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Old 01-26-2008, 01:39 AM   #1861
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Originally Posted by John Stranahan View Post
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.

I found lowering the Tbar's pivots yields more rear stability.
I use this as a tuning aid, but only if all else fails.

39 ounces (1100 gram) is indeed a bit light.
At that weight a car is not legal for racing here.
We have a 1200 gram limit.
At 1230 gram my car handles great.
However, with some setup tuning you should get your car to handle at anu weight though - just a matter of balance.
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Old 01-26-2008, 09:06 AM   #1862
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The problem of the light car was not balance. It was perfectly balanced. It was grip. The foam tire just would not get through the light dirt that is always on a track and grip the asphalt. A second light LiPo battery on board made the car faster.
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Old 01-26-2008, 02:58 PM   #1863
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The problem of the light car was not balance. It was perfectly balanced. It was grip. The foam tire just would not get through the light dirt that is always on a track and grip the asphalt. A second light LiPo battery on board made the car faster.
John
A solution to that is run narrower tires, like rally cars do.

I found the super soft corally silverstars still worked great with a lighter car.

Don't forget a lighter car needs softer springs/damping.
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Old 01-26-2008, 05:02 PM   #1864
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A narrower tire may have helped. Tally's car is really light, he could try that with an old set.

Springing on a standard pan car goes like this. You spring the back pretty light then you add spring rate to the front until it corners in a neutral posture. There is no real way to get below this. The rear is going to be light the front is going to be stiff.

Standard pan cars have one center rear shock. (or maybe three with two side shocks) I did not note any traction advantages to changing the damping on the center shock. (You are going to have the side shocks pretty light already.) I mainly selected a center shock oil that would keep the chassis off the ground or lighter if the car was bouncy over the bumps. In theory you get a little less steering traction if you go lighter. No way to affect front and back at the same time.

I know that as a general rule say on my touring car both of these latter items would help overall traction. My pan car design can also be adjusted this way, but it is at a heavier weight that is grippy so it is not necessary to change it. It is at the lightest spring rate that will keep the back of the chassis from wearing on the track, though. Those rear springs on my pan are 3.5 lb/in. The fronts are effectively 35 lbs/in as they have been shortened.

I should get a new run on the car tomorrow. We prepped the track today but it was a little wet from Fridays rain to practice.
John
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Old 01-27-2008, 01:55 AM   #1865
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I have to disagree on the Tbar pancar setup with you John.
For example:
Yesterday I ran at my home track. The track was dusty, and it was really cold (about 7 degrees celcius) and very windy.

I started with 35wt oil in the centershock and a silver (firm) spring, with 0.022" front springs.

I found I was lacking traction - no surpise.

I first changed my center shock - first a green (medium) spring, than 25wt oil.
The rear was locked-in now.
However, now my car was pushing.
I simply swapped front springs to 0.020" and my car was in business.

This is simply how old-style pancars cope with slippery conditions.
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Old 01-28-2008, 08:51 PM   #1866
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Thanks Pro 10. I see we get slightly different results based on track smoothness. I can go no weaker usually on the center shock without wearing away the edge of the pod on a standard type center pivot link pan car. This is less of a problem on the T-plate car.


CRC's GenX Pro 10
Now here is some good pan car news. This thread has probably helped the situation. 5 companies will now be producing 1/10 pan cars in the US. The first page of the thread already has links to the Darkforce model, Hyperdrive, and team Speed Merchant model. CRC and BMI bring new cars to the field.

The CRC Pantoura is being discontinued but will now be replaced with a 200 mm pan car using generation 3 parts at CRC. The Gen X-10. It has an especially nice system for brick type encased LiPo’s. They will sell a kit to enlarge it to 235 mm. I you are outside on a big track this is the way to go. Of the three companies this is the only one I heard that will be 235 mm capable. Here is a quote from the CRC team.

“The Gen-X 10 also features our Pro-Strut front end, easily adjustable, easy to build and very durable. The Pro Strut is mounted on an adjustable front end plate that allows the user to change the wheel base of the car and width of the front end. Of course the Pro-Strut allows the use of trailing or inline axle applications without extra parts. In addition, CRC will offer a 235 mm kit for those looking to replicate the old “wide” cars.”

