the speed up. The TC3 gear drive car is one of the few cars where you can coast almost to mid corner before you are back on the throttle.
Crush Spacer Shim Availability?
One of the problems that cause a tight driveline is insufficient length to the crush spacer that separates the wheel bearings. On the old Losi or Associated cars, I would add an extra MIP axle shim just inside of the outside wheel bearing. This adds a little length to the crush spacer and a month or two down the road you are not adding an axial load to these wheel bearings when you tighten the wheel nut.
This new TC5 has an oversized metric sized axle shouder. The MIP axle shims no longer fit in there. If you know of some 6 mm ID thin shims that fit please let me know. I bought a set of Associated shims for the TC5; it did not contain a suitable size.
LRP sintered arm Question
I noticed that LRP has an sintered rotor for sale as an option. What I don't know is if the X11 motors come with this option. By spinning the arm in the car it feels like they do. The magnetism is very strong. By looking at the arm it is hard to tell if it is sintered or not. It looks like neither the Novak epoxy based arm nor the Novak sintered arm.
The second spring rate chart is tiny, you can print it, cut it out, and put it in your pit box.
John
I put a couple more runs on the TC5. A couple of the guys from the shop got a few laps in with it. I tapped the boards 4 or 5 times. There were no breakages. I believe this is because the arms are made of a little softer material than previous and also those vertical inner A-arm supports, that I talked about previously, give a little in a side crash. We all noted I still had a little too much steering on the car. I did not have a spring chart at hand and the calipers helped little in the range I needed as the springs have different number of coils. Photo one is a spring chart that came with a new set of springs. I inceased the front spring from a blue 17 lb to a gold 19 lb. I will be better armed next session.
No Themalling Yet LRP Sphere TC edition
I was able to give the car a full 5.5 minute test. Motor temp was 178F Speed control was only at 140 F, probably a little hotter internally. It did not thermal. The track was 10 degrees cooler than Monday though. Things are looking good in this regard. At most I can gear down by adding a few teeth to the spur. Note that I am on the ragged edge at the motor with the car 7 ounces light.
Takeoff RP 40's
I ran the hard tires for this hot session this time. Grip was good. I need slightly more roll stiffness for a good match to the tires. The gold front spring should give me this. After 3 runs I put some traction compound on the tire just to inspect the wear pattern. I had my nice tiny ripples lined up with the circumference that I pictured previously in this thread. More tightly spaced than the photo, very even accross the whole width. I could not ask for a better tire for the condition. I ran the tires dry but have in my pit box, Paragon Traction Action which works well with rubber tires if you need a little more grip.
Some issues
If you ease up on the throttle the TC5 car slows way too fast. In some respects this is typical touring car behaviour. You overcome this by not coming off the throttle so far. On some layouts I never even go to neutral for the whole lap. Most of the belt cars I have driven you are back on the throttle a little to enter the corner and keep the speed up. The TC3 gear drive car is one of the few cars where you can coast almost to mid corner before you are back on the throttle.
Crush Spacer Shim Availability?
One of the problems that cause a tight driveline is insufficient length to the crush spacer that separates the wheel bearings. On the old Losi or Associated cars, I would add an extra MIP axle shim just inside of the outside wheel bearing. This adds a little length to the crush spacer and a month or two down the road you are not adding an axial load to these wheel bearings when you tighten the wheel nut.
This new TC5 has an oversized metric sized axle shouder. The MIP axle shims no longer fit in there. If you know of some 6 mm ID thin shims that fit please let me know. I bought a set of Associated shims for the TC5; it did not contain a suitable size.
LRP sintered arm Question
I noticed that LRP has an sintered rotor for sale as an option. What I don't know is if the X11 motors come with this option. By spinning the arm in the car it feels like they do. The magnetism is very strong. By looking at the arm it is hard to tell if it is sintered or not. It looks like neither the Novak epoxy based arm nor the Novak sintered arm.
The second spring rate chart is tiny, you can print it, cut it out, and put it in your pit box.
John
Last edited by John Stranahan; 08-22-2007 at 09:03 PM.
08-22-2007, 08:44 PM
#109
Drive Line Inspection OK
I inspected the front end for my racheting noise. Turned out it was in the diff somewhere and not at the wheels. I took it out, inspected the diff rings. They were fine, no little divots. I put it back together and the racheting was gone, so the problem was probably in the little thrust bearing and it corrected itself.
