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Lead part - cast or turn?
I need to make some custom shaped lead weights that must be balanced
and fit precisely inside a small plastic wheel, the kind you might find on a pinebox derby car. I've tried making a casting of the inside of the wheel to use as a pattern so I could make molds of the part and cast them out of lead, but I've tried using plaster of paris, wax, clay and lead to cast the pattern. Plaster of parris disintegrates when I try to remove it from the wheel, as does the clay when allowed to dry. The wax and wet clay deform horribly when I remove them from the wheel. The best success I has was lead, but the hot lead did melt the plastic wheel enough to deform it. When I made the final lead castings, they were still deformed enough to deform the wheel when inserted. This and the fact that the weights were unbalanced lead to a speed destroying oscillation. If I can cast a better patters, I should be able to case weights that are a lot more accurate then use the lathe to finish them, but I've still got to figure out the balancing part, and, how dangerous would the lead chips be? I also thought about just turning a lead cylinder of the correct size and boring out the center, then slicing it up into the individual weights. Any suggestions on getting this done right? |
Lead part - cast or turn?
Okay try this...
Use putty style silicone mold material (it mixes by squishing it together). Put the mixed material into the wheel and let set (about 10 mins). Remove model once set by simply pulling it out. Now use this mold to create another mold using more of the putty. Simply put it on a flat surface, mold the new lump over it and let set. (Oh side note, powder the model or it might stick permanently to the mold body.) You should now have a mold of the correct dimensions of the wheels inner spaces ready to receive molten lead (or lead free white metal/pewter) that can withstand the low heat and be reused a great many times. "tillius" wrote in message ups.com... I need to make some custom shaped lead weights that must be balanced and fit precisely inside a small plastic wheel, the kind you might find on a pinebox derby car. I've tried making a casting of the inside of the wheel to use as a pattern so I could make molds of the part and cast them out of lead, but I've tried using plaster of paris, wax, clay and lead to cast the pattern. Plaster of parris disintegrates when I try to remove it from the wheel, as does the clay when allowed to dry. The wax and wet clay deform horribly when I remove them from the wheel. The best success I has was lead, but the hot lead did melt the plastic wheel enough to deform it. When I made the final lead castings, they were still deformed enough to deform the wheel when inserted. This and the fact that the weights were unbalanced lead to a speed destroying oscillation. If I can cast a better patters, I should be able to case weights that are a lot more accurate then use the lathe to finish them, but I've still got to figure out the balancing part, and, how dangerous would the lead chips be? I also thought about just turning a lead cylinder of the correct size and boring out the center, then slicing it up into the individual weights. Any suggestions on getting this done right? |
Lead part - cast or turn?
Okay try this...
Use putty style silicone mold material Thanks. I'll google up the right material and order some so I can give it a try. Tillman |
Lead part - cast or turn?
Why would you want to weight the wheels of a Pinewood Derby car? Adding
weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... -- Bob (Chief Pilot, White Knuckle Airways) "tillius" wrote in message ups.com... I need to make some custom shaped lead weights that must be balanced and fit precisely inside a small plastic wheel, the kind you might find on a pinebox derby car. |
Lead part - cast or turn?
Why would you want to weight the wheels of a Pinewood Derby car? Adding
weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... Because the track we run on has a very long runout at the bottom of the slope. I was thinking that the rotational inertia would cause the wheel's RMP's to decay slower on the straight away. That, and moving the weight from the body to the wheels would decrease the friction between the wheel axels and the wheels. I may be wrong, but since we've got another year to prepare, I was thinking we could set up a small test track in the basement and try different configurations. It would make a great science project for the kids as well. BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Tillman |
Lead part - cast or turn?
tillius wrote:
Why would you want to weight the wheels of a Pinewood Derby car? Adding weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... Because the track we run on has a very long runout at the bottom of the slope. I was thinking that the rotational inertia would cause the wheel's RMP's to decay slower on the straight away. That, and moving the weight from the body to the wheels would decrease the friction between the wheel axels and the wheels. I may be wrong, but since we've got another year to prepare, I was thinking we could set up a small test track in the basement and try different configurations. It would make a great science project for the kids as well. BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Tillman You might want to try some of that "fixturing alloy" you can get from MSC/Enco/McMaster. Since it melts at such a low temp you might be able to directly cast it into the plastic wheels. Pete C. |
Lead part - cast or turn?
