Losi Constant Velocity Drive (LCD) vs MIP CVD
01-07-2006, 11:19 AM
#91
Battery Discharge Curves Scorpion LiPo vs GP 3700
I had a chance to run a discharge curve for the GP3700 at 20 Amperes. I plotted this discharge curve along with that of the Scorpion LiPo. The attached photo shows that the discharge curve for the two batteries are very similar. In spite of this, the LiPo had a little more punch (probably in the 50 amps region) for 4-5 laps in a previous test. Then the two batterries (when a huge 7 ounce ballast was added to the LiPo) felt about the same.
Both of these curves will be higher and longer if a higher capacity battery of each type is tested and may be improved by incremental improvements in the battery types. I think the next battery on my list to buy would be a high capacity NiMH, IB 3800 or 4200.
Both of these curves will be higher and longer if a higher capacity battery of each type is tested and may be improved by incremental improvements in the battery types. I think the next battery on my list to buy would be a high capacity NiMH, IB 3800 or 4200.
Last edited by John Stranahan; 01-09-2006 at 04:42 PM.
01-08-2006, 12:25 PM
#92
Spektrum Final Install with Capacitor
I put the capacitor long ways on the chassis to have enough room. Note how I route antennas. Drill a little hole in the tube with the Xacto. Ream the hole a little with your .050 allen driver. Then thread antenna in through this hole. On some cars this prevents the antenna from peeking out under the chassis through the stupid hole and getting scraped off clean (Cut). This procedure keeps the antenna a little farther from the other wires. I mount the tube with a tie wrap to the front shock tower on this car with the Spektrum.
There are four faults with the early Spektrum that can be found at SpektrumRC.com
1. Glitch from poorly routed antenna inside the case. There is a photo.
2. Poor response indoors, Send early models back for a reprogram.
3. Shutdown on low voltage. The capacitor should cure this. Mine is a Novak, still waiting for the Spektrum model (same specs)
4. Poor steering trim. Send early models back for a reprogram.
There are four faults with the early Spektrum that can be found at SpektrumRC.com
1. Glitch from poorly routed antenna inside the case. There is a photo.
2. Poor response indoors, Send early models back for a reprogram.
3. Shutdown on low voltage. The capacitor should cure this. Mine is a Novak, still waiting for the Spektrum model (same specs)
4. Poor steering trim. Send early models back for a reprogram.
Last edited by John Stranahan; 01-21-2006 at 06:10 PM.
01-09-2006, 04:22 PM
#93
Losi JRXS, Novak GTB 6.5 Roadtest
I went to Mikes-HobbyShop.com track just North of Houston in Porter Texas for the maiden run on the JRXS and the GTB 6.5. Here are a couple of pics of the track. Track temp 24 C. CS 32's for mod practice. Citrus Oil traction compound.
GTB 6.5
GEARING
The manual recommends a gearing range for rubber tired touring cars between 7.75 - 8.5. I started at 7.32 because of the large size of the track. The motor was a bit too punchy even though I had geared higher than recommended. Too much acceleration out of the corners. It is hard to drive smooth this way in the corners. Then 7.00. Felt better, smoother. Motor temp 175F on the bottom 155 F on top. This is on the high side of OK, 160 F is recommended. I changed the spur and used 90/23 x 1.83 = 7.16. The car felt great. There was another fellow running a 10/2 brushed motor in a XXXS. He was running pretty good. We did not run together but I watched his car quite a bit. My car, at 7.16 , accelerated a little better, his had a little better speed on the end of the straight. I think with the same driver mine would have a slightly better lap time. I’ll run my own 11/2 after a while and give you a more direct comparison. I have racing fever now.
DRAG BRAKE
I set the speed control on profile 1 which gave me 20% dragbrake. If you have run stock motors, you have a natural built in drag brake with them. The laydown brushes shorts the poles to itself 2% of the time, so if the stock motor is turning on coast it is giving you substantial brakes when you go to neutral or ease off the throttle by generating current. The first thing you notice when you stick in a mod is that the car rolls forever and has somehow lost a lot of its steering on coast. There is no shorting due to standup brushes or brushless. Drag brake corrects this by adding a little braking action in neutral. M&M in Houston is a track with fairly generous width to the lanes, not too big a layout. I seldom go through neutral or use brakes. Mikes Hobby Shop track is a big high speed outdoor track with fairly good traction. The car is going really fast at the end of each straight section. It helps you steer around the corner to go to neutral and have some gentle drag brake slow you down and add weight transfer to the front. I eventually went to profile four which gave 40 % drag brake as well as 40 % initial regular brakes for emergencies when I overshot a corner. This means the brakes start at 40 % in neutral and then increase to 100% on trigger full forward. I set the radios end point adjustment on brakes to 75% to eliminate some wheel hop on full brakes.
