Unlimited class next year- what are my opions since I'm new

[FatSebastian]

I put this in another post

Impressive!

World Record?!? Seems rather an outlandish and unverifiable claim.

... especially considering that the car has a "starting device" against the customary BSA rules that typify the competition known as the "Pinewood Derby". (It also appeared to race on a 32' track, which is relatively short compared to this purely gravity powered design which timed 40' in 1.74 seconds; it would be entertaining to see these two designs raced against each other!) The phrase "World's Fastest" or "World Record" will return some interesting hits via Google (including a less-elegant but still effective CO2 firing mechanism), although this seems like an entertaining, lower-tech approach:

https://youtu.be/

Why a dual outlet though...I'd question better thrust with a single outlet, but maybe he was shooting for a tamer solution.

At the speeds this car was traveling, it might have made sense to reduce wheel inertia and streamline the body as much as possible. I might therefore guess that the dual exhaust was for looks, like other stylish elements of the car.

[Speedster]

Cubmasterbob, you build the chassis. It consists of 4 pieces. There are 2 pieces of 1/4" brass tubing and 2 slot car motor mounts that also hold the axles. That's the chassis. You make the length to fit the wheel openings on whatever body you are going to attach to it. The body is for looks. You could tape the battery on top of the speed control and run it down the track that way if you so choose. The slot car people make it really easy for us with the "motor mount/axle mount" as one piece. Everything simply falls together. I had to use the smallest ring gear and purchased the tallest tires offered by the slot car folks. You have to make the ring gear clear the center guide strip. I finally ended up cutting broccoli rubber bands and gluing them on the rear tires. That gives me plenty of clearance and SUPER grip. If you are running on an aluminum track where the center guide is not solid, you are very fortunate and won't face this problem.
There's a picture of the underside of the McD's car in this post. If you look at that and look at the attached drawing I think it will be clear how the car was constructed.
Do you think I should get a patent on this chassis? Maybe call it, "Chassis by Willie". Ha, Ha.
Cheers
Bill

[Speedster]

Hello, Everyone. I'd like folks thoughts.
Let me start off by saying, "I'm not so sure I cannot beat a Rocket car."
That being said, here's why. There's no way a Rocket car could beat a slot car and I can't either. I'm going to guess most folks think it's the speed. Speed is not the problem. I have a very powerful motor in McD's but it is not the ultimate. I have a Mamba brushless motor in one of my Mini-T's. A Mini-T was clocked at 65 MPH and its acceleration is awesome. There are many ring and pinion combinations for slot cars. The only problem I see is keeping the car on the track but the rocket has the same problem, sort of. The RC car will ride the rail even though both back wheels are pushing. I figured I will have Sporty machine me a perfect BSA wheel and that one will ride the rail. Think about the start. Let's say it's done by remote and the pins drop away instantly. I'm standing with my finger on the trigger staring at the start. The pin drops, I squeeze the trigger, and the car reaches top speed in the first few feet. There is no tire spin because of the grip of the slot car tires, or in my case, the rubber bands, and it's going downhill. If the rocket car takes a split second for its mechanism to fire the rocket, I'm across the finish line.. Even if we start out together, I think it takes a rocket car a moment in time to get going. I'm also not so sure the rocket car reaches as high a speed as I do.
If I had my choice I'd like to race on a 42' aluminum track that had a full arc, not like the Best track. Perhaps this summer we can make it happen. If the track could be set up outside I'll keep the power on and run the car off the end of the track.
I think it would be an exciting race. Does anyone have a track like I described and be willing to let us use it?
Cheers
Bill

[knotthed]

How about this for an unlimited?

Ran across it last year when I first started exploring derby stuff online.

http://www.et.byu.edu/~wheeler/benchtop/xderby.php" target="_blank

Wild!

[FatSebastian]

Ran across it last year when I first started exploring derby stuff online.

Yes, that one appears to be a classic!

[FatSebastian]

I'd like folks thoughts. [...] I think it takes a rocket car a moment in time to get going. I'm also not so sure the rocket car reaches as high a speed as I do.

According to its thrust curve, a 1.07-ounce C6-0 rocket engine will generate a peak thrust of 4.9 lbs within 0.3 seconds, averaging 2.44 lbs force over its 0.8-second burn duration. For, say, a 2.5 ounce rocket car, the average thrust-to-weight ratio (T/W) would then be about 15.

Think about the start. [...] Perhaps this summer we can make it happen.

Because the vehicles being discussed need not be propelled by gravity, there is seemingly no requirement for a conventional PWD track with an elevated starting gate. It may suffice to lay out lengths of 1x4 employing 1-5/8" x 1/4" lath (or, say, strips of ripped masonite) as a guide rail. To eliminate driver reaction delays, etc., a laser gate or other starting sensor could sense when the car has started to move. Cars would then race against the clock one at a time, rather than head to head.

[Speedster]

Mr. FS, you are The Man.
I would prefer the lattice strip to get the full 1/4" height since I depend on it. I think 1/4" x 1 1/2" is a standard size which would save the cost and work cutting it down if that would be acceptable to the rocket cars. It would be more exciting to spectators if we go head to head and that technology already exist. Are there not some aluminum tracks where the start end could be raised just enough simply to clear the start mechanism? Neither of us would then have to be concerned about the curve. That gives me my advantage back of the slow start of the rocket car. Ha, Ha. For strictly speed and Elapsed Time over a given course, your way is best and I'd be happy to do it. I'm presently building a vehicle and equipping it with my Mamba brushless motor. What length track would you say would give a rocket car the best time? That's the length we should use. When I know the length I will extend my 32' track, move the timer, and then set up the gearing for the best elapsed time. Even though I will have a manual start it will still give me an idea for the best gears.
Are there any Rocket cars in your area? I'll write to Micro Wiizard to see if this Start mechanism already exist. Maybe we can simply use my track.
Thanks for all your info.
Cheers
Speedster

[cubmasterbob]

I stopped by the LHS{local hobby shop} yesterday since it was on the way home from the scout shop{needed to set up an account there and grab some segments for the kids}...anyway, turns out those AMT slot cars are center drive...so the '66 nova kit followed me home{reminded me of my old '67 I had long ago}. I also bought a full set of 4 losi micro ralley wheels for their height{1 3/8"}. Problem is they're treaded tires so I'll have to sand a pair down to make them slicks...should be tall enough even after that{I hope}. Carrera makes a 30k rpm 12v motor but it doesn't mount the same way as the amt does...I might try one anyway after I get the chassis built up. I need to find out what the voltage useage is for the amt motor so I can compare them as well as other possible motor options, but I'll also want to try her stock too to see just how fast it is out of the box.
I'm looking to run sans RC equipment not only to reduce clutter but also to keep it really simple{KISS}...I'm leaning towards two 5v capacitors like they use for the duct fan cars, depending on my needed motor voltage, and making up separate start and stop switches...momentary contact on the starting pin for going and another locking switch for shutting the system off at the track's end. A light 11.2v LiPoly pack is another power option I suppose. I'll worry about a 1/25 scale body when the rolling chassis is done...I have quite a few kits here to choose from luckily.... it'll simply be a matter of size and required room and car brand taste.