XRAY - Model racing cars

Hi all
Is there any where I can find a more comprehensive explanation of the iss eccentric bushing system on this car. I understand that if the dot is down it give a low pin then the same for middle and upper but it's the toe & castor and all combined that confuses me. I don't think the instruction go into enough detail for someone who gas never used this type of system before.

Hello

On pages 13 and 16 of the manual, you have all the explanations needed for angles and variations depending on the position of the bushings. Is it ok or you need further explainations?

Thanks for your reply but I am having difficulty in understanding the explanation in the instruction manual as I have never used this system before, I get the roll centres and track width it's the front kick up & rear anti squat & toe in settings, my view on what i think I know is with track width the dots either face in for narrower track width & dots out for wide track width / and roll centre is dot down for low roll centre - dot middle for normal roll centre and dot upper for high roll centre. This is of course at the wishbone pivot pin and I understand it has nothing to do with the camber links. PLEASE HELP i just need to understand this so I can tune the car to my liking and even though i have tried online set ups they don't work for me as I think set ups are usually personal to a drivers driving style even though I always start from a base set up as described in the instruction manual , I race mainly on prima felt carpet or astro turf but mainly carpet and at the moment it cold so grip is low ish and I run schumacher yellow mini pins rear & schumacher low profile cut staggers front

Regards

Ian

Hi Ian,

The key to remember is that the 'relative' location of the pin between the front and rear holder will dictate the adjustment for toe, anti-squat and kickup. You can relate it to the neutral pin position (0 insert) and calculate your geometry from there.

The vertical position of the insert controls anti-squat/kickup and roll center at the same time. For example, looking at the chart for the anti-squat adjustment, the 0 inserts in both F & R positions create 2deg of anti-squat. That also means that any combination of the inserts that position the pin at equal height F and R will result in 2 deg of anti-squat. For example the 1st, 5th, and 8th examples in the chart all list 2deg of anti squat because the pins have been move the same vertical distance front and rear, resulting in no anti-squat angle change. Those three locations represent three different roll center locations without altering anti-squat. If a change of the anti squat is desired, then the relative vertical position between the front and rear inserts must change. To increase anti squat, the front vertical location must be positioned 'higher' than the rear. That can be achieved by raising the front or lowering the rear. Which combination you choose would depends on the desired roll center position.

The amount of angle added depends on the relative difference of the front and rear locations. XRAY lists the difference as 1 deg (as shown above those charts) for the insert moving to the outer location. If the front insert is moved to the top row and the rear insert remains in the 0 position, then 1 deg has been added to the angle of the pin. If the front insert is moved to the top row and the rear insert is moved to the bottom row, 2 deg has been added to the angle of the pin because the relative difference in pin height is now doubled.

The same principle is true for the horizontal adjustments of toe and track width. The relative horizontal positions between front and rear inserts dictates the toe angle, while the absolute horizontal position dictates the track width.

Finally, these can be adjusted together using the inserts that move the pin location both vertical and horizontal at the same time. The vertical positions still make the same changes to the geometry even if the horizantal is changed at the same time. The only limitation with the diagonal inserts is that the vertical and horizontal positions must move equal distance because of how the inserts are molded. For example, you can move from the 0 position to 1 deg up and 1 deg out position, but it is not possible to move 1 deg up and only 1/2 deg out by changing only one insert.

That is probably even more confusing than the diagrams! But it will hopefully get you pointed in the right direction to start making changes.

- Bryan

thanks for the reply bryan i will print this off and study it and see if i can work it out from there, i think when i get to understand it it may be that i was wondering what all the fuss was about.

kind regards

ian