LOSI JRXS
I started with the book setup but with much weaker front springs and low roll centers and locked front diff. I made the front springs the same as the back. I had some initial difficulties as expected. There were two bumps that I had not even noticed on the track running my well setup, but well worn, TC3. One was in the middle of the straight. The Losi was going almost airborne. Note that it was also going twice as fast here as I am running mod now. I made two changes to correct this. I made sure I had full uptravel to the suspension. I had a couple of the wheels slightly limited. I raised the ride height to 6.5 mm from 6 mm. I was also getting a tick, tick, tick, going around the two hairpins. The XXXS guy was too. My chassis edges were rubbing the ground a little. They have a nice bevel now. The Novak cleared the ground. The higher ride height, which I needed anyway, eliminated this. On the TC3 I had a similar problem with bumps at ReflexRC indoors. I put a .010 inch wide bevel on the top of the shock pistons holes by hand. This makes the uptravel of the shocks easier and leaves the down travel the same. This works much better through bumps as well as on full size cars. I plan to make this mod to the Losi JRXS. You just turn a 1/8 inch drill bit by hand and enlarge the very top of the hole at the angle of the bits tip. I don’t have too much traction here so I don’t plan to increase the roll stiffness at this point by going to stiffer springs or adding anti roll bars. Anyway after the adjustments, I was really pleased with the car. The belt driveline handles speed so much better than the gear driveline. A lot less noise and wear of the spur. More to come.
Breakage Report
When you get into a leaf or pile of leaves the car goes absolutely bananas. A couple of crashes resulted (I was too close to the boards). Broke the left side outdrive cup on the front. This is the easy one to replace. Broke an A-arm. LCD survived both times due to its short length I'm sure. The TC3 would have toasted aluminum bones twice here. For some reason the Losi servo horn stripped. Never had a new one strip before. Put on a slightly more flexible one.
Rear Camber link ball cup
My rear camber link ball cups are barely engaged in the threads when the inside stud is in the center hole and outside is on the outside hole of the upright. Put a truck ball cup on the outside end of both sides trimmed 1/8 inch short to solve this problem.
I went to Mikes-HobbyShop.com track just North of Houston in Porter Texas for the maiden run on the JRXS and the GTB 6.5. Here are a couple of pics of the track. Track temp 24 C. CS 32's for mod practice. Citrus Oil traction compound.
GTB 6.5
GEARING
The manual recommends a gearing range for rubber tired touring cars between 7.75 - 8.5. I started at 7.32 because of the large size of the track. The motor was a bit too punchy even though I had geared higher than recommended. Too much acceleration out of the corners. It is hard to drive smooth this way in the corners. Then 7.00. Felt better, smoother. Motor temp 175F on the bottom 155 F on top. This is on the high side of OK, 160 F is recommended. I changed the spur and used 90/23 x 1.83 = 7.16. The car felt great. There was another fellow running a 10/2 brushed motor in a XXXS. He was running pretty good. We did not run together but I watched his car quite a bit. My car, at 7.16 , accelerated a little better, his had a little better speed on the end of the straight. I think with the same driver mine would have a slightly better lap time. I’ll run my own 11/2 after a while and give you a more direct comparison. I have racing fever now.
DRAG BRAKE
I set the speed control on profile 1 which gave me 20% dragbrake. If you have run stock motors, you have a natural built in drag brake with them. The laydown brushes shorts the poles to itself 2% of the time, so if the stock motor is turning on coast it is giving you substantial brakes when you go to neutral or ease off the throttle by generating current. The first thing you notice when you stick in a mod is that the car rolls forever and has somehow lost a lot of its steering on coast. There is no shorting due to standup brushes or brushless. Drag brake corrects this by adding a little braking action in neutral. M&M in Houston is a track with fairly generous width to the lanes, not too big a layout. I seldom go through neutral or use brakes. Mikes Hobby Shop track is a big high speed outdoor track with fairly good traction. The car is going really fast at the end of each straight section. It helps you steer around the corner to go to neutral and have some gentle drag brake slow you down and add weight transfer to the front. I eventually went to profile four which gave 40 % drag brake as well as 40 % initial regular brakes for emergencies when I overshot a corner. This means the brakes start at 40 % in neutral and then increase to 100% on trigger full forward. I set the radios end point adjustment on brakes to 75% to eliminate some wheel hop on full brakes.
LOSI JRXS
I started with the book setup but with much weaker front springs and low roll centers and locked front diff. I made the front springs the same as the back. I had some initial difficulties as expected. There were two bumps that I had not even noticed on the track running my well setup, but well worn, TC3. One was in the middle of the straight. The Losi was going almost airborne. Note that it was also going twice as fast here as I am running mod now. I made two changes to correct this. I made sure I had full uptravel to the suspension. I had a couple of the wheels slightly limited. I raised the ride height to 6.5 mm from 6 mm. I was also getting a tick, tick, tick, going around the two hairpins. The XXXS guy was too. My chassis edges were rubbing the ground a little. They have a nice bevel now. The Novak cleared the ground. The higher ride height, which I needed anyway, eliminated this. On the TC3 I had a similar problem with bumps at ReflexRC indoors. I put a .010 inch wide bevel on the top of the shock pistons holes by hand. This makes the uptravel of the shocks easier and leaves the down travel the same. This works much better through bumps as well as on full size cars. I plan to make this mod to the Losi JRXS. You just turn a 1/8 inch drill bit by hand and enlarge the very top of the hole at the angle of the bits tip. I don’t have too much traction here so I don’t plan to increase the roll stiffness at this point by going to stiffer springs or adding anti roll bars. Anyway after the adjustments, I was really pleased with the car. The belt driveline handles speed so much better than the gear driveline. A lot less noise and wear of the spur. More to come.
Breakage Report
When you get into a leaf or pile of leaves the car goes absolutely bananas. A couple of crashes resulted (I was too close to the boards). Broke the left side outdrive cup on the front. This is the easy one to replace. Broke an A-arm. LCD survived both times due to its short length I'm sure. The TC3 would have toasted aluminum bones twice here. For some reason the Losi servo horn stripped. Never had a new one strip before. Put on a slightly more flexible one.
