T4-RC8 RACER77

thank u john i am going to the gen x 10 car cause of the batteries and the front, i mean the pillow ball set up,

John Stranahan

iTrader: (27)

McPappy Dart

Here is a stolen spy shot of a new oval kit the McPappy Racing Dart. It has some interesting features. The T-Plate is suspended by an overhead frame to achive the lowest possible position. He has molded his own center pivot plastic supports which look to be a larger size. It is LiPo ready with a very nice strap to hold the LiPo hard case down. The Pod is very open like the Battle Axe. The left side front suspension has a generous adjustment for the inner upper A-arm to change the camber gain. Their photography is outstanding. Flex has been adjusted with the use of Cad Cam. The car is a T-plate car with tripple rear shocks. The top plate is one sided like the battle axe.

Very nice!

John

John Stranahan

iTrader: (27)

Wide Pan On Road, New CRC based front suspension

I have the wide pan ready for another test due to an early Christmass Speed Control. LRP TC edition.

In the last test I had all plastic CRC mounts on the front suspension for flexibility in the crashes. Although this plastic mount is plenty rugged for its intended use as an upper A-arm mount, the mount used on the lower A-arms failed in a crash. The mode of failure was the screws split the screw bosses molded into the mount. Note again this will never happen if used as intended for the upper mount only.

I put in two optional aluminum CRC mounts from the Pro Strut Front suspension for the lower mounts and retested. In the photo you can also see the triangulation of the lower arms which stiffened them considerably. The goal here was a rugged caster setting that would not lose caster with a mild tap of the flapper boards by bending the arm or mount.

Panhard Bar to front of motor.

I have also move the Panhard bar. This will be the first test in the new position. Also installed on the car is a full width front diffuser which worked really well.

First pic is a good view of the Aluminum suspension mount I added. I used a 0 degree version.

I am testing an LRP 3.5 motor. Geared 13/90. Hopefully the rotor will not explode.

John

John Stranahan

iTrader: (27)

Oval Meet
Jimmy's Battle Axe Test and Tune

Jimmy has a brand new original model Battle Axe at the track. At first he was not sure to run it or not. Today it was at the track built up. Having some experience with the car things went fast and well.

Firstly the front suspension was tight. We took off both kingpins and polished them until they dropped through the lower bushing without friction. We loctited the little brass set screws by previous experience. We ran the kit red front progressive springs pointy side up with no upper spring bucket. They may be a little soft. I notice in my previous setup I have written purple springs which are 1# stiffer. Next session we should try the purples as we had a tad too much steering traction at days end.

We set the left down tweak with scales to 12 ounces. This means the left rear weights 12 ounces more than the right rear. This proved to be about right again but was difficult to obtain with kit springs. We changed to a Wind Tunnel right rear copper 15#, and left rear orange 6#. I reversed the nut on the right rear shock and added an RC18T spring collar to the inboard end of the nut. All this was required to get 12 ounces. Note there is a stiffer set of Windtunnel springs now available that would make this task a little easier. Also, readjusting the length of the plastic rod ends on the right side shock may have helped.

We offset the left rear outboard about 8-9 mm. This makes the car go to the right out of the corner instead of looping in toward the inner board on corner exit.

We used 35 weight oil all arround. The center spring was medium about 15 lbs by touch and was silver in color. Don't know the brand, so I cannot be precise here.

We set ride height to 5.5 mm in the front by adding a 3 mm CRC shim to the 5 mm shim on the car. We set the rear at 7 mm for now. This will drop to a good height with some tire wear. He had all new uncut tires on the car.

