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Old 01-15-2008, 10:08 AM   #1846
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I've looked and felt at the low roll centre Hatzenbach/Ascari Cars.
They set it up with really stiff side springs.
In my opinion they lock the rear up so much that all traction comes from the tires anyhow, not any roll centre effect.

This kind of 10th pancar setup is typical for the most Germans I run against anyhow, since most of these drivers normally run 12th scale on high-grip carpet, where you need a firm setup.
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Old 01-15-2008, 12:55 PM   #1847
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JeV-That Futaba servo is discontinued. I agree that that KO 2413 would be a better choice as it has a steel output shaft. I did not happen accross it when ordering. Anyway I will give this one a try. By happenstance, it is offset very much to the right. This gives me good clearance to slide in my chubby battery infrom the left side.

Tell me about cog. Is this motor cog?

Mathijs- You talk of the rear being locked up. I noticed that there were four links controlling the roll center. Almost like a vertical version of the fourlinks I tried on the pan car. I suspected this would tend to lock up the suspension from the bars attempts to flex the chassis as lengths did not change to aid movement. A 3-link design was needed on my car.

Real Roll Centers
I have discussed this with a part time designer like myself by e-mail. My design has a Panhard Bar. The roll center should be at the center of the Panhard bar. The bar is easily adjustable. Although it will not go below the ground, it will get very close. The Pan car is not sensitive to changes of this Panhard bars height. I ended up running it at chassis height for good ground clearance. I still have a suspicion that the pod is so big and heavy that it should almost be considered a separate car attached to a front car with linkage. If the rear pod had body mounts this would even be more evident. The rear roll center is probably centered on the axle like in a full size car with solid rear axle and leaf springs. I think the benefit to shoot for is antisquat. This has been hugely favorable with this rear end. It increases both rear traction and steering into the corner.

I second the vote for hydraulic front damping. I have put those little RC18T shocks on my touring car as well. I dropped an ounce and they have not leaked for 4 months. I admit the rear and front of my pan car pounds them a little more than the Touring car and they require a rebuild a little more often.

Thanks for the posts.
John
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Old 01-15-2008, 02:06 PM   #1848
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I think by cog he meant Centre Of Gravity.
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Old 01-15-2008, 02:07 PM   #1849
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I believe the Futaba 9551 is intended to replace the 9550. Tower lists a case and gear set for the 9551, but no servo yet.

Those FMA lipos are incredible. I really hope Saehan Enertech makes a shorter cell for the R/C market, because I want one right now.

John, did you see that Corally have released a new 1/10 pan car? It appears to be based on their 12x.
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Old 01-15-2008, 09:34 PM   #1850
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"I know you fit the esc high so that will give you extra roll, but that also increases cog. Is it not better to keep cog as low as physicaly possible but raise the roll center of the susupension?"


JevUK-I agree with this for the most part. One thing that roll does however, is it delays weight transfer at the start of the corner untill full roll is achieved. This improves cornering early in the corner. If traction is lacking I don't think it matters whether you have weight up higher or use softer springs and roll bars. The end result is similar.

When traction is at a max my tactics change. I started having a problem with traction roll on the touring car. The first thing I did was move that speed control down. It mattered now. Then I added heavy sway bars.

On my wide pan, I have not been any where near traction roll. For the most part it acts very stiff because of the heavy front springs we need to run. The speed control up high made the car more supple and easy to drive. Weight transfer is delayed. The car was not so twitchy. The mcAllister Nissan 300 Z GT body helped even more in this regard. I have a new one ordered up for my all time lap record assault. Pic below.

Syndrome thanks for the servo info. I am glad to fit that nice high capacity battery in the pan. I am excited about its next test. It should be ballistic!

I have been following the 1/10th pan thread on the new corrally. I'll take another look at it.
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-mcallister-stock-car-002-resized.jpg  
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Old 01-16-2008, 11:51 AM   #1851
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Yeah cog=center of gravity

cog and roll center are spereate variable that need to be balanced to create the best handling. And then you have the spring and roll bars, damping anti squat etc

Ride hight has a massive affect on cog

The way I see how roll should be used is to smooth out lateral forces throughout the turn.

I think the reason we don't need springs on the side dampers is because the roll center is too low.

Foam tyres seem to cope much better when they break traction so the lack of roll does not mean total breakaway. More forgiving.

Remeber the center of gravity on the pan car is already much lower than the touring car. Then the roll center is lower too. And then you may have harder springs as well.

I find it an interesting topic to discuse but admit I do lose patentience when doing testing .

If a pan car was designed with adjustable roll center I can see it as a very usefull tuning tool.

When ride hight is alterate then roll center should be altered to compensate to give the same rate of roll?

Wikipedia is better to understand these things than me

http://en.wikipedia.org/wiki/Roll_center

Quote:
The significance of the roll center can only be appreciated when the vehicles center of mass is also considered. If there is a difference between the position of the center of mass and the roll center a “moment arm” is created. When the vehicle experiences angular acceleration due to cornering the size of the moment arm, combined with the stiffness of the springs and anti-roll bars (anti-sway bars in some parts of the world) dictate how much the vehicle will roll while cornering. This has other effects too such as dynamic load transfer.
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Old 01-16-2008, 12:14 PM   #1852
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Quote:
Originally Posted by syndr0me View Post
I believe the Futaba 9551 is intended to replace the 9550. Tower lists a case and gear set for the 9551, but no servo yet.
Might explain why I just got a s9550 for £40 inc postage from HK.

Looks like the replacement is similair speed but a lot more torque.