Rear Camber link ball cup
My rear camber link ball cups are barely engaged in the threads when the inside stud is in the center hole and outside is on the outside hole of the upright. Put a truck ball cup on the outside end of both sides trimmed 1/8 inch short to solve this problem.
Last edited by John Stranahan; 01-10-2006 at 09:59 PM. Reason: Corrected Initial Brake Description
01-10-2006, 06:42 AM
#94
Novak GTB Drag Brake Adjustment
Adjusting Drag Brake in Profile 4 on the GTB 6.5
This is something you do with the instructions in hand. I failed more than a few times, but may have succeeded with the following instructions.
The first trouble is reliably pushing the tiny set button which I can barely see as it is the same color as the switch body. I used the X-acto knife point. This gave me the best feel.
Turn on the radio and esc. Push and hold the set button until the blue and amber lights turn on solid. Let go. The lights will now flash the setting you are on. In my case for profile 4 they flash 8 times to indicate 40 % drag brake.
Now push the button one more time and WAIT FOR 9 FLASHES TO OCCUR. then hit the button one more time and wait for 10 flashes to occur. Now hold the button down for 1 second. Finished. I am now set to 50% drag brake. Chances are I will reduce this setting as I get better with this car motor and track.
This is something you do with the instructions in hand. I failed more than a few times, but may have succeeded with the following instructions.
The first trouble is reliably pushing the tiny set button which I can barely see as it is the same color as the switch body. I used the X-acto knife point. This gave me the best feel.
Turn on the radio and esc. Push and hold the set button until the blue and amber lights turn on solid. Let go. The lights will now flash the setting you are on. In my case for profile 4 they flash 8 times to indicate 40 % drag brake.
Now push the button one more time and WAIT FOR 9 FLASHES TO OCCUR. then hit the button one more time and wait for 10 flashes to occur. Now hold the button down for 1 second. Finished. I am now set to 50% drag brake. Chances are I will reduce this setting as I get better with this car motor and track.
01-11-2006, 04:11 PM
#95
Updated 2/20/2006
Losi JRXS Setup
Track Temp 12-15 C Takeoff CS 27's dry or Paragon Traction Action (new white label)
Front- Locked Diff (The sandpaper one, I broke the outdrive of my homemade one in a previous session) 14 lb Silver TC3 Springs, Two narrow number 4 wahsers under the shock lower pivot, thicker plastic spacer under the shock upper pivot for clearance on these Associated springs. Slight bevel to caster block for clearance. 35 weight oil, #57 hole black shock piston bevel on top of each hole. Rear Shock tower on Front. Top of shock third hole out, Front camber link inner middle hole (using rear shock tower on front). Ride height 6.5 mm. Droop maximum without having loose springs. Low roll center plust one shim under inner A-arm pivots. 4 degrees caster. No Kickup. No swaybar. Protoform Stratus Body 5th hole up.
Rear - 14 pound TC3 Silver Spring 35 weight oil, #57 hole black shock piston bevel on top of each hole. Top of shocks second hole out. Ride height 6.5 mm. Droop maximum without having loose springs. Two shims under inner hinge pivots, low roll center position. Long Ball stud on upright (top trimmed off outer camber link ballcup) Inner camber link middle hole, outer all the way out. No antisquat. Rear toe 2.5 degrees with 1/2 degree Losi XXXS uprights. Proline Stratus Body 10th hole up
GTB 6.5
Gearing- I lowered the gear to 90/22 * 1.83 = 7.48. 6 minute practice time, a good 5 minute race time. Profile #1 now with 20% Drag Brake.
Car goes through the bumps at full throttle now on the outside or middle of the straight. The other bump is now unoticable with the shock holes beveled on top.
Car is hooked up now.
Losi JRXS Setup
Track Temp 12-15 C Takeoff CS 27's dry or Paragon Traction Action (new white label)
Front- Locked Diff (The sandpaper one, I broke the outdrive of my homemade one in a previous session) 14 lb Silver TC3 Springs, Two narrow number 4 wahsers under the shock lower pivot, thicker plastic spacer under the shock upper pivot for clearance on these Associated springs. Slight bevel to caster block for clearance. 35 weight oil, #57 hole black shock piston bevel on top of each hole. Rear Shock tower on Front. Top of shock third hole out, Front camber link inner middle hole (using rear shock tower on front). Ride height 6.5 mm. Droop maximum without having loose springs. Low roll center plust one shim under inner A-arm pivots. 4 degrees caster. No Kickup. No swaybar. Protoform Stratus Body 5th hole up.
Rear - 14 pound TC3 Silver Spring 35 weight oil, #57 hole black shock piston bevel on top of each hole. Top of shocks second hole out. Ride height 6.5 mm. Droop maximum without having loose springs. Two shims under inner hinge pivots, low roll center position. Long Ball stud on upright (top trimmed off outer camber link ballcup) Inner camber link middle hole, outer all the way out. No antisquat. Rear toe 2.5 degrees with 1/2 degree Losi XXXS uprights. Proline Stratus Body 10th hole up
GTB 6.5
Gearing- I lowered the gear to 90/22 * 1.83 = 7.48. 6 minute practice time, a good 5 minute race time. Profile #1 now with 20% Drag Brake.