Unfortunately the car came with a new radio. 1/4th of your oval setup is in the radio. I removed huge amounts of exponetial (nearing 100). I think this was put in backwards as the car was very sensitive near the middle and would tend to huge weaves with slight movement of the wheel. Anyway go easy on this and usually you want to go negative to remove sensitivity near the middle. I removed half of the travel. I tightened the servo saver screw one full turn. Finally the radio was almost right. The dual rate adjustment on the DX3 radio was unknown to me or I would have cut steering some more. We had too much. I also felt a small size servo saver was not returning to center well. Use the Kimbrough Medium Servo saver instead.
Kimbrough 131 Medium servo gear saver Hitec$3.89
Kimbrough 201 Medium Servo Saver, black, Includes adaptors for Futaba, Hitec, Airtronics$4.95

We set chassis level. We will set rear droop to about 2 mm. Right now its about 5-6 mm.

Jimmy was running the typical oval wing. I increased angle of attack to match the winshield which I have heard is good for flat asphalt. I believe this is in the Hypedrive tips Barry posted earlier in this thread. This helped pin the rear down better in the turns.

We finished the session on xxPink left front, Purple right front, Pink left rear, XXPink/purple right rear. The car drove well. We still had too much steering traction. A little stiffer front spring should cure that. As we finalize this setup I will make changes to my original setup on this car. We have learned a good bit about tires since I posted a battle axe setup before.

pics, some cars from todays meet.
John.

John Stranahan

iTrader: (27)

Wide Pan Dual Dynamic A-arm front suspension

I received another set of Aluminum Caster Blocks now to reinforce the lower A-arm inner suspension mount with a sturdier part. I also put one above to add stiffness to maintain caster. This seems to be really important. See the pic. They are really nice looking parts, intricately machined on six sides. CRC part #3360.

Ron asked me if we would still need a better front suspension on the smoother track. My answer is that the car was not only more blowover proof, but it was 1.3 seconds faster running the road course compared to a standard wide pan. Ron is assembling his own 1/10 wide pan up to give me some electric high speed competition. His front suspension will be base on the Associated B4 buggy with pan car steering blocks. It looked pretty smooth on the bench. Road test to come.

Mikes-HobbyShop.com News

In preparation for the 2010 1/10 Nitro Sedan Worlds, Construction will begin on an all new asphalt surface for the big road course and our oval about December 15th or so. With any luck we will have a slightly wider oval on 3 lanes of the new track near the big permanent drivers stand. This will require a new detector loop which was holding us back previously from moving there. A couple of swinging or hinged boards will be put in place. Traction and smoothness should be super. The wide pan is going to scream. Our LiPo 13.5 oval class will be ideal on the slightly longer run line, wide 1/8 th scale lanes, and tall drivers stand. They are already great on our short oval. The straight on the road course will be about 40 feet longer, up now to 250 feet or so. Top speeds on the road course should be near 70 mph from the improved smoothness, better traction, and longer length. Stay tuned.

Concrete Flat Oval
In the meantime we will do some parking lot racing on the concrete next to the track. Sugar works there as well.

John

John Stranahan

iTrader: (27)

There were well over 200 views since my last post. Thanks.

Pan Car Roll Center, Road and Oval

I am going to discuss chassis roll and jacking forces first as it is helpful to understand these two items when selecting a good roll center. Also note that the pan car is not nearly as sensitive to roll centers as a touring car.

The first pic shows the factors that affect chassis roll. Centrifugal force acts on the center of gravity (top of dashed line) forcing the car to the outside of the corner (the frame of reference is the driver in the car). Tire forces act to the inside of the corner through the roll center (bottom of dashed line) which is usually lower in the car than the center of gravity. Because there is a short distance (a lever length) between the center of gravity and the roll center the chassis rolls.
A car that is difficult to roll has a high roll stiffness. This is either from stiff springs or a high roll center which reduces the lever length. A car with a high roll stiffness is very responsive to driver input, there is little chassis roll to delay driver inputs. This is at the expensive of some cornering force as the outside tires load up quicker and are less compliant (comform less) with the road because of the stiffness.
A car with low roll stiffness is better in low traction conditions. The weight transfer to the outside is delayed a bit’ the tires maintain better traction. The tires are more compliant with the road at the lower stiffness.