There is a separate thread on this CRC GenX Pro 10 car now. There are some good reduced sized photos in that thread now. As usual my thread will not be a substitute or compete directly with that thread. We provide the so called “color”.

Of the available designs that I have tried, I prefer this center pivot Link GenX Pro 10. It gives me beter rear traction.

new readers see page 1 of this thread for a list of pan car suppliers for bodies, parts and cars. Page 1-7 for the new car experience.

John

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Old 01-29-2008, 02:26 AM   #1867
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John, I like your suspension travel video, thanks. May be you can do some experimental with all round fully independent suspension. The satisfaction from RWD rc car totally next level to me. I mean higher.
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Old 01-29-2008, 02:26 AM   #1868
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John, I like your suspension travel video, thanks. May be you can do some experimental with all round fully independent suspension. The satisfaction from RWD rc car totally next level to me. I mean higher.
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Old 01-29-2008, 11:08 AM   #1869
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UFshadow-Thanks. I think if my car became independent rear it would be .5 seconds slower from extra driveline friction. Outdrives turning drive axles, axle U-joints, axle imbalance. This would also put the car in a non pan car category. As it is now the car can meet all the wide pan rules as they exist now.
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Old 01-30-2008, 04:34 AM   #1870
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John, seem that you are really master with what you said. No doubt that efficiency of fix axle system is higher. Just compare no. of ball bearing required for drive train.....8 > 2 for pancar....

But the good thing about independent such as very low unspring weight, rear toe in and others setting associated with independent suspension can contribute to more stability at the tight section and high speed especially for asphalt track.

Anyway, no class for it...it just my dream car.
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Old 02-02-2008, 04:53 PM   #1871
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UFShadow- I am not convinced yet that rear toe and camber are essential for the fastest lap times on an Electric RC car. There are gains in stability but losses in terms of road friction. I think with independent rear (ala a touring car) the car would be easier to drive than a pan but not quite as fast. I am still conducting those wars independent suspension (TC) vs wide pan. I have my custom wide pan with CRC chassis up an running again today.

I ran a couple of tests. I ran the Novak 3.5 motor with the fat tuning rotor geared 13/90, 2.4 inch tires. This was really not the ticket for the poor traction I had. It felt like a Novak 4.5 and would shock the rear tires loose from forward grip too often. I changed to the small rotor and geared 12/90 and I was in better control of forward traction.

My body needed a lot more rear wing. The car would go tail out and oscillate on the two high speed turns as I corrected with steering. A touring car wing set low is not enough. I changed to a 2 inch spoiler for the next test. The wide pan definitely steered harder on my two hairpins than the electric touring car.

You loose a lot of trigger control driving a touring car for a few months. You become a trigger masher. By the third pack I had some of this skill back but I needed more forward traction. We are experimenting with the sugar spray. If it goes on in a fine mist and is hot we seem to get the best traction from the additive. Today was not one of those days. (Rubber tires are hooked up great and are .5 seconds faster on the electric touring car.)

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Old 02-03-2008, 07:42 PM   #1872
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Default 200 mm pan car

Custom 3-Link, 200 mm, pan car with Panhard bar

Well here is the situation. Our carpet track has been under construction for a year. It will have air conditioning, a nice hung ceiling, paint etc. Pretty deluxe. This explains the delay. My spy told me it might be a tri-oval like some Nascar tracks (an oval with three turns) and run Nascar bodies on 1/10 scale pan cars. Well that's pretty exciting to hear.

I had this 200 mm pan car in a box, so I thought I would make some changes based on best knowlege now and try it out again. There are pictures of it previously in the thread but much has changed. I may add a new chassis later on to add some stiffness. The rear is cutout a little too much.

Posters have asked, nay clamored, for a Panhard bar in front of the motor. This is where it is now. I have a suspicion the roll center of all pods are middle of the rear axle. That's about where I put the bar. It may not have the theoretical disadvantage of being high (giving a high roll center) on a pan. I have a slight tilt to it which I found on the wide car prevented axle tramp on hard brakes. Not likely on the oval. The bar is above the battery so maybe I can use my long batteries with a short servo.

A second major change is the rear upper shock mount that you can see from the rear view. I needed the shocks to grow down from the center of the shock arms. I accomplished this with a glued on thickness of graphite plate followed by drilling and tapping the holes 2.5 mm. I also glued the ball stud in. I have good luck with this glue up on my TC5 which has these same RC18 Ball studs glued in. They never pull out unless the arm breaks.

