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Old 05-15-2008, 05:21 PM   #2041
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Moving the rear of the rear shock up is going to give it a little more action even if you raise the front with it. The spring will act slightly stiffer. You probably wont move it enough to notice any changes. Stiffer center spring transfers load faster to the front to give you a little more steering traction early in the corner (more turnin). This is less noticable than changing say a front spring.
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Old 05-16-2008, 09:46 AM   #2042
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Think of it this way - it's all about leverage.

If the position on the arm is in, the arm has more leverage and the shock/spring will act "softer" - move it out and the arm has less leverage so the shock/spring will act "stiffer".

Same thing with the shock tower. The more the shock is laid down, the "softer" the shock/spring will act because it will have less leverage against the arm; the closer to 90 degrees, the more leverage and the "stiffer".
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Old 05-16-2008, 06:39 PM   #2043
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Boomer -Thanks. Now talk to me about chassis rake again.

Ackerman
Ackerman allows the inside front wheel in a turn to turn a tighter radius turn than the outside wheel. This prevents scrub. Seems that racing 4 cell super stock on asphalt is a lot about reducing scrub so here is the complaint and here is what I did. We did discuss and adjust ackerman on my wide pan car earlier in this thread by using different servo saver widths.

A good corner radius for a fast lap seems to be about 16 feet on our course. 18-20 feet is possible if you go really wide. My car was doing this turn just fine but on occasion in traffic you pass on the inside on a straight and then want to take a little tighter radius turn or more likely an assymetrical turn where you come in tight and go out wide. My car was scrubbing some speed on the tighter radius turn. On a road course you use this scrub to brake for the apex. In stock oval it just slows you down uneccesarily. I wondered with all the adjustments on oval cars these days why there is not an adjustment for Ackerman. Here is what I did. I wanted to try more ackerman than available on the associated steering arm and less ackerman. The maybe succesful adjustment is shown in the pic. The blue aluminum part is a lower shock mount for a miniT. (If you buy miniT arms ($2.). you get a pair of these mounts. If you buy the Atomic mods Aluminum Arms you get aluminum blue ones (7$).)

Lets say those steering arms pointed straight back (instead of at a 45 degree angle) and lets say the two steering arms were connected with a straight link like on some Corralys. Then you would have no ackerman. The left wheel would always be parallel with the right when you turn. At 45 degrees but still connecting both arms with a straight link you would have perfect ackerman. A TC3 with its sliding steering rack also has perfect ackerman. by perfect, I mean, the angles change exactly like they are supposed to all the way from big sweeper turn down to tight radius turn. So what I did with my little adjustment is move the steering arm closer to straight back. I removed some ackerman. I also used the little plastic piece that is cut from an old steering arm to add ackerman for one experiment.

I did notice that on one of CRC's earlier cars there was a steering arm extension for the associated steering arm that was an adjustment to ackerman. I don't see that on their prostrut front end, but it may be built in.

With more ackerman (the plastic piece) the audible scrub seemed to diminish on corner entry, but I developed a mid corner and late corner push. Steering was less. I would think this had to be from more front wheel scrub reducing the effective steering.

With less ackerman there was no audible corner entry scrub with various radius turns and, importantly, mid corner to late corner I could apply full throttle without going wide. This is an improvement. I will have to prove it with lap times though. I did some geometric measurements as well. When the right front wheel turns 8.5 degrees (about what I use in a race). The left front wheel turn a little sharper at 9.5 degrees (stock). I took off maybe .25-.5 degrees of this difference and only made the change on the right front. The effect was smaller this way and is always split between left and right. The effect was hard to measure on the combination square, but I could certainly note the difference on the track.

Spring Rate
I did a heavy spring rate experiment in the previous race which proved to be slower. Because of this I went lighter on the front than what I use on the road course open mod. The 200 mm car felt very good and fast. Steering was more precise than ever. The race will tell.
I have noticed that the BMI team has been experimenting with lighter front springs on their 4 cell road car with pretty good success as well.
When running open mod these lighter springs make the car get sloppy, but with 4 cell super stock they feel about right.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-ackerman-adjustment-001-resized.jpg  

Last edited by John Stranahan; 05-19-2008 at 12:54 PM.
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Old 05-16-2008, 06:51 PM   #2044
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13.5 LiPo
It is my opionion that after a guy has run a couple of years of stock or superstock, he should be ready for some light mod work and leave a space for some of the stock guys to place. For this reason I did an experiment on the flat asphalt oval. I took the same super stock 13.5 motor that we run on 4 cell and just upped the voltage with a 6 cell equivalent LiPo. I did this with my wide pan car. Gearing ended up only 1 pinion tooth less than 4 cell. Motor temps went up from 140 to 170F for an 8-10 minute run. Now were talking.