Car goes through the bumps at full throttle now on the outside or middle of the straight. The other bump is now unoticable with the shock holes beveled on top.
Car is hooked up now.
Last edited by John Stranahan; 07-11-2006 at 11:25 AM.
01-12-2006, 01:47 AM
#96
John, it is awesome that you are running again. This saturday will be my first TC race in a couple of years myself. I have not been to Mike's yet but the facility I hear, is top notch! I am excited that you are running again, I'll get to pick your brain again and hopefully setup my new car real well. See you saturday?
01-12-2006, 06:33 AM
#98
Cristian-good to hear from you. There is a Factory Team TC4 at the track sometimes. I'll take a look. I think the angle back of the front drive axles is very milld and won't be a problem. Same for the JRXS. We are running mod with a 10 turn limit or GTB 6.5. There are some pictures of Mikes layout a few posts back.
When the driveshaft axle is angled toward the back like on the XXXS some forward bite is eliminated as the drive axle tends to lift. This is a problem in stock on a high bite track. In mod it tends to keep the front of the car down for more stability.
Spektrum Report with Mod
At the end of each run now the receiver turns the car off completely while I think I am still running close to racing speed. This is fairly aggravating. There will be no crawling to the finish line if I dump early. Hopefully that won't be a problem. The capacitor does not help this situation much as I am running one. It just does not have the capacity.
GTB 6.5 Reverse
I have reverse on the 6.5 I had one spinout yesterday that I had to marshall. Could have used reverse. I set up profile 2 with my 50% drag brake and plan to use this for practice. Generally its not allowed for racing as people will back into traffic.
When the driveshaft axle is angled toward the back like on the XXXS some forward bite is eliminated as the drive axle tends to lift. This is a problem in stock on a high bite track. In mod it tends to keep the front of the car down for more stability.
Spektrum Report with Mod
At the end of each run now the receiver turns the car off completely while I think I am still running close to racing speed. This is fairly aggravating. There will be no crawling to the finish line if I dump early. Hopefully that won't be a problem. The capacitor does not help this situation much as I am running one. It just does not have the capacity.
GTB 6.5 Reverse
I have reverse on the 6.5 I had one spinout yesterday that I had to marshall. Could have used reverse. I set up profile 2 with my 50% drag brake and plan to use this for practice. Generally its not allowed for racing as people will back into traffic.
Last edited by John Stranahan; 01-12-2006 at 06:45 AM.
01-14-2006, 02:14 PM
#99
Track temp 0C 32F at first practice battery. A good tire was Lyn's choice CS 27 Dry. I tried everything else for experiments, but had the CS 27 ready for the main (dry).
My first race in 2 years. Qualified (last)in the A-main. Did not start due to shredded spur from crash in heat 3. I should have goosed the car on the stand in the pit between races. MikesHobbyShop.com (Porter Texas),with Mathew at the helm ran a quality race program. They cooked for us from a built in concession stand. Racing was great and polite.
Novak GTB 6.5 Vs Fantom (Orion top based) 10x1 for Touring Cars
Cristian (Factory Team TC4) and I (Losi JRXS) ran an experiment to see how the GTB 6.5 compared to The Orion Revolution V2 Based Fantom 10 x1 (touring car edition). We started with fresh packs after the race. Neither pack was a pack with exceptional numbers (Racer Packs). We had a 200 foot straight. We turned the corner onto the straight with Christian slightly behind and beside my car coming onto the straight at near race speed (race speed for me) Then we accelerated to the cone which was the turn off for electric cars. Repeated about 6 times. The cars were as close to identical as you could imagine. We had also independently selected identical (effective) gearing for this course. One car was not better at the beginning than the other and then worse at the end. Now you might think that Christians car was at a disadvantage, but he can basically pass me anywhere from better trigger control coming out of the corner. He finished second in the A-main with an untested car. We did make quite a few changes to the FTTC4 during the day. Maybe Cristian can post a setup.
Good. An even match in the 10 turn class.
I have a report that this brushed motor with the angled brushes holds up better than standard brush motor off road. We'll get more data on this as Cristian races his in the touring car more. He did have 4 good runs with no slowing.
Run Time
My practice run time was a good six minutes. In the race (5 minutes) my last lap was only slightly slowed. I'm not that smooth yet though. This run time should improve with more racing and practice.
Losi JRXS Report (Orion Lipo)
I have a report from Robert that the Orion Lipo will not go into his JRXS. He says it does not even get to the point of touching the foam. It just will not go around the corner. You need to angle a pack in and then push it back on this car. The battery is just too tall. He plans to run it off-road.
This JRXS broke a steering rack link. I broke a servo arm. There is no servo saver. It might be good to add a servo saver to the servo arm or put in a flexible servo arm, which is what I did, to keep from breaking these parts. This is for people like me who still crash once in a while, or at least order these spares.
Spektrum Report
I finally received my spektrum capacitor. I moved the Novak capacitor that I was using in the meantime back to my new TC4. It blew up spectacularly with a jet of oil out of its base as soon as I powered it up, so maybe it was weak. I got no glitches with the new capacitor and much better behavior when the pack was dumping. I could slow now or I instinctively got off the throttle, so I could drive back to pit lane to pick the car up.
