[Mecoprop]

A very neat piece of work, LSI!
Probably deserves a little written piece on the replacement stubs, though I'd take a small bet that it's very much on Larry LS's lines?

Although relatively small figures are showing in the poll, it reads something like I would have expected, with a small majority plumping for independent fronts, but not really much in it. Some of you may be surprised as to how many have stated a preference for non-independent? I am not really surprised.

I suspect the reason for that might be at least partially due to personal experience of independents being limited to the Fly arrangement, which is generally considered to be very poorly implemented.

Of the larger manufacturers, Fly actually deserve congratulation for making the relatively bold move to produce independent fronts as standard. Yet, having done so, it appears that their poorly engineered 'solution' is one of the regular major targets for criticism of Fly product - sorry, but that one is well deserved imho. It's usually preferable to avoid altogether a design that is difficult to make work properly than to produce a really sloppy setup that creates significant problems of its own - and then continue to produce it, for years, in the face of mounting and justified criticism.

 

[Wankel Ickx]

QUOTE It's usually preferable to avoid altogether a design that is difficult to make work properly than to produce a really sloppy setup that creates significant problems of its own - and then continue to produce it, for years, in the face of mounting and justified criticism.

Sorry Meco, we're talking slot cars and axles here, not Microsoft Windows.

Cheese.

 

[Larry LS]

Hey Mike that front end looks suspiously like you used some TSRF parts to make them with. Hmmm PDl will be talking at you soon !

 

[JoeAngelicchio]

QUOTE (LSIntegra94 @ 20 May 2004, 03:50)Ah, but what do you do when you can not fit a solid axel? How about this as a solution? Gets rid of those pesky plastic stub axels too.

Hey Integra,
Do you have pics showing the stubs axles in more detail (extreme close-up)? Are those e-clips on the ends of the axles and are those pillow blocks?

 

[LSIntegra94]

Larry caught me. PDL would be proud though.

I used this design on last years Marconi car too. I just finished a write up on this as has been requested. So, if you want see a little more then click here.

 

[Tropi]

That is a nice bit of work, LSI, and a very useful how-to.
Thank you very much for that.

 

[wixwacing]

I've got a feeling I've mentioned this somewhere before but I'll do it again for the benefit of those that missed it.

The following pictures are of a simple trick to convert solid axles into independantly rotating stubs fixed on the same axis.

This is a picture of a front axle sawn through the centre. After the ends are cleaned up, two plastic or brass collars are superglued on the shafts at the point where they would be just inside the front axle holders.

A length of 3/32 I.D. brass tubing is then cut to fit snugly inside these collars when in place and the assembly is lubed with a bit of STP treatment and clipped back into place.

Needless to say, everything needs to be spotlessly clean before gluing or you could find your axle half out of the car at a crucial moment!!

Simple test to decide if your model would benefit from this conversion is to drive at a low speed round standard curves. If your car slows in the curve then the front wheels are dragging due to the lack of differential. Another test is to run your model without front tyres. If its performance picks up then this mod may be the cure.

Cars that don't have front axle bushes need a small 3/32 I.D. washer placed at each end of the axle between the collar and the wheel to run inside the axle clips on the chassis.

It is an essential mod for all 2wd cars with a spring loaded guide, Ninco and SCX

 

[GRAH1]

Nice mod wix

 

[Fergy]

Very nice, Wix!

QUOTE Simple test to decide if your model would benefit from this conversion is to drive at a low speed round standard curves. If your car slows in the curve then the front wheels are dragging due to the lack of differential.

I would go a step further, and say that sharp curves are the only ones where your senses can detect the problem of tire scrub. It is happening on any curve, of any radius, and unless your front tires are not contacting the track surface, it is an improvement to run independent fronts to avoid any scrub at all.

Remember too that front tires, scrubbing in a turn, can increase rear wheelspin and decrease rear traction in corners since the motor is trying to push those front tires through the turn. Any reduction in rolling resistance translates directly to better performance.

 

[Tropi]

Yes, agree with Grah, a very nice modification.
I have seen the Wix-mod before but it wasn't here and I'm delighted to get this one on to our board too.

