Depleted Uranium Hubcaps

Gold, uranium and tungsten all have an s.g. of 19.3 Lead (and silver) are 11.3.

It would be simpler to use tungsten, but I believe it is hard to machine.

Gold is easy to machine but weak and expensive.

Uranium is probably cheaper than all of them but difficult to get.

I'm not familiar with slot cars. Do they have a suspension? If so, the ratio of sprung to unsprung weight needs to be kept as low as possible otherwise handling suffers.

On another tack, cornering involves getting the mass around the corner with only the friction of the tyres to stop it spinning off. If you increase the mass, keeping it on the track becomes that much harder, even if the mass increases the friction force available at the tyre/road interface, the side force to be handled increases even faster.

The extra traction may improve acceleration if there is enough power to cause wheel spin without the extra weight.

I think your right, and thanks for taking the time for such an informative and well thought out answer. I knew there was a bunch of DU somewhere, $50 a pound, but I didn't realize it was so hard to get. I got the idea watching F1 races, and as I said in an earlier post my brother knows Stewart Koford personally, one of leading manufacturers of slot car products in the world. So, any idea we could come up with might end up making a little money. Oh well, back to the drawing board. I wonder if F1 is going to keep using those hubcap things on their cars if the lap times go up after they fall off.

Formula One Hubcaps

Actually, a car show on TV said the coming model from Rolls Royce will have stationary wheel fairings. Not to help with brake cooling or aerodynamics of course, but to show off the flashy Rolls Royce emblems.

With regard to F1 hubcaps, they are very light and only designed to improve the shape, reduce drag and help on brake cooling.....

Extra weight is only under very strange circumstances (bad original design) useful.......

Having to add weight to balance/improve things is the mark of a failure.....

suppose, :

you were able to acquire a supply.

big o tires has a catalogue of rims.. with the modeling skills that you have exhibited..

imho : to match a style to either pattern or use as a base,

might the idea to be: to machine the complete rim as a one piece unit....

my 2 cents

..

Good idea. It would be easier to balance too, I think. I just have this idea in my head that putting weight at the widest possible points of a car, the outside of the rim, would help handling. When you go around a corner, all the weight is transferred to the outside of the corner, and the tires on the inside of the curve are unloaded and try to lift up. Putting a weight on the outside of the rim of the inside tire would hold that tire down, hold the car a little flatter, and get better traction. My 2 cents...

I think it is a flawed concept.
I don't think it makes any difference if the weight is in the wheel rims or not, the aditional centrifugal force due to wheel rotation is merely trying to expand the rim.
The extra weight at the back will just tend to throw the back out.
this is all just my gut feel, surely it's simple enough to make a simple test chassis and add weight.

I don't think adding weight ever mady anything go faster. Maybe it can give better grip and excelleration... but what you gain on the swings you lose on the roundabout.

I'm happy to be shown to be wrong on this, but I'd say re-distribute weight rather than adding it.

Del

not having looked into the shaft horsepower from the slot motor ...gonna be tiny wheels.., i think...

I have a question: Did they both lose the same hubcap?

Why do you want the rims of the car to be heavier? You gain nothing from the fact that the wheels are rotating. Don't forget that any down force due to centrifugal force is balanced exactly by the centrifugal force on the other side of the rotating wheel going upwards. The objective in a real race car is to reduce the unsprung weight at the wheels. Why not just add weight to the body over the wheels, you'd accomplish your objective of getting more traction. Nothing to be gained from centrifugal force.

Hi,

I might not be in slot car racing, for better handling its better to look at working out some suspension system with anti-roll bars. Get examples from the old toyota corollas or mazda 323, they called them twin trapezoid link. It works like double wishbone suspension.

Good luck

KN

Hello Route 89:

Being as others put their two cents worth in, I'll only put my penny and a half worth in. It's already been mentioned but let me reassure you, unless you've got power to spare rotating mass is no place to put weight, you're just ending up with a big flywheel, you have to stop and start.

I'll go with putting on the car, or nonrotating axle assembly. Depleted uranium is still mildly radioactive, don't go grinding and breathing the stuff.

Route 89 --

You generally want to keep unsprung weight low to insure good traction due to ability of the wheels to stay in contact with the track surface whenever there is any suspension movement. This is a very old rule of thumb in most types of vehicle competition. You do add weight to farm tractor wheels because that is the most convenient place to put it and they go slow and have no significant rear suspension. But that's about it.

You guys into model car racing would do well to learn about the issues of handling for road race cars as well as circle track cars as a starting point and then understand the hows and whys of differences between your scale model cars and the full size cars. Also keep in mind that running surface conditions may vary from track to track so the weight setup that's right for one track may not be optimum for another.

Back to the issue of where to put added weight....Put the weight as low as you can in the body or frame if you are convinced traction from more weight is more important than the loss in acceleration from the added weight.