I took the pinion off to inspect the driveline further. This is the best way as the motor can mask your feel of the driveline. It was fine. Belts and pulleys all turn easy.
Now the motor does not turn easy like a normal brushless, it turns more like a brushed due to high magnetism and having a full size rotor that is very near the stack. This gives it more natural braking which is what we felt on the track. You avoid this when neccesary by using some throttle. Some guys actually give touring cars some forward throttle trim. I don't care for that much and will use neutral occasionally to bring the back end around when I overshoot a corner entrance just a bit. Phil noted the car would oversteer off-throttle. The solution really is not to be off throttle, unless you want oversteer. You can brake going into a hairpin, if you like, but you should do so while the car is going straight. Then get back on throttle to do the corner. Not huge throttle, just enough throttle.
I looked in the LRP instruction sheets for default setting of drag brake which might be just a bit high for the touring car. My grayed out areas indicating default settings are not visible like a copy of a copy of a copy might be. I might go through the setup routine and note what it is set at later. I will also tinker with that internal temperature readout the LRP is supposed to have.
John
I inspected the front end for my racheting noise. Turned out it was in the diff somewhere and not at the wheels. I took it out, inspected the diff rings. They were fine, no little divots. I put it back together and the racheting was gone, so the problem was probably in the little thrust bearing and it corrected itself.
I took the pinion off to inspect the driveline further. This is the best way as the motor can mask your feel of the driveline. It was fine. Belts and pulleys all turn easy.
Now the motor does not turn easy like a normal brushless, it turns more like a brushed due to high magnetism and having a full size rotor that is very near the stack. This gives it more natural braking which is what we felt on the track. You avoid this when neccesary by using some throttle. Some guys actually give touring cars some forward throttle trim. I don't care for that much and will use neutral occasionally to bring the back end around when I overshoot a corner entrance just a bit. Phil noted the car would oversteer off-throttle. The solution really is not to be off throttle, unless you want oversteer. You can brake going into a hairpin, if you like, but you should do so while the car is going straight. Then get back on throttle to do the corner. Not huge throttle, just enough throttle.
I looked in the LRP instruction sheets for default setting of drag brake which might be just a bit high for the touring car. My grayed out areas indicating default settings are not visible like a copy of a copy of a copy might be. I might go through the setup routine and note what it is set at later. I will also tinker with that internal temperature readout the LRP is supposed to have.
John
08-22-2007, 08:46 PM
#110
John, the list is on the web somewhere (and I think in the papers that come with the TCSpec+X11 combo). I'm pretty sure it says that all the lower wind motors are sintered, and higher wind motors are bonded. The 4.5t is definitely sintered, and 13.5 is definitely bonded - that's all I know for certain.
-Adam
-Adam
08-22-2007, 08:53 PM
#111
Adamge-Thanks. I see the specs now. They were stuck between the cardstock of the motor package. It is sintered. That's a relief as it is about $50 for just the sintered rotor. These should hold up better to the 180 degree heat. It is also a large diameter sintered rotor from my internal inspection of the motor. This should lead to more efficiency and torque for the TC. I notice that little chart suggest 8.9 gearing for TC long track. I am at 10.8 and 180 F. I have a fat sintered rotor coming for my Novak 3.5.
John
John
Last edited by John Stranahan; 08-22-2007 at 09:09 PM.
08-23-2007, 01:30 AM
#112
08-23-2007, 02:05 AM
#113
Tech Adept
[QUOTE=John Stranahan;3607079The solution really is not to be off throttle, unless you want oversteer. You can brake going into a hairpin, if you like, but you should do so while the car is going straight. Then get back on throttle to do the corner. Not huge throttle, just enough throttle.
I looked in the LRP instruction sheets for default setting of drag brake which might be just a bit high for the touring car. My grayed out areas indicating default settings are not visible like a copy of a copy of a copy might be. I might go through the setup routine and note what it is set at later. I will also tinker with that internal temperature readout the LRP is supposed to have.
John[/QUOTE]
For what it's worth: my experiences with the LRP brushless. Keep in mind: this is with the Sphere Competition 2007 Spec though, with the Sphere TC edition, the settings will probably be different.
First of all, I love sintered. (And 50$ is way more than ppl pay in Europe) Braking is back, and so is grunt.
I felt that around neutral, the system is too smooth for me. The initial millimeter I push the throttle stick forward doesn't do much for moving the car. It turns the motor when free, but it doesn't move the car. Solution: "Throttle punch" setting of 20% on my KO radio. This is kind of like adjusting "DeadBand" on older Novak brushed ESCs. Now I have better control in slow corners.
