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Old 10-02-2008, 05:33 AM   #301
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I have power now, after 16 days without due to Hurricane Ike. Things are returning to normal. Life has been at a standstill. Nice to have a working refrigerator etc.

Hey John, maybe time to think of buying a generator for the next time???? LOL ... Glad to hear you're okay that's the main thing.

Maybe the third week of this month.

Seeing is believing.

John
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Old 10-06-2008, 09:20 AM   #302
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Gasolene supply was a major problem during our power outage. One of those huge propane powered backup generators would be nice, but I can fund my R/C hobby for about 5 years on the cost.

13.5 LiPo/6 cell
We had only a hanfull of oval guys show. Maybe too soon after the storm. We ran 13.5 LiPo, Two guys for the first time. Everyone that tries it really likes it, especially Herman who was out with only his Nitro cars that day. He does have an oval car, but drove mine today. He was very pleased with the added zip on the straights. You can actually see the car accelerate now from the drivers stand instead of just imagining that it is doing so.

We worked on a Hyperdrive Pro III. The added power caused some recurrence of corner exit hooking. He was running pinks on three corners and purple on the right front. I suggested he try a purple right rear as this had helped my car under a particular track condition. (low-med traction). It did not help this time. What did help was adding some lead to the left side rear of the chassis to bring the car up to near 43 ounces. I think he must add some more to get legal 6 cell weight. My car is fully ballasted with a huge chunk of lead which may partly be the reason it is behaving so well on corner exit. Herman had no problem driving it free of mistakes. I do also have left rear positive offset and left rear steer helping.
My car was really fast running BSR XXPink fronts and XXPink/purple rears. We had med-high traction.

I also ran some fourcell with a late comer. He has an interesting oval project going. We started with his old RC10L2. This is a wide road car. Graphite chassis and graphite pod top plate with a wide pod. It is setup for a Viscous disk controlled pod. He had modified it to a single rear side shock much like the new RC10L2. It is on the wrong side for oval though. He lacks sufficient left down tweak adjustment. I told him there was a market for these wide cars but the conversion to oval proceeds. I had an old RC10L2O lower pod plate. He plans to convert his wide pod to an offset pod and use as many of the original axle plarts as possible. I'll report how that goes. My car needed no changes to run four cell. I probably could have removed the weight.

Pic shows Lead ballast weight on a little graphite arm so I can adjust it left and right if needed. Protoform THD is holding up well.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-lead-ballast-weight-resized.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-protoform-t-hd-front-view-resized-last.jpg  

Last edited by John Stranahan; 10-08-2008 at 11:15 PM.
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Old 10-10-2008, 08:53 PM   #303
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Changes in order to profit from 13.5 Brushless LiPo
Our change from 13.5 Brushless 4 cell, to 13.5 Brushless/LiPo has brought some welcome relief in several areas, one in the area of required weight. It is 41 ounces for the 4 cell and 43 ounces for LiPo or 6 cell.
Now if you were to just add 2 more NiMH cells to the 4 cell car you would gain 5 ounces. Now your car would be 46 ounces. Pan cars are somewhat finicky about their weight to achieve the best traction. You have to get through a layer of light dust to have traction, this requires weight, but you have to be somewhat light weight to corner well (the latter is true of all racecars). A 43 ounce pan car in my tests is about ideal. A 46 ounce car will start to corner poorly. I feel that a LiPo at 43 ounces will produce a superior car to NiMH car at 46 ounces.

With 13.5 LiPo the car starts to act a little like mod pan. On the oval you are traction limited on almost the whole oval instead of being motor limited for a good half of the lap. Rolling on the throttle becomes important instead of slamming on the throttle. This means that slight differences in battery voltage or 1 Watt differences in motor power are less important. Setup and driver skill will replace these.

Durability can now be improved with the heavier slightly faster powertrain.

Gone will be the skinny Associated style body clips in favor of the thick Losi style body clips. Note that the full size Cup cars also use body pins rather than dzus fasterners (1/4 turn locking screws) or a more streamlined fastener in the hood. They look much like ours; I have used them myself on one of my street cars.

