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Old 03-10-2008, 10:20 AM   #1936
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Jev-I found some of those RW pinions for sale here. They look like 48 pitch (6 mod is stated should be .52 module) . I have a good supply of steel 48 pitch pinions. The titanium nitrided gold pinions from Stormer are extremely good. I was trying to find a steel 64 pitch.

Rear Steer
I examined the rear steer on a couple of custom works chassis. There is 5 degree hole available but interestingly it turns the pod clockwise on the vertical axis when viewed from above. This is opposite to the way I turned mine to cure the corner exit oversteer problem. It cannot be turned the other way on the custom works car.

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Old 03-11-2008, 01:21 AM   #1937
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http://www.rc-direct.co.uk/rw-racing...page=4&sort=2a

As long as they are the gold ones they are made the same as my 48dp set.
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Old 03-11-2008, 09:43 AM   #1938
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Jev-Thanks. I will order a few of those. I have some aluminum ones coming but they will only last one race. If they are steel and nitride coated they should be the best available from a wear standpoint.

Front to Back weight distribution

A car will have its best cornering power when the front and back cornering powers are their highest and equal. On a car with different tires front and back this is not neccesarily going to be at a 50/50 weight split front to back. I made a spreadsheet on a stock truck by first getting a load vs friction curve for front and back tires. the tires are different hardness front to back, harder on the front, and there is a huge rear weight bias (similar to a pan car). The spreadsheet would, calculate weight transfer, traction at each corner, then cornering g's at each axle for front and back. It was good enough to predict the change in handling of the truck as I moved the theoretical inline battery 1/2 inch forward. I could calculate the optimum battery position for best handling. I only did this to understand the situation not to use as a tuning tool. For a tuner it is good enough to know that there is an optimum position for that battery and he should search for it using the time sheet. With hard tires on the front the weight bias is going to be heavy to the rear not 50/50

So what I have done is move my pack 1/2 inch forward. My goal is to get better cornering and possibly eliminate some of my corner exit hooking which I think is caused by front end unloading on application of full power. I noticed 5 other cars out on the track with various degrees of this same problem. Some were almost undrivable as a result. If the problem is reduced I can reduce my rear steer or possibly eliminate it. This may make the car more efficient on the straights.
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Old 03-11-2008, 09:51 AM   #1939
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This actually sounds like a conversation we've been having on the 1/10th Pan Car thread - any way I could get you to comment on it?
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Old 03-12-2008, 08:25 PM   #1940
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Well Boomer-they want to send me off to little RC school. I say maybe they should pick up a book for once. Maybe a Physics book. Or a full size car racing book. The guys that write those full size racing books pride themselves in getting the Physics right! Especially the weight transfer.
Everything is new and a surprise to them. Shows lack or reading. It is all in the books. I just remember, test, and then repeat it.

Track Report
sugar treated but covered with pollen. The chassis came back yellow.

Moved Battery Forward .5 inch
I had surprisingly good traction both forward and cornering. I had moved the battery 1/2 inch forward. This had the effect of planting the front better on corner exit. I eliminated about half of my rear steer which was aimed at solving the same corner exit hooking. I did use 1 click of right steering trim on occasion to help me steer right just a little. The car was exiting suprisingly straight considering the traction. Part of this is improved driver training.

I removed 2 ounces from the car using aluminum screws and removing any parts of the car that did not look like an oval car. A new protoform THD body helped. I am at 40.4 ounces now without paint.
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Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-quaker-state-3-002.jpg  

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Old 03-13-2008, 10:08 AM   #1941
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Hi John,

Yeah, I know. It all started with just a quick question about no (or little) battery placement adjustment - which with the 10L2 in all of its evolution with us was incredibly important.

In any case, I found your arguments well spoken (as always) and their responses less than I'd hoped.

What I'd hoped for was an actual in depth discussion of these cars - akin to what you have done on this thread (and the TC5 thread, which I also follow)

Oh well. I guess if you get more than 2 engineers in a room you'll end up with bloodshed!
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Old 03-15-2008, 07:10 PM   #1942
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Boomer-thanks for the post

Protoform THD Impala ss

I changed from a McAllister COT body to the above protoform body. I put on wing and spoiler and used the suggested foam cutout line on the bottom. The major change was that I had a lot more steering traction. The rear end was loose in spite of a medium size wing. The trunk lid is much higher on this protoform body in the manner of new fullsize cars these days. This should result in lower overall friction. A low mounted wing is now above the roof line with this trunk, though, so I mounted it direct to the trunk. I now have a similar sized HPI wing but mounted up on HPI pedestals. The wing is not as big as on the previous body but I have a large spoiler that will help it. The spoiler was insufficient alone. I have one of the BRP oval wings but every time I go to mount it I don't like the looks a whole lot. I also do't care for those long piano wire extensions where the wing bobs up and down as the car goes round the track. One of the cars had a severe case of this and was dragging the ground on the down stroke of the wing.

