Posted: 1/20/2011 4:53:54 AM EDT
|
My son and I are building our first derby car.
Any tips you can offer would be great. |
|
Quoted:
Quoted:
Weight in the nose. Sand down the wheels so they're flat. The plastic rim from the press doesn't roll as well. (You could put them in a lathe like I did  )I always hear weight in the back. Something about more potential energy. PW cars run by gravity. The longer you keep the heavy part on the incline, the more potential energy is released, and the heaviest part starts further up the track. This gives it more energy to continue at better speeds on the flat. EVERY speed tip book and web page suggests that the weight be in the back. A good starting place is to have the center of gravity 1″ to 1½” in front of the rear axles. |
|
There's 2 ways you can do it.
1. Let the kid do it, offer minor assistance here and there. He learns that anytihng worth doing, is worth doing correctly. Most likely loses. 2. Do like all the other parents did when I was a kid, and build the thing for him. Spare no expense. Kid wins, but learns that mommy and daddy will do everything for them. and that's 100% my experience. I did the pinewood derby once, and it was a joke. You could clearly tell which ones were build by parents, and which ones were build by kids. |
|
Axles and wheels. At a minimum get rid of the little burrs at the head of the axle and polish them to a mirror finish. You can also buy a jig that ensures they are straight but I've never bothered with that, yet. Wheels as they come in the BSA kit are a good starting point. The bores need to be polished and you need to make sure they are round. I use a mandrel in my drill press to true up the wheels and polish them. Anything that kills friction is a good thing. Pay extra attention to the area where the head of the axle meets the wheel. If I had a metal working lathe you can guarantee I'd use it on both the wheels and axles. Make sure the tread areas of the wheels are polished to a mirror finish because friction is the enemy. Powdered graphite lube is essential. Alignment. Make sure the car rolls straight. I don't bother getting one wheel off the track although the theory behind it is sound. Body shape? I saw a fuzzy bunny slipper glued to a wood block dominate an Outlaw race one time. Aerodynamics are not as important as the axles and wheels. Weight. Very important. Build your car a tad bit light so you can super glue that last weight to the car on race day. I've seen cars fluctuate in weight due to humidity. Also consider the fact that that official scales might not match yours and they are the ones that count. I've never seen a parent win an argument with a track official over this one. Don't buy a pre-built car off the internet. Odds are the track officials will let the child race anyway with it but everyone in the Pack will know you are a cheat. Pinewood Derby is about a lot more than winning a dinky little trophy. And if you have any boys in the Pack who simply don't have anyone to help with their cars, be the guy who they can count on to get them in the race. That's what it's all about. |
|
Quoted:
There's 2 ways you can do it. 1. Let the kid do it, offer minor assistance here and there. He learns that anytihng worth doing, is worth doing correctly. Most likely loses. 2. Do like all the other parents did when I was a kid, and build the thing for him. Spare no expense. Kid wins, but learns that mommy and daddy will do everything for them. and that's 100% my experience. I did the pinewood derby once, and it was a joke. You could clearly tell which ones were build by parents, and which ones were build by kids. I let my kid pick the style and shape of the car and let him work on the block of wood with all the cutting shaping, sanding. Let him prep the car for painting, I sprayed it. Let him polish axles and wheels with drill, I finished with dremel. Let him assemble, and I assist with fine tuning. He won not only the pack races but also the district. Built one for my self BTW, they had dad races too. My dad did not even help me when I did mine, it rolled like crap. |
|
I built mine myself. I lost badly every time. The Internet wasn't there for me. Nothing like using a handsaw to make a wedge car and gluing the provided lead weights to it, only to show up with one kid having gone so far as to have recreated the bat-mobile perfectly. |
|
For the last two pinewood derby's that my son participated in, the big winners were cars with:
1. A low profile. Usually shaped like a narrow wedge. 2. The weight primarily more towards the back. 3. The wheel axles spread out as far from each other as possible. The winners generally disregarded the pre-cut axle positions and made their own further apart from each other. 4. The axles polished, of course. |
|
Quoted:
Weight in the nose. Sand down the wheels so they're flat. The plastic rim from the press doesn't roll as well. (You could put them in a lathe like I did )I helped built four last year (two boys and two friends with fathers who were not available). My observations: 1. Build the car however you want. Aerodynamics don't seem to matter. 2. Once built, add maximimum weight above the REAR wheels. This appears to keep gravity acting on the car a little longer than weight in the front. 3. Attached wheels carefully so they spin well. 4. Smoth out the axle pins before attaching. 5. Use the graphite on the wheels prior to race as legally permitted. "My" cars dominated. But what really matters is having a fun time. Let you son do as much as possible, and remember these days. |
|
Most of the tips have been said. I've never built one for myself but I worked in a machine shop and we helped alot of kids and dads that did not have tools at home.