Chassis Jacking
There is another important force that we try to minimize while cornering. This is Chassis Jacking. See the second pic. The tires traction force acts through thte roll center to make the car go around the corner. If the roll center is above the ground part of this force is used up raising the chassis. If traction roll is an issue this is to be avoided. Chasiss jacking is the least and cornering forces are most efficient when the roll center is near the ground.

On carpet or very high traction use a low roll center near the ground, but generally stiff springs to keep a high roll stiffness.. On asphalt you can use the roll center as a separate handle on roll stiffness. If the springs are about right for the bumpy conditions, but you want the car to respond better, raise the roll center to increase roll stiffness. If you need a little more traction when it is slick lower the roll center a little.

Pan Car front roll center.

Here is the procedure for drawing a roll center for a strut type of suspension. You draw a line along the upper A-arm and extend it. You draw a line perpendicular to the kingpin at the center point of its lower pivot ball and extend it. Where these two lines meet is called the instant center. Then draw a third line from the bottom of the tire to the instant center. It is common on my road cars to have different camber on left and right so I have drawn the diagram in pic 3 with -2.5 degrees of camber on the right front and -3.0 degrees of camber on the left front. The roll center comes out low, slightly below the ground. The car is supple, but still responds well with stiff front springs. The stiff springs are necessary to keep the chassis off the ground on the high speed straight. Plenty of downforce is developed.

Now the last time I discussed pan car roll centers quite a discussion developed. The point of contention was that the kingpin angle and thus the Camber of our front tires has an effect on the roll center. Since we are well into negative camber all the time we end up with good roll centers. I drew a diagram with the two tires at a positive camber and roll center is quite high. Thus, the low roll center in the fourth pic is a surprise to me. But here it is.

On the oval it is common to have the left side tire with positive camber. Pic 4 shows that the roll center ends up below the ground slightly to the left of the car (to the right on the diagram). This is OK as it is still low. The lines from the tires diverge to the left in the diagram so they are joined by extending them to the right.

To lower roll center then, raise the upper inner A-arm. On an oval car this has the most effect on the right side which has normal negative camber. The left side inner upper A-arm pivot can be raised, however, to reduce the negative camber gain of the tire, but there is little effect on the roll center. (see the McPappy car) Negative camber gain means as the suspension goes up into bump, negative camber is added by the suspension to compensate for chassis roll. As the left side tire goes up in bump the camber becomes more negative; this is not helpful on the always inside left front tire on the oval.

Fifth pic, Front of Wood Racing Oval Car

Roll Center Program
I also have available an excell file that is a program to calculate roll center on the front of a pan car. It is written by Steve Curtiss who was a Winston Cup Head of chassis design for a team. The program requires you to measure parts of the car. [email protected].

John

jeremy reed

iTrader: (7)

does anyone have or know someone who has an sk modified roller for sale?

lidebt2

iTrader: (21)

YHPM

jeremy reed

iTrader: (7)

.................

jeremy reed

iTrader: (7)

i am interested,can you send me some [email protected]

John Stranahan

iTrader: (27)

Budget Buildup
Superior Spectre Oval Car, Offset Pod, Back Pivot T-plate

The next few posts will be about this Spectre Chassis that I bought used. Eventually I will post a parts list to see what it cost to outfit one of these with medium price equipment. Where possible, I will list source and price for less expensive equipment that may do the same job for the club racer.

My goal in buying this chassis is to experiment with an offset pod car. This particular chassis had the benefit for me that it had a box full of spare parts. This included 10 of these very nice graphite T-plates. Because the T-plate is not required to flex much it should hold up fine however. I will have spares for my two woods Racing cars as well now. I also got the standard pod as well as several spare pods and chassis pieces.