Gone will be the horrible (for outside pan car) 64 pitch gears. These are completely worn out on our track in one race. You end up running really raggedy looking gears in the main even when you start the day with a brand new set. I have an order in for RW lightweight hardened steel pinions. (Jev UK's reccomendation) These are titanium nitride coated as well as being made of hardened steel. I have ordered these in 48 pitch which are much more durable outside. I have a 72 and 74 spur coming. Pinions around 29 teeth are suitable. If you think 64 pitch gears are fine on a pan car just apply the brakes one time. They will strip out. The oval guys usually tune all the brakes out which makes it quite commical trying to line up for the race. The cars just roll and roll. The tall gearing is also somewhat to blame.

I will be able to fit a full size foam bumper. I have a couple of the new CRC foam bumpers coming.

I will be able to run with the back of the body less cutout which is my preference from my wind tunnel tests on the Pantoura thread.

Pic-If you look close you can see a body pin on the hood as well as some other important racing hardware.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-busch-series-car.jpg  

Last edited by John Stranahan; 10-10-2008 at 09:26 PM.
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Old 10-11-2008, 05:42 AM   #304
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[B][SIZE=4][COLOR=red]
Pic-If you look close you can see a body pin on the hood as well as some other important racing hardware.
John
In your dreams John
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Old 10-14-2008, 08:12 PM   #305
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I have plenty of dreams. They are more like this one though.

World Gt and the Sliding Kingpin Front Suspension.

There is a little interesting clause in the World GT Rules. I will just call it the Anti Stranahan (anti MLP also) or anti progress, clause as I am sure my work on the Pantoura Thread was consulted to craft this little clause or maybe not. I noticed that at the International Indoor Champs, that this clause was not strickly followed. There were some corraly cars where the front uprights ride on top of what can be called a big flat swaybar. Not really the sliding kingpin type. I notice at the Cleveland indoor champs there will be another World GT event. This is great. However they have published this little clause on the race web site. I don't know if the corraly car will be allowed. My 3-link oval car with mighty small changes would be a World GT car. The rear would pass, the front would not because of the anti progress clause.

So the question is how to make a nice dampened front suspension that would follow the world GT class Rules. I present the following model of a non working front suspension. In this suspension the upper arm is fixed to the chassis (some parts are obviously missing here). The lower arm swings as god intended. The steering knuckle pivots on the standard ball joint. The upper shock mount pivots on a ball but cannot move up and down or in and out. This upper ball is fixed to the chassis. The lower end of the shock mount is rigidly attached to the steering arm by a tiny piece of machined steel or plastic. (not built yet). The camber angle can be fixed by a selection of these little parts. The roll center will be low regardless of the camber angle because of the inclined kingpin. The kingpin around which the steering rotates is the shock shaft. It certainly slides. So there you go. A sliding kingpin front suspension that is fully dampened. Automotive people call this a McPherson strut front suspension. Not as good as two moving A-arms on camber control, but better than the Associated inverted strut suspension in that the camber and roll center can be independently set. Also much better in that it is fully dampened. No more nasty goo need be applied to the kingpin shaft.

So what don't I really like about the associated front suspension. Well the car flies when it hits a bump at speed. It lacks damping. There is also too much tire scrub sideways as the tire goes up in bump. This limits cornering performance through the bumps. I never get a good rippled front tire wear pattern with this suspension, the tire is always scrubbed smooth. This is all well discussed and solutions made on the Pantoura thread.

For a better view of this suspension type just look under the front of your full size (normally priced) car.

My tests also showed the front shocks working better the closer and more directly you put them to the wheel. This is certainly about as close as is possible. About the same as in my dual moving a-arm front suspension. The shock shaft may need upgrading to a bigger size in this configuration. The shock piston size is OK though.

Note that nice Delrin fully machined lower A-arm. (not the threaded stud) I hear CRC may make another run for the upper arm of the associated or CRC suspension.

