Monday, December 27, 2010

Emails on the F104 and F103


How do you adjust droop?  Shock length?  How do you measure?  With a straight axle rear end, the only up travel is at the center of the car where chassis meets rear pod.  I guess I'm having a bit of a problem getting my head around the dynamics of this concept compared to a traditional chassis.  Please explain if you would.

You adjust the droop by shock length.  Take the car at ride height, and looking at it from the side, lift it until the rear tires leave the table.  The difference between ride height and where the tires lift is your droop.  Measure at the rear of the main chassis.  Just think of the pod like a suspension arm flopping down.

If I understand you correctly, you mean the rear arms near the back of the servo, right.

 You want me to put spacers under the ball studs to angle the rear of the front arm up.
How much?
  Start with 1mm, you may be able to get 1.5 on with the stock screw.  More would probably need a longer screw.  You can also change the ball stud on the front of the arm to a shorter one to get a similar effect, or add even more in combination with the rear spaced up.
Is this kinda like antidive? What I don't understand is how raising the arms here does anything with the pivot ball at the top of the
This is the same as the front end of a 12L with the dynamic caster setup.  The upper arm moves forward on compression, reducing caster. There is a slight caster increase at ride height, but it's not much.  You're just pulling the upper arm back a little, but the big effect is the caster change in compression.  You'll see it if you work the suspension.

What about front caster?  Not adjustable?  Spacer under front screw like F103?

You could do the spacer,but you might not have as big of an effect due to the geometry of the arms

What about the steering blocks?  Right now the car has the 3.5 mm offsets on it.  We tried both styles on the F103 and found that the car was 2-3 tenths faster with the offsets.

I'm surprised to hear you were faster with offset blocks.  They kill a lot of steering for me.  L--- might drive different than me (i.e. better).  You may want to try the regular blocks, just because I feel they steer more off center/off power. 


Speaking of F103,  do you use the pivot ball suspension or the O ring?  I'm sure you tried both... advantages/disadvantages?  What would you use for rubber tire?  I just bought the pivot ball suspension, but before I tried it, I thought I'd ask you for your opinion.  Any special tricks/tweaks you do to them to make them work better?

I did a lot of work with the pivot suspension.  Having raced 1/12 quite a bit, I liked that you could add tweak screws and tweak the car like a 1/12.  It also was a lot of trouble for nothing, as an o ring setup was the exact same speed without all the tweak headaches.  I have watched a lot of guys out here run the pivot setup with no tweak screws, and it seems good outdoors, and at least ok on carpet. I feel that the o ring is a little better for foam, at least, as you can adjust the screw tension, as well as use different orings and tilt the t bar as well.

What I had been doing was using the stock t bar, with an .5mm aluminum shim on the forward screw.  The rear screw was either a black oring (lower traction) or an .060" nylon spacer for higher traction.  I would start with the o ring for rubber, but you may want to add a .5mm or .030" shim as well.  I was trying to achieve a slight angle to the back of the car, sort of like anti squat.  This will make the car not get on the nose so hard off power, making it easier to drive.  You may also want to look into a soft t bar as well, or even an o ring on both screws depending on traction.

The tension on the t bar affects how much it can twist, and I feel this affects  the rotation of the car.  More twist = more rotation, but there are diminishing returns here.  For a good example, the 104 with the middle screw out rotates a lot more since the t bar can twist much more freely.  Too much and it will park in the sweepers or hang a wheel in the air.  It may not be as big of as hazard with rubbers though.

Right know, with Ride A front tires and the Tamiya A's the car is hooked up pretty well.  Rear tires are "chirping" a bit a on sharp turns.  Can't seem to get the car to rotate through the corners as well as I'd like it to.  Any suggestions on getting the car to roll through the corners better? 

Tried stiffer shock spring, but started with  the silver one that has a ton on coils in it, fairly soft and all the way up to a yellow.  Just lost overall speed with not any real improvement. Tried more tension on the puck set screw, heavier grease, not saucing the rears all of which made the car slower.

Got the stock black O ring in the middle hole with the stock black T plate. The middle T plate screw is medium light on the tightness. Using the 3Racing front suspension with the caster setting at about 5 degrees.  Tried the stock front F103 front end and it again was slower than the link type front.

You may actually be a bit faster with the pivot ball, from what you are saying.  You're sliding the rears to get the chirp.  All the things you tried bound up the rear end more, so the car just wants to slide.  The pivot setup will just cycle side to side as fast as the puck lets it, so the car should rotate better.  Otherwise I would go with o rings on both screws, maybe even red orings to be a bit softer.

I think the link front end probably is the way to go, as it seems to have more traction and you can add camber as well.  I know with foams it had too much steering generally.

You might want to widen the rear a little bit as well.

This was a 15th anniversary car??  If not, and you are running the short fiberglass top deck, it will feel like it has no steering.  What is the chassis setup- graphite? fiberglass?  long or short top deck?  A graphite car can also feel like garbage on a low traction track. 


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