Note that tungsten (specific gravity 19.3) weighs just a bit more than uranium (specific gravity 19.05). Tungsten is found in TIG welding electrodes and gets consumed down to an unusable stub where it is held in the welding torch handle. These electrodes are small diameter rods commonly 1/16 to 3/16 in diameter and about 7 inches long when new. The material is too hard to cut with a saw blade; but being fairly brittle you can grind a notch put it in a vise and break it to the length you want. In years past tungsten electrodes used for welding steel contained 2% to 4% thorium, which is slightly radioactive. If you use this type you'll probably want to avoid breathing the dust or eating without washing your hands first.

You can find TIG welding electrodes on ebay for a good price, especially the obsolete thoriated type. I use tungsten electrodes for weighting small HO scale locomotives to get better traction and electrical contact with the track. I notch and break them to the lengths I need and epoxy them together into a close fitting stack.

Ed Weldon

Well said john M I really could not believe that sane people would want to start messing about with this stuff!

There was plenty reported (and not revealed) about the effects of DU in the atermath of the 1st Gulf war and only time will be the true answer to the physiological outcomes of being exposed to it.

It is most certainly not for playing with in slot cars!!

I believe that its the "dust" of either exploding the stuff or working it with a lathe or grinding that is dangerous when breathed in.....

But it is not alone in this, several other metals exhibit similar problems when worked - Beryllium for example...

Hi,

you are right, this ultra-dangerous.

Any particle (metallic or oxidic or any other alpha-radiating elements or molecules) will adhere to nasal or bronchial or lung-tissue.

There is the first likelihood of cancer by radiation.

Then there is dissolution into body fluids - maybe doing damage there too. (Slow dissolution of oxide but rapid dissolution of metallic U because rapid reaction to hydroxide.)

Then filtered by the kidneys - high concentration ratio - high radiation damage.

Some authors tell us that this is mainly chemical toxicity but I never heard a conclusive argument deciding the question of chemical versus radiation toxicity.

The small amount of tungsten in the welding rods for TIG-welding is forbidden now because of radiation and inhalation of fumes. Although this is very small and slow evaporation.

Beryllium is not nearly as critical: existing in typical agricultural soils at 0.5 to 5 mg/Kg.

Some people are allergic at Be exposure - also at these low levels.

At higher levels Be is doing havoc with our internal protein chemistry as the necessary enzymes - all containing one metal atom as working center. Be is replacing these metal atoms and making the enzymes inactive. So there is a difficult to diagnose and diffuse illness.

So do not grind dry: CuBe or any other Be containing alloys, not: emeralds, aquamarines and other Be containing precious stones. Allowable concentration in air around machines is 2µg/m3 around most machines and 5µg/m3 around grinding- and edm-machines. If I were responsible for these I would lower this allowable concentration by a factor of 100 or better eliminate any exposure by sufficient direct ventilation. In waste-water 10,000 times more is allowable or 20mg/kg and here I do not see any pathway that may do damage.

RHABE

RHABE -- Relative to your paragraph quoted here: "The small amount of tungsten in the welding rods for TIG-welding is forbidden now because of radiation and inhalation of fumes. Although this is very small and slow evaporation."

I'm thinking you meant to say "thorium" instead of tungsten. The majority of the metal in TIG welding electrodes is tungsten. In the case of the electrodes used for TIG welding aluminum they are straight tungsten with no thorium.

It's important to note the worker exposure conditions that were considered when thoriated tungsten welding rods were phased out. We're talking all day welding 250 days a year at likely 30-40% duty cycle for a production welder. And note that during the welding process the electrode is vaporized into the air surrounding the welder. This is way different than the exposure that might occur during casual light grinding of the material by a hobbyist who is breaking them up for weights.

There are basically 4 sources of these electrodes: A welding supply store, a welding shop electrode disposal cache, ebay and your casual seller who has no idea what they are. The first two should be able to tell you what they are. Many ebay sellers will also know and list and price the item accordingly. The casual seller probably won't know unless they are in the original package which likely will be marked due to the varying applications for the electrodes. (Pure tungsten for aluminum welding is just one example). It's reasonable to assume anything unmarked from an unknown source contains thorium. But like I said the hobby application represents much smaller exposure than production welding. I don't worry about it. I just vacuum up the dust and wash my hands after notching the electrodes for my model train projects.

Ed Weldon

Hi Ed Weldon,

you are right, I mixed up (late at night) the two materials.

Your procedure is ok., but I would prefer making the notch underwater by a handheld small tool, so almost no dust.

More dangerous is dry grinding of granite and other U containing material.

Thank you for correction

RHABE

"In waste-water 10,000 times more is allowable"... I know of a car wash that uses recycled waste water. Smells like it too.

