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Old 08-14-2008, 10:08 PM   #241
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I made this post to the TC5 thread by mistake.

Oval tire test coming
I have a set of Purple/Double Pink rears mounted for a test now on the 200 mm oval car. I am in the habit of truing tires for the oval now. The only change I made to my truing rig is that I use a 3/4 inch router bit now in the toolpost grinder. This gives me more tip speed than the 1/4 inch bit and makes a smoother surface in one pass still. I am getting 4 plus races out of a set of trued tires. Starting diameter is 2.260 inch. Because of this I think I should throw on a new body. I can cut my arches considerably smaller now that they don't have to accomodate the large new tires. This should streamline things.

Full size Street/track cars
Most of the little tune up tips that I use and detail in this thread have a basis in full size car racing. I have had two full size street/strip cars. Adjustments to springs, roll center, sway bars all worked the same on my first 4 door "touring car" as they work on my electric TC and pan car. This first car was a 300 HP V8 powered Ford Falcon (same chasis as a Mustang) that would run 13's and would corner very well. It was lowered, had the front roll center lowered and had stiff springs and roll bars added, huge G series rear tires (355mm) under homemade flares and wide fronts. Extremely bulletproof drivetrain.
Here are a couple of pics of a more recent project of mine on a full size Ford Focus. This car is my second street/track car. It is lowered with stiff Ford Performance springs and Eibach antiroll bars, short light Motegi wheels and Falken Azeni tires for lowered gearing and great cornering bite. It will go 130mph. I had it in a fourwheel drift on a 120 mph corner recently. It pulls 1.0 g's in the corners. It has a completely neutral oversteer/understeer balance which makes it easy to take it to the limit in the corners. Use ProSolo (autocross).
A new project, detailed in a thread, is the addition of quad Individual Throttle Bodies (ITB's) to the four cylinder dual overhead cam Mazda based engine which comes equiped with a single throttle body. Mid range and top end may be improved. These throttle bodies originated from a Suzuki GSX R 750 Motorcycle. The project includes a HOMADE ABS plastic intake Manifold!

Practice day tomorrow. Race Sunday. Then I will have more pan car stuff to discuss.

Pic: We are looking at the bottom inside of the ITB assembly. The white manifold is ready to bolt on to the front of the engine. The airbox needs to be completed. The copper pipes are for EGR inlet. Factory Fuel Injectors are in the head. I have software to increase their pressure and the slope of the fuel curve. The factory computer and an after market Mass Air Flow (MAF) Sensor will be used. Last pic top view, Strap needs paint.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-assembly-near-completion-002.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-motegi-wheel-001-resized.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-air-box-top-bracket.jpg  

Last edited by John Stranahan; 08-19-2008 at 02:40 PM.
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Old 08-15-2008, 05:49 PM   #242
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BSR Double Pink/Purple

In the never ending quest for oval of reducing tire scrub, I tried the above tires. I have been running GRP Magenta (35) which are very close to Double Pink (36) in hardness. These double Pink/purple tires have the outer part of the tire purple (40) and then the inner double pink.
The track was cleaned and freshly prepped. Traction was medium by intent. On the first few laps I had too much steering with two pink (30) fronts (in the previous race I had reduced this by running a double pink right front. I think two pink front have more potential after studiying the race lap times) I was able to dial the front in by reducing dual rate with the two pinks. Now the car went around the corner in a slight drift with the rear angling out. Gradually as I learned to use less steering throw this went away. I had sufficient forward traction coming out of the corner. I could use huge throttle there. I was able to start throttle roll on mid corner without the rear letting go. I was pleased. Now all I need is some lap times to prove them. Race Sunday. Maybe a touch more wing would help.
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Old 08-15-2008, 05:59 PM   #243
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Very cool project john!! Here is the project im working on right now. Its gonna take me a while to complete but its coming along nice so far. So far i got the wheels and tires, Ram Air Induction, Computer tune and a few little cosmetic pieces. I am making up a list of upgrades i am going to do but will be waiting a few months to get started again. So far i have her running mid to high 12's at the strip. Not bad but could be better.
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CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-vette-pic-1.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-new-vette-pic.jpg  
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Old 08-18-2008, 11:05 AM   #244
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Jason-Nice ride! Good luck with your project.

Tire Report Oval, World GT
I did a test of a series of back tires. Here are the Hardness and then average lap for the fastest 20 laps in that heat of the race. The results are pretty clear. All else was unchaged except in the main I made a hub change to reduce some wobble and lost a little left rear offset. Front tires were the same set of GRP pinks.

BSR Purple/doublepink 4.729 s
GRP Magenta 4.753 s
RC4 less Pink 4.834 s
RC4 less Pink 4.856 s

I did these test somewhat blind as the time sheets were not brought down until after the race. My only clue was the relative speed with Hermans car who won the race. I came in second. I should have run the purple double pink in the main. The trend is clear with the harder tires turning in better laps.

