[vfr750]

It is generally accepted that it is advantageous to have the guide as far in front of the car as possible. With the different types of guides available, jet flag, trailing guides, guide pins etc. is it the pivot point or the leading edge of the guide that matters.

Cheers,

John

 

[GRAH1]

The distance between the rear axle and the pivot point is the important measurement the longer this distance the less twitchy the car will be ,the feel of the car will be more relaxed and probably a lot easier to drive than a car with its guide pivot set up closer to the rear axle .My own preference for the guide is a leading one as it acentuates the above settings ,but a trailing guide can also perform well and does have the advantage of being able to set the pivot point further forward on a short nosed car without havin the guide show .
Hope this helps
Graham

 

[Russell Sheldon]

The "guide-lead", i.e. the distance measured from the centre-line of the rear axle to the centre of the guide pivot post is a critical dimension. Just moving the pivot point one or two millimetres forward or backwards has a profound affect on handling.

Here is an extract of an interesting article that was published in Model Cars magazine, October 1969, which probably best explains why tripods handle better!:

How far in front of the front axle should the pivot of the guide-flag be?

A simple experiment is worth doing to get the 'feel' of this. Fig. 2 shows a split-axle complete with wheels soldered to a strip of Meccano. Using a nail as a pivot, as shown, if the nail is in position (1) close up to the axle, you will be able to steer the axle round the nail quite easily, but note in doing so that one wheel rotates in the opposite direction to the other; hence the use of a split-axle in the experiment. If the nail is moved to the dotted position (2) well away from the front axle, you will have difficulty trying to steer the axle around the nail; you will have to force the tyres to skid in a sideways direction. To give them a chance, round their edges with sandpaper if they are not already rounded.

If the nail is in some intermediate position, you will feel a medium resistance to steer-ability and you are getting close to a useful position for the pivot point.
The moral of all this is that (i) if the pivot is too close to the front axle, the car will tail-slide a lot wagging side to side up the straight and broad siding round the bends; (ii) if the pivot is too far in front of the front axle, the car will tend to tip over round the bends.

In getting the 'feel' of the resistance exerted by the front wheels against drift when cornering, remember that a 6 oz. car in a fast corner is subject to a centrifugal force of about half a pound. So push around quite a bit while doing this simple experiment and try to judge the anti-slide, anti-overturn control exerted by the front tyres.

In general, the more weight distribution you have towards the back of the car, the further the guidepost will need to be in front of the rear-axle; in 1/24th scale, you may have as much as 1" for the fast commercial tracks. But do remember to round off the edges of the rear tyres, to prevent 'tripping over' and erratic behaviour on corners.

Kind regards,

Russell