I slammed the front end down now to hopefully reduce the front down force. Race tomorrow will tell.

Oval Gears
Gears. I decided on about the smallest spurs that would fit. I am running an 88 tooth Robinson racing spur. They are light and should reduce rotating mass. The pinion is still a Robust 35 tooth so friction from too small a gear should not be a problem. 64 pitch. Either a new gear each week or a steel gear will be needed in the future on our track.
John
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Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-quaker-state-3-protoform-thd-006.jpg  

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Old 03-16-2008, 06:11 PM   #1943
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Race Report
some pollen on the track. Traction improved by the main.

The impala SS body handled well like in the photo. Not too much steering, plenty of rear traction. The car won the first and third heats and the 7 car main. Now the main was some excitement as all the cars were in it and there was a wide variety of skills. This means I made about 25-30 passes of varying degrees of difficulty from easy to very difficult all the way to the end. You have seen the nascar video of the cars entering the smoke as two or so cars spin in front of them. Thats how most of the passes were. Over in an instant, inches from disaster. Second place was running faster laps (behind me) but got tangled a couple of times.

Gearing
my gearing continues to increase. My rollout is about 2.7 with the Novak 13.5 motor. I geared up a pinion in the third heat but the car was slower. There were a bunch of 30 mph gusts as well so maybe this is why it was slower. I returned to 2.7 but will try Mike D's bigger 2.86 rollout eventually.

Wing
I also might try that long (along the long axis of the car) BRP oval wing. Maybe there is some benefit to keeping the air from coming down onto the decklid. Most of the oval guys run the long flat part at roof height. I did try a smaller wing than in the photo and the car was a little loose especially in the huge gusts on the downwind turn.
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Old 03-17-2008, 11:41 PM   #1944
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Based on the second race's results I need a couple tenths more speed. I have very good consistency and freedom from spins. Here are some things that I did.

Speed Control
I put the Spere Comp TC edition back on instead of an older Sphere comp as the fast laps in the first race with the TC edition were a tenth faster than with the old sphere. (I made several changes from race one to race two so this may not be a problem at all.)

New Battery Tray
I knew that my batteries were a bit high in the car so I made a new battery tray with slots this time for my stick pack arranged four cell pack. The new tray is mounted to a beveled rail. I will be able to make adjustments forward by remounting the tray to the rail. This might help a bit in the corners by reducing lateral weight transfer. The lower the better.

Pinks on the Front
I have some pinks coming for the front. Maybe the key to having less scrub in the corner is having a softer tire rather than a hard one in the front. I have used pinks up front on the wide pan, but it travels a lot faster and just wore them out quickly without much benefit. It may be different on the Novak 13.5 four cell car. I know I can mix purple outside and pink inside.

Gearing
I have some new pinions coming to up the gear a bit. I was not too far off Mike D's ratio who got fast lap.

I have a lighter SS13.5 motor coming since this is allowed and prevalent.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-200-mm-3-link-oval-car-battery-tray-004.jpg   Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-200-mm-3-link-oval-car-battery-tray-006.jpg  
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Old 03-23-2008, 01:21 AM   #1945
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Race Report
under the lights
We had our first evening race. Traction was good, pollen season is over. I had trouble seeing the cars with black paint jobs, but otherwise the 3 link car did OK. I had made 3 major changes that together were worth about .2 seconds on the short flat oval. The major benefit was putting 2 pink fronts instead of two purple fronts or one pink inner and one purple outer. This really improved the grip and reduced scrubbing. It also cured the corner exit spins. I had spoke about this previously early on this thread and noted that putting on harder front tires made this problem worse. I suspected the fronts were unloading. Well these result adds additional credence to that theory. It helped two other cars with the same problem to put on two pink fronts as well, they had much better performance on corner exit.

I tried gears between 2.84 and 2.93 rollout. Fast laps are now within .05 (5 hundreths of the other fast car). That is not a lot of difference in the two now except that he has years of oval experience and I have years of onroad experience. These gears are now in line with what other oval guys have reported but still 7 teeth less that Mike D is running in the slightly faster car.

McAllister COT and Protoform THD
After running both this Protoform THD body and the McAllister COT, I am thinking the McAllister body is .1 seconds faster. I will have to try it again. I guess that HD means high downforce. I probably do not need so much.