Notice in the second pic that this is a fully pivoting T-plate; It has rear pivots the same as we use on the front of the T-plate. That means in bump the t-plate does not flex. The pod just pivots up on these balls. This should make the car behave much like a center pivot link car, except that the pivot is farther back giving exceptional antisquat. Corner exit forward grip is great as a result. This car is probably a Generation newer than the Woods car as it uses full graphite components in the newest parts, and has the benefit of the smooth associated pivots on the T-plate. I suspect this car will require less adjustment to keep the pod free of side to side play. One of the T-plates is equiped with a forward mounted side link to add rear steer in either direction.

Offset Pod
The third pic shows the offset pod. What you will find here is a short left hand hub, and a extra long right hand hub. The T-plate will be assymetrical, longer on the left, in order to fully clamp to the left offset pod. The T-Plate may also be offset in some of the newer cars giving you some left right adjustment settings. As you offset the pod left you tighten the rear (less oversteer). I would imagine the best rear traction is obtained when two identical rear tires are wearing equally. This would mean near equal loading while in the corner. You may, however, not need optimum rear traction as this might make the car push. This is the reason some guys are using right rear steer with an offset pod. The right rear steer will loosen the car.

Build
I used some liquid car polish and a 7 inch buffer on a drill motor to restore the shine to the chassis. If the can says polish, that means usually that there is some very fine abrasive in it to remove the oxidized paint. This worked well on the graphite without taking it down to the threads so to speak. Superglue residue needed to be scraped off. Double stick tape residue needed to be cleaned off with cigarette lighter fluid. It came out looking really nice. The first pic is the chassis after polishing it.

The rear of the T-plate needed a lot of attention before the pod would drop from gravity alone. I cleaned the pivots changed the screws and worked it around by hand fairly forcefully to center the parts. It finally freed up.

Parts so far.
IRS offset pod hubs and axle kit.
Acer Racing Carbide Diff Balls
RW 72 tooth spur, RW 28 tooth steel 48 pitch pinion
RC18T shocks with Windtunnel side springs.
Novak 13.5 EX motor with big bearing upgrade.
KO propo PDS 2413 ICS, This is a nice half height servo with good torque, strength and speed.
CRC red servo mounts
CRC based front suspension with Associated style kingpins and CRC Delrin steering arms
CRC Battle Axe front bumper, Foam bumper to come.
I will be running LiPo 13.5 with a Novak 4cell controller and Spektrum receiver.

Setup
The car is setup square now with rear width at 206 mm. 103 mm on the right and then the left side to match. Shock oil 35 weight.

Parts on order.
Traxxas BX shock for Center Shock

Superior Spectre:
Maker of the car
Ron Young. Westminster, CA

the Superior Spectre car used a PIVOT BALL rear end W/ a t-plate

Boomer

John,

I don't quite see the point of the T-Bar in this car since it looks like (from the pics) the rear pod pivots on its own balls and not using the T-Bar at all. . .

Could you maybe clarify a bit?

I've always thought that eliminating the T-Bar would be a wonderful thing. . .

SWTour

iTrader: (9)

boomer,

I ran a Superior car for a few years on the oval (Some of the stuff John has came from a guy I gave them to locally to get him started in oval racing a couple years ago I believe)

The T-Plate is still needed for side to side movement. The "FLOATING" rear pod is nice, and some of these were salvaged for racing on our VELODROME and been kept around (which is where some more of the stuff John has came from...) Thanks to my buddy ODIE.

There were 3 or 4 different versions of the Superior rear pod setup. One was a short "MONO BALL" tplate with a rod at the front to keep the pod straight...and allow for rear steer. (It was sweet, but you could knock the real alignment out easy in a crash.) That was my first 3 shock car...