As a former Cub Scout pack Master I must advise you that modifying the
wheels other than truing the roundness is not legal. We added unlimited top fuel and funny car classes for the dads that couldn't resist meddling to much in their Cub's design. :-) -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "tillius" wrote in message ups.com... Why would you want to weight the wheels of a Pinewood Derby car? Adding weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... Because the track we run on has a very long runout at the bottom of the slope. I was thinking that the rotational inertia would cause the wheel's RMP's to decay slower on the straight away. That, and moving the weight from the body to the wheels would decrease the friction between the wheel axels and the wheels. I may be wrong, but since we've got another year to prepare, I was thinking we could set up a small test track in the basement and try different configurations. It would make a great science project for the kids as well. BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Tillman |
Lead part - cast or turn?
Pete C. wrote:
You might want to try some of that "fixturing alloy" you can get from MSC/Enco/McMaster. Since it melts at such a low temp you might be able to directly cast it into the plastic wheels. Yeah... but you'll still need to machine it in place to balance. And don't let the cub scout handle the stuff unsupervised - same goes for the lead really. 4 wheel weights of lead may easily exceed the 5 oz limit... what about using some more ordinary engineering material such as free-machining brass? |
Lead part - cast or turn?
|
Lead part - cast or turn?
4 wheel weights of lead may easily exceed the 5 oz limit... what about
using some more ordinary engineering material such as free-machining brass? I ws thinking of only weighting the two rear wheels, since real location of weight has the greater potential energy. The samples we did in testing this year, we were able to get up to 5 oz by just weighting the rear wheels. Tillman |
Lead part - cast or turn?
As a former Cub Scout pack Master I must advise you that modifying the
wheels other than truing the roundness is not legal. Well, it's not really Cub Scout pinebox, it's AWANA Grand Prix. Same cars, etc. And you can't modify the wheels here either, but you can place the wieght anywhere you want on the car. My test car passed the legal check this year. Tillman |
Lead part - cast or turn?
for the dads that couldn't resist meddling to much in their Cub's design
Oh yeah, other than casting the weights, putting the weight into the car when we weighted their original designs, and the bandsawing, my kids do all the work themselves, I like to offer suggestions, but then they have to do it and test it and make the final decisions. They learn a lot more that way. Tillman |
Lead part - cast or turn?
tillius wrote:
Why would you want to weight the wheels of a Pinewood Derby car? Adding weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... Because the track we run on has a very long runout at the bottom of the slope. I was thinking that the rotational inertia would cause the wheel's RMP's to decay slower on the straight away. You might just be onto something there. I'm thinking that maybe if the car accelerates slower but rolls further because of that rotational inertia in the wheels, then the overall energy losses due to air resistance drag effects should be less than if the car reached higher velocity during its run. That, and moving the weight from the body to the wheels would decrease the friction between the wheel axels and the wheels. Now that seems like it might work too. I may be wrong, but since we've got another year to prepare, I was thinking we could set up a small test track in the basement and try different configurations. It would make a great science project for the kids as well. I sure hope you'll post the results here, I'm fascinated. BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Tillman I'm remember back 30+ years or so when I too was the "engineering support" for our two son's Cub Scout Pinewood Derby efforts. Being the only engineer father in a troop of kids with mostly doctor and lawyer dads*, it was like shooting ducks in a barrel and the kids' cars always brought home the bacon. We weighted the cars with lead to within a quarter of a gram of the legal limit, I made the kids a "calibration weight" out of screws and nuts in a small glass jar adjusted on a lab scale at work. I still remember the kids getting a useful lesson in "positional authority" when the guy running the Pinewood Derby one year put one of my kid's cars on the POS kitchen scale he was using, with no standard weight on hand, and judged it was heavy by about an eighth of an ounce. It wasn't worth making a row about in front of a bunch of youngsters, but I did speak to the guy privately later in the evening and asked him if he'd like to bet me $100 for charity that an accurate scale would prove my kid's car was under the weight limit. He mumbled something about having to go by the scale he was given and slunk away. I'm assuming they are a little more sophisticated about weighing the cars these days. Am I right? Jeff * The only reason we could afford to live where the doctors and lawyers did back then was because I could fix our cars, house and everything else the family owned (save for medical problems) while the other guys had to shell out for all of those things. I'm still enjoying living that way. G -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "Truth exists; only falsehood has to be invented." |
Lead part - cast or turn?
tillius wrote:
I need to make some custom shaped lead weights that must be balanced and fit precisely inside a small plastic wheel, the kind you might find on a pinebox derby car. This is pretty interesting! Keep us posted on the results. |
Lead part - cast or turn?