Losi JRXS Tweak Report
This is a fairly sad report. I set my car on the tweak station before race one (note that I was having trouble turning in one direction). My Tweak was way off. I started tinkering with shock collars, but then I new something else was wrong. I picked the car up, twisted it straight (creaked a bit), and then the tweak could be set with just a small adjustment. The problem was chassis twist caused by the screws up through the chassis that hold the diffmounts at the front of the chassis. All the other screws are locktited in place. I think that this diffmount should have a more substantial square base (cross members) so that this does not happen so easy. In the meantime I will add blue locktite under the head of these 8 screws which I left dry for maintenance. I have had the front diff supports off twice now.
FTTC4 Locked Diff
Cristian broke his solid steel front spool (that hurts you big time in the pocket book). We locked his front standard diff with Losi sandpaper disks (removed the balls) after the races. The car was hooked up better than with a standard diff (tight) or one-way. Reshimmed the gears. Seemed to work. We'll see.
Losi JRXS Diff R&R
I'm used to taking the entire diff outdrive unit out of the car for service. On the JRXS this is quite a pain. There is an easier way. Take the diff apart in the car. Loosen dif screw wheel on. Use the wheel for the wrench. Use a screw driver blade through the slot on the head of the diff screw. Remove rear inner hinge pin mount. Move the arm away. When you loosen the diff screw, you can remove the pulley side outdrive, then the pulley with belt, then inner diff washer. This way you can loktite the diff support in place, never touch them again and help prevent tweak. The aluminum diff tube never really needs to come out of the car, but it will slide out once the pulley and opposite outdrive are removed. I did not need to loosen the belt tension.
Robert had the nicest pit. I'm envious. Note the JRXS in the center. This pic had 11 hits when I replaced it with tighter cropped copy.
My first race in 2 years. Qualified (last)in the A-main. Did not start due to shredded spur from crash in heat 3. I should have goosed the car on the stand in the pit between races. MikesHobbyShop.com (Porter Texas),with Mathew at the helm ran a quality race program. They cooked for us from a built in concession stand. Racing was great and polite.
Novak GTB 6.5 Vs Fantom (Orion top based) 10x1 for Touring Cars
Cristian (Factory Team TC4) and I (Losi JRXS) ran an experiment to see how the GTB 6.5 compared to The Orion Revolution V2 Based Fantom 10 x1 (touring car edition). We started with fresh packs after the race. Neither pack was a pack with exceptional numbers (Racer Packs). We had a 200 foot straight. We turned the corner onto the straight with Christian slightly behind and beside my car coming onto the straight at near race speed (race speed for me) Then we accelerated to the cone which was the turn off for electric cars. Repeated about 6 times. The cars were as close to identical as you could imagine. We had also independently selected identical (effective) gearing for this course. One car was not better at the beginning than the other and then worse at the end. Now you might think that Christians car was at a disadvantage, but he can basically pass me anywhere from better trigger control coming out of the corner. He finished second in the A-main with an untested car. We did make quite a few changes to the FTTC4 during the day. Maybe Cristian can post a setup.
Good. An even match in the 10 turn class.
I have a report that this brushed motor with the angled brushes holds up better than standard brush motor off road. We'll get more data on this as Cristian races his in the touring car more. He did have 4 good runs with no slowing.
Run Time
My practice run time was a good six minutes. In the race (5 minutes) my last lap was only slightly slowed. I'm not that smooth yet though. This run time should improve with more racing and practice.
Losi JRXS Report (Orion Lipo)
I have a report from Robert that the Orion Lipo will not go into his JRXS. He says it does not even get to the point of touching the foam. It just will not go around the corner. You need to angle a pack in and then push it back on this car. The battery is just too tall. He plans to run it off-road.
This JRXS broke a steering rack link. I broke a servo arm. There is no servo saver. It might be good to add a servo saver to the servo arm or put in a flexible servo arm, which is what I did, to keep from breaking these parts. This is for people like me who still crash once in a while, or at least order these spares.
Spektrum Report
I finally received my spektrum capacitor. I moved the Novak capacitor that I was using in the meantime back to my new TC4. It blew up spectacularly with a jet of oil out of its base as soon as I powered it up, so maybe it was weak. I got no glitches with the new capacitor and much better behavior when the pack was dumping. I could slow now or I instinctively got off the throttle, so I could drive back to pit lane to pick the car up.
Losi JRXS Tweak Report
This is a fairly sad report. I set my car on the tweak station before race one (note that I was having trouble turning in one direction). My Tweak was way off. I started tinkering with shock collars, but then I new something else was wrong. I picked the car up, twisted it straight (creaked a bit), and then the tweak could be set with just a small adjustment. The problem was chassis twist caused by the screws up through the chassis that hold the diffmounts at the front of the chassis. All the other screws are locktited in place. I think that this diffmount should have a more substantial square base (cross members) so that this does not happen so easy. In the meantime I will add blue locktite under the head of these 8 screws which I left dry for maintenance. I have had the front diff supports off twice now.
FTTC4 Locked Diff
Cristian broke his solid steel front spool (that hurts you big time in the pocket book). We locked his front standard diff with Losi sandpaper disks (removed the balls) after the races. The car was hooked up better than with a standard diff (tight) or one-way. Reshimmed the gears. Seemed to work. We'll see.