Here is the track experience. With LiPo, I now accelerate out of the turn on part throttle, I see the air dam lift a bit (cool). Acceleration is surprisingly fast when standing at track level, but just about right up in the 12 foot high drivers stand. I reach full throttle at mid straight and then start to slow for the corner. The throttle roll on and roll off are important to maintain smooth momentum. I corner with about 1/4 throttle. No slamming the throttle full at mid corner and holding it there until corner entry any more. A spec LiPo battery such as the new coming TrackPower 3600 with a hard case would be ideal. No more battery war, but still as much power as you need at any given time. No car setup change was need, little gearing change is needed.

If you bought a charger recently chances are it will charge a LiPo. One LiPo pack will easily outlast 4 NiMH packs and still be performing well on the track. The hazard is low with modern chargers and hardcase batteries that are roar approved. I have never bought a LIPO that did not exceed its label specs on capacity. 4 of seven of my NiMH's had to be returned due to deterioration of as much as 25% from just sitting for sale for a few months. That is close to industrial specs for a used up battery. Jeff has trouble getting these NiMH 4 cell packs for the shop. I have trouble finding them on the Web.

Charging at 1 C (3.6 amps for our spec battery) is desired for the best lifetime. It may even double the life over using 2C which can also be used.
John

Last edited by John Stranahan; 05-16-2008 at 07:03 PM.
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Old 05-18-2008, 08:35 PM   #2045
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Race Report

Ackerman
The changes to Ackerman and the soft spring and return to GRP tires, all helped today. The car was strong again. I could quickly gain on the competition where last week it was a struggle. The main gain was an improvement to Ackerman which added steering for me. I noticed that the guys that got tech help at the nats swept the tie rods backwards from the middle out by quite a bit. On road I usually run them straight out by putting balls on the back side of the servo horn. This angling back changes the Ackerman. (I think it increases it though I am not positive) this may help on carpet. I reduced my Ackerman with the little miniT part for asphalt.

Durability
The beefing up tricks and the flexible bumper helped. 3 other guys broke their graphite bumpers today which lost the aluminum front body mount and rendered the car inoperative for the heat. I wonder if they should at least use plastic front body mounts. The Aluminum post develops tremendous forces at the base in a crash. They have very good leverage on the small base. This breaks the graphite bumper. CRC looks like they provide a srew on type of body post that is made of plastic on their battle axe. These may become available soon. I am still using body clips like most of the road guys. You reduce your chance of loosing a body post if you screw it to the chassis. The chassis rarely breaks (unless you put aluminum body posts on it). There is a good crossbreed post that has the base aluminum and the top part plastic but it is high cost.


I popped a ball cup on the front end in a full speed head on crash with the other guy driving at good speed the wrong way. (Too little dual rate to get turned out of the way probably). One of those hard to prevent events. It broke his car and popped my ball cup. This popping off is a deficiency that, I fixed with the next genertion of my front end. The problem is inadequate downtravel of the tie rod (which you only encounter in a crash). This levers the tie rod end off the steering arm ball. I cushioned the down travel of the arm with foam to help this problem. (I put downtravel limiting screws previously and just broke the arms from the hard stop instead of preventing the tie rod popping off.) I would say durability of the car is very good now. I finished 3 laps ahead and qualified first. The first place start was a great help in avoiding traffic at the start. Now my times are about the same as last week, but we had better traction last week. A day with less wind will help to prove the ackerman change. Best laps were as good as ever, but with less traction available.

Another tip from the nats. Put a second wrap of strapping tape at right angles to your normal wrap to keep that battery on board in the crashes.

BSR tires
The BSR tires performed well on the LiPo 13.5 powered pan. This feels a little like a mild mod maybe slightly less than a well tuned 19 turn. It gave the wide car more steering traction and rear forward traction. I am going to try Magentas on the narrower oval car eventually. I have not written this tire off by any means especially since my shop can obtain them.

Back of the Body Cutout On-road and Oval
Most oval guys and 1/10 wide pan car guys cutout the back of their bodies to have better down force. I had done a small test in a windtunnel with a wide pan that showed air actually entering the body just under the wing. This showed on the little propeller type of wind meter. The guys went to the nats with most of the rear body in place. They received tuning advice to remove it. The tuner swore he could see the car with the back end lower in the corner. The guys swore they noticed an improvement. Do I think he actually saw a superstock powered car rise up less. Well I doubt it. But the drivers thoughts are hard to ignore. So there you have it.