On 7 Nov 2005 07:56:27 -0800, "tillius"
wrote: Why would you want to weight the wheels of a Pinewood Derby car? Adding weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... Because the track we run on has a very long runout at the bottom of the slope. I was thinking that the rotational inertia would cause the wheel's RMP's to decay slower on the straight away. That, and moving the weight from the body to the wheels would decrease the friction between the wheel axels and the wheels. I think it's a bad idea to weight the wheels but go ahead and try it. Experimenting with these things is good for the kids. I'm still disappointed that the local club did away with the unlimited adult class. It was a lot of fun and allowed the kids to learn. Of course part of the reason they outlawed it was because of me. I always had some outrageous design which looked sure to win. The funny thing is that only one of my cars ever won the race and it was a powered car thrown together in about 30 minutes just before the race. I never had a lot of time to work on many of them since I was also in charge of setting up the track and much of the other work that went into the race. The powered car was simply sawed out quickly on a chop saw to get rid of excess wood. Gutted a old VCR for the motor and friction tire to run on one of the car wheels. Clipped three 9volt batteries together. Wire a on and off switch and a micro switch on the front for the starting gate to keep the motor off till the gate dropped. Some sheet metal and screws to mount the motor and a bunch of hot melt glue to hold everything else. That car won the race. Funny though they never did have a unlimited class race after that. :-) But it sure was fun to race the 5 lb ball bearing wheeled car even if it never did win. I took a piece of 1 1/4" pipe. Forged one end to look kind of like a DC-3 nose. Put steel axles through the middle. Filled full of lead (and I mean full with the car being the max length allowed). Made wheels for masonite pressed over ball bearings. That car made everybody stand up and notice. But it never won a single race even after I melted all the lead out to reduce it's weight. It did great on the straight away but took way to long getting up to speed on the slope so it always lost. The first year I lost to a guy who took his old cub scout propeller driven rocket and made a base for it. He used standard derby wheels and filled the base full of lead. But the prop gave him enough of a boost to beat me. After they outlawed the unlimited class I concentrated on design. Helping my daughter come up with designs that brought home at least one trophy a year (some years we brought home 2 or 3 what with the adult class and more than one car entered into it). In fact some cars just kept bringing home trophies for years since we'd enter the old cars into the adult class (we had to pay to do it so it was for a good cause). The last few years the local Awana's club has gone to the boat races instead of the cars. In this case we kept bringing home race trophies since I taught my daughter how to blow them properly plus I always streamlined the boats. In fact my standard design for the boats is a tri-maran with much lower water friction that most boats. But we never got a design trophy for any of them. Looks like I won't have to worry about that this year though. Since my daughter got older and decided to not do Awana's this year. I may end up being roped into the race again though since the water trough tracks are stored at my place (I built them from my own money). Actually the finish gate for the car track was built by me as well though somehow it ended up being stored somewhere else the last year or two of the race. I may be wrong, but since we've got another year to prepare, I was thinking we could set up a small test track in the basement and try different configurations. It would make a great science project for the kids as well. Sounds great to me. BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Moly is what you want in powdered form. Harder to find than graphite but much slicker. Wayne Cook Shamrock, TX http://members.dslextreme.com/users/waynecook/index.htm |
Lead part - cast or turn?
I'm assuming they are a little more sophisticated about weighing the
cars these days. Am I right? Yep, every car is weighed on the same digital scale which is calibrated from use to use with a 'standard' 5 oz weight to make sure it's calibrated the same no matter which day the kids register their cars. Cars also have to be registered no later than 1 week before the race and they are confiscated until race day. The guy in charge doesn't have any kids so their's no partiality involved. And if one of the kids car is over weight or under weight, we have a few drill presses setup and either one of the volunteers can adjust the weight or one of the kids parents can. And I'll be happy to post the results once we start testing. Tillman |
Lead part - cast or turn?
