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Old 05-31-2010, 12:09 PM   #1516
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Yes the track can get very dusty and dirty during the week, but it does clean up on race days.

On another note:
Having recently got my GM120 back from a software update I got to race it with a 1s 10.5 motor (Graupner).
Previous time with GM120 software 4.8 and Orion 10.5 was 17:308 (TR for 1s 10.5 was 17:300)
New time with GM120 software 8.0 and Graupner 10.5 is 19:316 (new 1s 10.5 TR)
My track record time with GM90 software 4.8 and 2s with Ballistic 17.5 is 20:310
(my 2s 13.5 is at 20:303 but is not officially recognised)
(overal track record for pan car is a 235mm 6t brushed 6cell car, and is 20:300)
(times set prior to 2003 was on old track layout, so do not count)
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Old 05-31-2010, 04:03 PM   #1517
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Thanks for the help John. I have no idea what I was doing before, but my ride height wasn't changing when I changed spacers. I think the suspension may still be a bit tight, as the car has only had about 3 packs through it!
I'm using the carbon spacers and shims to get it set and now i'm on 5.5mm with 1.5mm droop, which is where I want to start.
I have a friend bringing his new X-Ray X10 to the next meet. We will probably be the only Pan cars there, so we'll be trying to put on a good show and get a few more people interested
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Old 05-31-2010, 09:35 PM   #1518
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Thanks for the posts guys.
JR007-If the ride height does not respond to spacer changes make sure you have no contact with the outermost 4-40 screw that secures your spacer plates to the chassis especially if you have altered the wheelbase length.

NiMo how come some of your times are faster than the overall track record. Is there a short course.

Entering the Straight
I thought I would talk about this instability entering the straight. This is a trait shared by all the powerful pan cars I have driven. I can make an analogy to a powerful 2 wheel drive full size car that you are exiting the corner with. If you give it a bit too much throttle you can cause the rear end to start to drift out. You make corrections to steering and throttle to bring it back but it may swing back a bit too far and cause a wiggle, (the rear end oscillates left then right) that slows you down a bit. The Same thing happens on the powerful pan car. One thing that causes it is: the car is not aimed quite correctly when you start to apply throttle. This and the powerful motor causes the instability. A partial cure is to add side dams to the rear of the body. This gives the car aerodynamic stability and makes it tend to go straight. It reduces the wiggle. This is like adding fletching to an arrow or fins to a rocket, you move the center of aerodynamic pressure behind the center of mass, then the arrow or the rocket flies straight. You can also leave material behind the wheel of the pan car that is usually trimmed away. Another thing that helps is the passage of time and practice. Eventually you just aim the car correctly on corner exit and you can roll on throttle much sooner than before. Photo at left shows some huge side dams. I am weaned off them completely on my latest body shell.

Note that I sell a 2 lb/inch custom spring and a 1/lb per inch Gold Associated RC 18T spring for the JS Pro 10. If I had banking to deal with I would leave the rear at 3lb/in


Practice Session
I had a fairly rough car from recent changes to 2011 specs. The first pack I was running low 20 second laps and made a 19.6. But it was a solo good lap. I had a little too much steering in some corners. Motor temp was 176F indicating I was not quite hooked up.
I made only two changes. I had too much front droop. I reduced this to 1 mm. I added a little more antisquat basically trying to make the car behave like the previous version but with the new pieces.
It was perfect now. Steady mid 19's one 19.4. Motor temp was 196 F. The little antisquat change had hooked up the rear a little more on power. The top loaded battery setup had not spoiled the good chassis.
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CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-peugeot-905b-new-side-dams-resized.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-top-loaded-battery-001.jpg  
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Last edited by John Stranahan; 05-31-2010 at 10:23 PM.
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Old 06-01-2010, 07:03 AM   #1519
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Overal track record is 23:303, set with a 200mm IC 4wd with Lola type shell.
We have TR's for the different classes we run, including the 1/5th Bikes
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Old 06-01-2010, 01:53 PM   #1520
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Anyone have any thoughts or experience on the RC Devil 235mm car?

They do make some nice looking parts for various pancars aswell, including a cool looking carbon battery tray for the GenX10.
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Old 06-01-2010, 03:39 PM   #1521
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John, the new HMS bodyshell has quite large side dams already. I have also cut the rear section a lot lower like the one illustrated on your web page. I have found that it also adds some strength to the rear of the shell.




There is also the option of cutting the shell lower behind the rear wheel. Looks kind of ugly but may be fast.
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Old 06-01-2010, 05:04 PM   #1522
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Here is a discussion of the RC Devil. It is a Hatzenbach design that I have mentioned previously.

http://www.freemart.de/rcdevilshop/p...m-version.html

The pics at Red RC are the only good ones.



Note that full size GTP LMP cars do not cut out that valuable piece of body work behind the rear wheel. You leave it to improve directional stability.

John
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Old 06-01-2010, 06:15 PM   #1523
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Reading the above, I probably don't have the most aerodynamic body now! D'Oh

Oh well, it still look pretty.

