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Old 04-26-2008, 06:06 PM   #2011
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I believe that would be the correct one. It will fit any brand of 1/10 pan front and rear tire. The front wheel with bearings removed is going to use the smallest diameter on the tool. There is about a 5/8 inch hole in the back wheel that should fit the larger diameter of the tool. I'll bump this up to get a second opinion.

I was asked for a link to the DNA pan car front suspension which came from the RC10DS. My link is broken. Tell me If you have a working link to this or a similar aftermarket front suspension for a velodrome car.
John

Last edited by John Stranahan; 04-26-2008 at 09:32 PM.
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Old 04-28-2008, 10:14 AM   #2012
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http://www.southwesttour.com/images/...ront%20end.jpg
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Old 04-28-2008, 11:48 AM   #2013
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Steve-Thanks. I forwarded that link. Those are good images of the DNA front end, but are they still for sale somewhere. The link does not point to a store.

I did a short test with BSR pinks front and rear on the asphalt oval. They were really hooked up. A fellow competitor drove my car. At first it had way too much steering for him. Then when he started to drive the wide line he was doing good laps with very little scrub.

I need some more tire information. Someone told me that Jaco and BSR tires used the same foam. They seem to handle differently for me. The Jaco pink is a little harder than BRP pink. Can someone elighten me. As GRP tires are becoming unavailable here we are looking for alternates.

I think my question is answered here on BSR's website.
"
Purple - Duro 38-43
BSR developed their own mix of select sheets and seam positioning for our purple. BSR's single purple is different than others. If you want a purple similar to say Jaco use Our Double purple.

Medium/firm compound recommended for carpet and aspalt racing. Low wear/ longer lasting characteristics."

One thing I noticed straight off is the car gained an ounce of weight when I put on the BSRs
John

Last edited by John Stranahan; 04-28-2008 at 10:03 PM. Reason: made a brand mistake BRP instead of correct BSR
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Old 04-28-2008, 12:21 PM   #2014
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Try posting at www.southwesttour.com on the message board. You should be able to get answer there.
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Old 04-29-2008, 07:17 PM   #2015
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SKJ-thanks. I got a parts list from there. Seems that a lot of the parts are out of production.

What fun. Racing a car that looks like a full size race car. Protoform Dodge Charger HD. Summit racing #12.
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Old 04-30-2008, 05:38 AM   #2016
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Moving Weight Forward
Bob Stormer asked a question on the 1/10 pan thread a while ago. I thought I would answer it here. What happens to the car when you move the battery Ĺ inch forward?

I plan to give two answers, one without numbers and one with numbers in the following post.

The first answer is simple. Well it depends. It depends on situation in the car before the battery is moved.

Let me consider first a more simple case than a pan car; a 4- wheel drive touring car with the same tires on all four corners. This type of car corners best with near a 50:50 weight split. If you have the 50:50 weight split on the car and have carefully adjusted springs and shocks for a neutral oversteer/understeer balance (where the car drifts sideways out to the boards if you corner too hot). Moving the battery forward will create an understeer condition or a push. The extreme case is to tape the battery pack to the hood of the car. The push will be very extreme and apparent. If you donít believe this then actually do it to a touring car or a stock truck. Now why discuss the equal tired car. I notice that a lot of the velodrome guys are driving pan cars with capped rubber tires that look very similar front and back. I also notice they tend more toward a 50:50 split than we do on the flat asphalt oval.

So why do we get a push moving weight extremely forward, with the front tires loaded higher. The reason has to do with the way rubber tires lose efficiency the higher they are loaded. We have unloaded the rear tires a bit. They are more efficient. There is less weight transfer at the back now so our losses are low. At the front the tires are more loaded, they are less efficient. There is more lateral weight transfer from the extra weight, so the losses are high from lateral weight transfer. The inside front loses a lot more traction from lateral transfer than the outside front gains.

Now letís take two pan car examples. Because a pan car is two wheel drive, there are huge benefits to forward traction by putting weight toward the back. This causes an oversteer cornering condition. Now if you have not routinely over steered the pan car when learning, you are a much better man than I. So what is done, is a less efficient narrow front tire is used. On powerful pan cars a harder front tire is also used. On most pan cars a substantial rear wing is used. This gets the oversteer under control. If we manage to get the car perfectly neutral on a particular corner and then move the battery 1/2 inch forward then we will create less steering traction (even though we are far from a 50-50 weight split).