Wayne Cook wrote:
On 7 Nov 2005 07:56:27 -0800, "tillius" wrote: snipped Looks like I won't have to worry about that this year though. Since my daughter got older and decided to not do Awana's this year. I may end up being roped into the race again though since the water trough tracks are stored at my place (I built them from my own money). Actually the finish gate for the car track was built by me as well though somehow it ended up being stored somewhere else the last year or two of the race. Never fear, you can always move on to belt sander drag racing. http://users.rcn.com/markt.dnai/lett...beltsander.htm I think I've heard they also have chain saw and other power tool drag racing events too. Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "Truth exists; only falsehood has to be invented." |
Lead part - cast or turn?
Heh, my design this year had a high spoiler in the front then swept
straight back to drop down just before the wheels. The spoiler rested against the starting pin, but as soon is it cleared, my car was rolling before the pin cleard the fronts of the other cars. I'm hoping not too many noticed it, my son wants to incorporate that into his car next year. Tillman |
Lead part - cast or turn?
Dave Hinz wrote:
On 7 Nov 2005 08:49:09 -0800, wrote: Pete C. wrote: You might want to try some of that "fixturing alloy" you can get from MSC/Enco/McMaster. Since it melts at such a low temp you might be able to directly cast it into the plastic wheels. Yeah... but you'll still need to machine it in place to balance. And don't let the cub scout handle the stuff unsupervised - same goes for the lead really. Well, let's be realistic. Handling lead isn't going to make 'em start twitching. 4 wheel weights of lead may easily exceed the 5 oz limit... what about using some more ordinary engineering material such as free-machining brass? Drill holes in the underside of the body with a spade bit, and cast the lead directly into them. Drill to reduce to legal weight. I believe the "fixturing alloy" currently sold by MSC and Co. is lead free. Pete C. |
Lead part - cast or turn?
"Pete C." wrote in message ... Dave Hinz wrote: Drill holes in the underside of the body with a spade bit, and cast the lead directly into them. Drill to reduce to legal weight. When my son cubbed, we drilled out his pinewood body, and filled it with #7 shot, with a quick-release "Moog Headers" decal over the hole, so we could reduce the weight if the officials' scales weren't exactly the same calibration as ours. I engineered, but the kid actually did the cutting. LLoyd |
Lead part - cast or turn?
On Mon, 07 Nov 2005 19:44:56 GMT, Pete C. wrote:
Dave Hinz wrote: Well, let's be realistic. Handling lead isn't going to make 'em start twitching. Drill holes in the underside of the body with a spade bit, and cast the lead directly into them. Drill to reduce to legal weight. I believe the "fixturing alloy" currently sold by MSC and Co. is lead free. And therefore significantly lighter. I'll repeat my statement that, while lead is a hazard, it's certainly a manageable one. Overreacting isn't the lesson to teach on this one - if anything, it's a great way to teach "Yes, this could be a hazard, so to avoid problems we do (this, that, the other)". Dave Hinz |
Lead part - cast or turn?
if anything, it's a great way to teach "Yes,
this could be a hazard, so to avoid problems we do (this, that, the other)". Yep. Same thing when it comes to firearms. My dad, begin an excellent gunsmith as well as a phenomenal tool and die man, always had guns in the house, in various stages of repair and fully functional. I shot my first rifle (.22) when I was 4. My first handgun when I was 6. Dad always had the policy that if you wanted to shoot, just ask and he'd take you shooting, but if we EVER touched a gun without his immediate authorization and supervision, we'd not be touching one for a long, long time. We'd probably not be sitting down for a bit longer than that too. Worked for me and my sister. My oldest shot his first rifle at 4, same .22 that was mine. We've got the same policy for swords (he's got a nice collection of them he really enjoys looking at and showing of) as well as their bows. My son was at a friends house and his friend found a pistol (had a trigger lock and wasn't loaded). My son asked to hold it and took it straight to his friends dad. :) Teach 'em proper handling of dangerous things and they'll be a lot safer than if you isolate them. Tillman |
Lead part - cast or turn?
In article ,
Wayne Cook wrote: BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Moly is what you want in powdered form. Harder to find than graphite but much slicker. Look for "Jet Lube", mostly moly but probably slicker, especially if your bearings are a tad loose. -- Free men own guns, slaves don't www.geocities.com/CapitolHill/5357/ |
Lead part - cast or turn?