I trim to the top of the bumper only lately to keep the rear of the body strong. The cut removes a few grams. I am very slightly overweight. I don't think my lap times suffered from the more complete rear of the body, but we race on asphalt and not carpet. It is possible on carpet that the rear tires push further into the roadbed and stream their jet of air rearward at a higher angle than I achieved on a windtunnel (without a moving carpet roadbed). You don't see this cutout mod on full size cars that are not complete also with a huge rear diffuser.

John

Last edited by John Stranahan; 05-19-2008 at 12:49 PM.
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Old 05-19-2008, 09:41 AM   #2046
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Boomer -Thanks. Now talk to me about chassis rake again.
John
I never did figure out the chassis rake thing - I just did what I was told and kept it level or a bit down.
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Old 05-19-2008, 12:59 PM   #2047
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Boomer thanks-I did a search where we discussed rake earlier in the thread and also on the 1/10 pan thread. It seems if you raise the center pivot you get more forward traction. Lower the pivot less rear traction. The pivot height determines how much antisquat the car has. There are a several votes for this now including the oval racers at the oval nats. I ran the road car pretty level most of the time. If I get that CRC battle axe, I'll do some more experiments with this.

pic is of my current rear cutout. Discussion above.
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Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-monte-carlo-hd-light-weight-005.jpg  

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Old 05-19-2008, 01:13 PM   #2048
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Boomer thanks-I did a search where we discussed rake earlier in the thread and also on the 1/10 pan thread. It seems if you raise the center pivot you get more forward traction. Lower the pivot less rear traction. The pivot height determines how much antisquat the car has. There are a several votes for this now including the oval racers at the oval nats. I like you ran the road car pretty level most of the time. If I get that CRC battle axe, I'll do some more experiments with this.
john
Want one????????? Never touched the track yet!!!!!!
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Old 05-19-2008, 01:34 PM   #2049
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Here is the story. Frank Calandra (owner of CRC) had offered me some CRC products to test, nothing specific. Jason Breiner from BMI made a similar offer after we had settled our differences and got to know each other better. I requested a battle axe from CRC as we are racing oval right now. He is thinking it over. They are not available from Horizon yet. Horizon says early June. At that time my shop will have a couple for sale. Soon we will be purchasing a large indoor CRC ozite carpet. Maybe after that Frank will consider my request. The indoor track is almost ready for carpet.
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Old 05-19-2008, 01:44 PM   #2050
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Here is the story. Frank Calandra (owner of CRC) had offered me some CRC products to test, nothing specific. Jason Breiner from BMI made a similar offer after we had settled our differences and got to know each other better. I requested a battle axe from CRC as we are racing oval right now. He is thinking it over. They are not available from Horizon yet. Horizon says early June. At that time my shop will have a couple for sale. Soon we will be purchasing a large indoor CRC ozite carpet. Maybe after that Frank will consider my request. The indoor track is almost ready for carpet.
John
John PM me your address and I will send you my car for testing. Just send it back when you are done. I'm not using it.
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Old 05-19-2008, 06:13 PM   #2051
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PM sent. Exciting news. That will give me a head start.
John
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Old 05-20-2008, 09:29 AM   #2052
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PM sent. Exciting news. That will give me a head start.
John
The car is on the way. Check your PM,
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Old 05-20-2008, 01:16 PM   #2053
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Thanks.
Expect a new thread starting soon with this title.

CRC Battle Axe, GenXPro 10, 1/10th pan, LiPo, Oval, On Road, Tips and Tricks.

I will continue this thread there. The Pantoura thread will still be available by link from the new thread. A lot of interesting things back in this thread.

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Old 05-26-2008, 01:23 AM   #2054
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Here is an interesting pic of a velodrome car that shares many design similarities to my 3-link prototype. There is a front of pod mounted Panhard bar (track bar). It has Rear mounted vertical shocks. Shock tower tubular cross brace at the rear. G10 plate frame rails etc.
John
i saw that car first hand.. and must say it is a work of art. it had troubles with "bouncing" at the local velodrome track (that's really rough) but its rear end is the smoothest ive seen for "that" type of car.

here is a pic i snatched up of the rear...



ps.. the owner is from japan ;-)
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Old 05-26-2008, 10:50 AM   #2055
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John, what kind of shocks are you using on your front- end? Are there different springs available??
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