My son's 2003 winning car (Updated pic)

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terryep
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My son's 2003 winning car (Updated pic)

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This is my son's 2003 winning car. He called it Formula1. It has a plastic air foil on the front and a metal foil on the rear. (For looks only) It's jet engine is an axially mounted 5/8" steel rod which serves to weight the car. It uses the stock axle slots but the back end is shortened to move the center of gravity higher up the starting ramp. Lubricated with "Slick n' Shine" silicone spray.

His previous year's car was called Stinky (a Skunk motif). It was a full size black and white block with a slanted front end. Looked like a WWII landing boat. We were real surprised to win district. It used graphite lube.
Last edited by terryep on Fri Mar 26, 2004 7:10 pm, edited 1 time in total.
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Re: My son's 2003 winning car (Updated pic)

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Are there any other winning cars out there that are not wedges? 8)

Terry
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Re: My son's 2003 winning car (Updated pic)

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My son built a 'Batmobile' last year which was really cool (at least to dad). I plan on getting pictures posted soon.

I notice that you mentioned the back is shortened on your sons car. Have your seen MaxV's current newsletter where Michael L talks about a short front nose being bettter? I'm trying to figure that one out. :rockedover:
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Re: My son's 2003 winning car (Updated pic)

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Yes, the results presented in MaxV's news letter was interesting reading for sure. Our district rules require we use the original axle slots so changing the wheel base was not an option.

Terry
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Re: My son's 2003 winning car (Updated pic)

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Den_Leader wrote: I notice that you mentioned the back is shortened on your sons car. Have your seen MaxV's current newsletter where Michael L talks about a short front nose being bettter? I'm trying to figure that one out. :rockedover:
I must've missed that one. What was the explanation?
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Re: My son's 2003 winning car (Updated pic)

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I must've missed that one. What was the explanation?
Michael didn't fully explain it, but his testing found that long nosed cars tend to not perform as well as short nosed cars. But note, this factor cannot be taken in isolation. Rear-weighted cars perform better than front weighted cars, so moving the axles slots towards the rear (but keeping the same spacing) still may be better because of the latter factor. But you certainly don't want to increase the nose length by moving the front axle closer to the rear axle (thus shortening the wheelbase).
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Re: My son's 2003 winning car (Updated pic)

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MaxV wrote:
I must've missed that one. What was the explanation?
Michael didn't fully explain it, but his testing found that long nosed cars tend to not perform as well as short nosed cars. But note, this factor cannot be taken in isolation. Rear-weighted cars perform better than front weighted cars, so moving the axles slots towards the rear (but keeping the same spacing) still may be better because of the latter factor. But you certainly don't want to increase the nose length by moving the front axle closer to the rear axle (thus shortening the wheelbase).
Randy, let's say you have a situation where you can't extend the wheelbase and you have to use the slots provided in the block. Would it be advantageous to cut the back off the car and glue it to the front? You'd have a more back-weighted car, but a longer nose. Have tests been done to compare an untouched wheelbased verses a car with the back cut off and glued to the front?
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Re: My son's 2003 winning car (Updated pic)

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Gavin Chafin wrote:...you can't extend the wheelbase and you have to use the slots provided in the block. Would it be advantageous to cut the back off the car and glue it to the front?
I'm not aware of any published tests on this matter.

But... Here's my $0.02

Assumptions:
1: Car A uses stock axle slot dimensions from each end of the block
2: Car B has the area behind the rear axle is shortened by 5/16"
3: Original axle slots are used on A and B.
4: Total car length is 7" when finished on A and B.
5: Weight material placement is as far back as the builder can achieve for A and B.

By moving the portion of the mass that would have been behind the rear slot to a position that is in front of the rear slot, the CM on Car B has to shift forward by some distance. This results in some additional weight on the front wheel. This should assist in stability.

The forward shift in the CM will not be a full 5/16" and the position of the CM in Car A will not be as far up the track as Car B when looking at the initial PE. Car A will have less PE than Car B at the start.

IMHO this seems like a win-win scenario if you keep the new front end as light as possible and the weight near the rear slot.

I’ll take Car B. :)
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Re: My son's 2003 winning car (Updated pic)

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By my calculation car B will have a 0.022 second lead at the line (about 4 inches at 16feet/sec). This assumes the same CM distance from rear axle. 32 foot track, 4 foot rise, and no frictional losses.

Stan helped me refine an Excel spredsheet for these cases around the time we were arguing about raised CMs

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Re: My son's 2003 winning car (Updated pic)

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terryep wrote:By my calculation car B will have a 0.022 second lead at the line (about 4 inches at 16feet/sec). This assumes the same CM distance from rear axle. 32 foot track, 4 foot rise, and no frictional losses.

Stan helped me refine an Excel spredsheet for these cases around the time we were arguing about raised CMs

Terry
Now that you have computations of your own to serve as a check, try Michael's Engr. Sim program.

BTW, I love the look of the car... it passes my "looks like it was built by a youngster" test with flying colors! Gavin's son's car (the dark yellow or gold colored rail) had some of that same look... some irregularities in the left front rail, and other signs that a youngster's hands produced the car.
Stan
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Re: My son's 2003 winning car (Updated pic)

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terryep wrote:By my calculation car B will have a 0.022 second lead at the line (about 4 inches at 16feet/sec). This assumes the same CM distance from rear axle. 32 foot track, 4 foot rise, and no frictional losses.

Stan helped me refine an Excel spredsheet for these cases around the time we were arguing about raised CMs

Terry
That's quite significant. We might have to try and experiment around again with that next year.
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Re: My son's 2003 winning car (Updated pic)

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Thanks Stan, don't cringe, I rough cut this car on a table saw! That's a good enough reason for my wife to make me get a band saw!

I expect the lead to be less with Michael's program since he probably uses some friction coefficients. The CM on this car is above the wheel plane, this year Mark will try a lead plate suspended beneath the car and a lower frontal cross section unless he comes up with something more interesting (I hope)

Terry

If anyone is interested in the spredsheet let me know. It could serve as a starter for a more involved analysis.
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