In article ,
Dave Hinz wrote: Drill holes in the underside of the body with a spade bit, and cast the lead directly into them. Drill to reduce to legal weight. Or just drill a bunch of 5/16" holes and epoxy 30 cal cast bullets in them. -- Free men own guns, slaves don't www.geocities.com/CapitolHill/5357/ |
Lead part - cast or turn?
On Mon, 07 Nov 2005 22:01:10 GMT, Nick Hull wrote:
In article , Dave Hinz wrote: Drill holes in the underside of the body with a spade bit, and cast the lead directly into them. Drill to reduce to legal weight. Or just drill a bunch of 5/16" holes and epoxy 30 cal cast bullets in them. That'd work too. The idea about lead shot is a good one, though, as it allows last-minute weight adjustments for when the scales are wrong. |
Lead part - cast or turn?
Dave Hinz wrote:
On Mon, 07 Nov 2005 19:44:56 GMT, Pete C. wrote: Dave Hinz wrote: Well, let's be realistic. Handling lead isn't going to make 'em start twitching. Drill holes in the underside of the body with a spade bit, and cast the lead directly into them. Drill to reduce to legal weight. I believe the "fixturing alloy" currently sold by MSC and Co. is lead free. And therefore significantly lighter. I'll repeat my statement that, while lead is a hazard, it's certainly a manageable one. Overreacting isn't the lesson to teach on this one - if anything, it's a great way to teach "Yes, this could be a hazard, so to avoid problems we do (this, that, the other)". Dave Hinz Wasn't my point though. I suggested it due to the very low melt temp which should be more compatible with direct application to plastic wheels. Lead free is just a side benefit. Pete C. |
Lead part - cast or turn?
In article , Jeff Wisnia says...
Never fear, you can always move on to belt sander drag racing. http://users.rcn.com/markt.dnai/lett...beltsander.htm Heh. What *will* they think of next! The beer bottles visible around the pit areas indicate a certain relaxed attitude while working with high-speed vehicles though. :^) Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Lead part - cast or turn?
On Mon, 07 Nov 2005 13:47:22 -0500, Jeff Wisnia
wrote: Wayne Cook wrote: On 7 Nov 2005 07:56:27 -0800, "tillius" wrote: snipped Looks like I won't have to worry about that this year though. Since my daughter got older and decided to not do Awana's this year. I may end up being roped into the race again though since the water trough tracks are stored at my place (I built them from my own money). Actually the finish gate for the car track was built by me as well though somehow it ended up being stored somewhere else the last year or two of the race. Never fear, you can always move on to belt sander drag racing. http://users.rcn.com/markt.dnai/lett...beltsander.htm I think I've heard they also have chain saw and other power tool drag racing events too. I've wanted somebody to get that started during our St Patricks celebration here. I know of one other guy who would be interested in it. I'm not sure of anybody else which is going to be the problem. Wayne Cook Shamrock, TX http://members.dslextreme.com/users/waynecook/index.htm |
Lead part - cast or turn?
On Mon, 07 Nov 2005 13:47:22 -0500, Jeff Wisnia
wrote: Wayne Cook wrote: Never fear, you can always move on to belt sander drag racing. http://users.rcn.com/markt.dnai/lett...beltsander.htm Been there done it :-) The place is Kenyon Woodworking in Jamaica Plains Ma. Four of us from Maine head down there once year or so to compete in some type of annual race. Usually have thirty or so racers and manyyyyyyyyyyy more spectators. They have a 75' foot track set up just like a drag strip. Three of us four run in the "modified class" I run a Makita 4x24 with twin motors. Usually get a trophy or end up breaking something on the sander in the process. Under two seconds to go 75 feet when its tweaked right, turning some pretty good rpm's. Ten dollar entry fee to race, I'st, 2nd and third is good for a trophy and some cash in both stock and modified classes. Spectators get in free, Samual Adams beer is supplied free.......... their brewery is in the same complex as the wood shop and a pallet of various samples of their ale is supplied. It can get a bit touchy as the day progresses... Power tools and beer open belts, chains and such with no guards.... Luckily the racers are more into racing than drinking. Hmmmm Halloween is past and no race.......... maybe super bowl weekend, Where is my sander? Need to check that puppy out. |
Lead part - cast or turn?