Braking needs some work. Again, it's too smooth/weak initially, but 100% brake is hella strong. So I put initial brake on 3 (default is 0 or 1), and reduced EPA on the TX to 70 - 85%. Feels almost identical to brushed now; the entire range of brake that's left is usable.
With the stock settings, the first 2mm of stick movement wouldn't slow my car down, and from 50% on, it's lock up the rear wheels.
I like drag brake, so mine is set to 3. You probably want 0, pan cars are kinda sensitive to that.
Fiddle with the settings, you'll be pleasantly surprised!
I looked in the LRP instruction sheets for default setting of drag brake which might be just a bit high for the touring car. My grayed out areas indicating default settings are not visible like a copy of a copy of a copy might be. I might go through the setup routine and note what it is set at later. I will also tinker with that internal temperature readout the LRP is supposed to have.
John[/QUOTE]
For what it's worth: my experiences with the LRP brushless. Keep in mind: this is with the Sphere Competition 2007 Spec though, with the Sphere TC edition, the settings will probably be different.
First of all, I love sintered. (And 50$ is way more than ppl pay in Europe) Braking is back, and so is grunt.
I felt that around neutral, the system is too smooth for me. The initial millimeter I push the throttle stick forward doesn't do much for moving the car. It turns the motor when free, but it doesn't move the car. Solution: "Throttle punch" setting of 20% on my KO radio. This is kind of like adjusting "DeadBand" on older Novak brushed ESCs. Now I have better control in slow corners.
Braking needs some work. Again, it's too smooth/weak initially, but 100% brake is hella strong. So I put initial brake on 3 (default is 0 or 1), and reduced EPA on the TX to 70 - 85%. Feels almost identical to brushed now; the entire range of brake that's left is usable.
With the stock settings, the first 2mm of stick movement wouldn't slow my car down, and from 50% on, it's lock up the rear wheels.
I like drag brake, so mine is set to 3. You probably want 0, pan cars are kinda sensitive to that.
Fiddle with the settings, you'll be pleasantly surprised!
08-23-2007, 06:33 AM
#114
sydewynder-Thanks. Those 6 mm HPI shims should be perfect. Thickness is about .008 inch. That should be perfect as well. They will allow me to tighten my wheels down very well without putting a load on the wheel bearings.
Elvo-Thanks for the post. I will play with the settings. It looks like a more aggressive power profile is warranted for the touring car. I'll add a couple of points there. I have the same problem that initial throttle does not move the car. I have not used much brake yet as the car is slowing very fast in neutral. I will check the initial brake setting and make sure it is enough and also the drag brake or automatic brake setting. I'll give a report next session. I will likely be using brakes on my two tight hairpins in the Touring Car (like I do with the pan).
John
Elvo-Thanks for the post. I will play with the settings. It looks like a more aggressive power profile is warranted for the touring car. I'll add a couple of points there. I have the same problem that initial throttle does not move the car. I have not used much brake yet as the car is slowing very fast in neutral. I will check the initial brake setting and make sure it is enough and also the drag brake or automatic brake setting. I'll give a report next session. I will likely be using brakes on my two tight hairpins in the Touring Car (like I do with the pan).
John
08-23-2007, 07:04 AM
#115
Here's the TC Spec manual with default settings visible.
http://www.lrp-electronic.de/e/downl...ad.asp?id=1337
http://www.lrp-electronic.de/e/downl...ad.asp?id=1337
08-23-2007, 07:23 PM
#116
Adam-Thanks. I made a nice copy from that link. It does look like I should go 3 points more aggressive on the motor and use maybe a touch less drag brake as the natural braking of this particular motor is quite high.
Damping Rate
One question you have in setting up a touring car is evaluating how much damping you put on it. There are probably several schools of thought one of which is always stiff as hell. Here is a little test that we performed today that I though was instructive in this regard so Here it is even though the subjects are full size.
In one corner Tony's Arrest me Red Porsche 944. This is a two seat 2 L naturally aspirated sports car which is very low to the ground; rear wheel drive. Springing is not too taught, but adjustable Coil over shocks are set fairly stiff. Street tires of fairly generous dimension for the size of the car.
In the second corner My Stealth Black 2005 Fort Focus ST. This is a 4 seat touring car with 2 L dual over head cam four valve per cylinder engine; front wheel drive. The drag race we performed is no contest, the Focus wins. The autocross is no contest the Porsche wins. I am working on that.
