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Post by gulpster on Apr 4, 2012 17:38:49 GMT -7
Hey guys, still new to building but 4 cars built at my Sons Den. His, Mine, Wife's, and Daughters. We all won. So I'm doing something right. Now I'm already thinking of next year and want to get all my questions out of the way. So heres my two for this segment.
1. Center of Gravity. 25 percent of the length from the rear forward to find COG? This is 1 3/4 from the rear of the car forward. I'm using this from the common accepted rule for RC Aircraft in lew of the Engine to rear of plane. Is this the correct way of thinking?
2. I have been told to stretch the wheels as close to either end of the car as possible. I have seen some real demons on the track where the front wheels were over an inch from front of the car. Why is this? I'm just wanting the comprehension, not making an opinion.
Thanks
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Post by P D D R 2 on Apr 5, 2012 9:14:10 GMT -7
Hey guys, still new to building but 4 cars built at my Sons Den. His, Mine, Wife's, and Daughters. We all won. So I'm doing something right. Now I'm already thinking of next year and want to get all my questions out of the way. So heres my two for this segment.
1. Center of Gravity. 25 percent of the length from the rear forward to find COG? This is 1 3/4 from the rear of the car forward. I'm using this from the common accepted rule for RC Aircraft in lew of the Engine to rear of plane. Is this the correct way of thinking?
What works really good is 1/8" to 1/4" in front of the rear wheel tread surface, this is a good place to be. Balance the car at this point.
The longer the weight stays on the hill the more acceleration it will get.
But if track conditions are bad you will need to adjust.
2. I have been told to stretch the wheels as close to either end of the car as possible. I have seen some real demons on the track where the front wheels were over an inch from front of the car. Why is this? I'm just wanting the comprehension, not making an opinion.
Depending on the sytle of car and track be raced on can affect which wheelbase works best.
Thanks
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Post by gulpster on Apr 5, 2012 15:33:09 GMT -7
1/4 to 1/8 sounds intense! Im currently getting it down to getting the cars with wheels and axles to under 1 onces so I can have 4 oz of weight to play with. Slim frame, hollow, balsa capping and finish resin firberglass to keep the balsa grain down.
So with that light weight in mind, front end rising not a factor with the COG that far back? Or is is down to track condition. Track is the long aluminum 6 wide. District they use BestTrack.
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Post by John Thawley on Apr 19, 2012 10:36:26 GMT -7
I think someone is having a good laugh. For my money, 1/2" is the danger zone. You're going to need to nail the steer-in just right or you'll wiggling all the way down.
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Post by esollars1 on Nov 10, 2014 11:33:26 GMT -7
Just starting out is tough. The very fast guys are getting the COG below 1/2 inche in front of the rear axle. At one time 1/2 inch was dangerous and you would wobble-fish tail down the track. As the fast guys have gotten the friction out of their cars they have been able to get a low COG below 1/2 inch. I would suggest if you are just starting stick with 5/8 inch in front of the rear axle for the COG. That was low at one time. Graphite cars are notorious for needing a COG higher than the oil cars. Wood tracks or rough tracks need a higher COG of at least 5/8 inches in front of the rear axle.
Depending on the cub competition you don't need to take the chance of fish tailing with a COG of < 0.5 inch. Cub competition would be ok with 5/8 COG. League competitiuon would need a COG at 0.5 or less COG.
Good luck racing.
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