The 3 link car got second place today, but it was more a function of how long first and second place spent whispering the word Marshall as we were upside down on the track. only .5-1 second separated the two cars at the end. Pretty exciting with lead changes a couple of times.

I ran large tires (brand new) with no traction compound in heat 3 and the main due to adequate traction. There was some dampness off of the main line that would slow you down if you were not careful.

The new battery tray worked well. I will play with battery forward adjustments next race as my gear selection is settling down.
John

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Old 03-25-2008, 05:56 PM   #1946
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I took a look at the new Associated RC 12 R5
This is a center pivot side link road car. Who knows it may make it up to 1/10 scale. Also available is a T plate chassis option. Interestingly their finding on the two mirror my own stated in this thread

"The pivot ball-link chassis has proven to be more durable in high speed impacts and better in bumpy track conditions."

Some interesting features include shocks with thru shafts. These continue out the top of the shock. The shock is then free from the rebound effects as the internal shaft volume is always the same now. This feature seemed essential for using only one shock to control roll. There are some wrench flats on the bottom of the shaft and splines near the top that seem to indicate some kind of internal adjustment. I did not see this discussed. Maybe just shock length. The manual is not yet ready for download.

The front end is composed of all new parts, but of similar design as the old car. The upper A-arm is a little beefier looking. There are some new Aluminum uprights to support the suspension. I don't like the way this inverted strut type of suspension confounds the roll center adjustment with the camber adjustment; when you adjust camber it is not independent of roll center but rather changes the roll center as well. The rear end is novel in the use of a single shock to control roll. There are also two small side springs along with this one shock. I am glad not to see damper tubes which seize up on my track.

John

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Old 03-25-2008, 06:12 PM   #1947
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it is my understanding that associated is one of the companies planning a 200mm gt10..
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Old 03-25-2008, 07:19 PM   #1948
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Quote:
Originally Posted by John Stranahan View Post
I took a look at the new Associated RC 12 R5
This is a center pivot side link road car. Who knows it may make it up to 1/10 scale. Also available is a T plate chassis option. Interestingly their finding on the two mirror my own stated in this thread

"The pivot ball-link chassis has proven to be more durable in high speed impacts and better in bumpy track conditions."

Some interesting features include shocks with thru shafts. These continue out the top of the shock. The shock is then free from the rebound effects as the internal shaft volume is always the same now. There are some wrench flats on the bottom of the shaft and splines near the top that seem to indicate some kind of internal adjustment. I did not see this discussed. Maybe just shock lenghth. The manual is not yet ready for download.

The front end is composed of all new parts, but of similar design as the old car. The upper A-arm is a little beefier looking. There are some new Aluminum uprights to support the suspension. I don't like the way this inverted strut type of suspension confounds the roll center adjustment with the camber adjustment; when you adjust camber it is not independent of roll center but rather changes the roll center as well. The rear end is novel in the use the use of a single shock to control roll. There are also two small side springs along with this one shock. I am glad not to see damper tubes which seize up on my track.

John

The flats on the shock shaft are for adjusting pod droop without removing the shock. Pretty cool but i thought that using a knurled cap and and ballcup on the cap would have been more simple. turn the cap and it backs the ballcup off and increases shock length. No tools needed. I was able to do this on our new car with IRS's new macro shock. They offer 2 styles of caps which really made a super cool and easy adjustment for pod droop.

Not sure im following you on the front end though. Please explain on the camber/roll center better so i can see if i am following you. On the existing AE front end,and from what i can see on the new one,roll center and camber adjustment are completely isolated from eachother.
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Old 03-25-2008, 08:06 PM   #1949
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The instant center on this inverted strut (inverted McPherson Strut) is determined by extending a line at right angles to the kingpin at the lower pivot. A second line is extended on the upper A-arm axis. Where the two meet is the instant center. A line from the tires contact patch to the instant center meets the roll center at the vertical center line of the car.

Because of this when you change camber you change the angle of the kingpin and thus the lower right angled line. This changes the instant center and thus the roll center. This was explained to me earlier in this thread. The roll center may be no where near what you expect based only on the camber of the tire that you need to run.

My twin A-arm pan car front suspension does away with this little defect as well as all the stiction of that sliding kingpin. Grip on asphalt is improved.
John
Attached Thumbnails
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Old 03-25-2008, 08:23 PM   #1950
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Ok, i do see how you can get a slight bit of change now. Have you seen the old HPI front end with hinged upper and lower arms with inboard springs? That was actually a really cool front end. A little much but very cool indeed.
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