"tillius" wrote in message ups.com... Why would you want to weight the wheels of a Pinewood Derby car? Adding weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... Because the track we run on has a very long runout at the bottom of the slope. I was thinking that the rotational inertia would cause the wheel's RMP's to decay slower on the straight away. That, and moving the weight from the body to the wheels would decrease the friction between the wheel axels and the wheels. I think you could mix lead shot with epoxy and fill each cavity. To balance you could just subtract from the heavy side. I may be wrong, but since we've got another year to prepare, I was thinking we could set up a small test track in the basement and try different configurations. It would make a great science project for the kids as well. BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Why not buy mechanical pencil leads and then use them as the needles for a needle bearing setup. I have never checked, but they appear to be nice and smooth and very straight. That way all you would have to do would be to ream and polish the inside of the tube to the proper diameter. It wouldn't last forever, but you would probably eliminate most of your friction, and it should last long enough to win the race. Another option would be to get some solid graphite scrap from an EDM shop. Turn round slugs with an accurately centered hole and use some nice ground and polished drill rod for the axels. -- __ Roger Shoaf Important factors in selecting a mate: 1] Depth of gene pool 2] Position on the food chain. |
Lead part - cast or turn?
On 7 Nov 2005 16:52:02 GMT, Dave Hinz wrote:
Yeah... but you'll still need to machine it in place to balance. And don't let the cub scout handle the stuff unsupervised - same goes for the lead really. Well, let's be realistic. Handling lead isn't going to make 'em start twitching. If it did..Id be complety screwed. Twitch...spasm...jerk...grimace....#$%!!! Never mind...... Gunner "Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules. Think of it as having your older brother knock the **** out of you for torturing the cat." Gunner |
Lead part - cast or turn?
Bee Firearms has moly.
Karl "Wayne Cook" wrote in message ... On 7 Nov 2005 07:56:27 -0800, "tillius" wrote: Why would you want to weight the wheels of a Pinewood Derby car? Adding weight at their periphery will increase the rotational inertial of the wheels, and they will accelerate more SLOWLY than unweighted wheels. Just the opposite of what you want. But I may be missing something... Because the track we run on has a very long runout at the bottom of the slope. I was thinking that the rotational inertia would cause the wheel's RMP's to decay slower on the straight away. That, and moving the weight from the body to the wheels would decrease the friction between the wheel axels and the wheels. I think it's a bad idea to weight the wheels but go ahead and try it. Experimenting with these things is good for the kids. I'm still disappointed that the local club did away with the unlimited adult class. It was a lot of fun and allowed the kids to learn. Of course part of the reason they outlawed it was because of me. I always had some outrageous design which looked sure to win. The funny thing is that only one of my cars ever won the race and it was a powered car thrown together in about 30 minutes just before the race. I never had a lot of time to work on many of them since I was also in charge of setting up the track and much of the other work that went into the race. The powered car was simply sawed out quickly on a chop saw to get rid of excess wood. Gutted a old VCR for the motor and friction tire to run on one of the car wheels. Clipped three 9volt batteries together. Wire a on and off switch and a micro switch on the front for the starting gate to keep the motor off till the gate dropped. Some sheet metal and screws to mount the motor and a bunch of hot melt glue to hold everything else. That car won the race. Funny though they never did have a unlimited class race after that. :-) But it sure was fun to race the 5 lb ball bearing wheeled car even if it never did win. I took a piece of 1 1/4" pipe. Forged one end to look kind of like a DC-3 nose. Put steel axles through the middle. Filled full of lead (and I mean full with the car being the max length allowed). Made wheels for masonite pressed over ball bearings. That car made everybody stand up and notice. But it never won a single race even after I melted all the lead out to reduce it's weight. It did great on the straight away but took way to long getting up to speed on the slope so it always lost. The first year I lost to a guy who took his old cub scout propeller driven rocket and made a base for it. He used standard derby wheels and filled the base full of lead. But the prop gave him enough of a boost to beat me. After they outlawed the unlimited class I concentrated on design. Helping my daughter come up with designs that brought home at least one trophy a year (some years we brought home 2 or 3 what with the adult class and more than one car entered into it). In fact some cars just kept bringing home trophies for years since we'd enter the old cars into the adult class (we had to pay to do it so it was for a good cause). The last few years the local Awana's club has gone to the boat races instead of the cars. In this case we kept bringing home race trophies since I taught my daughter how to blow them properly plus I always streamlined the boats. In fact my standard design for the boats is a tri-maran with much lower water friction that most boats. But we never got a design trophy for any of them. Looks like I won't have to worry about that this year though. Since my daughter got older and decided to not do Awana's this year. I may end up being roped into the race again though since the water trough tracks are stored at my place (I built them from my own money). Actually the finish gate for the car track was built by me as well though somehow it ended up being stored somewhere else the last year or two of the race. I may be wrong, but since we've got another year to prepare, I was thinking we could set up a small test track in the basement and try different configurations. It would make a great science project for the kids as well. Sounds great to me. BTW, while I'm on the subject, is there a better lube than graphite powder? We tried teflon and graphite this year and the graphite definitely outperformed the teflon by a HUGE margin. Moly is what you want in powdered form. Harder to find than graphite but much slicker. Wayne Cook Shamrock, TX http://members.dslextreme.com/users/waynecook/index.htm |
Lead part - cast or turn?