When I switched from THIS type of car, I went to the HPI "Roadstar" 10Go, which is still one of my favorite cars for local short track oval racing...and it has NO t-plate, and has a full floating rear pod. I also have 2-3 On-Road versions of that car, one I plan to put back together to run in the World GT 200mm class. (It takes a 6 cell pack up the center and is LIPO ready)

John Stranahan

iTrader: (27)

Boomer-I postulated with the Woods racing car which has a similar rear pivot that the T-plate was not really needed any more and maybe this was the precursor to the center pivot side link car. In this Superior car the T-plate functions like the side links on a center pivot side link car and prevents pod twist or yaw. SWtour-thanks for your discussion as well. I appreciate the post. Gave!!! Damn, I paid $$$ for the car. Just kidding. Nice to know the history of the car. You will note on the second pic that second countersunk hole for the mini T-plate. The forward T-plate pivot is moved back to this hole.

Superior Spectre Electronics Install
One of the big factors in oval performance are the preloads that we give the car. We shift weight left. This reduces the load on the right side tires under cornering conditions and gives the tires on an axle increased efficiency or more cornering grip. I put the car with left side tires on a beam on a scale, right side tires on a beam on a scale. I have 13 ounces excess on the left side. My target was about 12 so this should be good.

On a pan car with any power it is helpful to preload the back tires to get more corner exit forward traction. I put the rear tires on a beam on a scale and the front tires on a beam on a scale. The rear is 7 ounces heavy. This is intentional. It will go up an ounce or two just from the weight of a center shock installed that is on the way.

I noticed that in his Cleveland World GT win on carpet that Tom had the batteries all the way forward on his Gen X 10's 6 cell tray. This shows that with good traction on 13.5/4 cell you might not need so much rear preload. On asphalt with a 13.5/ LiPo rearward weight is more helpful.

That 3 ounce lead ingot is cut from a 5 ounce fishing weight. The pattern is left by cold forging it a little more flat in the vise.

I put the bottom shot in to show some chassis mods. I moved the battery outboard of the frame. The little bumps on the bottom of this Orion case are only 3/8 inch wide or so. Their very square inner edge catches the side of the frame. I added the rear nerf bar behind the battery to hold the lead where I like to put ballast. This bar will catch an impact with the wall. I felt it was important to move this light battery closer to the body side. You can tape on added protection to the battery side if you like. As any T-bone strike is likely to be with the thin edge of a graphite bumper, I don't think this position is any riskier for it. That bumper would have no problem sliding above the frame and hitting a slightly more centered battery.
I have put a long graphite strap (from a crossplate knife) screwed to the frame on the inside of the battery. This lets me use two sideways strips of tape. I like this arrangement much better than a longways strip that often lets the battery escape the vehicle in a crash. New holes that were required are two large holes in the graphite bumper. Two drilled and countersunk holes on the battery strap, Two drilled and countersunk hole on my ballast shelf, two .089 holes inboard on the crossplate knife to mount the RC18T shock ballstuds which are threaded in. No nut on the left side for battery clearance..

Why RC18T rear shocks
Firstly they were in the box. Secondly the shafts are truly hard, they rarely bend, the shock is a bladder design so no internal air is needed. The pistons have holes for tuning. The hardware on the two ends of the shock rarely fail. I am almost afraid to thread on a ball cup to that little 4-40 aluminum spud coming out of normal pan car shocks for fear of snapping the little sucker off. They bend here, at the base of that stud, in a crash. The only drawback to the RC18T shocks are some tiny e-clips that you have to deal with. $18 a pair instead of $18 each in keeping with the budget build. CRC sells some nice dressup parts for these shocks including red bodies and yellow shock ends. I have a set coming for a second car.

Note the speed control and receiver are mounted to an 1/8 inch thick piece of G10 which is screwed to the frame. This give you clearance on the T-plate and a little more left side weight. Last pic shows temporary center shock. I set left down tweak to 12 ounces with both rear tires on scales, front tires on a beam. This means the left rear is 12 ounces heavier than the right. I tightened the right rear shock collar to accomplish this.
John

Boomer

Okay - just trying to get this fully figgered out in ma brain.

is the rear pod ONLY connected to the t-plate? That would make it all make sense, then.

The pics kinda look otherwise. . . it's why I'm puzzled.