Just got to finish the wing and get it on the track now
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CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-dsc00065.jpg  
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Old 06-02-2010, 08:17 PM   #1524
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Default Is any amount of tweak acceptable on the GenX?

Ok, so bought this GENX10 off of "Bag of Doritos" here and it's a basketcase. Needs a full teardown. Anyhow, I stripped it down to the chassis plate and noticed that it didnt lie flat on my setup board. Has about 1mm of play. Is this chassis trash? Or still usable? I was planning on using it for casual wgt racing around here on carpet. Nothing high speed yet.

Here's a short you tube video of it. You can see a little bit of side to side play from the shadows of light.

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
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Old 06-02-2010, 10:02 PM   #1525
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JR 007- Your body is fine for most motor packages. When you put in the 4.5 or 3.5 2s LiPo it may wiggle getting on the straight at first.

NiMo Thanks. I see that you are reporting laps now.


dynamic-e Any race car chassis will go slightly out of tweak with use. The one mm will probably be reduced or eliminated when you bolt the top plate and battery bottom plate up tight. Any remaining of that 1 mm will adjust out when you detweak the car before running it. A simple way is to lift the front of the car in the middle with the X-acto knife. Adjust rear side spring tension until the front tires lift at the same time. Equal front droop is needed before you do this step. Droop is how far the wheels drop when you lift the chassis. The space between the lower A-arm pivot and steering block while you hold the chassis up is equal to the droop.
John

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Old 06-08-2010, 08:19 PM   #1526
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Default 18t Shocks

John, I am designing a 4-link birdcage car for oval. That means the pod and the suspension is independent of each other. I was going to use either the micro VCS shock or the Mini-t one. After finding this thread I will probably use the 18T front shocks. What is the dimension of the shock @ full compression and extension? Also how much droop do you like in the rear end of your car? BTW after reading this I will probably put provisions for your front end.

Sean
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Old 06-08-2010, 10:25 PM   #1527
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Sean-
Those mini T shocks from pivot center to pivot center 1.80 inch at full extension, 1.40 compressed.
On my wide pan I like about 1.5 mm droop with the body on. With the body off there is little rear droop. This is due to the high speeds and bumps on the track. I use about 8 mm ride height on the chassis rear and 6mm on the pod plate. Because the pod and chassis are not hinged together you can run the pod and thus the heavy motor lower.

Good luck. Give us a pic when you have something put together.
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Old 06-09-2010, 08:56 AM   #1528
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Default 1/8 pan gearing

Hi John, I'm not trying to hi-jack this thread,but I have a gearing question. I'm rebuilding my 1/8 electric pan car. I asked in the "Will there ever be a 1/8 scale electric onroad car" thread, but didn't get a definitive answer. It will have a 4s2p saddle pack of A123 cells and a "L" size motor with a KV of 2500.All up weight should be about 4.5 lbs. Rear tire diameter is 65mm. I was thinking of gearing 3-4 to 1. It would need to be as fast as 1/8 gas road cars. (pics available in thread mentioned,post #2) Thanks, Don
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Old 06-09-2010, 09:49 AM   #1529
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Quote:
Originally Posted by John Stranahan View Post
Note that full size GTP LMP cars do not cut out that valuable piece of body work behind the rear wheel. You leave it to improve directional stability.
The bodywork of real LMP cars has to be "closed" because of regulations. "Closed" means: the wheels should not be visible.

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Old 06-09-2010, 09:50 AM   #1530
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Der Dickie-Maybe so, but they would still be closed to make that rear diffuser work. There is a vacuum that needs to be contained. (That panel also adds directional stability and reduces the ammount of side panel the wing requires.) Our cars develop a vaccum below the spoiler. I tested on a windtunnel a pan car with high cut rear panel as is the custom as well. I saw air entering this area from the back of the car. I am sure that cutting the rear up high is a custom that developed simply from "thinking" that air must be let out up there. I cut mine a little lower in back to block that incoming air.


DLS II
I'll start off by saying that operationally in the car this is a difficult problem I watched as Serpent attempted to do the same thing with their new 4 wheel drive 1/8 scale electric while they were visiting at my home track.

here are some basic calculations. this is your desired speed in inches/minute
65mi/h x 5280 feet/mi x 12 in/ft x 1h/60 min = 68640 in/min

Your tire circumference is 8.0 in

Divide the two gives a desired wheel RPM of 8580 RPM

multiply by a gear ratio of 3 and you get 25,740 RPM

Divide by your Kv and you get 10.3 V

this assumes you achieve 100% of your Kv. More likely is that you will achieve 80-90 % under load with an optimum gear.

So I suggest a 3s or 3s2p LIPO to get your volts up. That is what serpent was using. They still did not have sufficient gear on hand to achieve the high straight speed, although performance out of the corners was excellent. Do not try advancing timing. The motor fried two speed controls as a result. Anyway you can play with the math and your voltage to see what you might obtain with the 123 cells.
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Last edited by John Stranahan; 06-09-2010 at 12:15 PM.
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