Now, to throw a few scraps into the ring for scratching at!

Even when running a tripod with front wheels designed to be suspended more or less permanently, under hard cornering, I think we should probably assume that the outer tyre MUST touch the track surfaceat some point?

For simplicity's sake, let's assume the front rubber is touching track at least some of the time. There seems to be a common acceptance that minimising the tyre width is a good thing and using hard tyres or in some way hardening their surface is a good thing. But I am not even totally convinced that this is always, necessarily, true - I may come back to that point . . . if I can remember long enough!

The basic argument for independently rotating front wheels is that, during cornering, the outer one must travel a greater distance than the inner. If they can't rotate at different speeds, then this will create drag and slow the car down. But I'm not sure it's as simple as that. For a start, is it NECESSARILY a bad thing if the car is slowed a little in a curve? In any case, there are similar arguments used in favour of a differential on the driven wheels, but decades of experience by a massive horde of expert drivers has pretty well conclusively proven that a diff adds NO overall advantage and is, if anything, a hindrance! Certainly top end racers wouldn't dream of using one, not ever. That's worth thinking about before concluding that independent fronts MUST naturally be advantageous - it is certainly not a foregone conclusion in spite of seeming so obvious at first thought.

That's enough for this post - it is a complex business and I want to sit back and see what happens before opening it to further doubt (and my particularly abstruse theories!)

 

[GRAH1]

QUOTE front tires, scrubbing in a turn, can increase rear wheelspin and decrease rear traction

Got to agree with Fergy on this one , When testing for this years world proxy I found 3/10ths of sec round pendle on my ferrari just by adding 10 thou clearance under the front wheels. This car already had independant wheels but I was look ing at the diference between my set up for Chris Briggs track and home.

 

[Intergrali]

yes all very well and good having a differencial and all that work, however I find it a load easier to go ask mickl for his make up bag and borrow some of his nail varnish, he only let me use clear last time, maybe he knows it's heavier than pink.
anyway, problem solved!

til Next time -

Inte

 

[GRAH1]

you and mick takin up drag racing again?

 

[Intergrali]

nah, I quite like the curves

 

[BEEJAY7]

Got to agree with Graham on this. A tripod on smooth wooden tracks has always been superior to all four wheels on the track, after all look at BRSCA cars they don't really have any front wheels!. If you have this type of setup I'm not convinced that independent front wheels then have any effect at all.

If your tripod car is corning hard it will lean to one side anyway and only one wheel will be in contact with the track at any one time. Providing there is adequate clearance in the wheelarch the wheel not in contact will just spin in free air.

I can see the advantage of independents on Plexy track where all four wheels are in contact, but they must have plenty of vertical play built in to allow for undulations of the track surface. Especially important if you have Radius One curves.

Regards

Alan

 

[Fergy]

The tripod obviates any need for independent fronts. That's a given. Personally, I hate tripods. I think all 4 tires should touch the track at rest. It's just a personal preference thing...

I'm also not convinced that the tripod is the ultimate, unless those airborn fronts are close enough to the track surface to prevent any roll in a turn from reducing the weight on the inside rear tire to the point where traction becomes minimal. ANY roll force reduces rear traction. Not so important on mag cars, but on non-mag cars it is crucial that both rear tires are kept in contact with the track. The tripod design doesn't do this, particularly on corner entry when the car would like to roll on a line between the guide and outboard rear tire. Tripods are less stable than quadpods.

In full BSCRA or other pro-style formats, there are many additional considerations and factors, but for typical plasticars, I think keeping the front wheels in contact (at least minimally) is a plus, and independent wheels will outperform a solid axle. And the common practice of putting nail polish on the front tires is nothing more than an attempt to reduce the scrubbing that independent fronts will already eliminate. (This might upset Inte and Mick's relationship though!

)

 

[Tropi]

Erggghh!
Fergy, you brought up too many things at once for my noddle!
Let me look at just one.
QUOTE nail polish on the front tires is nothing more than an attempt to reduce the scrubbing that independent fronts will already eliminate
This is the obvious and common perception.
it's so glaringly obvious that it just has to be so.
But nevertheless, I query it gently.
Note, NOT dispute, just query gently!