turn and true the axles, polish them and lube them true the wheels, turn the flat tread area to a narrower profile and taper the back hub area to only a very small surface area touches the body. pre-drill the holes for the axles so you can press/tap them in straight We used to use lead as the weight, press fit into holes and then drill out the extra the day of the race by just twisting a drillbit by hand. The theory would say to put the mass as far back as possible to maximize energy to convert to velocity. That ignores aerodynamics, too much mass in the rear will cause the nose to pull up and possibly catch air and bounce or flip. I would assume the idea of having the cg 1=1.5 inches behind the front axle is a comprimise between energy and control so the car is not bouncing up and down and side to side off the rails. |
|
Quoted:
There's 2 ways you can do it. 1. Let the kid do it, offer minor assistance here and there. He learns that anytihng worth doing, is worth doing correctly. Most likely loses. 2. Do like all the other parents did when I was a kid, and build the thing for him. Spare no expense. Kid wins, but learns that mommy and daddy will do everything for them. and that's 100% my experience. I did the pinewood derby once, and it was a joke. You could clearly tell which ones were build by parents, and which ones were build by kids. He is doing the work, I'm not going to build the thing for him. If his car does well, great, if not he stil had fun making the car. I looked at a few of the websites where you can buy the special kits with the fancy stuff, it's not for us. |
|
Quoted:
There's 2 ways you can do it. 1. Let the kid do it, offer minor assistance here and there. He learns that anytihng worth doing, is worth doing correctly. Most likely loses. 2. Do like all the other parents did when I was a kid, and build the thing for him. Spare no expense. Kid wins, but learns that mommy and daddy will do everything for them. and that's 100% my experience. I did the pinewood derby once, and it was a joke. You could clearly tell which ones were build by parents, and which ones were build by kids. This |
|
Quoted:
Quoted:
There's 2 ways you can do it. 1. Let the kid do it, offer minor assistance here and there. He learns that anytihng worth doing, is worth doing correctly. Most likely loses. 2. Do like all the other parents did when I was a kid, and build the thing for him. Spare no expense. Kid wins, but learns that mommy and daddy will do everything for them. and that's 100% my experience. I did the pinewood derby once, and it was a joke. You could clearly tell which ones were build by parents, and which ones were build by kids. This I'm considering a third option: I've already let my kid do it his way twice. The result being that he's done OK (probably better than any of my cars I ran as a kid) but never come close to the winning times, either. Now I'm tempted to do it my way this next year just so he can have a winning year once before I let hiim go back to doing his own way again. 
|
|
Put the axles in a drill, take a 4" by 1/2" strip of 600 grit sandpaper, add a few drops of militec, some graphite, and hit the trigger for 1 minute on each axle.
File the OD of the hub while it's on the drill as well. I put a button of superglue mixed with powdered graphite directly over the axle slot on the car body - keeps the wheel from rubbing on bare wood/paint. 1 wheel off the track isn't hard to do, just cut one of the front axle channels a mm or two higher. My 7 yo helped with everything, but it's pretty obvious Dad had a hand in the build ... 
|
|
Quoted: My son and I are building our first derby car. Any tips you can offer would be great. Yeah. Have your kid build it. Supervise for safety only. If the kid wants to win, he needs to win from his own ingenuity. If not, he didnt really win. Too many people these days prohibit their kids from being self sufficient. No wonder we are a nation of spiled babies who expect everything. |
|
Quoted:
There's 2 ways you can do it. 1. Let the kid do it, offer minor assistance here and there. He learns that anytihng worth doing, is worth doing correctly. Most likely loses. 2. Do like all the other parents did when I was a kid, and build the thing for him. Spare no expense. Kid wins, but learns that mommy and daddy will do everything for them. and that's 100% my experience. I did the pinewood derby once, and it was a joke. You could clearly tell which ones were build by parents, and which ones were build by kids. A lot depends on the age, too. My son just turned 7. He can't do all the cuts with a coping saw, and the power saws and routers are out of the question for him. He got to use the drill press a lot, and is doing sanding and painting himself. He wanted it to look just like Gravedigger, so I got the body looking right then had him finish it. We sat together and read the book on how to make it faster and he's excited to know the "secrets." Each year he'll get to do more and more on his own, but he is definitely learning! Someone with a 6-7 year old is going to be giving a lot more assistance than someone with a 13 year old. |
|
Quoted:
I built mine myself. I lost badly every time. The Internet wasn't there for me. Nothing like using a handsaw to make a wedge car and gluing the provided lead weights to it, only to show up with one kid having gone so far as to have recreated the bat-mobile perfectly.  That happens.
|
|
My kids are only eight. They don't get to use the powered shop tools any time soon. I also don't want to load them down with tons of sanding because the idea is to keep it fun. Right now I'm working on #1's car. He hangs with me in the shop and does the simple little tasks like light sanding, polishing axles, and learning how to use the power tools from Dad. It's a great time but I'd be lying if I said the boy was building his own car. Once we get to the finishing phase he'll be pretty much on his own this year. Same goes for #2 but his build is going to be kind of wild and won't really take as much time as carving a car from scratch. The kid in my Webelos Den I'm going to help is getting your basic garden variety streamliner. I'm just going to taper it with a table saw and have him sand it smooth, a few coats of lacquer to smooth it out and he can spray it whatever color floats his little boat. The axles, that's where we're going to really pay attention. He'll also get a set of trued wheels made. |