I continue to have problems with the left tire wobbling. Since they are true coming off the lathe the problem is likely in the hub or axle. I measured the axle. It is .001 uncersize compared to my wide pan axle. This causes the hub to clamp at an angle. I ordered a new axle and hub to see if this would correct the problem. It is bad enough to look like I had a bad crash on that side. The right side is centered by a radial bearing and runs perfectly true.

I wonder if what we need is a collet left hub that clamps radially and applies presure to collet fingers with an inner and outer taper, when you tighten a nut on the inside.

John
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Old 08-18-2008, 04:29 PM   #245
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that sounds actually like a good idea, John. You would need a larger opening on the hub so you could use some sort of collet or shim system. . .
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Old 08-18-2008, 08:11 PM   #246
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Riemen made a 1/12th collet hub for 1/12th axles. I did some testing with it and it did work pretty well but it was a real pain to get clamped. I think it could have been made a little different to make it easier to use. I may still have it if you want to play around with it.
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Old 08-18-2008, 08:29 PM   #247
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Jason
yes please send that puppy over here. Maybe I can adapt it. It might need some teflon or something to aid clamping. The Dewalt zip tool has a beautiful 1/4 inch collet finger with tapers on both sides and eight longitudinal slits.
John Stranahan, 4139 De Leon St, Houston, Texas, 77087.

Note we are talking about a part that would hold the axle like the standard Dremel Chuck holds onto a 1/8 shaft; this part only clamps on one end. The Dewalt part clamps on both ends.

Pic is of the Dewalt Cutout Tool Collet. It is a four fingered design that works extremely well. It produces a very concentric clamping action. A nut forces the device between two tapers to clamp a shaft in place.
John
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CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-dewalt-four-fingered-collet-002.jpg  

Last edited by John Stranahan; 08-18-2008 at 09:40 PM.
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Old 08-21-2008, 12:13 PM   #248
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John

What are your views on balancing a car, Jason said in another forum that he balances his cars with the pod detached, which makes sense due to the heavy pod weight. Is there a weight distribution we should be looking for? When I used to race stock cars this was one of the most critical items, maybe more than tires, pressures spring rates and shock dampening. It was also a bit of a tuning thing to run your weight up or down on the cage to enhance or decrease the roll(dirt track). If a person was to weight out their pan car, what should they see as the weight dist. or should they just get left to right correct and use springs and tires to tune. I myself race 10 and 12 scale pans on carpet roadcourses Great thread by the way.
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Old 08-21-2008, 08:05 PM   #249
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Cammer-Thanks.
On weight distribution
I don't detach the pod.
I do this one time on building then just make slight adjustments as needed without reweighing. Some good numbers to shoot for on flat asphalt is a 9 ounce excess on the left and a 9 ounce excess on the back. This is where my car is now as opposed to numbers I have heard. I use two beams and two scales. Set the left tires on one beam, the right tires on the other beam, each beam on a scale. Note I run about 10 mm left rear wheel offset which makes the wheel farther from the car. This reduces the left side reading on a scale. (body is then centered with offset in place). It was more like 12 ounces without this offset. This spacer reduces to nothing corner exit hooking and makes the car easy to drive even when slick with dust.

More discussion and pics in this thread here.

Move weight until there is 9 ounces more on the left scale than the right.

Do the same front to back. About 9 ounces more in the back.

Now you have to set the wedge or left down tweak. On a 3 shock pod you will tighten the right rear shock collar. This will add load to the left rear tire and take away load from the right rear. This adjustment is extremely helpful in getting rid of corner exit hooking and oversteer in general.

More discussion in this thread here and a method to use scales. I am shooting for about 10-11 ounces of left rear downtweak last I ran the battle axe. This is excess weight on the left rear compared to the right rear. On my custom 3-link car I can get by with considerably less left down tweak. I temporarily added a third shock to my 3-link car to easily dial down tweak in but it was not helpful and just added more weight. The stock rear pan car suspension definitely profits from considerable left down tweak.
Tighten the collar more to add understeer mid corner. At the same time this reduces corner exit hooking. Make this adjustment after a test drive on the track every race day. No need for scales except to share the information.
John

Last edited by John Stranahan; 08-31-2008 at 10:04 PM.
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Old 08-21-2008, 08:30 PM   #250
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History of left rear wheel wobble.
At first I was using little left rear wheel offset. I trimmed the axle to the end of the bearing surface of the hub and used a lightweight KSG hub.
I increased offset to 10mm. Now the axle was a little less than flush in the hub.
Probably from normal wear and being a bit too short the axle OD wore down about .001 inch.
A new axle and standard 3/4 inch hub provided increased axle diameter and full bearing on the hub. Runnout is now very low again.

you might notice this problem when you put on a freshly trued tire on and it wobbles at low speed when you run the motor, car in your hand.