I've got 1 S9550 and 1 PDS-2413 and they are both great so the futaba wins on price imho.

S9550
Torque (6.0V): 83 oz/in. (6.0kg.cm)
Speed: .11 sec/60° @ 6V
Weight: 1.6oz (45g)

S9551
Torque @ 6.0V: 136 oz-in
Speed @ 6.0V: .12 sec/60°
Weight: 1.6 oz (45 g)

KO PDS-2413
Torque: 118 oz-in (8.5Kg-cm)
Speed: 0.10 sec @ 60deg
Weight : 44.8g
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Old 01-22-2008, 05:53 PM   #1853
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JevUK-Thanks for the posts.

Here is a pic of the recent McAllisterracing.com Nissan 300z. He threw in some Nissan decals this time. I am running it loosely according to the wide pan GT class rules. This allows me to place a wing at the rear that the original race car also used. This is probably not the best wing but it should work OK. I like the wing better than a spoiler extension (flat plate right on the rear of the rear deck) on this body because I can move the wing forward and back. A little forward of the rear provides a little more front stability on the straight and prevents blowovers. We had an 1/8 scale blow over this last weekend so this is still a concern. I am waiting on the return of electronics from Associated. I will run the LRP TC edition speed control and the X11 3.5 motor. I was qualified 3 of 11, 1/10 Nitro touring cars last weekend in the electric TC and 3 rd of 8, 1/8 th scale open mod cars. I hope to improve on this with the wide pan. A sugar water treated track will help.

This is the only GT body available at the moment. I think the car corners better with this body. Current state of the chassis in pic 2 with LRP TC edition.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-nissan-300z-red-001.jpg   Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-wide-pan-lrp-tc2.jpg  

Last edited by John Stranahan; 01-22-2008 at 09:18 PM.
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Old 01-24-2008, 11:26 PM   #1854
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3-link Wide Pan car rear suspension Video

I was asked to do this a while back,but I did not have the neccesary digital video camera. Now I do. The poster wanted a video of my custom home designed and built 3 link suspension getting a workout on the bench to see how it actually moved. Note this is the same suspension used on the current Mustang GT rear suspension.

The .wmv movie file is only a few minutes long and is about 10 MByte in size. About 3 times bigger than my one lap videos I posted previously in this thread. I have located the file in two places. The first is the raw file and should give you a good quality full screen view if you hit the correct buttons on your viewer.

Note that when looking at the right side of the chassis for pod movement, the view in the reflection on the glass table top gives you a good view of the pod movement.

http://hometown.aol.com/johnstranahan/3-LinkSuspensionDemo.wmv

I have also placed this video in my Machining Journal where the actual machining of some of the parts are described.

http://journals.aol.com/johnstranahanb/RebarrelingandHome-ShopMachining/#Entry1636

This link will take you to the proper entry in the Journal and then a smaller faster download will result using the Journals fixed viewer.

Negative Camber Gain
I have also included a short clip of the negative camber gain with roll of the front tire. This setting, arrived at experimentally, gave me the best front steering traction.

Anyway this is for Posterity. Maybe one day a manufacturer will try it.
Advantages are
No blowovers at track speeds on a bumpy straight.
10% more speed and traction through a bumpy straight.
5% better lap times than standard designs. 1 second is a lot on a 20 second lap.
much fewer spinouts due to better rear traction.
Faster corner exit from generous antisquat.

That ratty long front bumper is just an experiment.
John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-front-view-jspro-10-001.jpg  

Last edited by John Stranahan; 01-24-2008 at 11:43 PM.
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Old 01-25-2008, 12:02 AM   #1855
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nevermind
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Old 01-25-2008, 05:12 AM   #1856
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Hi John, I like the video. Chassis is pronunounced shassis though

Did you look into mounting the panhard bar in front of the motor or is there just not enough space? I guess the lower the bar is, the higher the roll center?
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Old 01-25-2008, 11:05 AM   #1857
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There is no space in front of the motor for a Panhard bar with this battery or a standard size 2s1p LiPo. The advantage at the rear is that the bar can be made very long. In Theory this minimizes the change in roll center when turning left vs turning right. As you can see in the video turning right lowers the panhard bar a bit compared to turning left. In theory also the roll center of the back of the car is at the center of the Panhard Bar. If you lower the Panhard Bar you should lower the roll center. In practice the car is fairly insensitive to Panhard bar height. I have also noticed that the center pivot link cars are fairly insensitive to low roll center kits. I do note that Mathijs reported a benefit from lowering the T-bar on a wide pan.

I found on our track the wide pan cars perform the best at about 43 ounces which is where this car came out. At 39 ounces they have trouble developing bite. Heavier they handle like a pig.
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Old 01-25-2008, 04:15 PM   #1858
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i have been trying to run my car with a core lipo, but it is so light it is a handful.. comes in at 34oz...
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Old 01-25-2008, 04:20 PM   #1859
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TallyRC-Thanks for the post. Did you find any pan car racing in Florida?
I found a benefit to adding a second LiPo in parallel when the car was very light. Forward traction improved a lot. Cornering was not hurt too much as long as the car did not get too heavy. 3 ounces of lead might help as well. This dead weight does not help quite as much but it may help forward traction.
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Old 01-25-2008, 09:31 PM   #1860
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there are a few others running pan cars but i have yet to catch up with them as racing has been back burnered due to an unrelenting work schedule.. i imaging the pan cars with pick up further when BMI's 10th scale is released as they are based in Tampa and travel the state often and are well represented.. i have now switched to entirely lipo and brushless so some lead weights are in my future unless i can find some tungsten that is...
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