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Steering front ends

How DO they do that??
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wixwacing
Marshal!!!
Posts: 1871
Joined: Thu Jul 10, 2008 9:22 am

Steering front ends

Post by wixwacing »

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It is my view that the next significant advance in slot car modelling will have to be the re introduction of Ackermann steering to models. And why do I say this, well, one of the last remaining idiosyncrasies still attached to scale model slotcars (were not talking womps, wing cars and plafits now) is the side slip and consequent drag caused by front tyres that don’t follow the race line!!

When the average model turns into a corner there is a side slip generated as the guide causes the model front to slew sideways relative to the direction that the model is pointing. This sideslip can have a minimal or major effect on a models handling and / or forward progress depending on the severity of the side slip and the co-efficient of friction between the track and the front tyres. This can be felt by placing a model before a medium to tight bend and pushing it slowly round the bend. As the model goes from straight to angular motion, the drag of the sideslip will be felt coming into play



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The solution opted for by various codes is diverse. Some rules allow front wheels to be vestigial!! ie tiny laser cut discs mounted horizontally to the chassis and never seeing the light of day, let alone the track! Some models with correctly mounted wheels still have an air gap between the front tyre and the track. Contact only being made by one side at a time during hard cornering. The application of a lacquer or varnish is an option to some racers. The front wheels get a hard coat of something, usually clear nail varnish, and this reduces the tyre friction to the track. You can sand tyres in a convex manner so that only a very thin strip of tyre at its centre touches the track! Another fix is to fit some ‘hard’ grade tyres to the front of the model. This too will go some way to relieving drag. Some models like Fly for instance, use a ‘wobbly’ front wheel, but the model is running on the guide anyway and the guide drag is more of a problem than wheel drag.

So why concern ourselves with this? Models that take weight on their guides are inherently slowed by the guide. The drag between braid and track is greater than the drag between a rolling wheel and the track, so the model has a handicap for the entire lap length. Place a model which runs on all wheels next to a ‘tripod’ type setup on a piece of spare track and lift the end of the track up slowly. The model on all fours will start to roll noticeably sooner than the tripod model, try this at home kids! This is friction at work and it gets worse the faster you go.



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In the last couple of years, Scalextric have moved towards models which run on ‘all fours’! A lot of their models sit hard on all wheels and the miracle of modern computer engineering has allowed them to construct a guide mount which holds the guide at the right height relative to the models ‘sitting’ position. Grinding front tyres smaller on these models causes the model to loose top speed on the straight but enhances their cornering ability as the front end friction has been alleviated. Fly, too, have adopted the solid front end in recent times, they wouldn’t do this without researching it, I bet! In fact, the vast majority of RTR slotcars are now coming with fixed solid front axles and weight on ‘all fours’ (Scalextric classic and SCX track with raised conductor rails may cause these models to unavoidably adopt the ‘tripod’ stance).

Braid material too has undergone a bit of a metamorphosis. Once upon a time braid was the by product of electrical coaxial cable sheathing. A hard copper with a tinned coating. In recent years slotcar manufacturers have moved to soft copper which has greater drag on dry rails !!??. It’s my view that the best braid available is the good old tried and tested Scalextric tinned braid. Most of the pure soft copper braids dirty quickly from arcing slag inclusions and would need to be changed every meeting to ensure their useful conductivity and consequent performance. Oxygen free brading as used in auto hi-fi speaker wiring is much better too as it is a hard copper compound and will have a reduced friction level. But being hard, it takes a bit of setting up. So running a model ’tripod’ style on its braids is not that good an alternative.


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So where are we going, getting back to steering, it is the only 100% front end solution to front end drag without giving truescale models a sit up and beg look or unacceptably altering the model. Most models will not run in competition, most models will not run on commercial raceways! Most models will be the admiration of the purchaser in the comfort of their own home and on a tight and twisty plastic or board track and the dilemma of drag in corners will not be a dilemma but, for those who want to maximise their models drivability, steering is a serious consideration. The model’s front wheels point in the direction of travel at all times and they have the added advantage of being able to turn independently of each other.

Utopia incarnate! History shows that models already made were leaders in their time. The early Airfix F1’s used to leave my Scaley Coopers and Ferraris for dead when my class mates came round to run on the ‘BIG’ track. Admittedly there were other factors too, but the general smoothness of the Airfix models and the ‘Coffee blender’ coarseness of the scaleys were quite a contrast. Moving up to the seventies and again the MRRC F1s would out manoeuvre anything Scalextric was offering. Later still, SCX Jordans etc were unapproachable in their class as non magnet models and the SRS 2 chassis were so smooth to race. Even Ninco considered it suitable to fit steering to their F1’s with great success. All these models were leaders in their time and ALL had steering, coincidence? I think not.


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So what went wrong a way back? Firstly, the novelty of steering on a model is an extra expense and back in the days when slotcar manufacturer owners were looking to maximise the profit from a niche hobby, cost cutting did not allow such fancy ideas. Others were put off by the frailty of some set ups. I would be the first to admit that the last thing some people want in the heat of a race is for the front wheels to face north and south after a prang. Steering units to date have been prone to this although I can recall very few occasions in my time racing. But to this I say, don’t have a prang!! Drive within yours and the models limits and watch the track ahead. A deslot with a fixed front end model is just as harmful to results! I have to admit to winning an F1 race in days passed with an errant front wheel thrashing away at the front end of the model.

So the next best thing has to be a model with a good steerable front end. Rigid, not rocking, this contributes to the model’s rollover ability. Robust, to minimise a steering failure at deslot. Admittedly, this is more prevalent with exposed wheels on F1 models. The model’s weight needs to be ON the front end and not the guide! And a pair of nice tyres to finish off.



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Pipedream, never gonna happen? Who’s taking bets? Just give it a little time and we’ll see, mark my words. And when It does happen, remember I told you so!
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When I'm not racing slotcars,
I'm out in the back yard, burning food!!

When I win, it's because of my talent, not my car or my controller!
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