These are just thoughts for the future. Don't take them personally please.

pic is a front view of the right front suspension. Photo shows the shape of the shock support needed. A little less shock angle is desired. Tire clearance is super. The left most vertical pin can be very short and is really just part of a ball joint. It is not the kingpin.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-mcpherson-strut-front-suspension-b-resized.jpg  

Last edited by John Stranahan; 10-15-2008 at 01:37 PM.
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Old 10-14-2008, 08:18 PM   #306
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Quote:
Originally Posted by John Stranahan View Post
World Gt and the Sliding Kingpin Front Suspension.

There is a little interesting clause in the World GT Rules. I will just call it the Anti Stranahan (anti MLP also) or anti progress, clause as I am sure my work on the Pantoura Thread was consulted to craft this little clause or maybe not. I noticed that at the International Indoor Champs, that this clause was not strickly followed. There were some corraly cars where the front uprights ride on top of what can be called a big flat swaybar. Not really the sliding kingpin type. So maybe only antique suspensions were allowed. I notice at the Cleveland indoor champs there will be another World GT event. This is great. However they have published this little clause on the race web site. I don't know if the corraly car will be allowed. My 3-link oval car with mighty small changes would be a World GT car. The rear would pass, the front would not because of the anti progress clause.

So the question is how to make a nice dampened front suspension that would follow the world GT class Rules. I present the following model of a non working front suspension. In this suspension the upper arm is fixed to the chassis (some parts are obviously missing here). The lower arm swings as god intended. The steering knuckle pivots on the standard ball joint. The upper shock mount pivots on a ball but cannot move up and down or in and out. This upper ball is fixed to the chassis. The lower end of the shock mount is rigidly attached to the steering arm by a tiny piece of machined steel or plastic. (not built yet). The caster angle can be fixed by a selection of these little parts. The roll center will be low regardless of the camber angle because of the inclined kingpin. The kingpin around which the steering rotates is the shock shaft. It certainly slides. So there you go. A sliding kingpin front suspension that is fully dampened. Automotive people call this a McPherson strut front suspension. Not as good as two moving A-arms on camber control, but better than the Associated inverted strut suspension in that the camber and roll center can be independently set. Also much better in that it is damped. No more nasty goo need be applied to the kingpin shaft.

I would put this on the Pantoura thread but my intentions were to archive that thread and continue on with similar topics in this one.

So what don't I really like about the associated front suspension. Well the car flies when it hits a bump at speed. It lacks damping. There is also too much tire scub sideways as the tire goes up in bump. This limits cornering performance through the bumps. This is all well discussed and solutions made on the Pantoura thread.

For a better view of this suspension type just look under the front of your full size (normally priced) car.
John, that would look pretty cool all machined up.
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Old 10-15-2008, 08:41 AM   #307
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I probably will not complete a prototype as my current front suspension works great. Just an idea.

Inerter
While on a theoretical bent, waiting for new stuff to show up, I thought I would discuss a new device, I read about in Race Car Engineering News, that is being used very succesfully in formula 1. It is attached to the suspension arms much like a shock. A similar device might do wonders to return our heavy pod back to ground.

The device consists of a rack and pinion gear. The rack is attached to the suspension arm. The pinion gear is held steady by the frame. On bump the rack spins the pinion to which is attached a tuning weight. In other words suspension travel spins the weight. To understand how it works I will write some theory first. It is well know that the car will corner the best and accelerate the best if the tires have a uniform, unchaging contact pressure with the road. Unfortunately there are always bumps which tend to undo this. We compensate with shocks. Being passive though shocks cannot anticipate a situation, they can only react to them. The next generation would have been computerized active suspension. This was outlawed in F1. Now comes the inerter which is a mechanical device that when tuned can anticipate the end of a bump and help drive the wheel back down in concert with the spring. It can also help drive the wheel up toward the top of a bump. The end result is more uniform tire contact pressure and better grip.