Mark, A generous friend gave me his G-tech Unit. This is a cell phone sized unit that contains several accelerometers to monitor car performance. It is sophisticated enough to give accurate quarter mile times within a couple feet of true distance using just the accelerometers inside. We only measured cornering power or G's which I talked about previously.
We found two, what I will call, long sweeper turns. One was a little wavy, one was almost flat. We ran both cars several times on each turn, the first wavy turn in the afternoon then the second smooth turn 10 miles away more toward evening.
After practicing awhile and gathering data with the Black Focus, we then changed the instrument into the other car, but I ran in tandem with me following so I can give you an impression of both cars.
On the left is the output of the G-tech unit that you can plug into your computer later. The graph in the middle vertically is the graph of interest. The others are entertaining as well so I included them. On this graph the Black Focus is always the Black line and the Red Porsche is the Red line. When the g's build in a Right Hand turn the lines go above center. The Maximum scale of the graph is .9 g's. When the line approaches .9 we were at or near maximum cornering power for a glorious 10 seconds or so. (no other cars in sight, two full lanes for safety areas). Then the lines drop down on corner exit. You can see on this first graph that the red line is a bit wavy. The reason was the road was wavy we were thrown left then right a bit as the tires gained grip on the top of the humps and then lost grip as they unloaded in the depressions. I could see tonys car heave up and down and the rear also heaved left and right a bit (I was at least 3 feet behind). Also notice that the fourth hump was the tallest, he had a slight oversteer right there and then needed to slow a bit to correct it before we exited the corner. Also notice the little black line comes back to center a bit sooner. The Focus has actually exited the corner sooner in time and had a slightly higher peak G cornering force (.92 g's) early in the corner vs the .84 the Porshce obtained late in the corner. These graphs obviously were not obtained at the same time as we have but one instrument. They are the best that we produced. I could stay right on Tony's ass though when he was taking measurements.
We tweaked on tonys car a bit. We went up from 33 to about 36 psi in the front. I suggested he would do better if he did not have to worry about oversteer (which is a very dramatic scene sometimes at the autocross). This is like us moving the front shock one hole out at top to make the front roll stiffness a little stiffer. You can drive a little harder in the corner without this worry. We talked about going down from full stiff on the shocks, but the next corner was known to be smooth and high grip so we did not.
The graph on the right is the smooth corner. You can see the Porsche red line is coming to 0 sooner after the corner. The Porsche is exiting the corner a bit sooner. The red graph has a higher peak and a higher average than before and is also smoother. He actually pulled 1 G on the return corner. This is great with long wearing street tires. (We have the semi race rubber in the garage for another test maybe). I could no longer hold a few feet from his back bumper for the whole corner although I did not go as close in to start with as it made the lead car a little nervous.
Ok. So the moral of the story is too adjust damping to suit the conditions of the track. Making it too stiff is going to hurt you in a bumpy corner by causig that wavy cornering power condition.
When you are cornering you also want to keep that g curve up near your cars limit for as much of the turn as possible. It helps to drive smooth as each sharp movement of the wheel is likely to result in a dip in the curve.
If your RC car is heaving up and down on a bumpy turn chances are you are a little on the stiff side with your shocks. Smooth high traction surfaces like stiff, though.
I drove Marks Subaru WRX STI on this same corner but with all season tires. It pulled .89 g's. Really steady and easy to corner full out with due to the fourwheel drive. Ferocious corner exit traction.
John
Damping Rate
One question you have in setting up a touring car is evaluating how much damping you put on it. There are probably several schools of thought one of which is always stiff as hell. Here is a little test that we performed today that I though was instructive in this regard so Here it is even though the subjects are full size.
In one corner Tony's Arrest me Red Porsche 944. This is a two seat 2 L naturally aspirated sports car which is very low to the ground; rear wheel drive. Springing is not too taught, but adjustable Coil over shocks are set fairly stiff. Street tires of fairly generous dimension for the size of the car.
In the second corner My Stealth Black 2005 Fort Focus ST. This is a 4 seat touring car with 2 L dual over head cam four valve per cylinder engine; front wheel drive. The drag race we performed is no contest, the Focus wins. The autocross is no contest the Porsche wins. I am working on that.
Mark, A generous friend gave me his G-tech Unit. This is a cell phone sized unit that contains several accelerometers to monitor car performance. It is sophisticated enough to give accurate quarter mile times within a couple feet of true distance using just the accelerometers inside. We only measured cornering power or G's which I talked about previously.