Letís say I have the battery Ĺ inch back from Ideal when I make the Ĺ inch movement and the car has some Push already. Moving the battery forward will create some additional steering traction which brings your battery closer to the ideal position and then further movements forward will create less steering traction. Thatís why it depends. A numerical example follows.
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Old 04-30-2008, 05:50 AM   #2017
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This example involves a mod truck. Because it is 2 wheel drive the weight placement in the truck is very similar to mod pan car. Lots of weight back. Soft grippy mini pins in the rear. Hard wedge fronts worn almost smooth. I had the same question Bob did. What is happening when I move the battery forward. From track experience I liked the battery 1/2 inch back from the front of the battery tray in the Losi XXT truck. It is a simple matter to answer this question on the track. You just move the battery one half inch forward and then see how it corners. To calculate this you have to measure several things.

The tires traction curves as weight is added to them. This is shown in the two graphs below. Note the lines go up, traction increases with weight, but the lines curve concave down as the efficiency is reduced with weight.

The weight of the front and the back tires at various battery positions.

The aproximate average cornering g's of the truck. I used Physics to measure this.

The deceleration rate of the truck. Determined from a coast down test.

With this data you can calculate the cornering power on each axle and model what is happening on the track. The chart on the left gives the results. If you look at the column labeled cornering power on each axle, note the front axle or steering traction is above the rear axle cornering traction. As we move the battery forward I go up in the chart. The steering traction improves slightly in the first lowest step (but noticably on the track) then deteriorates as I move the battery farther forward.

So the only thing this should tell you is there is an optimum battery position and you should hunt for it on the track.

E-mail me for the Spreadsheet to get a clearer image of the second table. [email protected]
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-weight-transfer001.jpg   Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-weight-transfer002.jpg  

Last edited by John Stranahan; 04-30-2008 at 11:22 AM.
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Old 04-30-2008, 02:25 PM   #2018
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What about Static vs. Dynamic coeffients of friction on rubber tires.
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Old 04-30-2008, 04:01 PM   #2019
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Trailranger-thanks for the post.

The graphs were obtained by sliding the rubber tire accross a granite stone. They were dynamic results. The results were checked on asphalt and hard clay and were comparable. Rubber has a couple of unique properties compared to other materials. One is that the dynamic friction is higher than static friction. It's as if there are thousands of tiny fingers of rubber walking accross and griping the surface when the rubber is sliding. Most other materials have a higher static coefficient of friction.

The second unique property of rubber is that the dynamic coeficient of friction has a curved graph. The rubber loses efficiency the higher it is loaded. This explains the use of very wide tires in most racing applications including the rear of our pan cars. The rubber is loaded less this way.
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Old 04-30-2008, 05:17 PM   #2020
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Interesting John...
I've always assumed the opposite that rubber in a static situation(wheel speed matches ground speed) has more grip than rubber in a dynamic situation. That may explain a few things, like how sprint cars get around the track so fast.

I am sure wheel slip is not best for tirewear but being faster wins the races.

I think tires need to be rated differntly than just Softness in Shore.
I think a new measurement needs to be added Shear(Static or Dynamic grip)

Adding this rating would be easier to compare "colors" and shore numbers since for example all these colors are the same shore but vary in grip:
Pink, Green, Gray, Yellow?
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Old 04-30-2008, 08:20 PM   #2021
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Quote:
Originally Posted by trailranger View Post
Interesting John...
I am sure wheel slip is not best for tirewear but being faster wins the races.

Adding this rating would be easier to compare "colors" and shore numbers since for example all these colors are the same shore but vary in grip:
Pink, Green, Gray, Yellow?

What you want in cornering is some drift velocity or some slip angle. This lets the rubber slide accross the surface creating maximum grip. If the slip angle is too high then the rubber lets go. There is a peak in this dynamic friction. On my granite test block the peak seemed to be at an estimated 3-4 cm/sec of sideways slip. You could clearly see the tire let go on the scale if you pulled it faster. You could also see the force required increase when the tire started to slide.

http://www.rctech.net/forum/attachment.php?attachmentid=164204&d=1156882828

This trinity shore rating and softness chart is a popular download from early in the thread. It shows some softness difference in the colors you mention.
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Old 04-30-2008, 09:30 PM   #2022
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You are the man John.

I may have to give you a nick name....

thinking...

thinking

thinking
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Old 04-30-2008, 09:37 PM   #2023
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Still thinking on a nick name...

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Old 05-01-2008, 06:36 AM   #2024
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Now, if they teach these in school, i wouldn't be busy falling sleeping!

Great explanation! It's great sharing!
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Old 05-01-2008, 12:25 PM   #2025
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maybe a little overdone on the capt planet, but I was having a hard time finding Mr. Wizarrd stuff.

John Sure knows his stuff.
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