Our rear suspension being rather heavy might profit from such a device. It would be no more complicated than say a gear diff to make. Just an idea and point of discussion. I personally am for mechanical aids to traction, and not so much for a computer driving the car. Yes it would drive the price up. Tamiya could make it.

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Old 10-15-2008, 11:08 AM   #308
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I have also read the article in Racecar-Engineering. In my opinion, a system like this is much to complicated and heavy for 10th scale.
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Old 10-15-2008, 01:20 PM   #309
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If you look at the complexity of a servo and the fact that a micro servo might sell for $20, then this device would be a bit simpler and could be priced within reach. In fact the gear train of a low torque servo may be ideal. It does not have to be a rack and pinion. The servo arm could be driven off the center shock pod mount and the servo itself with no power could be the device. There would have to be some friction reduction with use of metal gears or maybe one fewer set of gears. What would be needed is a way to adjust the rotating weight. On an oval car there is even room for the device down low. It could be less than 1 ounce total weight. I have 3 ounces of lead in my car. This may warrant a test in the future.
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Last edited by John Stranahan; 10-15-2008 at 01:39 PM.
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Old 10-15-2008, 01:39 PM   #310
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What sizes are you guys starting your pro 10 tires at?
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Old 10-15-2008, 02:04 PM   #311
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I used to run my wide pan tires at full height on lower traction days and then save a set of shorter tires to race on. Now I cut my oval tires to 2.260 inches. I usually practice on them once and then race them until the plastic starts to show on the edges.
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Old 10-15-2008, 07:02 PM   #312
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Funny you mention that clause in the rules about the kingpin suspension....

I thought it fairly ludicrous as well considering the technological advancements of 2wd/4wd gearbox conversion kits to today's current touring cars.

If the tech is there, why can't we use it?

But instead of complaining, is it possible to build a cantilever system? And before you laugh, bear in mind i teach language arts, not race car technology.
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Old 10-15-2008, 07:18 PM   #313
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Pejota-The rules don't mention or forbid a shock. The present suspension can be dampened by a shock with a simple setup. A cantilever could be used also to attach a shock. I found the shock more effective the closer and more direct it acts on the wheel though. Here is a pic of a simple conversion to shocks. This helps but not as much as the reduced friction and improved geometry of the double wishbone. Sketch that puppy up and we can take a look at your cantilevered suspension.

Pic the car is a Powell wide pantoura chassis. Some CRC Pantoura and IRS parts, RC18T home added front and rear side shocks. Parts list available on the Pantoura thread.
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Old 10-16-2008, 09:15 AM   #314
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Inerter Continued

I have assembled a prototype inerter which I discussed above. In brief what the inerter should do is build up inertia on the ramp of a bump. This inertia is then used to force the suspension up a little higher than normal at the top of the bump reducing tire contact pressure that would ordinarily be at a maximum here. This also "winds up" the suspension spring for a good strong push down the backside of the bump. The initial push builds up reverse inertia which is used near the bottom backside of the bump to accelerate the tire down into good contact where ordinarily contact would be light. The device if tuned right anticipates the top and bottom of the bump. Tire contact pressure is more even. There is more traction available.

I took an old "non Coreless" servo which has a standard looking motor with armature. I removed the pots that control its position. I removed the circuit board. I took the brushes out of the motor. There is no O-ring seal. If I give the servo saver a little torque the saver continues to move about 1/4 to 1/2 inch depending on how hard I push. The inertia built up in the armature does this. I will use a single link to attach the servo saver so it moves with the pods up and down motion. If it shows any promise at all, I can use a radar gun to see if it improves speed on the straight. I know that with my wide pan this is traction limited by the bumps. Weight is 1.7 ounces. I have 3 mounting heights for my link to tune it.
John
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Old 10-16-2008, 10:45 AM   #315
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Hi John

If I understand right, you need a centering spring as well as the one directly connected to the suspension. . . were you thinking of having this between the two suspension sides using them as centering springs?

Were you thinking of a parallel or serial setup? The graphs at http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf seemed to show that each was somewhat inverted from the other in terms of action. . .

very interested in this. . .
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