Scout outlaw help

[Bubblegum]

We have our District race coming up and there is an outlaw/family class and I am wanting to build two new cars for it plus replace parts on our first place car.
Basically the rules are standard regarding rules except extended wheelbase are allowed and max weight is 7.0 oz. At the pack we place 1 and 2 with two different designs. I have new parts now (thanks John) so I am hoping for better times.

My questions are regarding wheel base and weight. Also I imagine weight influences steer and axle bend. I remember an older thread about weight choice but cannot find it yet.

So any suggestions on those as a starting point? Thanks.

 

[Bubblegum]

I did some digging and there seems to have been discussion on this around 2014 and then kind of died out.

Seems that 6 oz seems to be the sweet spot for a heavier car if allowed from the previous posts and that 5 oz does as well as 7 oz.

Much to ponder on weight vs. diminishing returns.

 

[Thinkin'Bout Racin]

I believe that track length would play a big role in the decision on how much weight.

 

[Bubblegum]

42'

So is it better to have more weight yet take longer to roll but gain in the curve or faster off and further down the line?

I cannot think of too many times if ever when a scout car has been passed when in the lead going into the straight section.

 

[Thinkin'Bout Racin]

42'


I cannot think of too many times if ever when a scout car has been passed when in the lead going into the straight section.

I agree not very often. However all of those cars are at or close to 5 oz. In this scenario, one might have up to a couple ounces more weight than another car ...I am not sure, but in my simple mind that could change things.

On a 35' track, you probably could go heavy. A 49' track ....probably just a bit heavier than the 5 oz. A 42' track ...maybe split the difference.

 

[DerbyBoyz]

I did some digging and there seems to have been discussion on this around 2014 and then kind of died out.

Seems that 6 oz seems to be the sweet spot for a heavier car if allowed from the previous posts and that 5 oz does as well as 7 oz.

Much to ponder on weight vs. diminishing returns.

I want to say 5Kids did some testing on this same thing awhile back. I think he had posted his results as well? May want to do a search maybe under 5Kids?

 

[Bubblegum]

Thanks for the help and suggestions. I started looking but haven't finished yet.

May take my 7 oz. car and start taking weight off just to see if there is a sweet spot for it.

 

[Pinewood Outlaw]

I hosted a race for a car racing club. My test car was my daughter's car from last year and hasn't been lubed since then. Her car weight 4.99oz and st the end of their race a guy with a outlaw car weighing 7.5oz wanted to race her car. Her car consistently beat the heavier car by 0.05 everytime.

 

[CFD Engineer]

Math states that the maximum weight would be best. (with all other variables being constant)
This lowers the fraction of energy that must go into spinning the wheels. It also means aerodynamic drag would have less effect at slowing the car down.

The difference between 5oz and 7oz is only 23 ms in my calculation script I wrote for a 42' best track. So I can see other variables changing could easily play a role as well.
Perhaps other variables are changing as well when people go for a heavier car? I'd like to know what, and why 6oz would be considered ideal?

 

[Chief]

That was talked about a very long time ago by OPA. I searched for him but had no luck. If my memory serves me well it was 6.25 oz that he found to be the fastest due to the weight bearing down on the wheels. I could be mistaken. Either way, if you are on this forum and you build a 6 oz unlimited car no one there will even come close to you

 

[Chief]

That was talked about a very long time ago by OPA. I searched for him but had no luck. If my memory serves me well it was 6.25 oz that he found to be the fastest due to the weight bearing down on the wheels. I could be mistaken. Either way, if you are on this forum and you build a 6 oz unlimited car no one there will even come close to you

Well I was incorrect, on OPA...he said with his bearing cars it was 7 to 7.5oz. Oh well ya know what they say...first to go is the memory...Funny, I dont remember that.

 

[Bubblegum]

I asked my daughter if she wanted to run a car for the districts and she said yes and to my surprise she wanted to run her car from the 2018 Mid America derby. We didn't do well. The car has not been touched since then and I decided to test weights so I stuck double sided tape on top and raced on my 35 ft best track. I did not clean the wheels nor did I graphite the wheels.

I ran the car 5 heats at each weight, took the average of the 5 runs, and compared this. I ran at 5.0, 6.0, 6.5, 6.8, and 7.0 oz.

The results were as weight increased, the time decreased and 7.0 oz was the fastest overall. The difference between 5.0 and 7.0 oz cars was 0.0204 seconds.

I did not have bearings just straight axles and no fenders.

On a side note my fastest time was heat 24 of 25 of the weight test and overall this car has had 30+ runs on graphite. The slowest run of the 7.0 oz car was 0.0126 sec slower than the average of this 5.

 

[CFD Engineer]

Thank you very much for running this real world test Bubblegum.
That concurs very well with my prediction of 23 ms faster for the 7oz vs 5oz car.
It's good to know that math and the laws of physics are still valid

 

[Bubblegum]

Thank you for running numbers and it is interesting that the results lined up for this.

I will have 4 cars at districts this weekend: 5 oz standard wb (don't like), 5.0 oz at 4.75 in., two 7.0 oz with extended wb of almost the entire car length.

It will be interesting to see how cars 2 to 4 do in the family/outlaw class(es).

I will post numbers etc. if the TV interfaces with the laptop this time and I can see something.