Losi JRXS Diff R&R
I'm used to taking the entire diff outdrive unit out of the car for service. On the JRXS this is quite a pain. There is an easier way. Take the diff apart in the car. Loosen dif screw wheel on. Use the wheel for the wrench. Use a screw driver blade through the slot on the head of the diff screw. Remove rear inner hinge pin mount. Move the arm away. When you loosen the diff screw, you can remove the pulley side outdrive, then the pulley with belt, then inner diff washer. This way you can loktite the diff support in place, never touch them again and help prevent tweak. The aluminum diff tube never really needs to come out of the car, but it will slide out once the pulley and opposite outdrive are removed. I did not need to loosen the belt tension.
Robert had the nicest pit. I'm envious. Note the JRXS in the center. This pic had 11 hits when I replaced it with tighter cropped copy.
Last edited by John Stranahan; 01-15-2006 at 04:32 PM.
01-15-2006, 08:24 AM
#100
Updated setup for 2/26/06
Car is ballistic 15.9 sec fast lap! Avg. lap went from 16.7-16.8 to 16.1-16.3!!!
FTTC4
Front:
30wt oil
blue spring
2 holes in at the top
outside on A-arm
1 tab on both arm mounts
Camber link:
2nd from the inside no washers.
4 deg castor blocks
Arms spaced one washer front mount/ 2 washers rear mount
Locked diff w/ losi sandpaper rings. ( going from very tight diff to oneway to a locked spool, this was the best solution. Car accelerated much better and had better corner speed)
ride height 5.5mm
PLASTIC FRONT A-ARMS
Droop set @ 6 on associated gauge
Black swaybar(thinest AE)
Rear
30wt oil
blue spring
2 holes out at the top
outside on a-arm
4 tabs on both a arm mounts (going up from 2 to four free'd up the rear incredibly and increased front grip. Car went from not turning at all to a fair amount of steering could still use some more off power steering)
2.5 rear toe block
Arms spaced back 2 washers (2f/1r)
Camber links:
All the way inside on bulkhead, one washer underneath stud
Inside hole on Hub carriers
Associated lightened steel differential
ride height 5.5 mm
Losi Rear XXXS hubs, inside hole, centered wheelbase, no washers.
Droop set @ 4 on associated gauge
Motor:
Fantom Vortec 10x1
gearing: 72x24 (straightaway is ~200 ft)
Battery:
SMC IB 3800
TIRES: Takeoff CS27/22
Traction compound: Ground Effects
Car is ballistic 15.9 sec fast lap! Avg. lap went from 16.7-16.8 to 16.1-16.3!!!
FTTC4
Front:
30wt oil
blue spring
2 holes in at the top
outside on A-arm
1 tab on both arm mounts
Camber link:
2nd from the inside no washers.
4 deg castor blocks
Arms spaced one washer front mount/ 2 washers rear mount
Locked diff w/ losi sandpaper rings. ( going from very tight diff to oneway to a locked spool, this was the best solution. Car accelerated much better and had better corner speed)
ride height 5.5mm
PLASTIC FRONT A-ARMS
Droop set @ 6 on associated gauge
Black swaybar(thinest AE)
Rear
30wt oil
blue spring
2 holes out at the top
outside on a-arm
4 tabs on both a arm mounts (going up from 2 to four free'd up the rear incredibly and increased front grip. Car went from not turning at all to a fair amount of steering could still use some more off power steering)
2.5 rear toe block
Arms spaced back 2 washers (2f/1r)
Camber links:
All the way inside on bulkhead, one washer underneath stud
Inside hole on Hub carriers
Associated lightened steel differential
ride height 5.5 mm
Losi Rear XXXS hubs, inside hole, centered wheelbase, no washers.
Droop set @ 4 on associated gauge
Motor:
Fantom Vortec 10x1
gearing: 72x24 (straightaway is ~200 ft)
Battery:
SMC IB 3800
TIRES: Takeoff CS27/22
Traction compound: Ground Effects
Last edited by CristianTabush; 02-26-2006 at 05:05 PM.
01-19-2006, 10:18 AM
#101
Roll Stiffness
We had a little tuning session at Mikeshobbyshop.com. We concentrated on getting the roll stiffness right for the track on the JRXS and the FTTC4. Roll stiffness is how hard the car is to roll to the side in a corner. Stiffer springs increase roll stiffness, higher roll centers (lower pivots shimmed upward) increase roll stiffness. Sway bars increase roll stiffnes. There is range of roll stiffness that seems to give you the best traction for a given tire and track. At Mikes the spring rate required seems to be in the 12.5 to 17 pounds per inch range. Roll centers low or medium.
We also wanted to verify how the roll stiffness affects handling with a car that has a locked diff. Everything seems to be backwards from a car running a standart diff or one-way. I have my theories on why this is so, but Cristian did verify this with a couple of simple tests that I had peformed previously.
So with a locked diff
Higher spring rate in front (more pounds/inch on the springs, higher roll stiffness) - gives you more mid corner steering traction. Too high and the car will oversteer badly. This is opposite of what you see with a one-way or standard diff.
Higher roll center in back (shim inner hinge pin pivot blocks higher). This will increase the rear roll stiffness. This will cause the locked diff equiped car to rotate less, more rear mid corner cornering traction. It does just the opposite with a one-way.
Sway bars - Increase roll stiffness. On the front of a locked diff equiped car a tiny bar adds a touch more mid corner steering traction. This is opposite of what they do on a one-way equiped car.
