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I have been scratch-building 1/32nd cars to compete in the IHSR series, creating custom chassis components, many of which are parts made on a filament 3D printer.
One car I have created is based on a Monogram model of the Cooper Monaco racer. I have used the body as the main structure of the car -- a monocoque design. There are three sub-chassis attached to the body, a motor pod, a center module that carries a rattle pan, and the front sub-chassis that includes the guide and the front wheels.
That front sub-chassis mounts the front wheels on a pair of stub-axles. Each wheel has its own ball-bearing fitted into its hub. Those ball bearings are a loose fit on their stub-axles, so the front wheels are a bit wobbly -- they don't have to spin exactly square with the chassis. They have some ability to self-steer. At least in theory they can steer and roll rather than slide when the car drifts a bit in a corner. And that, in theory, should reduce the front-end drag in cornering, making the car less likely to spin out.
That front end wobble was not intentionally part of the design. It just seems to have happened. But that car has started to perform really well, and I am beginning to think the wobbly wheels are -- to coin a phrase -- not a bug but a feature.
They are not the first set of wobbly wheels in slot racing -- not by half. The 1970's HO TycoPro chassis designed by the legendary Pat Dennis featured skinny front wheels loosely mounted on plastic stub axles. Those wheels most definitely wobbled. Was that by intent? Nobody ever seemed to mind, and the TycoPro chassis was a definite success, even if its pickup system was not so stellar.
One of the top competitors in the IHSR club has pointed out to me that when a slotcar enters a curve there is a conflict between the guide and the front wheels. The guide is trying to turn the car while the front wheels want to keep going straight. That appears to be the reason why there is so much emphasis on keeping the load on the front wheels light and the front tires slippery -- so they put up the least amount of resistance to the guide's efforts to steer the car.
I'm thinking my wobbly wheels are helping in that direction. Rather than get dragged sideways they'd self-steer into the corner. One can hope they have a bit of gyroscopic action so their ability to wobble doesn't have them flopping chaotically either in the corners or in the straights.
Add to the list of the mundane superpowers I crave would be the ability to actually see what those front wheels are doing at speed. In my prior life as an engineer I once had access to high speed cameras capable of thousands of frames per second. It would be just the thing.
A little bit of online research has turned up the fact that the current iPhone models can take 240 frames per second in Slo-Mo mode. But I don't think that would be fast enough. There are high speed video cameras that cost less than a thousand dollars, but Santa would have to be very, very happy with me for such a thing to come into my life.
Anyway, at the moment it appears that my car's wobbly wheels are part of a package that is performing really well. If they aren't helping it does not appear they are hurting.
Ed Bianchi
One car I have created is based on a Monogram model of the Cooper Monaco racer. I have used the body as the main structure of the car -- a monocoque design. There are three sub-chassis attached to the body, a motor pod, a center module that carries a rattle pan, and the front sub-chassis that includes the guide and the front wheels.
That front sub-chassis mounts the front wheels on a pair of stub-axles. Each wheel has its own ball-bearing fitted into its hub. Those ball bearings are a loose fit on their stub-axles, so the front wheels are a bit wobbly -- they don't have to spin exactly square with the chassis. They have some ability to self-steer. At least in theory they can steer and roll rather than slide when the car drifts a bit in a corner. And that, in theory, should reduce the front-end drag in cornering, making the car less likely to spin out.
That front end wobble was not intentionally part of the design. It just seems to have happened. But that car has started to perform really well, and I am beginning to think the wobbly wheels are -- to coin a phrase -- not a bug but a feature.
They are not the first set of wobbly wheels in slot racing -- not by half. The 1970's HO TycoPro chassis designed by the legendary Pat Dennis featured skinny front wheels loosely mounted on plastic stub axles. Those wheels most definitely wobbled. Was that by intent? Nobody ever seemed to mind, and the TycoPro chassis was a definite success, even if its pickup system was not so stellar.
One of the top competitors in the IHSR club has pointed out to me that when a slotcar enters a curve there is a conflict between the guide and the front wheels. The guide is trying to turn the car while the front wheels want to keep going straight. That appears to be the reason why there is so much emphasis on keeping the load on the front wheels light and the front tires slippery -- so they put up the least amount of resistance to the guide's efforts to steer the car.
I'm thinking my wobbly wheels are helping in that direction. Rather than get dragged sideways they'd self-steer into the corner. One can hope they have a bit of gyroscopic action so their ability to wobble doesn't have them flopping chaotically either in the corners or in the straights.
Add to the list of the mundane superpowers I crave would be the ability to actually see what those front wheels are doing at speed. In my prior life as an engineer I once had access to high speed cameras capable of thousands of frames per second. It would be just the thing.
A little bit of online research has turned up the fact that the current iPhone models can take 240 frames per second in Slo-Mo mode. But I don't think that would be fast enough. There are high speed video cameras that cost less than a thousand dollars, but Santa would have to be very, very happy with me for such a thing to come into my life.
Anyway, at the moment it appears that my car's wobbly wheels are part of a package that is performing really well. If they aren't helping it does not appear they are hurting.
Ed Bianchi
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