A third change is that I have made the top link longer. This reduces the rotation of the pod with bump.

There is no rubbing now. I had just a little tire contact with the shock arms previously. When you drive a 235 mm car it is hard to go back to the narrow car so I did not pursue it much. Marty at MLP had done a CAD and was pursuing a version of this 200 mm car. No car was produced so I thought I would advance the prototype.

The several new 200 mm cars which, by conspiracy, will be little changed from previous pan cars are suggested to run with rather lesser power trains than we have been discussing. I will follow suit on the 200 mm car.

The main advantage of this design will be generous antisquat for better corner exit speed and much quicker return to ground of a tire that has gone up in bump. Tuning will be simple.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-front-quarter-view-200mm-pan-002.jpg   Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-back-view-200mm-pan-001.jpg  

Last edited by John Stranahan; 02-04-2008 at 10:15 AM.
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Old 02-03-2008, 09:48 PM   #1873
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Antisquat
I posted a picture sequence earlier on the effects of antisquat. That is one of the major benefits of the 3-link suspension. Here is a short video clip, less than 1 MB. showing the effect on the 200 mm pan car in the new post above.

http://hometown.aol.com/johnstranahan/AntisquatDemo.wmv

You can clearly see the rear of the chassis rise and then when uptravel is used up the front of the chassis will lift. When the rear of the chassis rises, even if only a little bit, it adds a good size dynamic load in the opposite direction, downward on the rear tires. I have a roll of tape on the front to mimic a load from servo body and wheels on the front.

My Nephew experienced this directly At MTI technical school on a full size T-bucket roadster with a 350 Cheverolet engine. Doing burnouts in the parking lot, the passenger seat which is only a little in front of the rear axle rises with the chassis. You can feel this. You can see the same action on the full size dyno as the chassis lifts with power.

Note that antisquat on an independent rear RC suspension works differently. It causes the suspension to become stiff and results in oversteer. Not so on the solid rear axle pan.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-antisquat-setup-002.jpg  

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Old 02-04-2008, 03:18 PM   #1874
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Here is a picture of the flat oval car with a mockup of the electronics. I am able to slide the battery left and right to tune. Now I will tell you I have no experience with asymmetrical oval cars. I did run some dirt oval in a buggy and truck. So here is the question. Our oval will be flat maybe 85x75 ft. There will be three turns. If you run some flat oval on carpet with a 1/10 scale pan give me an idea of how much preload you would put on the left side to start with in percents or just raw corner weights.

Preloading the chassis
I thought I would discuss this a bit as I have not had a reason to previously in this thread. I'll asume the foam tires on carpet behave very similar to rubber tires on asphalt as I notice the same tricks are used to optimize lap time on both. I realize that traction will be higher.

A rubber tire develops more traction the more weight you have on it. If you graph this, though, it is not a straight line. The tire actually loses efficiency at a higher weight.

Thus, a rubber tire can develop more g's of cornering power the lighter it is loaded. It is more efficient there. (a more detailed discussion of this is on my other thread). That means that lateral weight transfer on an axle is bad for cornering. The outside tire gains weight and gains some traction, but it loses efficiency. Weight is lost from the inside tire which is cornering at higher efficiency. This reduces it's cornering power. There is more loss on the inside wheel than gained on the outside wheel. The axle loses some cornering power.

On the oval this effect is greatest on the front axle and especially on the right front tire. The right front tire gets the most load from lateral weight transfer in the corner and back to front weight transfer as the car is slowed or braked for corner entry. There is a tendency then for the car to push as weight is transferred. We avoid this by placing weight left on a car that only makes left turns. This preloads the chassis so that when lateral weight transfer occurs we end up with evenly or more evenly loaded left and right tires. We develop the best cornering traction this way. So my first question is how much extra should we put on the left. More questions to follow for you oval guys that visit this thread once in a while.

We are looking for 6 cell equivalent with maybe a 17.5 (stock) or 21.5 (slower than stock) motor on this oval.
John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-oval-car-electronics-001.jpg   Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-oval-car-electronics.jpg  

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Old 02-04-2008, 03:50 PM   #1875
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Looks good John, nice job.

Will be intersting to see how the high panhard bar works out. Keep us posted, look forward to it.
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