I needed a little more roll stiffness to hook up better with CS 27's I tried the 14.5 lb spring in front all the way in, but this felt too stiff. I ended up using the 12.5 spring all the way out, but I needed just a bit more to balance the cars oversteer understeer. I added a tiny sway bar in front. This is probably equal to moving 1/2 a hole out on the shocktowers. Christian is running a more substantial sway bar in the front, but may change to heavier springs next. I ordered an extra rear shock tower that has an extra hole. (note that on the XXXS I had the same problem and losi eventually made a spring in between to solve the problem. The green spring.)
I have updated my setup post here on this thread.
MY CURRENT JRXS SETUP
Note that on the JRXS the sway bar support has a large slot and a small slot. Use the small slot for the tiny bar. I also changed to a slightly longer aluminum screw to simplify adding the bar. You don't have to take the nut comletely off the screw now.
Both of us have some chassis wear on the bottom outer edges from roll in the corners. I have solved my problem by beveling the edges of my chassis where there was wear, raising my ride hight a little, and increasing the roll stiffness a little. I get no more contact. We are pondering a solution on the FTTC4. It is handling quite well as is, but the chassis is getting excessive wear from running a low ride height.
I would be glad to discuss opposite views on this locked diff matter. This is what we have observed on both a high grip indoor asphalt track and a medium grip very high speed outdoor track.
And here is a pic of the competition FTTC4. OK I made some minor changes, but I can put it back like it was. Cristian was running a motor cooling fan. I removed it for the photo. The car has good side to side balance, almost even front to back balance. You can pick both ends of the car up in the middle with two X-acto knife points and check your side to side balance. The Fantom motor with "Sprint" brushes went 6 runs in the touring car before the motor needed attention. The enduro brushes are on line for the next test.
Note that Cristian removed the upper chassis plate posts to increase chassis flex on this medium grip asphalt. He preferred this over using the spine screws. I would prefer this as well on this car, because if you remove some spine screws you are going to get some stick-slip action on the mating parts that will be constantly changing the tweak (twist) of the car.
We had a little tuning session at Mikeshobbyshop.com. We concentrated on getting the roll stiffness right for the track on the JRXS and the FTTC4. Roll stiffness is how hard the car is to roll to the side in a corner. Stiffer springs increase roll stiffness, higher roll centers (lower pivots shimmed upward) increase roll stiffness. Sway bars increase roll stiffnes. There is range of roll stiffness that seems to give you the best traction for a given tire and track. At Mikes the spring rate required seems to be in the 12.5 to 17 pounds per inch range. Roll centers low or medium.
We also wanted to verify how the roll stiffness affects handling with a car that has a locked diff. Everything seems to be backwards from a car running a standart diff or one-way. I have my theories on why this is so, but Cristian did verify this with a couple of simple tests that I had peformed previously.
So with a locked diff
Higher spring rate in front (more pounds/inch on the springs, higher roll stiffness) - gives you more mid corner steering traction. Too high and the car will oversteer badly. This is opposite of what you see with a one-way or standard diff.
Higher roll center in back (shim inner hinge pin pivot blocks higher). This will increase the rear roll stiffness. This will cause the locked diff equiped car to rotate less, more rear mid corner cornering traction. It does just the opposite with a one-way.
Sway bars - Increase roll stiffness. On the front of a locked diff equiped car a tiny bar adds a touch more mid corner steering traction. This is opposite of what they do on a one-way equiped car.
I needed a little more roll stiffness to hook up better with CS 27's I tried the 14.5 lb spring in front all the way in, but this felt too stiff. I ended up using the 12.5 spring all the way out, but I needed just a bit more to balance the cars oversteer understeer. I added a tiny sway bar in front. This is probably equal to moving 1/2 a hole out on the shocktowers. Christian is running a more substantial sway bar in the front, but may change to heavier springs next. I ordered an extra rear shock tower that has an extra hole. (note that on the XXXS I had the same problem and losi eventually made a spring in between to solve the problem. The green spring.)
I have updated my setup post here on this thread.
MY CURRENT JRXS SETUP
Note that on the JRXS the sway bar support has a large slot and a small slot. Use the small slot for the tiny bar. I also changed to a slightly longer aluminum screw to simplify adding the bar. You don't have to take the nut comletely off the screw now.
Both of us have some chassis wear on the bottom outer edges from roll in the corners. I have solved my problem by beveling the edges of my chassis where there was wear, raising my ride hight a little, and increasing the roll stiffness a little. I get no more contact. We are pondering a solution on the FTTC4. It is handling quite well as is, but the chassis is getting excessive wear from running a low ride height.
I would be glad to discuss opposite views on this locked diff matter. This is what we have observed on both a high grip indoor asphalt track and a medium grip very high speed outdoor track.
And here is a pic of the competition FTTC4. OK I made some minor changes, but I can put it back like it was. Cristian was running a motor cooling fan. I removed it for the photo. The car has good side to side balance, almost even front to back balance. You can pick both ends of the car up in the middle with two X-acto knife points and check your side to side balance. The Fantom motor with "Sprint" brushes went 6 runs in the touring car before the motor needed attention. The enduro brushes are on line for the next test.
Note that Cristian removed the upper chassis plate posts to increase chassis flex on this medium grip asphalt. He preferred this over using the spine screws. I would prefer this as well on this car, because if you remove some spine screws you are going to get some stick-slip action on the mating parts that will be constantly changing the tweak (twist) of the car.
Last edited by John Stranahan; 01-19-2006 at 04:41 PM.
01-19-2006, 11:51 AM
#102
new post and pic above too.