I would suggest that MAYBE the sideways scrubbing of front tyres so vastly outweighs the relatively small discrepancy in rotational speed that having independent fronts might not matter much, if at all. That would apply when not varnished. Furthermore, that if they ARE varnished, independents matter even less again.

An additional point, just for thought, not rammed down throats - if there is lateral weight transfer at the front, the inner wheel tends to lift and the case for independents is reduced even further.

Finally (for now!), if in spite of points suggested above, if it is still thought that independents are good, then I really can't understand why steering fronts aren't thought to be even better! Yet the vast majority poo-poo steering. Some factors, generally perceived as facts, don't seem to make complete sense when looked at clinically.
Or do they?

 

[Fergy]

Complexity, Tropi, complexity!

We eliminate it at every chance since.... yup, complexity adds weight, and it usually does so at points higher than our idea of ideal center of gravity! Your are right about the sideways motion of the tires also impacting the use of "hard" fronts or "nail polish". That's perhaps less of an issue than the solid axle scenario though - if the fronts touch, it stands to reason that they WILL spend more time rotating than being pushed sideways! Depends on the driver I guess!

But the principle is similar - reduce friction from components that contribute nothing to either forward motion or lateral grip. The front tires do neither. But they MAY contribute to stability in some situations! The negative to independent fronts is weight and complexity, something we eliminate every chance we get - but sometimes, the opportunity arises to use the concept (weight-based classes, etc.)

Steering fronts? Might possibly be the perfect design, IF you could build them without impacting the overall weight and COG even more than independent fronts do! A very tall order indeed! Though I must admit, they do look fantastic when done well!

 

[Tropi]

Let me throw in another little snippet to poke at!

Back end sliding - a nuisance.
Non-independent front wheels help to reduce it, IF both touching track!
Want a demo?
Hold the car down hard on the front end, rear wheels off the track and try to swivel the car around the guide.
It swivels much more easily with independent fronts and much less easily with a fixed pair.
Interesting!

 

[Larry Geddes]

If I may contribute my two cents gentlemen - Everyone has their own views on what does or doesn't work, probably since each individual's personal slot car experiences are totally unique. I think this is why there are so many differing opinions on just about everything inside a slot car.

I can only speak from my own experiences (yours will no doubt be different), so for what it's worth, I feel that a gravity car (no magnets or aero downforce) benefits from having the front tires on the track (the guide bearing practically no weight), & from having independent front wheels. I also feel that some tilting of the rear end is not only inevitable, but actually desirable. Both rear tires cannot stay "hooked up" around curves, & I think that the inboard tire should be able to "get light" & let go of the track surface (unload) as easily as possible, with the traction in the curve coming soley from the outboard tire. A "4-wheeler" needs a lot of chassis flex (twist) to be able to do this; cars with center spine pivots like Russell Sheldon's "flexi-boards" are ideal for this. A "tripod" can be stiffer since it tilts so much easier (assuming the front tires are set up to let it) & unloads the inboard tire by that means. Very stiff chassis that can't either twist or tilt easily either tend to slide a lot, or are prone to other handling problems.

My entry in the 2001 Marconi proxy race (class A - nonmagnet CanAm cars) used a very flexible center spine chassis, fully functional independent fronts, SlotIt V12 in the anglewinder layout, no weight on the guide, & weighed 116 grams overall. The race was held on the (then new) 1/32 6-lane wood track (120' lap) at Buena Park raceway in Los Angeles. The car was not only TQ in the low 7's but also faster than 40% of the magnet car field. It won the race easily, but did not fare so well in concours, finishing 5th overall, with Jim Cunningham's beautiful L&M Lola winning class A.

That is one of my own experiences, but that is not to say that it is the best way, or that the design theory is even "correct". I have had many other experiences with all kinds of cars & on all kinds of tracks, from 3-lane basement tracks running hardbodies to punchbowl king tracks running G27 wing cars, & have had positive results with many different setups. Of course each track has a different "solution" for the car design, but even on a given track there are variations between the cars.

It would certainly be boring (& not much fun) if there were only one "correct" way to do anything, with everything else doomed to failure.