Ha ha at last someone with a real problem I will give the standard lawyers disclaimer (since i am one!) "I make this statement without prejudice as I am no expert!" That being said it seems to me that you are looking at the wrong factors - I guess you wanna go faster and stay on the track? Aside from the dangers graphically outline by Mr Meuller the discussion re DU is in my mind irrelevant.

What makes the car go faster is its power to weight ratio and the ability to transmit that power to the track. The last part is the most important - the interface between track and power which is the rubber! adding weight to increase the downforce and achieve better coefficient of friction is not the best method - just slows the car down and higher centrifugal forces during cornering due to added mass balances out the coefficient of friction - so back to square one. Keep it light and focus on the rubber!

I used to soak the rubber in acetone to soften it up he he! well paint a little on the tire surface anyway! well that's my addition to this neat thread.

Best to All Rogerzz

HI rogerzz,

Hmmm, you know something about physics and you don't sound like a lawyer, so we'll let you live (just don't accept my ex-wife as a client!)

Mike

Once again, thanks to everyone for the informative input. This really is a great bunch of people. The depleted uranium idea has been deposited into the toxic waste dump, like most of my ideas. I had been assured that the residual radioactivity of DU was negligible, but I knew nothing about its toxicity. John M, you have probably saved me from a painful, hideous death. And thanks to Ed for the tungsten idea, I'm going to go down to my friend's welding shop today and steal some. And, I'm going to show everybody I'm not crazy :-) The prevailing obsession with weight reduction is exactly the reason why I came up with the idea - nobody else would even consider adding weight to a race car to make it faster. Power/weight ratio is the golden rule, but I have violated it in the past, and it worked. I had an old Strombecker motor, which is hideously heavy and underpowered compared to my brother's 6-magnet 250,000 rpm lightweight $300 motor, but I soldered up a chassis with the Strombecker motor offset as far to the outside of the chassis as possible, right ahead of the right wheel. Then I counterbalanced the left side of the chassis with lead, and I beat him. He would fly by me in the straight, but in the corners I murdered him. The reason slot cars come out of their track is because the wheel that is on the inside going around a corner lifts up at a certain speed, and the car crashes. It's not so much tire traction as it is using gravity to hold the car flat around corners. I think everybody's right about too much rotating mass on the tire rim, but I'm going to put a piece of tungsten right behind the rear wheel, not rotating, as far to the outside of the car as I can. This should keep the wheel from lifting up around corners. If it works, the same principle might be able to be applied to F1 cars. Watch the slow-mo videos of them when they corner - the inside front tire lifts up. Putting weight on those ugly stationary hubcaps would hold the inside tire down. My 2 cents...

Using gravity

Hmmmmmmm - sounds like a few variables need to be eliminated. If it is an oval track and the cars circuit in one direction then the position of the motor is important not so much its weight - no need to counterbalance anything with tungsten lead gold or best wishes! You were right with repositioning the motor and I am sure there are some engineers more clever than me that could work out the angular moment generated, at a given centrifugal force, of placing the motor as far as possible from the outside wheels. It would have the same effect as lowering the center of mass. If you took it to extreme perhaps you could mount the motor on the outside of the chassis or in between the wheels or maybe just have one chassis rail for example (all on the inside side the car is turning to I mean).

Cheers Mikerho - no I don't do matrimonials - kinda messy dealing with real people

I'm not sure how to acomplish it but a low mounted weight that would shift towards the inside, is what you really want. It would probably have to be electrically operated [unless someone can come up with a mechanical way]

Now when it comes to the tig electrodes, the sharpening releases a bunch of dust... A very common practice, especially for SS sheetmetal.

Not likely to succeed

http://wapedia.mobi/en/Sway_bar

Since slot cars have almost unlimited energy avalable (drawing from the track and not an onboard source) how about putting skirts around the car and adding a second motor to suck air out from underneath and blow it out the back? That would increase downforce and traction without increasing weight too much. If you could get just .25 psi over a 2 square inch area, that would be the same as adding a half a pound of DU to the car's structure without the acceleration and cornering problems.

My thoughts are that adition to the rotating portion of the wheels will be a disaster in handling.

Why does a pushbike go straight and not fall over? It's the energy maintained in the rotating tyre and wheels that do this.

The extra weight in the wheels will become like two miniature gyroscopes, trying to continue straight along the track and NOT turn the corner. I suspect that the outcome of trying to turn will lift the car front and you will see some very spectacular flips different from the traditional tail spinout from loss of traction.

Maybe the guys familiar with circuit racing could comment on this.

If added wheel mass was a great idea, then cars would not have moved to the lightweight alloys and all the DU in the world would be in high demand.