GTB 6.5 Brakes
Cristian and I swapped cars just briefly so I could note his impression on a couple of flavors of tires, some 28's and some 24's. They both sucked according to both of us. The car was very loose (track temp 15 C) We never have got them to hook up even in stock. CS 22's and CS 27 seem to work better. Anyway our immediate impression is that my brakes are about 1/2 of his brakes even though mine are turned all the way up. I sent a note to Novak and got a very speedy reply. Here is a quote from the tech department.
"Well, the overall braking power of a Brushless system is NOT equal to regular motors. Usually, the braking is good enough for nearly all applications other then "very heavy" braking for tight tracks.
The way I've described it to the engineers is that it feels about right for most normal driving conditions, but for Panic braking, or emergency stops its not good enough.
Sometimes turning up the "minimum brake" will help address some of the initial brake feel, makes them "come on quicker" so they feel a bit more usable. So try that first, but it's possible it won't ever be as strong braking wise as a regular motor."
GTB 6.5 Brakes
Cristian and I swapped cars just briefly so I could note his impression on a couple of flavors of tires, some 28's and some 24's. They both sucked according to both of us. The car was very loose (track temp 15 C) We never have got them to hook up even in stock. CS 22's and CS 27 seem to work better. Anyway our immediate impression is that my brakes are about 1/2 of his brakes even though mine are turned all the way up. I sent a note to Novak and got a very speedy reply. Here is a quote from the tech department.
"Well, the overall braking power of a Brushless system is NOT equal to regular motors. Usually, the braking is good enough for nearly all applications other then "very heavy" braking for tight tracks.
The way I've described it to the engineers is that it feels about right for most normal driving conditions, but for Panic braking, or emergency stops its not good enough.
Sometimes turning up the "minimum brake" will help address some of the initial brake feel, makes them "come on quicker" so they feel a bit more usable. So try that first, but it's possible it won't ever be as strong braking wise as a regular motor."
Last edited by John Stranahan; 01-19-2006 at 03:09 PM.
01-21-2006, 02:14 PM
#104
Another track report.
My car was hooked up well on the first pack. Novak had suggested lowering the gear ratio to get more brakes and acceleration. I took one tooth off the pinion. This gave me more brakes. This also made the motor feel more ordinary as the spool up time was now limiting acceleration. I changed the spur to a smaller spur as a compromise. 7.48 overall. CS 27 dry were hooked up at 11 C. Then I had trouble which I finally traced to rear diff that would get tight and loose. Felt just like a tire that came partly unglued. There is some trash that got into the space between the aluminum diff tube and the eccentric. It left scars. The diff balls also were dirty and a little dry. I still have to pull the diff screw out to clean this bearing. This would not happen on a XXXS or TC4 as these items are more protected on those cars. My new rear shock tower for front use is in. I report on this later. The goal is to eliminate the little sway bar with its attendant pivot friction.
Cristians car was strapped. Sadly, he tried some Paragon Ground Efffects and it worked. This is the nasty, leave the pit bag, pit rag, and car in the garage, oudoor use only stuff. I have a few other traction compounds on order to try out. Cristian might update his previously posted setup.
We both made some aerodynamic changes to suit the high speed track better. I lowered the rear of my body 2 holes (it needed retrimming). This helped top speed and high speed steering traction. Cristian trimmed a little off the back wing a while ago.
My car was hooked up well on the first pack. Novak had suggested lowering the gear ratio to get more brakes and acceleration. I took one tooth off the pinion. This gave me more brakes. This also made the motor feel more ordinary as the spool up time was now limiting acceleration. I changed the spur to a smaller spur as a compromise. 7.48 overall. CS 27 dry were hooked up at 11 C. Then I had trouble which I finally traced to rear diff that would get tight and loose. Felt just like a tire that came partly unglued. There is some trash that got into the space between the aluminum diff tube and the eccentric. It left scars. The diff balls also were dirty and a little dry. I still have to pull the diff screw out to clean this bearing. This would not happen on a XXXS or TC4 as these items are more protected on those cars. My new rear shock tower for front use is in. I report on this later. The goal is to eliminate the little sway bar with its attendant pivot friction.
Cristians car was strapped. Sadly, he tried some Paragon Ground Efffects and it worked. This is the nasty, leave the pit bag, pit rag, and car in the garage, oudoor use only stuff. I have a few other traction compounds on order to try out. Cristian might update his previously posted setup.
We both made some aerodynamic changes to suit the high speed track better. I lowered the rear of my body 2 holes (it needed retrimming). This helped top speed and high speed steering traction. Cristian trimmed a little off the back wing a while ago.
01-21-2006, 05:05 PM
#105
How to correctly use digital weighing scales for car tweak
Hi John, we recently bought 4 digital weighing scales to be used for tweaking our cars. I hope you don't mind, is it possible for you to teach us the correct procedure in tweaking with digital scales on all four corners of the car.
I tried doing it a couple of times but i can't seem to arrive at correct numbers on each wheel. The numbers seem to keep on changing whenever I compress the suspension, somehow, it's like a hit or miss thing on the numbers. I feel like I'm missing out on the correct procedure. I hope you can help us newbies. Thank you for your time
Sonny
I tried doing it a couple of times but i can't seem to arrive at correct numbers on each wheel. The numbers seem to keep on changing whenever I compress the suspension, somehow, it's like a hit or miss thing on the numbers. I feel like I'm missing out on the correct procedure. I hope you can help us newbies. Thank you for your time
Sonny