Another option would be to get some solid graphite scrap from an EDM shop.
Turn round slugs with an accurately centered hole and use some nice ground and polished drill rod for the axels. Alas, you have to use the nail axels that come with the kits. You can polish them and lube them, but that's the extent of the modifications allowed to the wheel hubs and the axels. Tillman |
Lead part - cast or turn?
In article .com, tillius
says... Alas, you have to use the nail axels that come with the kits. You can polish them and lube them, but that's the extent of the modifications allowed to the wheel hubs and the axels. There is one legal trick with the wheels that puts you in a different class though. You probably already know it. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Lead part - cast or turn?
"jim rozen" wrote in message
... In article .com, tillius says... Alas, you have to use the nail axels that come with the kits. You can polish them and lube them, but that's the extent of the modifications allowed to the wheel hubs and the axels. There is one legal trick with the wheels that puts you in a different class though. You probably already know it. Jim Tell us. Do you mean turning them to +/- 0.0002" concentricity and roundness, like I do? g BTW, I use Simichrome to polish the axles, after the 2000-grit w/d, which I taught my son to do. He won all three years. -- Ed Huntress |
Lead part - cast or turn?
Do, don't know it. The only ones I know you can do is the lube and
polish. I heard you could take an appropriately sized machine screw, heat it up and screw it into the hubs and it would cut/melt threads in the hubs that you could load with graphite, but I don't think that one is legal. I've seen about beveling the tread so a smaller portion touches the track or only running with 3 wheels touching, but that's about all I've seen. Let me know what it is? Tillman |
Lead part - cast or turn?
In article .com, tillius
says... Let me know what it is? The three wheel one. You rig the car so that one wheel is off the track. This makes a huge difference in the time, and it's legal as far as I know. JIm -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Lead part - cast or turn?
In article , Ed Huntress says...
Tell us. Do you mean turning them to +/- 0.0002" concentricity and roundness, like I do? g BTW, I use Simichrome to polish the axles, after the 2000-grit w/d, which I taught my son to do. He won all three years. Hi Ed. How're the college visits going? I was getting at the 'one wheel off the track' trick which apparently makes a big difference. I think it's legal. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Lead part - cast or turn?
The three wheel one. You rig the car so that
one wheel is off the track. This makes a huge difference in the time, and it's legal as far as I know. Yep, it's legal. And it's funny too. A lot of parents will accidentally get the wheels aligned that way then come to the workshop and ask us to help them fix the car so all the wheels are touching. So we do :). Tillman |
Lead part - cast or turn?
"jim rozen" wrote in message
... In article , Ed Huntress says... Tell us. Do you mean turning them to +/- 0.0002" concentricity and roundness, like I do? g BTW, I use Simichrome to polish the axles, after the 2000-grit w/d, which I taught my son to do. He won all three years. Hi Ed. How're the college visits going? Good. Two more to go. How about you? I was getting at the 'one wheel off the track' trick which apparently makes a big difference. I think it's legal. I tried it, I saw no difference, but it was on only one car, on my 16' test track. The biggest issue was tracking straight without a guide track, such as on a hardwood floor. That made big-time differences on the actual track. Of course, the long-wheelbase deal is the real biggie, but I don't like seeing them without a special class. They're sure to win if they're done well. Think low polar moment of inertia. g Keep the weight concentrated and dead-center. -- Ed Huntress |
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