Hello Just an Engineer:

I'm not a circuit track racer, but I've got plenty of experience in drag racing, any rotating mass is bad for acceleration, whether it's a crankshaft, or wheels what ever, one of the secrets to a good drag racing engine is lighter rotating mass, and obviously as you mentioned they don't spend the money on magnesium rims for nothing.

Without even considering the handling characteristics, adding rotating mass is a bad idea.

Please take a moment to peruse this article generated by WHO about DU before continuing further in this endeavor.

http://www.who.int/mediacentre/factsheets/fs257/en/ - sorry, link no longer available

DU is used in radiation implants and the advisement is not to allow pets in close proximity to the radiated areas on the patients body. This is seemingly contradictory of some statements of potential DU toxicity.

Bwire,

About 18 months ago I spent a week looking for reliable information on DU. There is a very wide range of views on its hazards/safety, its health harms/innocence, etc. The WHO paper you cite is an example of one that is strongly on the innocence & safety side of the reports. I have difficulty with reconciling this with the handling hazards outlined in the two MSDS's I have read regarding DU.

Those who have been most outspoken about DU have ignited a large amount of controversy and been condemned. Perhaps we need to adopt the stance taken by PSR (Physicians for Social Responsibility), who advocate a precautionary principle: Because of the large number of reported problems and the wide range of disagreement regarding DU we should not use it until we have proven that its use is safe. I don't think we can.

--JMM

Once again, thanks for all the input, especially the info about depleted uranium. I now have a tungsten welding rod, and I am going to carefully break off 2 small pieces of it and position them as low as possible and as far outward on the chassis as possible, non-rotating. Slot cars have no suspension, and basically start out as a 3" x 5" plate of .065" thick T6 aluminum or .050" tempered spring steel that has about .035" clearance from the track surface. Most tracks are road courses with plenty of curves. The idea of adding some weight to the rim is to prevent the inside wheel from lifting up around corners, which is what causes it to come out of its track. However, I agree that the added moving mass would kill this idea. So, I am now adding 2 pieces of tungsten as low as possible (.035") just behind the rear wheels to see if this will keep the wheels from lifting up around corners. We have to drive about 60 miles to Chicago to get to the nearest track, but I'll try to post some results when I get a chance. THANKS AGAIN!

Slot cars cornering

Onboard camera - if you listen carefully, you can hear the wheel chatter around the corners.

Suggest diy an inertia driven potentiometer controlled lateral sliding weight to compensate. Use DU as the weight

bwire -

Interesting suggestion. When slot cars go around a corner, the guide that fits into the slot on the track swivels left and right as you go around the corner. Maybe I could connect a rod to the guide with a weight on the end of it to shift the weight left and right as it corners. And, I could finally get to use my depleted uranium... (just kidding).

Military Film about Depleted Uranium Awareness Training

Hazards of Depleted Uranium

Another reminder to read the fine print on your ID Card eh

What happens when you add weight right over the guide, or maybe some nice graphite brushes to reduce friction...

In addition to difficulties acquiring it and the difficulties and bad things associated with metalworking depleted uranium, it is not something that will improve the time on the slot cars. You want as much of the available energy to be directed into the forward motion of your car. The energy ends up divided into linear kinetic energy of the car and wheels and the rotational kinetic energy of the wheels. The larger the mass of the wheels, the greater the amount of energy must be dumped into rotating the wheels. Also, the further the mass is from the center of the wheel (or the hub), the greater the moment of inertia of the wheel and therefore, more of the energy is lost to making the wheel rotate. In other words, the outer edge of the rim of the tire is the worst possible place to put it.

You want to reduce the mass of the wheels as much as possible, especially around the outside edge, reduce the friction on the axles, make the car more aerodynamic with a better shell and reduce the mass of the car if possible. There eventually comes a tradeoff between lightness of the car and slowing down to take the corners, but an experienced person such as your brother will likely have a good feel for that.

PhysicsProf -

Thanks for the input, very informative. Putting the weight on the wheels, and especially using depleted uranium, has been abandoned. I'm going to use tungsten. I still think there is another way to look at it. Reducing weight is certainly logical, but if you could magically reduce the weight of a slot car, or a real car, to zero, it wouldn't move. You would then add weight to the car, and it would go faster. I would add this weight as low as possible and as close to the wheels as possible (not on the wheels), and as wide as possible to keep the car as flat as possible around corners. It would be interesting to run a computer simulation of how an F1 car would act if it weighed 10 pounds, or 100 pounds, etc., and find out how much the car would have to weigh to keep it from sliding all over the track. Would a computer simulated 50kg car be faster than a 605kg car around the corners? It would also be interesting to see where the optimum location of the added weight would be. The weight and weight distribution of this 'magic' computer simulated car would be unobtainable in the real world, especially with all the rules, but it would give F1 engineers a direction and a theoretical goal to aim for.