We found two, what I will call, long sweeper turns. One was a little wavy, one was almost flat. We ran both cars several times on each turn, the first wavy turn in the afternoon then the second smooth turn 10 miles away more toward evening.
After practicing awhile and gathering data with the Black Focus, we then changed the instrument into the other car, but I ran in tandem with me following so I can give you an impression of both cars.
On the left is the output of the G-tech unit that you can plug into your computer later. The graph in the middle vertically is the graph of interest. The others are entertaining as well so I included them. On this graph the Black Focus is always the Black line and the Red Porsche is the Red line. When the g's build in a Right Hand turn the lines go above center. The Maximum scale of the graph is .9 g's. When the line approaches .9 we were at or near maximum cornering power for a glorious 10 seconds or so. (no other cars in sight, two full lanes for safety areas). Then the lines drop down on corner exit. You can see on this first graph that the red line is a bit wavy. The reason was the road was wavy we were thrown left then right a bit as the tires gained grip on the top of the humps and then lost grip as they unloaded in the depressions. I could see tonys car heave up and down and the rear also heaved left and right a bit (I was at least 3 feet behind). Also notice that the fourth hump was the tallest, he had a slight oversteer right there and then needed to slow a bit to correct it before we exited the corner. Also notice the little black line comes back to center a bit sooner. The Focus has actually exited the corner sooner in time and had a slightly higher peak G cornering force (.92 g's) early in the corner vs the .84 the Porshce obtained late in the corner. These graphs obviously were not obtained at the same time as we have but one instrument. They are the best that we produced. I could stay right on Tony's ass though when he was taking measurements.
We tweaked on tonys car a bit. We went up from 33 to about 36 psi in the front. I suggested he would do better if he did not have to worry about oversteer (which is a very dramatic scene sometimes at the autocross). This is like us moving the front shock one hole out at top to make the front roll stiffness a little stiffer. You can drive a little harder in the corner without this worry. We talked about going down from full stiff on the shocks, but the next corner was known to be smooth and high grip so we did not.
The graph on the right is the smooth corner. You can see the Porsche red line is coming to 0 sooner after the corner. The Porsche is exiting the corner a bit sooner. The red graph has a higher peak and a higher average than before and is also smoother. He actually pulled 1 G on the return corner. This is great with long wearing street tires. (We have the semi race rubber in the garage for another test maybe). I could no longer hold a few feet from his back bumper for the whole corner although I did not go as close in to start with as it made the lead car a little nervous.
Ok. So the moral of the story is too adjust damping to suit the conditions of the track. Making it too stiff is going to hurt you in a bumpy corner by causig that wavy cornering power condition.
When you are cornering you also want to keep that g curve up near your cars limit for as much of the turn as possible. It helps to drive smooth as each sharp movement of the wheel is likely to result in a dip in the curve.
If your RC car is heaving up and down on a bumpy turn chances are you are a little on the stiff side with your shocks. Smooth high traction surfaces like stiff, though.
I drove Marks Subaru WRX STI on this same corner but with all season tires. It pulled .89 g's. Really steady and easy to corner full out with due to the fourwheel drive. Ferocious corner exit traction.
John
Last edited by John Stranahan; 08-25-2007 at 06:50 PM.
08-23-2007, 07:45 PM
#117
talk about overthinking EVERYTHING...
08-23-2007, 08:44 PM
#119
I would rather overthink than not think enough...Also, in most anything, its the guys that push the limits of our knowledge that excel. Look at the pros in racing, they not only can drive well, but know what affects what, or at least should
So John, you havent talked too much about driving the TC5, but it does seem that it its a great vehicle, especially if one does not want to drop the dough on an xray.
Oh John, about the 6mm ID shims, I bought some for my Losi 8: Team Losi Shim Set, Metric 5mm/6mm
[LOSA6356]
Darned things were hard to find.
So John, you havent talked too much about driving the TC5, but it does seem that it its a great vehicle, especially if one does not want to drop the dough on an xray.
Oh John, about the 6mm ID shims, I bought some for my Losi 8: Team Losi Shim Set, Metric 5mm/6mm
[LOSA6356]
Darned things were hard to find.
08-23-2007, 10:16 PM
#120
not trying to be hostile....just givn you a little $hit cuz I get a headache reading all these longggggggg posts....keep up the good work