Maximum Theoretical Weight

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sldwaa
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Maximum Theoretical Weight

Post by sldwaa »

I am entering an open race where there is no weight limit (it can exceed 5 oz). My question is, what is the point of diminishing returns due to friction? I once heard 10 ounces is the optimal weight, however, I am not sure. I am using stock BSA axles and wheels (all polished, etc), but am curious if anyone has testing or calculated what the max best weight is. Last year there were some heavy cars which were in the finals but I am not sure what they weighed. Second question, at this higher weight, is it still advantageous to bend the axles and ride the rail? I would think rail yes, but will the additional weight cause issues with the axle bending (1.5 degrees and 2.5 degrees is what I would anticipate doing). I do drill my own holes and do not use the slots. Lastly, will the COG at about 0.75'ish still apply or will this need to be adjusted also due to this weight. :scratching:

Thanks!
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whodathunkit
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Maximum Theoretical Weight

Post by whodathunkit »

I ran a class b semi truck set up to rail ride on three wheels.
However it was 25 ounces and 19 inches long.


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MaxV
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Re: Maximum Theoretical Weight

Post by MaxV »

Although I have not ran a test on this, from feed back I have received, around 10-12 ounces seems to be a point at which additional weight does not help, given standard wheels/axles (no bearings or similar). I'm sure the track length would also be a factor (shorter track less weight, longer track more weight).
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Re: Maximum Theoretical Weight

Post by Speedster »

We have an 8 ounce limit, graphite only, for our Outlaw race. The same 5 ounce wafer wheel car wins it every year.
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whodathunkit
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Maximum Theoretical Weight

Post by whodathunkit »

Randy
I would say that I was running close to 10 to 12 ounces as well.
With the wood weight of the truck around 7 oz
then 8 wheels.


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Stan Pope
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Re: Maximum Theoretical Weight

Post by Stan Pope »

From intuition ... run cambered axles with wheel's inverted to put weight on strongest part of the tread.
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whodathunkit
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Maximum Theoretical Weight

Post by whodathunkit »

Stan Pope wrote:From intuition ... run cambered axles with wheel's inverted to put weight on strongest part of the tread.

Okay Stan I'll try running the numbers on last years class b semi truck Blue sonic.
(might have my numbers all wrong here to convert them though.)

Stock axles 0.9 grams + 8 = 8.9 grams.
stock wheels 3.6 grams + 8 = 11.6 grams.. total 20.5 grams or 0.7231162 ounces.

7.4 ounce frame.. at 209.786 grams.
16.8 ounces of weight no including trim weights or paint and details.. total of 476.272 grams

20.5 + 209.786 + 476.272= 706.558 grams.
I figure with paint & details + the added trim weight it was somewhere around 62.9 grams at 2.218732 ounces.
706.558 + 2.218732 = 708.776732 grams ..( 25 ounces = 708.778 grams.)


EDIT:
Okay very late night when I posting the numbers seen above!

(25 ounces to grams = 708.738) and 1.562 to pounds... and not the 708.778 .
my trim weight was not right as well at 62.9 grams at 2.218732 ounce.
It should have been 61.2 grams = 2.158766 ounce.
So take 706.558 + the 61.2 grams = 2.158766 ounce for a total of = 708.738766
Last edited by whodathunkit on Sat Feb 06, 2016 4:56 pm, edited 2 times in total.
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Vitamin K
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Re: Maximum Theoretical Weight

Post by Vitamin K »

Are you running graphite or oil? I have been told that oil allows for much more weight than graphite to be added before friction losses kill any gains from inertia.
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sldwaa
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Re: Maximum Theoretical Weight

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I slammed some transformer weights in the cavity of a 5 oz. last years car (wedge shape), and it weighed in at approximately 14 oz. I put it on a tuning board with a slight decline, and with about the same axle / wheel prep as the current year 5 oz car, I noticed it was slower down the ramp than the 5 oz as you might expect. The 14 oz was only slightly faster than the 5 oz on the track at race day (both used graphite, not oil). The winning car came in at 2.5 pounds also using graphite and I came in second. Hmmm, the 2.5 pound winning amazed me, I know it was that heavy as I was the starter. I am still confused, so back to the drawing board for next year. The winner did not use bearings or any other unique devices. Does someone with no more scouts have a metal track they want to sell so I can figure this out this summer :scratching: :D
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Re: Maximum Theoretical Weight

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All you Physics Majors, is our thinking correct on this matter with all this weight. We race on a 30' Piantedosi track. We have an 8 ounce limit for our OUTLAW race. Yesterday a little girl won the race with my wife's Mid America car weighing 6 ounces. The only car that came close to her was my 8 ounce Mid America car. My car would have beat her at 5 ounces but I had done a lot of tests with it the past few years and it's getting tired. This is the second year the car won the race and last year it was at 5 ounces. I don't really know if it was faster or slower this year. I'm going to run a test and find out the difference between the 5 ounce car and the 6 ounce car (when the weather gets warmer.) The only car that's ever beat it is my friends wafer wheel car. He wasn't there yesterday. There were 2 wafer wheel cars in yesterdays race but she beat them by about 3 inches.
I did not inspect those 2 particular cars so I don't know what they weighed. Soooo, does all that heavy weight think about getting moving, and while it's thinking the Mid America Car is crossing the finish line on a 30' track? Obviously, people who build and race those slim wheeled cars can beat our car. I think if you truly want to win an OUTLAW race, even if there is no weight limit, study all the Physics involved with the rules you are dealing with. We don't put heavy wheels on a car to go faster.
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