Left rear wheel offset
Quite a few racers at our track including some running the days fast lap have tried this little trick to reduce corner exit hooking. I won't call this oversteer as what happens is the front end darts to the inside board. You fix part of this with left down tweak and maybe some left rear wheel offset. The offset causes a clockwise (when viewed from above) torque steer and cancels the natural torque steer that loaded right rear is making on corner exit. The question is how much. Well one guy quit about 1/8 inch. He was continuously plagued with the problem and had many spins in the main. I just kept adding till the problem went away. I ended up with about .450 inch. In the main a hub change lost about 1/8 inch of offset and I had one early partial spin as a result.

It is not self serving to not make an adjustment that may cost you .003 seconds a lap in increased airfriction and then have one spin that costs you 1/2 a lap or 2 seconds as a result of not making the needed adjustment. There is no width limit to our cars except maybe out to 250 mm (9.875 inch).
John

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Old 08-24-2008, 05:50 PM   #251
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More Tire Tests 200 mm pan 13.5 4 cell

It seems, on the oval at least, that the 13.5, 4 cell powered car is fastest when you have found the hardest front and rear tires that you can live with. This means you can complete the race without a big tire related spinout or push to the wall.

This weekend I had two session on GRP front purple tires and BSR XXPink/purple rear tires. Note that I use purple fronts routinely on my wide on road pan, but I have been using soft fronts on the oval. Saturday I put on 4 lbs of sugar and had a clean track. The tires were well hooked up after maybe about 5 laps. During this 5 laps I increased steering throw with the dual rate wheel and let them scrub in from a fresh tire truing cut down to 2.260 inch. I ran two pretty full packs which is at least 30 minutes of track time.
Today I measured about .015 inch of average tire wear on those hard fronts. My right front only .010 more worn than the left. That's about 6 heats worth of runtime. I rotated tires today. I applied 2 lbs more sugar as there was a light shower over night and normal dust that accumulates over night. It took about 15 laps for the fronts to "scrub in". What is happening here is the tire is wearing down to a full contact patch (from a fresh rotation) and getting smooth (don't rotate before the main). Another thing that I think was happening is dust that accumulated needed to be scrubbed off the track by the passing of the car. This is not needed on the front XXpinks; they hook up right away as do pink fronts. Now once I scrubbed in I got some sparring partners (really the whole race crew today) and the tire combination just slaughtered the opposition on practice packs. This was evident in a second run, but again, I was slow for about 10 laps. So the thing to do might be to run those 10 laps in practice which is easily possible. That is less than about 1 minute of prerace practice. I think this 10 laps on non rotated tires is just cleaning accumulated dust off the track that collects between heats.

I worked on my oval line. Our drivers stand really overlooks one end of the track on the side. I have trouble with this near corner as it is out of the eyes view when I start the corner. I thought a little stripe or something on the white painted outer perimeter might help. Kind of like the feet distance signs on a full size race track to aid in finding the right braking point for corner entry. We don't brake, but it is helpful really, to run a semi diamond shaped line on a short asphalt course. Start a gradual turn near the middle of the straight. This is exactly what the carpet nats videos showed. They had a nice black line in the carpet to follow. I put a white piece of flapper material flat on the track which worked well unless some guys that drove from ground level for practice obscured it.
John

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Old 08-31-2008, 03:56 PM   #252
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John, where can I find an oval kit?
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Old 08-31-2008, 05:56 PM   #253
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bigB11- Battle Axe from teamCRC.com I don't know if they are in good numbers yet. It is still pretty new.

Others that are popular at our track

RC10L4 from Associated. They may be discontinuing this model so numbers may be low.

Hyperdrive or Custom Works from LeftHander-RC.com or RC4less.com. These are the type with a large number of adjustments. Also check the very first post in this thread. There are other suppliers listed you can check.

http://www.teamirsrc.com/ IRS model shockwave

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Old 08-31-2008, 05:57 PM   #254
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Quote:
Originally Posted by bigb11 View Post
John, where can I find an oval kit?
Best car I've seen. Support is GREAT!!!!!!!!

http://www.teamirsrc.com/shockwave.html

I owned the Battle Axe that that John wrote about in this thread and received no support from CRC, I can tell you, you will love the IRS car and any of the drivers to the owner will help you in anyway possible.

The car lists on IRS's website for $419.00 but you can get it cheaper at Windtunnel http://www.windtunnelracingproducts....oducts_id=1188 for $375.00.

There is no hop ups for this car because they come with the car kit. If you have more questions send me a PM and I will try to help answer any questions if I can.

Rick
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Old 08-31-2008, 06:03 PM   #255
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Quote:
Originally Posted by lidebt2 View Post
Best car I've seen. Support is GREAT!!!!!!!!

http://www.teamirsrc.com/shockwave.html

I owned the Battle Axe that that John wrote about in this thread and received no support from CRC, I can tell you, you will love the IRS car and any of the drivers to the owner will help you in anyway possible.

The car lists on IRS's website for $419.00 but you can get it cheaper at Windtunnel http://www.windtunnelracingproducts....oducts_id=1188 for $375.00.

There is no hop ups for this car because they come with the car kit. If you have more questions send me a PM and I will try to help answer any questions if I can.

Rick
I can vouch for Rick loving the IRS car because he had me paint IRS on the hood of his oval bodies.
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